2020 exam revision Flashcards
(153 cards)
1
Q
function of cerebrum:
A
includes association area (intellectual and emotional processes), motor area (controls muscular movements) and sensory area (interprets impulses), mental activities such as thinking, learning, memory, intelligence.
2
Q
function of thalamus:
A
relays motor and sensory signals to cerebral cortex
3
Q
function of hypothalamus:
A
releases hormones, regulates body temp
4
Q
function of pons varolii:
A
controls breathing and communication between parts of the brain.
5
Q
functions of medulla oblongata:
A
controls autonomic functions eg breathing, digestion, heart and blood vessel function.
6
Q
functions of cerebellum:
A
receives info from sensory systems, spinal cord and regulates motor movements. exercises control over balance, posture and fine coordination/ muscle movement.
7
Q
function of ventricles:
A
produces cerebrospinal fluid + transports it
8
Q
functions of corpus callosum:
A
thick band of nerve fibres that divide cerebral cortex lobes into left + right hemispheres, connects left + right sides of the brain allowing for communication.
9
Q
function of midbrain:
A
serves in motor movements eg eye movements and visual processing.
10
Q
function of meninges:
A
protects the CNS
11
Q
function of spinal cord:
A
relays messages from brain to body, to perform an action and to pass along messages from sensory receptors to the brain/coordinate reflexes that are managed by spinal cord alone.
12
Q
structure of cerebrum:
A
- outer surface of grey matter
- 2-4mm thick is cerebral cortex
- below cortex is white matter
- inside grey matter is basal ganglia
- convolutions separated by fissures
13
Q
structure of corpus callosum:
A
-wide band of nerve fibres under cerebrum
14
Q
structure of cerebellum:
A
- surface folded into parallel ridges
- outer part is grey matter, inside is white matter that branches to all parts of cerebellum.
15
Q
structure of medulla oblongata:
A
- continuation of the spinal cord
- 3cm long
16
Q
structure of spinal cord:
A
-cylindrical extending from foramen magnum to the 2nd lumbar vertebra
17
Q
what are the 3 types of nerve cells + examples
A
- unipolar (sensory neurons)
- bipolar (sense organs eg eyes)
- multipolar (connector and motor neurons)
18
Q
dendrite:
A
where a nerve impulse enters the cell body
19
Q
cell body:
A
contains nucleus, is the site of many chemical reactions
20
Q
cell body nucleus:
A
controls the size, shape and function of the cell
21
Q
axon:
A
a very long extension of the cell body, where the nerve impulse passes through the cell
22
Q
shwann cell:
A
surrounds and insulates the axon
23
Q
neurilemma:
A
the outside membrane of the shwann cell, produces a fatty substance called myelin
24
Q
myelin:
A
insulates axon
25
axon termination:
the end of an axon where the nerve impulse can be passed on to the next nerve cell
26
node of ranvier:
a gap between successive shwann cells, it allows for the movement of transmission chemicals.
27
what is a reflex?
a rapid, automatic response to a stimulus
28
what are the 9 types of reflexes?
```
involuntary
rapid
innate
stereotypical
protective
visceral
monosynaptic
polysynaptic
learned
```
29
what is a monosynaptic reflex?
when a sensory neutron connects directly to a motor neurone (only one synapse) eg knee jerk reflex
30
what is a polysynaptic reflex?
when a sensory neuron connects to a connector neuron, then to a motor neuron (2 synapses) eg withdrawal reflex
31
what are the 3 layers of the meninges?
3. dura layer= toughest layer, helps to protect brain
2. arachnoid layer= filled with a web of collagen fibres, contains cerebrospinal fluid
1. pia matter= softest layer, attached to surface of the brain, contains blood capillaries that nourish tissue
32
function of cerebrospinal fluid?
delivers nutrients, acts as a shock absorber, expels waste
33
what is a synapse?
the gap between neurons, essential so we can create specific nerve pathways around our body.
34
what composes the CNS?
brain
| spinal cord
35
what composes of the peripheral nervous system?
somatic NS
| autonomic NS
36
what composes of the autonomic NS?
- cannot be controlled-
| - sympathetic and parasympathetic NS
37
what composes of the somatic NS?
- cranial nerves
| - spinal nerves
38
what is visceral reflex?
-automatic response within the body organ (heart rate, digestion)
39
describe the transmission of a nerve impulse across a synapse.
- nerve impulse is the movement of na+ ions
- na+ causes calcium channels to open in axon terminal membrane
- calcium ions enter axon terminal
- these calcium ions cause the vesicles containing acetylcholine to rupture, causing acetylcholine to fill the synapse
- receptor proteins on the dendrite membrane detect this, causing na+ channels to open
- these na+ ions move to the dendrite.
40
what is a synapse?
-the gap between neutrons, is essential so that we can create specific nerve pathway.
