Lab 3: Skeletal muscle contraction

Question 1

motor unit

Answer 1

motor neuron and all the muscle fibres it innervates

Question 2

difference between motor unit recruitment experimentally and in body

Answer 2

exp = bigger motor units first bc bigger diameter so faster conduction velocity (stimulus sideways to nerve)
body = smaller units first because smaller axon hillock so less ions needed

Question 3

muscle fibre types in EDL vs soleus

Answer 3

soleus = postural -> primarily slow twitch (type I)
EDL = for power -> primarily fast twitch (IIB)

Question 4

experimental results in EDL vs soleus

Answer 4

soleus = tetanus at lower frequency, but smoother and maintained for longer
EDL = faster to peak, fatigues quickly

Question 5

why differences between fibre types (7)

Answer 5

• RyR density,
• myosin type,
• SERCA pump,
• energy production type (w or w/o O2),
• mitochondria density,
• oxidative enzymes,
• myoglobin

Question 6

MG testing

Answer 6

repetitive stimulation = decrease in EMG amplitude bc less nAChR at NMJ

Question 7

MG treatment

Answer 7

AChE blocker so more ACh stays in synapse -> more likely to bind to receptor -> more likely to cause AP