PNS exam Flashcards
PNS components and associated structures
nerve fibers and cell bodies OUTSIDE THE CNS that conduct impulses to/away from the CNS
cranial and spinal nerves
nerve
cord-like organ made up of parallel bundles of peripheral axons enclosed by successive wrappings of CT
ganglion
collection of PNS nerve cell bodies
outside the cord in dorsal root ganglion
anterior horn of ventral root
nerve fiber consists of
axon, neurilemma, and surrounding endoneurial CT
endoneurium
delicate loose CT that surrounds the axons and neurilemma
perineurium
single layer of dense CT that encloses a fascicle and provides protection against foreign substances
epineurium
tough fibrous sheath that encloses all the fascicles
includes fatty tissue, bv, and lymphatics
classification of nerves: sensory/afferent
carries impulses towards the CNS
classification of nerves: motor/efferent
carries impulses away from the CNS to effectors
classification of nerves: mixed
most common
carry motor+sensory info to and from the CNS
a damaged neuron can regenerate only if
the soma remains intact
nerve regeneration
- wallerian degen- separated ends of the axon seal themselves off and swell disintegrating the distal part of the axon
- macrophages remove debris to clean out the dead axon leaving the myelin sheath intact and they stimulate schwann cells to divide
- schwann cells form a regeneration tube that the axon filament sprouts grow thru to be guided across the gap to their original contacts
- the axon regenerates and a new myelin sheath forms
cranial nerve I
olfactory
sensory/afferent for smell
cranial nerve II
optic
sensory/afferent for vision
cranial nerve III
oculomotor motor and parasympathetic fibers for eye movement elevation of eyelid pupil constriction+ ciliary muscle
cranial nerve IV
trochlear
motor to supply superior oblique muscle
smallest nerve but longest pathway
cranial nerve V
trigeminal mixed motor for mastication sensory for face divided into opthalamic, maxillary, and mandibular
cranial nerve VI
abducens
motor
serves lateral rectus muscle allowing eye to abduct
cranial nerve VII
facial
mixed (stylomastoid foramen) mainly for smile/laugh
motor for muscles of face and scalp
sensory for taste buds
*parasympathetic fibers for salivary and lacrimal glands
cranial nerve VIII
vestibulochochlear
sensory
vestibular nerve for equilbruim
cochlear nerve for hearing
cranial nerve IX
glossopharyngeal
parasympathetic fibers
mixed (jugular foramen)
motor for muscles of pharynx/salivary glands
sensory for pharynx sensation, tonsils, posterior 1/3 of tongue, bp in carotid arteries
cranial nerve X
vagus
mixed (jugular foramen)
motor/ paraympathetic (except swallow), supplies heart, lungs, abdominal viscera, involved in heart rate/breathing/digestion
sensory for impulses from thoracic/abdominal viscera, aortic/carotid chemoreceptors and taste buds on tongue and pharynx
only cranial nerve to extend beyond head/neck to thorax/abdomen
cranial nerve XI
accessory
mixed (jugular foramen)
motor ctrls muscles of pharynx, sternocleidomastoid, trapezius,
sensory for proprioceptors of above muscles
cranial nerve XII
hypoglossal mixed motor for muscle of tongue sensory for proprioceptors of tongue allows food mixing/manip by tongue and swallowing and speech involving the tongue
spinal nerves
initially arise from spinal cord as rootless but converge to form 2 nerve roots
all are mixed nerves
8 cervical, 12 thoracic, 5 lumbar, 5 coccygeal
31 pairs
dorsal root
sensory/afferent info
cell bodies are located outside the cord in dorsal root ganglion
ventral root
motor/efferent info
cell bodies lie in anterior horn
posterior dorsal ramus
serves deep muscles and skin of dorsal trunk
anterior ventral ramus
serves muscles/structures of upper/lower limbs and skin of lateral/ventral trunk
rami communicates
autonomic visceral sympathetic nerve fibers
cranial nerves for eye movement
III oculomotor
IV trochlear
VI abducens
cranial nerves that are mostly sensory
I olfactory
II optic
VIII vestibulocochlear
