Effect of Acetylcholine on Heart Rate

Acetylcholine is a neurotransmitter that is responsible for the parasympathetic nervous system's functioning. It controls a wide range of bodily functions, including heart rate, digestion, and respiratory rate. Acetylcholine is a neurotransmitter that is released by nerve cells and binds to receptors on the target cell's surface.

Effect of Acetylcholine on Heart Rate

When acetylcholine is released, it binds to specific receptors in the heart, causing the heart rate to decrease. This is because acetylcholine stimulates the parasympathetic nervous system, which is responsible for slowing the heart rate. The parasympathetic nervous system opposes the sympathetic nervous system, which is responsible for increasing the heart rate.

Mechanism of Action of Acetylcholine on Heart Rate

Acetylcholine binds to muscarinic receptors in the heart, which are located in the sinoatrial node (SA node) and the atrioventricular node (AV node). The SA node is the primary pacemaker of the heart, and it generates electrical impulses that initiate the heart's contraction. The AV node is responsible for transmitting electrical impulses from the atria to the ventricles.

When acetylcholine binds to muscarinic receptors in the SA node, it decreases the rate of depolarization, which reduces the heart rate. This effect is due to the opening of potassium channels, which hyperpolarizes the cell membrane and makes it less likely to generate an action potential.

In the AV node, acetylcholine decreases the conduction velocity of electrical impulses, which further decreases the heart rate. This effect is due to the opening of potassium channels and the inhibition of calcium channels, which reduces the influx of calcium ions into the cells.

Conclusion

In summary, the injection of acetylcholine will decrease the heart rate by stimulating the parasympathetic nervous system. This effect is due to the binding of acetylcholine to muscarinic receptors in the SA node and AV node, which reduces the rate of depolarization and conduction velocity of electrical impulses, respectively.