Nervous System- Co-ordination

Question 1

What is in the cell body of a neuron?

Answer 1

RER to produce neurotransmitters

Question 2

What is the function of a Dendron?

Answer 2

Carry nerve impulse to the cell body

Question 3

What does an axon do?

Answer 3

Carries the impulse away from the cell body

Question 4

What is the purpose of the Schwann cells and what does it produce?

Answer 4

To protect and provide insulation which makes the myelin sheath which increase speed of cell conduction

Question 5

Where are the Nodes of Ranvier?

Answer 5

They are between myelinated areas

Question 6

What is a nerve impulse?

Answer 6

The self propagating wave of electrical disturbance which travels along the surface of an axon

Question 7

What are the 4 characteristics of the resting potential?

Answer 7

1) 3Na+ ions move out for every 2K+ ions that move in
2) Most Na channels are closed
3) Most K channels are open
4) Na/K pump which requires ATP

Question 8

What are the characteristics of the action potential?

Answer 8

1) Temporary reversal of the charge of the membrane
2) Na+ channels open and K+ channels close
3) Na+ ions flood the axon, because Na+ ions are positively charged it becomes more positive inside the membrane

Question 9

Why does hyperpolarisation occur?

Answer 9

Due to an overshoot of K+ ions

Question 10

Which factors increase the speed of an impulse?

Answer 10

1) The myelin sheath- prevents the potential forming in myelinated areas so the potential is forced to the Nodes of Ranvir (Salutatory Conduction)
2) Diameter- greater the diameter of the axon the greater the speed of conduction
3) Temperature- higher temp means a faster nerve impulse. ATP for active transport utilises enzymes from respiration

Question 11

What is the refractory period?

Answer 11

The time period between 2 action potentials which is due to Na+ channels being temporarily closed.

Question 12

What are the 3 purposes of the refractory period?

Answer 12

1) Limits the number of action potentials
2) Produces discreet impulses
3) Ensures the action potential are unidirectional

Question 13

What is the structure of a synapse?

Answer 13

Presynaptic membrane which contains synaptic vesicles, synaptic cleft, post synaptic membrane which contain receptor sites

Question 14

What are the 2 functions of a synapse?

Answer 14

1) unidirectional action potential

2) filters out low level stimuli

Question 15

What happens when an action potential reaches the presynaptic membrane?

Answer 15

Neurotransmitters is released and fuses with presynaptic membrane, then the neurotransmitter crosses the cleft and binds to receptors at the postsynaptic membrane which generates a new action potential.

Question 16

What happens at the synapse?

Answer 16

1) The action potential reaches the presynaptic membrane causing Ca2+ channels to open and Ca2+ to move into the presynaptic area
2) Influx of Ca2+ causes presynaptic vesicles, containing ACh, to fuse with the presynaptic membrane and the neurotransmitter is released
3) ACh diffuses past the cleft to the postsynaptic membrane
4) ACh binds to ACh receptors at the postsynaptic membrane which causes Na+ channels to open
5) Influx of Na+ generates new action potential

Question 17

What is required to reform Acetyl and Choline?

Answer 17

ATP released by mitochondria

Question 18

What are the differences between the hormonal and nervous system?

Answer 18

Hormonal
1) Chemicals
2) Transmitted by blood
3) Slow
4) General- travel to all areas of the body but target specific organs
5) Wide spread response
6) Irreversible
Nervous
1) Nervous impulses 
2) Transmitted by neurones
3) Fast
4) Specific- travels to specific areas of the body 
5) Localised response 
6) Reversible 
7) Effect is more intense

Question 19

What are 2 examples of chemical mediators?

Answer 19

1) Histamine- causes dilation of blood vessels and increases permeability of capillaries
2) Prostaglandin

Question 20

What is a neuromuscular junction (NMJ)?

Answer 20

Where a neurone meets a muscle

Question 21

What are the key difference between NMJ and cholinergic synapse?

Answer 21

1) NMJ’s are only excitatory
2) NMJ only between neurone and muscle
3) NMJ has no threshold value
4) NMJ’s have no summation

Question 22

How is a resting potential maintained?

Answer 22

1) 3 Na+ out, 2 K+ in using Na/K pump
2) Creates a chemical gradient which makes Na+ try to re-enter the axon and K+ to leave
3) Na+ channels are closed, K+ channels are open
4) K+ moves out which causes a more positive environment
5) K+ ions move back into the axon until an equilibrium is formed
6) No more net movement and electrical gradient becomes balanced