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Divisions of the Nervous System: The two big divisions are the CNS (brain and spinal cord) and the PNS. The PNS = The Somatic Motor System & the Autonomic Nervous System. Voluntary muscles are under the control of the somatic motor system. Autonomic Nervous System controls the involuntary body processes.

Autonomic Nervous System

Three Functions:

Regulation of the Heart

Regulation of Secretory Glands

Regulation of Smooth Muscle

Two Divisions of the Autonomic Nervous System = The Parasympathetic Nervous System and the Sympathetic Nervous System.

Parasympathetic Nervous System Functions

Slows heart rate

Increases gastric secretion

Emptying of the bladder

Emptying of the bowel

Focusing the eye for near vision

Constriction of the pupil

Contraction of bronchial smooth muscle

Sympathetic Nervous System Functions

Regulation of the Cardiovascular System

*Maintenance of blood flow to the brain

*Redistribution of blood flow during exercise

*Compensation for blood loss

Regulation of Body Temperature

*Regulating blood flow to the skin

*Promotion of sweat secretion

*Inducing piloerection

Implementation of the "Fight or Flight" Reaction

*Increased heart rate and BP

*Shunting of blood away from the skin and viscera and into skeletal muscles

*Bronchial dilation

*Pupil dilation

*Mobilization of stored energy

Innervation: Some body structures are innervated by both kinds of nerves (sympathetic and parasympathetic) while some are innervated by only one or the other (Blood vessels are only innervated by sympathetic nerves). Dual innervation can have opposing effects or complementary effects.

Peripheral Nervous System Transmitters (There's a really good diagram of this on p. 107)

Acetylcholine is released:
- by all preganglionic neurons of the parasympathetic and sympathetic nervous systems.
- by all postganglionic neurons of the sympathetic nervous systems.
- by all motor neurons to skeletal muscles.
Norepinephrine is released:
- by postganglionic neurons of the sympathetic nervous system (except for those going to sweat glands - they release ACh).
Epinephrine is released:
- Released by the adrenal medulla
- Initiates the "Fight or Flight" response

Peripheral Nervous System Receptors

2 basic catergories = Cholinergic Receptors & Adrenergic Receptors

The natural transmitter for cholinergic receptors is ACh
Each of these types of receptors has subtypes, and drug action at these different subtypes increases selectivity.

Cholinergic Receptor Subtypes and Locations

Nicotinic_N	All autonomic nervous system ganglia (parasympathetic and sympathetic) and on cells of the adrenal medulla.
Nicotinic_M	Skeletal muscle (the neuromuscular junction)
Muscarinic	On all organs under the regulation of the parasympathetic nervous system (Eyes, heart, lungs, bladder, GI tract, sweat glands, sex organs, blood vessels)

Adrenergic Receptor Subtypes and Locations

alpha₁	Eyes, Blood Vessels, Male Sex Organs, Bladder Neck and Prostatic Capsule
alpha₂	Presynaptic Nerve Terminals
beta₁	Heart, Kidneys
beta₂	Arterioles (of the Heart, lungs and skeletal muscle), Bronchi, Uterus, Liver, Skeletal Muscle
dopamine	Kidneys

Adrenergic Receptor Subtypes and Their Transmitters

alpha₁	Epinephrine, Norepinephrine, Dopamine
alpha₂	Epinephrine, Norepinephrine
beta₁	Epinephrine, Norepinephrine, Dopamine
beta₂	Epinephrine
dopamine	Dopamine

A Few Last Words About Transmitters

ACh is degraded by acetylcholinesterase.

Norepinephrine, if not stored in vesicles for reuse following reuptake, will be destroyed by monoamine oxidase.

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