unit 3 + unit 4 Flashcards

Question

neuron structure

Answer 1

- Neuron structure: › Cell body: contains nucleus, controls cell’s functioning, directs metabolism, no role in neural signalling. Holds the organelles (mitochondria, Golgi body, etc) › Dendrites: short extensions of the cytoplasm of the cell body. Increase surface area. Receive nerve messages. High branched and carry messages/nerve impulses into the cell body › Axon: single long extensions of cytoplasm. Carries nerve impulses away from the body of the cell to other cells. Length varies. At its end, axon divides into many small branches which terminates at the axon terminal › Myelin sheath: layer of white fatty material that covers axons. - Nerve fibres with myelin: myelinated fibres - Nerve fibres without myelin: unmyelinated fibres - Outside brain and spinal cord it is formed by Schwann cells (wrap around the axon) - Gaps in myelin sheath called nodes of Ranvier - In brain/spinal cord: made by oligodendrocytes › White matter: myelinated fibre appears white › Grey matter: areas made of cell bodies and unmyelinated fibres

Answer 2

- Function of myelin sheath: 1. Acts as an electrical insulator (stops nerve signal leakage) 2. Protects axon from damage 3. Speeds up movement of nerve impulses along axon

Answer 3

- Outermost coil of Schwann cell forms neurilemma around myelin sheath › Helps in repair of injured fibres - Synapses: › Junction between the branches of adjacent neurons › Neurons don’t physically touch, small gap › Message carried across gap by movement of neurotransmitters › Axon and skeletal muscles cell = neuromuscular junction

Answer 4

• Functional types of neurons: - Sensory: (afferent/receptor) neurons that carry messages from receptors to CNS - Motor: (efferent/effector) neurons that carry message from CNS to effectors - Interneuron: (association/connector/relay) in CNS, link between sensory and motor

Answer 5

• Structural types of neurons: - Multipolar: have one axon and multiple dendrites extending from cell body. › Interneurons and motor neurons - Bipolar: one axon and one dendrite. › Neurons in eye, ear and nose (from receptor cell to other neuron) - Unipolar: only one extension, axon. › Not in humans, insects - Pseudo-unipolar: properties of both unipolar and bipolar. One axon separates into two. One connects to dendrites, while other ends in axon terminal. Cell body lies to one side of main axon. › Sensory neuron

Answer 6

• Nerve fibres: - Axon and dendrites of nerve cells = nerve fibres - Nerve fibres arranged in bundles held together by connective tissue, with multiple bundles joining together to form nerve.

Answer 7

- PNS is composed of › Nerve fibres that carry info to and from the CNS › Group of nerve cell bodies, ganglia, which lie outside brain and spinal cord - Cranial nerves: › 12 pairs (e.g., optic and auditory) that arise from the brain › Most are mixed nerves (both sensory and motor fibres), few carry only one - Spinal nerves: › 31 pairs arise from spinal cord › All mixed nerves - Each nerve is joined to the spinal cord by two roots - Ventral root: axons of motor neurons that have their cell bodies in grey matter of spinal cord - Dorsal root: contains axons of sensory neurons that have their cell bodies in a small swelling on the dorsal root, known as the dorsal root ganglion

Answer 8

• afferent-efferent - Afferent division: sensory division, has fibres that carry impulses into CNS by sensory neurons from receptors › Somatic sensory neurons: bring impulses from skin and muscles › Visceral sensory neurons: bring impulses from the internal organs - Efferent division: motor division, has fibres that carry impulses away from the CNS › Autonomic - Parasympathetic - Sympathetic › Somatic

Answer 9

• autonomic-somatic - Autonomic: carries impulses from CNS to heart muscle, involuntary muscles and glands › Controls body’s internal environment › Usually operates without conscious control › Regulated by groups of neurons in medulla oblongata, hypothalamus and cerebral cortex - Heart rate - Blood pressure - Pupil diameter - Urination and defecation › Nerve fibres of ANS make up part of spinal and cranial nerves. › Impulse travels along 2 neurons from CNS to the effector - First is myelinated and has its cell body in the CNS - Second neuron is unmyelinated and has its cell body in a ganglion, outside CNS › Neurotransmitter is either acetylcholine or noradrenaline › Function: internal adjustment, homeostasis › Usually involuntary control › Two sets of nerves to target organ (parasympathetic and sympathetic) › Effect of target organ: excitation and inhibition - Somatic: takes impulses from CNS to the skeletal muscles › Has one neuron from CNS to effector › Neurotransmitter is acetylcholine › Function: response to external environment › Usually voluntary control › Effect on target organ: always excitation

Answer 10

• sympathetic-parasympathetic - Sympathetic: produce responses that that prepare body for strenuous physical activity (flight/fight) › In threatening situations, sympathetic becomes dominant. Flight/fight response: - Rate and force of heart increase, BP increases as well - Blood vessels dilate in organs involved in strenuous activity (heart, skeletal muscles, liver) - Blood vessels constrict in organ NOT involved in strenuous activity (kidney, stomach, intestines, skin) - Airways in lung dilate, rapid breathing - Blood glucose levels rise, as liver breaks down glycogen - Secretions from sweat glands increase - Adrenal medullae secrete adrenaline and noradrenaline which intensify and prolong above responses - Parasympathetic: produces responses that maintain the body during relatively quiet conditions (rest) › Both maintain stability of body functions - Decreases rate and strength of heart contraction - Constrict bronchioles - Constrict pupil - Constricts muscles of urinary bladder - Increases movement of stomach and intestines - Increase production of glycogen - Increases secretion of saliva - No effect on: sweat, blood vessels, adrenal medulla

Answer 11

• Cranium and vertebrae (bone): - Outermost protective layer is bone - Brain is protected by cranium - Spinal cord runs through vertebral canal (opening in vertebrae) › Bones provide strong, rigid structure that protects CNS

Answer 12

• Meninges: - Inside the bones and covering surface of brain and spinal cord. - 3 layers of connective tissue forming membranes called meninges › Dura mater: (outer) tough and fibrous and provides layer of protection - Sticks closely to bones of skull, but on inside of vertebral canal it isn’t that close fitting › Arachnoid mater: (middle) loose mesh of fibres › Pia mater: (inner) contains many blood vessels and sticks closely to surface of brain and spinal cord.

Answer 13

• Cerebrospinal fluid (CSF): - Occupies space between middle and inner meninges layer - Circulates through cavities in brain and through a canal in centre of spinal cord - Clear watery fluid containing few cells and some glucose, proteins, salts and urea - Functions: › Protection: shock absorber, cushions blows/shocks sustained by CNS › Support: the brain is suspended inside the cranium and floats in the fluid that surrounds it › Transport: CSF formed from blood and circulates around and through CNS before re-entering capillaries. Takes nutrients to cells and carries away wastes.

Answer 14

• Cerebrum: - Biggest part of brain - Outer surfaces thick of grey matter known as cerebral cortex - Below cerebral cortex is white matter. Composed of nerve fibres surrounded by myelin. In CNS bundles of nerve fibres are called tracts (outside called nerves). Tracts in white matter › Tracts that connect various areas of cortex to within same hemisphere › Carry impulses between 2 hemispheres › Connect the cortex to other parts of brain/spinal cord - Deep inside cerebrum is additional grey matter called basal ganglia › Consist of group of nerve cells associated with control of skeletal muscles › Initiate desired movement, and inhibit unwanted movement. - Folded to increase surface area (cortex contains 70% of all neurons CNS) › Round ridges/convolutions (gyri) › Convolutions separated by shallow downfolds (sulci) › Convolutions separated by deep downfolds (fissures) - Deepest fissure: longitudinal fissure, almost separates cerebrum into two hemispheres - Fissures and sulci further divide each hemisphere into 4 lobes - Frontal lobe: thinking, problem solving, emotions, personality, language (left hemisphere), control of movement - Parietal lobe: processing temp, touch, taste, pain and movement - Temporal lobe: processing memories and linking them with senses. Receives auditory information - Occipital lobe: vision - Insula: deep inside the brain. Recognition of different senses and emotions, addiction and psychiatric disorders. - Cortex has three functional areas: › Sensory: interpret impulses from receptors › Motor: control muscular movements › Association: intellectual and emotional processes

Answer 15

• Corpus callosum: - Wide band of nerve fibres that lies underneath the cerebrum at the base of the longitudinal fissure - Nerve fibres cross from one hemisphere to the other: allow the two sides to communicate with each other

Answer 16

• Cerebellum: - Under the rear part of cerebrum. - Second largest - Surface folded into a series of parallel ridges. - Outer part is grey matter, inside is white matter that branches to all parts of cerebellum. - Controls posture, balance and fine coordination of voluntary muscle movement - Receives sensory info from: › Inner ear about posture and balance › Stretch receptors in skeletal muscles for information about length of muscles - Without it movements would be spasmodic, jerky and uncontrolled

