BIO 304 · Human Anatomy & Physiology
PNS & Autonomic Nervous System
Nervous System · Module 7
A reference for the PNS & ANS video. The peripheral nervous system carries information to and from the CNS. The autonomic branch runs everything you do not have to think about: heart rate, blood pressure, digestion, sweat.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet , print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice; type the term, click Reveal to check yourself.
- List the twelve cranial nerves and the primary function of each.
- Distinguish the somatic nervous system from the autonomic.
- Compare sympathetic and parasympathetic divisions by anatomical origin, ganglion location, and neurotransmitter.
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PNS Components
Twelve cranial nerves
- I Olfactorysmell (sensory only)
- II Opticvision (sensory only)
- III Oculomotormost eye movements, pupil constriction, lid
- IV Trochlearsuperior oblique eye muscle
- V Trigeminalface sensation; muscles of mastication
- VI Abducenslateral rectus eye muscle
- VII Facialfacial expression; anterior tongue taste; lacrimal & salivary
- VIII Vestibulocochlearhearing & equilibrium (sensory only)
- IX Glossopharyngealposterior tongue taste; pharynx; parotid
- X Vagusparasympathetic to thorax & abdomen; pharynx, larynx
- XI Accessorysternocleidomastoid, trapezius
- XII Hypoglossaltongue movement
Spinal nerves
- 31 pairsC1-C8, T1-T12, L1-L5, S1-S5, Co1
- Mixedboth sensory (dorsal root) and motor (ventral root)
- Dermatomeskin area supplied by one spinal nerve
- Plexusescervical, brachial, lumbar, sacral — networks of mixed fibers
Somatic vs Autonomic
Somatic vs autonomic
- Somaticvoluntary; one motor neuron to skeletal muscle; ACh; always excitatory
- Autonomicinvoluntary; two-neuron chain to smooth/cardiac muscle & glands; can be excitatory or inhibitory
Sympathetic (fight or flight)
- Originthoracolumbar (T1-L2) lateral horn
- Preganglionic axonshort; synapses near spinal cord (sympathetic chain or collateral ganglia)
- Postganglionic axonlong; reaches target
- Preganglionic NTacetylcholine on nicotinic receptor
- Postganglionic NTnorepinephrine on alpha/beta adrenergic (most targets)
- Adrenal medullamodified ganglion; secretes epinephrine and NE into bloodstream
Parasympathetic (rest & digest)
- Origincraniosacral: brainstem (III, VII, IX, X) and S2-S4
- Preganglionic axonlong; synapses in or near target organ
- Postganglionic axonshort
- Preganglionic NTacetylcholine on nicotinic
- Postganglionic NTacetylcholine on muscarinic
- Vagus (CN X)carries ~75% of parasympathetic output
Tone & targets
- Dual innervationmost organs get both branches with opposing effects
- Heartsymp speeds up, parasymp slows (resting vagal tone keeps HR low)
- Pupilsymp dilates, parasymp constricts
- Gutsymp slows, parasymp activates secretion and peristalsis
- Sweat glandssympathetic only, but use ACh (the exception)
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