Chapter 21, Problem 1O

Summary Introduction

To discuss:

Briefly review the functions of the sympathetic nervous system and the specific effects of blocking cholinergic receptors (parasympatholytics effects).

Concept introduction:

The parasympathetic nervous system is a part of the autonomic nervous system, in which the transmission of impulses is carried to the effector cells by the neurotransmitter, acetylcholine. The cholinergic-blocking drugs are used to block the effects of the parasympathetic nervous system.

Explanation of Solution

Functions of the sympathetic nervous system: The autonomic nervous system has two divisions, namely sympathetic and parasympathetic nervous system. The sympathetic nervous system stimulates the response of fight-or-flight in our body. It helps to maintain the homeostasis at a basic level and it acts as complementary to the action of the parasympathetic nervous system. It stimulates the constriction of blood vessels present in the digestive tract, kidneys, and skin. This constriction is stimulated by α-1 adrenergic receptors activation by norepinephrine. Βeta-2 adrenergic receptors stimulates the relaxation of the muscles present in the lungs, the heart, and the brain, and the skeletal muscles. The net result is a flow of blood increased in those organs which have high physical activity.

The specific effects of the parasympathetic nervous system:

The parasympathetic nervous system’s action is complementary to the sympathetic nervous system. It stimulates the body’s rest and digest activities. Acetylcholine is responsible for the action of the parasympathetic nervous system. The acetylcholine binds to nicotinic cholinergic and muscarinic receptors. The cholinergic blockers inhibit the muscarinic action of the parasympathetic nervous system by blocking the action of acetylcholine. The sympathetic nervous system is dominated when the parasympathetic nervous system is blocked. The anticholinergics act in the heart, gastrointestinal tract, eye, respiratory, and exocrine gland.

Conclusion

Thus, the sympathetic nervous system stimulates the fight or flight responses to the body, and cholinergic blocking or parasympathetic nervous system stimulates the rest and digest response to the body.