41
difference in speeds between axons?
- unmyelinated = 140ms-1,
| - myelinated= 2ms-1
42
describe the transmission of a nerve impulse along an unmyelinated axon:
- the na+/k+ pump maintains resting membrane potential at -70 mV
- large negatively charged organic molecules make the inside of the axon negatively charged
- the nerve impulse itself is a flow of na+ ions from the cell body along the axon to the axon terminal
- as na+ ions enter axon, membrane potential is raised from -70mV to -55mV
- at -55mV, Na+ gates open, more Na+ ions rush through
- membrane potential is raised to +30mV, then the na+ gates close and the K+ open. K+ ions rush out of axon.
- the leaving K+ ions cause the membrane potential to fall to -70mV, K+ gate closes.
- the sodium/potassium pump switches back on and maintains resting membrane potential.
43
describe the transmission of a nerve impulse across a myelinated axon:
Is faster because the impulse jumps from node of ranvier to node of ranvier
44
what is a steady state control system?
```
maintains a system or function at optimum level by the following means
Stimulus
Receptor
Modulator
Effector
Response
Feedback
```
45
what is saltatory propagation?
when the nerve impulse appears to jump from one node of ranvier to the next (transmission along a myelinated axon)
46
what are thermorecpetors?
- found in the skin
- inform the brain of changes to outdoor temperatures
- Internal thermoreceptors found in hypothalamus (detecting temp of blood flow through the brain)
47
what is a nephron?
-functional units of the kidney, carrying out the roles of excretion and water regulation.
48
what does ADH do in terms of kidneys?
- controls the permeability of the walls of distal convoluted tubule.
- when concentration of ADH in plasma is high, tubules are permeable to water-leaving tubules and joining surrounding capillaries.
- when ADH conc in plasma is low, tubules are not very permeable to water, and little water is reabsorbed by capillaries.
49
what is the difference between protein, amine and steroid hormones?
- protein and amine hormones bind to receptors on the membrane of the cell
- steroid hormones bind to receptors inside the cell
50
what hormones does the anterior lobe produce? (6)
- FSH
- LH
- prolactin
- ACTH
- TSH
- growth hormone
51
what hormones does the posterior lobe produce?
- oxytocin
| - ADH
52
role of the thyroid gland:
- releases thyroxin upon recieving stimulus of TSH from anterior
- thyroxine controls body metabolism by releasing more energy for reactions.
53
role of parathyroid glands:
-secrete the parathyroid hormone (parathormone) which controls calcium and phosphate in blood.
54
role of the thymus:
-secretes thymosins, which influence maturation of disease fighting cells (T lymphocytes)
55
role of the adrenal glands
- secrete adrenaline and noradrenaline (fight or flight)
| - secretes aldosterone (reduces sodium and increases potassium in urine) and cortisol (promotes normal metabolism)
56
role of the pancreas (islets of langerhans):
- releases insulin (reduces amount of glucose in blood, in the liver causes conversion of glucose to glycogen and fat, in skeletal muscles causes conversion of glucose to glycogen and acts as storage in fat tissue)
- releases glucagon, (works to increase blood glucose, by promoting breakdown of glycogen to glucose in the liver)
57
what is grey matter (when referring to nerve cells)
-consists of nerve cell bodies and unmyelinated fibres
58
what is white matter (when referring to nerve cells)
-consist of myelinated fibres (lipid covered)
59
what is the ANS?
- controls bodies internal environment
- operates without conscious control, regulated by nerve cells in medulla oblongata, hypothalamus and cerebral cortex
- controls blood pressure, temperature, digestion, defecation, urination
60
difference between autonomic and somatic NS?
- autonomic is involuntary muscles and glands, somatic is voluntary skeletal muscles
- autonomic is response to homeostasis, somatic is response to external forces
61
what are the 3 types of reabsorption in ultrafiltration?
- facultative reabsorption
- selective reabsorption
- active secretion
62
what is facultative reabsorption ?
reabsorption of water in the late distal convoluted tubule and. collecting duct under the control of antidiuretic hormone (ADH).
63
what is selective reabsorption?
Selective reabsorption is the process whereby certain molecules, after being filtered out of the capillaries along with nitrogenous waste products and water in the glomerulus, are reabsorbed from the filtrate as they pass through the nephron. Selective reabsorbtion occurs in the PCT.
64
what is active secretion?
when substances are moved from the capillaries into the nephron at the PCT and DCT.
65
describe 3 way antibodies can act on pathogens?
- combine with foreign enzymes or bacterial toxins
- bind to surface of viruses and prevent them from entering other cells
- coat bacteria so that they are more likely to be consumed by phagocytes.
66
describe the bodies external defences? (6)
- acts as protective barrier, at openings there is extra protection and good bacteria
- bacteria occupies the skin, blocking foreign invaders
- sebum is secreted which kills pathogenic bacteria
- sweat contains salts and fatty acids that prevent the growth of microorganisms.
