How Nerves Work 5

Question 1

What is the neuromuscular junction?

Answer 1

Junction between the skeletal muscle and motor neuron

Question 2

Does the cell at the neuromuscular junction always or sometimes reach threshold when acetylcholine is released?

Answer 2

Always

Question 3

Why are there fold at the neuromuscular junction?

Answer 3

Allows more voltage gated Na⁺ channels to be closer to the ligand gated acetylcholine receptor so the graded potential doesn’t have far to go

Question 4

Why is acetylcholine removed afterwards?

Answer 4

To stop any spasms occuring as many action potentials are fired

Question 5

What is the process of an action potential being fired at the neuromuscular junction?

Answer 5

1. Action potential travls down motor neuron
2. Opens voltage gated Ca²⁺ channels in presynaptic terminal
3. Triggers fussion of vesicles (Ca²⁺ dependent exocytosis)
4. Acetylcholine is released
5. Diffuses across the synaptic cleft and binds to acetylcholine receptors
6. Opens ligand gated Na⁺/K⁺ channels
7. Evokes graded potential (end plate potential)
8. Always depolarises adjacent membranes to threshold
9. Opens voltage gated Na⁺ channels evoking a new action potential
10. Acetylcholine removed by acetylcholinesterase

Question 6

What is the process of synaptic transmission in the CNS?

Answer 6

1. Action potential releases terminal
2. Voltage gated Ca²⁺ channels open
3. Ca²⁺ enters axon terminal
4. Neurotransmitter released and diffusion
5. Neurotransmitter binds to post-synaptic receptors
6. Neurotransmitter removed from synaptic cleft

Question 7

What are some examples of neurotransmitters used in the CNS?

Answer 7

Acetylcholine
Noradrenaline
Dopamine
Serotonin
Histamine
Glutamine
GABA
Glycine
Peptide
ATP
Adenosine
Nitric oxide (not in vesicle as lipphillic, produced on deman)

Question 8

How does the neuromuscular junction and CNS differ in the neurostransmitters that they use?

Answer 8

CNS uses a range of neurotransmitters whereas theneuromuscular junction only uses acetylcholine

Question 9

How many receptors does each neurotransmitter have (one or several)?

Answer 9

Several

Question 10

What receptor does acetylcholine act on at the neuromuscular junction?

Answer 10

Nicotinic

Question 11

Do the CNS and neuromuscular junction both use a range of postsynaptic potentials?

Answer 11

No, the CNS uses a wide range (fast IPSP, slow IPSP, fast EPSP and slow EPSP) whereas the neuromuscular junction always depolarises

Question 12

What is the advantage of many small kinds of postsynaptic potentials?

Answer 12

Enables synaptic integration to use lots of information to determine if an action potential should be fired

Question 13

What are the different anatomical arrangements of synapses in the CNS?

Answer 13

Axo somatic (onto soma)

Axo dendritic (onto dendrite)

Axo axonal (onto terminal of other fibre)

Question 14

Which form of synaptic anatomical arrangement in the CNS usually produces the largest response?

Answer 14

Axo somatic (onto the soma)

Question 15

What are the two forms of synaptic connectivity?

Answer 15

Convergence

Divergence

Question 16

Where is synaptic connectivity used?

Answer 16

In the CNS

Question 17

What can synaptic connectivity be used for?

Answer 17

Feedback inhibition to stop a neuron from firing more than once

Question 18

What pathways of neurons can be found in the CNS?

Answer 18

Monosynaptic

Polysynaptic

Question 19

What do monosynaptic pathways look like?

Answer 19

Sensory - inter - motor

Question 20

What do polysynaptic pathways look like?

Answer 20

Lots of synapses between the sensory and motor

Question 21

Why is the CNS more complex than the neuromuscular junction?

Answer 21

Range of neurotransmitters

Range of postsynaptic potentials

Small potentials (use synaptic integration)

Variations of anatomical arrangements

Variations on connectivity of neuron

Question 22

How can the actions of drugs be explained by the mechanism of the NMJ?

Answer 22

They inhibity different aspects of it