lecture 8 - neuromuscular physiology

Question 1

what is the structure of a neuron?

Answer 1

dendrites, myelin sheath, soma (cell body), axon

Question 2

what is the function of a dendrite?

Answer 2

receive signals from other neurons – comm with each other, sends signals to other neurons

Question 3

what is the function of the soma?

Answer 3

contains nucleus and chemicals that are within the production of neurotransmitters

Question 4

what is the function of the axon?

Answer 4

Nerve fibre that carries nerve impulses away from the cell body to other neurons or tissues

Question 5

what is the function of the myelin sheath?

Answer 5

insulates axon and enhances transmission speed along the axon

Question 6

what does it mean if the resting membrane potential is more neg?

Answer 6

hyperpolarised

Question 7

what does it mean if the resting membrane potential is more pos?

Answer 7

depolarised

Question 8

what contributes to the polarised resting membrane potential?

Answer 8

Ions cannot pass freely through the cell membrane, and instead use specialised channel proteins providing a “tunnel” for ions to pass through.

Some channels, known as “leak channels”, are open in resting neurons. Others remain closed and only open in response to a signal.

In neurons, the resting membrane potential depends mainly on movement of potassium (K+) through potassium leak channels

Question 9

what is a ligand-gated ion channel?

Answer 9

Ion channels which open in response to neurotransmitter binding

Question 10

what is a voltage-gated ion channel?

Answer 10

Ion channels which open in response to a change in membrane potential (e.g. an increase in the charge of a neuron)

Question 11

what is a mechanically-gated ion channel?

Answer 11

Ion channels which open in response to mechanical stimulation (i.e. pressure)

Question 12

what is the action potential propagation?

Answer 12

wave of depolarisation spreads along the nodes of ranvier

Question 13

is glutamate excitatory or inhibitory?

Answer 13

excitatory - pos charged ions

Question 14

is gaba excitatory or inhibitory?

Answer 14

inhibitory - neg charged ions

Question 15

where is the motor cortex?

Answer 15

frontal lobe

Question 16

where do motor neurons send signals?

Answer 16

efferent - away from the ns

Question 17

where do sensory neurons send signals?

Answer 17

afferent - from the periphery to the ns

Question 18

where do interneurons send signals?

Answer 18

between neurons

Question 19

what is a slow-twitch motor units (type s)?

Answer 19

recruit a smaller number of type I, fatigue resistant muscle fibres. These are recruited first (i.e. at low forces).

Question 20

what are fast-twitch, fatigue resistant units (type FR)?

Answer 20

recruit a larger number of type IIa muscle fibres. These are recruited second (i.e. at moderate forces).

Question 21

what is fast-twitch fatigable units (type FF)?

Answer 21

recruit a large number of type IIx muscle fibres. These are recruited last (i.e. at high forces).

Question 22

what happens when a motoneuron is activated?

Answer 22

action potential spreads along the muscle fibre which makes a contraction

Question 23

what happens during nerve conduction velocity?

Answer 23

When a nerve signal passes it travels at a certain velocity – differs between individuals – maj of normal individuals fall within defined ranges
Arm into cold water, take out cold water and measure nerve conduction velocity, Stimulate nerve at 2 diff sites – measure response elicit vis electromyography – measures the nerve conduction velocity

Question 24

what are the effects of cold on nerve conduction velocity?

Answer 24

Action potential takes longer to initiate and spread along the nerves

Question 25

what are the mechanisms of force graduation?

Answer 25

increase in motor unit recruitment (spatial summation), Increase in discharge frequency, termed rate coding
(temporal summation)

Question 26

what is the myotatic reflex arc?

Answer 26

1) Muscle spindles detect dynamic stretch induced via percussion of the tendon

1) Muscle spindles detect dynamic stretch induced via percussion of the tendon

3) Ia afferents synapse with homologous a-motoneuron monosynaptically, thereby activating the quadriceps motoneuron

4) Concurrently, the Ia afferent synapses with an inhibitory interneuron which in turn synapses with the antagonist muscle, thereby inducing relaxation in he hamstrings. This is known as reciprocal inhibition.

5) This response induces shortening of the quadriceps, thereby preventing excessive stretch