TOPIC 6 EXAM QUESTIONS Flashcards
Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process.
- Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid / fall
in pH
OR
Baro / pressure receptors detect rise in blood pressure; - Send impulses to cardiac centre / medulla;
- More impulses to SAN;
- By sympathetic (nervous system for chemoreceptors / CO2)
OR
By parasympathetic (nervous system for baro / pressure
receptors / blood pressure);
When the heart beats, both ventricles contract at the same time.
Explain how this is coordinated in the heart after initiation of the heartbeat
by the SAN.
- Electrical activity only through Bundle of His / AVN;
- Wave of electrical activity passes over / through both ventricles at the
same time;
The fovea of the eye of an eagle has a high density of cones. An eagle
focuses the image of its prey onto the fovea.
Explain how the fovea enables an eagle to see its prey in detail.
- High (visual) acuity;
- (Each) cone is connected to a single neurone;
Accept no retinal convergence.
Accept ‘bipolar/nerve cell’ for neurone. - (Cones send) separate (sets of) impulses to brain;
The retina of an owl has a high density of rod cells.
Explain how this enables an owl to hunt its prey at night.
Do not refer to rhodopsin in your answer.
- High (visual) sensitivity;
Accept retinal convergence. - Several rods connected to a single neurone;
Accept ‘bipolar/nerve cell’ for neurone
Accept 2, ‘many’ or - Enough (neuro)transmitter to reach/overcome threshold
OR
Spatial summation to reach/overcome threshold; more for ‘several’
Explain how applying pressure to the Pacinian corpuscle produces the
changes in membrane potential
- (Pressure causes) membrane / lamellae to become deformed /
stretched; - Sodium ion channels in membrane open and sodium ions move
in; - Greater pressure more channels open / sodium ions enter.
Explain how the resting potential of –70 mV is maintained in the sensory
neurone when no pressure is applied.
- Membrane more permeable to potassium ions and less permeable to
sodium ions; - Sodium ions actively transported / pumped out and potassium
ions in.
Multiple sclerosis is a disease in which parts of the myelin sheaths
surrounding neurones are destroyed. Explain how this results in slower
responses to stimuli.
- Less / no saltatory conduction / action potential / impulse
unable to ‘jump’ from node to node; - More depolarisation over length / area of membranes.
topics to use in nerve essay
Enzymes
3.2.1.2 Structure of prokaryotic cells and of viruses
3.2.3 Transport across cell membranes
3.2.4 Cell recognition and the immune system
3.3.4.1 Mass transport in animals
3.4.2 DNA and protein synthesis
3.5.1 Photosynthesis
3.5.2 Respiration
3.6.1.1 Survival and response
3.6.1.2 Receptors
3.6.1.3 Control of heart rate
3.6.2.1 Nerve impulses
3.6.2.2 Synaptic transmission
3.6.3 Skeletal muscles
3.6.4.1 Principles of homeostasis
Suggest two advantages of simple reflexes.
- Rapid;
- Protect against damage to body tissues;
- Do not have to be learnt;
- Help escape from predators;
- Enable homeostatic control.
Explain how a resting potential is maintained across the axon membrane in
a neurone
- Higher concentration of potassium ions inside and higher
concentration of sodium ions outside (the neurone)
OR
potassium ions diffuse out
OR
sodium ions diffuse in;
Accept ‘more’ for ‘higher concentration’.
Accept ‘sodium ions can’t diffuse in (due to
alternative explanation). - (Membrane) more permeable to potassium ions (leaving
than sodium ions entering)
OR
(Membrane) less permeable to sodium ions (entering
than potassium ions leaving);
Accept for ‘less permeable to sodium ions’ is
‘impermeable to sodium ions’ or ‘sodium
gates/channels are closed’ (alternative
explanation). - Sodium ions (actively) transported out and potassium ions in;
Explain why the speed of transmission of impulses is faster along a
myelinated axon than along a non-myelinated axon.
- Myelination provides (electrical) insulation;
Reject thermal insulation.
