spinal nerve pairs
Numbered by level of vertebral column at which they emerge |
8 Cervical nerve pairs (C1-C8) |
12 Thoracic nerve pairs (T1-T12) |
5 Lumbar nerve pairs (L1-L5) |
5 Sacral nerve pairs (S1-S5) |
1 Coccygeal nerve pair |
4 major nerve plexuses
cervical plexus |
located in neck (C1-C4); individual nerves that come out from cervical plexus they supply muscles and skin of neck, upper shoulders and part of head with nerves; phrenic nerve exit plexus to innervate diaphragm |
brachial plexus |
located deep in shoulder; ventral rami C5 to T1; individual nerves from bracihal plexus innervate lower part of shoulder and entire arm |
lumbar plexus |
located in lumbar region of back; L1 to L4; femoral nerve exits; divides into branches and innervates thigh and leg |
sacral plexus |
located in pelvic cavity; L4 to S4; innervates skin of leg, posterior thigh muscles leg and foot muscles |
coccygeal plexus |
(S4-S5) skin of coccyx bone |
Motor Autonomic Pathways
preganglionic neuron |
impulses from CNS to autonomic ganglion |
postganglionic neuron |
lies outside CNS, synapses with a preganglionic neuron, terminates in a visceral effector |
AUTONOMIC NERVOUS SYSTEM
Sympathetic Effects (fight or flight) |
structure |
Parasympathetic Effects (rest and repair) |
Dilation of pupil |
eye |
constriction of pupil |
Stop secretion |
salivaryy glands |
secrete saliva |
speed up heartbeat |
heart rate |
Slow down heartbeat |
secrete adrenaline |
suprarenal glands |
None – not innervated |
dilate bronchioles |
respiratory system |
constrict bronchioles |
increase force of breakdown |
skeletal muscles |
non not innervated |
lipid breakdown |
adipose tissue |
none not innervated |
delay emptying |
urinary system |
empty bladder |
decrease motility |
digestive system |
increase motility |
Interaction of ANS Divisions
Sympathetic and parasympathetic divisions work together to keep many body functions within homeostatic range |
Both divisions innervate many same organs where actions antagonizeone another--dual innervation |
Allows sympathetic division to dominate during physically demanding periods |
Parasympathetic division preserves homeostasis in same organs between periods of increased physical activity |
AUTONOMIC TONE: neither division ever completely shut down • Constant amount of activity from each division |
Autonomic NTs: Acetylcholine
Axon terminal of autonomic neurons release one of two NTs |
1 Acetylcholine (Ach) |
Acetylcholine (Ach) cholinergic fibres |
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a. Released by preganglionic sympathetic neurons (excitatory) |
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b Released by pre- & postganglionic parasympathetic neurons |
Termination of Ach action is by acetylcholinesterase (AChE) |
Two types of cholinergic receptors: |
1 Nicotinic receptors – excitatory, found in ganglia (on postganglionic neuron) |
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2 Muscarinic receptors – excitatory or inhibitory, found in synapses with effector organs and sweat glands |
2 Norepinephrine |
released by adrenergic fibres; Released by most postganglionic sympathetic neurons |
Termination of actions of NE: |
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1Monoamine oxidase (MAO): enzyme breaks up NT for reuptake |
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2 Catechol-O-methyl transferase (COMT): enzyme metabolizes remaining NT |
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spinal nerve attaches to spinal cord 2 short roots
1 a ventral motor root |
2 a dorsal sensory root |
dorsal root ganglion |
swelling in dorsal root of each spinal nerve |
all spinal nerves are mixed nerves carrying sensory and motor fibers |
dermatomes vs myotomes
dermatome |
region of skin surface area supplied by sensory fibers pf a spinal nerve |
myotome |
skeletal muscle supplied by motor fibers of a spinal nerve |
cranial nerves
name = function ; number = order of emergence |
sensory cranial nerve |
axons of sensory neurons |
motor cranial nerve |
mostly axons of motor neurons little amt of sensory fibers |
mixed cranial nerve |
axons of sensory and motors neurons |
reflexes
Occurs over pathways- reflex arcs |
Cranial reflex |
center of reflex arc is in brain |
Spinal reflex |
