Bio 6 Flashcards

Question

6.3 Application: Explain the causes and consequences of blood clot formation in coronary arteries.

Answer 1

Consequences: the occlusion of a coronary artery by a blood clot may lead to an acute myocardial infarction (heart attack) Causes: -blood clots form when the vessels are damaged as a result of the deposition of cholesterol -aheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen --atherosclerosis -restricted blood flow increases pressure in the artery, leading to damage to the arterial wall (from shear stress) -damaged region is repaired with fibrous tissue which significantly reduces the elasticity of the vessel wall -smooth lining of the artery is progressively degraded, lesions form - atherosclerotic plaques -plaque ruptures -> blood clotting -> forms thrombus -> restricts blood flow -thrombus is dislodged it becomes an embolus and can cause a blockage in a smaller arteriole -coronary occlusion -damage to the capillary epithelium -hardening of arteries -rupture of atheroma Factors that are correlated with an increased risk of coronary thrombosis: -smoking -high blood cholesterol concentration -high blood pressure -diabetes -obesity -lack of exercise

Answer 2

It is the innate immune system: non-specific in its response. -non-specific -non-adaptive -main component: phagocytic white blood cells that engulf and digest foreign bodies -other components: inflammation, fever and antimicrobial chemicals Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to disease Phagocytes -solid materials (such as pathogens) are ingested by a cell (i.e. cell 'eating' via endocytosis) -phagocytic leukocytes (WBC) circulate in the blood and move into the body tissue freely in response to infection -damaged tissues release chemicals (e.g histamine) which draw white blood cells to the site of infection -extensions surround the pathogen and then fuse to form an internal vesicle -vesicle is then fused to a lysosome and the pathogen is digested -antigens (fragments from pathogens) may be presented on the surface of the phagocyte in order to stimulate the third line of defence

Answer 3

Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity -differentiate between particular pathogens and target a response that is specific to a given pathogen -respond rapidly upon re-exposure to a specific pathogen, preventing symptoms from developing (immunological memory) Lymphocytes -when phagocytic leukocytes engulf a pathogen, some will present the digested fragments (antigens) on their surface -these antigen-presenting cells (dendritic cells) migrate to the lymph nodes and activate specific helper T lymphocytes -helper T cells then release cytokines to activate the particular B cell capable of producing antibodies specific to the antigen -activated B cell will divide and differentiate to form short-lived plasma cells that produce high amounts of specific antibody -antibodies will target their specific antigen, enhancing the capacity of the immune system to recognise and destroy the pathogen -a small proportion of activated B cell (and activated TH cell) will develop into memory cells to provide long-lasting immunity

Answer 4

• Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells -kill or inhibit the growth of microbes (specifically bacteria) by targeting prokaryotic metabolism including: -key enzymes -70S ribosomes -components of the cell wall -eukaryotic cells do not possess these features -antibiotics will target the pathogenic bacteria and not the infected host -either kill the invading bacteria (bactericidal) or suppress its potential to reproduce (bacteriostatic) • Viruses lack a metabolism and cannot therefore be treated with antibiotics -do not possess a metabolism and instead take over the cellular machinery of infected host cells -they cannot be treated with antibiotics and must instead be treated with specific antiviral agents

Answer 5

• Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance -confer resistance by encoding traits that: -degrade the antibiotic -block its entry -increase its removal -alter the target -resistant strains of bacteria can proliferate very quickly following the initial mutation -can be passed to susceptible strains via bacterial conjugation (horizontal gene transfer) The prevalance of resistant bacterial strains is increasing rapidly with human populations due to a number of factors: -over-prescribed (particularly broad-spectrum drugs) or misused (e.g. given to treat a viral infection) -many are freely available without a prescription and certain antibiotics -commonly included in livestock feed -multi-drug resistant bacteria are especially common in hospitals -an example of an antibiotic resistant strain of bacteria is Golden Staph (MRSA - Methicillin Resistant Staphylococcus aureus) Solutions: -doctors prescribing antibiotics only for serious bacterial infections -patients completing courses of antibiotics to eliminate infections completely -hospital staff maintaining high standards of hygiene to prevent cross-infection -farmers not using antibiotics in animal feeds to stimulate growth Pharmaceutical companies developing new types of antibiotics - no new types have been introduced since the 1980s

Answer 6

-Florey and Chain's team developed a method of growing the fungus Penicillium in liquid culture -also developed methods for producing reasonably pure samples of penicillin from the cultures -the penicillin killed bacteria on agar plates, but they needed to test whether it would control bacterial infections in humans. Florey and Chain conducted experiments to test penicillin on bacterial infections in mice. -8 mice were injected with hemolytic streptococci and four of these mice were subsequently injected with doses of penicillin -untreated mice died of bacterial infection -those treated with penicillin all survived demonstrating its antibiotic potential -Florey and Chain decided that they should next do tests on human patients, which required much larger quantities. -when enough penicillin had been produced, a 43-year-old policeman was chosen for the first human test. -he had an acute and life-threatening bacterial infection causes by a scratch on the face from a thorn on a rose bush. -he was given penicillin for four das and his condition improved considerably, but supplies of penicillin ran out and he suffered a relapse and died from the infection. -larger quantities of penicillin were produced and five more patients with acute infections were tested. All were cured of their infections, but sadly one of them died.

Answer 7

HIV infects helper T cells, disabling the body's adaptive immune system -causes a variety of symptoms and infections collectively classed AIDS Effects of HIV: -infection -> virus undergoes a period of inactivity (clinical latency) during which infected helper T cells reproduce -the virus becomes active again and begins to spread, destroying the T lymphocytes in the process -reduction in the number of helper T cells -> antibodies are unable to be produced -> lowered immunity -body becomes susceptible to opportunistic infections, eventually resulting in death if the condition is not managed Transmission of HIV: -through the exchange of body fluids (including unprotected sex, blood transfusions, breastfeeding, etc.) -HIV through sexual contact can be minimised by using latex protection (i.e. condoms) -HIV is a global issue, but is particularly prevalent in poorer nations with poor education and health systems

Answer 8

• Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries. **because gas exchange is actually passive! -02 consumed by cells during cellular respiration -carbon dioxide produced as a waste product -02 is constantly being removed from the alveoli into the bloodstream (and CO2 is continually being released) -lungs function continually cycles fresh air into the alveoli from the atmosphere -02 levels must stay high in alveoli (and diffuse into the blood) and CO2 levels stay low (and diffuse from the blood) -the lungs are also structured to have a very large surface area, so as to increase the overall rate of gas exchange

Answer 9

There are two types of alveolar cells - type I pneumocytes and type Il pneumocytes • Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange. Function: -involved in the process of gas exchange between the alveoli and the capillaries Structure: -flattened in shape to minimise diffusion distance for respiratory gases -connected by occluding junctions, which prevents the leakage of tissue fluid into the alveolar air space -amitotic and unable to replicate -type I pneumocytes are amitotic and unable to replicate, however type II cells can differentiate into type I cells if required • Type I pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension Structure: -cuboidal in shape and possess many granules (for storing surfactant components) -provides an area from which carbon dioxide can evaporate into the air and be exhaled. Function: -responsible for the secretion of pulmonary surfactant -create a moist surface -> easier for oxygen to diffuse across the alveolar and capillary membranes when dissolved in liquid -> reduces surface tension -type I pneumocytes secrete a liquid known as pulmonary surfactant which reduces the surface tension in alveoli -surface tension is the elastic force created by a fluid surface that minimises the surface area (via cohesion of liquid molecules) -as an alveoli expands with gas intake, the surfactant becomes more spread out across the moist alveolar lining -this increases surface tension and slows the rate of expansion, ensuring all alveoli inflate at roughly the same rate

Answer 10

• Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles -enters the respiratory system through the nose or mouth and passes through the pharynx to the trachea -trachea -> divides into two bronchi (singular: bronchus) -> connect to the lungs -right lung is composed of three lobes, while the left lung is only comprised of two (smaller due to position of heart) -bronchi divide into many smaller airways called bronchioles, greatly increasing surface area -bronchiole terminates with a cluster of air sacs called alveoli, where gas exchange with the bloodstream occurs nostrils > nasal cavity > pharynx > larynx > trachea > bronchi (with cartilaginous rings) > bronchioles (without cartilage) > alveoli.