- hairs found in nose and ears paired with mucous trap 90% of particles
- acidic secretions from stomach and vagina
67
describe the bodies internal defences? (3)
- phagocytes are cells that engulf and digest microorganisms and cell debris
- phagocytosis, leucocytes are able to leave blood caps and migrate through tissues to site of infection. some WBCs secrete substances that destroy bacteria
- macrophages are large phagocytic cells that develop from leucocytes.
68
what is the purpose of the inflammatory response?
1. reduce the spread of pathogens
2. remove damaged tissue and cell debris
3, begin repair of damaged tissue
69
what are the 7 steps of the inflammatory response?
1. histamine, heparin and other substances are released from mast cells when there is a stimulus
2. histamine increases blood flow through area and makes the blood capillaries more permeable so that fluid is filtered from the blood.
3. heparin prevents clotting, a clot of the fluid around the damaged area forms and slows the spread of the pathogen
4. chemicals released from the mast cells attract phagocytes. phagocytosis occurs.
5. the abnormal conditions stimulate pain receptors
6. the filled phagocytes die, paired with the tissue fluid it forms pus
7. new cells are produced via mitosis and repair of the damaged tissue takes place.
70
what is conduction?
heat energy transferred when 2 objects are in direct contact with each other, the heat moves from the hotter object to the cooler one.
71
what is convection?
happens in liquids and gases, when. liquid is heated it will expand, becoming less dense and rise to the top off the surface, same as for gases hence "hot air rises"
72
what is radiation?
when infrared rays remove heat if the temperature outside is lower than internal body temp.
73
what does aldosterone do
comes from the adrenal cortex, targets the nephrons, causes Na+ molecules to enter the blood capillary and as a direct result water will follow via osmosis.
74
what is deamination?
when excess amino acids that cannot be stored in the body are broken down in the liver.
-amino acid -----> amino group (-NH2) + carbohydrate
75
what is a difference between the sympathetic and parasympathetic NS?
- SYMPATHETIC NS; increases breakdown of glycogen and release of glucose (glycogenolysis)
- PARASYMPATHETIC NS; increases uptake of glucose and synthesis of glycogen (glycogenesis)
76
what are the 3 main types of cell fluid
intracellular; fluid inside the cell eg cytosol
extracellular; fluid outside cells
plasma; blood fluid
intercellular; fluid between cells eg lymph, synovial, cerebrospinal
77
what does ACTH do
-stimulates the adrenal glands, more specifically the adrenal cortex to produce cortisol and aldosterone.
78
describe antibody-mediated immunity
1. B cell is sensitised, enlarges and divides, farming clones.
2. most new B cells become plasma cells, which then secrete antibodies, some become memory cells
3. antibodies combine with antigens and form the antigen-antibody-complex, preventing the antigen from reproducing and binding to receptors on cells.
79
describe cell-mediated immunity
1. t-cells in lymphoid tissue, one type becomes sensitised, enlarges and divides, forming clones.
2. most T-cells become killer T-cells, or helper T-cells, and migrate to antigens. some become memory cells
3. killer T-cells attack to and kill antigens, helper T-cells secrete chemicals that attract macrophages and a substance that densities more lymphocytes
4. supressor T-cells release substances that inhibit T & B cell activity.
80
what are the 7 mechanisms of evolution?
1. mutations
2. natural selection
3. random genetic drift
4. founder effect
5. migration
6. barriers to gene flow
7. genetic diseases
81
what are the 6 types of chromosomal mutations?
1. DELETION: when part of a chromosome is lost
2. DUPLICATION: a section of chromosome occurs twice- part of a cromatid (copied chromosome) breaks off and joins onto the wrong chromosome
3. TRISOMY 21 (Down syndrome)
4. INVERSION: a piece of chromosome breaks from the middle of a chromosome but when it reattaches its the wrong way
5. TRANSLOCATION: part of a chromosome breaks off and joins to the wrong chromosome
6. NON-DISJUNCTION/ANEUPLOIDY: when the eggs and sperm are formed sometimes chromatid pairs do not move to seperate cells, instead one cell receives both chromatids and will have an extra chromosome, whilst the other cell is one chromosome short
82
state the 3 keys to natural selection:
1. variation
2. birth rate
3. natures balance
83
what is random genetic drift?
- also known as the Sewall-Wright effect
- can only happen in small populations
- eg Australian aborigines on Bentinck island all have the allele for 1B (blood type B)- whereas mainland has blood type 1A and 1B, this is due to Mornington island aborigines hopping to the mainland thousands of years ago and the Bentnick not- so when sea levels rose that path to the mainland was lost
- allele frequency changes for no 'real' reason meaning there is no survival advantage.
84
what is the founder effect?
