🧠 Nervous System🟢 BasicAutonomic Nervous System

The Autonomic Nervous System

The part of the nervous system that automatically controls internal organs, glands and vessels, through two divisions that usually balance the body's activity.

Key points

The autonomic nervous system controls involuntary functions such as heart rate, blood pressure, digestion and sweating, working without conscious thought.
It has two divisions: the sympathetic system for fight-or-flight and the parasympathetic system for rest-and-digest, which often oppose each other, though many organs are driven mainly by one division.
Each autonomic pathway uses two neurons in series, meeting at a relay station called a ganglion, unlike the single motor neuron that runs to skeletal muscle.
All preganglionic neurons and the parasympathetic endings release acetylcholine, while most sympathetic endings release noradrenaline; an exception is the sweat glands, whose sympathetic fibres release acetylcholine.
The sympathetic system speeds the heart, widens the pupils and airways and diverts blood to muscle, while the parasympathetic system does the opposite and aids digestion.
The adrenal medulla acts like a sympathetic ganglion, releasing mainly adrenaline (with some noradrenaline) into the blood to spread the fight-or-flight response around the body.

Memory trick

Two divisions, two neurons each: sympathetic is fight-or-flight (noradrenaline), parasympathetic is rest-and-digest (acetylcholine); the adrenal medulla is a modified sympathetic ganglion.

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🧠 Nervous System🟢 BasicAutonomic Nervous System

The Autonomic Nervous System

The part of the nervous system that automatically controls internal organs, glands and vessels, through two divisions that usually balance the body's activity.

Key points

The autonomic nervous system controls involuntary functions such as heart rate, blood pressure, digestion and sweating, working without conscious thought.
It has two divisions: the sympathetic system for fight-or-flight and the parasympathetic system for rest-and-digest, which often oppose each other, though many organs are driven mainly by one division.
Each autonomic pathway uses two neurons in series, meeting at a relay station called a ganglion, unlike the single motor neuron that runs to skeletal muscle.
All preganglionic neurons and the parasympathetic endings release acetylcholine, while most sympathetic endings release noradrenaline; an exception is the sweat glands, whose sympathetic fibres release acetylcholine.
The sympathetic system speeds the heart, widens the pupils and airways and diverts blood to muscle, while the parasympathetic system does the opposite and aids digestion.
The adrenal medulla acts like a sympathetic ganglion, releasing mainly adrenaline (with some noradrenaline) into the blood to spread the fight-or-flight response around the body.

Memory trick

Two divisions, two neurons each: sympathetic is fight-or-flight (noradrenaline), parasympathetic is rest-and-digest (acetylcholine); the adrenal medulla is a modified sympathetic ganglion.

All of Physiology More Nervous System