Download - Introduction to the PNS
Peripheral Nervous System
Brian J. Piper, Ph.D., M.S.
The Nervous System
-------------------------------Enteric (digestive)
Goals
• Anatomy & Physiology of:– Somatic Nervous System– Autonomic Nervous System
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Meninges of the Spinal Cord
Spinal cord
Spinal cord
Pia mater
Arachnoid mater
Dura mater
Dorsal root
Dorsal root
Spinal nerve
Epidural space
(a) (b)
Ventral root
Dorsal rootganglion
Thoracicvertebra
Spinalnerve
Dorsal rootganglion
Subarachnoidspace
Dorsal branch(dorsal ramus)
Ventral branch(ventral ramus)
Ventral root
Epiduralspace
Body ofvertebra
Refresher I• Afferent: towards center (brain), ≈sensory• Efferent: away from center (brain), ≈motor• Ganglia: mass of cell bodies• Plexus: network of neurons
Refresher II
• Nicotinic: subtype of Acetycholine receptor
1530-1600
• Muscarinic: subtype of Acetycholine receptor
Jean Nicot Nicotiana tobaccum
Amanita muscaria
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Peripheral Nervous System
• Cranial nerves arising from the brain• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
• Spinal nerves arising from the spinal cord• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
12 Cranial Nerves
• On Old Olympic Towering Tops A Finn And German Viewed Some Hops
• Once One Openly Told Tourists About FightingVampires Gobling Various Antelope Herds
• Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
http://en.wikipedia.org/wiki/List_of_mnemonics_for_the_cranial_nerves
CN I: Olfactory
• Connect nasal cavity to temporal cortex• Substantial individual differences• Forms new neurons throughout life!
CN II: Optic
• Connects retina to thalamus (lateral geniculate nucleus)
• Partial decussation
CN VIII: Vestibulocochlear (Auditory)
• Connects cochlea to brainstem• Responsible for balance & hearing
Somatic Nervous System
• Voluntary Nervous System– Motor cell bodies in ventral horn– Send axons to muscle– Use Acetylcholine to stimulate
Autonomic NS: Two Neurons
ACh
Howland & Mycek (2006). Lippincott’s Illustrated Reviews: Pharmacology. p. 36.
ACh: Acetylcholine
Autonomic Nervous System• Autonomous “automatic”• Functions: blood pressure, heart rate, sleep, bladder
& bowel function• Sympathetic NS: “fight or flight”
• Parasympathetic NS: “rest & maintain”
Medulla: EpinephrineCortex: Cortisol
Walter Cannon
Automobile Analogy
Functional Consequences of Normal ANS Function
Sympathetic Parasympathetic
Heart Rate Increased Decreased
Blood pressure Increased Decreased
Bowel motility Decreased Increased
Lung Bronchodilation Bronchoconstriction
Pupils Dilation Constriction
Adrenal glands Catecholamine release -
Sexual function (males) Orgasm Erection
Bladder Increased sphincter tone Decreased sphincter tone
Parotid gland - Salivation
Low & Engstrom (2012). Disorders of the ANS. In Harrison’s VII, Ch 375, p. 3352.
Unbalanced
Sympathetic Parasympathetic
Heart Rate Increased < DecreasedBlood pressure Increased > decreased (mildly)
Bowel motility Decreased Increased
Lung Bronchodilation Bronchoconstriction
Pupils Dilation Constriction
Adrenal glands Catecholamine release -
Sexual function (males) Orgasm Erection
Bladder Increased sphincter tone < Decreased sphincter tone
Parotid gland - Salivation
Low & Engstrom (2012). Disorders of the ANS. In Harrison’s VII, Ch 375, p. 3352.
Sympathetic & Parasympathetic Innervation I
• Central components “accident” example
• All at once (Sym) versus individual components (PS)
Sympathetic versus Parasympathetic
Preganlionic projection: short long
ComparisonSympathetic Parasympathetic
Origin T1 to T12, L1, L2 CN III, VII, IX, X, S2, S3
Target organs Diffuse Localized
Transmitter Adrenergic Muscarinic
Amplification Yes (1:20) No (1:1)
Comparison of Somatic and Autonomic Nervous Systems
Somatic Sympathetic ParaSymp
# neurons 1 >1 2Myelinated Yes Pre-Gang Pre-Gang
Neuro-transmitter
ACh Pre: AChPost: NE, Ep
Pre: AChPost: ACh
Receptor Nicotinic Pre: NicPost: Adren
Pre: NicPost: mus
Light Reading
O:15 to 3:58: http://www.youtube.com/watch?v=sPS7GnromGo
ANS (Stress) & Health
• Top Causes of Death (2009):– 1) Heart Disease– 2) Cancer– 3) Chronic respiratory diseases– 4) Stroke– 5) Accidents– 6) Alzheimer’s – 7) Diabetes– 8) Influenza & pneumonia– 9) Kidney disease– 10) Suicide
http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_04.pdf