- occurs during the founding/establishing of a new colony
- small group leaves a main land and are not representative of the dominant gene frequencies of the homeland population
- an example of this is the Indonesian island colourblind allele
85
what is migration?
- emigration is when a population leaves an area, immigration is when people enter a new area
- when a population loses or gains new variations in a population then there will be an allele frequency change.
86
what is barriers to gene flow?
there are 2 main types of barriers- socio-cultural and geographical.
1. GEOGRAPHICAL BARRIERS: oceans, mountains, deserts, rivers
2. SOCIO-CULTURAL BARRIERS: language- Basque people. religion (jewish-orthodox)
- these populations are isolated, stopping the inter-mingling between populations resulting in barriers to gene flow.
- jewish orthodox and dunkers cannot marry out of their faith group
- economic status, social position and educational background are also barriers
87
what are genetic diseases?
1. Tay-sachs
2. sickle cell anaemia
- tay sachs occurs when a mutated gene replaces the normal gene that breaks down lipids via an enzyme (protein coded by normal gene)
- provides immunity to tuberculosis if a person is a carrier- popular in the ashkenazi jew population
- sickle cell anaemia provides resistance against malaria
88
what is a mutation?
a sudden, permanent change in chromosomal DNA
89
what are the 4 types of mutation?
1. gene mutations- change DNA of a single gene
2. chromosome mutations- change in all or part of a chromosome
3. somatic mutation- a mutation in body cells, only affects the individual within the mutation
4. germline (germinal)- a mutation in the gametes, passed on to offspring and subsequent generations (eg PKU)
90
what is a mutagen?
a mutagen can speed up or causes mutation and include:
1. CHEMICALS; thalidomide, mustard gas, antibiotics
2. IRRIDATION: x-rays, UV rays, gamma rays
3. TEMPERATURE; optimum temp for sperm production is a couple degrees below body temp (35-36)
4. SPONTANEOUS; no known reason
91
what is the evidence for evolution? (6)
1. fossils
2. comparative studies of embryology
3. comparative study of homologous organs
4. comparative study of DNA
5. comparative study of proteins
6. vestigal organs
92
discuss comparative study of embryology:
- the 5 vertebrae groups (fish, mammal, reptiles, birds and humans) all have similar structure during embryonic development suggesting a common ancestor
- similar brain development
- 2 chambered heart
- gill slits
- tail
93
discuss vestigial organs;
- appendix, abdominal muscles- the remains of an organ that was once used but no longer has a function
- this proves evolution as the human population has changed over time as our common ancestors once used these organs.
94
discuss homologous organs;
- same bones found in birds, bats, horses, humans and whales suggest a common ancestor
- all have the same bones just slightly changed to better suit a species locomotion
95
discuss comparative studies of protein:
-there are 20 different amino acids, all form in sequences to code for proteins. when comparing human and chimpanzees, these sequences are identical, but point mutations will occur as species differ
96
discuss comparative DNA
-proves evolution as all organisms on earth share the same genetic coding (sugar phosphate, C+G, A+T)
97
list relative dating techniques:
- stratigraphy
- index fossils
- fluorine analysis
98
discuss stratigraphy:
- refers to the composition of rock layers and the fossils found in between them- the closer a layer is to the surface- the younger the fossil
- LIMITING FACTORS: earth movements can change the direction of compositions
- core samples must come from the same area
99
discuss index fossils:
1. have to be widespread
| 2. life must be short-lived (only ever found in one layer of sedimentary rock 100-1000 years)
100
discuss fluorine analysis:
- groundwater contains fluoride ions
- PETRIFICATION AND PERMINERALISATION where bone materials are replaced by minerals
- therefor the more fluoride ppm content found in fossils- the older it is
- LIMITING FACTORS: we cannot compare bones from different areas as different soils have different groundwater concentrations
101
list the absolute dating techniques:
- radio-carbon dating
- potassium-argon dating
- dendrochronology
102
discuss radio-carbon dating:
- the earth is continually bombarded by cosmic rays, when these rays hit the atmosphere, it causes nitrogen to be changed in Carbon 14
- Carbon 14 is radioactive, its half life is the time taken for 1/2 of Carbon 14 to turn into another substance- this take 5,730 years
- the carbon 14 in atmosphere stays constant due to cosmic rays
- every living thing contains 14C in the ratio of 1:10^12 due to food chains
- we can measure the amount of 14C in an organism through mass, ratio and radiation
- LIMITING FACTORS: after 50,000-60,000 years there is not enough 14C to measure- meaning a fossil has to be younger than 60,000 years old to be dated
- can only date living organisms
103
discuss potassium argon dating:
- the time taken for potassium 40(solid) to turn into argon 40(gas)
- 40K has a half life of 1.3 billion years
- LIMITING FACTORS: can only be used in volcanic areas where 40Ar is 0% and 40K is 100%
