Unit 13: Key Terms
Peripheral nervous system (PNS)
links CNS to the body and the external environment, detects sensory stimuli and delivers info to CNS as sensory input
Sensory division
consists of sensory (afferent) neurons that detect and transmit sensory stimuli to CNS, somatic and visceral divisions
Somatic Sensory Division
detects both internal and external stimuli, general sense receptors detect stimuli from skin, special sensory receptors detect stimuli from special sense organ
Visceral Sensory Division
relays internal information (blood pressure) from organs of abdominopelvic and thoracic cavities
Motor division
motor (efferent) neurons, carry out motor functions of nervous system, subdivisions based on organs that neurons contact, somatic and visceral divisions
Somatic motor division
voluntary motor functions, lower motor neurons (somatic motor neurons) that directly trigger skeletal muscle contractions
Visceral Motor division
autonomic motor nervous system (ANS), maintains many aspects of homeostasis by controlling involuntary motor functions in body, neurons innervate cardiac muscle cells, smooth muscle cells, and secretory cells of glands
ANS Division: Sympathetic nervous system
fight or flight division, homeostasis activities surrounding physcial work, and visceral responses of emotions
ANS Division: Parasympathetic system
Rest and digest division, digestion and maintaining body's homeostasis at rest
Peripheral nerves
main organs of PNS axons of many neurons bound together by connective tissue
innervate
nerves of PNS contact majority of structures in body
Mixed nerves
contain both sensory and motor neurons
Sensory nerves
contain only sensory neurons
Motor neurons
contain mostly motor neurons, also some sensory neurons involved in muscle stretch and tension
Spinal nerves
originate from spinal cord and innervate structures below head and neck, all 31 pairs of spinal nerves are mixed nerves
PNS connection with spinal cord's gray matter: Anterior Root
motor neurons from anterior horn
PNS connection to spinal cord' gray matter: Posterior Root
sensory neurons from posterior horn
Posterior root ganglion
(dorsal root ganglion), swollen area in the posterior root, houses cell bodies of sensory neurons
Spinal Nerve fuse
posterior and anterior roots fuse to form this, just lateral to posterior root ganglion
Epineurium
outermost layer of connective tissue, holds motor and sensory axons together
Fasicles
small groups of bundled axons surrounds by connective tissue perineurium
Endoneurium
each individual axon within fascicle is surrounded by this connective tissue
Cranial nerves
attach to brain, mostly innervate structures in head and neck, not formed by fusion, allow for purely sensory, mixed, and mostly motor nerves
3 cranial nerves contain axons of only sensory neurons
Olfactory, Optic, Vestibulocochlear
5 cranial nerves contain primarily axons of motor neurons
Oculomotor, Trochlear, Abducens, Accessory, Hypoglossal
4 cranial nerves contain axons of both sensory and motor
Trigeminal, Facial, Glossopharyngeal, Vagus
Spinal Nerve structure
short, divides into two mixed nerves, both carry somatic motor and sensory information
Anterior ramus
travels to anterior side of body and/or to an upper or lower limb
Posterior ramus
travels to posterior side of body
31 pairs of spinal nerves
8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar and sacral nerves, 1 pair of coccygeal nerves
Nerve Plexuses
complicated networks of nerves, anterior rami of cervical, lumbar and sacral spinal nerves each merge to form this
Brachial Plexuses
Axillary nerve, Radial nerve, Musculocutaneous nerve, Median nerve, Ulnar nerve
Lumbar Plexuses
Iliohypogastric nerve, Ilioinguinal nerve, Genitofemoral nerve, Lateral femoral cutaneous nerve, Obturator nerve
Sacral Plexuses
Superior gluteal nerve, Inferior gluteal nerve, Pudendal nerve, Posterior femoral cutaneous never, Sciatic nerve, Common fibular nerve, Tibial nerve