FAQs on Nodal Tissues in Heart : SA , AV nodes - Body Fluids and circulation, Biology, Class 11

Question 1

1. What are the functions of the SA and AV nodes in the heart?

Accepted Answer

Ans. The SA (sinoatrial) node is responsible for initiating the electrical impulses that regulate the heart's rhythm. It acts as the natural pacemaker of the heart. The AV (atrioventricular) node, on the other hand, serves as a relay station for the electrical signals from the atria to the ventricles. It delays the transmission of the impulses, allowing the atria to contract before the ventricles, ensuring efficient blood pumping.

Question 2

2. How do SA and AV nodes contribute to the coordination of heart contractions?

Accepted Answer

Ans. The SA node generates electrical impulses that spread through the atria, causing them to contract simultaneously. The impulses then reach the AV node, where they are delayed for a short period. This delay allows the blood to move from the atria to the ventricles before the ventricles contract. Once the impulses are transmitted through the AV node, they travel through specialized fibers called bundle of His and Purkinje fibers, stimulating the ventricles to contract in a coordinated manner.

Question 3

3. What happens if the SA node fails to function properly?

Accepted Answer

Ans. If the SA node fails to function properly, it can result in a condition called sinus node dysfunction or sinus node dysfunction. This may cause the heart to beat too slowly (bradycardia), irregularly, or even stop beating altogether (asystole). In such cases, an artificial pacemaker may be required to regulate the heart's rhythm and ensure proper blood flow.

Question 4

4. How are the SA and AV nodes influenced by the autonomic nervous system?

Accepted Answer

Ans. The autonomic nervous system plays a crucial role in regulating the activity of the SA and AV nodes. The sympathetic nervous system, under conditions like stress or exercise, releases norepinephrine, which increases the heart rate by stimulating the SA node. On the other hand, the parasympathetic nervous system, during periods of rest, releases acetylcholine, which slows down the heart rate by inhibiting the SA node. The AV node is also influenced by these autonomic signals, regulating the transmission of electrical impulses from the atria to the ventricles.

Question 5

5. What are some common disorders associated with SA and AV nodes?

Accepted Answer

Ans. Some common disorders associated with SA and AV nodes include:- Atrial fibrillation: This is an irregular and rapid heartbeat that originates from abnormal electrical signals in the atria. It can be caused by malfunctioning SA or AV nodes.- Heart block: This condition occurs when the electrical signals are delayed or blocked between the atria and ventricles, often due to a malfunctioning AV node.- Sinus node dysfunction: As mentioned earlier, this is a condition where the SA node fails to function properly, resulting in abnormal heart rhythms.

Nodal Tissues in Heart SA , AV nodes - Body Fluids and circulation, Biology,

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