- if it is hot enough to melt rock, no living organisms can be found in the layers of of rocks- its between layers where organisms can be dated
- fossils have to be over than 100,000 years due to large half-life
104
discuss dendrochronology:
- tree ring dating
- each ring on a tree indicates one year of growth
- the thickness and size of the ring is reflective of the weather patterns in that year
- artefacts can be dated using this technique
105
Contrast six features of the torso and body limbs between the genus of Homo and Australopithecus
```
AUSTRALOPITHECUS:
1. narrow hips (pelvis)
2. femurs more parallel, more smaller carrying angle
3. arms are linger than legs
4. vertebrae less wedge shaped
5. shorter thumb
6. fingers are curved
HOMO
1. broader hips (pelvis)
2. femur slopes in towards knee, larger carrying angle
3. legs are longer than arms
4. vertebrae more wedge shaped
5. longer thumb
6. fingers are straighter
```
106
what are the conditions for fossilisation to take place: (6)
- alkaline rather than acidic soils so that the bones are not dissolved
- rapid burial
- lack of oxygen
- geographically stable location
- area uninterrupted by humans and animals
- water based environment for a quick deposition of sediments
107
discuss the bodies fight or flight responses? (6)
- increased heart rate- pumps more blood around the body so that nutrients are delivered to the muscles
- increase in breathing rate/bronchodilation delivers more oxygen to the blood to be taken to the muscles
- vasodilation in skeletal muscles causes more flow of blood to muscles
- blood glucose levels increase, liver converts glycogen to glucose to produce more energy/ATP
- increase in adrenaline and noradrenaline from adrenal medulla works to prolong responses and increase glucose levels
- sweating due to relaxation of sweat glands and dilation of blood vessels
108
Explain the process of cell replacement therapy in the context of Alzheimer’s disease. (3)
1. stem cells are isolated
2. stem cells are grown and cultured ex-vivo (outside of the organism)
3. cells are reintroduced into damaged area of the brain
109
how can a microorganism gain antibiotic resistance?
1. natural selection
2. some bacteria show antibiotic resistance
3. antibiotics will kill 'normal bacteria' and do not kill resistant bacteria
4. resistant bacteria multiply and grow
110
Explain how comparing nuclear DNA sequences can provide evidence for evolution.
- all species have different DNA sequences/codes
- through the use of hybridisation/ERVS/NON-FUNCTIONAL (JUNK) dna
- the more similar two species dna is the closer related they are vice versa
111
Suggest two reasons why mitochondrial DNA (mtDNA) is best used when comparing individuals within a species.
- mtDNA is inherited from mothers
- lack of recombination
- higher rate of mutations
112
Explain why diabetes sufferers experience constant feelings of thirst.
- osmoreceptors in blood detect increased osmotic pressure
- stimulation of thirst centre makes the person feel thirsty
- this thirsty feeling stimulates the person to drink water
113
Identify and describe two external defence mechanisms of the respiratory tract that would help prevent pathogens from entering the body
- hairs within the nose cavity trap pathogens
- mucous membranes secrete mucous that traps pathogens
- cilia hair like projections cells that line airway trap and usher pathogens towards the throat.
114
Explain the pathway of a spinal reflex. Ensure your answer refers to the neurons involved in the pathway.
1. receptors detect the stimulus
2. sensory neuron conducts nerve impulse/message from receptor to spinal cord
3. information is processed in the CNS / one or more interneurons pass message to motor neurone
4. motor neuron passes impulse/message to the effector
5. effector carries out appropriate response
115
Describe why releasing and inhibiting factors from the hypothalamus are classified as hormones themselves.
- secreted into extracellular fluid (surrounding the hypothalamus)
- travel in the blood
116
what are the 4 types of vaccination
1. dead organisms
2. living attenuated organism
3. toxoids (harmless toxin)
4. sub-unit (fragment of pathogen)
117
describe the defining features of the Australopithecus afarensis? (skull, pelvis, limbs, jaw/teeth)
```
SKULL
-sloped forehead
-projecting face
-prominent brow ridge
-foramen magnum at bottom of skull
JAW/TEETH
-prognathic jaw
-canines longer than other teeth
-diastema present
-molars LARGE
PELVIS
-short and wide like humans but lacked the refinements that enables humans to walk with a striding gait
LIMBS
-short, longer arms than legs
-thick bone around knees and ankles, femur bone slanted inwards slightly
```
118
describe the defining features of the Australopithecus africanus? (skull, pelvis, limbs, jaw/teeth)
SKULL
-more human-like features such as a smaller brow ridge & a slightly arched (rather than flat) forehead area.
-foramen magnum bottom of skull
JAW/TEETH
-smaller canine and incisors
-LARGE molars
-diastema was rare
PELVIS
-fully adapted for walking on two legs but compared with those of modern humans it was less rounded, had a narrower birth canal, & was not specialised for a striding gait.