Answer 11

-have a very thin epithelial layer (one cell thick) to minimise diffusion distances for respiratory gases -surrounded by a rich capillary network to increase the capacity for gas exchange with the blood -roughly spherical in shape, in order to maximise the available surface area for gas exchange -internal surface is covered with a layer of fluid, as dissolved gases are better able to diffuse into the bloodstream

Answer 12

• Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them. -external intercostal contract -> rise in ribcage -diaphragm contracts to make space in thorax -pressure in the chest < atmospheric pressure, air will move into the lungs (inspiration) -internal intercostal contract -> lower in ribcage -diaphragm relaxes -abdominal muscles contract to force air out -when the pressure in the chest > atmospheric pressure, air will move out of the lungs (expiration) • Different muscles are required for inspiration and expiration because muscles only do work when they contract. -muscles that increase the volume of the chest cause inspiration (as chest pressure is less than atmospheric pressure) -muscles the decrease the volume of the chest cause expiration (as chest pressure is greater than atmospheric pressure)

Answer 13

Lung cancer describes the uncontrolled proliferation of lung cells, leading to the abnormal growth of lung tissue (tumour) -the tumours can remain in place (benign) or spread to other regions of the body (malignant) -lungs possess a very rich blood supply, increasing the likelihood of the cancer spreading (metastasis) to other body regions Symptoms: -difficulties with breathing -persistent coughing -include coughing up blood, wheezing, respiratory distress and weight loss -loss of appetite, weight loss -general fatigue -if the cancer mass compresses adjacent organs it can cause: -chest pain, difficulty swallowing and heart complications Causes: -smoking: contains many mutagenic chemicals. As every cigarette carries a risk, the incidence of lung cancer increases with the number smoked per day -air pollution: sources of air pollution that are most significant are diesel exhaust fumes, nitrogen oxides from all vehicle exhaust fumes and smoke from fossil fuels -radon gas causes (a radioactive gas that leaks out of certain rocks such as granite). It accumulates in badly ventilated buildings and people then inhale it. -certain infections -genetic predispositions

Answer 14

-degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae) -damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase -this elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall -loss of elasticity results in the abnormal enlargement of the alveoli -> lower total surface area for gas exchange Cause: -smoking: the chemical irritants in cigarette smoke damage the alveolar walls -a small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation Symptoms: -shortness of breath -expansion of the ribcage -cyanosis and -increased susceptibility to chest infections -fatigue -weezing -chest tightness -anxietv

Answer 15

• External and internal intercostal muscles, and diaphragm and abdominal muscles are examples of antagonistic muscle action. -antagonistic means working oppositely - when the inspiratory muscles contract, the expiratory muscles relax (and vice versa) Inspiration -the diaphragm and external intercostals (plus some accessory muscles) -diaphragm muscles contract -> diaphragm flatten -›increase the volume of the thoracic cavity -External intercostals contract -> pulling ribs upwards and outwards (expanding chest) Expiration -abdominal muscles and internal intercostals (plus some accessory muscles) -diaphragm relax -> diaphragm curves upwards reduce the volume of the thoracic cavity -Internal intercostal muscles contract, pulling ribs inwards and downwards (reducing breadth of chest) -abdominal muscles contract and push the diaphragm upwards during forced exhalation

Answer 16

Ventilation can either be monitored by: -simple observation (counting number of breaths per minute) -simple apparatus -data logging with a spirometer (recording the volume of gas expelled per breath) - chest belt and pressure meter (recording the rise and fall of the chest) Ventilation rate and tidal volume can be measured by spirometer: -involves measuring the amount (volume) and / or speed (flow) at which air can be inhaled or exhaled -a device that detects the changes in ventilation and presents the data on a digital display -simplistic method is breathing into a balloon and measuring the volume of air in a single breath -volume of air can be determined by submerging the balloon in water and measuring the volume displaced (Iml = 1cm3)

Answer 17

• Neurons are specialised cells that function to transmit electrical impulses within the nervous system. Neurons contain: -dendrites: short-branched fibres that convert chemical information from other neurons or receptor cells into electrical signals -axon: an elongated fibre that transmits electrical signals to terminal regions for communication with other neurons or effectors -soma: a cell body containing the nucleus and organelles, where essential metabolic processes occur to maintain cell survival -myelin sheath: improves the conduction speed of electrical impulses along the axon, but require additional space and energy -nervous system converts sensory information into electrical impulses in order to rapidly detect and respond to stimuli

Answer 18

• The myelination of nerve fibres allows for saltatory conduction. -myelin functions as an insulating layer -the main purpose of the myelin sheath is to increase the speed of electrical transmissions via saltatory conduction -allows nerve impulse to jump across gaps in the myelin sheath called the nodes of Ranvier and jump from node to node

Answer 19

• Neurons pump sodium and potassium ions across their membranes to generate a resting potential. -resting potential is the difference in charge across the membrane when a neuron is not firing -the inside of the neuron is more negative relative to the outside in resting potential The maintenance of a resting potential is controlled by sodium-potassium pumps --active process: -expels 3 Na+ ions for every 2 K+ ions admitted (additionally, some K+ ions will then leak back out of the cell) -as there are more positively charged ions outside of the cell and more negatively charged ions inside the cell - electrochemical gradient -requires hydrolysis of ATP

Answer 20

-action potentials are the rapid changes in charge across the membrane that occur when a neuron is firing • An action potential consists of depolarization and repolarization of the neuron (in between has a refractory period) Depolarisation -a sudden change in membrane potential - usually from a (relatively) negative to positive internal charge -in response to a signal initiated at a dendrite, sodium channels open within the membrane of the axon -as Na+ ions are more concentrated outside of the neuron, the opening of sodium channels causes a passive influx of sodium -the influx of sodium causes the membrane potential to become more positive (depolarisation) Repolarisation -the restoration of a membrane potential following depolarisation (i.e. restoring a negative internal charge) -influx of sodium, potassium channels open within the membrane of the axon -K+ ions are more concentrated inside the neuron, opening potassium channels causes a passive efflux of potassium -efflux of potassium causes the membrane potential to return to a more negative internal differential (repolarisation) Refractory Period -the period of time following a nerve impulse before the neuron is able to fire again -normal resting state: sodium ions are predominantly outside the neuron and potassium ions mainly inside (resting potential) -ionic distribution is largely reversed (in de and repolarization) so the resting potential must be restored via the antiport action of the sodium- potassium pump

Answer 21

• Nerve impulses are action potentials propagated along the axons of neurons. -nerve impulses are action potentials that move along the length of an axon as a wave of depolarisation -depolarisation occurs when ion channels open and cause a change in membrane potential -ion channels that occupy the length of the axon are voltage-gated (open in response to changes in membrane potential) -depolarisation at one point of the axon triggers the opening of ion channels in the next segment of the axon -causes depolarisation to spread along the length of the axon as a unidirectional 'wave' • Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential. -an action potential of the same magnitude will always occur provided a minimum electrical stimulus is generated - threshold potential is the level required to open voltage-gated ion channels -if the threshold potential is not reached, an action potential cannot be generated and hence the neuron will not fire • A nerve impulse is only initiated if the threshold potential is reached. -threshold potentials are triggered when the combined stimulation from the dendrites exceeds a minimum level of depolarisation -if the overall depolarisation from the dendrites is sufficient to activate voltage-gated ion channels in one section of the axon, the resulting displacement of ions should be sufficient to trigger the activation of voltage-gated ion channels in the next axon section

Answer 22

• Synapses are junctions between neurons and between neurons and receptor or effector cells. -neurons transmit information across synapses by converting the electrical signal into a chemical signal

Answer 23

• When presynaptic neurons are depolarized they release a neurotransmitter into the synapse À -neurotransmitters are released in response to the depolarisation of the axon terminal of a presynaptic neuron -bind to receptors on post-synaptic cells and can either trigger (excitatory) or prevent (inhibitory) a response