Answer 17

``` • Hypothalamus: - Middle of brain - Concerned with homeostasis › Regulation of autonomic nervous system › Thermoregulation › Food and water intake › Emotional responses › Stimulates pituitary gland ```

Answer 18

• Medulla oblongata: - Continuation of spinal cord › Cardiac centre: regulates rate and force of heartbeat › Respiratory centre: control rate and depth of breathing › Vasomotor centre: regulates diameter of blood vessels - Influenced by higher centres in brain, especially hypothalamus

Answer 19

• Spinal cord: - 44 cm long - From foramen magnum to second lumbar vertebra - Space between outer meningeal layer and bone: contains fat, connective tissue and blood vessels › Serves as padding around spinal cord › Allows cord to bend when spine is bent - grey matter is at centre surrounded by white matter › grey matter is ‘H’ shape › in centre of grey matter is central canal which holds CSF - Myelinated fibres: › Ascending tracts: sensory axons that carry impulses towards brain › Descending tracts: motor axons that conduct impulses away from brain - Takes messages between brain and peripheral nervous system

Answer 20

• Receptors: structure that detects change in internal and external environment

Answer 21

• Thermoreceptors: in skin and hypothalamus - Respond to heat and cold - Skin thermoreceptors: inform the brain (hypothalamus and cerebrum) of changes in temperature outside the body. › Peripheral thermoreceptors in skin sensitive to heat or cold (not both) - Thermoreceptors in the hypothalamus: monitors core temperature, detect temperature of the blood that is flowing through the brain › Using info from skin AND hypothalamus receptors, hypothalamus can regulate body temperature - Krause end bulbs: detect cold (in skin) › Only in specialised regions › Defined by capsules - Ruffini endings: detect warmth (in skin) › Can act as thermoreceptors › Deep layers of skin › Detect warmth

Answer 22

• Osmoreceptors: hypothalamus - Sensitive to changes in osmotic pressure › Osmotic pressure: concentration of substances dissolved in water of blood plasma. Higher the concentration -> higher osmotic pressure - Stimulate hypothalamus so that body’s water content is maintained

Answer 23

• Chemoreceptors: - Stimulated by particular chemicals. Nose (sensitive to odours) and mouth (sensitive to taste), internal chemoreceptors (sensitive to composition of bodily fluid) e.g. Certain blood vessels (sensitive to blood pH and concentration of O2 and CO2)-> regulate heart rate and breathing

Answer 24

• Touch/Mechanoreceptors: mainly in skin - Some are close to skin surface and sensitive to light touch (lips, fingertips, eyelids, external genital organs) - Hair receptor: nerve endings on base of hair follicle › Respond to light touch that bends the hair › Touch receptors close to skin and hair receptors: adapt rapidly, after a while no longer aware of the touch - Some receptors are deeper in the skin and are sensitive to pressure and vibrations - Merkel’s Disk: slow adapting, unencapsulated nerve endings that respond to light touch. Present in upper layers of the skin - Ruffini endings: slow adapting, encapsulated receptors that respond to skin stretch and are present in both smooth and hairy skin - Pacinian corpuscles: rapidly adapting, deep receptors that respond to deep pressure and high frequency vibration - Meissner’s corpuscle: rapidly adapting, encapsulated neurons that respond to low frequency vibrations and fine touch. Located in glabrous (hairless) skin on fingertips and eyelids

Answer 25

• Nociceptors: concentrated in skin and mucous membranes. Most organs, not in brain - Stimulated by damage to the tissues by poor blood flow to tissue; or by excessive stimulation form stimuli (heat or chemicals) - Pain warns us that damage to tissues is occurring so we can take evasive action/ seek medical action - Pain receptors: adapt little or not at all, so pain continues as long as stimulus is present › Failure to adapt keeps person aware

Answer 26

• Reflexes: rapid automatic response to a stimulus. Properties: - Stimulus required to trigger reflex - Involuntary: without conscious thought - Rapid: only small number of neurons involved - Stereotyped: occurs same way each type it happens • Most are coordinated by spinal cord. Spinal reflex: reflex carried out by spinal cord without involvement of brain - Impulses may be sent to brain, so we become aware of what is happening, awareness occurs after response has been initiated

Answer 27

• Reflex arc: pathway a nerve impulse follows in travelling from a receptor to an effector - Receptor reacts to change in the internal and external environment by initiating nerve impulse in sensory neuron - Sensory neuron carries impulse from receptor to spinal cord or brain - There is at least one synapse: nerve impulse may be passed directly to motor neuron, or there may be one or more interneurons to direct impulse to correct motor neuron - Motor neuron carries nerve impulse to an effector - Effector receives impulse, and carries out appropriate response

Answer 28

• Learnt reflexes: - Innate reflexes: acquired genetically, present at birth. Suckling, chewing, etc. - Acquired reflexes: response learnt through practise. Jamming car brakes, catching a ball, etc.

Answer 29

• Nerve impulses: electrochemical change that travels along a nerve fibre. Involves: - Change in electrical voltage - Brought about by changes in chemicals (concentration of ions around neuron cell membrane)

Answer 30

• Electrical charge and potential difference: - Like charges repel - Opposite charges attract - When positive and negative charges come together energy is released. If they are separated, they have potential to come together and release energy - Potential difference: difference in electrical charge between two locations

Answer 31

• Potential difference across a cell membrane: - Extracellular fluid: contains high concentration of NaCl. Positive Na ions and negative Cl ions - Intracellular fluid: low concentration of Na ions and Cl ions. Mainly positive K ions, and negative ions come from a variety of organic substances made by the cell - Differences in concentration of ions means there is a potential difference inside and outside cell membrane, membrane potential. - Resting membrane potential = -70mV › Potential of inside of membrane is 70mV less than that of outside

Answer 32

• Sodium- potassium pump: - Ions are unable to diffuse through phospholipid bilayer › Move through protein channels - Leakage channels: channels that are open all the time - Voltage-gated channels: only open when the nerve is stimulated - Resting membrane potential is mostly due to Na and K ions. Extracellular more positively charged › [Na ion] is 10x higher outside than inside. Limited number of sodium leakage channels, so this limits facilitated diffusion of Na ions › [K ion] is 30x higher inside. Cell is very permeable to K ions due to lots of potassium leakage channels. More K ions able to diffuse than Na ions. › [Cl ion] is higher outside than inside. Cell is highly permeable to Cl ions, allowing diffusion through protein channels › Concentration of large, negatively charged organic ions is higher inside the neuron than outside. Cell membrane impermeable to these ions, so they stay inside - Sodium-potassium pump is a carrier protein that lets Na and K move across membrane › Uses ATP because it goes against concentration gradient 1. The S-P pump binds 3 Na ions and an ATP molecule 2. Splitting of ATP provides energy to change the shape of the channel. Na ions driven through the channel 3. Na ions released to outside of new membrane, and the new shape allows 2 K ions to bind 4. Release of phosphate allows the channel to revert to its original form, releasing the K ions on the inside of the membrane › Net reduction of positive ions inside the cell › Negative resting membrane potential, membrane is polarised

Answer 33

• Action potential: opening and closing of voltage-gated channels, which cause rapid depolarisation and repolarisation of the membrane. Lasts a millisecond. Action potential triggers action potential in adjacent membrane - 1. Depolarisation: sudden increase in membrane potential › Level of stimulation exceeds around 15mV › When a neuron is stimulated, some sodium channels are opened. More Na ions move into the cell, makes intracellular fluid less negative, increasing potential difference. › If stimulus increased potential to -55mV, voltage-gated sodium channels open, and Na ions move into cells independently of stimulus - Size of response is not related to strength of stimulus - All or none response: nerve impulse is transmitted at full strength or not at all › Inside more positive than outside, membrane is depolarised. Polarity reaches 40mV approximately - 2. Repolarisation: › Sodium channels close, stops influx of Na ions › Voltage-gated potassium channels open, increasing flow of K out of cell › Inside is more negative and decreases membrane potential- membrane is repolarised › Potassium channels open for longer than needed, so membrane potential drops lower than resting membrane potential, membrane is hyperpolarised - 3. Refractory period: › Once sodium channels have opened, they quickly become inactivated: so, they are unresponsive to stimulus › Brief period after being stimulated, membrane will not undergo another action potential. › Lasts from -55mV to -70mV (returns to resting membrane potential) › Period of time before another action potential can occur at same location

Answer 34

• Conduction along unmyelinated fibres: - Depolarisation of one area of membrane causes a movement of Na ions in adjacent areas › Process repeats itself: action potential moves along the membrane away from point of stimulation › Nerve impulse prevented from going backwards by refractory period

Answer 35

• Transmission along myelinated fibres: - Myelin sheath insulates the nerve fibre from extracellular fluid. Ions cannot flow between the inside and outside and action potential cannot form - Doesn’t occur at nodes of Ranvier, no myelin there › Action potential jumps from one node to the next › Saltatory conduction: allows faster transmission in myelinated fibres › (140m/s vs 2m/s)

Answer 36

• Size of nerve impulse: - Nerve impulse that travels along a fibres is always the same size, regardless of stimulus size they produce same action potential (provided it exceeds threshold) › Nerve impulse doesn’t become weaker with distance - Strong impulse: causes depolarisation of more nerve fibres, and produces more nerve impulses in a given time

Answer 37

• Transmission across a synapse: - 1. When the nerve impulse reaches the axon terminal, it activated voltage-gated calcium ion channels - 2. Since there is a higher [Ca ion] in extracellular fluid, they flow into the cell at the pre-synaptic axon terminal - 3. This causes synaptic vessels to fuse with the membrane, releasing neurotransmitters by exocytosis - 4. Neurotransmitters diffuse across gap and attach to receptors on the membrane of the next neuron - 5. This stimulates ligand-gated protein channel to open, which allows influx of Na ions and initiates an action potential in the post synaptic membrane › Neurotransmitters are reabsorbed by presynaptic membrane, by being degraded by enzymes or diffusion › One direction : Axon to dendrites or axon to cell body

Answer 38

• Effect of chemicals on transmission of nerve impulses: - Stimulants: (caffeine) stimulate transmission at synapse - Depressant: (alcohol) depress transmission at synapse - Venom affects neuromuscular junction › Nerve agents contain organophosphates, which cause build-up of acetylcholine at neuromuscular junction. All muscles then try to contract-> prevents breathing

Answer 39

• speed of action: - nervous responses are more rapid than hormonal ones, because nerve impulses travel rapidly along nerve fibres, while hormones are transported in blood stream - nervous system responds to stimulus in milliseconds, while hormone release may take several seconds or days

Answer 40

• duration of action: - when stimulus ceases: nervous system stops generating nerve impulse and the responses ceases almost immediately. So nerve impulses bring about an immediate response, which only lasts a short time - hormones are slower acting, and responses can last a considerable time (even years). May continue long after stimulus has stopped

Answer 41

• nature and transmission of the message: - nervous messages are an electrochemical change (electrical impulses and neurotransmitters) that travels along membrane of neuron - endocrine messages are chemical (hormones) that are usually transported by blood › some substances function as both hormones and neurotransmitters (noradrenaline, ADH, dopamine) › some neurotransmitters and hormones have the same effect on the same target cells. Noradrenaline and glucagon both act on liver cells to breakdown glycogen › some hormones (oxytocin and adrenaline) are secreted by neurons into extracellular fluid

Answer 42

• specificity of message: - nerve impulses travel along fibre to specific part of the body and often influence just one effector. Usually local and specific. › Effects muscles, glands and other neurons - hormones travel to all parts of the body, are carried by blood and often affect a number of different organs. May be very general and widespread › can affect all body cells

Answer 43

process of keeping the environment inside fairly constant despite fluctuations in external environment. - Body needs optimal temp, pH, oxygen, glucose, etc. - Makes us independent of external environment. - There is a dynamic equilibrium, input and output need to be balanced - Nervous and endocrine system are the main sensory and controlling body systems › Operate through feedback systems

Answer 44

responds to stimulus, response alters original stimulus - Stimulus: change in environment that causes system to operate - Receptor: detects change - Modulator: control centre responsible for processing information from receptor and for sending information to effector - Effector: carries out a response counteracting/enhancing the effect of the stimulus - Response: original stimulus has been changed. Feedback achieved - Homeostatic mechanisms controlled by nervous and endocrine systems. Both detect changes, endocrine is slower.

Answer 45

response reduces or eliminates the stimulus that caused feedback loop. - AKA steady state system: return body back to steady state - Dynamic equilibrium = fluctuation - Point around which it fluctuates = set point - Tolerance limits = upper and lower limits around which levels fluctuate › If rise/fall exceeds tolerance limits, dysfunctions occur

Answer 46

no role in homeostasis. Response to stimulus reinforces and intensifies the stimulus results in a greater response - Childbirth: › Labour initiated by secretion of oxytocin › Oxytocin creates uterine contractions; contractions push baby’s head against cervix › Stimulation of cervix sends impulses to brain which secretes more oxytocin. › Increased oxytocin increasingly intensifies contractions › Once baby delivered and cervix no longer stretched, positive feedback stops - Blood clotting is another example - Can be dangerous if you have a high fever: › small rise in temp is good when fighting fever, but when body temp exceeds 42ºC, positive feedback loop occurs › raised body temp increases metabolic rate which makes more heat, so temp increases.

Answer 47

* Set point is 36.8ºC: optimal temp for cellular activities * Heat gain = heat loss * Heat gain: heat from metabolism, heat from surroundings by conduction/radiation * Heat loss: radiation, convection, conduction to surroundings, evaporation of water from skin and lungs, warm air breathed out, warm urine and faeces excreted

Answer 48

- Food we eat contains energy in chemical bonds › Energy released when oxidised › 60% of energy used for heat production - Metabolic rate: rate at which energy is released by breakdown of food - Factors effecting metabolic rate › Exercise › Body temp › Stress: stimulation of sympathetic nerves releases noradrenaline from nerve endings: increasing metabolic activity of cells

Answer 49

- Peripheral thermoreceptors: detect temp change in external environment, and send info to hypothalamus (skin and mucous membrane) - Central thermoreceptors: detect temp of internal environment (hypothalamus, spinal cord, abdominal organs) - Cold receptors: stimulated by temp lower than normal - Heat receptors: detect temp higher than normal

Answer 50

- Large SA and location of skin makes it essential. Heat can be lost by: › Conduction: transfer by direct contact › Convection: transfer by movement of liquid/gas › Radiation: transfer by infrared radiation › Evaporation: liquid forming gas, absorbs heat energy

Answer 51

- Blood vessels in dermis carry heat to skin from body core › Diameter controlled by autonomic nerves - Vasodilation: moves blood to skin and rate of heat loss increases - Vasoconstriction: less blood to skin, heat loss rate decreases

Answer 52

- When heat must be lost and arterioles are already dilated, sweating occurs - Sweating: active secretion of fluid by sweat glands and periodic contractions of cells surrounding sweat glands to pump sweat to skin surface - Stimulated by sympathetic nerves - Sweat: water and dissolved substances (salt, urea, lactic acid, potassium ions) - Evaporation of sweat has a cooling effect › Heat removed from skin as sweat vaporises cooling skin which cools blood in skin › Also, water evaporated by lungs and respiratory passages

Answer 53

- Shivering due to increased skeletal muscle tone producing rhythmic muscle tremors › Energy produced by muscles is released as heat

Answer 54

- Cold receptors send messages to hypothalamus - Hypothalamus sends impulses to initiate warming processes › Stimulates sympathetic nerves that cause skin arterioles to constrict. Cooler skin, less heat lost from body surfaces › Stimulates adrenal medulla by sympathetic nerves to secrete adrenaline and noradrenaline in blood: increases cellular metabolism › Stimulates parts of brain that cause shivering. Under primal control of hypothalamus, conscious input from cerebral cortex can suppress urge to shiver › Anterior lobe secretes TSH. Increased metabolic rate which increase bod temp. slower and long lasting. › Reduce SA of body, remove layers, move closer to heat source (consciously aware of cold conditions) › Piloerection

Answer 55

- Vasodilation: greater heat loss by radiation and convection - Sweating: cooling effect in dry environment › Humid: sweat cant evaporate so it doesn’t absorb heat from body › Less thyroxine: decrease in metabolic rate › Removing layers, reducing physical activity

Answer 56

- Hypothalamus is modulator › Receives impulses from peripheral thermoreceptors through negative feedback loop, including autonomic nervous system, thermoregulation mechanisms are maintained

Answer 57

- Heat stroke: body temp rises and regulating mechanisms cease. Fatal if brain cells effected (42-45ºC) - Heat exhaustion: results from extreme sweating and vasodilation to lose heat › Loss of water reduces volume of blood plasma › vasodilation reduces resistance to blood flow › low BP and output of blood from heart decreases › body temp is almost normal - Hypothermia: temp falls below 33ºC › Metabolic rate is so low that heat production is unable to replace heat lost and temp continues to fall › Death below 32ºC

Answer 58

• Sugar in blood in form of glucose • Blood sugar = amount of glucose in blood - Glucose is a source of energy • Source of glucose is food: - Carbohydrates broken down to glucose and then absorbed by blood through walls of small intestine - After a meal BGL rise sharply - Homeostatic mechanisms reduce BGL by storing excess glucose ready for when BGL drops

Answer 59

- Glucose is stored as glycogen › Glycogen: molecule made of long chains of glucose molecules - Body can store 500g of glycogen (100g in liver, remainder in skeletal muscles) - Excess glucose to glycogen - Not enough glucose, glycogen to glucose

Answer 60

- Largest gland - Converts glucose to glycogen or glycogen to glucose - Liver’s blood supply comes mostly through the hepatic portal vein. › Brings blood from stomach, spleen, pancreas, small and large intestine › Liver has first chance to absorb nutrients from digested food - Glucose absorbed by villi in small intestine › Hepatic portal vein brings glucose to liver - Glucose can: › Removed from blood by liver to provide energy for liver functioning › Removed by liver/muscles and converted to glycogen for storing › Continue to circulate in blood, for other body cells to use as a source of energy › Be converted into fat for long term storage if it is in excess of that required to maintain both normal blood sugar and tissue glycogen levels - Glycogenesis: when glucose molecules are chemically joined in long chains to make glycogen (stimulated by insulin) › Glycogen stored in liver is available for conversion to maintain BGL and provide energy for liver functioning › Glycogen in muscles provide glucose for muscle activity - Glycogenolysis: when glycogen is broken down into glucose › Stimulate by glucagon › Glycogen is short term energy supply (6 hours). If more energy is required, body uses energy reserves stored in fat - Gluconeogenesis: conversion of fats or proteins into glucose

Answer 61

- Clusters of hormone secreting cells (islets of Langerhans) - Insulin causes a decrease in BGL: › Accelerates transport of glucose from blood into body cells (especially skeletal muscle) › Accelerates conversion of glucose into glycogen in liver and skeletal muscles (glycogenesis) › Stimulation of glucose to protein (protein synthesis) › Stimulating conversion of glucose into fats in adipose tissue or fats storage tissue (lipogenesis) - BGL regulated by negative feedback loop - As BGL rises, chemoreceptors in beta cells stimulate those cells to secret insulin › As BGL decrease the cells are no longer stimulated and production reduced - Glucagon causes an increase in BGL: › Stimulate glycogenolysis in liver › Stimulates gluconeogenesis: production of sugar molecules from fats and amino acids in liver. Involves lipolysis › Have a mild stimulating effect on protein breakdown - When BGL rises, chemoreceptors in alpha cells stimulate secretion of glucagon. › As BGL rises, cells no longer stimulated, and production reduced

Answer 62

- Glucocorticoids secreted by adrenal cortex - Secretion of adrenaline/noradrenaline by adrenal medulla - Adrenal cortex: › Stimulated to secrete hormones by ACTH from AL of pituitary gland › Cortisol secreted › Glucocorticoids regulate carbohydrate metabolism by ensuring enough energy is provided to cells › Stimulate conversion of glycogen to glucose in glycogenolysis. › Also increases rate at which AA are removed by cells (mainly muscle) and transported to the liver - Some AA to glucose by liver during gluconeogenesis if glycogen and fat are low › Promote metabolism of fatty acids from adipose tissue, allowing muscle cells to shift from using to glucose to FA for much of their metabolic energy - Adrenal medulla: › Synthesis of adrenaline and noradrenaline make same effects as sympathetic nervous system › Effect is increase of BGL: adrenaline elevates BGL through glycogenolysis and counteracts effects of insulin - Stimulates production of lactic acid from glycogen in muscle cells, can be used by liver to manufacture glucose

Answer 63

- 4-6 millimoles/L | - 5mmol/L = 90mg/100ml

Answer 64

• Water makes up large portion of human body - 75% infants - 50% females - 60% males - 45% old age • Fluid inside cell: intracellular fluid/cytosol • Fluid outside cell: extracellular: - Blood plasma located within blood vessels (intravascular) - Fluid between cells (interstitial, intercellular, tissue) - Fluid in specific body regions (transcellular) › Brain, spinal cord, eyes, joints, surrounding heart • Different body fluids aren’t isolated from one another. Continuous exchange of materials between them • If imbalance in osmotic concentration (conc of solutes) does occur, osmosis normally restores balance - Osmotic pressure: tendency of a solution to take in water › Greater difference in osmotic conc, the greater the osmotic pressure › Osmosis tends to occur

Answer 65

