Describe the basic sequence of events that occurs at the neuromuscular junction and in the muscle cell during excitation and excitation-contraction coupling
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The action potential triggers the exocytosis of neurotransmitters stored in vesicles in the axon ending. This acetylcholine binds to receptors in the motor end plate, increasing the muscle membrane permeability to sodium. Acetylcholinesterase destroys the acetylcholine, ensuring that each nerve action potential produces only a single twitch. The influx of these positive sodium ions triggers an action potential. The action potential spreads in both directions away from the end plate across the entire surface of the muscle fiber and into the interior via transverse tubules, triggering a pulse of calcium ion release from the sarcoplasmic reticulum, which generates a brief small twitch. With additional stimuli, calcium ion builds up and higher tensions are produced.
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A 58-year-old woman complains of loss of urine when coughing and sneezing, and during exercise. She has had three children. Describe the possible causes of urinary incontinence in this patient
What will be an ideal response
The long bone growth-promoting effects of growth hormone are mediated by __________.
A. somatostatin B. somatotrophs C. somatomedins D. insulin
Which describes the all-or-none law as it relates to muscle function?
A. All fibers in a motor unit contract or none of them do. B. All fibers in a fascicle contract or none of them do. C. The whole muscle contracts or it does not. D. All myofibrils contract maximally or they do not contract at all.
Which of the following major events of prenatal development happens first?
A. Bone calcification begins. B. The central nervous system begins to form. C. The body is covered with downy hair. D. Meconium accumulates in the intestines. E. The eyes open fully.