All the components of the nodal tissue are autoexcitable. Why does the SA node act as the normal pacemakar?
- SA node has the lowest rate of depolarisation.
- SA node is the only component to generate the threshold potential.
- Only SA node can convey the action potential to the other components.
- SA node has the highest rate of depolarisation.
The Correct Option is D
Approach Solution - 1
Approach Solution -2
Ans: SA nodes can act as the normal pacemaker because it has the highest rate of depolarization. The change in the electrical potential across the cell membrane is called depolarization, which will eventually lead to generation of action potential. This action potential will cause the muscle to contract. Thus on depolarization heart muscles contract and therefore pumping of the blood. SA nodes have the highest depolarization rate because their cells have the ability to automaticity. This allows the cells to generate action potentials spontaneously. The SA nodes also have ion channels thus help the cells to reach the threshold much faster.
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Concepts Used:
Circulatory Pathways
Virtually every cell, tissue, organ, and system in the body is impacted by the circulatory system.
- Digestive - Absorbs nutrients and water; delivers nutrients (except most lipids) to liver for processing by hepactic portal vein; provides nutrients essential for hematopoiesis and building hemoglobin.
- Endocrine - Delivers hormones: atrial natriuretic hormone (peptide) secreted by the heart atrial cells to help regulate blood volumes and pressures; epinephrine, ANH, angiotensin II, ADH, and thyroxine to help regulate blood pressure; estrogen to promote vascular health in women and men.
- Integumentary - Carries clotting factors, platelets, and white blood cells for homeostatis, fighting infection, and reparing damage; regulates temperature by controlling blood flow to the surface, where heat can be dissipated; provides some coloration of integument; acts as a blood reservoir.
- Muscular - Provides nutrients and oxygen for contraction; removes lactic acid and distributes heat generated by contraction; muscular pumps aid in venous return; exercise contributes to cardiovascular health and helps to prevent atherosclerosis.