Autonomic Nervous System Overview

The autonomic nervous system (ANS) is a crucial part of the peripheral nervous system that regulates involuntary bodily functions, including things like heart rate, blood pressure, breathing, and digestion.

The sympathetic nervous system is responsible for the 'fight-or-flight' response, preparing the body for stressful situations. Think of it as the 'gas pedal' for your body.

The parasympathetic nervous system is responsible for the 'rest-and-digest' response, promoting relaxation and energy conservation. Think of it as the 'brake pedal' for your body.

Acetylcholine is a neurotransmitter that plays a key role in the ANS. It's used by both the sympathetic and parasympathetic systems, especially in the preganglionic neurons and some postganglionic neurons.

Muscarinic receptors are a type of acetylcholine receptor found at postganglionic parasympathetic nerve endings. These receptors are responsible for mediating the effects of acetylcholine on target organs like the heart, smooth muscles and glands.

Muscarinic receptors are classified into subtypes. These subtypes are important because they dictate the specific effect of acetylcholine on different cells and tissues. For example, M1 receptors are found in the brain, while M3 receptors are responsible for smooth muscle contraction.

Atropine is a drug that acts as a muscarinic antagonist, meaning it blocks the action of acetylcholine at muscarinic receptors. This can have effects on various organ systems like the heart, eye, and digestive tract.

G-protein coupled receptors (GPCRs) are a large family of cell surface receptors that are involved in many cellular processes including signaling in the nervous system. Muscarinic receptors belong to this class of receptors and they mediate their effects through intracellular signaling pathways.

A type of neurotransmitter receptor found in autonomic ganglia, the suprarenal medulla, and motor end plates. They are stimulated by nicotine and are blocked by Hexamethonium (for neuronal nicotinic receptors) and d-tubocurarine (for muscle nicotinic receptors).

They mediate the effects of norepinephrine and epinephrine in the sympathetic nervous system. There are two main types: alpha (α) and beta (β).

A type of adrenergic receptor that is mostly excitatory. They are further subdivided into α1 (A, B, D) and α2 (A, B, C).

A type of adrenergic receptor that is mostly inhibitory. There are five subtypes: β1, β2, β3, β4, and β5, with β3 receptors located in adipose tissue and β4 and β5 receptors under research.

The process of synthesizing catecholamines, including norepinephrine, epinephrine, and dopamine, begins with the amino acid tyrosine.