``` - Fluid gain = fluid loss › Keeps composition of body fluid constant - Water intake: › Food › Metabolic water (by-product) › Drink - Water loss: › Lungs › Skin › Kidneys (urine) › Alimentary canal (faeces) ```

Answer 66

- Removal of waste products of metabolism from the body › Toxic, so harmful if it accumulates - Lungs excrete water (vapour) and carbon dioxide - Sweat glands: secret water containing by-products of metabolism - Alimentary canal: passes out bile pigments that entered small intestine with bile › Bile pigments are breakdown products of Hgb from RBC › Bulk of faeces is undigested food (not excretory producst as it isn’t produced by cells) - Kidneys: principle excretory organ › Maintain constant conc of materials in body fluids › Maintain waste in urea

Answer 67

- Only place where water loss can be regulated for osmoregulation › Sweat glands regulated by thermoregulation - Regulated to achieve a constant conc of dissolved substances in body fluids - Reddish brown, abdomen, wither side of vertebral column, 11cm lon, due to presence of liver: right is usually lower - Embedded in and held in position by a mass of fatty tissue - Ureter leaves each kidney, to bladder, to urethra - Each kidney has ~1.2 million nephrons › Nephrons: functional unit, carry out role in excretion and water regulation › 1. Blood enters glomerulus under high pressure › 2. Filtration: high BP forces water and small dissolved molecules out of blood and into capsule. Large molecules stay in blood › 3. Filtrate collected by glomerular capsule › 4. Reabsorption: filtrate passes PCT, LOH, DCT, CD. Water and other useful substances reabsorbed into peritubular capillaries › 5. Secretion: some materials that need to be removed from body are secreted into kidney tubule from peritubular capillaries › 6. Urine: water and dissolved substances make up urine. Carried by collecting ducts to ureter to bladder

Answer 68

- As water is lost, plasma becomes more concentrated and has higher osmotic pressure. › Water moves from interstitial fluid to plasm by osmosis › Interstitial fluid more concentrated and water diffuses out of cells › cells start to shrink from dehydration - osmoreceptors in hypothalamus detect increase in osmotic pressure

Answer 69

- Dehydrated = urine is less volume and concentrated - Reabsorption of water occurring at PCT and LOH is osmosis - Reabsorption at DCT and CD is active reabsorption controlled by ADH - When ADH conc is high tubules are very permeable to water › Water able to leave tubule and re-enter peritubular capillaries › Outward flow of water from filtrate reduces volume and increases conc of remaining materials - When ADH conc is lower: tubules not very permeable › Little water reabsorbed into plasma › Filtrate remains fairly dilute and volume not reduced

Answer 70

- Aldosterone helps osmoregulation - Salt-retaining hormone - Secreted by adrenal cortex in response to: › Low sodium in blood › Low blood volume and pressure › High potassium in blood - Acts on DCT and CD to increase sodium reabsorbed and amount of potassium secreted in urine - Uses active transport using a sodium potassium pump › Every 3 sodium, 2 potassium secreted › Net movement into blood and subsequent transport of water into blood via osmosis › So aldosterone has a role in osmoregulation

Answer 71

- Osmoreceptors able to stimulate thirst centre in hypothalamus promoting person to drink water › Fluid absorbed across wall of alimentary canal into blood decreasing osmotic pressure › Excess fluid in interstitial fluid is collected by lymph system

Answer 72

- Body fluids become diluted and cells take in extra water by osmosis - Person loses water and salt through sweating and replaces loss with water - Light-headedness, headache, vomiting

Answer 73

- Water loss exceeds intake | - Severe thirst, low BP, dizziness, headache

Answer 74

* Cells need a continuous supply of oxygen and removal of carbon dioxide * Respiratory system takes in oxygen and removes carbon dioxide, respiratory system transports them

Answer 75

- Muscles that cause air to move in and out are: › Diaphragm: separates thorax from abdomen › Intercostal muscles: muscles between ribs - Skeletal muscles require stimulation from nerve impulses to contract - Phrenic nerve: stimulates diaphragm - Intercostal nerve: stimulates intercostal muscle › Spinal nerves have their origin in the spinal cord at the level of the neck and thorax - Nerve impulses controlled by respiratory centre in the medulla oblongata. 2 regions: › Controls expiration › Controls inspiration › To coordinate breathing, messages need to pass between neurons of these regions

Answer 76

- Conc of CO2, O2 affect breathing rate and depth - Conc of CO2 in blood plasma affects H+ conc - These 3 factors affect breathing

