10 Coordination Flashcards
EQ
A myelinated axon conducts impulses faster than a non-myelinated axon. Explain this difference. (3)
- (In myelinated) action potential/depolarisation
only at node(s); - (In myelinated, nerve impulse) jumps from node
to node/saltatory; - (In myelinated) action potential/impulse does
not travel along whole length;
EQ
Explain the shape of the curve for sodium ions between 0.5 ms and 0.7 ms (rapid increase) (3)
(Ion) channel proteins open;
Sodium in;
Changes membrane potential/makes inside of axon less
negative/positive/depolarisation/ reaches threshold;
More channels open/positive feedback;
EQ
During an action potential, the membrane potential rises to +40 mV and then falls. Use
information from the graph to explain the fall in membrane potential. (3)
Potassium channels open;
Potassium out;
Sodium channels close;
EQ
After exercise, some ATP is used to re-establish the resting potential in axons. Explain
how the resting potential is re-established.. (2)
Pump/active transport/transport against concentration
gradient;
Of sodium from axon/sodium out/of potassium in;
EQ
Describe how hormones are different in the cells they affect. (1)
Hormones have widespread effect / affect different organs /
affect different parts of the body / affect distant organs / only
affect cells with right receptor;
EQ
Describe how hormones and local chemical mediators reach the cells they affect. (2)
- Hormones in blood;
- Local chemical mediators spread by diffusion / spread
directly;
EQ
Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being
unidirectional. (2)
- (Acetylcholine) released from/in presynaptic side;
- Diffusion from higher concentration/to lower concentration;
- Receptors in postsynaptic (side) / binds on postsynaptic
(side) ;
EQ
The black mamba’s toxin kills prey by preventing their breathing. It does this by
inhibiting the enzyme acetylcholinesterase at neuromuscular junctions. Explain how
this prevents breathing. (3)
1. Acetylcholine not broken down / stays bound to receptor; 2. Na+ ions (continue to) enter / (continued) depolarisation / Na+ channels (kept) open / action potentials/impulses fired (continuously); 3. (Intercostal) muscles stay contracted / cannot relax;
EQ
Serotonin is a neurotransmitter released in some synapses in the brain. It is
transported back out of the synaptic gap by a transport protein in the pre-synaptic
membrane.
7 (a) Serotonin diffuses across the synaptic gap and binds to a receptor on the post-synaptic
membrane.
Describe how this causes depolarisation of the post-synaptic membrane. (2)
- Causes sodium ion channels to
open; - Sodium ions enter (cell and
cause depolarisation);
EQ
It is important that a neurotransmitter such as serotonin is transported back out of
synapses. Explain why. (2)
- (If not removed) keeps binding (to
receptors); - Keeps causing action
potentials/depolarisation (in postsynaptic
membrane); - Prevents information being
carried across synapse/described
consequence;
EQ
What conclusion can be made from the results for treatment B? (1) (grows horizontally, 0 degree curvature)
1. (Cells in) root tip detect gravity / respond to gravity; OR 2. IAA/auxin is produced in the root tip;
EQ
(low on top, high on bottom)
Explain how this distribution of IAA causes the root to bend (2)
1. Greater (elongation) growth on top of root/less growth on bottom of root; 2. (IAA) at bottom of root/where IAA concentration high inhibits expansion/elongation (of cells); 3. (IAA) at top of root/where IAA concentration low leads to expansion/elongation (of cells);
EQ
When a young shoot is illuminated from one side, IAA stimulates growth on the shaded
side. Explain why growth on the shaded side helps to maintain the leaves in a
favourable environment. (2)
- Causes plant to bend/grow towards light / positive
phototropism; - (Light) required for photosynthesis;
EQ
The pea seedlings were kept in the dark after each treatment. Explain why this was
necessary. (1)
1. (Seedlings) respond to light / are phototropic; OR 2. (Only) measuring the effect of gravity / response to gravity;
EQ
Name the process by which IAA moves from the growing regions of a plant shoot to
other tissues. (1)
Diffusion;
EQ
Suggest how indoleacetic acid (IAA) could have caused the results for:
treatment A (grows downwards, 60 degree curvature)
treatment B (upper half of root tip removed, grows downwards, 30 degree curvature)
) 1. IAA/auxin moves to lower side / more IAA/auxin on lower side; 2. Lower side grows less/slower / upper side grows more /faster / inhibits growth on lower side;
- Less IAA/auxin (produced);
- Lower side grows
more/faster / less inhibition
of growth on lower side;
Name 2 differences between nervous and hormonal system.
Slow, long-lasting, widespread, blood plasma
Rapid, short-lived, localised, nerve cells
Chemical mediators
2 examples?
Released by infected/injured cells
Spread by diffusion
Cause inflammation
Histamine and prostaglandins
Name 3 external stimuli and why they are needed in plants.