Answer 24

Acetylcholine: neurotransmitter -released at neuromuscular junctions and binds to receptors on muscle fibres to trigger muscle contraction -released within the autonomic nervous system to promote parasympathetic responses ('rest and digest') -created in the axon terminal by combining choline with an acetyl group (at cholinergic synapses) -stored in vesicles within the axon terminal until released via exocytosis in response to a nerve impulse -activates a post-synaptic cell by binding to one of two classes of specific receptor (nicotinic or muscarinic) -must be continually removed from the synapse, as overstimulation can lead to fatal convulsions and paralysis -acetylcholine -> two component parts by the synaptic enzyme acetylcholinesterase (AChE) -either released into the synapse from the presynaptic neuron or embedded on the membrane of the post-synaptic cell -liberated choline is returned to the presynaptic neuron where it is coupled with another acetate to reform acetylcholine

Answer 25

-blocking of acetylcholine by the binding of neonicotinoid pesticides to acetylcholine receptors -neonicotinoid pesticides cannot be broken down by acetylcholinesterase -> permanent overstimulation of target cells -overstimulation results in fatal convulsions and paralysis -insects have a different composition of acetylcholine receptors which bind to neonicotinoids much more strongly -more toxic to insects than mammals -> highly effective pesticide Disadvantages: -linked to a reduction in honey bee populations (bees are important pollinators within ecosystems) -linked to a reduction in bird populations (due to the loss of insects as a food source)

Answer 26

-oscilloscopes are scientific instruments that are used to measure the membrane potential across a neuronal membrane X axis: time (ms) Y axis: membrane potential (mV) A typical action potential will last for roughly 3 - 5 milliseconds and contain 4 key stages: Resting potential: Before the action potential occurs, the neuron should be in a state of rest (approx. -70 mV) Depolarisation: A rising spike corresponds to the depolarisation of the membrane via sodium influx (up to roughly +30 mV) Repolarisation: A falling spike corresponds to repolarisation via potassium efflux (undershoots to approx. -80 mV) Refractory period: The oscilloscope trace returns to the level of the resting potential (due to the action of the Na+/K+ pump) **an action potential will only occur if the initial depolarisation exceeds a threshold potential of approximately -55 mV

Answer 27

• Insulin and glucagon are released by and a cells of the pancreas to control blood glucose concentration. When blood glucose levels are high (e.g. after feeding: -insulin is released from beta (B) cells of the pancreas and cause a decrease in blood glucose concentration May involve the following: -(high blood glucose levels) detected by pancreas islet cells/beta cells; -stimulating glycogen synthesis in the liver (glycogenesis) (glucose -> glycogen) -promoting glucose uptake by the liver and adipose tissue -increasing the rate of glucose breakdown (by increasing cell respiration rates) -glucose converted to fatty acids/triglycerides/ fat; -stimulates cells to absorb glucose; **negative feedback process; When blood glucose levels are low (e.g. after exercise): -glucagon is released from alpha (a) cells of the pancreas and cause an increase in blood glucose concentration May involve the following: -stimulating glycogen breakdown in the liver (glycogenolysis) -conversion of polysaccharides/glycogen (in the liver) to glucose -promoting glucose release by the liver and adipose tissue -decreasing the rate of glucose breakdown (by reducing cell respiration rates)

Answer 28

Type 1 diabetes: unable to produce insulin Type 2 diabetes: failing to respond to insulin production Type l: -occurs during early childhood -caused by the destruction of beta cells -insulin injections Type 2: -usually occurs during adulthood -caused by the down regulation of insulin receptors -controlled by managing diet and lifestyle

Answer 29

• Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature -primary role of thyroxin is to increase the basal metabolic rate (amount of energy the body uses at rest) -achieved by stimulating carbohydrate and lipid metabolism via the oxidation of glucose and fatty acids -increasing metabolic activity -> production of heat -hence thyroxin helps to control body temperature -thyroxin is released in response to a decrease in body temperature in order to stimulate heat production -partially composed of iodine; a deficiency of iodine in the diet -> decreased production of thyroxin -cold temp. -> hypothalamus -> thyroxin release -> increased metabolic rate -> generate heat -> increase in body temp.

Answer 30

• Leptin is secreted by cells in adipose tissue and act on the hypothalamus of the brain to inhibit appetite -the concentration of leptin in the blood is controlled by food intake and the amount of adipose tissue in the body. -regulates fat stores within the body by suppressing appetite -leptin binds to receptors located within the hypothalamus -> inhibit appetite -overeating -> more adipose cells to formed -> more leptin is produced -> suppressing further appetite -starvation -> reduction in adipose tissue -> less leptin is released -> hunger -obese people are constantly producing higher levels of leptin -> body becomes progressively desensitised to the hormone -they are more likely to feel hungry, less likely to recognise when they are full and are hence more likely to overeat -leptin resistance also develops with age, increasing the potential for weight gain later in life (e.g. the 'middle-age spread')

Answer 31

-leptin was considered as a form of treatment for individuals with clinical obesity -leptin injections -> reduce hunger -> limit food intake -> weight loss Experiment shows that: -most cases of obesity are caused by an unresponsiveness to leptin and not a leptin deficiency -hence, very few participants experienced significant weight loss in response to leptin injections -many patients did experience adverse side effects from leptin injections, including skin irritations -leptin treatments are not considered to be an effective way of controlling obesity

Answer 32

• Melatonin is secreted by the pineal gland to control circadian rhythms -secretion controlled by cells in the hypothalamus called the suprachiasmatic nuceli (SCN) -retina detects light -> sends signals to SCN-> sends signals to the pineal gland -controls circadian rhythms/biological clocks «in mammals» -production is controlled by amount of light detected by the retina -produced by the pineal gland of the brain in response to changes in light -light exposure -> hypothalamus -> inhibits melatonin secretion -melatonin is secreted in response to periods of darkness, resulting in higher concentrations at night -circadian rhythms are driven by an internal circadian clock -can also be modulated by external factors -melatonin is responsible for synchronising circadian rhythms and regulates the body's sleep schedule **production/secretion is directly proportional to night time duration -melatonin secretion is suppressed by bright light (principally blue wavelengths) -hence levels increase during the night -melatonin secretion becomes entrained to anticipate the onset of darkness and the approach of day -melatonin functions to promote activity in nocturnal animals and conversely promotes sleep in diurnal animals (like humans) -affects «seasonal» reproduction/sleep-wake cycles/jet lag -melatonin levels naturally decrease with age, leading to changes in sleeping patterns in the elderly

Answer 33

-alteration of circadian rhythm caused by the body's inability to rapidly adjust to a new time zone following extended air travel (jet' lag) -pineal gland continues to secrete melatonin according to the old time zone -> sleep schedule is not synchronised to the new timezone -symptoms of jet lag include fatigue, headaches, lethargy, increased irritability and reduced cognitive function -jet lag should resolve as the body resynchronises its circadian rhythm -taking melatonin near the sleep time of the new time zone can help recalibrate the body -artificially increasing melatonin levels at the new night time -> body can respond quicker to the new day-night schedule

Answer 34

• A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone XX = female XY = male Y chromosomes is shorter than X chromosome -Y chromosome includes a gene called the SRY gene (Sex Determining Region Y) -> male development -SRY codes for a DNA-binding protein called TDF (testis determining factor) -TDF stimulates the expression of other genes that cause testis development. -SRY gene -> testis-determining factor (TDF) -> embryonic gonads form into testes (male gonads) -the testes produce testosterone to promote the further development of male sex characteristics -no TDF protein (i.e. no Y chromosome) -> ovaries -produce estrogen and progesterone to promote the development of female sex characteristics

Answer 35

• Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty. -testes develop testosterone-secreting cells at an early stage and these produce testosterone until about the 15th week of pregnancy. -during the weeks of secretion, testosterone causes male genitalia to develop. -testosterone = male reproductive hormone -secreted by the testes Functions: -pre-natal development of male genitalia -involved in sperm production following the onset of puberty -aids in the development of secondary sex characteristics (including body hair, muscle mass, deepening of voice, etc.) -helps to maintain the male sex drive

Answer 36

• Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty. -main female reproductive hormones (secreted by the ovaries) are estrogen and progesterone Functions: -promote the pre-natal development of the female reproductive organs -responsible for the development of secondary sex characteristics (including body hair and breast development) -involved in monthly preparation of egg release following puberty (via the menstrual cycle) -initially, estrogen and progesterone are secreted by the mother's ovaries and then the placenta