Answer 77

- Peripheral chemoreceptors: groups of cells within walls of aorta and carotid arteries › Sensitive to changes of the 3 factors › Carotid and aortic bodies - Central chemoreceptors: medulla oblongata sensitive to changes in CO2 and H+ conc in cerebrospinal fluid › When stimulated send impulse to area of respiratory centre that regulates breathing

Answer 78

- As O2 is consumed by cells, its levels decrease in the blood › If O2 drops below normal while other factors are constant, breathing increases - Conc has to fall to very low levels before it has a major stimulatory effect › Under normal circumstances, O2 plays a little roles regulation of breathing - Large decrease in O2 stimulates peripheral chemoreceptors and nerve impulses are sent to respiratory centre › Stimulates transmission of messages to diaphragm and intercostal muscles so breathing rate and depth increases

Answer 79

- Small increase in CO2 conc is enough to cause an increase in breathing rate and depth - Increase in CO2 conc increases H+ conc › Increase in both stimulates central and peripheral to transmit impulses to respiratory centre to increase breathing rate and depth - Chemoreceptor more sensitive to change in CO2 conc are the ones in medulla oblongata › Responsible for 70-80% of response form high CO2 conc › Takes several minutes - Immediate increase in breathing rate that follows an increase in CO2 produced by stimulation of aortic and carotid bodies

Answer 80

- As H+ conc increases, pH decreases - Decrease in pH stimulates peripheral chemoreceptors to transmit impulses to respiratory centre › Increase breathing rate and depth

Answer 81

• Voluntary control of breathing: - Voluntary control comes via connection from cerebral cortex to descending tracts in spinal cord › Bypasses respiratory centre - Protective device: enables us to prevent irritating gases and water from entering lungs • Holding our breath: - Cant stop breathing forever - Build of CO2 in plasma stimulates the inspiratory centre to send impulses to inspiratory muscles › Forced to breathe

Answer 82

• Hyperventilation: - Rapid deep breathing › Provides more O2 and removes more CO2 than needed › Voluntarily or stimulated by stress › Usually corrects itself. Reduction in CO2 means chemoreceptors aren’t being stimulated, reduces breathing rate and depth until normal • Exercise and breathing: - More O2 required and more CO2 produced - Respiratory centre increases breathing rate and depth - Influenced by 3 factors (O2 to a lesser extent)

Answer 83

• Pathogens: disease causing organism - Disease spread from one person to another= communicable, infectious, transmissible - most common: bacteria, viruses, some fungi, animal parasites

Answer 84

• Bacteria: - Prokaryote, unicellular organisms with simple internal structure - Lack distinct nucleus/specialised organelles (no membrane bound organelles) - Lack a nucleus. DNA either floats freely in cytoplasm or in form of circular plasmids - Majority non-pathogenic - Bacilli: rod shaped with flagella - Cocci: spherical cells › Pairs: diplococci › Clusters: staphylococci › Chains: streptococci - Spirilla: twisted cells - Vibrio: curved rods, comma shaped - Seen with light microscope (diameter= 0.5-2. Length= 1-10) › To identify: first grown on agar plate/growth medium in specific conditions. Then stained and viewed. - Reproduce with binary fission

Answer 85

• Viruses: - 20-750 › Seen with electron microscope › Contain genetic info as either DNA or RNA molecule. Molecule surrounded by coat of protein - Some viruses have external lipid envelope - Not living things: can’t reproduce by themselves › Infect living cell and its DNA/RNA induces the cell to make more virus particles › New virus particles are able to leave host cell and infect others › Host cell damaged/changed/die › *Symptoms shown relate to tissue virus invades - Bacteriophages: viruses that infects bacteria. Causes death - Virus attached to outside of host cell and nucleic acid enters the cell. New viral genes made by host cell. 100s of virus particles

Answer 86

Transmission of pathogens occurs by various mechanisms, including through: Communicable: spread by transmission of pathogenic organism from one person to another. Either contagious or vectors (intermediate hosts of pathogens). • direct and indirect contact: - contact: spreading with physical touch (direct and indirect e.g. skin infections, STIs • transfer of body fluids: - blood/body fluid contact with mucous membrane or bloodstream of uninfected person. Pathogen may enter e.g. HIV, hepatitis B+C • disease-specific vectors: - transfer of pathogens by other animals e.g. malaria from mosquitos • contaminated food and water: - contaminated with pathogen leads to disease e.g. salmonella • droplets: - when tiny droplets of moisture with pathogens are emitted when breathing, talking, sneezing/coughing. Droplets breathed in or settle on food or utensils e.g. COVID 19, Ebola, influenza • airborne transmission: - when moisture in exhaled droplets evaporates, viruses can remain viable and cause infection when inhaled - remain viable for greater distance than those transmitted by droplets as particles are lighter e.g. Measles

Answer 87

The body’s external defence mechanisms against pathogens include features of the: Non-specific defences: work against all pathogens, first line of defence • digestive tract: stomach juices are strongly acidic. The acid kills many of bacteria taken with food are those contained in mucus swallowed • urogenital tract: - vagina also has acidic secretions that reduce the growth of microorganisms - urine and the sweat on the skin are also slightly acidic - Urine flowing through urethra has a cleansing action, this prevents bacterial growth and helps stop bacteria reaching bladder and kidneys • respiratory system: trachea and bronchi mucus layers trap microorganisms • the ear: cerumen protects the outer ear against infection by some bacteria, slightly acidic and contains lysozyme • the eye: lysozyme is an enzyme that kills bacteria. eyes are protected by flushing action of tears which in contain this enzyme. lysozyme also in saliva, sweat, secretions of the nose and tissue fluid - Tears, sweat and saliva are also involved in flushing and cleansing • skin: - sweat on the skin are also slightly acidic - Impervious barrier covering the outside of the body. good at stopping entry of microorganisms - bacteria on skin make it difficult for pathogens to become established - sebum produced by oil glands contain substances that kill some pathogenic bacteria - sweat secreted on the skin contains salts and fatty acids that prevent the growth of many microorganisms • mucous: mucous membranes line body cavities that open to the exterior - secrete mucus which traps particles for inhibiting entry of microorganisms - digestive, urinary, reproductive • hairs: found in nasal cavity, and in the ears - hairs and layer of mucus trap up to 90% of particles inhaled and breathing • cilia: tiny hairlike projections from cells that are capable of a beating motion. beating of cilia move mucus, containing trapped particles in microorganisms towards the throat or it may be coughed up or swallowed

Answer 88

• protective reflexes: - Sneezing: irritation of walls of nasal cavity. The irritation may be caused by fumes or dust particles, which carry microorganisms. › forceful expulsion of air from the lungs carries mucus foreign particles and irritating gases out through the nose and mouth - Coughing: irritation in lower respiratory tract (bronchi and bronchioles). air is forced from the lung to try and remove the irritant. Air drives irritant up trachea towards the throat and mouth - Vomiting: psychological stimuli, excessive stretching of stomach, and bacterial toxins can induce vomiting. contraction of muscles of abdomen and diaphragm expels stomach contents - Diarrhoea: irritation of intestines by microorganisms can cause diarrhoea will stop irritation causes increased contractions of muscle of the walls of the intestines, so that irritant is removed as quickly as possible, water not fully absorbed

Answer 89

• Phagocytosis: - Phagocytes: specialised WBC that engulf or digest microorganisms and cell debris. Eliminates pathogens before infection - 1. Monocytes and Macrophages: monocytes leave bloodstream from tissue. At tissue differentiate and become macrophages. › Macrophages: removing microbes and dying cells through phagocytosis - 2. Neutrophils: granulated leucocyte, most abundant › First cells to move into tissue and use phagocytosis to destroy pathogen › Short life span. Dead neutrophils make up large portion of pus - 3. Dendritic cells: have projections from cytoplasm. › Beyond phagocytosis: detect, engulf and process foreign particles - Use this info to assist with specific immunity

Answer 90

• Inflammation: response to tissue damage. - Purpose: › Reduce spread of pathogens and destroy them and prevent entry of more pathogens › Remove damaged tissue and cell debris › Begin repair of damaged tissue - Signs of inflammation: redness, pain, heat and swelling - Complement proteins made by liver cells and macrophages - 1. Mechanical damage or local chemical damage causes mast cells (specialised WBC) to be activated by complement proteins. Release histamine and heparin into tissue fluid - 2. Histamine increase blood flow to area by vasodilation, making capillary walls more permeable. More fluid into tissue from capillary. Increased blood flow =heat and redness, escape of blood fluid = swelling - 3. Heparin prevents clotting in immediate area of injury. Clot of fluid forms around the damaged area, slows spread of pathogen into healthy tissues - 4. Complement system proteins and other chemicals from mast cell attract phagocytes, particularly neutrophils, which consume microorganisms and debris - 5. Abnormal conditions stimulate pain receptors - 6. Phagocytes begin to die. Dead phagocytes and tissue fluid make pus - 7. New cells made by mitosis and tissue repair begins

Answer 91

• Fever: setting of higher set point to inhibit growth of bacteria and speeds up rate of chemical reactions (help make body repair quicker) - Pyrogens released by WBC during inflammation and act of hypothalamus. - Body’s thermostat becomes set at abnormally high level - Body feels cold, hypothalamus initiates warming processes - Fever breaks = crisis point, body’s thermostat back to normal and person feels hot - Fever also inhibits viral replication by allowing interferons to operate quicker

Answer 92

• Vaccines: - Immunisation: programming immune system so that body can respond rapidly to infecting microorganisms. (Developing immunity) - Vaccination: introduction of antigens to acquire artificial immunity without suffering illness › Vaccine: antigen preparation used in artificial immunisation - Live attenuated: reduced virulence (reduced ability to make disease symptoms). Person manufactures antibodies. E.g., rubella - Inactivated: dead microorganisms. Shorter lasting immunity than live attenuated. E.g., whooping cough - Toxoid: inactivated toxins that are released by bacteria. E.g., tetanus - Sub-unit: fragment of organism to provoke an immune response. E.g., HPV - *Another approach: changing DNA to make less virulent (recombinant DNA) › Most commonly injected using syringe › Few months after birth: blood still contains’ mother’s antibodies, vaccine’s antigens will be eliminated by mother’s antibodies, before child can mount own immune response. - Also to activate child’s immune system › Second vaccination = booster, stimulates secondary response - Higher longer lasting antibodies and even more memory cells - ~2 months after to allow antibodies in blood to be eliminated - Herd immunity: group immunity that occurs when a high proportion of people in a population are immunised that those who are not immunised are protected › Less chance of disease being transmitted across population

Answer 93

• Factors to consider with Vaccines: - Allergic reactions: usually to medium in which vaccine was cultured (eggs/yeast) - Preservatives: certain chemical used as preservatives; some believe this impacts nervous system but not proven - Ethical (animal): some viruses cultured in chicken embryos or mice brains. Animal abuse? - Ethical (humans): some require human tissue as some viruses doesn’t grow well in other cells. (Rubella: cells from human embryos) - Ethical (informed consent): developing countries where there are low levels of education (not fully aware of risks) - Ethical (animal testing): vaccines tested on live animals - Promoting sexual activity: HPV virus, more sexually active - Availability: not available readily in all areas - Religious beliefs: opposed to vaccines or methods used to produce vaccines - Cost: too expensive - Commercialisation: interest of commercial vaccine production may affect its use

Answer 94

• Antibiotics: drugs used to fight microorganisms (bacteria) - Bactericidal antibiotics: kill bacteria by changing structure of cell wall/disrupting action of essential enzymes - Bacteriostatic antibiotics: stop bacteria from reproducing, disrupts protein synthesis - Broad spectrum vs narrow spectrum - Multiple drug resistance: resistance to some strains of bacteria to most available antibiotics

