Ch15 Nervous coordination

Question 1

Nervous system

Answer 1

1. nerve cells pass electrical impulses
2. secrete neurotransmitters
3. short-lived
4. fast
5. localised

Question 2

Hormonal system

Answer 2

1. produces chemicals transported by blood plasma
2. change in hormone concentration stimulate target cell receptors
3. long-lasting
4. wide-spread
5. slower

Question 3

Resting potential of axon

Answer 3

1. three Na+ actively transported out of axon
2. two K+ ions actively transported into axon
3. by sodium potassium pump
4. Na+ channels are closed - axon is less permeable
5. K+ ions diffuse out of axon through open channels
6. more negative inside axon

Question 4

Depolarisation

Answer 4

1. Stimulus reaches threshold value
2. Na+ channels open
3. Na+ diffuse into axon down electrochemical gradient
4. membrane becomes more permeable to Na+ ions
5. depolarisation occurs
6. inside axon becomes more positive (+40mv)

Question 5

Repolarisation

Answer 5

1. Potassium channels open
2. Potassium ions diffuse out
3. down electrochemical gradient
4. Sodium channels occur
5. repolarisation occurs

Question 6

Hyperpolarisation

Answer 6

1. Outward movement of K+ ions
2. Sodium channels close
3. Axon becomes more negative than usual

Question 7

All or nothing principle

Answer 7

Once stimulus reaches threshold value, all action potentials reach same charge

Question 8

Different protein channels

Answer 8

1. each protein has specific tertiary shape complementary to ions
2. ions have different shapes and charges

Question 9

Saltatory conduction

Answer 9

1. Myelin sheath is electrical insulator
2. Action potential jump from node to node (of Ranvier)
3. increases speed of conductance

Question 10

3 Factors affecting action potential speed

Answer 10

1. myelin sheath
2. diameter of axon
3. temperature

Question 11

Diameter of axon

Answer 11

1. greater diameter, faster speed of conductance
2. less ion leakage
3. membrane potential easier to maintain

Question 12

Temperature

Answer 12

1. higher temperature, faster speed of conductance
2. diffusion rate increases
3. proteins and enzymes involved(active transport and channels) can denature

Question 13

Refractory period

Answer 13

1. no NA+ ions can diffuse in because channels are closed
2. no new action potential can be produced

Question 14

Function of refractory period

Answer 14

1. Action potentials propagated in one direction only
2. discrete impulses
3. limits number of action potentials

Question 15

Transmission across cholinergenic synapse

Answer 15

1. depolarisation of presynaptic membrane
2. Calcium channels open and calcium ions enter synaptic knob
3. Synaptic vesicles fuse with presynaptic membrane
4. neurotransmitter(acetylcholine) released - exocytosis
5. diffuses across synaptic cleft
6. binds to receptors on postsynaptic membrane
7. sodium channels open, sodium ions enter
8. postsynaptic neurone is depolarised

Question 16

Recycling acetylcholine

Answer 16

1. acetylcholinterase hydrolyses acetylcholine
2. ethanoic acid and choline diffuse across synaptic cleft to presynaptic neurone
3. Sodium channels close in postsynaptic knob- no new action potentials
4. ATP reforms acetylcholine

Question 17

Spatial summation

Answer 17

1. different presynaptic neurones converging on one synapse
2. release enough neurotransmitter at same time to exceed threshold value
3. Action potential produced

Question 18

Temporal summation

Answer 18

1. One neurone release neurotransmitter many times over short period
2. Neurotransmitter accumulate to exceed threshold value
3. Action potential produced

Question 19

Mitochondria use

Answer 19

1. Maintain active transport ions in sodium potassium pump
2. Synthesis of neurotransmitter
3. Movement of vesicles
4. Synthesis of enzyme acetylcholinterase

Question 20

Unidirectionality

Answer 20

1. Synaptic vesicles with neurotransmitter only synthesised in presynaptic neurone
2. Neurotransmitter receptor only located at postsynaptic neurone
3. Neurotransmitter diffused down concentration gradient

Question 21

Inhibition

Answer 21

1. Neurotransmitter binds to receptor
2. K+ and Cl- channels open
3. K+ passes out and Cl- passes in
4. Membrane potential hyperpolarised
5. increased stimulation needed to reach threshold value
6. more Na+ required