BIOL121: 06/10/26 (Mendel)

PNS

all neural structures outside brain and spinal cord

PART 1 = sensory receptors

PART 2 = nerves and their structure and repair

PART 3 = motor endings and activity

PART 4 = reflex activity

sensory receptor

specialized to respond to changes in environment (stimuli)

activation results in graded potentials triggering nerve impulses (action potential)

awareness of stimulus (sensation) and interpretation of meaning of stimulus (perception)

type of receptors (stimulus type)

MECHANORECEPTOR = respond to touch, pressure, vibration, stretch

THERMORECEPTOR = sensitive to changes in temperature before pain

PHTORECEPTOR = respond to light energy (retina)

CHEMORECEPTOR = respond to chemicals (smell, taste, changes in blood chemistry

NOCICEPTORS = sensitive to pain causing stimuli (substance P)

perception of pain

release neurotransmitters glutamate and substance P

some pain impulses blocked by endorphins and enkephalins

VISCERAL = stimulation of visceral organ receptors

REFERRED = pain from one body region perceived coming from different region

PNS layers

ENDONEURIUM = loos connective tissue that encloses axons and their myelin sheaths (schwann cells)

PERINEURIUM = coarse connective tissue that bundles fibers into fascicles

EPINEURIUM = tough fibrous sheath around all fascicles to form the nerve

types of fibers in mixed nerves

SOMATIC AFFERENT = sensory from muscle to brain

SOMATIC EFFERENT = motor from brain to muscle

VISCERAL AFFERENT = sensory from organs to brain

VISCERAL EFFERENT = motor from brain to organs

cranial nerves acronym

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cranial nerves

I. Olfactory = smell

II. Optic = vision, axons from retina

III. Oculomotor = 4/6 extrinsic eye muscle, pupil, eyelid

IV. Trochlear = motor to superior oblique (eye)

V. Trigeminal = 3 branches to face, largest, chewing

VI. Abducens = abduction lateral rectus (eye)

VII. Facial = anterior 2/3 tongue, motor face

VIII. Vestibulocochlear = balance and hearing

IX. Glossopharyngeal = tongue/throat, swallowing

X. Vagus = motor to guts only sympathetic, rest and digest

XI. Accessory = shrug shoulder, from C1-C5

XII. Hypoglossal = stick tongue out, muscles under tongue

pairs of spinal nerves

CERVICAL = 8 (C1-C8) C1 above C1 vertebrae

THORACIC = (T1-T12)

LUMBAR = (L1-L5)

SACRAL = 5 (S1-S5)

COCCYGEAL = 1 (C0)

cervical plexus

innervates neck and back of head (NOT FACE)

VENTRAL RAMI C1-C4 = innervate skin of neck, ear, back of head, shoulders

PHRENIC NERVE C3-C5 = motor and sensory nerve of diaphragm (breathing) irritation causes hiccups

brachial plexus

VENTRAL RAMI C5-C8, T1 = nerves innervating upper limb (arms)

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Root, Trunk, Division, Cord, Branch

axillary, musculocutaneous, radial, median, ulnar

lumbar plexus

innervates front of leg (L1-L4)

FEMORAL NERVE = largest, innervates quads and skin of anterior thigh and medial surface of leg

OBTURATOR NERVE = innervate adductor muscles

sacral plexus

innervates back of leg (L4-S4)

S2-S4 “keeps it off the floor” = regulates bowel and bladder

SCIATIC NERVE= longest and thickest nerve of body

connus medularis

where spinal cord ends L2/L3

cauda equina

continuation of nerves past cord end

L3-C0

spinal rami vs root

DORSAL RAMI = innervate back muscles

VENTRAL RAMI = form plexuses

DORSAL ROOT = sensory afferent (cell bodies)

VENTRAL ROOT = motor efferent

reflex activity

INBORN (INTRINSIC) REFLEX = rapid, involuntary, predictable motor response to stimulus (maintain posture, control visceral activates)

LEARNED (ACQUIRED) REFLEXES = reflexes from practice or repetition

TENDON RELFEX = help prevent damage due to excessive stretch

FLEXOR (WITHDRAWAL) REFLEX = causes automatic withdrawal of threatened body part