Answer 95

• Antivirals: drug treatment for viral infections | - Inhibit development of virus

Answer 96

• Immunity: resistance to infection by invading microorganisms. Presence of memory cells allows the body to respond quickly to deal with pathogenic microorganisms before symptoms occur - Natural immunity: occurs without human intervention - Artificial immunity: results from giving people an antibody or antigen

Answer 97

• Passive immunity: when a person receives antibodies produced by someone else - antibodies diffusing across placenta to developing foetus - antibodies passed a baby in breast milk - When a person is injected with antibodies to combat a particular infection - antibodies are given so that immunity is established immediately - short lived, only lasts until the antibodies are broken down and excreted

Answer 98

• Active immunity: results when the body is exposed to a foreign antigen an manufacturers antibodies in response to that antigen - longer lasting due to presence of memory cells - Having the disease (natural) or vaccine (artificial) - secondary exposure, appropriate antibodies can be produced very quickly eliminating antigen before any symptoms

Answer 99

• Specific defences: directed towards a specific pathogen - Specific defences part of immune system. Immune system composed of cells and proteins that protect against pathogens. - B cells and T cells only provide protection against specific pathogens › When they react it is an immune response

Answer 100

• Immune response: homeostatic mechanism - Deals with invasion and restores internal environment to normal - B cells and T cells: WBC called lymphocytes › Produced in bone marrow › T cells mature in thymus › B cells mature in bone marrow › All become part of lymphoid tissue. Most lymphoid tissue in lymph nodes, but also in spleen, thymus and tonsils - Humoral response: production of antibodies by B cells › Circulate and attack antigens - Cell mediated response: T cells form lymphocytes that destroy invading agents

Answer 101

• Antigens: substance capable of producing immune response - Only non-self antigens triggers both immune responses - Large molecules (protein, carbs, lipids, nucleic acids and may include virus particles/microorganisms/toxins)

Answer 102

• Antibodies: ‘Y’ shaped specialised protein made by plasma cells in response to non-self antigens - Belong to immunoglobulins - Antibody combines with antigen to form an antigen-antibody complex (lock and key) › Antigens have specific active sites with particular shape, antibody has complementary shape

Answer 103

• Antigen presenting cells: dendritic cells, macrophages, and undifferentiated B cells - Detect presence of antigen - Engulf pathogen - Digest pathogen, producing small fragments that move to cell surface - Present antigen to lymphocytes

Answer 104

• Humoral response: - Production and release of antibodies into the blood and lymph › provides resistance to pathogens before they can enter body cells - lymphoid tissue contains B cells [lots of types] › each type has a receptor for a particular antigen › so therefore capable of responding to specific antigen - when antigen presenting cell presents an antigen to specific B cells, B cells activated › antigen also presents the helper T cells leading to release of cytokines: small proteins released in response to antigens and act as messengers - cause helper T cells to clone themselves and produce different cytokines which activate B cells - when B cells are activated they enlarge and divide into a group of cells called a clone › most of the clones become plasma cells which secrete the specific antibody capable of attaching to active site of antigen - circulate in blood, lymph, extracellular fluid to reach site of invasion of pathogen › remaining B cells become memory cells - spread to all body tissues to allow the response to occur more rapidly if antigen enters body again - first exposure = primary response › Usually very slow, takes time for B cells to multiply and differentiate into plasma cells and then secrete antibodies › primary response leaves immune system with the memory of particular antigen - Secondary response: › memory cells recognise antigen more quickly › plasma cells formed quickly and antibody levels in blood rise rapidly to a higher level that lasts longer - response is so quick that antigen has little opportunity to exert any noticeable effects on the body and no illness results

Answer 105

• How antibodies work: - Inactivate foreign enzymes or toxins by combining with them or inhibiting their reaction with other cells - bind to surface of viruses and prevent entering other cells - Coat bacteria, easily consumed by phagocytes - Particles (bacteria, viruses, foreign blood cells) to clump together: agglutination - dissolve organisms - react with soluble substances to make them insoluble › more easily consumed by phagocytes

Answer 106

• Cell mediated immunity: - provide resistance to the intracellular phase of bacterial and viral infections › these pathogens specialise in invading an replicating inside their hosts therefore difficult to overcome - fighting whole cells, provide resistance to fungi and parasites and reject foreign tissue transplants. important in fighting cancer cells - T lymphocytes responsible for cellular immunity - occur in same lymphoid tissue as B cells but occupy different area. thousands of types of T cells that are specific › pathogen -> antigen presenting cells present antigen to specific T cells -> become activated or sensitised › sensitised T cell enlarges and divides, gives rise to a clone - some cells of clone remaining tissue as memory cells - T cells that aren't memory cells develop into three types of T cells › 1. killer T cells: migrate to site of infection and deal with invading antigen. attached to invading cells and secrete chemical to destroy antigen, then search for more antigens › 2. helper T cell: bind to antigen on antigen presenting cells, stimulates secretion of cytokines: - attract lymphocytes to infection site which become sensitised and activated (intensify response) - attract macrophages to place of infection - intensify phagocytic activity - promote action of killer T cells › 3. Suppressor T-cells: release substance that inhibit T cell and B cell activity, slowing immune response - when infection dealt with successfully

Answer 107

• Biotechnology: uses cellular process to make useful products

Answer 108

• Nucleotide: consists of phosphate group, Deoxyribose (5 carbon sugar) and nitrogenous base - Order of nitrogenous base in DNA molecule is genetic information that determines cell structure and functioning

Answer 109

• Recombinant DNA technology: - Artificial selection: choosing parents with desired traits or without undesired trait › Selecting which male and female organism breed › Increase chance of certain gene being present in DNA of next generation › Increase or decrease incidence of certain gene › Slow and inefficient: genes passed on by chance and necessary to wait for next generation to mature before knowing the outcome - Genetic engineering: artificial modification of DNA › DNA either added or removed from a cell › DNA produced = recombinant DNA › Organism = GMO › Possible uses - Introducing genes for desired traits using harmless bacteria to make proteins, replacing faulty genes - Introducing DNA from one species to a different species. Produces: Transgenic Organism. AIM: introduce trait that is not normally present - Isolate and amplify DNA segments and insert into bacterial cell (transgenic bacterium) › Introduced gene became part of bacteria’s DNA and passed on • Examples: - Diagnosis and treatment of diseases and genetic disorders - Manufacture large quantities of pure protein (insulin)

Answer 110

• Restriction enzyme: - 1. Gene for desired trait must be identified and isolated - 2. DNA receiving gene must be opened - 3. Gene added and joins its DNA - Recognise certain base sequence, cut at a certain point - Restriction enzymes are examples of endonucleases: enzymes that cut within a DNA molecule by separating two nucleotides › Straight cut: restriction enzyme makes a clean break across 2 strands of DNA producing a blunt end (both strands terminate in a base pair) › Staggered cut: results in fragments with sticky ends (stretch of unpaired nucleotides, they overhang at break in strands) - Sticky ends: able to combine with DNA segments with complementary bases - Useful as it allows a single stranded overhand to be paired with any other DNA segment that corresponds - Recognition sites: palindromic, 4-8 base pairs in length › Same sequence occurs on both strands within recognition site

Answer 111

• DNA ligase: - Enzyme that joins together DNA strands through ligation - Joins phosphate group to sugar molecule of shorter strand › Complementary bases must first join by forming Hydrogen bonds then DNA ligase joins backbone of each strand

Answer 112

• Vectors: - DNA molecule used to carry DNA into a cell - First isolate the desired gene, gene then inserted into vector and clones › 1. Identify desired gene › 2. Use restriction enzyme to cut DNA on either side of gene › 3. Use restriction enzyme to cut DNA of vector › 4. Add desired gene to vector › 5. Use DNA ligase to join 2 sections of DNA - Example: bacterial plasmids or bacteriophage viruses › Plasmids: circular, double stranded units of cytoplasmic DNA. - Can replicate in cell independent of chromosomal DNA - Gene for desired trait integrated into vector and referred to as recombinant DNA - Vector cloned: numerous copies of DNA able to insert into host cells › Host cells then produce foreign protein using instructions in gene in recombinant DNA

Answer 113

• Recombinant DNA vaccines: - 1st vaccine: for HEP B › Introduce the gene from HEP B virus into cowpox virus › HEP B antigen producing gene is isolated and added to a plasmid - Plasmid introduced into a yeast cell › Yeast cell divides, new cell contains the plasmid with the desired gene › Gene allows yeast cells to produce antigen proteins which is collected and purified

Answer 114

• Diabetes mellitus: group of diabetes, abnormally high BGL and glucose excretion in urine - Disrupts homeostasis - Hyperglycaemia: produces insufficient insulin or cells are resistant to insulin

Answer 115

• Type 1 Diabetes: Insulin Dependent - Fault in patient’s immune system causes destruction of beta cells in islets of Langerhans › Therefore, they don’t produce insulin. Most cells respond do treatment is insulin injections - Insulin: › can’t be treated as tablet: digested in alimentary canal › regular injection of insulin › programmable pump that provides continuous supply of insulin under the skin › doesn’t cure, simply ensures that body is able to function › long-term effects: blindness, kidney failure, heart attack, stroke, amputations, nerve damage

Answer 116

• Type 2 Diabetes: Adult-Onset - Produce insulin but cells don’t respond to it - Lifestyle disease: lack of physical activity, being obese, high fat/sugar/salt diet, low fibre diet, high BP, high BC, smoking - Since cells don’t respond to insulin, they do not take glucose from blood. Blood test after fast has abnormally high BGL - Untreated: heart disease, stroke, kidney disease, eye problems, nerve damage, skin and foot problems - Treatment: healthy lifestyle, monitoring BGL, and medication if BGL can’t be controlled by other measures

Answer 117

• Treating diabetes: - Insulin injections: › insulin obtained from cows/pigs -> expensive and limited - extracts must be purified and sometimes patients suffer from allergic reactions or infections from animal derived insulin - Genetically engineered human insulin: › Gene for human insulin inserted into DNA of bacteria. › Bacteria cultured and transgene allowed bacterial cells to produce protein of human insulin - Extracted and treatment for people

Answer 118

• Thyroid disorders: - Thyroxine: stimulate carbohydrate, protein, and fat metabolism › Regulates basal metabolic rate › Maintain body temp › Controlled by secretion of TSH - Caused by problem with thyroid gland or TSH imbalance

Answer 119

• Hyperthyroidism: - Too much thyroxine: most common type = Grave’s disease - Genetic predisposition but not inherited - Enlargement of thyroid gland due to immune system reaction - Symptoms: › Rapid heartbeat › Weight loss › Sweating › Fatigue › Increased appetite › Anxiety › Exophthalmia: Protruding eyeballs (Graves’s disease) - During production of T3 + T4: › Iodine absorbed from bloodstream, concentrated in cells in the thyroid gland and then incorporated into molecules to produce the hormones › Treatment: - Drugs that block thyroid gland’s use of iodine - Radioactive iodine ingested: radioactive iodine taken up by thyroid cells which are then killed by radioactivity. Other body cells don’t absorb iodine so not effected. Radioactive iodine eventually excreted in urine - Surgery to remove all/some of gland: less gland = less hormone - *when cells of thyroid are destroyed there is a risk of developing hypothyroidism

