Outline-4, BIO 2310, Autonomic Nervous System


A. General classification & function

PNS, visceral efferent to smooth muscle, cardiac muscle and glands

B. Preganglionic & postganglionic neurons

Preganglionic neuron begins at CNS to ganglion and is myelinated. Postganglionic neuron begins at ganglion to effector and is unmyelinated.

C. Sympathetic division{expends energy}

1. Preganglionic neurons T1-L2 [short]

2. Sympathetic chain ganglia or trunk

a. White & Gray ramus communicans

White ramus is the branching of the preganglionic neuron from the spinal nerve; Gray ramus is the branching of the postganglionic neuron to rejoin the spinal nerve

b. Directly to postganglionic neuron [long]

c. Up or Down sympathetic chain ganglia

d. Through chain ganglia to Collateral =Prevertebral Ganglia

1. Splanchnic nerves -pertaining to viscera

2. Celiac ganglion

3. Superior mesenteric ganglion

4. Inferior mesenteric ganglion

e. Adrenal medulla

Preganglionic neuron only

3. Divergence

D. Parasympathetic division{conserves energy}

1. Cell body location

2. Not to skin, blood vessels

3. Brain stem {3,7,9,10}

4. S2-S4, Pelvic splanchnic nerves

E. Comparisons of anatomy between SNS & PNS

Short preganglionic neurons SNS, long postganglionic neurons SNS; opposite in PNS. More localized effects in PNS due to anatomy.

F. Neurotransmitters

1. Acetylcholine – Cholinergic

a. Parasympathetic {pre/postganglionic fibers}

b. Preganglionic fiber – SNS

2. Norepinephrine – Adrenergic

a. Postganglionic fiber – SNS

3. Adrenal medulla

Releases norepinephrine and epinephrine to exaggerate the fight or flight response

4. Receptors

a. Acetylcholine

1. Muscarinic [blocked by atropine]

2. Nicotinic [blocked by curare in somatic system]

b. Norepinephrine/epinephrine

1. Alpha

-Alpha 1 are most common and have a stimulatory response [constricts muscles]

-Responds to norepinephrine & epinephrine

2. Beta 1


Stimulatory effect

-Responds to norepinephrine & epinephrine

-Propranolol – B1 blocker

3. Beta 2

-Most common beta receptor

-Generally inhibitory

-Responds to only epinephrine

G. Functions

Heart – SNS increases rate and force of contraction, PNS decreases rate and force.

Airways – SNS dilates airways, PNS narrows airways

Digestive structures – SNS decreases secretions and peristalsis, PNS increases secretions and motility

Pupil – SNS dilates pupil, PNS constricts pupil

Sweat glands – SNS increases sweat secretion

Adrenal medulla – SNS causes release of epinephrine and norepinephrine from adrenal medulla

Urinary bladder – SNS causes wall to relax and sphincter to contract, PNS causes wall to contract and sphincter to relax

Cutaneous and abdominal blood vessels – SNS causes vasoconstriction

Skeletal muscle blood vessels – SNS causes vasodilation

H. Controls