cranial nerves with parasympathetic fibers that serve visceral muscles and glands
III oculomotor
VII facial
IX glossopharyngeal
X vagus
plexus
network of tangled nerves that mostly serve limbs
formed by ventral rami
each end of the plexus contains fibers from several spinal nerves
cervical plexus
C1-C4
phrenic nerve C3-C5
most important nerve
sensory/motor fibers to diaphragm
brachial plexus
C5-C8 and T1
entire nerve supply to upper extremities, neck, and shoulder muscles
radial, median, ulnar
lumbar plexus
L1-L4
abdominal wall, external genitals, part of lower extremities
femoral-largest part of lumbar plexus serves thigh, buttocks, and lower extremities
sacral plexus
L4-L5 and S1-S4
sciatic nerve-thickest and longest of all
serves anterior thigh muscles, and medial surface of leg knee-foot
spinal nerve in charge of contracting the diaphragm
phrenic nerve C3-C5
radial nerve
part of brachial plexus
goes under olecranon- called the funny bone
ulnar nerve
part of brachial plexus
on the medial side of the arm, innervates the pinky and ring finger
median nerve
part of brachial plexus
innervates thumb, index, and middle finger
can cause carpal tunnel
somatic nervous system
peripheral nerve fibers for voluntary motor info (excitatory) to the skeletal muscle
reflexive movements
a single neuron arising from ventral horns
ACH is only neurotransmitter
autonomic nervous system
ctrls smooth muscle of viscera/internal organs and glands
sympathetic, parasympathetic, and enteric
somatic effectors, pathways, and neurotrans
effector: skeletal muscle
effector pathway: single heavily myelinated neuron
neurotrans: ACH
autonomic effectors, pathways, and neurotrans
effector: smooth/cardiac muscles and glands
effector pathway: 2 neurons; pregang 1 light myel neuron, post gang 1 unmyel neuron
neurotrans: pregang- ACH, post gang NRE stim, ACH inhibit
ANS sympathetic division origin, length of fibers, neurotransmitters
origin: thoracic and lumbar
length of fibers: pregang-long, postgang- short
neurotrans: pregang-ACH, postgang NRE
sympathetic division innervation
pupil-dialates salivary glands-inhibits heart-accelerates lungs- dialates bronchi digestive- inhibits liver- converts glycogen to glucose bladder-inhibits contraction/release secretes adrenaline and Noreadrenaline
ANS parasympathetic division origin, length of fibers, and neurotrans
origin: cranial nerves and sacral
length of fibers: pregang-short, postgang-long
neurotransmitter: pregang ACH, postgang-ACH
parasympathetic division innervation
pupil-constricts salivary glands- stimulates heart-slows lungs- bronchi constrict digestive- stimulates peristalsis and secretion liver- stimulates bile release bladder- contracts and release
main functions of general sensory receptors and special senses
keep us aware and able to respond to stimuli in envt
allow survival
special senses allow for vision, olfaction, taste, hearing, equilibrium
by stimulus
mechanoreceptors
touch pressure vibration stretch itch meissners corpuscles
by stimulus
thermoreceptors
free nerve endings
sensitive to temperature changes
by stimulus
photoreceptors
in retina
resp to light
by stimulus
chemoreceptors
in hypothalamus, vomiting center, heart
smell
taste
changes in blood chemistry
by stimulus
noiceptor
free nerve endings
sensitive to pain causing stimuli
by location
exteroceptors
found near the body surface respond to stimuli arising outside the body touch pressure pain temperature and special sense organs
by location
interoceptors
found in internal viscera/bv resp to stimuli arising within the body chemical changes stretch temperature changes
proprioceptors
interoceptor that responds to degree of organ stretch in skeletal muscles, tendons, joints, ligaments, CT coverings
constantly advise the brain of movement
the 5 special senses are
vision olfaction taste hearing equilibrium
accessory eye structures: eyebrows
coarse hairs that overlie supraorbital margins to shade the eye and stop perspiration from reaching the eye
accessory eye structure: eyelids