Answer 37

The menstrual cycle is controlled by a complex interplay of hormones and feedback mechanisms between the brain, ovaries, and uterus. The two main hormones involved in controlling the menstrual cycle are follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are produced by the pituitary gland in the brain. The menstrual cycle begins with the release of FSH, which stimulates the growth and development of follicles in the ovaries. As the follicles mature, they produce estrogen, which causes the lining of the uterus to thicken in preparation for a possible pregnancy. When estrogen levels reach a certain threshold, the pituitary gland responds by releasing a surge of LH, which triggers ovulation – the release of an egg from the ovary. The egg then travels through the fallopian tube towards the uterus. After ovulation, the remaining follicle transforms into the corpus luteum, which produces progesterone to prepare the uterus for a possible pregnancy. If the egg is fertilized by a sperm and implants in the uterus, the developing embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum and keeps progesterone levels high. If the egg is not fertilized, the corpus luteum eventually disintegrates, causing progesterone levels to drop and triggering the shedding of the uterine lining – menstruation. The cycle then begins again with the release of FSH. Overall, the menstrual cycle is a complex and finely tuned process that is controlled by a delicate balance of hormones and feedback mechanisms. Any disruptions or imbalances in this system can lead to menstrual irregularities or fertility problems.

Answer 38

IF drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy. Down regulation -drugs are used to halt the regular secretion of FSH and LH -> stops the secretion of estrogen and progesterone -doctors can take control of the timing and quantity of egg production by the ovaries -typically delivered in the form of a nasal spray Superovulation -involves using artificial doses of hormones to develop and collect multiple eggs from the woman -patient is firstly injected with large amounts of FSH to stimulate the development of many follicles -follicles are then treated with hCG; a hormone usually produced by a developing embryo -CG stimulates the follicles to mature and the egg is then collected (via aspiration with a needle) prior to the follicles rupturing Fertilisation -extracted eggs are then incubated in the presence of a sperm sample from the male donor -eggs are then analysed under a microscope for successful fertilisation Implantation -two weeks prior to implantation, the woman begins to take progesterone treatments to develop the endometrium -healthy embryos are selected and transferred into the female uterus (or the uterus of a surrogate) -multiple embryos are transferred to improve chances of successful implantation (hence multiple births are a possible outcome) -roughly two weeks after the procedure, a pregnancy test is taken to determine if the process has been successful

Answer 39

Original soil and seed theory: -male produces a 'seed' which forms an 'egg' when mixed with menstrual blood (the 'soil') William Harvey tested Aristotle's theory using a natural experiment with deers: -unable to detect a growing embryo until approximately 6 - 7 weeks after mating had occurred -so concluded that Aristotle's theory was incorrect and that menstrual blood did not contribute to the development of a fetus -unable to identify the correct mechanism of sexual reproduction and incorrectly asserted that the fetus did not develop from a mixture of male and female 'seeds' -Harvey failed to solve the mystery of sexual reproduction because effective microscopes were not available when he was working -so fusion of gametes and subsequent embryo development remained undiscovered at his time

Answer 40

Testis: responsible for the production of sperm and testosterone (male sex hormone) Epididymis: site where sperm matures and develops the ability to be motile (i.e. "swim") - mature sperm is stored here until ejaculation Sperm Duct: long tube which conducts sperm from the testes to the prostate gland (which connects to the urethra) during ejaculation Seminal Vesicle: secretes fluid containing fructose (to nourish sperm), mucus (to protect sperm) and prostaglandin (triggers uterine contractions) Prostate Gland: secretes an alkaline fluid to neutralise vaginal acids (necessary to maintain sperm viability) Urethra: conducts sperm / semen from the prostate gland to the outside of the body via the penis (also used to convey urine)

Answer 41

Ovary: where oocytes mature prior to release (ovulation) - it also responsible for estrogen and progesterone secretion Fimbria: a fringe of tissue adjacent to an ovary that sweep an oocyte into the oviduct Oviduct: transports the oocyte to the uterus - it is also typically where fertilisation occurs Uterus: the organ where a fertilised egg will implant and develop (becoming an embryo) Endometrium: the mucous membrane lining of the uterus, it thickens in preparation for implantation or is otherwise lost (via menstruation) Vagina: passage leading to the uterus by which the penis can enter (uterus protected by a muscular opening called the cervix)

Answer 42

plasma/water; dissolved gases / CO2 / 02; erythrocytes / red blood cells; leucocytes / white blood cells; lymphocytes and phagocytes; platelets; hormones / named hormone(s); amino acids / albumin / antibodies; salts / minerals / ions other named solute in plasma apart from glucose, urea and plasma proteins;

Answer 43

-atria collect blood from veins (vena cava/ pulmonary);collect blood while ventricles are contracting; -atria pump blood into ventricles/ensure ventricles are full: -ventricles pump blood into arteries/out of the heart; -ventricles pump blood at high pressure because of their thicker, muscular walls; -mention of heart valves working with atria and ventricles to keep blood moving; -left ventricle pumps blood to systems and right ventricle pumps blood to lungs; Both left and right ventricles with correct function required for mark to be awarded.

Answer 44

a. example of a nutrient e.g. glucose; b. oxygen/02; c. carbon dioxide/CO2; d. nitrogen/N2; e. hormones; f. antibodies; g. urea:

Answer 45

Amylase - Carbs -begins in the mouth with the release of amylase from the salivary glands (amylase = starch digestion) -secreted by the PANCREAS in order to continue carbohydrate digestion within the small intestine -enzymes for disaccharide hydrolysis are often immobilised on the epithelial lining of the small intestine, near channel proteins -substrate: starch - amylose and amylopectin -amylose -> amylase -> maltose -amylopectin -> amylase -> dextrins Protease - Protein -begins in the stomach with the release of proteases that function optimally in an acidic pH **in the stomach, pepsin is the main digestive enzyme attacking proteins. -secreted by the PANCREAS -proteins/polypeptides -> short peptides -endopeptidases work optimally in neutral environments (pH ~ 7) as the pancreas neutralises the acids in the intestine Lipase - Lipids -breakdown occurs in the intestines, beginning with emulsification of fat globules by bile released from the gall bladder -smaller fat droplets are then digested by lipases released from the PANCREAS -triglycerides -> glycerol/fatty acids + monoglycerides Phospholipase-Phospholipids -phospholipids -> fatty acids, glycerol and phosphate

Answer 46

Nucleases: -digests DNA and RNA into nucleotides. Maltase: -digests maltose into glucose. Lactase: -digests lactose into glucose and galactose. Sucrase: -digests sucrose into glucose and fructose. Exopeptidases (a type of protease): -digest peptides -removes single amino acids either from the carboxyl or amino terminal of the chain until only a dipeptide is left. Dipeptidases: -digest dipeptides into amino acids

Answer 47

So it can be reused or be linked to secondary functions like membrane transport.

Answer 48

-villi look into the lumen -microvilli are on top of villis -small intestine wall has many folds.

Answer 49

-peristalsis is the involuntary, wave-like contraction of muscle layers of the small intestine -contraction of circular muscles behind the food constricts the guy to prevent it from being pushed back towards the mouth -contraction of longitudinal muscle where the food is located moves it on along the gut. -swallowed food moves quickly down the esophagus to the stomach in one continuous peristaltic wave. -peristalsis only occurs in one direction away from the mouth. **main function of peristalsis in the intestine is churning of the semi-digested food to mix it with enzymes and thus speed up the process of digestion.