Accept description of (electrical) insulation.
2. (In myelinated) saltatory (conduction)
OR
(In myelinated) depolarisation at nodes (of Ranvier);#
- In non-myelinated depolarisation occurs along whole/length (of axon);
Accept action potentials for depolarisation.
A scientist investigated the effect of inhibitors on neurones. She added a
respiratory inhibitor to a neurone. The resting potential of the neurone
changed from –70 mV to 0 mV.
- No/less ATP produced;
- No/less active transport
OR
Sodium/potassium pump inhibited;
Accept Na+ not/fewer moved out and K+ not/fewer
moved in. - Electrochemical gradient not maintained
OR
(Facilitated) diffusion of ions causes change to 0 mV
OR
(Results in) same concentration of (sodium and
potassium) ions (either side of membrane)
OR
No net movement of (sodium and potassium) ions;
Describe the sequence of events involved in transmission across a cholinergic
synapse.
Do not include details on the breakdown of acetylcholine in your answer.
- Depolarisation of presynaptic membrane;
Accept action potential for depolarisation. - Calcium channels open and calcium ions enter (synaptic knob);
Accept Ca2+.
- (Calcium ions cause) synaptic vesicles move to/fuse with
presynaptic membrane and release
acetylcholine/neurotransmitter;
Accept abbreviations for acetylcholine as term is in
the question.
- Acetylcholine/neurotransmitter diffuses across (synaptic cleft);
Accept abbreviations for acetylcholine as term is in
the question. - (Acetylcholine attaches) to receptors on the postsynaptic membrane;
- Sodium ions enter (postsynaptic neurone) leading to depolarisation;
Accept Na+.
Accept ‘action potential’ or ‘generator potential’ for
depolarisation.
Dopamine is a neurotransmitter released in some synapses in the brain.
The transmission of dopamine is similar to that of acetylcholine.
Dopamine stimulates the production of nerve impulses in postsynaptic
neurones.
Describe how.
- (Dopamine) diffuses across (synapse);
- Attaches to receptors on postsynaptic membrane;
Ignore name/nature of receptor e.g. cholinergic - Stimulates entry of sodium ions and depolarisation/action potential;
Accept Na+ for sodium ions
Accept generator potential for action potential
Dopamine has a role in numerous processes in the brain including pain
relief. The release of dopamine can be stimulated by chemicals called
endorphins produced in the brain. Endorphins attach to opioid receptors on
presynaptic neurones that release dopamine.
Morphine is a drug that has a similar structure to endorphins and can
provide pain relief.
- Morphine attaches to opioid receptors;
Reject reference to active site - (More) dopamine released (to provide pain relief);
Reject receptors release dopamine
GABA is a neurotransmitter released in some inhibitory synapses in the
brain. GABA causes negatively charged chloride ions to enter postsynaptic
neurones.
Explain how this inhibits postsynaptic neurones.
- (Inside of postsynaptic) neurone becomes more
negative/hyperpolarisation/inhibitory postsynaptic potential;
Ignore K+
Accept -75mV or any value below this as equivalent
to more negative
Accept ‘decrease in charge’ - More sodium ions required (to reach threshold)
OR
Not enough sodium ions enter (to reach threshold);
Accept Na+ for sodium ions - For depolarisation/action potential;
Context must covey idea that depolarisation / action
potential is less likely
Use your knowledge of how myosin and actin interact to suggest how the
myosin molecule moves the mitochondrion towards the presynaptic
membrane.
- Myosin head attaches to actin and bends / performs
powerstroke; - (This) pulls mitochondria past / along the actin;
- Other / next myosin head attaches to actin (and bends /
performs powerstroke);
) This movement of mitochondria happens when nerve impulses arrive at the
synapse.
Suggest and explain one advantage of the movement of mitochondria
towards the presynaptic membrane when nerve impulses arrive at the
synapse.
