Synaptic transmission (15)

Question 1

What is the purpose/function of synapses?

Answer 1

electrical impulses cannot travel over the junction between neurons so neurotransmitters send impulses between neurons from neurons to effectors, the new impulses can be initiated in several different neurons for multiple simultaneous responses

Question 2

Draw and label the structure of a synapse.

Answer 2

look at notes.

Question 3

What are the 3 steps that happen in a presynaptic neurone when an action potential is transmitted from one neuron to another?

Answer 3

1) wave of depolarisation travels down presynaptic neuron, causing voltage-gated calcium ion channels to open
2) vesicles move towards and fuse with the presynaptic membrane
3) exocytosis of neurotransmitter into synaptic cleft

Question 4

How do neurotransmitters cross the synaptic cleft?

Answer 4

via simple diffusion

Question 5

Why is synaptic transmission unidirectional?

Answer 5

only the presynaptic contains vesicles of neurotransmitters and only the postsynaptic membrane has complementary receptors

Question 6

What are the 3 steps that happen in a postsynaptic neuron when an action potential is transmitted?

Answer 6

1) neurotransmitter binds to specific receptor on postsynaptic membrane
2) sodium ion channels open
3) if influx of sodium ions raises the membrane to threshold potential an action potential is generated

Question 7

What is summation?

Answer 7

when neurotransmitters from several sub-threshold impulses accumulate to generate an action potential

Question 8

What are the 2 types of summation?

Answer 8

temporal
spatial

Question 9

Where does summation not occur?

Answer 9

at neuromuscular junctions

Question 10

What is temporal summation?

Answer 10

when 1 presynaptic neuron releases neurotransmitter several times in quick succession

Question 11

What is spatial summation?

Answer 11

when multiple presynaptic neurons release neurotransmitter at the same time

Question 12

What type of synapse uses acetylcholine as the primary neurotransmitter?

Answer 12

cholinergic synapse

Question 13

What do cholinergic synapses use and as what?

Answer 13

use acetylcholine as the primary neurotransmitter

Question 14

What 3 places are cholinergic synapses located at and for what?

Answer 14

1) motor end plate (muscle contraction)
2) preganglionic neurons (excitatory response)
3) parasympathetic postganglionic neurons (inhibitory response)

Question 15

What are the 3 steps that happen to acetylcholine from the synaptic cleft?

Answer 15

1) hydrolysis into acetyl and choline by acetylcholinesterase (AChE)
2) acetyl and choline diffuse back into presynaptic membrane
3) ATP used to reform acetylcholine for storage in vesicles

Question 16

What are the 2 importance’s of acetylcholinesterase (AChE)

Answer 16

• prevents overstimulation of skeletal muscle cells
• enables acetyl and choline to be recycled

Question 17

What are the 3 steps that happen in an inhibitory synapse?

Answer 17

1) neurotransmitter binds to and opens chloride channels on postsynaptic membrane, and triggers potassium ion channels to open
2) chloride moves in and potassium ions move out via facilitated diffusion
3) potential difference becomes more negative (this is hyperpolarisation)

Question 18

What is the structure of a neuromuscular junction?

Answer 18

synaptic cleft between a presynaptic neuron and a skeletal muscle cell

Question 19

What are 3 ways drugs decrease synaptic transmission?

Answer 19

• inhibit release of neurotransmitter
• decrease permeability of postsynaptic membrane to ions
• hyperpolarise postsynaptic membrane

Question 20

What are 2 ways drugs increase synaptic transmission?

Answer 20

• inhibit AChE
• mimic shape of neurotransmitter

Question 21

What are the 5 differences between cholinergic synapses and neuromuscular junctions?

Answer 21

postsynaptic cell
AChE location
action potential
response
neurons involved

Question 22

What is the difference between cholinergic synapses and neuromuscular junctions, in terms of postsynaptic cell?

Answer 22

CS - another neuron
NJ - skeletal muscle cell

Question 23

What is the difference between cholinergic synapses and neuromuscular junctions, in terms of AChE location?

acetylcholinesterase

Answer 23

CS - synaptic cleft
NJ - postsynaptic membrane

Question 24

What is the difference between cholinergic synapses and neuromuscular junctions, in terms of action potential?

Answer 24

CS - new action potential produced
NJ - end of neural pathway

Question 25

What is the difference between cholinergic synapses and neuromuscular junctions, in terms of response?

Answer 25

CS - excitatory or inhibitory
NJ - always excitatory

Question 26

What is the difference between cholinergic synapses and neuromuscular junctions, in terms of neurons involved?

Answer 26

CS - motor, sensory and relay
NJ - only motor