Autonomic Nervous System

ANS target tissues

Smooth muscle, cardiac muscle, and glands.

Sympathetic tone

Background activity where both branches are always active to some degree.

Sympathetic head and thorax outflow

T1-T6 spinal segments.

Sympathetic abdominopelvic outflow

T5-L2 spinal segments.

Sympathetic pre-ganglionic destination

Trunk ganglia.

Collateral ganglia location

Anterior to the vertebral column.

Parasympathetic ganglia name

Terminal ganglia.

Terminal ganglia location

Close to or within the wall of the target organ.

Vagus nerve contribution

90% of pre-ganglionic parasympathetic fibres.

Cranial nerves supplying head parasympathetic innervation

CN III, VII, and IX.

Cholinergic receptors

Receptors that bind acetylcholine (ACh).

Nicotinic receptor locations

ANS post-ganglionic neurons, adrenal medullary cells, and skeletal muscles.

Effect of ACh on nicotinic receptors

Excitation (EPSP).

Muscarinic receptor location

All parasympathetic target organs.

Effect of ACh on muscarinic receptors

Excitation (EPSP) or inhibition (IPSP).

Adrenergic receptors

Receptors that bind noradrenaline and adrenaline.

Beta-1 receptor location and effect

Located in the heart; causes excitation.

Beta-2 receptor

Located in airways and certain blood vessels/organs; causes inhibition.

Alpha-1 receptor location and effect

Located in most sympathetic targets and blood vessels; causes excitation.

Effect of NA on peripheral blood vessels

Binds alpha-1 receptors to cause vasoconstriction and decreased blood flow.

Effect of NA on skeletal muscle blood vessels

Binds beta-2 receptors to cause vasodilation and increased blood flow.

Adrenal gland role in sympathetic response

Releases NA and adrenaline into the bloodstream to amplify the response.

Visceral afferents definition

Nerve fibres carrying sensory information from internal organs to the CNS.

Baroreceptors detect

Stretch of the blood vessel wall.

High blood pressure baroreceptor response

Parasympathetic innervation decreases heart rate to lower blood pressure.

Low blood pressure baroreceptor response

Sympathetic innervation increases heart rate to raise blood pressure.

Parasympathetic Ganglia

Long pre

Short post

Sympathetic Ganglia

Short pre

Long post

CN X

vagus nerve

Parasympathetic makeup

CN III, VII, IX + CN X + sacral nerves

More stretch

higher BP