Answer 120

• Hypothyroidism: - Too little thyroxine - Problems with thyroid, pituitary or hypothalamus - Symptoms: › Slow heartrate › Unexplained weight gain › Fatigue › Lack of energy › Intolerance to cold › Swelling of face › Goitre: enlargement of thyroid - Deficiency of iodine can prevent gland from making enough hormones - Thyroid may become enlarged in effort to increase hormone production - Hashimoto’s disease: attack on thyroid gland by immune system - Surgery for thyroid cancer: removal of large portion of gland (causes of hyperthyroidism) - Treatment: › More iodine in diet › Thyroid hormone tablets (dose monitored carefully) - Made from dried and powdered thyroid gland of animals. Contain T3+T4 but not in same human proportions - Contain traces of other hormones › Levothyroxine: thyroxine is isolated and synthesised - Oral and injectable - Most common

Answer 121

• Gene therapy: - Aims to cure/treat genetic abnormalities by identifying faulty genes and inserting healthy ones - Uses genes themselves as treatment - Possibilities: › Replacing mutated gene with healthy copy › Fixing/inactivating mutated gene › Inserting a new gene that will fight the disease › Making the immune system recognise diseased cells - Vector: used to deliver desired DNA into cell. › DNA can be incorporated into the cell’s nucleus and undergo transcription and translation to produce desired protein

Answer 122

• Type 1 Diabetes: - Reprogramming other cells to produce insulin › Insulin gene into vector › Vector infects desired cells (e.g., alpha) › These cells incorporate the new DNA into their nucleus and able to use protein synthesis to make insulin

Answer 123

• Cystic Fibrosis: (autosomal recessive) - Affects lungs and pancreas - Mucous secreting glands become fibrous secreting thick, sticky mucous › Mucous may clog the tiny air passages and trap bacteria: susceptible to infection › Repeated infection and continual blockage of airways = irreversible lung damage and shortened life expectancy - Pancreas: prevents secretion of enzymes required for digestion › Problems with nutrition and need to take care of diet › Diet: low fat, high carb, high protein - Heel prick test as baby - Mutation in CFTR gene results in CF: › Scientists correct faulty CFTR genes in cultured cells by adding normal copies of gene to culture - CF: single gene disorder and lungs are severely affected › Lungs: easily accessible so gene therapy is option › Disease is slow to process enable gene therapy to occur before significant lung damage - Modified common cold virus to act as vector to carry normal genes to CFTR cells in airway of lungs. › First experiment: amount of gene transfer too small, any benefit short lived, too small to have any therapeutic benefit

Answer 124

• Huntington’s disease: - Single gene disorder - Gene therapy could slow down/prevent development - Mutation in single gene on CHR 4 (IT15) › Symptoms rarely appear before 40 › Mutated form of protein “Huntington” results in nerve cells in brain to become damaged - Causes physical, mental and emotional changes - Characterised by occasional unintentional flailing of arms and legs, and difficulty in making voluntary movement of the limbs › Progressive dementia and loss of ability to think clearly - Modified virus to deliver a corrective gene into brain cells that boosts a natural shield against the effects of defective Huntington protein. › Trial on rats and primates

Answer 125

• Cell replacement therapy and tissue engineering: - Stem cells: undifferentiated cells that can repeatedly divide by mitosis for long time and can differentiate into specialised cells - Potential candidate for CRT: loss of/injury to normal cells › Alzheimer’s: brain cell connections and the cells themselves degenerate and die - Progressive form of dementia - Symptoms: memory loss and confusion - Eventually destroys memory and other important mental functions › CRT for Parkinson’s: transplants differentiating stem cells into patients’ brain to replace dying neurons - Uses embryonic stem cells (ethical issues): transplanted cells survived and made connections with adjacent cells - Stem cells also used for tissue engineering: restore healthy tissues or organs to eliminate need for implants. Using stem cells overcomes: using cells from recipient not practicable and not enough normal cells to produce culture - Tissue engineering: requires abundant supply of disease-free cells of specific types: › These cells induced to grow on scaffold to produce 3D tissue › Scaffold: template for tissue growth - Needs high pore size that enable cell growth and diffusion of nutrients - Usually biodegradable so it doesn’t have to be removed via surgery - Scaffold deterioration needs to = cell growth - Stem cells seeded onto scaffold enabling further cell growth and proliferation - Cell covered scaffold inserted into patient, at site in which new tissue is required

Answer 126

• Mutations: change in gene or chromosome leading to new characteristics - Gene mutation: changes in a single gene - Chromosomal mutation: all/part of chromosome affected - Change in base can change AA which can change protein › Gene’s DNA altered = missing or abnormal protein - Sum of mutation characteristics = overall impact mutation will have

Answer 127

• Induced mutation: caused by mutagen - Mutagen: environmental agent that increases rate of mutation occurring › E.g., X-rays early in pregnancy could lead to microcephaly

Answer 128

• Spontaneous mutation: occurred due to error in natural biological process

Answer 129

• Somatic mutation: mutation in body cell - Mutation passed on to daughter cells, but reproductive cells not affected - When person dies mutation dies (not passed on) - Involved in cancerous growths due to mutagen

Answer 130

• Germinal mutation: change in genetic information of gametes that becomes incorporated into DNA of every cell in the body of offspring - Passed on - Individual usually not affected but makes gametes with changed DNA - Conception with affected gamete often aborted naturally - PKU: intellectual deficiency, seizures, failure to produce normal skin pigmentation

Answer 131

• Effect of mutation: - Missense: change in AA and protein - Nonsense: change to STOP base sequence leads to a shorter protein, unable to fulfil function - Silent: no change in AA and protein - Neutral: change in AA, no overall change in protein because AA is same type

Answer 132

``` • Extent of mutation: - Amount of DNA affected - Gene mutation: single gene - Chromosomal mutation: multiple gene › Change in chromosome structure/number › Usually leads to miscarriages ```

Answer 133

• Change in DNA: - Point mutation: only one base is changed › Single nucleotide changed due to being - Inserted: new nucleotide added to strand - Deleted: removed - Substituted: existing nucleotide replaced - Frameshift: when bases are added/removed › Series of 3 bases that code for AA start at different base › Changes way sequence is read › Affect outcome of all DNA from that point › Won’t occur when 3 bases are added or removed as it will code for one less AA - Not frameshift as rest of AA is the same - Longer/shorter protein - Mutation of large DNA section: › Duplication/insertion: section of chromosome occurs x2 › Deletion: segment removed due to breakage › Inversion: break in chromosome, broken piece flips and joined wrong way round › Translocation: part breaks off and re-joined to wrong chromosome › Non-disjunction: in meiosis, when a chromosome pair doesn’t separate (one more and one less in daughter cell) - Aneuploidy: change in chromosome number

Answer 134

• Gene mutation: - Duchenne muscular dystrophy: › Mutation in mother then inherited by son, or occurs in male zygote › Wasting away of muscles › Death due to failure of respiratory muscles - Cystic Fibrosis: › Mutation in chromosome 7 - Gene has code for 1480 AA that make protein that regulates passage of Cl ions across cell › Recessive

Answer 135

``` • Chromosome mutation (trisomy): - Down syndrome: › X3 chromosome 21 › Characteristic facial expression › Intellectual disability › Weak muscles › Heart defects › Partial trisomy: extra copy of chromosome 21 attached to another chromosome - Patau syndrome: › Extra chromosome 13 - Intellectual disability - Cleft palate - Microcephaly - Extra finger › Usually die within a month of birth › From mothers’ egg or fathers sperm - Klinefelter syndrome: › Non-disjunction in males: extra X chromosome or Y chromosome › XXY: normal as boys but develop syndrome as adults › Small testes, sparse body hair › Enlarged breasts › Sometimes has intellectual disability ```

Answer 136

• Chromosome mutation (monosomy): - Cri-du-chat syndrome (partial monosomy): › Missing portion of chromosome 5 › Characteristic cry of infants born with disorder - Problems with larynx and nervous system - Turner syndrome: › Only one X chromosome › Short stature females › Lack secondary sex characteristics › Infertile

Answer 137

• Lethal recessives: - People who inherit both recessive would die before their alleles can be passed on › Allele frequency gradually reduced - Tay-Sachs disease: › Disorder of lipid metabolism › Autosomal recessive › Mutation in HEXA gene that codes for enzyme beta-hexosaminidase - Responsible for breaking down toxic substances including GM2 ganglioside (fatty substance) in nervous system, which destroys neurons › Baby normal for a few months then deterioration that causes intellectual and physical disabilities begin - Death in early childhood

Answer 138

• Gene pool: sum of all alleles in a given population - Population: group of same species in a particular place at a particular time - Allele frequency: how often allele of gene occurs in population

Answer 139

• Migration: causes gene flow and changes in allele frequency - Movement of people from one area to another with intention of permanent settlement

Answer 140

• Gene flow: transfer of alleles from one population to another - Movement of genetic info from one population to another. Facilitated by migration, hut hindered by barriers such as geography and sociocultural factors - Migration enables gene flow, brings alleles not already in population - Barriers to gene flow: inhibit the amount of interbreeding between populations. Isolation leads to separate gene pools forming › Geographical barriers: oceans, mountain ranges, lake systems, deserts, ice sheets - E.g., Indigenous Australians › Sociocultural barriers: economic status, educational background, social position, religion and language are barriers to interbreeding

Answer 141

- Genetic drift: random, non-directional change in allele frequency between generations › Purely by chance › Occurs in populations of all sizes but unlikely to have a significant effect on large populations - plays important role in evolution in small populations

Answer 142

- Founder effect: extreme example of genetic drift › Small group moves away from its homeland and establishes population in new area which later expands › Because of small size, chance causes new groups to have - Different allele frequency from the original population - Decreased genetic variation - May show frequency of alleles no typical of original homeland population Chance of survival is by chance and not due to a specific trait

Answer 143

- Bottleneck effect: extreme example of genetic drift › Event (e.g., natural disaster) severely reduces population size - Allele frequency may (by chance) be different from before the event - Chance of survival is by chance and not due to a specific trait

Answer 144

• Sickle cell anaemia: - Malaria: › Anopheles mosquito which transmits the malaria parasite - Needs quite stagnant pools of water for breeding sites › As human cleared forests in Africa for agriculture - Created additional reeding sites - Increased food supply and increased human population - More bodies on which mosquitos breed - Homozygous for recessive allele › Point mutation in DNA sequence of HBB gene - Codes for beta globulin proteins - Make up Hgb in RBC › Different base sequences mean AA valine is added instead of glutamic acid - Different form of protein, altering Hgb produced which distorts shape of RBC › RBC die early leading to anaemia › RBC are inflexible and get stuck in blood vessels › Fatigue, jaundice, organ damage, high BP, heart failure - Heterozygous: › No ill effects unless oxygen in short supply - RBC show mild sickling › Survival advantage in malaria prevalent areas - Presence of malaria acts as a selective agent for the sickle cell allele - Homozygous dominant › More susceptible to malaria - If person with allele dies before reproducing, allele that causes disease is not passed to next generation. SCA allele prevalent in areas with malaria

Answer 145

• Tay-Sachs disease: - Mutation that leads to absence of enzyme beta-hexosaminidase › Death at early age - Recessive condition - Heterozygous: reduced amount of enzyme › Protection from tuberculosis › Survive TB, reproduce, pass on both alleles › Heterozygote advantage provided by a heterozygous genotype increases percentage of recessive allele in gene pools in areas affected by Tuberculosis - Homozygous recessive: › Die before reproducing due to Tay-Sachs › Don’t pass on recessive alleles - Homozygous dominant: › Affected by TB › May die before reproducing

Answer 146

• Thalassemia: - Hgb: 4 protein chain › 2 alpha globulin chains › 2 beta globulin chains - Alpha thalassaemia: mutation in HBA gene on chr 16 › Decrease levels alpha globulin in Hgb - Beta thalassaemia: mutation in HBB gene on chr 11 › Decrease levels of beta globin in Hgb - *Both are autosomal recessive - People with thalassaemia: less Hgb therefore carry less oxygen in blood › Severity depends on number of genes affected - More common in areas affected by malaria › Alpha most common in south east Asia › Beta most common in Mediterranean basin - Malaria acts as a selective agent › Increase allele frequency of alpha thalassaemia › Lower amount of Hgb gives some protection against malaria › Quicker recovery may be due to increased RBC

