Answer
The cardiac center is a part of the autonomic nervous system that plays a crucial role in regulating the heart rate and cardiac output. It's located in the medulla oblongata, which is a part of the brainstem. The cardiac center consists of two main components: the sympathetic cardiac accelerator center and the parasympathetic cardiac inhibitory center. These centers work together to control the heart rate and maintain the balance between sympathetic (fight or flight) and parasympathetic (rest and digest) nervous system influences on the heart.
1. **Sympathetic Cardiac Accelerator Center**: This part of the cardiac center is responsible for increasing the heart rate and cardiac output in response to stress, physical activity, or other situations that require increased blood flow to the body's tissues. The sympathetic nervous system releases norepinephrine, which binds to beta-adrenergic receptors on the heart muscle cells (myocytes), leading to an increase in heart rate and the force of contraction. This results in a higher cardiac output.
2. **Parasympathetic Cardiac Inhibitory Center**: This component of the cardiac center is responsible for slowing down the heart rate during times of rest or relaxation. The parasympathetic nervous system releases acetylcholine, which binds to muscarinic receptors on the myocytes, leading to a decrease in heart rate. This action is particularly important in situations where the body needs to conserve energy and reduce blood flow.
In summary, the cardiac center integrates signals from various parts of the body, including sensory receptors, to adjust the heart rate and cardiac output according to the body's needs. The interplay between sympathetic and parasympathetic influences allows for fine-tuned control of heart function.
The innervation of the heart involves these autonomic nervous system pathways:
- **Sympathetic Nervous System**: Sympathetic nerves originate from the thoracic and upper lumbar regions of the spinal cord. They release norepinephrine, which accelerates the heart rate and increases the force of contractions. This prepares the body for increased activity or stress.
- **Parasympathetic Nervous System**: Parasympathetic nerves originate from the vagus nerve (cranial nerve X) and release acetylcholine. This leads to a decrease in heart rate and a decrease in the force of contractions. The parasympathetic system promotes restful states and helps conserve energy.
The balance between sympathetic and parasympathetic influences on the heart is essential for maintaining heart rate variability and adapting to various physiological demands.
Work Step by Step
The cardiac center is a part of the autonomic nervous system that plays a crucial role in regulating the heart rate and cardiac output. It's located in the medulla oblongata, which is a part of the brainstem. The cardiac center consists of two main components: the sympathetic cardiac accelerator center and the parasympathetic cardiac inhibitory center. These centers work together to control the heart rate and maintain the balance between sympathetic (fight or flight) and parasympathetic (rest and digest) nervous system influences on the heart.
1. **Sympathetic Cardiac Accelerator Center**: This part of the cardiac center is responsible for increasing the heart rate and cardiac output in response to stress, physical activity, or other situations that require increased blood flow to the body's tissues. The sympathetic nervous system releases norepinephrine, which binds to beta-adrenergic receptors on the heart muscle cells (myocytes), leading to an increase in heart rate and the force of contraction. This results in a higher cardiac output.
2. **Parasympathetic Cardiac Inhibitory Center**: This component of the cardiac center is responsible for slowing down the heart rate during times of rest or relaxation. The parasympathetic nervous system releases acetylcholine, which binds to muscarinic receptors on the myocytes, leading to a decrease in heart rate. This action is particularly important in situations where the body needs to conserve energy and reduce blood flow.
In summary, the cardiac center integrates signals from various parts of the body, including sensory receptors, to adjust the heart rate and cardiac output according to the body's needs. The interplay between sympathetic and parasympathetic influences allows for fine-tuned control of heart function.
The innervation of the heart involves these autonomic nervous system pathways:
- **Sympathetic Nervous System**: Sympathetic nerves originate from the thoracic and upper lumbar regions of the spinal cord. They release norepinephrine, which accelerates the heart rate and increases the force of contractions. This prepares the body for increased activity or stress.
- **Parasympathetic Nervous System**: Parasympathetic nerves originate from the vagus nerve (cranial nerve X) and release acetylcholine. This leads to a decrease in heart rate and a decrease in the force of contractions. The parasympathetic system promotes restful states and helps conserve energy.
The balance between sympathetic and parasympathetic influences on the heart is essential for maintaining heart rate variability and adapting to various physiological demands.
