Peripheral Nervous system
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PNS divisions
Afferent - Carries info from receptors to CNS. Efferent - Carries info from CNS to effectors.
Afferent (sensory) division
Somatic - Carry info from receptors in skeletal muscles and joints. Visceral - Carry info from internal receptors.
Efferent (motor) division
Somatic - External - Carry info to effectors in voluntary skeletal muscles. Autonomic - Internal - Carry info to effectors in involuntary muscles and glands.
Sympathetic nervous system
Produces responses that prepare body for strenuous physical activity. • Slower digestion/ movement of peristalsis. • Perspiration (sweating). • Dilation of pupils. • Decrease saliva production. • Increased heart rate-constriction of blood vessels.
Parasympathetic nervous system
Maintains body during rest conditions. • Increase movement stomach/intestine. • Increase uptake glucose in liver. • Constrict pupils. • Increase secretion of saliva. • Decrease heart rate.
Cranial nerves
12 pairs of nerves arising from brain. • Some are mixed nerves – both sensory and motor fibres. • Others are purely sensory or motor. • E.g. optic nerve/auditory nerve/olfactory nerve.
Spinal nerves
31 pairs of nerves arising from spinal cord. • All are mixed nerves arranged in pairs. • Nerves are joined to spinal cord by roots.
Ventral root
Joins motor nerve to S.C.
Dorsal root
• Joins sensory nerve to S.C. • Contains a ganglion (a group of nerve cell bodies which lie outside CNS). • Dorsal root ganglion (small swelling on side of dorsal root).