Question

Name the two cardiac centers and state their location. Sympathetic impulses to the heart have what effect? Parasympathetic impulses to the heart have what effect? Name the parasympathetic nerves to the heart. (p. 287)

Short answer

Question: Identify the two cardiac centers, their location, and the effects of sympathetic and parasympathetic impulses on the heart. Additionally, name the parasympathetic nerves to the heart. Answer: The two main cardiac centers are the cardioaccelerator center and the cardioinhibitory center, both located in the medulla oblongata. Sympathetic impulses, sent through the cardioaccelerator center, increase the heart rate and strength of contraction. Parasympathetic impulses, sent through the cardioinhibitory center, decrease the heart rate and strength of contraction. The parasympathetic nerves to the heart are called the vagus nerves (cranial nerve X).

Step-by-step solution

1. Cardiac Centers

There are two main cardiac centers in the human body, the cardioaccelerator center and the cardioinhibitory center.

2. Location of Cardiac Centers

Both of these cardiac centers are located in the medulla oblongata, which is a part of the brainstem.

3. Sympathetic Impulses to the Heart

Sympathetic impulses to the heart are sent through the cardioaccelerator center and have the effect of increasing the heart rate and the strength of contraction. This is the body's "fight or flight" response, preparing the body for action.

4. Parasympathetic Impulses to the Heart

Parasympathetic impulses are sent through the cardioinhibitory center and generally have the effect of decreasing the heart rate and the strength of contraction. This is more of a "rest and digest" response, as it helps to conserve energy and restore the body's resources.

5. Parasympathetic Nerves to the Heart

The parasympathetic nerves that reach the heart are called the vagus nerves (cranial nerve X). These nerves play a crucial role in regulating the body's heart rate in response to various stimuli and conditions.

Key concepts

Sympathetic Impulses

Sympathetic impulses play a crucial role in preparing the body for action. These impulses originate from the cardioaccelerator center in the medulla oblongata. When triggered, they increase both the heart rate and the strength of heart contractions. This is part of the body's natural "fight or flight" response, which helps you react quickly to stress or danger.
Think of this response as your body's way of amping up your heart function to ensure you can handle a challenging situation.

• Increase in heart rate
• Stronger heart contractions
• Part of the fight or flight response

This system is essential for acute stress situations, like running away from a threat or engaging in physical exercise.

Parasympathetic Impulses

Parasympathetic impulses work in an almost opposite manner to sympathetic impulses. These signals are responsible for calming the heart down after it has been stimulated. They are sent through the cardioinhibitory center in the medulla oblongata, and they decrease the heart's rate and contraction strength.
This calming down process is often dubbed the "rest and digest" response. It ensures energy conservation and recovery.

• Decrease in heart rate
• Weaker heart contractions
• Part of the rest and digest response

Thanks to the parasympathetic system, your heart shifts its focus from action to rest and recuperation, maintaining balance in your body's functions.

Vagus Nerve

The vagus nerve, also known as cranial nerve X, is a key player in the parasympathetic nervous system. It helps mediate the heart's activity by sending calming parasympathetic impulses to the heart.
Its function is to lower the heart rate and manage other involuntary activities related to resting and digesting.

• Connected to the cardioinhibitory center
• Reduces heart rate
• Part of the parasympathetic nervous system

Because of the vagus nerve, your heart receives signals to slow down and conserve energy, playing an integral part in your body's ability to remain in a state of calm and rest.

Medulla Oblongata

The medulla oblongata, a critical structure in the brainstem, houses both cardiac centers. It functions as a control center for regulating involuntary bodily processes, including heart rate and blood pressure.
This section of the brain is crucial because it ensures that both sympathetic and parasympathetic responses are appropriately coordinated.

• Located in the brainstem
• Controls involuntary functions
• Hosts both cardiac centers

Without the medulla oblongata, our ability to seamlessly switch between increased action and restful periods would be impaired, affecting our overall health and efficiency.

Cardioaccelerator Center

The cardioaccelerator center is responsible for managing the body’s increase in heart activity. Located in the medulla oblongata, it plays a pivotal role in the sympathetic response.
When you encounter a stressful situation, the cardioaccelerator center sends signals via sympathetic nerves to the heart, causing an increase in speed and intensity of beats.

• Increases heart rate
• Located in the medulla oblongata
• Triggers fight or flight response

The operations of the cardioaccelerator center are vital when rapid physical action is necessary, thus ensuring your body can respond adequately to immediate threats or challenges.

Cardioinhibitory Center

The cardioinhibitory center acts to reduce heart activity and promote relaxation. Found within the medulla oblongata, this center is key to initiating the parasympathetic response.
It sends impulses through the vagus nerve to lower the heart rate, promoting a calm state.

• Decreases heart rate
• Located in the medulla oblongata
• Engages rest and digest response

By managing the down-regulation of heart activity, the cardioinhibitory center helps maintain a balance between action and rest, ensuring the body doesn’t burn out from continuous stress or exertion.