Alpha-1 receptor stimulation causes:
a) Pupillary dilatation
b) Increased heart rate
c) Increased contractility
d) Increased gastric motility
Correct Answer: a
Explanation:
Apha-1 receptor causes
- Increased smooth muscles contraction, such as in arterioles where it increases TPR & so BP
- Increased pupillary muscle dilatation (mydriasis)
Increased heart rate (choice b)
& increased contractility (choice c) of heart, although a function of
sympathetic system, is not mediated by alpha-1 receptors rather it is mediated
by Beta-1 receptor stimulation in heart.
Also increased gut motility (choice
d) is purely a parasympathetic function.
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