practical 6: EMG, reflexes, and human nerve conduction velocity results

Question 1

what does EMG stand for

Answer 1

electromyogram

Question 2

muscles are electronically connected to the spinal cord by _______ _________, which synapse at individual muscle fibres at a region called the neuromuscular junction

Answer 2

motor neurons

neuromuscular junction

Question 3

describe in detail what happens when the motor neuron is stimulated

Answer 3

depolarisation of the synaptic knob, opens ca2+ voltage gated calcium channels and we get calcium ion influx, triggering release of neurotransmitter acetylcholine from the presynaptic cell. the neurotransmitter diffuses across the neuromuscular junction where it binds to nicotinic receptors on the post synaptic muscle membrane . these receptors are coupled to sodium channels so Na+ diffuses into the muscle causing depolarisation of the membrane. if sufficient neurotransmitter is released, an action potential will be generated in the muscle fibre . spreads along muscle membrane initiating muscle contraction

Question 4

what is a motor unit

Answer 4

one or more muscle fibres supplied by a motor neuron

Question 5

the size of the motor unit depend on

Answer 5

the role of a particular muscle eg large muscles need larger motor units, so 100-120 muscle fibres

Question 6

describe the individual muscle fibres of skeletal muscle

Answer 6

multinucleated

striated due to regularly spaced myofibrils consisting of actin and myosin filaments

Question 7

excitable cardiac cells (myocytes) make up cardiac muscle which myogenic which means

Answer 7

they have the ability to beat without any nervous innervation

Question 8

a cardiac myocyte cell has been isolated from a whole heart by a collagenase enzyme, what is this

Answer 8

an enzyme that breaks down the proteins which holds the cells together

Question 9

what does ADM muscle of the hand stand for

Answer 9

abductor digiti minimi

Question 10

what nerve supplies the ADM muscle

Answer 10

ulnar

Question 11

how is a skeletal muscle able to produce different contraction strengths

Answer 11

frequency of action potentials are different

size and number of motor units

Question 12

how can we excite nerve fibres in the ulnar nerve

Answer 12

use the stimulating electrode

Question 13

for each stimulus current amplitude (mA) measure the

Answer 13

latency (time from stimulus to start of response)
duration of each individual response ( time from beginning of response to end of response)
peak response (change in mV from baseline to peak of` the response)

Question 14

what physical characterisitics of the nerve fibre affect its conduction velocity

Answer 14

myelination / diameter

Question 15

which other muscles are innervated by the ulnar nerve

Answer 15

abductor pollicis
opponens
flexor
1st dorsal and 1st palmer interosseous