19,20-Neural regulation

Question 1

Skeletal muscle contraction ?

Answer 1

requires neurogenic innervation
incoming action potential (AP) from spinal cord-skeletal muscle
Motor unit: consists of one motor neuron & all the muscle fibres it innervates:
o Motor unit number & size varies: e.g. there are many, small motor units
found in muscles requiring fine control (e.g. eye movement muscles).

Question 2

Motor neuron ?

Answer 2

Motor neuron axon forms many branches with ‘bulbous swellings’:
sometimes called synaptic end bulbs, synaptic knobs, terminal boutons…

Question 3

Skeletal muscle: the neuromuscular junction and the (corresponding) motor end-plate ?

Answer 3

Skeletal muscle plasma membrane (sarcolemma) in the area of the NMJ is
called the motor end-plate (MEP), aka the postsynaptic membrane:
o MEP appears as depressions in the (modified folds of the) sarcolemma

Question 4

Neuromuscular junction at skeletal uscle ?

Answer 4

point of contact between the motor
neuron axon terminal and the muscle fibre: Axon terminal = presynaptic membrane.
Contains mitochondria and synaptic vesicles (acetylcholine).
NMJ rests in an invagination of the sarcolemma, i.e. MEP:
o MEP = postsynaptic membrane.
o Ligand-gated ion channels are expressed here; specifically,
nicotinic acetylcholine receptors (nAChRs).
* Similar to neuronal synapses, space between pre- and postsynaptic
membranes (in skeletal muscle) is called the synaptic cleft.