Answer 50

capillary: -maintain a concentration gradient for absorption by rapidly transporting absorbed products away. epithelial cell: -secretio -selective absorption -trans cellular transport -tight junctions in between the epithelial cells = maximum movement can occur because nothing can slip out -brush border (where the microvilli) can increase the surface area lacteal: -absorb lipids from the intestine into the lymphatic system (which are later reabsorbed back into normal circulation) goblet cell: -secrete mucus to protect the mucous membranes where they are found

Answer 51

Taking in substances through cell membranes or layers of cells in particular from the lumen of the gut into the blood or lymph capillaries

Answer 52

carbohydrates) glucose, fructose, galactose and other monosaccharides -(proteins) any of the twenty amino acids used to make proteins -(lipids) fatty acids, monoglycerides and glycerol -bases from digestion of nucleotides -mineral ions such as calcium, potassium and sodium (no digestion required) -vitamins such as ascorbic acid (vitamin C) (no digestion required)

Answer 53

Products of lipase digestion: fatty acids and monoglycerides -can be absorbed into villus epithelium cells by simple diffusion as they are hydrophobic -also absorbed by facilitated diffusion as there are fatty acid transporters (proteins in the membrane of the microvilli) -once inside the epithelium cells, fatty acids are combined with monoglycerides to produce triglycerides ( cannot diffuse back out in the lumen) -triglycerides coalesce with cholesterol to form droplets with a diameter of about 0.2 (um), which become coated in phospholipids and protein -these lipoprotein particles are released by exocytosis through the plasma membrane on the inner side of the villus epithelium cells -can either enter the lacteal and are carried away in the lymph or enter the blood capillaries in the villi.

Answer 54

-glucose cannot pass through the plasma membrane by simple diffusion because it is hydrophilic. -sodium-glucose co-transporter proteins in the microvilli transfer a sodium ion and a glucose molecule together from the intestinal lumen to the cytoplasm of the epithelium cells. This type of facilitated diffusion is passive but it depends on the concentration gradient of sodium ions created by active transport. -glucose channels allow the glucose to move by facilitated diffusion from the cytoplasm to the interstitial spaces (in between) inside the villus and on into blood capillaries in the villus.

Answer 55

Source: -saliva -pancreas (secretes into small intestine) Function: -digestion of both forms of starch -any 1,4 bonds in starch molecules can be broken by this enzyme as long as there is a chain of at least four glucose monomers. -amylose -> amylase -> maltose -amylopectin -> amylase -> dextrins Specificity: -because of the specificity of its active site, amylase cannot break 1,6 bonds in amylopectin -fragments of the amyl-pectin molecule containing a 1,6 bond that amylase cannot ingest are called dextrins. -dextrins -> dextrinase -> glucose -maltose -> maltase -> glucose **maltase are fixed to the epithelial lining of the small intestine -maltotriose -> glucosidase -> glucose

Answer 56

Break down the diverse mixture of large carbon compounds in food, to yield ions and smaller compounds that can be absorbed.

Answer 57

A model can be used to represent a part of a living system and to investigate specific aspects of a process.

Answer 58

Dynamic Gastric Model Dialysis tubing made from cellulose

Answer 59

Only model specific aspects of a process, not the whole process. Oversimplified portrayal of the process

Answer 60

Tunica externa: a tough outer layer of connective tissue Tunica media: a thick layer containing smooth muscle and elastic fibres made of the protein elastin Tunica intima: a smooth endothelium forming the lining of the artery

Answer 61

At the end of each heartbeat, the pressure in the arteries falls sufficiently for the stretched elastic fibres to squeeze the blood in the lumen.

Answer 62

Systolic: the peak pressure reached in an artery is called the systolic pressure. Diastolic: the minimum pressure inside the artery.

Answer 63

Cause: -the capillary wall consists of one layer of very thin endothelium cells -coated by a filter-like protein gel -contains pores between the cells Effect: -wall is thus very permeable and allows part of the plasma to leak out and form tissue fluid. -the fluid flows between the cells in a tissue -allowing the cells to absorb useful substances and excrete waste products

Answer 64

-blood flow in veins is assisted by gravity and by pressures exerted on them by other tissues especially skeletal muscles. -veins typically pass between skeletal muscle groups, which facilitate venous blood flow via periodic contractions -when the skeletal muscles contract, they squeeze the vein and cause the blood to flow from the site of compression -contraction makes a muscle shorter and wider so it squeezes on adjacent veins like a pump. -veins typically run parallel to arteries, and a similar effect can be caused by the rhythmic arterial bulge created by a pulse

Answer 65

Fish have a single circulation. -blood is pumped at high pressure to their gills to be oxygenated -after flowing through the gills the blood still has enough pressure to flow directly, but relatively slowly, to other organs of the body and then back to the heart. In contrast, the lungs used by mammals for gas exchange are supplied with blood by a separate circulation. *it is essential that blood flowing to and from the two circulations is not mixed. -the heart is therefore a double pump, delivering blood under different pressures separately to the two circulations.

Answer 66

Refers to the generation and transmission of electrical signals within a muscle or organ, such as the heart, that is initiated by the muscle or organ itself rather than by external input or stimulation. In the case of the heart, myogenic transmission refers to the generation of electrical signals by the pacemaker cells in the sinoatrial (SA) node that initiate the contraction of the heart muscle cells.

Answer 67

The region of the heart with the fastest rate of spontaneous beating is a small group of special muscle cells in the wall of the right atrium, called the sinoatrial node. -these cells have few of the proteins that cause contraction in other muscle cells -but they have extensive membranes -(therefore) the sinoatrial node initiates each heartbeat, because the membranes of its cells are the first to depolarise each cardiac cycle.

Answer 68

During the cardiac cycle, there are four main heart valves that open and close to regulate blood flow. The timing of the opening and closing of these valves can be identified on a graph of pressure changes during the cardiac cycle. Mitral Valve: The mitral valve is located between the left atrium and the left ventricle. It opens during the early part of diastole when the left atrial pressure exceeds the left ventricular pressure. It then closes at the onset of ventricular systole when the left ventricular pressure exceeds the left atrial pressure. Aortic Valve: The aortic valve is located between the left ventricle and the aorta. It opens during ventricular systole when the left ventricular pressure exceeds the aortic pressure. It then closes at the onset of ventricular diastole when the aortic pressure exceeds the left ventricular pressure. Tricuspid Valve: The tricuspid valve is located between the right atrium and the right ventricle. It opens during the early part of diastole when the right atrial pressure exceeds the right ventricular pressure. It then closes at the onset of ventricular systole when the right ventricular pressure exceeds the right atrial pressure. Pulmonary Valve: The pulmonary valve is located between the right ventricle and the pulmonary artery. It opens during ventricular systole when the right ventricular pressure exceeds the pulmonary artery pressure. It then closes at the onset of ventricular diastole when the pulmonary artery pressure exceeds the right ventricular pressure. On a graph of pressure changes during the cardiac cycle, the opening and closing of heart valves can be identified by changes in pressure. The mitral and tricuspid valves open during diastole when the atrial pressure exceeds the ventricular pressure, and close during systole when the ventricular pressure exceeds the atrial pressure. The aortic and pulmonary valves open during systole when the ventricular pressure exceeds the arterial pressure, and close during diastole when the arterial pressure exceeds the ventricular pressure.

Answer 69

Organism (or virus) that causes a disease

Answer 70

6.3 Define the term passive immunity.

Answer 71

When a cut or other injury involving damage to blood vessels occurs: 1) plateletes aggregate at the site forming a temporary plug 2) release the clotting factors that trigger off the clotting process.

Answer 72

The production of antibodies in response to a particular pathogen.

Answer 73

An antigen is a substance or molecule, often found on a cell or virus surface, that causes antibody formation. An antibody is a globular protein which recognises a specific antigen and binds to it as part of an immune response.

Answer 74

Antibodies are large proteins that have two functional regions: -a variable region that binds to a specific antigen -a constant region that helps the body to fight the pathogen in one of a number of ways (makes a pathogen more recognizable to phagocytes, preventing viruses from docking to host cells so that they cannot enter the cells.)

Answer 75

A chemical that inhibits the growth of microorganisms.

Answer 76

a. antibiotics block/inhibit specific metabolic pathways/cell functions found in bacteria; Accept specific examples of inhibition such as cell protein synthesis, cell wall formation b. viruses must use host/eukaryotic cell metabolism / viruses do not have their own metabolic pathways; C. host/eukaryotic cell metabolism/pathways not blocked/inhibited by antibiotics;

Answer 77

-some strains of bacteria have evolved with genes that confer resistance to antibiotics -some strains of bacteria have multiple resistance -since bacteria divide rapidly this strain of bacteria that has mutliple resistance will quickly grow in number. A bacteria such as this would be hard to treat since multiple antibiotics would be ineffective.

