Autonomic Nervous System

Autonomic Nervous System

General Neural Organization

Two motor neurons are involved in the connection between the CNS and the target organ

Preganglionic neurons - the first motor neurons; cell bodies are located within the CNS

Ganglionic neurons - the second motor neurons; cell bodies are located in autonomic ganglia outside of the CNS

Sympathetic Division

Axons of preganglionic neurons from the thoracic and lumbar spinal segments synapse in three groups of ganglia located peripherally:

Sympathetic Chain Ganglia

Affect smooth (and cardiac) muscle in skin, skeletal muscle and thoracic organs

Celiac and Mesenteric Ganglia

Affect smooth muscle in abdominal and pelvic organs

Adrenal Medulla

Affect smooth (and cardiac) muscle in skin, skeletal muscle, and thoracic, abdominal and pelvic organs through release of Norepinephine and Epinephrine into blood

Neurotransmitters

preganglionic neurons release acetylcholine which act on nicotinic receptors on the ganglionic neurons

postganglionic fibers release norepinephrine which act on either alpha or beta receptors of the target organs

Parasympathetic Division

Axons of preganglionic neurons in the brain stem and sacral spinal segments synapse on neurons in intramural ganglia, inside visceral organs.Intramural Ganglia in head and neck:

Affect pupils and salivary glands

Thoracic Intramural Ganglia:

Affect thoracic organs

Abdominal and Pelvic Intramural Ganglia:

Affect abdominal and pelvic organs

Neurotransmitters

preganglionic neurons release acetylcholine which act on nicotinic receptors on the ganglionic neurons

postganglionic neurons release acetylcholine which act on muscarinic receptors of the target organs