LIMBS
-ape-like features including slightly curved finger, toe bones & arms that were quite long, although not longer than their legs
119
describe the defining features of the Paranthropus robustus? (skull, pelvis, limbs, jaw/teeth)
SKULL
-flat forehead & a prominent brow ridge above the eyes.
-zygomatic arch
-shorter, flatter faces
-prominent sagittal crest
JAW/TEETH
-all teeth relatively small except for molars
-jaws were large and robust (hence sagittal crest for large jaw muscles)
PELVIS
-built for walking on two legs but without the refinements for the striding gait of humans.
LIMBS
-arms longer than legs
120
describe the defining features of the homo habilis? (skull, pelvis, limbs, jaw/teeth)
SKULL
-expansion of brain results in more rounded skull
-slight forehead
-small, arched brow ridge
JAW/TEETH
-teeth were arranged in a more rounded arc like those of modern humans
-teeth had become smaller & more human-like, although the incisors were still relatively large
LIMBS
-features of the leg & foot bones indicate that this species walked on two legs
-legs were relatively short, providing this species with arm & leg proportions that were relatively
ape-like & similar to those of the australopithecines.
-finger bones are slightly curved
121
describe the defining features of the homo erectus? (skull, pelvis, limbs, jaw/teeth)
SKULL
-face was large with a low, sloping forehead, a massive brow ridge & a broad, flat nose
-skull was broad & long with sharp angles at the rear,
JAW/TEETH
-jaw was large & thick without a pointed chin
-molars slightly smaller
LIMBS
-similar to modern humans just thicker suggesting a more physically demanding lifestyle
122
describe the defining features of the homo neanderthalensis? (skull, pelvis, limbs, jaw/teeth)
SKULL
- skull shape that was long & low, with a rounded brain case
-occipital bun
-thick but rounded brow ridge lay under a relatively flat & receding forehead
JAWS/TEETH
-larger and more robust jaw
-jaw lacked projection of a chin found in sapiens
-teeth were larger than those of modern humans
LIMBS/PELVIS
-limb bones were thick & had large joints which indicates they had strongly muscled arms & legs
-shorter limbs due to cold conditions
-pelvis was wider from side to side than in modern humans & this may have slightly affected their posture
123
describe the defining features of the homo sapiens? (skull, pelvis, limbs, jaw/teeth)
SKULL
-skulls have a short base & a high braincase. Unlike other species of Homo, the skull is broadest at the top.
-back of the skull is rounded & indicates a reduction in neck muscles
-small face with projecting nose
-small brow ridge and tall forehead
JAWS/TEETH
-short jaw=vertical face
-protruding chin
-parabolic shaped jaw
-teeth all small
LIMBS/PELVIS
-limb bones thinner and less robust indicating less muscle mass
-legs longer than arms
-finger and toes straight
-pelvis is narrower from side-to-side & has a deeper bowl-shape from front-to-back
124
Endogenous retroviruses:
ERV are viral sequences that are part of an organism’s genome, Matching ERVs have been found between
similar primate species. the more closely related the primate to humans the more ERVs they have in common, suggesting a common ancestor.
125
describe how natural selection occurs:
1. There is variation in traits. For example, some beetles are green & some are brown. Both excessively reproduce.
2. Selection pressures act on the population. There is a struggle for existence, green beetles tend to get eaten by birds & survive to reproduce less often than brown beetles do.
3. The surviving brown beetles have brown baby beetles because this trait has a survival advantage, this is known as survival of the fittest
4. The brown colour allows the beetle to have more offspring, becoming more common in the population (change in gene pool).
the fittest
126
discuss the process of recombinant dna in reference to vaccines: (6)
1. The gene/segment of DNA for the antigen is isolated by cutting it at a recognition site by the use of a restriction enzyme.
2. The enzyme cuts the DNA on either side of the gene to produce sticky ends.
3. A plasmid (a circular strand of DNA inside a bacterial cell) is removed from a bacterium.
The plasmid is cut with the same type of restriction enzyme to also create complimentary sticky ends.
4. DNA ligase is used to join the sticky end of the isolated gene & the plasmid together.
5. The plasmid is inserted into the bacterial cell.
6. The bacteria are then cloned to produce large amounts of the gene or its product, e.g.
vaccine.
127
what is DNA sequencing ?
DNA sequencing is the determination of the exact order of the base pairs in a segment of DNA.
128
describe gel electrophoresis:
-DNA/protein placed at negative end of gel bed
-An electric current is passed through the gel/ voltage applied across the gel
-The negatively charged DNA/protein move towards positive charge at the opposite end of the tank
-The DNA/protein pieces move through the gel at different speeds/ smaller pieces move faster than large
ones
-Forming bands/bar code representing different segments/ sizes of DNA/protein. Sketch OK if show bands
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why do we use PCR?
