[010] Neuromuscular junction

Question 1

Which muscle has polyneural connections (remain innervated by multiple fibres after birth)

Answer 1

extra-occular muscles

Question 2

What is a motor unit

Answer 2

Number of Muscle Fibres contacted by a single Motor Neuron

AKA Number of Terminal branches/Nerve Terminals of a Motor Neuron

Question 3

What does the size of a motor unit determine?

Answer 3

precision of movement

eg
temporalis muscle motor unit size ~500
extra-occular muscle motor unit size ~5, allows for fine control of movement

Question 4

What is a neuromuscular junction comprised of

Answer 4

• a nerve terminal where ACh can be released
• folded and highly specialised post-synaptic Sarcolemma (Motor End Plate) on the Muscle Fibre, where AChRs are localised to.

Question 5

motor end plate

Answer 5

region of muscle fibre where nerve terminal contacts muscle

Question 6

what channels are found at the base of motor end plate folds
what are their functions

Answer 6

voltage-gated Na+ channels
- initiate muscle action potential and causes muscle fibre to twitch