AP Lab 2- PNS & Reflexes

I- Olfactory Nerve

function: smell

location: o-superior portion of nasal cavity & i- olfactory bulbs

pathology: loss of smell

II- optic nerve

function: sight

location: retina, optic foramina, optic chiasm, visual cortex

pathology: contralateral loss of vision

III- oculomotor nerve

function: ciliary muscles- adapt lens for eye focus, pupillary spinchter of iris

location: midbrain to motor muscles

pathology: focal issues, inability to move eye, light entry

IV- trochlear nerve

function: superior oblique muscle: medially rotate eye

location: nucleus near midbrain near oculomotor nerves

pathology: inability to control cross eyed movement, loss of motor

V- trigeminal nerve

BRANCH 1: OPTHALMIC

function: sensations from forehead, lacrimal glands, eyelids, ciliary bodies, nose sides

BRANCH 2: MAXILLARY

function: sensations from eyes to top teeth

BRANCH 3: MANDIBULAR

function: sensations from cheek, lower teeth, mandible, mouth floor
sensations on tongue: touch, temp, pressure, NOT taste

motor: mastication, biting, chewing

VI- abducens nerve

function: lateral rectus muscle, abducts and moves eye laterally

location: origin in pons

pathology: restricted lateral eye movement

VII- facial nerve

function: motor- 5 branches, innervates, scalp, neck muscles; sensory- taste from anterior 2/3 of tongue and proprioceptive signals of face and scalp

location: originates in pons and ends in pons and gustatory cortex

pathology: facial expression issues and loss of anterior taste

VIII- vestibulocochlear nerve

VESTIBULAR

function: orientation and movement of head

location: vestibular ganglion

COCHLEAR

function: sense of hearing

location: spiral ganglion

pathology: loss of hearing and equilibrium (balance), potential vertigo

IX- glossopharyngeal nerve

function: motor- innervates stylopharygenus muscle; sensory- taste of posterior tongue, Bp changes in carotid artery, blood chem changes

location: pharynx and larynx muscles, stimulate saliva glands

pathology: loss of swallow and reduction of saliva production while eating, position capabilities of tongue, loss of BP and B chemistry changes

X- vagus nerve

function: PNS activation and pharyngeal principal motor nerve innervation, aortic bodies and aortic arch

location: medulla to target tissue

pathology: loss of ear sensation, taste buds, neck, throat, larynx, loss of motor function for heart, GI organs, breathing rate, sweating

XI- accessory nerve

function: sternocleidomastoid and trapezius muscle function

location: cranial- medulla oblongata, spinal-C1-C6, arise from spinal cord

pathology: inability to move neck and shoulder

XII- hypoglossal nerve

function: extrinsic and intrinsic control muscle of speech and swallowing

location: medulla to tongue

pathology: difficulty swallowing and speaking

PNS- somatic function

*voluntary control of skeletal muscle

*sensory signals from environment

*sensory receptors > spinal nerves > ascending tract of spinal cord > processed in cerebral cortex

PNS- autonomic function

heart rate, respiration, visceral organs, monitors internal conditions, involuntary

skin sensory receptors function

convey signals for tactile sensations

meissner corpuscles

touch

merkel cells

light touch, pressure, vibration

pacician corpuscles

pressure, vibration

free nerve endings

pain, temp, itch, tickle

cervical plexus

transverse cervical, great auricula, lesser occipital, supraclavicular, phrenic

brachial plexus

supra/subscapular, thoracodorsal, axillary, medial/lateral pectoral, musculocutaneous, median, radial/ulnar

lumbosacral plexus

femoral, illioinguinal, sciatic, gluteal

cranial nerve saying

On Old Olympus Towering Tops A Finely Vested Gunman Viewed A Hop

sensory/motor saying

Some Say Marry Money, But My Brother Says Big Brains Matter More

reflex arc

*neural pathway that allows for sensory neurons to not pass directly into brain but synapse in spinal cord to allow for quick reflexes

*spinal motor neurons activate without delay of routing signals through brain (brain will receive sensory input while reflex action occurs)

reflex

*rapid, predictable response to stimulus

*prevents us from thinking about small details (EX: posture)

*learned or inborn

learned reflexes

*acquired

*driving, salivation, playing instrument, reacting in sports

inborn reflexes

coughing, suckling, swallowing, sneezing

somatic reflex

*activate skeletal muscle

*mediated by spinal cord (no direct brain involvement)

*spastic vs flaccid paralysis

autonomic reflex

activate visceral effectors (cardiac muscle)

flaccid paralysis

*causes muscles to shrink and become flabby

*results in muscle weakness

spastic paralysis

*involves tight and hard muscles

*can cause muscles to twitch uncontrollably or spasm

components of reflex arc

receptors > afferent neuron > integration center > efferent neuron > effector (muscle)

integration center

component of reflex arc that consists if one or more synapses in CNS bw sensory and motor neuron

monosynaptic vs. polysynaptic

*based on on how many synapses occur in integration center

*greater number of synapses, more complex and slow reflex

monosynaptic reflex

*bicep, patellar, tricep reflex

*can not consciously inhibit pathway

polysynaptic reflex

*withdraw reflex: step on something sharp and immediately withdraw foot

*can consciously inhibit pathway

structures involved in somatic reflexes

*muscle spindles: sense length of muscle, sensitive to stretch, send self excitatory signals

*golgi tendon organ (GTO): located in tendon, senses tension on muscle and assoc tendon, sensory fiber send info to CNS via sensory fiber, self-inhibitory

stretch reflex

*caused by stretch in muscle- involves muscle spindles

*overall effect: stretched muscle will be activated and antagonist will be inhibited

*clinical implication: shows spinal cord intact at that point and excitability of spinal cord

steps of stretch reflex

*muscle stretched in quad

*spindle senses stretch, sends afferent signal to spinal cord

*afferent neuron synapses with motor neuron of quad and inhibitory neuron of hamstring

*result: quad contracts and hamstring relaxes

crossed-extensor reflex

*accompanies flexor reflex

*important in maintaining balance

*Ipsilateral withdrawal and contralateral extension

Ipsilateral withdrawal and contarlateral extension

*afferent sensory fibers from right arm to spinal cord interneurons

*efferent motor response to right arm, exciting stretched muscle and inhibiting antagonist → arm flexes

*efferent motor response to left arm, inhibiting flexors and exciting extensors → arm extends

Hypo-reflexia

*occurs when there is injury to lower motor neuron

*expected reflexes- less than expected or non-existent)

*WHY: sensory signal can not get to spinal cord or damage to motor neuron not allowing signal to reach effector

Hyper-reflexia

*occurs when injury to upper motor neuron

*expected reflexes- greater than expected

*WHY: reflex info can not be modified by CNS