Answer 147

• Evolution: gradual change in characteristics of a species - Over time, alleles change so that it is better suited to environment. Environment also changes over time - Characteristics that enhance survival enable succeeding generations to gradually adapt to environment - Species adapt to environment through natural selection and process of adaptation, takes many generations

Answer 148

• Darwin’s theory of natural selection: - Variation: › All members of a species vary › Variations passed on from one generation to the next one - Birth rate: › All living organisms reproduce at a rate far greater than that at which their food supply and other resources increase - Leads to overcrowding - Due to excessive birth rate and limited resources, there is a struggle for existence - Nature’s balance: › Despite high birth rate each species number remains relatively constant

Answer 149

• Survival of the fittest: organisms with favourable characteristics are more likely to survive - Organisms with unfavourable characteristics die before they have a chance to reproduce - Possible because variation among species exists

Answer 150

• Natural selection: selection of favourable alleles in a population that give an organism a greater survival advantage. Principle of evolution through natural selection: - There is variation of characteristics within a species - More offspring of a species are produced than can possibly survive to maturity - Excessive birth rate and limited resources: struggle for existence and competition for survival - Individuals with characteristics best suited to environment have more chance for surviving and reproducing › Survival of the fittest - Favourable characteristics are passed on to the next generation - In gene pool proportion of alleles that produce favourable characteristics gradually increases - Natural selection works on phenotypes: explains why some disadvantageous recessive alleles still exist

Answer 151

• Selective agent: environmental factor acting on population - If environment favours particular characteristics, it will increase its allele frequency - *natural selection is change in allele frequency in populations as a result of a selective agent

Answer 152

• Species: group of individuals that share many characteristics and are able to interbreed under natural conditions to produce fertile offspring • No 2 environments are exactly the same, so certain alleles are favoured more in one environment - Over time allele frequencies of each gene pool will change depending on which characteristics are favoured - Over many generations, populations become more different • If 2 populations are isolated for long time and environmental influences are different enough, major allele frequency changes occur - Become so different that interbreeding is no longer possible › Regarded as two different species

Answer 153

• Speciation: formation of new species due to variation, isolation and selection leading to two groups becoming so different that they can no longer breed - 1. Variation: variation between individuals in species › From processes like mutations, meiosis and epigenetics - 2. Isolation: populations of same species isolated without gene flow › No gene flow between similar gene pools, due to geographical, cultural, behavioural barriers - 3. Selection (differential selection): each population subjected to different selective agents › When the probability of survival for a particular phenotype is greater than others in the population, allowing more of this phenotype to survive and reproduce › Leaves more offspring with the advantageous allele in the next generation - 4. Speciation: allele frequency changes until they become so different that the two groups are no longer able to interbreed › When gene flow is restored between similar populations, interbreeding does not occur thus there are two species rather than populations › 2 populations -> 2 species

Answer 154

• Polymerase chain reaction: enables small amounts of DNA to be replicated, producing testable amounts of DNA to use in analysis techniques. Process is repeated 20-30 times (thermo-recycling). 2-3 hours to produce a billion copies - 1. Denaturation: two DNA strands are separated. › Uses high temperatures (96ºC) to break hydrogen bonds holding two strands together. Separates without disrupting - 2. Annealing: short sections of DNA are bound to the separated strands. › Temperature decreased (50-60ºC), allows primers (short DNA strands) to bind to single DNA strands. › Primers are complementary to either end of the section of DNA to be copied. - 3. Extension: short sections of DNA are extended to produce longer strands. › DNA polymerase used to join new, complementary nucleotides to sections originating with primers: extending nucleotide chain and creates new DNA strand. › However not full length as primer doesn’t begin at end of strand. Eventually most of DNA strands are same length as DNA between location of primers. › DNA polymerase attaches to double stranded DNA once primers are located. › DNA polymerase denatures so lots are required. Taq polymerase doesn’t denature, optimum temp is 68-72ºC

Answer 155

• Gel electrophoresis: technique that can separate DNA strands based on their lengths. - DNA pieces are placed in wells in a semi-solid gel that is immersed in electrolyte solution. Electrodes on either end. - Negatively charged DNA move towards positive electrode, smaller pieces move faster. - Creates a DNA profile. › Use micropipette to place DNA in wells, so DNA diffuses through gel › DNA ladder: usually run at same time. Contains DNA segments with known lengths, results from unknown sample compared to determine length of DNA strand in sample › Visualising DNA: - Ethidium bromide added to agar prior to gel being set, as DNA moves it can pick up some of the chemical. UV light shone over so DNA fluoresce. Con: is carcinogen - Methylene blue dye that binds to DNA. Gel soaked in dye, DNA stains a deeper blue - DNA probes: short sections of a single strand of DNA with radioactive/fluorescent molecule that binds to DNA being tested

Answer 156

• DNA sequencing: determination of precise order of nucleotides in DNA sample. - When DNA forms: each nucleotide loses two phosphate groups and sugar molecule loses H from hydroxyl as it bonds to phosphate of adjacent molecule - Sangers’ method: synthetic nucleotides without hydroxyl group are added to growing strand= dideoxy-ribonucleotides triphosphates (ddNTPs) › Synthetic nucleotide stops elongation of the sequence because there is no hydroxyl group for next nucleotide to attach to. This happens at each of the nucleotides in the DNA sample, creating different lengths- > separated using gel electrophoresis › *Knowing which base was added to create each length allows scientists to determine the order of nucleotides. - Autonomy, confidentiality, equity, and privacy

Answer 157

• Comparative genomics: genome sequences of different species are compared - Complete set of DNA in each cell of an organism is a genome - Study evolutionary changes, identify genes preserved among species and which ones make a species unique

Answer 158

• Endogenous retrovirus: viral sequence that has become part of genome. - Retroviruses store genetic info as RNA. Once it enters a cell RNA -> DNA through reverse transcription - DNA inserted into host cell’s chromosomes - Only becomes endogenous: inserts into a cell whose chromosome will be inherited by the next generation, ovum, or sperm cell - Offspring (and subsequent generations) will have ERV copy in same place, in same chromosome, in every cell

Answer 159

• Mitochondrial DNA: small circular molecules, 37 genes: 24 contain code to make tRNA, 13 make enzymes necessary for cellular respiration reaction. - Inherited from mothers - mtDNA has a higher rate of mutation: amount of mutation roughly proportional to how much time has passed from common ancestor. - Track ancestry

Answer 160

• Protein sequences: by comparing type and sequence of amino acids in similar proteins from different species, degree of similarity can be established. - Degree of difference enables an estimate to be made of the amount of evolution that has taken place since two species developed from a common ancestor - Ubiquitous proteins: found in all organisms and are completely independent of an organism’s specific function or the environment in which it lives. They carry out the same function no matter where they are found › Cytochrome C: performs essential step in production of cellular energy. › To compare cytochrome C they need to be aligned so maximum number of positions with same amino acid can be determined › More similarity= more recently evolved from a common ancestor

Answer 161

• Bioinformatics: use of computers to describe the molecular components of living things - Uses biochemical analysis to gain information about DNA and proteins, and computer software to store and analyse it - Annotation: identifying genes and other biological features in a DNA sequence

Answer 162

• Embryology: comparing the very early stages of the development of organisms

Answer 163

structures that are very similar in structure but maybe used in different ways

Answer 164

• Vestigial structures: structures that may have been important once but have lost or changed their function - Reduced in size and function

Answer 165

• Phylogenetic tree: represents evolutionary relationships between a number of species derived from a common ancestor - Species with more recent common ancestor diverge further up the tree › 1. Join most similar species (recent common ancestor= short branches) › 2. Add next most similar species › 3. With leftover species, join it with the species it has a most recent ancestor with

Answer 166

• Fossils: any preserved trace left by an organism. - Best buried where decomposition is prevented - Soil with no oxygen: complete preservation of soft tissues and bones of animal - Alkaline soil: minerals in bones are not dissolved › New minerals deposited in bone pores, replacing organic matter. Bone becomes petrified, but details still preserved. - Conditions: › Quick burial of material › Presence of hard body parts › Absence of decay organisms › Long period of stability

Answer 167

* Absolute dating: actual age of specimen in years | * Relative dating: comparison of fossils to tell us whether one sample is older or younger than the other

Answer 168

• Potassium Argon dating: based on the decay of radioactive potassium to calcium and argon. - Potassium is a mixture of 3 isotopes: potassium 40 is radioactive an decomposes to form calcium 40 and argon 40. - As rock ages, potassium 40 decreases and argon 40 increases - Determining amounts of K40 and Ar40 enables age of rock to be calculated - Only date rocks older than 100 000 and 200 000 years - Half-life: 1250 billion years - When rocks produced in volcanic eruptions bury bones

Answer 169

• Carbon 14 Dating: based on carbon 14 decay - Carbon 14 produced in upper atmosphere by the action if cosmic radiation on nitrogen. - By measuring amount of radiation liberated by a sample, the ratio of carbon 14 to carbon 12 can be estimated, which can be used to calculate age - Useful up to 60 000 - Half-life: 5730 (plus/minus 40) - Problems: › At least 3 grams of organic material is needed, so accelerator mass spectrometry radiocarbon dating is used to date 100 micrograms. Sample broken up into atoms, and carbon isotopes are counted › After 70 000 only 0.21% of carbon 14 left, too small › Material to be dated must contain organic compounds › Assuming that ratio to carbon 14 to carbon 12 in the atmosphere was constant, even though it varies.

Answer 170

• Stratigraphy: study of layers. - Principle of superposition: assumes that in layers of sedimentary rock, the layers at the top are younger than those beneath them - Correlation of rock strata: matching layers of rock from different areas. Rocks with same fossil are assumed to be same age › Index fossil: fossils or organisms that were on Earth for only a short period of time. Useful in relative dating.

Answer 171

order of humans evidence: fossils and comparative anatomy humans: primates-> haplorrhini->simiiformes->hominoidea-> hominidae-> homininae->homo->sapiens

Answer 172

body, limbs: unspecialised hands/feet: pentadactyl, nails, grasping ringers and gripping toes with friction ridges for gripping, first digit opposable eyes: forward facing for stereoscopic vision, most distinguish colour smell: poor sense of smell teeth: 4 incisors in both upper and lower jaw brain: large and complex, cerebrum size increase and primates evolved reproduction: not restricted to breeding system, rhythmic sexual cycle, long period of parental care for offspring

Answer 173

family=hominidae characteristics: - larger more complex brain than other primates (increased cognitive ability) - 5 cusps in molar teeth of lower jaw - arms that freely rotate at shoulders - wide, shallow chest cavity - no external tail - appendix - diurnal

Answer 174

trend: increased in size cerebral cortex: deals with vision, memory, reasoning and manipulative ability arboreal environment led to large brain for body size: environment favours more accurate vision and tactile perception (more reliant on vision than smell) frontal lobe had greatest enlargement: higher functions (problem solving, thinking, reasoning planning and processing) strong pattern of convolutions: allow SA of brain to be greatly increased.

