Question

c. short answer

1. complete the chart below:

app - 6

1. heart produces heart sounds. write a note on heart sounds. (app - 3marks)

Explanation:

For the SA node:

• Function: It is the natural pacemaker of the heart. It initiates the electrical impulses that cause the heart to contract. The electrical signal starts in the SA node and spreads through the atria, causing them to contract and pump blood into the ventricles.
• Special feature: It has autorhythmicity (the ability to generate electrical impulses on its own without external nervous system stimulation). It sets the normal heart rate (around 60 - 100 beats per minute in adults).

For the Systematic Aorta:

• Function: It is the main artery that carries oxygen - rich blood from the left ventricle of the heart to the rest of the body. It branches into smaller arteries, arterioles, and capillaries to distribute blood to all tissues and organs.
• Special feature: It has a thick, elastic wall. The elasticity helps to maintain blood pressure by expanding during ventricular systole (when the heart contracts) and recoiling during ventricular diastole (when the heart relaxes).

For the Purkenji fibers:

• Function: They conduct the electrical impulses (that originated from the SA node, passed through the atrioventricular node, and the bundle of His) very quickly to the ventricular muscle cells. This ensures that the ventricles contract in a coordinated manner, starting from the apex (bottom) of the heart, which is efficient for pumping blood out of the heart.
• Special feature: They have a large diameter and are specialized for rapid conduction of electrical impulses. Their conduction speed is much faster than that of ordinary cardiac muscle cells.

For heart sounds:

• Heart sounds are produced by the closing of heart valves and the turbulent flow of blood.
• The first heart sound ($S_1$) is "lubb" and is caused by the closure of the atrioventricular valves (tricuspid and mitral valves) at the beginning of ventricular systole. It marks the start of ventricular contraction.
• The second heart sound ($S_2$) is "dubb" and is due to the closure of the semilunar valves (aortic and pulmonary valves) at the end of ventricular systole. It marks the end of ventricular contraction.
• Abnormal heart sounds (murmurs) can indicate problems such as valve stenosis (narrowing) or regurgitation (leaking).

Answer:

Part	Function	Special feature
Systematic Aorta	Carries oxygen - rich blood from left ventricle to body	Thick, elastic wall for blood pressure maintenance
Purkenji fibers	Rapidly conduct electrical impulses to ventricular muscle	Large diameter for fast conduction

Heart sounds:

• $S_1$ ("lubb"): Atrioventricular valve closure (start of ventricular systole).
• $S_2$ ("dubb"): Semilunar valve closure (end of ventricular systole).
• Murmurs: Indicate valve problems (stenosis/regurgitation).