When norepinephrine binds to adrenergic receptors,
A. Na+ channels open.
B. Ca2+ channels open.
C. adrenaline is released.
D. G proteins mediate the cell's response.
E. Na+ channels are closed.
D
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Which statement is not accurate about the absolute refractory period?
a. Another stimulus, regardless of its strength, cannot initiate another action potential during this period b. During this period, voltage-gated Na+ channels open, then close but are inactivated c. Immediately following this period, the membrane can experience another action potential if the stimulus is strong enough d. This period occurs during the after hyperpolarization phase of the action potential e. This period ensures a unidirectional spread of the action potential down a nerve fiber
The single most abundant chemical substance of the body, accounting for 60% to 80% of body weight, is ________.
A) oxygen B) protein C) water D) hydrogen
The cells that are formed during spermatogenesis by meiosis I are called
A) spermatogonia. B) primary spermatocytes. C) secondary spermatocytes. D) spermatids. E) sperm.
Which of the following is NOT true of corticospinal fibers?
A. They may synapse with afferent neurons in ascending pathways. B. They may synapse directly on gamma motor neurons. C. They may synapse directly on interneurons. D. They are collectively sometimes called the extrapyramidal system. E. They may synapse directly on alpha motor neurons.