Honors Anatomy & Physiology Chapter 13

1. Thermoreceptors:  respond to temperature change 2. Mechanoreceptors:  respond to mechanical force: touch, pressure, vibration, stretch 3. Photoreceptors:  respond to light 4. Chemoreceptors:  respond to chemicals in solution 5. Nociceptors:  respond to pain

 activated by: 1. extremes of pressure & temperature 2. Chemicals  histamine  K+  ATP  acids  bradykinin

Sharp Pain  myelinated A delta fibers Burning Pain  unmyelinated C fibers

 pain stimuli arising in one part perceived as pain from another part  example: pain from heart attack can be felt as pain in medial aspect of left arm  cause: T1 – T5 spinal segments innervate both

 12 paired on base of brain  name refers to their function  numbered by Roman numerals  I and II attach to forebrain  III – XII brain stem

 sensory only  nasal mucosa  synapse in olfactory bulbs

 test: have patient smell ammonia  damage: anosmia (total loss)  olfactory receptors are bipolar neurons  each: single odor-sensitive dendrite

 sensory only

 test:  vision: eye chart  visual fields: mark chart at point patient first sees an object  view fundus with opthalmoscopeto check for swelling of optic disc (where optic n. leaves eyeball) & examine blood vessels *only place in body can directly visualize vessels  damage: II: blindess in affected eye if beyond optic chiasma  partial loss

 “eye mover”  motor mostly (only sensory proprioceptors)  somatic  4 of 6 extrinsic eye muscles  parasympathetic  circular muscles of iris (constriction of pupil) & to ciliary muscle (controls shape of lens for focusing)

 test: examine pupils for size, shape, symmetry  damage:  eye cannot be moved up, down, or rest eye rotates laterally  upper eyelid droops ( ptosis )  patient has double vision &trouble focusing on close objects

 “pulley”  motor  sensory: proprioceptors  supplies extrinsic eye muscle that loops through a pulley- shaped ligament (superior oblique muscle)

 test: eye movement  down & out  damage: double vision & impairs ability to rotate eye inferolaterally

 3 branches  largest cranial nerve  sensory to face/ motor to chewing muscles

 test: check blink reflex, touch to side of face, clench teeth, move jaw side to side  damage: trigeminal neuralgia : worst pain known, inflammation of V, ? due to compression by a vessel – treatment: surgery

 motor only  controls eye muscle that abducts eyeball (lateral rectus)

 clinical test: check eye movements  rest eyeball rotates medially on affected side (internal strabismus)

 normal test  abnormal test

 mixed  sensory: taste anterior 2/3 of tongue  motor: muscles of facial expression; autonomic motor: lacrimal & salivary glands

 clinical test: test taste in anterior 2/3 of tongue, check symmetry of face, assess tearing (ammonia)  damage: Bell’s palsy - paralysis of facial muscles on affected side, +/- continuous tearing causing dry eye

 ? caused by herpes simplex which causes swelling & inflammation of facial nerve  treatment: corticosteroids  clinically: ask patient to smile

 mostly sensory: hearing & balance

 clinically:  check hearing by air & bone conduction  damage to  vestibular division  dizziness, nystagmus, loss of balance, nausea, vomiting  cochlear division  central deafness

 tongue & pharynx  mixed:  sensory: taste posterior 2/3 tongue, baroreceptors in carotid sinus, chemoreceptors in carotid bodies  motor: upper pharynx, autonomic fibers to parotid glands

 test:  check position of uvula: will deviate away from affected side when patient says “ahh”  check gag reflex  ask patient to speak & cough  taste check

 *only cranial nerve to extend beyond head & neck  Mixed:  Motor: somatic to muscles of pharynx & larynx/ parasympathetic to heart (HR), lungs (RR), abd viscera (peristalsis)  Sensory : from thoracic & abd viscera, chemoreceptors for respiration (carotid & aortic bodies) and taste bud in epiglottis, proprioceptors

 “the wanderer”  test: same as for IX  damage: hoarseness or loss of voice, dysphagia (difficulty swallowing),impaired digestive motility

 motor  trapezius & sternocleidomastoid  only sensory is proprioception  emerges from spinal cord (C1 – C5)  up thru foramen magnum  travels with X

 test: injury to 1 side causes head to turn to affected side (sternocleidomastoid); patient has weak shoulder shrug on affected side

 “below tongue”  mostly motor: tongue: controls movements of tongue that mix & manipulate food when chewing, also contributes to speech & & swallowing  test: protrude/ retract tongue, check for deviations

 31 pairs:  8 cevical C1 – C8  12 thoracic T1 – T12  5 lumbar L1 – L5  5 sacral S1 – S 5  4 coccygeal Co1 – Co5

 Ventral  motor (efferent) fibers  muscle  Dorsal  sensory (afferent)fibers  sensory receptors  both pass laterally from cord & the 2 unite to form a spinal nerve (1-2 cm)

 ramus = branch  supply entire somatic region of body (skeletal muscle & skin)  spinal nerve divides (1 -2 cm from vertebra)  1. dorsal ramus:  posterior body 2. ventral ramus :  anterior body + limbs 3. meningeal branch : reenters vertebral canal to innervate the meninges

 all ventral rami (except T2- T12) branch & join each other lateral to vertebrae forming complicated nerve networks called: nerve plexuses where fibers criss-cross (so each muscle receives innervation from >1 spinal nerve)  cervical plexus  brachial plexus  lumbar plexus  sacral plexus