Question: 112. Cardiac activities of the heart are regulated by:
A. Nodal tissue
B. A special neural centre in the medulla oblongata
C. Adrenal medullary hormones
D. Adrenal cortical hormones
Choose the correct answer from the options given below:
(1) A, B and C Only.
(2) A, B, C and D
(3) A, C and D Only
(4) A, B and D Only
Answer: Option (1)
Explanation:
The rhythmic contraction and relaxation of the heart are mainly controlled by specialized cardiac tissues and nervous and hormonal regulation.
The nodal tissue of the heart, which includes the sinoatrial node and atrioventricular node, acts as the pacemaker and directly regulates heart rate and rhythm.
The cardiac control centre present in the medulla oblongata regulates heart activity through the autonomic nervous system by sending sympathetic and parasympathetic impulses.
Adrenal medullary hormones such as adrenaline and noradrenaline increase heart rate and force of contraction during stress or excitement.
Adrenal cortical hormones like aldosterone and cortisol do not directly regulate cardiac rhythm or cardiac activity.
Therefore, cardiac activities of the heart are regulated by A, B and C only.