Topic 7/8 Flashcards
Describe the differences in the structure of a myelinated sensory neuron and a myelinated motor neuron (3)
In sensory neuron, dendron is longer
in sensory neuron dendron is myelinated
In sensory neuron axon is shorter
explain the electrical changes in an axon when stimulated by a nerve impulse (4)
potential difference across axon changing
due to increased permeability to sodium ions (volt gates open)
sodium ions cause depolarisation
potassium channels then open
potassium ions cause repolarisation of the membrane
Explain how conduction of nerve impulses will be affected if the following membrane proteins are damaged (6) 1 - Acetylcholine receptors 2 - Voltage-gated sodium ion channels 3 - Voltage-gated potassium ion channels 4 - Calcium ion channel
1 - if Acetylcholine receptors on post-synaptic neuron affected, post-synaptic neuron will not depolarise
2 - if Voltage-gated sodium ion channels affected, no depolarisation of axon
3 - if Voltage-gated potassium ion channels, no repolarisation of axon, no propagation of action potential
4 - if Calcium ion channels affected, vesicles in pre-synaptic neuron will not fuse with pre-synaptic membrane, neurotransmitter wont be released
Explain why there is a difference in the velocity of a myelinated neuron’s nerve impulse and an unmyelinated one (5)
Schwann cells cover axon of myelinated neuron
Schwann cells provide insulation
depolarisation occurs at nodes of Ranvier
Saltatory conduction depolarises part of a neuron not whole one
impulse jumps from node to node
describe and explain the sequence of events that occur at the synapse after a neurotransmitter has been released (5)
Diffuses across cleft
binds to receptors on post-synaptic membrane
causes it to depolarise
if depolarisation is sufficient enough, action potential is set up in post-synaptic membrane
neurotransmitters that are not taken up by the post-synaptic membrane are digested by enzymes in the cleft
Spatial summation allows multiple impulses from various neurons to meet at one neuron and continue to the next as one impulse
in which region is the hypothalamus found (1)
forebrain
State the functions of these regions of the brain (4)
1 - cerebral hemisphere
2 - cerebellum
3 - medulla oblongata
1 - cerebral hemisphere, initiating and controlling voluntary muscle movement
2 - cerebellum, coordinating skeletal muscle movement, balance and posture
3 - medulla oblongata, controlling heart and breathing rate
Describe the role of ATP in the contraction of a muscle fibre (5)
myosin slides along actin to contract muscle fibre
ATP binds to myosin head causing cross-bridge between actin and myosin to break
ATP hydrolyses to ADP and Pi releasing energy, causing myosin head to reset
myosin head binds to actin forming a cross-bridge
Pi is released from myosin head
ATP also transports Ca ions back into sarcoplasmic reticulum
Compare and contrast the properties of the slow and fast twitch cycle
Property - Slow twitch - Fast twitch Myoglobin - more - less mitochondria - many - few Glycogen - less - more capillaries - many - few Myosin ATPase activity - low - high fibre diameter - small - large Creatine phosphate - low high
explain changes when calcium ions bind to molecules in myofibrils (4)
myosin heads can bind to binding sites
myosin changes shape
actin filaments slide over the myosin, causing sarcomeres to shorten
ATP is hydrolysed releasing ADP and Pi
Explain how the blood pH of a sprint is returned to normal after a race (5)
Low pH due to acid in blood
lactate taken to liver
More oxygen has to be inhaled than normal
used to convert lactate back into pyruvate with production of reduced NAD
Pyruvate converted to glucose
chemoreceptors detect change in pH, increased rate
in genetic modification how does addition of chemical cause human gene to be switched on (3)
Chemical could be transcription factor
interaction at bacterial cell surface membrane
the transcription factor is activity
advantage of injecting chemicals into veins rather than arteries
Larger lumen
thinner wall so easier to penetrate
bp is low so less damage to vein
cell that links rod cell to sensory neuron (1)
Bipolar neuron
explain why only one restriction enzyme is used for genetic modification (3)
cuts a specific sequence of bases
generates complimentary sticky ends
easier to join together
suggest why FMRI is considered better than CT for studying brain function (2)
it views brain activity directly
safer as it does not use x rays
sees brain activity over a period of time
how is NAD formed in electron transport chain (3)
due to reduced NAD releasing electrons
electrons go to carriers
H+ moved into inner membrane space
explain link between ATP and H+ in electron transport chain (3)
H+ pass through ATP synthase
H+ pass down electrochemical gradient
Energy is released to join ADP and Pi
compare and contrast CT and MRI for studying brain structure (6)
Image resolution is higher in MRI and lower and CT
CT can only identify larger structures, MRI can identify small ones
MRI uses magnetic fields, CT uses xrays
MRI is safer than Xrays but is louder
both give 2D/3D images
MRI is more expensive than CT
Suggest why pupils appear black (1)
pigment at the back of the eye absorbs light
explain why panting generates heat (2)
panting involves muscle contractions
muscle contraction requires respiration which releases energy
explain the role of negative feedback in the panting response of dogs (5)
Blood temperature is kept in a state of homeostasis
thermoreceptors detect changes in temperature
thermoreceptors send nerve impulses to thermoregulatory centre
if blood temperature increases, TC sends nerve impulses to increase panting
panting causes blood temperature to fall
once normal blood temp is reached, impulse to TC stops and panting stops