Answer 78

Staphylococcus aureus (MRSA) which has infected the blood or surgical wounds of hospital patients and resists all commonly used antibiotics.

Answer 79

The formation of blood clots in the coronary arties

Answer 80

To supply the heart muscle (cardiac muscle fibres) with oxygen and nutrients

Answer 81

A collection of several diseases or conditions existing together is called a syndrome. When the syndrome of conditions due to HIV is present, the person is said to have acquired immune deficiency syndrome (AIDS)

Answer 82

Present: -initial tests are performed on animals and then on small numbers of healthy humans. -only if a drug passes these tests is it tested on patients with the disease that the drug is intended to treat -the last tests involve very large numbers of patients to test whether the drug is effect in all patients and to check that there are no severe or common side effects Past: -a drug could be tested on human patients after only a very brief period of animal testing -pure samples of a drug were not required and there may have been side effects because of these impurities

Answer 83

a. ventilation rate at rest is reduced; b. maximum ventilation rate (during exercise) increases: c. diaphragm and intercostal muscle strength increase; d. vital capacity may increase/ VO2 max may increase: Do not accept answers relating to cardiac output.

Answer 84

Cartilage is strong but flexible tissue. -keeps the trachea open even when air pressure inside is low or pressure in surrounding tissues is high -help support the trachea while still allowing it to move and flex during breathing. -strengthens the walls of the bronchi

Answer 85

The bronchioles have smooth muscle fibres in their walls, allowing the width of these airways to vary.

Answer 86

-infection in the lungs draw leucytes there -protease is released by leukocytes (white blood cells). -protease breaks down the connective tissue, such as elastin) of the lungs. -results in the destruction of small airways and alveoli. -results in the formation of large air pockets and the breakdown of capillaries. -large air pockets have a much lower surface area to volume ratio than the alveoli which causes insufficient ventilation. -when combined with the reduced blood supply this in turn means inefficient gas exchange and hence low blood oxygen levels.

Answer 87

There is no current cure for emphysema, but treatments are available to relieve symptoms and delay disease progression -bronchodilators are commonly used to relax the bronchiolar muscles and improve airflow. -corticosteroids can reduce the inflammatory response that breaks down the elastic fibres in the alveolar wall: -elastase activity can be blocked by an enzyme inhibitor (a-1-antitrypsin), provided elastase concentrations are not too high -oxygen supplementation will be required in the later stages of the disease to ensure adequate oxygen intake -in certain cases, surgery and alternative medicines have helped to decrease the severity of symptoms

Answer 88

The study of the incidence and causes of disease.

Answer 89

An association has repeatedly been found by epidemiologists between leanness and an increased risk of lung cancer. -among smokers leanness is not significantly associated with an increased risk. -smoking reduces appetite and so is associated with leanness and of course smoking is a cause of lung cancer. In the 1950's epidemiologists observed links between tobacco and cancer. -the correlation spurred additional research -was able to show a direct casual relationship between smoking and cancer.

Answer 90

• Nerve impulses are action potentials propagated along the axons of neurons.

Answer 91

Remember, up to TWO "quality of construction" marks per essay a. nerve impulse reaches the end of the presynaptic neuron; b. (depolarization causes) calcium channels in membrane (to) open; c. calcium diffuses into the presynaptic neuron; d. vesicles of/containing neurotransmitter move to and fuse with presynaptic membrane; e. (neurotransmitter) released (by exocytosis) into synaptic space/cleft; f. (neurotransmitter) diffuses across the space/ synapse; g. (neurotransmitter) attaches to receptors on postsynaptic neuron; h. receptors cause ion channels to open and sodium diffuses into the postsynaptic neuron; i. the postsynaptic neuron membrane is depolarized; j. (depolarization) causes a new action potential; k. (neurotransmitter) on postsynaptic membrane is broken down; I. (neurotransmitter) is reabsorbed into the presynaptic neuron;

Answer 92

The nervous system is involved in receiving information about the environment around us (sensation) and generating responses to that information (motor responses).

Answer 93

Structure: -consists of many layers of phospholipid bilayer. -Schwann cells deposit the myelin by growing round and round the nerve fibre. -there is a gap between the myelin deposited by adjacent Scwann cells (node of Ranvier.) Function: -acts as an insulator so that myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier -forces the action potential to jump from node to node (saltatory conduction) resulting in the impulse moving faster -saltatory conduction also reduces degradation of the impulse (the impulse can travel longer distances than impulse in unmyelinated axons -also reduces energy expenditure over the axon as the quantity of sodium and potassium ions that need to be pumped to restore resting potential is less than that of a un-myelintated axon

Answer 94

-deposit the myelin by growing round and round the nerve fibre -each time they grow around the nerve fibre a double layer of phospholipid bilayer is deposited There may be 20 or more layers when the Schwann cell stops growing.

Answer 95

The potential difference or voltage across the membrane of a neuron that is not transmitting a signal. (caused by an imbalance of positive and negative charges across the membrane)

Answer 96

Action potential: a rapid change in membrane potential (consisting of two phases), with reversal and restoration of the membrane potential as an impulse travels along it Depolarization: a change from negative to positive voltage in the membrane of the neuron Repolarization: a change back from positive to negative voltage in the membrane of the neuron

Answer 97

Cause: some of the potassium from the sodium side of the membrane leak through potassium channel. Consequence: The refractory period after a depolarization prevents propagation of an action potential backwards along the axon.

Answer 98

Cause: local currents reduce the concentration gradient in the part of the neuron that has not yet polarized. This makes the membrane potential rise from the resting potential of -70mV to about -50mV Effect: sodium channels in the axon membrane are voltage-gated and open when a membrane potential of -50mV is reached which is therefore known as the threshold potential. (The opening of the sodium channels causes depolorization.)

Answer 99

Synapse: a junction between neuron, and neuron and receptor or effector cells Synaptic cleft: a fluid-filled gap which separates pre-synaptic and post-synaptic cells so that electrical impulses cannot pass across. Effector: muscles and glands which carry out a response to a stimulus Neurotransmitter: (they are) chemicals that send signals across synapses

Answer 100

The opening of some sodium channels and the inward diffusion of sodium ions increases the membrane potential causing more sodium channels to open so there is a positive feedback effect.

Answer 101

At a synapse, the amount of neurotransmitter secreted following depolarization of the pre- synaptic membrane. May not be enough to cause the threshold potential to be reached in the post-synaptic membrane. The post-synaptic membrane does not the depolarize. The sodium ions that have entered the post-synaptic neuron are pumped out by sodium potassium Pumps and the post-synaptic membrane returns to the resting potential.

Answer 102

acetvlcholine is used as the neurotransmitter in many synapses -produced in the pre-synaptic neuron by combining choline, absorbed from the diet, with an acetyl group produced during aerobic respiration. -acetylcholine is loaded into vesicles and then released into the synaptic cleft during synaptic transmission. -receptors of acetylcholine in the post-synaptic membrane have a binding site to which acetylcholine will bind. -acetylcholine only remains bound to the receptor for a short time, during which only one action potential is initiated in the post-synaptic neuron. This is because the enzyme acetylcholinesterase is present in the synaptic cleft and rapidly breaks acetylcholine down into choline and acetate. -choline is reabsorbed into the pre-synaptic neuron, where it is converted back into active neurotransmitter by recombining it with an acetyl group.

Answer 103

A synapse which uses acetylcholine as its neurotransmitter.

Answer 104

A much greater proportion of synapses in the central nervous system are cholinergic in insects than in mammals

Answer 105

Neonicotinoids bind much less strongly to acetylcholine receptors in mammals than insects

Answer 106

Structure: chemical structure is unusual because the thyroxin molecules contains four atoms of iodine Function: regulates the body's metabolic rate

Answer 107

-lack of energy and feeling tired all the time -forgetfulness and depression -weight gain despite loss of appetite as less glucose and fat are being broken down to release energy be cell respiration -feeling cold all the time because less heat is being generated -constipation because contractions of muscle in the wall of the gut slow down -impaired brain development in children

Answer 108

Leptin is a protein hormone.