Answer 175

enable moving about, locating food, social skills, tool making tool making (instead of make): requires predetermined image of what tool looks like, requires highly developed brain greater variety of behavioural responses for variety of environmental problems eg. grooming: reinforces relationships large brain requires large cranium

Answer 176

measuring volume inside the cranium using endocast | determines brain size

Answer 177

primate limbs unspecialised leads to diversity in use pentadactyl, very mobile ->arboreal environment prehensile digits required for tree climbing trend: increased ability to move digits independently of each other opposability: (depends on length of 1st digit compared to the other 4) human toe = not opposable human have longest thumb human hand: short, broad, straight fingers w/ long strong thumb

Answer 178

thumb and finger apply force to palm to transmit force to an object

Answer 179

grasping object between thumb tip and fingertip handling small delicate objects well shows presence of truly opposable thumb

Answer 180

quad->bi | humans: bipedal locomotion with striding gait

Answer 181

hole where brain joins spinal cord trend: moved forward to become more central allows skull to balance apes need large neck muscles to hold head in position, humans don't (weight of skull borne by vertebral column)

Answer 182

c-> s allow upright posture improves balance upright, and allows head to balance cervical curve in neck brings vertebral column directly under centre of gravity of skull double curvature: lumbar vertebrae are wedge-shaped from front to back (forms forward jutting curve)

Answer 183

apes: protruding, humans: flat reduced prognathism: skull balance equal weight infant of and behind FM

Answer 184

broad, short, bowl-shaped BS: supports abdominal organs when standing erect -> better stability for bipedal broad hip bones: allow space for attachment of large buttock muscles-> move body, keep body erect

Answer 185

human: shape and orientation of pelvis means acetabulum right under trunk and head - > allows body weight to be transferred to legs from pelvis acetabulum further apart: femurs converge at knees carrying angle: arrangement of thigh bones to form angle to vertical -> ensures weight distribution remains close to central axis of body when walking human: weight falls through outside of femur -> enables striding gait: body rotated about lower leg and foot-> footsteps follow a straight line better stability upright

Answer 186

weight transferred to outside of femur to knee knee joint: two part hinge joint (condyle) -> hinge on either side of ligaments in middle of joint thus: outer hinge larger and stronger since weight is transmitted there centre of gravity: falls through a line in front of knees - > thus: force that tries to bend knee backwards exists -> resisted by ligaments making up knee joint - > natural resistance= joint that requires no energy to support erect posture

Answer 187

weight: knee joint-> tibia -> talus-> tarsal bones-> metatarsals-> then phalanges via foot arches-> big toe foot lost prehensility to become locomotory organ big toe: large and aligned alongside other toes metatarsals from transverse and longitudinal arch-> enables bipedal

Answer 188

point where gravity is concentrated human: lower centre of gravity-> have longer legs than arms that increase stride length lower centre of gravity: stability when walking/standing

Answer 189

partial contraction of skeletal muscles eg. head erect: back neck muscles are partially contracted muscles that help with upright position: - muscles that bring about movement of the spine, hip, knee, ankle - abdominal muscles * maintained by nervous system and sense organs

Answer 190

walking upright that hip and knee are fully straightened

Answer 191

the foot: - weight transmission: heel->outside of foot-> ball-> crosses ball via transverse arch-> big toe - thus: final moment of striding: whole weight propelled by big toe big toe lost opposability to evolve into weight bearing appendage transverse arch is shock absorber

Answer 192

trunk rotates around pelvis whilst walking -> forward swinging of arms compensates for natural rotation of body (right arm when left leg) arm swinging: keep shoulder 90º to direction of travel and less energy expended. otherwise energy wasted in reversing rotation of body

Answer 193

converge at knee stability whilst walking body can be rotated about lower leg and foot ->weight distribution close to central axis

Answer 194

favours low speed and long distance - energy efficient way of moving - hands free (tools/carry items) - greater height to see further - less body exposed to sunlight - increased exposure to breezes and increased cooling mechanisms

Answer 195

primates have deciduous and permanent teeth dental formulas: number of teeth and shape natural selection led to decrease in teeth number -> reduction in face size and jaw that occurred in primates OWM, primates, humans: 2:1:2:3 - > OWM have large canines projecting beyond level of teeth - >diastema: gap between upper canine and incisor to accommodate lower canine so mouth can close to allow for large upper canine: crown of first lower premolar is slanted back with sharp edge -> upper canine fits tight and is sharpened by grinding against premolar 4 cusps upper 5 cusps lower ->evolved due to fruit diet of apes human dentition: canines don't project/interlock - > more similar to incisors - > small teeth take up less jaw space - > thus: dental arcade evolved from u shape to parabolic

Answer 196

non human apes and early homies have increased prognathism and brow ridge trend: teeth size decreased so face flattened, chin developed and prominent nose bipedalism: flatter face shirts weight to central position to allow skull to balance when upright frontal lobe increased: brain occupies larger volume ->cranium extends forward and brow ridge decreased flatter face and noticeable forehead

Answer 197

``` thicker cranium bones smaller cranial capacity heavy brow ridges no/sloping forehead lower cranium less prominent cheekbones saggital crest FM post central larger prognathic jaw heavy thick mandible no chin larger teeth diastema prominent canine incisor and molar size difference narrow pelvis less wedge shaped LV wide ribcage shorter less mobile thumb long curved fingers parallel femurs arms longer ```

Answer 198

``` thinner cranium bones larger cranial capacity reduced brow ridges vertical forehead dome cranium prominent cheekbones no crest central FM flatter face and smaller jaw slender/thinner mandible chin smaller teeth no diastema less prominent canine even teeth broader pelvis wedge shaped LV smaller ribcage longer thumb with increased opposability shorter straight fingers converging femurs arms shorter ```

Answer 199

``` from laetoli footprints: bipedal (varying gait to humans) lateral transmission of weight longitudinal arch parallel big toe ``` canine: short non projecting no diastema, parabolic shape low forehead more projected jaw femur, pelvis, carrying angle more human like non opposable robust big toe rounded skull at the back s shaped spine= upright stance thumb shorter and less mobile than humans ->heavier finger-> better adapted to power grip (arboreal?)

Answer 200

``` afarensis: 430cm^3 2.8-3.9 mya east africa F= 105-110cm, M=150 cm low sloping forehead short sagittal crest for males diastema curved fingers ``` ``` africanus: 457cm^3 2-3.2 mya south africa F= 110cm, M= 135cm slightly arched forehead smaller brow ridge no diastema some curvature of fingers ```

Answer 201

542cm^3 1.2-1.8 mya not ancestor of humans: part of evolutionary branch with no descendants robust jaw and skull F=1m, M= 1.2m large sagittal crest: for attachment of strong chewing muscles large molars and premolars, small incisors and canines less prognathism than australopithecines wide dish shaped face with zygomatic arch heavy brow ridges

Answer 202

``` 590cm^3 1.5-2.3 mya east and South Africa compared to australopithecines: larger brain, smaller teeth->meat in diet, taller, more erect F= 110cm M= 130cm rounder skull smaller brow ridge central FM moderate prognathism parabolic jaw shot legs long arms curved finger bones: strong power grip able to form precision grip -> adept at tool making ```

Answer 203

``` 1004cm^3 first humans to show modern human like body -> life on ground larger brain curve of dental arcade: shorter and rounder at front shorter compact jaw, chin beginning to form modern teeth (similar diet?) use of fire and tools 145-185cm short stocky body with thicker bones low sloping forehead defined brow ridge large thick jaw without chin decrease in molar size ```

Answer 204

Europe, Asia, northern Africa side brach along pathway to modern human ``` 1485cm^3 adapted to colder environments ->big faces - low large skulls - heavy brow ridges - slightly larger brain ``` back of skull drawn in to bun (occipital bun) lacked chin swept back cheeks: streamlined appearance robust but larger brain prognathism: accentuated by way nasal bone protrudes -> larger, wider nose-> adaptation for environment ``` short (M=150cm) ->limbs shorter heavily jointed with powerful muscles more heavily built than humans barrels shaped chest thick neck muscles ``` large skull with large brain -> extra brain capacity for control of extra muscles

Answer 205

``` Cro magnon: first anatomically modern people in Europe 40 000 to 12 000 ya member of our species - shorter skulls and higher - rounded skull - less prominent brow ridge - reduced face projection - smaller jaw - chin developed - broad and short face - eye sockets well separated large brain, hunter gatherers ``` 1350cm^3

Answer 206

``` neanderthals: 28 000 - 300 000 ya shorter more robust wider shoulders F: 156cm, M: 168cm long low brain case occipital bun thick brown ridge receding foreheads elongated skull flared zygomatic arch depression at back of skull for neck muscle attachment shorter thicker limbs with large joints large robust prognathic jaw lacking chin large teeth barrel shaped ribcage ``` ``` sapiens: 300 000 to present short slender trunks long limbs F: 160 cm, M: 175cm short base high brain case short jaw bony chin Long leg with short arms straight fingers and toes less barrel shaped ribcage ```

Answer 207

anything that is learnt cultural development is important to overcome environmental challenges cultural evolution: gradual improvement in culture, overcoming environmental and other challenges

Answer 208

HOME bases no fire use evidence ``` pebble tools (choppers, scrapers, flakes, chisels) required precision grip 2.5mya tools marked start of cultural evolution -> allowed them to exploit more habitats ```

Answer 209

used oldowan tools -> sharpened by striking one rock to another (skinning animals, chopping meat, breaking open bones, crushing plants, digging edible plant roots) hunter gatherers: diet consisted of plant materials, supplementing meat -> provided complex fats for brain growth -> worked in groups with specific roles: food brought back was shared bulge of Broca (speech production area): pressure to speak spoken language. rudimentary speech -> larynx not capable of making complex sounds both hunter and scavenger: shown by recovered bones with cuts made by stone tools

Answer 210

trend: becoming more independent of environment tools: tear drop shaped. flaked around edges to forms bi faced lumps: used as hand axes found in France (stone and bone) organised: logical thought and working together more systematic tool use: increased commitment to meat eating FIRE mutual cooperation needed to create complex society

Answer 211

kept predators away at night warmth light at night used to stampede animals important for migration during ice age enabled cooking of food: increased food range by improving flavour and digestibility -> made food safe to eat (destroyed parasites)

Answer 212

trend: becoming more independent of environment MOUSTERIAN: production of stone flakes trimmed to form various cutting, scraping, piercing and gouging tools - LEVALLOIS technique: piece of stone trimmed to disc shape, struck by another stone to produce flakes that were flat on one side and had sharp edges - > slow labour intensive, required planning and foresight (significant development of foresight) flake tools joined to handle/spear/arrow by hafting increased brain capacity due to increased importance of meat flake tools enabled those living in colder climates to become good clothe makers buried their dead: ceremonial burial, spirituality

Answer 213

finer baldes, projectile weapons ~40 000 modern humans moved to Europe -> brought clothes and shelter -> helped survive winter AURIGNACIAN: blades made by removing long, flat rectangles from the core stone, easy to handles, effective in cutting SOLUTREAN: willow leaf, laurel leaf points. - > made by carefully retouching blades produced from original stone core by pressure flaking - > for aesthetics MAGDALENIAN: bone and antler > flint and stone for tools and art - > made by using a burin, chisel like cutter (tool used for making other tools) - > burin: blade shaped so it had a sharp cutting point - bone and antler and ivory cut to make orange of tools from fine needles to barbed spear points and spear throwers

Answer 214

- increased manipulation of materials - increased complexity of tools - greater variety of materials being used to make tools - improved workmanship and development of equipment needed to make tools - increased specialisation of tools

Answer 215

olduvai Africa. 2.6-1.7 mya. st acheul France, 1.7-200 000 Le moustier France. 200 000- 40 000 Aurignac France. 43 000-26 000 Solutre France. 22 000- 19000 Le madeleine France. 18000-12000

unit 3 + unit 4 Flashcards

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