Describe how FMRI can be used in an investigation (3)
conduct FMRI scan while someone is engaged in a cognitive activity
indicates areas with high blood flow
lit up areas indicate higher levels of brain activity
When a muscle fibre contracts what happens to the number of myosin heads (1)
stays the same
What does the binding of calcium ions to troponin do (1)
expose myosin bindings sites
describe how the arrival of nerve impulse at synapse releases neurotransmitters (3)
Ca2+ enters synaptic knob
vesicles contain neurotransmitters
they fuse with presynaptic membrane and neurotransmitters are released by exocytosis
Explain the difference between the structure of a myelinated sensory neuron and myelinated motor neuron (3)
IN SENSORY NEURON
dendron longer
dendron myelinated
axon shorter
explain how the sinoatrial node ensures that oxygenated blood enters the aorta (4)
initiates electrical activity over atria
causes atria to contract
forcing oxygenated blood into left ventricle
electrical activity from SAN received by AVN travel through bundle of HIC
causing left ventricle to contract forcing blood into aorta
explain how twin studies can be used to compare the effects of nature and nurture on human development (4)
monozygotic twins are genetically identical
derived from one egg and sperm
any phenotypic difference is due to nurture
dizygotic twins are genetically different
any phenotypic difference when the environment is the same is likely to be nature
suggest why mean concentration of L-dopa in blood plasma decreases after some time (4)
l-dopa leaves blood into tissues
l-dopa crosses blood brain barrier
converted to dopamine
l-dopa is broken down
Explain how you would use traces from spirometer to compare tidal volume and breathing rates of male + female participants (6)
calibration for volume
calibration for time
one peak = one breath
breathing rate is number of peaks per minute
use the same age of participants for both males and females
use non-smokers
traces taken at test
replicate the procedure 3 times with the same group to acquire mean results
suggest how habituation is beneficial to sea slugs (2)
avoids wasted effort to non-threatening stimulus, more energy for other purposes
explain what is meant by phase III trial (2)
randomised trial
large sample of patients
use of placebos
explain why radical and circular muscles need to be antagonistic (3)
to constrict pupils: Radical muscles relax, circular muscles contract
To dilate pupils: Radical muscles contract, circular muscles relax
allows changes to take into account varying light intensity
muscles can only shorten
antagonistic muscles have opposite effects
describe and explain the role of calcium ions and ATP in muscle contraction (5)
vesicles contain calcium ions
which bind to troponin
tropomyosin moves exposing binding sites for myosin
ATP needed to remove calcium ions
ATP provides shape for changing shape of myosin
ATP required to break down cross-bridges
explain how high conc of H+ is maintained in intermembrane space (3)
H+ ions from reduced NAD pumped into intermembrane space energy needed for pump electrons move along electron transport chain ETC on cristae
describe how the cardiovascular centre in the medulla oblongata affects SAN during exercise (2)
increased impulses to SAN
via sympathetic nervous system
stimulates more frequent depolarisation in SAN
increases heart rate
explain why muscles occur in antagonistic pairs (2)
muscles cannot extend themselves
need opposing muscle to extend
antagonistic muscles allows control of movement
two factors that determine how quickly an animal becomes habituated (2)
time between each stimulus
duration of the stimulus
describe how increased heart rate increases oxygen uptake by blood in the lungs (3)
more blood passing through lungs
oxygen diffuses into blood
oxygen diffuses faster
describe how epo production might be shut down when oxygen levels in blood are normal (3)
gene transcription stops
transcription involves joining RNA bases on a template strand complimentary to the exposed DNA strand
no MRNA produced
no translation of MRNA
describe how fmri is used to investigate brain function (2)
detects levels of oxygenation of blood
increased flow of oxygen suggests increased activity
brain activity can be studied in relation to tasks
describe interaction of troponin and tropomyosin when skeletal muscle fibre contracts (2)
calcium ions bind to troponin
troponin changes shape
this displaces tropomyosin
Describe the role of the human nervous system in returning raised body temp to its normal level (4)
thermoreceptors in hypothalamus
detects change in blood core temp
heat loss centre activated
Autonomous nervous system sends impulse down motor neuron to effector
vasodilation of blood vessels, sweat released
suggest how the human genome project has helped develop drugs (3)
human genome project identified millions of alleles
drug targets specific allele
mutant allele can no longer express itself
this type of drug is very effective
explain how plants can be genetically modified to be resistant to damage by insects (4)
Use gene that provides resistance to insects
gene could code for insect enzyme inhibition
gene would have to be isolated from rest of the insect resistant plan
suggest how heart decreases during hibernation (3)
Cardiovascular system sends nerve impulse down the presynaptic nerve to the SAN
decreased frequency off signals from the SAN
describe how curate ligaments can be repaired with minimal damage to the joint (2)
keyhole surgery
doctor watched procedure through a screen
explain the role of acetylcholine in nerve impulse transmission (2)
to transmit nerve impulse across synapse
because action potential cant cross the gap
role of ligaments?
