Question

Rate of heart beat is under the control of
A) Autonomic nervous system
B) Vagus nerve
C) Glossopharyngeal nerve
 D) None of the above

Answer 1

Hint:The normal activities of the heart are regulated intrinsically that is auto regulated by specialised muscles (nodal tissue) hence the heart is called myogenic. This autonomic rhythm is produced by spontaneous depolarization which leads to contraction of heart.

Complete answer:
Heart is a muscular organ which helps in pumping of the blood throughout the body. Heart rate can be defined as the speed at which heart beats per minute. The normal or average heart beat per minute is 72.
A special neural centre in the medulla oblongata located in the brain can modulate the cardiac function through autonomic nervous system (ANS).

Autonomic nervous systems consist of two antagonistic components- Sympathetic and Parasympathetic nerves which are connected to the heart and modify the rate of spontaneous depolarization of the SA node.

Sympathetic nerves release noradrenaline which stimulates the SA node that accelerates the heart beat, the strength of ventricular contraction and thereby the cardiac output. On the other hand, parasympathetic nerve endings release acetylcholine which decreases the rate of heartbeat speed of conduction of action potential and thereby the cardiac output.

Let us look into the given options
>Option A : The Autonomic Nervous System has both sympathetic and parasympathetic divisions that work together to maintain balance. inducing the force of contraction of the heart, peripheral resistance of blood vessels and the heart rate. Therefore, this is the correct answer.
>Option B : The vagus nerve is the main component of the parasympathetic nerve. This nerve is involved in the regulation of internal organ functions, such as digestion, and respiratory rate. It also stimulates certain muscles in the heart partially that help to slow heart rate. Therefore, this is an incorrect answer.
>Option C : The glossopharyngeal nerve provides sensory innervation which provides taste and Motor innervation to the mucous membrane and muscle of the pharynx which is responsible for swallowing. Therefore, this is an incorrect answer.
>Option D : As the correct option is given above. Therefore, this is an incorrect answer.
Hence the correct answer is option ‘A’.

Note:The various factors affecting heart rate are,
i) During anxiety the heart increases
ii) Age
iii) Medications
iv) Diet and fitness levels