The polymerase chain reaction (PCR) is used for creating multiple copies of a specific section of DNA
from a sample. 100 billion identical strands can be produced from a single DNA segment within a few hours. Used when scientists are only able to obtain tiny fragments of DNA, e.g. at a crime scene or from fossils
130
describe the steps involved in PCR?
1. DENATURING
- dna is heated to 90 degrees to denature the double helix
2. PRIMER ANNEALING
- mixture is cooled to about 50 degrees
- primers bind to each of the complimentary base sequences on both pairs- acting as starter points for the replication of new DNA molecules
3. PRIMER ELONGATION
- mixture is heated to 72 degrees
- starting at the primers, DNA polymerase begins to read the DNA code and builds a complimentary strand of DNA
- this doubles the amount of strands and is repeated.
131
describe the process of cell-mediated immunity (4)
1. A macrophage or B lymphocyte presents the foreign antigen to a specific T lymphocyte in lymph nodes.
2. The T lymphocyte is activated/sensitised, which enlarges & divides into clones.
3. Some clones become memory cells in the lymphoid tissue.
4. T lymphocytes that do not become memory cells either become killer T-cells, helper T-cells & suppressor T-cells
132
describe the process of antibody mediated immunity (5)
1. Antigens in blood or lymph are recognised by B lymphocytes.
2. B lymphocytes enlarge & divide into plasma.
3. B lymphocytes that did not differentiate become memory cells.
4. Plasma secretes antibodies, which travel through blood lymph & circulatory fluid reaching the
response site.
5. Antibodies combine with antigens forming an antigen-antibody complex.
133
describe the cause of hypothyroidism:
through problems with the thyroid gland or due to problems with the pituitary gland or hypothalamus. The most common cause is an attack on the thyroid gland by the patient’s immune system, this is known as Hashimoto’s disease. Another cause of hypothyroidism is a severe deficiency of iodine, a deficiency of iodine in the diet can prevent the thyroid gland from making enough hormones. Another cause is surgery for cancer of the thyroid gland that involves the removal of the thyroid gland.
134
symptoms of hypothyroidism;
- the thyroid gland is under-active & does not make enough of the thyroxine hormone.
- may experience slow heart rate, unexplained weight gain, fatigue, lack of energy, goitre
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how is hypothyroidism treated?
-treated with hormones made synthetically by a chemical process. Levothyroxine is the most commonly prescribed drug for thyroid hormone replacement. It is a synthetic form of T4. If the cause is lack of iodine it is treated by the inclusion of extra iodine in the diet.
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cause of hyperthyroidism:
Occurs when the thyroid gland is over-active & produces too much of the hormone thyroxine. The most common type of hyperthyroidism is known as Grave’s disease. It is an enlargement of the thyroid caused by an immune system reaction. There is a genetic predisposition for the condition.
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symptoms of hyperthyroidism:
The increased production of thyroxine over-stimulates cells & the body’s processes speed up. For this reason, people experience symptoms such as appetite/fatigue/sweating/anxiety/in the case of Grave’s disease, protruding eyeballs.
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how is hyperthyroidism treated?
drugs that block the thyroid glands use of iodine. The surgery to remove some or all of the gland. Another method is to give the patient a drink containing radioactive iodine which is taken up by the cells in the thyroid which are then killed. other cells do not absorb the iodine.
139
cause of type 2 diabetes?
the bodies cells cannot respond to insulin properly (insulin resistance). Type 2 diabetes has a strong genetic & family related risk factor. It usually develops in people over the age of 45 with a genetic disposition to the condition. Type 2 diabetes is a lifestyle disease. this means it is caused by poor diet, lack of physical exercise, smoking etc.
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Symptoms of type 2 diabetes?
patients are able to produce insulin but their cells don't respond to it (insulin resistance). if insulin cannot do its job the glucose channels do not open properly and there is a build up of glucose in the blood rather than in the cells for energy
-symptoms include thirstiness, passing more urine, tired, blurred vision
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medical treatments of type 2 diabetes?
management programs that aim to keep blood glucose levels within the normal range. Management includes careful diet, regular physical activity, healthy weight, monitoring blood glucose & medication that regulates blood glucose or insulin therapy.
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cause of type 1 diabetes
Begins in childhood & may have a genetic factor, occurs because of a fault in the patient’s immune system that causes the destruction of beta cells in the Islets of Langerhans of the pancreas. It is not known what causes the auto-immune reaction.
