Neuromuscular Physiology

Question 1

Outline the gross anatomy of a neuron.

Answer 1

Dendrites, soma, axon hillock, axon, axon terminal, synapses.

Question 2

What is anterograde transport? What facilitates it?

Answer 2

Outward movement from the cell body.

Kinesin

Question 3

What is Retrograde transport? What facilitates it?

Answer 3

Movements from axon to cell body.

Dynein

Question 4

Outline the different sections of an action potential.

Answer 4

Resting membrane potential -70mV. Established by Sodium/Potassium pump.
Threshold potential -55mV.
Depolarisation - Sodium influx
Repolarisation - Potassium efflux
Hyperpolarisation - Delayed closing of potassium channels

Question 5

How is depolarisation propagated along the axon?

Answer 5

The sodium influx during depolarisation causes neighbouring voltage-gated sodium channels to open.

Question 6

Describe the two different types of synapses? Describe their properties.

Answer 6

Electrical - Gap junctions (formed by connexin proteins). Bidirectional. Movement of ions and small molecules.
Chemical - Axodendritic, Axosomatic and axoaxonic and all different classes.

Question 7

Outline the process that facilitates the transmission of signals across the neuromuscluar junction.

Answer 7

1. Action potential propagated to terminal buton
2. Voltage-gated calcium channels open, calcium influx
3. Exocytosis (SNARE proteins mediate vesicle fusion)
4. Potassium efflux to restore resting membrane potential of end bulb
5. Ach binds to Ach receptors triggering opening of ligand-gated sodium channels
6. Sodium influx
7. Ach broken down into acetate and choline

Question 8

Explain and give examples of the different V and T SNARE proteins.
What mediates the joining of snare proteins?

Answer 8

V-SNARE - Attach to vesicle. 
-Synaptobrevin
-Synaptotagmin
T-SNARE - Attach to cell membrane
-Snap-25
-Syntaxin
Calcium mediates the joining of SNARE protiens.

Question 9

Outline the process of muscle contraction.

Answer 9

8. Muscle action potential travels along transverse tubule. This opens calcium releasing channels in SR and triggers an influx of calcium ions into the sarcoplasm
9. Calcium binds to troponin, exposing binding sites for myosin
10. Myosin heads bind to actin to initiate power stroke
11. Calcium release channels in the SR close and calcium active transport pump uses ATP to restore calcium in SR.

Question 10

List the broad categories of neurotransmitters.

Answer 10

Amino acids
Amines
Peptides
(ACh is an exception, formed by Acetyl-CoA and Choline)

Question 11

Where are cholinergic neurons found? How is ACh produced?(Include equation) Which enzyme is required for this process to occur?

Answer 11

All motor neurons in the spinal cord and brainstem.
Choline acetyltransferase is the enzyme required to synthesise ACh.
Acetyl-CoA + Choline > Acetylcholine

Question 12

Which neurotransmitters bind to catecholaminergic neurons? What are they all derived from?

Answer 12

Dopamine, noradrenaline, adrenaline.

All derived from tyrosine

Question 13

Which neurotransmitter binds to serotonergic neurons? What is this substance derived from?

Answer 13

Serotonin.

Derived from tryptophan.

Question 14

Give examples of neurotransmitters that bind to amino acidergic neurons? Are the excitatrory or inhibitory?

Answer 14

Glutamate - Excitatory, memory, highly toxic

GABA - Inhibitory

Question 15

Describe the action of cocaine.

Answer 15

Causes a blockage of dopamine reuptake transporters, causing an accumulation of dopamine in the synaptic cleft.

Question 16

Describe the action of Botox.

Answer 16

Cuts SNARE proteins, so neurotransmitters cannot be released and the connected muscle cannot contract.

Question 17

List and describe the four tools used for taking measurements in Neuromuscular Physiology.

Answer 17

Dynamometer - Force/Strength (Newtons). Absolute or relative values.
Magnetic stimulation - Target areas of central control.
Electrical stimulation
Electromyography - Recording changes in electrical potential of a muscle. Surface or intramuscular.

Question 18

What is the m wave and what is it used for?

Answer 18

The compound muscle action potential.

Used to assess peripheral properties of the neuromuscular system.

Question 19

What measurements can be taken?

Answer 19

Excitability:
-M wave amplitude
-M wave area
Contractility:
-Twitch force
-Time to peak twitch
-Half relaxation time
-Electromechanical delay
Voluntary Activation:
-Measure superimposed twitch and pertentiated twitch and take a ratio of the two. (1-(STW-PTW))x 100