SEHS Topic 4.1 Neuromuscular
Function
Label a diagram of a motor unit
• Foundation required:
• A motor unit is made up of a motor neuron and all
of the skeletal muscle fibers innervated by that
axon.
• What’s neuron?
• It’s the functional unit of the nervous system (a.k.a.
a nerve cell)
Cont’d
• http://www.getbodysmart.com/ap/muscletissue/ne
rvesupply/motorunit/tutorial.html
• The large and complex terminal formation by which
the axon of a motor neuron establishes synaptic
contact with a striated muscle fiber
Cont’d
• Label this: use the following word bank: tranverse(t)
tubule; axon; synaptic vesicle containing neurotransmitters;
synapse; sarcolemma; motor end plate; sarcoplasmic
reticulum; neuromuscular junction
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Explain the roles of neurotransmitters (NTs) in
stimulating muscle contraction
What are neurotransmitters (NTs)?
Endogenous chemicals that transmit signals from a
neuron to a target cell across a synapse.
They are packaged into synaptic vesicles clustered
beneath the membrane in the axon terminal, on the
presynaptic side of a synapse.
They are released into and diffuse across the
synapse (a.k.a. synaptic cleft), where they bind to
specific receptors in the membrane on the
postsynaptic side of the synapse
Cont’d
• The key NTs for skeletal muscle contraction include”
• Acetylcholine (ACh) and cholinesterase
• In the peripheral nervous system,
acetylcholine activates muscles, and
is a major neurotransmitter in the
autonomic nervous system.
• When acetylcholine binds to acetylcholine receptors on
skeletal muscle fibers, it opens gated sodium channels in
the cell membrane.
• Sodium ions then enter the muscle cell, initiating a
sequence of steps that finally produce muscle contraction.
Cont’d
• So what happens after a motor neuron has been
stimulated by Ach?
• In biochemistry, cholinesterase is a family of
enzymes that catalyze the hydrolysis of the
neurotransmitter acetylcholine into choline and
acetic acid, a reaction necessary to allow a
cholinergic neuron to return to its resting state
after activation
Cont’d: it essentially terminates
synaptic trasmission
• It is also know as a: degradation enzyme
Explain how skeletal muscle contracts by the SLIDING
FILAMENT THEORY
• Foundation 1:
• Muscle structure (review in part):
Cont’d: functional contractile unit: the
sarcomere
Animations
• http://www.youtube.com/watch?v=EdHzKYDx
rKc
• http://www.liquidjigsaw.com/science/animati
on/animations/bigpicture/musclecontraction.html
Explain how slow and fast twitch muscle fibers differ
in structure and function
• Most of us have a 50%-50% make-up of slow vs. fast
twitch muscle fibers. Some of their functions and
features are shown below and on the next slide.
Cont’d – A more inclusive table
• Exercise/sports
types:
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