Autonomic nervous system

Introduction

The autonomic nervous system (ANS) is responsible for maintaining homeostasis by regulating involuntary physiological processes such as heart rate, respiration, digestion, and pupil response. It consists of two divisions: the sympathetic nervous system, which prepares the body for "fight or flight" responses, and the parasympathetic nervous system, which promotes "rest and digest" activities. These divisions often work in opposition to maintain a balanced physiological state, adapting the body to changing environmental conditions and physiological needs.

The ANS exerts its effects through a network of neurons that originate in the central nervous system (CNS) and communicate with peripheral organs via autonomic ganglia. The sympathetic division generally stimulates physiological processes that enable the body to respond to stress, while the parasympathetic division conserves energy and restores normal function after stressors have subsided.

Neurotransmitters such as acetylcholine (ACh) and norepinephrine (NE) transmit signals between neurons and target organs. The type of receptor they bind to determines the physiological response. Nicotinic and muscarinic receptors mediate cholinergic transmission, while adrenergic receptors regulate responses to norepinephrine. Understanding how these systems interact provides insight into their role in health and disease, such as autonomic dysfunctions in conditions like hypertension or heart failure.

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Sympathetic vs. Parasympathetic Nervous System

Neurotransmitters in the ANS

Dual Innervation and Homeostasis

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Summary