Light - photosynthesis
Water - photosynthesis/plant support
Gravity - anchoring
Effect of IAA (shoots)
- Cells in the shoot tip produce IAA
- Light causes IAA to move to shaded side, greater concentration
- IAA causes elongation of cells
- Shaded side grows faster causing shoot to bend towards light.
Effect of IAA (roots)
- Cells in the root tip produce IAA
- Gravity causes IAA to move to lower side, greater concentration
- IAA inhibits elongation of cells
- lower side grows slower.
Why does the cell body contain nucleus and RER?
What do dendrons do?
What does the axon do?
Give 2 functions of Schwann cells
To produce proteins/neurotransmitter
Carry nerve impulse to cell body
Carry nerve impulse away from cell body
Protection/insulation of axon, phagocytosis
Define nerve impulse
a temporary reversal of the electrical p.d. across the axon membrane. (also action potential).
Give 3 ways in which movement of ions across the axon membrane is controlled.
Plasma membrane
Channel proteins
Na-K pumps
Resting potential:
inside/outside?
charge?
state?
ESTABLISHING RESTING POTENTIAL
Chemical gradient (4)
Electrical gradient (2)
INSIDE = NEGATIVE, OUTSIDE=POSITIVE
Charge = -65mV
Axon polarised
- Na-K pump AT Na ions out, AT K ions in (Na:K=3:2)
- Outside more positive than inside
- Through channel proteins Na ions diffuse in, K ions diffuse out (axon 100x more permeable to K)
- Outside even more positive
- Diffusion of K stops because attracted to -ive inside, repelled by +ve outside
- Equilibrium - gradients balanced, no net movement of ions
Action potential:
inside/outside?
charge?
state?
When NI reaches end of axon? (2)
At +40mV? (4)
Resting potential re-established?
INSIDE = POSITIVE, OUTSIDE = NEGATIVE
Charge = +40mV.
Depolarised
- NI reaches end of axon:
- Na channels open, Na ions diffuse in = depolarisation
- More Na channels open
- At +40mV:
- Na channels close
- K channels open, K ions diffuse out = repolarisation
- More K channels open (K ions cause temporary overshoot = hyperpolarisation)
- K channels close
- Na-K pump re-establishes resting potential by AT Na ions out
How does an action potential pass along an unmyelinated axon? (3)
Depolarisation establishes localised electrical circuits
Causes depolarisation further along axon
Behind new region repolarisation
Factors affecting speed of action potential passage:
Myelin sheath (1)
Diameter of the axon (2)
Temperature (3)
Myelinated = faster
Greater diameter = faster
Leakage of ions less likely
Higher temperature = faster
Enzymes work faster, more e-s complexes, more collisions
Enzymes control respiration which provides ATP for active transport
Refractory period
Describe it
Purposes? (3)
When depolarisation in one region, no depolarisation in any other region
Ensures action potential propagated in one direction only
Produces discrete impulses:
Limits the number of action potentials
All-or-nothing principle:
Define threshold value
All:?
Nothing?
= level of stimulus that must be exceeded to generate action potential and therefore nerve impulse
any stimulus above = one action potential
any stimulus below = no action potential
How do organisms perceive the size of a stimulus? (2)
Number of impulses in given time
Different neurones have different threshold values
Define Neurotransmitter
= chemical form of nerve impulse
Define synaptic cleft
= small gap that separates neurones
Define presynaptic neurone
= neurone that releases neurotransmitter.
Define synaptic knob
= portion at end of presynaptic neurone axon (many mitochondria and RER for neurotransmitter production)
Define synaptic vesicles
=store neurotransmitter.
Define postsynaptic neurone
= neurone that receives neurotransmitter - has receptors on membrane that it binds to.
Function of synapses? (2)
Transmit single nerve impulse to multiple neurones (one stimuli, multiple responses)
Combine multiple impulses to single neurone (multiple stimuli, single response)
Features of synapses:
Unidirectionality?
Summation? (3)
Inhibition (inhibitory synapses)? (2)
Nerve impulse passes in one direction (presynaptic to postsynaptic)
- Resolves insufficient quantity of neurotransmitter to exceed threshold value on postsynaptic neurone and generate action potential.
- Spatial summation - multiple presynaptic neurones combined
- Temporal summation - single presynaptic neurone releases lot of neurotransmitter over short period of time (high-frequency)
Cl channels ions open, Cl ions diffuse in =hyperpolarisation
Less likely action potential generated
Define cholinergic synapse
a synapse in which the neurotransmitter is acetylcholine.
Transmission across a cholinergic synapse (6)
Why do acetyl and choline diffuse back across synaptic cleft into presynaptic neurone to be stored in vesicles?
- Nerve impulse reaches reaches end of axon
- Influx of calcium ions into pre-synaptic membrane
- Synaptic vesicles fuse with membrane and release acetylcholine
- Acetylcholine diffuses across synapse and binds to receptors on postsynaptic membrane
- Action potential/depolarisation of postsynaptic membrane
- Influx of sodium ions;
To prevent continuous generation of action potential in postsynaptic neurone.