overlying skin that protects the eye anteriorly and produces lubricating mucus to keep the eye from drying out
accessory eye structure: tarsal glands
secrete whitish oily fatty substance
accessory eye structure: lacrimal apparatus
lacrimal glands and associated ducts
secrete tears; a dilute saline solution with mucous, antibodies, and lysozymes
accessory eye structure: lens
biconvex transparent avascular structure that allows precise focus of light on to the retina
composed of simple cuboidal epithelium in the anterior cells that differentiate into lens fibers
and lens fibers-cells filled with transparent protein crystalin
fibrous tunic of eyeball
slcera-protection and anchoring of extrinsic muscles; covered by conjuntiva
cornea- curved to help focus light on the retina
vascular tunic (uvea)
choroid- highly vascularized dark brown membrane bt sclera and retina that helps absorb light and supplies blood to all tunics
ciliary body-thickened ring of tissue surrounding the lens ciliary muscles are smooth muscle bundles to ctrl lens shape
ciliary processes secrete aqueous humor and anchor suspensory ligament that holds the lens in place
iris and pupil- colored part of eye ctrl amt of light
sensory tunic (retina)
ora serrata- attaches ciliary body to sensory tunic
2 layer membrane- pigmented layer that absorbs light/prevents scattering/acts like phagocytes; retina- multi layered outgrowth of brain w photo receptors, bipolar cells, ganglion that joins optic disk and leaves as optic nerve
anterior chamber
bt cornea and iris
cont aqueous humor- a plasma like fluid that drains via canal of schlemm (scleral venous sinus)
supports nourishes and removes waste
posterior chamber
bt iris and lens
cont vitreous humor- clear gel that supports the posterior surface of the lens; and holds the neural retina firmly against the pigmented layer
main structure of the eye that regulates the amout of light passing to the visual receptors of the eye
pupil
flow of light
cornea–aqueous humor of anterior seg–pupil-lens–vitreous humor of posterior segment–ganglion cells–bipolar cells–photoreceptors
rods
sensitive to dim light best suited for night vision/peripheral vision 1 photopigment-rhodopsin input in gray tones fuzzy/indistinct images
cones
high acuity color vision
requires bright light for activation (low sensitivity)
detailed and high res in blue, red, and green
found in macula lutea and concentrated in fovea capitis
arrangement of photopigments
rods/cones arranged in a stack of disk like infoldings of plasma membrane that change shape as they absorb light
visual pigments
colored proteins that undergo structural changes when they absorb light creating potentials
opsin-
visual pigment
glycoprotein bound to retinal
4 types
retinal
derivative of vit A
light absorbing part
wavelength depends on which opsin is attached
visual transduction of rods
bleaching of pigment- breakdown of retinal opsin combo;
regeneration- retinal binds to opsin
rhodopsin- deep purple pigment in rods that absorbs blue-green
visual transduction of cones
visual pigments retinal and opsin
dark- continual release of glutamate–no vision
light-no glutamate–light+vision
smell
olfactory epithelium
covers superior part of nasal cavity
bipolar neurons with radiating olfactory CILIA embedded in mucus
taste
taste buds found in papillae on tongue
bud made up of supporting cells that insulatethe receptor, basal cells/stem cells, GUSTATORY HAIRS that bind molecules and release serotonin and ATP
activation of smell
- olfactory receptors bind odor causing chemicals
- use CAMP as 2nd messenger to initiate G protein mechanism
- CAMP opens NaCa+ channels to trigger an action potential
activation of taste
- chemical must be dissolved in saliva and bound to gustatory hairs
- binding of food chemical depolarizes taste cell membrane releasing neurotransmitter and initiating action potential and starting digestion
- thermoreceptors, mechanoreceptors, nociceptors, and texture influence taste
5 different tastes
