Question

Norepinephrine

(i) is released by sympathetic fibers

(ii) is released by parasympathetic fibers

(iii) increases the heart rate

(iv) decreases blood pressure

• A. (ii) and (iii)
• B. (i) and (iii)
• C. (i) and (iv)
• D. (ii) and (iv)

Answer 1

The correct option is B

(i) and (iii)

The correct option is B:

Explanation for the correct option:

Statement (i)

1. Norepinephrine, generally known as noradrenaline, is a hormone and a neurotransmitter.
2. It's a pivotal element of our body's "fight-or-flight" response.
3. The substance norepinephrine, also known as noradrenaline, is released primarily from the terminals of sympathetic nerve fibres and operates to increase the force of skeletal muscle contraction as well as the pace and force of heart contraction.

Statement (iii)

1. The hormone norepinephrine (NE) can increase blood pressure and heart rate.

Explanation for the incorrect options:

Statement (ii):

1. Norepinephrine (NE) is released by the sympathetic nervous system, while acetylcholine is released by the parasympathetic nervous system (ACh).
2. Heart rate and myocardial contractility are both increased by sympathetic activation.

Statement (iv):

1. Vasoconstriction, or the narrowing of blood vessels, is promoted by norepinephrine.
2. Blood pressure rises as a result of this. Norepinephrine stimulates alpha-adrenoreceptors in blood vessel cells, the same as epinephrine.
3. It raises blood sugar levels and boosts heart rate.

Final answer: Norepinephrine is released by sympathetic fibres and increases the heart rate.