The parasympathetic nervous system decreases heart rate through a series of steps:

1. The process begins in the medulla oblongata, the part of the brain that controls autonomic functions such as heart rate.

2. When the body is in a relaxed state, the medulla oblongata sends signals via the vagus nerve, a cranial nerve, to the heart.

3. The vagus nerve releases a neurotransmitter called acetylcholine.

4. Acetylcholine binds to receptors on the heart's pacemaker cells, which are located in the sinoatrial (SA) node.

5. This binding causes the cells to become hyperpolarized, meaning they are less likely to fire.

6. As a result, the rate of electrical impulses that trigger heart contractions is slowed down.

7. This leads to a decrease in heart rate, allowing the body to conserve energy during times of rest or digestion.

Question

The parasympathetic nervous system decreases heart rate through a series of steps:

1. The process begins in the medulla oblongata, the part of the brain that controls autonomic functions such as heart rate.

2. When the body is in a relaxed state, the medulla oblongata sends signals via the vagus nerve, a cranial nerve, to the heart.

3. The vagus nerve releases a neurotransmitter called acetylcholine.

4. Acetylcholine binds to receptors on the heart's pacemaker cells, which are located in the sinoatrial (SA) node.

5. This binding causes the cells to become hyperpolarized, meaning they are less likely to fire.

6. As a result, the rate of electrical impulses that trigger heart contractions is slowed down.

7. This leads to a decrease in heart rate, allowing the body to conserve energy during times of rest or digestion.

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