sweet-sugars, saccharin, alcohol, aminos
salt-metal ions like NaCl
sour- acids H+
bitter- alkaloids like caffeine and nicotine
umami- meaty flavor from aminos, glutamate, aspartate
papillae that contain taste buds
foliate
fungiform
circumvallate
composition of a taste bud
supporting cells-insulate the receptor
basal cells-dynamic stem cells
gustatory hairs- taste cells
outer ear composed of
auricle (pinna)- helix/rim and lobule
external acoustic meatus-short curved tube filled w ceruminous glands
typmanic memb- CT memb bt outer/mid ear that vibrates and transfers sound energy to ossicles
middle ear
small air filled mucosa lined cavity flanked laterally by tympanic memb and flanked medially by oval and round windows
pharyngotympanic tube- equalizes pressure in middle ear w external air
ossicles- (malleus, incus, stapes) transmit vibratory motion of tympanic membrane to oval window
inner ear
cochlea_ spiral conical bony chamber that is divided into
scala vestibuli-upper, connected to oval window, perilymph
scala tympani- lower, terminates at round window serves as pressure valve, perilymph
scala media- middle cochlear duct filled with endolymph, high K+ conc
receptor for hearing is
the organ of corti
part of inner ear enclosed by tectorial memb- upper memb touched by hairs; and basal memb- separates scala media from scala tympani, where hair cells are embedded
two groups of hair cells in the inner ear
inner cells- single row
outer cells-three rows
sterocilia on the apical side of cells
extend to endolymph of scala media
long microvilli arranged in several rows of graded height (longest called kinocilium)
at basal end both types of cells synapse w sensory neurons from the cochlear branch of CN VIII
physiology of sound
- sound vibrations beat on tympanic membrane
- tympanic memb pushes against the ossicles which press fluid in the inner ear against oval/round windows setting shearing forces that pull hairs
3 cilia bend towards kinocilium
-opens mech gated K+ channels
-cause graded pot and release of neurotrans
-neurotrans cause cochlea fibers to trans impulses to brain where sound is received
vestibule
central egg shaped cavity of bony labyrinth; 2 sacs depended in perilymph,
saccule-extends 2 cochlea- resp to verticle mvmt
utricle-extends to semicircular canals-resp to horiz mvmt
static equilbruim
macula of vestibula
monitor pos of head in space and controls posture
resp to speed/direction but not rotation
supporting cells and hair cells
-each hair has stereocilia +kinocilium in the otolithic memb- jelly like mass studded w tiny calcium carbonate stones called otoliths
static equilbruim activation
otolithic mvmt in direction of kinocilia-depol vestibular nerve fibers, increase number of AP
otholithic mvmt away from kinocilia- hyperpol/ reduces the rate of impulses
either way the brain is informed of changing pos of head bc hair cells synapse w fibers of vestibular nerve
dynamic equilbrium
crista ampularis of semicircular canals
ampula-swollen end of each canal-has eq receptors called crista ampularis
resp to angular mvmts of head
each has support cells and hair cells that extend to a gel like mass called cupula
dendrites of vestibular nerve encircle base of hair cells
dynamic eq activation
resp to changes in velocity of rotary head mvmts
directional bending of hair cells in cristae causes
depol, rapid impulses that reach the brain at a faster rate
hyper pol few impulses reach the brain
this informs brain of rotational info
main reason for motion sickness is
that visual input doesnt match eq input
vision
receptor by stimulus: photoreceptor
location: retina
smell
receptor by stimulus: chemoreceptor
location: olfactory epithelium; cilia
taste
receptor by stimulus: chemoreceptor
location: taste buds; gustatory hairs
hearing
receptor by stimulus: mechanoreceptor
location: organ of corti
static eq
receptor by stimulus: mechanorecptor
location: vestibule-macule
dynamic eq
receptor by stimulus: mechanoreceptor
location: semicircular canals-crista ampularis
