About autonomic functions: a. The autonomic nerves don't initiate activity in smooth muscles but rather modify it .b. The muscarinic action of acetylcholine is produced by parasymp. Pregang nerve fibres.c. Injection of atropine leads to slowing of the heart rate (bradycardia).d. Epinephrine & norepinephrine blood concentrations are equale. Sympathetic stimulation accelerates fatigue of skeletal muscles.
Question
About autonomic functions: a. The autonomic nerves don't initiate activity in smooth muscles but rather modify it .b. The muscarinic action of acetylcholine is produced by parasymp. Pregang nerve fibres.c. Injection of atropine leads to slowing of the heart rate (bradycardia).d. Epinephrine & norepinephrine blood concentrations are equale. Sympathetic stimulation accelerates fatigue of skeletal muscles.
Solution
a. Partially correct. The autonomic nervous system (ANS) does not initiate activity in smooth muscles, but it can modify it. However, it's important to note that the ANS can also initiate activity in some cases, such as in the heart where it can initiate a heartbeat.
b. Correct. The muscarinic action of acetylcholine is indeed produced by parasympathetic preganglionic nerve fibers. These fibers release acetylcholine, which then binds to muscarinic receptors on the target organ.
c. Incorrect. Atropine is a muscarinic antagonist, meaning it blocks the action of acetylcholine at muscarinic receptors. This would lead to an increase in heart rate (tachycardia), not a decrease (bradycardia).
d. Incorrect. The concentrations of epinephrine and norepinephrine in the blood are not equal. Epinephrine is typically found in higher concentrations than norepinephrine.
e. Incorrect. Sympathetic stimulation does not necessarily accelerate fatigue of skeletal muscles. While it does increase the rate of energy use, it also increases the delivery of oxygen and nutrients to the muscles, which can help to delay fatigue.
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