Answer 109

-breeding experiments showed that obese mice had two copies of a recessive allel, ob. -earlier it was shown that the wild-type allele of this gene supported the synthesis of a new hormone that was named leptin. -adipose cells in mice that have two recessive ob alleles cannot produce leptin. -when ob/ob mice were injected with leptin their appetite declined, energy expenditure increased and body mass dropped by 30% in a month.

Answer 110

The rhythms in behaviour which fit the 24-hour cycle that humans are adapted to live in

Answer 111

-enlargement of the penis -growth of public hair -deepening of the voice due to growth of the larynx

Answer 112

At first estrogen and progesterone are secreted by the mother's ovaries and later by the placenta.

Answer 113

-enlargement of the breasts -growth of public and underarm hair.

Answer 114

-FSH and LH protein hormones produced by the pituitary gland -bind to FSH and LH receptors in the membranes of follicle cells -estrogen and progesterone are ovarian hormones -produced by the wall of the follicle and corpus luteum -they are absorbed by many cells in the female body (where they influence gene expression and therefore development)

Answer 115

progesterone: -rises at the start of the luteal phase; -promotes thickening and maintenance of the endometrium (lining of the uterus) estrogen: -rises to a peak towards the end of the follicular phase; -stimulates repair of the endometrium and an increase in FSH receptors on ovary cells FSH: -starts to rise towards the end of the cycle (day 28); -stimulates the development of follicles -stimulate the production of estrogen by the follicle wall LH: -rises to a sudden peak towards the end of the follicular phase; -stimulates completion of meiosis in the oocyte and thinning of the follicular wall, so that ovulation can occur. -after ovulation, it stimulates the development of the remaining part of the Graafian follicle into the corpus luteum -(by causing an increase in the number of follicle cells) -increasing follicle cells secrete estrogen (this is an example of positive feedback) and progesterone

Answer 116

a. anterior pituitary/hypophysis secretes FSH which stimulates ovary for follicles to develop b. follicles secrete estrogen c. estrogen stimulates more FSH receptors on follicle cells so respond more to FSH d. increased estrogen results in positive feedback on «anterior» pituitary [XYSW1] e. estrogen stimulates LH secretion f. estrogen promotes development of endometrium/uterine lining g. LH levels increase and cause ovulation h. H results in negative feedback on follicle cells/estrogen production i. LH causes follicle to develop into corpus luteumORfollicle cells produce more progesterone j. progesterone thickens the uterus lining k. high progesterone results in negative feedback on pituitary/prevents FSH/LH secretion I. progesterone levels drop and allow FSH secretion m. falling progesterone leads to menstruation/ degradation of uterine lining Award [5 max] if no reference to feedback is made

Answer 117

Type I diabetes: -testing the blood glucose concentration regularly and injecting insulin when it is too high or likely to become too high -injections are often done before a meal to prevent a peak of blood glucose as the food is digested and absorbed Type II diabetes: -treated by adjusting the diet to reduce the peaks and troughs of blood glucose. -small amounts of food should be eaten frequently rather than infrequent large meals. -foods with high sugar content should be avoided. -starchy food should only be eaten if it has a low glycemic index, indicating that it is digested slowly. -high-fibre foods should be included to slow the digestion of other foods. -strenuous exercise and weight loss are beneficial as they improve insulin uptake and action.

Answer 118

-73 obese volunteers injected themselves either with one of several leptin doses or with a placebo. -a double blind procedure was used -the leptin injections induced skin irritation and swelling and only 47 patients completed the trial -the eight patients receiving the highest dose lost 7.1 kg of body mass on average compared with a loss of 1.3 kg in the 12 volunteers who were injecting the placebo. -however, in the group receiving the highest dose the results varied very widely from a loss of 15 kg to a gain of 5 kg -any body mass lost during the trial was usually regained rapidly afterwards.

Answer 119

-a very small proportion of cases of obesity in humans are due to mutations in the genes for letpin synthesis or its various receptors on target cells. -leptin reduces food intake and body weight. -obese patients are desensitised to the process and effects of leptin.

Answer 120

-difficulty in remaining awake during daylight hours -difficulty sleeping through the night -fatigue -irritability -headaches -indigestion.

Answer 121

When fertilization occurs outside the body in carefully controlled laboratory conditions.

Answer 122

Testis: -responsible for the production of sperm and testosterone (male sex hormone) Epididymis: -site where sperm matures and develops the ability to be motile (i.e. 'swim') - mature sperm is stored here until ejaculation Vas Deferens: -long tube which conducts sperm from the testes to the prostate gland (which connects to the urethra) during ejaculation Seminal Vesicle: -secretes fluid containing fructose (to nourish sperm), mucus (to protect sperm) and prostaglandin (triggers uterine contractions) Prostate Gland: -secretes an alkaline fluid to neutralise vaginal acids (necessary to maintain sperm viability) Urethra: -conducts sperm / semen from the prostate gland to the outside of the body via the penis (also used to convey urine)

Answer 123

Ovary: -ovary is where oocytes mature prior to release (ovulation) - it also responsible for estrogen and progesterone secretion Fimbria: -fimbria (plural: fimbriae) are a fringe of tissue adjacent to an ovary that sweep an oocyte into the oviduct Oviduct: -oviduct (or fallopian tube) transports the oocyte to the uterus - it is also typically where fertilisation OCCUrS Uterus: -uterus is the organ where a fertilised egg will implant and develop (becoming an embryo) Endometrium -mucous membrane lining of the uterus, it thickens in preparation for implantation or is otherwise lost (via menstruation) Vagina -passage leading to the uterus by which the penis can enter (uterus protected by a muscular opening called the cervix)

Answer 124

-he was unable to detect a growing embryo until approximately 6 - 7 weeks after mating had occurred -because viable microscopes for such investigations were not invented until 17 years after the death of William Harvey

Answer 125

A. «immumoglobulins are/function as» antibodies b. variety of binding sites / variable regions for binding C. specific to antigens on bacteria/ viruses/ pathogens d. constant region aids destruction of the bacteria/virus/pathogen e. attracts phagocytes/macrophages to engulf pathogen f. bursting pathogen cells/agglutination/ neutralizing toxins/other example of the action of antibodies Award marks for an annotated diagram.

Answer 126

a. clotting factors «are proteins» that initiate the clotting cascade/process b. fibrin «is a protein that» permits blood clottingORallows the formation of a clot C. «the protease» thrombin converts fibrinogen to fibrin OWTTE d. fibrin forms a mesh/clot that prevents the entry of pathogen/antigen into the blood e. antibodies are «specific» proteins that lymphocytes make f. each antibody corresponds to a specific pathogen/antigenORantibodies are specific «to certain pathogens/antigens» g. antibodies create specific immunity h. plasma cells produce large amounts of «specific» antibodiesORmemory cells retain the ability to produce «specific» antibodies I. immunoglobulins are antibodies against pathogens j. enzymes in phagocytic white blood cells may digest pathogens Accept annotated diagrams of the process.

