Chapter 20, Problem 1O

Summary Introduction

To review:

The functions of the autonomic nervous system and the impact of the parasympathetic division.

Introduction:

The central nervous system (CNS) and peripheral nervous system (PNS) are considered as the two important branches of the nervous system. The CNS consists of the spinal cord and brain, whereas the PNS contains autonomic (ANS) and somatic nervous system (SNS). The ANS is further divided into the sympathetic or adrenergic and parasympathetic or cholinergic. The main functional unit of ANS is visceral reflex and it involves the body homeostasis.

Explanation of Solution

Functions of the autonomic nervous system:

The autonomic nervous system consists of complex neurons that innervate and influence all the metabolic functions of the body. It includes blood pressure maintenance, breathing rate regulation, urination, gut motility (digestion), and sexual arousal modulation. It controls and influences the cardiovascular system by altering the heart rate contraction, blood vessel dilation, and constriction.

Impact of the parasympathetic nervous system:

The parasympathetic nervous system is a part of the autonomic nervous system which has the opposite function to the sympathetic nervous system. In PNS, the nerve impulse transmission to effector cells is carried out by acetylcholine neurotransmitters. The functions of PNS are mediated by binding of cholinergic receptors to the acetylcholine receptors. Nicotinic and muscarinic receptors are determined based on the location and action of the cholinergic receptors.

Nicotinic receptor is located at the ganglia of the ANS and SNS and it is stimulated by the nicotine. It is a receptor of ligand-controlled cation channels for potassium and sodium ions.

Muscarinic receptors is a cholinergic receptor coupled with G-protein and they control the ion channels. They are located in all effector cells innervated by postganglionic cholinergic fibers of smooth muscles, cardiac muscles, and glands. This receptor is stimulated by muscarinic- an alkaloid muscarine from mushrooms.

Conclusion

Thus, autonomic nervous involves the body homeostasis and it impacts the parasympathetic nervous system by binding of cholinergic receptors to the acetylcholine neurotransmitters.