Autonomic Ganglia: Anatomical Characteristics and Physiological Functions
Autonomic ganglia are collections of nerve cells found in the peripheral nervous system (PNS). They are located outside the central nervous system (CNS) and play a crucial role in the control of autonomic functions such as heartbeat, breathing, and digestion (Watts, 2021). The autonomic ganglia are composed of two main types of neurons: preganglionic and postganglionic. The preganglionic neurons originate from the central nervous system and transmit their signals through the autonomic ganglia to the postganglionic neurons. The postganglionic neurons then transmit the signals to various target organs to regulate their activity. This article will discuss the anatomical characteristics and physiological functions of the autonomic ganglia.
Anatomy
The autonomic ganglia can be divided into two categories: the sympathetic ganglia and the parasympathetic ganglia. The sympathetic ganglia are composed of two types of neurons: the preganglionic neurons and the postganglionic neurons. The preganglionic neurons originate from the thoracolumbar region of the spinal cord and are composed of myelinated axons. These axons extend from the CNS, travel through the sympathetic chain, and synapse with the postganglionic neurons present in the sympathetic ganglia. The postganglionic neurons are composed of unmyelinated axons that extend from the sympathetic ganglia to the target organs.
The parasympathetic ganglia are composed of three types of neurons: the preganglionic neurons, the postganglionic neurons, and the intramural neurons. The preganglionic neurons originate from the cranial and sacral regions of the spinal cord and are composed of myelinated axons. These axons travel from the CNS to the parasympathetic ganglia and synapse with the postganglionic neurons present in the parasympathetic ganglia. The postganglionic neurons are composed of unmyelinated axons that extend from the parasympathetic ganglia to the target organs. The intramural neurons are present in the walls of the target organs and are composed of both myelinated and unmyelinated axons.
Physiology
The autonomic ganglia play an important role in the regulation of autonomic functions such as heartbeat, breathing, and digestion. The sympathetic ganglia are involved in the control of the fight-or-flight response, which is a response to stressful situations. The preganglionic neurons release the neurotransmitter acetylcholine which binds to the nicotinic receptors present on the postganglionic neurons. This binding leads to the release of the neurotransmitters epinephrine and norepinephrine, which activate the sympathetic nervous system. This activation leads to an increase in heart rate, blood pressure, and respiration rate in order to prepare the body for fight or flight.
The parasympathetic ganglia are involved in the control of the rest-and-digest response, which is a response to relaxed situations. The preganglionic neurons release the neurotransmitter acetylcholine which binds to the muscarinic receptors present on the postganglionic neurons. This binding leads to the release of the neurotransmitter acetylcholine, which activates the parasympathetic nervous system. This activation leads to a decrease in heart rate, blood pressure, and respiration rate in order to conserve energy and promote digestion.
Conclusion
Autonomic ganglia are collections of nerve cells located outside the central nervous system. They are composed of two main types of neurons: preganglionic and postganglionic. The preganglionic neurons originate from the CNS and transmit their signals to the postganglionic neurons present in the autonomic ganglia. The postganglionic neurons then transmit the signals to various target organs to regulate their activity. The autonomic ganglia are involved in the control of the fight-or-flight response and the rest-and-digest response, which are essential for homeostasis.
References
Watts, S. (2021). Anatomy and physiology of autonomic ganglia. Retrieved from https://www.sciencedirect.com/topics/neuroscience/autonomic-ganglia