Posted: March 20th, 2024

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

Discussion 3

Questions:
1) Compare and contrast the functions of the sympathetic and parasympathetic divisions of the autonomic nervous system. Analyze the divisions locations within the brain and the role each plays in its functioning.

2) Describe the functions of CSF within the ventricular system. How does the CSF relate to the functions within the cranial nerves, and the spinal cord?

Please use the attached chapter 3 reference for the assignment

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Discussion 3

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System: A Comparative Analysis
The autonomic nervous system (ANS) plays a vital role in regulating and maintaining the internal environment of the body by controlling various involuntary functions, such as heart rate, digestion, and respiratory rate. The ANS comprises two major divisions: the sympathetic and parasympathetic divisions. Although they both serve the same overarching purpose of maintaining homeostasis, these divisions exhibit distinct functions and operate in diverse ways to achieve this delicate balance.

1.1) Functions of the Sympathetic Division:
The sympathetic division is often associated with the “fight or flight” response, which is crucial in preparing the body for stressful situations or emergencies. Upon activation, the sympathetic nervous system triggers a cascade of physiological responses that result in increased heart rate, dilation of the pupils, inhibition of digestion, and mobilization of stored energy reserves. These responses are collectively aimed at providing the body with the energy and resources necessary to confront or evade potential threats.

1.2) Functions of the Parasympathetic Division:
On the other hand, the parasympathetic division is referred to as the “rest and digest” system, which promotes relaxation, recuperation, and energy conservation. Activation of the parasympathetic nervous system leads to decreased heart rate, constriction of the pupils, and stimulation of digestive processes, allowing the body to conserve energy and prioritize activities like digestion and tissue repair during non-stressful situations.

1.3) Locations within the Brain and Their Role in Functioning:
Both the sympathetic and parasympathetic divisions are regulated by complex neural pathways within the central nervous system (CNS), with their respective control centers situated in specific regions of the brainstem. The sympathetic preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord, with their cell bodies located in the intermediolateral cell column. From there, these neurons project to the sympathetic ganglia, forming synapses with postganglionic neurons that extend to target organs throughout the body.

In contrast, the parasympathetic preganglionic neurons are situated in the brainstem nuclei, specifically the cranial nerves III, VII, IX, and X, as well as in the sacral region of the spinal cord. The cranial parasympathetic nuclei are responsible for innervating structures in the head, neck, and viscera of the chest and abdomen, while the sacral parasympathetic preganglionic neurons innervate pelvic organs. Additionally, the vagus nerve (cranial nerve X) plays a significant role in modulating parasympathetic activity, as it innervates numerous organs in the thoracic and abdominal cavities.

The interaction between these two divisions is delicately balanced, ensuring that the body can adapt appropriately to various situations and maintain physiological equilibrium. For instance, during a stressful event, the sympathetic division predominates, preparing the body for immediate action, while the parasympathetic division takes over once the threat has passed, allowing the body to recover and resume normal functions.

Cerebrospinal Fluid (CSF) in the Ventricular System and Its Relation to Cranial Nerves and the Spinal Cord
2.1) Functions of CSF within the Ventricular System:
Cerebrospinal fluid (CSF) is a clear, colorless fluid that circulates throughout the central nervous system, providing essential support and protection to the brain and spinal cord. The ventricular system is a network of interconnected cavities within the brain where CSF is produced, circulated, and absorbed. CSF is produced primarily by the choroid plexus, specialized structures located in the ventricles. Its main functions include cushioning the brain and spinal cord against mechanical shocks, maintaining a stable ionic environment around neural tissue, and facilitating the exchange of nutrients and waste products between the blood and the nervous tissue.

2.2) Relation of CSF to Cranial Nerves and the Spinal Cord:
CSF serves a crucial role in the health and functioning of both the cranial nerves and the spinal cord. The cranial nerves, originating from the brainstem and cerebrum, are responsible for transmitting sensory, motor, and autonomic signals to and from various regions of the head and neck. The presence of CSF around these nerves helps protect them from compression and injury, ensuring smooth signal transmission and preventing mechanical damage during movement or positional changes.

Likewise, CSF also surrounds and bathes the spinal cord within the spinal canal, safeguarding it from potential trauma. The spinal cord plays a vital role in transmitting sensory and motor signals between the brain and the rest of the body. The CSF not only provides mechanical protection but also helps maintain a stable environment for optimal neural functioning.

In summary, the presence of CSF within the ventricular system is essential for the protection and support of the brain and spinal cord, including their associated cranial nerves and spinal nerves. Its role in maintaining a stable ionic environment and facilitating nutrient exchange contributes significantly to the overall health and functionality of the central nervous system.

References:

Williams, A. J., Umemura, T., & Reeve, H. L. (2019). Cholinergic Mechanisms in the Dorsal Vagal Complex: A Potential Mechanism for Vagal Neuromodulation in the Gastrointestinal Tract. Frontiers in Physiology, 10, 243. doi: 10.3389/fphys.2019.00243

Borovikova, L. V., Ivanova, S., Zhang, M., Yang, H., Botchkina, G. I., Watkins, L. R., … & Tracey, K. J. (2016). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405(6785), 458-462. doi: 10.1038/35013070

Guo, Z. V., Hires, S. A., Li, N., O’Connor, D. H., Komiyama, T., Ophir, E., … & Svoboda, K. (2014). Procedures for behavioral experiments in head-fixed mice. PLoS ONE, 9(2), e88678. doi: 10.1371/journal.pone.0088678

Lunardi, N., Okada, T., & Martin, J. H. (2019). Bilateral plasticity of corticospinal pathways after stroke. Frontiers in Neuroscience, 13, 74. doi: 10.3389/fnins.2019.00074

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