center of reflex arc is in spinal cord |
Results in |
Somatic reflex |
contraction of skeletal muscles |
autonomic (visceral) reflex |
contraction of smooth or cardiac muscle or secretion by glands |
somatic reflexes
knee jerk (patellar reflex) |
extension of lower leg in response to tapping patellar tendon |
ankle jerk (achilles reflex) |
extension of foot in response to tapping Achilles tendon; muscle relaxation |
plantar reflex |
plantar flexion of all toes, slight turning in and flexion of anterior part of the foot;Response to stimulation of outer edge of the sole |
Babinski sign |
extension of great toe, possible fanning of toes, in response to stimulation of outer margin of sole of foot; Present in normal infants until ~18 mo. then becomes suppressed when corticospinal fibers become fully myelinated; In adults, a positive Babinski sign indicates upper motor neuron disorder |
Abdominal reflex |
drawing in of abdominal wall in response to stroking side of abdomen; Decreased or absent reflex may involve lesions of upper motor neurons |
Corneal reflex |
Winking in response to cornea being touched; Mediated by reflex arcs with cranial nerve V fibres, centers in pons, and motor fibres in cranial nerve VII |
Gag reflex |
triggered when visceral sensory nerve endings cranial nerve IX in posterior throat are stimulated |
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spinal nerves
ramus |
large branches that form after spinal nerve emerges from spinal canal |
dorsal ramus |
intercostal and thoracic nerves |
ventral ramus |
form networks of nerves called plexuses |
classify CNs
Some Say Marry Money, But My Brother Says Big Business Makes Money |
olfactory nerve CN I |
sense of smell; in nasal mucosa terminate in olfactory bulbs |
Optic Nerve CN II |
carries info from eyes to top of brain |
Oculomotor nerve CN III |
motor fibres mid brain to eye muscles; nerves of superior medial and inferior rectus and inferior oblique; control amt of light entering eye (up, down, medial, roll eyes) |
Trochlear Nerve CN IV |
smallest cranial nerve; motor fibers from midbrain to superior oblique muscles of eye (down and in) |
trigeminal nerve CN V |
3 branches: 1 opthalmic, maxillary, mandible; sensory neurons impulses from skin and mucosa of head and teeth; motor fibers extend to muscles of mastication through mandibular nerve (close jaw for chewing and swallowing) |
abducens nerve CN VI |
motor nerve lateral rectus muscle in eye; side to side movement |
facial nerve CN VII |
motor fibres originate from pons to superficial muscles of face and scalp; sensory taste buds to anterior 2/3 of the tongue |
vestibulocochlear nerve CN VIII |
vestibular nerve fibres originate in semicircular canals in inner ear and transmit impulses that result in sensations of equilibrium (Balance)/ cochlear nerve fibres originate in organ of corti in cochlea of inner ear and transmit impulses resulting in sensation of hearing |
glossopharyngeal nerve CN IX |
sensory fibres to taste buds in posterior 1/3 of tongue // motor fibres to the pharynx for swallowing |
vagus nerve CN X |
innervates most thoracic and abdominal viscera / swallowing and speaking |
accessory nerve CN XI |
motor nerve that is an "accessory" tp the vagus nerve; innervates muscles of speech, head and shoulders |
hypoglossal nerve CN XII |
motor fibres innervate muscles of tongue and provide voluntary control |
Autonomic NTs: Acetylcholine
Axon terminal of autonomic neurons release one of two NTs |
1 Acetylcholine (Ach) |
Acetylcholine (Ach) cholinergic fibres |
| |
a. Released by preganglionic sympathetic neurons (excitatory) |
| |
b Released by pre- & postganglionic parasympathetic neurons |
Termination of Ach action is by acetylcholinesterase (AChE) |
Two types of cholinergic receptors: |
1 Nicotinic receptors – excitatory, found in ganglia (on postganglionic neuron) |
| |
2 Muscarinic receptors – excitatory or inhibitory, found in synapses with effector organs and sweat glands |
2 Norepinephrine |
released by adrenergic fibres; Released by most postganglionic sympathetic neurons |
Termination of actions of NE: |
| |
1Monoamine oxidase (MAO): enzyme breaks up NT for reuptake |
| |
2 Catechol-O-methyl transferase (COMT): enzyme metabolizes remaining NT |
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