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Physiology Autonomic Nervous System
Testing
11
Physiology
Graduate
09/12/2009
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Term
o Locations of Preganglionic and Motor neurons
 Definition
 Sympathetic: Thoracocolumbar (T1 – T3 segments of spinal cord)
 Parasympathetic: craniosacral (midbrain, pons, medulla, S2-S4)

Somatic: spinal cord, medulla
Term
o Preganglionic
 Definition
 Sympathetic: short, ganglia close to spinal cord and adrenal medulla
 Parasympathetic: long, ganglia close to or in end organs

Somatic: midway between para and sympathetic, none
Term
Effectors
 Definition
 Sympathetic: smooth muscle in heart, blood vessels, etc; sweat glands
 Parasympathetic: smooth muscle in atria, GI tract, etc
Term
o Preganglionic and motor neuron transmitter and receptor subtypes (NN = neuronal nicotinic receptor and NM = skeletal muscle receptor)
 Definition
 all preganglionic and motor neurons are cholinergic and release ACh at their nerve terminals in the autonomic ganglia, adrenal medulla or skeletal muscle
Term
o Parasympathetic Postganglionic Neurotransmitter and Receptors
 Definition
 all parasympathetic ganglia neurons are cholinergic and release ACh at their terminals in smooth muscle and glands, which activates muscarinic receptors
Term
o Sympathetic Postganglionic Transmitters and Receptors
 Definition
 Nearly all sympathetic ganglia neurons are adrenergic and release NE at their terminals in end organs
• exception: at sweat glands have ACh and muscarinic receptors
 Adrenal medulla: cells have adrenergic and release epinephrine (80%) and NE (20%)into the bloodstream to have systemic effects
Term
Sympathetic only innervation
 Definition
vascular smooth muscles

Ventricles of the heart

Sweat glands

Kidney

Liver

Adipose tissue
Term
Parasympathetic only innervation
 Definition
airway smooth muscle
Term
Nicotinic receptors
 Definition
 Cholinoceptors
• cationic: Na+, K+, Ca2+ (flood in or out when channel is open: K+ hyperpolarizes while other two depolarize)
• Ligand-gated ion channels: found on all autonomic ganglia neurons, adrenal chromaffin cells, and skeletal muscle
 Excitatory
• when activated by ACh, rapid (ms) depolarize autonomic ganglia neuronsmessage to end organ
 Subunits
• NN contains α3 subunits
• NM contain α1 subunits
 Blockage
• nexamethonium blocks NN
• tubocurare blocks NM
Term
Muscarinic receptors
 Definition
 Cholinoceptor
• G protein coupled receptors: action is slower but more prolonged
• When activated by ACh can either cause contraction or relaxation of smooth muscles
 Subtypes
• M1, M3, and M5 subtypes act through phospholipase C and IP3 pathway to increase cellular Ca2+causes muscle contraction
• M2 and M4 in sinoatrial (SA) node causes release of the G protein αi subunitbinds to K+ channel and activates itinhibitory hyperpolarizing response in atrial muscledecrease in HR and contractility
 cause secretion in lacrimal glands (para) and sweat glands (sym)

Parasympathetic and Sympathetic Sweat
 Blockage: atropine
Term
Adrenoreceptors (sympathetic)
 Definition
 four types of adrenoreceptors
 All are G protein coupled receptors
 β1 in heart
 α1 (contracton), β2 (relaxation) in blood vessels
 β1 in kidney, fat
 α1 in GI sphincters
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