Nervous Coordination

Question 1

What does the nervous system include

Answer 1

Detection of stimuli by receptors
Transmission of nerve impulses by neurones
Response by effectors

Question 2

Dendrites

Answer 2

Forms connections with other neurones

Question 3

Axon

Answer 3

Long extension of neurone that transmits impulses

Question 4

Myelin sheath

Answer 4

Electrical insulation and speeds up transmission

Question 5

Schwann cell

Answer 5

Produces myelin sheath

Question 6

Terminal end branch

Answer 6

Impulses can be transmitted to other neurones

Question 7

Resting potential

Answer 7

At rest when there is no nerve impulse there is potential difference of -70mv across axon membrane
Membrane is polarised - maintaining potential difference between the two axis

Question 8

Na+/k+ pump

Answer 8

3 na+ move out and 2k+ move in
This requires energy from atp

Question 9

What happens at resting potential

Answer 9

Na+ channel is closed
Na+ pumped out the cell and cannot diffuse back in
Some k+ channels are open so some k+ can diffuse back out

Question 10

Action potential

Answer 10

Resting potential is maintained until membrane is disturbed
Action potential occurs when threshold is reached and becomes depolarised
-70mv to +40mv in seconds

Question 11

Depolarisation

Answer 11

If threshold is reached all na+ channels open
Na+ rapidly diffuse into the cell
Inside of cell more positive - depolarisation
K+ channels remain closed

Question 12

Repolarisation -3

Answer 12

Na+ channels close and k+ open
K + diffuse out

Question 13

Hyperpolarisation

Answer 13

K+ channels remain open for longer than needed
So cell more negative about -90mv
Sodium potassium pump restores to -70mv

Question 14

All or nothing

Answer 14

Minimum intensity of stimulus is called threshold
Threshold not reached then no action potential will occur
Above threshold full action potential occurs

Question 15

Refractory period

Answer 15

The time taken to restore the resting potential

Question 16

Myelin sheath efficiency

Answer 16

With myelin sheath impulse can jump from node of ranvier to node of ranvier so impulses are quicker and doesn’t have to travel full length of axon

Question 17

Temperature affecting impulse

Answer 17

High temp increases kinetic energy so increases rate of diffusion therefore increasing rate of conduction

Question 18

Synapse process

Answer 18

When action potential arrives at synaptic knob it causes ca2+ channels in presynaptic membrane to open
Ca2+ diffuse into synaptic knob by facilitated diffusion as higher conc of ca2+ in the tissue fluid
Ca2+ enzymes can cause synaptic vesicles to move towards presynaptic membrane
Vesicles fuse with presynaptic membrane and release acetylcholine by exocytosis this requires atp
Acetylcholine diffuses across cleft and bind to acetylcholine receptors on postsynaptic membrane as they’re complimentary
This causes na+ channels to open allowing na+ to diffuse in
If threshold is reached then membrane becomes depolarised and action potential occurs and spreads along axon
Enzyme hydrolyses acetylcholine into choline and ethanoic acid
Diffuse back across synaptic cleft
ATP released by mitochondria to resynthesise acetylcholine which is then stored in vesicles

Question 19

Important things about synapse

Answer 19

Will delay impulse slightly
Prevent the impulse from going in the wrong direction

Question 20

Neuromuscular junction

Answer 20

Synapse between a motor neurone and a muscle cell
Use acetylcholine which binds to nicotinic cholinergic receptors
Few differences:
-postsynpatic membrane has lots of folds to form clefts - increases surfaces area so more acetylcholine is hydrolysed at a faster rate
-postsynaptic membrane has more receptors that other synapse
- when a motor neurone fires an action potential it always triggers a response in a muscle cell

Question 21

Summation

Answer 21

Involves build up of neurotransmitter within the synapse

Question 22

Spatial summation

Answer 22

More than one neurones converge at one synapse
Action potential arrive from several different neurones at the synapse
Causes the release of enough neurotransmitters to reach threshold and cause an action potential in post synaptic neurone

Question 23

Temporal summation

Answer 23

One neurone but gives rapid impulses enough to depolarise post synaptic neurone

Question 24

Fatigue

Answer 24

Rate of transmitter release is higher than the rate at which it is reformed

Question 25

Excitatory neurotransmitters

Answer 25

Cause action potential in post synaptic neurone by making the resting potential less negative so less na+ to reach threshold

Question 26

Inhibitory neurotransmitters

Answer 26

Affect different receptors on postsynaptic neurone
Resting potential becomes hyperpolarised and postsynaptic membrane is less likely to reach threshold and generate action potential

Question 27

Effects of drugs on synapse

Answer 27

Can stimulate the nervous system
-creates more action potentials in postsynaptic neurone
-may bind to receptors on postsynaptic neurone
-may increase the release of neurotransmitters

2.can create fewer action potentials in the post synaptic neurone and have an inhibitory effect