Communication Between the Nervous System and Skeletal Muscles Sabrina Barner, Abbe Carlin, Amber Weigle

Neuromuscular Junctions Communication link between nervous system and skeletal muscle fiber Specialized intercellular connection Each skeletal muscle fiber is controlled by a nerve cell Motor neuron Axon Terminal: the somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells Cytoplasm of the axon terminal contains mitochondria and vesicles filled with acetylcholine(ACh) Synaptic cleft: narrow space which separates the axon terminal from the sarcolemma

Neuromuscular Junctions Cont. Motor end plate contains receptors that bind ACh Acetylcholinesterase (an enzyme) that both the synaptic cleft and the motor end plate contain AChE Action potential: neurons control skeletal muscle fibers by stimulating the production of this

The Contraction Cycle Link between the generation of an action potential in the sarcolemma and the start of a muscle contraction which occurs at the triads The passage of the action potential along T tubules triggers the massive release of calcium ions from terminal cisternae The presence of calcium ions begins muscle contractions

Checkpoint Questions Describe the neuromuscular junction. -Communication link between nervous system and skeletal muscle fiber How would a drug the blocks acetylcholine release affect muscle contraction? -There would be no changes in the sarcolemma and there would be no contraction in the muscle fiber. What would you expect to happen to a resting skeletal muscle if the sarcolemma suddenly became very permeable to calcium ions? -It would constantly be contracted and would inhibit the muscle from relaxing completely