1. Autonomic Nervous System
Organization
Comparison of peripheral
nervous system
Components of the ANS
Receptors/neurotransmitters
Hypothalamic control
Visceral function

2. Homeostasis & Organization
Maintenance of the internal environment – what else?
Visceral efferent division of the human nervous system
respond via contraction/relaxation or secretion
conduction of sensory impulses back to NTS
feedback loop: visceral efferent & afferent system
Parasympathetic & sympathetic branches exit the spinal cord in different regions
- craniosacral & thoracolumbar

3. Distribution of PNS: cranial nerve nuclei in brainstem
Oculomotor (III)
Facial (VII)
Glossopharyngeal (IX)
Vagus (X)
Sacral spinal nerves
(S2-S4)

4. SNS arises from thoracic & lumbar spinal cord levels – forming sympathetic trunk
intermediolateral
(IML) cell column
(prevertebral)

5. Autonomic sympathetic & parasympathetic pathways

6. Organization of Efferent Divisions of the ANS

7. Key questions for understanding organization & function of the ANS
1. How do the 2 autonomic branches differ anatomically?
2. The autonomic divisions are distinguished biochemically by their neurotransmitters & receptors explain?

8. Cholinergic Receptors
Nicotinic receptors:
preganglionic receptor for both PSN & SNS, at NMJ & in the adrenal medulla
responds to ACh; produce excitation ® binding opens ion channels influx of Na+ & efflux of K+
Muscarinic receptors (M1 & M2):
postganglionic for PSN; located in heart, smooth muscle & glands; respond to ACh
M1 receptor: IP3 is second messenger and ­ IC [Ca2+]
M2 receptor: inhibits adenylate cyclase result is ¯ [cAMP] & slows rate of depolarization

9. Adrenergic Receptors
receptor activation mechanism location produces of action
a1 skin & splanchnic excitation formation of IP3
vascular SM, GI & ­ IC [Ca2+]
& bladder sphincters
a2 walls of GI tract inhibition inhibit adenylate
fat cells & platelets cyclase, ¯ [cAMP]
b1 heart excitation produce cAMP,
activate adenylate
b2 GI tract & bladder relaxation same as b1
vascular & bronchial SM

10. Synapses in Autonomic Nerves
Varicosities
NT released to ECF
No cleft
Effect:
large area
slow acting
long duration
Synapses in Autonomic Nerves

11. Summary of two branches of the ANS

12. Comparison of the Somatic & Autonomic Nervous Systems
ANS: is a two-neuron system:
preganglionic fibers & postganglionic fibers
self-governed
exclusively a reflex system
innervates smooth muscle, viscera & glands
ACh & norepinephrine (NE) -- neurotransmitters
Somatic nervous system: cell bodies in the CNS – axons extend to skeletal muscle:
lack ganglia (single-neuron system)
voluntary/reflex system
innervate skeletal muscle
ACh is excitatory neurotransmitter

13. Adrenal Medulla: an extension of the SN S
acts like a combined autonomic ganglion & postsynaptic sympathetic nerve
releases epinephrine & norepinephrine (E = 80% & NE = 20%)
action of adrenals are under control of the hypothalamus

14. Hypothalamus Has Central Control of the ANS
Integrates autonomic & neuro- endocrine functions; serves as a homeostatic center
Coordinates visceral activities in response to changes in environment
Final common pathway is located in brainstem

15. ANS & Visceral Function
Structure SNS Stimulation PNS Stimulation
iris pupil dilation pupil constriction
salivary glands ­ saliva production ­ saliva production heart ­ HR, conduction/force ¯ HR & conduction
blood vessels vasoconstrict/dilatate
lung relax SM SM contraction
GI tract ¯ motility peristalsis, ­ motility ­ digestion
liver glycogenolysis conserve glucose
kidney ¯ GFR ­ urine secretion
sweat glands ­ sweating
bladder wall relaxed, sphincter wall contracted closed sphincter relaxed