Answer 127

a. double circulation / pulmonary and systemic circulations b. heart is a double pump / heart has separate pumps for lungs and other systems / left and right sides of heart are separate / no hole in heart (after birth) c. deoxygenated blood pumped to the lungs and oxygenated to other organs/tissues/whole body (apart from lungs) d. each side of the heart has an atrium and a ventricle e. left ventricle/side pumps blood to the systems/ tissues and right ventricle/side pumps blood to the lungs f. left atrium receives blood from the lungs and right atrium receives blood from systems/tissues g. left ventricle pumps blood via the aorta and right ventricle pumps blood via the pulmonary artery h. left atrium receives blood via the pulmonary vein and right atrium receives blood via the vena cava i. lungs require lower pressure blood / high pressure blood would damage lungs J. high pressure required to pump blood to all systems/tissues apart from lungs k. pressure of blood returning from lungs not high enough to continue to tissues / blood has to be pumped again after returning from lungs I. oxygenated blood and deoxygenated blood kept separate / all tissues receive blood with high oxygen content/saturation Points may be earned using an annotated diagram. enough to continue to tissues / blood has to be pumped again after returning from lungs

Answer 128

a. molecules move by diffusion / move down a concentration gradient b. nutrients move into tissues c. gas exchange / Oxygen and carbon dioxide exchange between tissues and blood/capillaries d. (nitrogenous) wastes/excess water move from cells/tissues into blood/capillaries e. hormones leave capillaries in target tissues/to attach to receptors on cells / (endocrine) organs/ gland tissues release hormones into the bloodstream

Answer 129

Nerve impulse is an action potential that stimulates a (wave of) depolarization along the membrane/axon:

Answer 130

Organs that secrete and release particular chemical substances

Answer 131

a. glucose in urine; b. high blood glucose; c. frequent urination / dehydration/excess thirst; d. constant hunger; e. weight loss; f. tiredness:

Answer 132

a. reduce blood glucose levels as target/ body/ muscle cells less sensitive to insulin / not enough insulin produced; b. reduce intake of (saturated) fats, to reduce weight; c. reduce the intake of sugar/simple carbohydrates, causes rapid increase in blood glucose concentration; d. eat more high fibre foods, satisfy appetite, but cannot be broken down; e. regular/many small meals, to avoid (rapid) rise in glucose after a big meal; f. eat complex carbohydrates/carbohydrates with a low glycemic index, digested and absorbed more slowly; To award the mark, answers require dietary recommendations with a reason. Do not accept comments about increased exercise.

Answer 133

a. (high blood glucose levels) detected by pancreas islet cells/beta cells; b. insulin secreted in response (to high blood glucose/glucose above threshold level); c. insulin stimulates cells to absorb glucose; d. glucose used in cell respiration (rather than lipids); e. glucose converted to glycogen (in liver/muscle cells); f. glucose converted to fatty acids/triglycerides/ fat; g. negative feedback process;

Answer 134

a. normal body core temperature constant/36.5 to 37.5°C; (accept single values within this range) b. regulated by negative feedback/homeostatic mechanisms; c. hypothalamus is the centre of thermoregulation; d. hypothalamus sends impulses to the body to increase/decrease temperatures; e. release of sweat (by sweat glands in the skin) if skin temperature rises; f. evaporation of water cools the body; (concept of evaporation must be mentioned) g. heat is transferred by blood; h. transfer of heat from body core in blood to surface: i. if temperature rises, increased flow of blood/heat to the skin/ vasodilation of skin blood vessels/arterioles: (do not accept veins, arteries or capillaries) j. if temperature drops, decreased flow of blood/ heat to the skin/vasoconstriction of skin blood vessels/arterioles; (do not accept veins, arteries or capillaries) k. shivering increases heat production (in muscles); I. example of one behavioural mechanism; (eg reducing activity (to lower body temperature) / reducing exposed surfaces (to reduce heat loss)

Answer 135

Gas exchange: the primary function of the lungs involving the transfer of oxygen from inhaled air into the blood and the transfer of carbon dioxide from the blood into the exhaled air. Ventilation: the exchange of air between the lungs and the atmosphere so that oxygen can be exchanged for carbon dioxide in the alveoli (the tiny air sacs in the lungs).

Answer 136

Alveolus as an oval with scalloped edges maximizes surface area for gas exchange. -alveolus wall is a single layer of Type 1 pneumocytes- minimizes distance gases have to travel between the blood in the capillary and the air in the alveolus -lumen of alveolus- volume of air for gas exchange. -surfactant produced by Type I pneumocytes- reduces surface tension and prevents collapse of alveolus when air is exhaled. -bronchial tube ending at alveolus- tube for transport of air into and out of the alveolus. -capillary surrounding outside of the alveolus- minimizes distance gases have to travel between the blood in the capillary and the air in the alveolus. -capillary wall is a single cell thick- minimizes distance gases have to travel between the blood in the capillary and the air in the alveolus.

Answer 137

-must occur so that cells have oxygen for performing aerobic respiration. -oxygen is the final electron acceptor in the oxidation of glucose during cellular respiration. -without oxygen, aerobic respiration will stop -additionally, the carbon dioxide waste product of the respiration must leave the cells. -it is very dangerous if carbon dioxide builds up in the body, so blood carries the carbon dioxide to the lungs where it is released into the air with exhalation.

Answer 138

-produce a pulmonary surfactant that is continuously released by exocytosis. -re-inflation of the alveoli following exhalation is made easier by the surfactant -which reduces surface tension in the thin fluid coating of the alveoli -fluid secreted by Type I pneumocytes facilitates the transfer of gases between blood and alveolar air. -the gases dissolve in the moist fluid, helping them to pass across the alveoli surface

Answer 139

inspiration: The process that causes air to enter the lungs. expiration: The process that causes air to leave the lungs.

Answer 140

-each rib is connected to the rib below it by both external and internal intercostal muscles. -the external intercostal muscles are located on the outer surface of the ribs and are positioned at a diagonal in between each rib. -the external intercostal muscles are responsible for forced and quiet inhalation. -contraction of the external intercostal muscles elevates the ribs and spreads them apart, resulting in the inhalation of air from the atmosphere.

Answer 141

tidal volume: volume of air taken in with each inhalation/out with each exhalation; ventilation rate: number of inhalations/ exhalations/breaths per minute;

Answer 142

-both ventilation rate and tidal volume increase with increased intensity of exercise. -exercise increases aerobic respiration; -CO2 concentration in blood increases, leading to drop in pH of blood detected / blood more acidic; -chemoreceptors detect the change in blood pH and send nerve impulses to the breathing center of the brain. -breathing centres (in the medulla) send impulses to diaphragm and intercostal muscles; -which will contract more frequently (increasing ventilation rate) and with more force (increasing tidal volume). -increase rate of contraction, hence increase in ventilation rate increases oxygen uptake/ decreases CO2; -during exercise the rate of cellular respiration increases and as a result more carbon dioxide is produced by the cells.

Answer 143

To award full marks, discussion must contain both pro and con considerations. pros/positive considerations: [3 max]chance for infertile couples to have children; decision to have children is clearly a conscious one due to difficulty of becoming pregnant; genetic screening of embryos could decrease suffering from genetic diseases;spare embryos can safely be stored for future pregnancies/used for stem cell research; cons/negative considerations: [3 max]IVF is expensive and might not be equally accessible:success rate is low therefore it is stressful for the couple;it is not natural/cultural/ religious objections;could lead to eugenics/ gender choice;could lead to (unwanted) multiple pregnancies with associated risks;production and storage of unused embryos / associated legal issues / extra embryos may be used for (stem cell) research;inherited forms of infertility might be passed on to children; Accept any other reasonable answers.

Answer 144

The heart is a muscle that can contract and relax to pump blood throughout the body. The heart's contraction is initiated by electrical signals that are generated by specialized cells in the heart, which are called pacemaker cells. The electrical signals are then transmitted through the heart, causing the muscle cells to contract and relax in a coordinated manner. There are two primary modes of transmission of the electrical signals in the heart: myogenic transmission and neural transmission. Myogenic Transmission: Myogenic transmission refers to the ability of the heart muscle cells to generate their own electrical signals, without the need for input from the nervous system. This intrinsic property of the heart muscle cells is due to the presence of pacemaker cells, which have the ability to spontaneously generate electrical signals. The pacemaker cells are located in the sinoatrial (SA) node of the heart, and they generate electrical impulses that spread throughout the atria, causing them to contract. Neural Transmission: Neural transmission refers to the transmission of electrical signals through nerves that innervate the heart. The nerves that innervate the heart are part of the autonomic nervous system and are divided into two branches: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system stimulates the heart to beat faster and stronger, while the parasympathetic nervous system slows the heart rate down. In summary, myogenic transmission refers to the intrinsic ability of the heart muscle cells to generate their own electrical signals, while neural transmission refers to the transmission of electrical signals through nerves that innervate the heart.

Answer 145

Refers to the transfer of information or signals from one neuron or group of neurons to another through specialized structures called synapses. In the case of the heart, neural transmission refers to the transmission of signals from the autonomic nervous system to the heart, which can modify the rate and force of the heart's contractions. The autonomic nervous system consists of two branches, the sympathetic and parasympathetic nervous systems, which have opposing effects on heart rate and function.

Bio 6 Flashcards

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