AnS 214 SI Session 10
Monday, 9/28, 7pm
A. Motor Units
1) Sarcomeres are the functional contractile unit of the myofiber. Adding sarcomeres in ______generates force, while adding sarcomeres in ______allows for flexibility. A motor unit is comprised of a ______and all the ______it innervates. During a contraction, ______motor units are recruited first, while ______motor units are recruited last.
The muscle fibers innervated by a single nerve are ______throughout the cell. This is referred to as a ______configuration. With age, ______myofibers degenerate. Viable nerves pick up de-innervated fibers, causing motor unit size to ______. As a result, ______motor function decreases.
2) Small motor units generally recruit what kind of fibers?
Large motor units?
3) Type I fibers are also called ______.
Type II fibers are also called ______.
B. Neuromuscular Junction
Fill in the diagram at right and answer the pertaining questions.
1) What is the name of the neurotransmitter released at the NMJ?
2) What kinds of channels will this neurotransmitter open on the sarcolemma?
3) What major enzyme is present within the synaptic cleft?
What is its function?
4) What is the significance of the junctional folds?
5) What is the significance of the Schwann cell surrounding the synaptic knob?
6) What kinds of receptors are located in the junctional folds?
7) What kinds of channels do they open?
8) What does this ion exchange initiate?
C. Myofiber Excitation
Fill in the blanks on the diagram below.
1) What kinds of channels are located at A? Describe the consequences of their activation.
2) Draw the path of the end plate potential along the sarcolemma. What structure does it enter?
3) What is the effect of the spreading potential on the structure labeled C?
D? Draw an arrow symbolizing any structural changes?
4) What particles are stored within the structure labeled B? What happens as a result of the conformational change to structure D?
5) What kinds of channels are located at B? Why do the intra-SR ions flood the cell?
6) What is the effect of these ions in the sarcoplasm?
7) What protein is responsible for returning calcium to the SR?