attach bones to other bones
allows some movement
which provides stability
explain how neurons enable pupils to increase in diameter in dim light (3)
Na+ ions are pumped out of inner segment causing membrane to depolarise
glutamate is released which inhibits the bipolar cell
bipolar cell does not depolarise and impulse is not produced down the optic nerve
Radial cells contract causing pupils to dilate
describe the role of myelin sheath in the conduction of nerve impulses (4)
acts as an electrical insulator
Depolarisation at nodes
impulse jumps node to node known as saltatory conduction
this provides faster conduction rather than depolarisation the entire axon
describe how structure of axon cell membrane is related to the conduction of nerve impulses (3)
phospholipids limit ion movement
proteins span the membrane
sodium potassium ion pump moves ions
protein gates allow diffusion of ions
explain how electrocardiogram can be used to calculate someone’s heart rate (3)
shows electrical activity of the heart
peak is one heart beat
count number of peaks within a minute
Explain how high CO2 concentration can change heart rate (5)
concentration of CO2 in alveoli is higher
concentration of CO2 in blood is higher
detected by chemoreceptors in the aorta, impulse sent to cardiovascular control centre in medulla
more impulses are sent via the autonomic nervous system to SAN
Noradrenaline is released into SAN
heart rate increases
suggest how tendons and antagonistic muscles cause lower leg to kick a ball (4)
extensor muscles contract leg is straightened flexor muscles relax muscles work in opposite directions, one contracts the other relaxes tendons attach muscles to bone
explain what is meant by the term myogenic (2)
stimulation generated from within muscle
resulting in depolarisation
suggest suitable units for Y axis on an ECG (1)
Millivolts/MV
explain how electrocardiogram can be used to calculate person’s heart rate (3)
shows electrical activity of the heart
one heart beat is one peak on the ECG
count number of peaks within 1 minute
heart rate calculated by divided beats/minute
study scanning technique to study physical and emotional experiences of brain (3)
FMRI fmri operates in real time as experience will be short lived active areas light up on the image high resolution as areas may be small
what happens to rod cells in the dark (5)
Opsin uncouples from rod cell surface membrane
rhodopsin formed from retinal and opsin
results in dark adaptation
permeability of cell surface membrane to Na+ increases
hyperpolarisation of cell decreases
more neurotransmitter is released
explain how heart rate of person is controlled when level of exercise increases during physical activity (6)
increased respiration rate rate in muscle cells
more CO2 in blood
more lactate in blood
chemoreceptors in medulla stimulated
impulses from cardiovascular centre in medulla sent to the SAN through autonomic nervous system
SAN excitation rate increases, results in increased heart rate
ethical reason why drugs like EPO should be banned in sports (2)
it is not fair
poses a health risk to athletes
suggest why fast twitch muscle fibres are less red in colour than slow twitch muscle fibres (2)
some have less myoglobin present
fewer red blood cells
fewer capillaries present
respiration is mainly anaerobic
describe how muscles in blood vessels in the skin help increase heat loss from the body (4)
muscles relax to increase diameter of arterioles
redirects blood to surface of arterioles
increase blood flow to capillaries more heat loss through radiation
state the location of rhodopsin within a rod cell (1)
outer segment
describe what happens to reduced NAD in aerobic respiration (4)
reduced NAD from glycolysis enters membrane
moves to inner membrane of mitochondrion
becomes oxidised as electrons are transferred to electron transport chain
hydrogen ions are pumped into inter membrane space
NAD returns to Krebs cycle
reasons why too little exercise is not good for health (2)
reasons why too much exercise is not good for health (2)
increased risk of obesity
coronary heart disease
wear and tear of joints
suppression of immune system
describe role of oxygen in aerobic respiration (4)
Oxygen is H+ acceptor at end of electron transport chain
oxygen is used to form water
plays a role in oxidative phosphorylation
production of ATP
describes what happens to lactate in muscles (5)
lactate moves into the blood
carried to the liver
lactate is converted to pyruvate
pyruvate is respired
why do older people see less clearly in low light (2)
pupil size is smaller in older people in low light conditions
radical fibres in iris contract less in older people compared to younger people
explain role of IAA in a plant showing phototropism (4)
IAA moves away from light
H bonds between cellulose molecules are broken
cells elongate due to uptake of water
IAA causes more cell elongation of dark side of the stem
how does panting enable dogs to maintain a stable body temp (4)
panting causes heat loss as water evaporates from mouth
heat energy from blood is used
panting increases air movement over tongue
increased air movement increases rate of evaporation
relationship between day light and rhodopsin present (2)
linear relationship
increasing daylight length reduces rhodopsin