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symptoms of type 1 diabetes
causes serious disruptions to homeostasis. Beta cells produce insulin & because they are being destroyed, a person with type 1 diabetes does not produce insulin. Without insulin cells are resistant to the effects of insulin meaning they cannot take in glucose from the blood or
stimulate the conversion of glucose into glycogen
-symptoms include excessive thirst, frequent urination, weight loss, fatigue, kidney failure, heart attacks, strokes, nerve damage
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treatments of type 1 diabetes
Monitoring blood-sugar levels by testing blood droplets in a glucose meter. Regular injections of insulin or the use of a programmable pump that provides a continuous supply of insulin under the skin. Pancreas replacement. Yeast is now used to make insulin for the treatment of diabetes’s & almost all the insulin used is biosynthetic recombinant ‘human’ insulin instead of animal insulin. (Future) Gene therapy can also be used to treat type-1 diabetes, it involves the stimulation of differentiated cells such as pancreas and liver cells to secrete insulin from their own insulin genes.
145
what is the function of the carotid and aortic bodies?
-they are peripheral chemoreceptors that detect change in the chemical composition of the arterial blood and send signals to the autonomic ns retrospectively
146
compare and contrast the action of water soluble and lipid soluble hormones and describe how cortisol and ADH affect their target cells (7 marks each)
CORTISOL
1. lipid soluble hormones enter the cell
2. attaches to receptors in the cytoplasm/on organelles/mitochondria/dna/nucleus
3. causes genes to be activated to produce particular enzyme/protein/changes rate of production of enzymes/ changes rate of transcription and translation
4. these effects are permanent and lasting
5. cortisol hass receptors on all body cells
6. cortisol is produced in times of stress
7. converts fat to glucose for energy
ADH
1. water soluble
2. attaches to receptors on/in the cell
3. this releases a secondary messenger
4. which alters enzyme activity/ changes the concentration of enzymes
5. which is much shorter acting
6. ADH has receptors on DCT and collecting tubules to become more permeable to water
7. so more water is reabsorbed from the filtrate back into the blood/ less urine is produced
147
explain how bioinformatics and gene therapy could be used to combat diabetes mellitus (6)
1. bioinformatics would be used to analyse the DNA code of a number of individuals
2. both with diabetes and without
3. in order to determine the genes that contribute to the disease
4. gene therapy would replace the defective diabetes genes
5. with healthy genes
6. so that the beta cells could produce insulin.
148
describe how the resting potential of the neuron membrane is maintained, using the all or none response to explain how stimulus of same nerve cell could result int 2 different outcomes. (10 marks)
1. the resting membrane is maintained by sodium potassium pumps
2. which pumps 3 sodium out and 2 potassium into the cell
3. potassium moves out very easily, sodium moves in less easily
4. the nerve cell membrane has a resting potential of -70mV
5. if a stimulus of less than 15mV is received
6. it is too small to cross the threshold
7. so no change in resting potential occurs/ no action potential occurs/ depolarisation does not occur
8. if the stimulus is greater than 15mV/ crosses the threshold of -55mV
9. depolarisation occurs
10. and due to the all or none response, an action potential occurs
149
compare and contrast the 2 specific immune responses of the body once an antigen has breached the external defences (10 marks)
COMPARE: (any 2)
1. both responses respond to only one type of antigen
2. both produce memory cells
3. both use lymphocytes
4. lymphocytes originate in bone marrow
5. mature cells found in all lymphoid tissue
5. become activated, sensitised, enlarge and divide on recognition of antigen
```
CONTRAST (4)
1. HUMORAL RESPONSE: involves B cells
. CELL-MEDIATED: involves T cells
2. HUMORAL: produces antibodies
. CM: does not produce antibodies
3. HUMORAL: forms into 2 types of cells/ plasma and memory cells
CM: forms 4 types of of cells/ killer T-cells, suppressor, helper and memory cells
4. HUMORAL: matured in bone marrow
CM: matured in thymus
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150
discuss how mutations are caused:
- mutations are inheritable changes in dna that occur during cell division, DNA replication or from damage due to mutagens
- mutagens are substances that increase the rate at which mutations occur
- mutagens could include x-rays, UV rays, mustard gas, formaldehyde, radioactive waste, nuclear explosions, sulphur dioxide or antibiotics
- the mutations could include: point mutation/ substitution/ insertion/ deletion/ gene mutation/ inversion
151
how can people become resistant to diseases?
EG MALARIA
- there must be variation in a population
- more individuals are born than survive to maturity
- the numbers of people in the population is maintained over time
- the lack of the receptor for malaria is adaptive and aids survival
- those who miss the receptor survive and reproduce
- those with the receptor have reduced survival rate therefor reproduce less
- lack of receptor increases in frequency from one generation to next therefor overtime the population increases to a majority without the malaria receptor.
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definition of a steady state system:
a steady state system refers to the maintaining of the body internal environment despite changes to the external environment
153
why is it impossible to hold your breath indefinitely?
it is impossible to hold your breath indefinitely because as you hold your breath the pressure of carbon dioxide and oxygen in your blood changes, eventually starving your body of oxygen which at this point your body functions will begin to shut down.
