Cardiac activities of the heart are regulated by:A. Nodal tissueB. A special neural centre in the medullaoblongataC. Adrenal medullary hormonesD. Adrenal cortical hormonesChoose the correct answer from the options givenbelow:
Answer
Regulation of Cardiac Activities
The activities of the heart are regulated by a combination of neural, muscular, and hormonal mechanisms to maintain proper heart rhythm and function.
1. Nodal Tissue (Intrinsic Regulation)
This tissue is responsible for initiating and coordinating the heartbeat.
- SA Node (Sinoatrial Node): Located in the right atrium, acts as the natural pacemaker by initiating impulses that trigger atrial contraction.
- AV Node (Atrioventricular Node): Receives impulses from the SA node and delays them to allow complete atrial contraction before ventricles contract.
- Bundle of His and Purkinje Fibers: Conduct impulses rapidly to the ventricular muscle, ensuring synchronized contraction of both ventricles.
2. Medulla Oblongata (Neural Regulation)
- Houses the cardiac control center which regulates heart rate and force.
- Receives input from baroreceptors and chemoreceptors to adjust cardiac output.
- Modulates heart activity via:
- Sympathetic nervous system: Increases heart rate and force of contraction.
- Parasympathetic nervous system (via vagus nerve): Slows down heart rate.
3. Adrenal Medullary Hormones (Hormonal Regulation)
- The adrenal medulla releases:
- Adrenaline (epinephrine)
- Noradrenaline (norepinephrine)
- These hormones:
- Increase heart rate
- Enhance the strength of contraction
- Prepare the body during stress or emergency (fight or flight response)
Summary
Cardiac function is finely tuned through the coordination of: nodal tissue (electrical impulses), the medulla oblongata (neural control), and hormonal signals (adrenal secretions).