- (Mitochondria) supply (additional) ATP / energy;
- To move vesicles / for active transport of ions / for myosin to
move past actin
OR
Re-synthesis / reabsorption of neurotransmitter / named
neurotransmitter;
Explain how a decrease in the concentration of calcium ions within muscle
tissues could cause a decrease in the force of muscle contraction.
- (Less/No) tropomyosin moved from binding site
OR
Shape of tropomyosin not changed so binding site not
exposed/available;
Ignore troponin.
Reject active site only once. - (Fewer/No) actinomyosin bridges formed;
Accept actin and myosin do not bind.
Reject active site only once. - Myosin head does not move
OR
Myosin does not pull actin (filaments)
OR
(Less/No) ATP (hydrol)ase (activation);
Reject ATP synthase.
In muscles, pyruvate is converted to lactate during prolonged exercise.
Explain why converting pyruvate to lactate allows the continued production
of ATP by anaerobic respiration.
- Regenerates/produces NAD
OR
oxidises reduced NAD;
Reject NADP and any reference to FAD.
Accept descriptions of oxidation e.g. loss of hydrogen. - (So) glycolysis continues;
The image shows glycogen granules present in skeletal muscle.
Explain their role in skeletal muscle.
- As a store of glucose
Ignore provide energy
OR
To be hydrolysed to glucose; - For respiration / to provide ATP;
During vigorous exercise, the pH of skeletal muscle tissue falls. This fall in
pH leads to a reduction in the ability of calcium ions to stimulate muscle
contraction.
Suggest how.
- Low pH changes shape of calcium ion receptors
Do not accept tropomyosin does not move - Fewer calcium ions bind to tropomyosin;
Accept troponin - Fewer tropomyosin molecules move away;
- Fewer binding sites on actin revealed;
- Fewer cross-bridges can form
Describe the roles of calcium ions and ATP in the contraction of a
myofibri
- Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
- (Calcium ions) cause movement of tropomyosin (on actin);
- (This movement causes) exposure of the binding sites on the
actin; - Myosin heads attach to binding sites on actin;
- Hydrolysis of ATP (on myosin heads) causes myosin heads to
bend; - (Bending) pulling actin molecules;
- Attachment of a new ATP molecule to each myosin head
causes myosin heads to detach (from actin sites).
ATP is an energy source used in many cell processes. Give two ways in
which ATP is a suitable energy source for cells to use.
- Releases relatively small amount of energy / little energy lost as
heat;
Key concept is that little danger of thermal death of
cells - Releases energy instantaneously;
Key concept is that energy is readily available - Phosphorylates other compounds, making them more reactive;
- Can be rapidly re-synthesised;
- Is not lost from / does not leave cells.
What is the role of ATP in myofibril contraction?
- (Reaction with ATP) breaks/allows binding of myosin to actin/
actinomyosin bridge; - Provides energy to move myosin head;
Neonatal diabetes is a disease that affects newly born children. The
disease is caused by a change in the amino acid sequence of insulin.
This change prevents insulin binding to its receptor. Explain why this
change prevents insulin binding to its receptor.
- Changes tertiary structure;
Reject change in tertiary structure of receptor. - No longer complementary (to receptor);
Reject ‘active site’ or reference to enzyme or
substrate.
Using your knowledge of the kidney, explain why glucose is found in the
urine of a person with untreated diabetes
- High concentration of glucose in blood/filtrate;
Accept tubule for filtrate. - Not all the glucose is (re)absorbed at the proximal convoluted tubule;
Reject no glucose is (re)absorbed. - Carrier/co-transport proteins are working at maximum rate
OR
Carrier/co-transport proteins/ are saturated;
Describe the role of glucagon in gluconeogenesis.
- (Attaches to receptors on target cells and) activates/stimulates
enzymes;
Reject ‘produces enzymes’. - Glycerol/amino acids/fatty acids into glucose;
Explain how increasing a cell’s sensitivity to insulin will lower the blood
glucose concentration.
- (More) insulin binds to receptors;
- (Stimulates) uptake of glucose by channel/transport proteins
OR
Activates enzymes which convert glucose to glycogen;
Explain how inhibiting adenylate cyclase may help to lower the blood
glucose concentration.
- Less/no ATP is converted to cyclic AMP/cAMP;
- Less/no kinase is activated;
- Less/no glycogen is converted to glucose
OR
Less/no glycogenolysis;
Each year, a few people with type I diabetes are given a pancreas
transplant. Pancreas transplants are not used to treat people with type II
diabetes.
Give two reasons why pancreas transplants are not used for the treatment
of type II diabetes.
- (Usually)Type II produce insulin;
- Cells / receptors less sensitive / responsive (to insulin)
OR
Faulty (insulin) receptors; - (Treated / controlled by) diet / exercise;
Give two ways in which people with type 1 diabetes control their blood
glucose concentration.
- Treat with insulin (injection/infusion);
- (Control) diet/control sugar intake;
Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of
both men and women. Affected individuals have proteinuria (high quantities of
protein in their urine).
(a) Suggest how AS could cause proteinuria
- Affects/damages basement membrane
OR
More protein channels/carriers in basement membrane; - Proteins can pass into the (glomerular) filtrate/tubule;
Describe how ultrafiltration occurs in a glomerulus.
- High blood/hydrostatic pressure;
Ignore references to afferent and efferent arterioles
Ignore ‘increasing/higher blood pressure’ as does not
necessarily mean high - Two named small substances pass out eg water, glucose,
ions, urea;
Accept correct named ions
Accept mineral ions/minerals
Accept amino acids/small proteins
Ignore references to molecules not filtered - (Through small) gaps/pores/fenestrations in (capillary)
endothelium;
Accept epithelium for endothelium - (And) through (capillary) basement membrane;
Give the location of osmoreceptors in the body of a mammal.
Hypothalamus.
When a person is dehydrated, the cell volume of an osmoreceptor
decreases.
Explain why
- Water potential of blood will decrease;
- Water moves from osmoreceptor into blood by osmosis
Stimulation of osmoreceptors can lead to secretion of the hormone ADH.
Describe and explain how the secretion of ADH affects urine produced by
the kidneys.
- Permeability of membrane / cells (to water) is increased;
- More water absorbed from / leaves distal tubule / collecting duct;
- Smaller volume of urine;
- Urine becomes more concentrated.
) Creatinine is a breakdown product of creatine found in muscle tissues.
Apart from age and gender, give two factors that could affect the
concentration of creatinine in the blood.
Muscle / body mass
Ethnicity
Exercise
Kidney disease –
The acidic pH conditions created by osteoclasts cause the inactive form of
the protein osteocalcin to change into the active form of osteocalcin.
Suggest how.
- (Change in pH) changes / breaks ionic / hydrogen bonds;
Ignore ref. to peptide or sulfur-sulfur bonds
Accept polar bonds - Changes tertiary structure;
Binding of insulin leads to an increase in the rate of respiration in cells such
as osteoblasts.
- (Insulin) leads to more transport proteins / channel (proteins) / carrier
(proteins) for glucose;
Ignore references to opening channels
Accept co-transport / GLUT 1 or 4 protein - More glucose (for respiration / glycolysis) enters cell;
Give two reasons why transmission across a cholinergic synapse is unidirectional.
- (Only) the presynaptic
neurone/knob/membrane releases/has
neurotransmitter/acetylcholine;
2.(Only) the postsynaptic
neurone/membrane has receptors
OR
No receptors in the presynaptic
neurone/membrane;
Name the part of the body which releases antidiuretic hormone (ADH) into the blood
Posterior pituitary;
Alcohol decreases the release of ADH into the blood.
Suggest two signs or symptoms which may result from a decrease in ADH.
- Dehydration/thirst;
- Frequent urination
OR
Increase in volume of urine;
3.Less concentrated urine
OR
Dilute urine
OR
Urine paler/lighter in colour;
Describe the effect of ADH on the collecting ducts in kidneys
- (Stimulates) addition of channel proteins into
membrane; - Increases permeability to water
OR
(More) water (re)absorbed; - By osmosis
