SLHS4245W-EXAM2

proprioception

internal awareness of limb position in space

kinesthesia

internal awareness of limb movement

factors that impact localization of sensation

size of field, density. adaption rate

rapidly adapting

fire many frequent action potentials initially, as stimulus remains firing decreases dramatically

slowly adapting

begin firing action potentials at onset. and will continue to fire for as long as stimulus is present

anterolateral system

protopathic sensation, divided into lateral and anterior spinothalamic tracts

dorsal column medial leminiscal system

epicritic information, fine discriminative touch, and vibration, proprioception, and kinesthesia

afferent

sensory, dorsal root, body to brain

efferent

motor, ventral root, brain to body

fasciculus cuneatus

info from the upper half of the body in the DCML

fasciculus gracilis

info from the lower half of the body in the DCML

synapses in ventral posterior lateral nucleus

all somatosensory information from the neck down synapses in the ventral posterior lateral nucleus before being sent to the cortex

synapses in ventral posterior medial nucleus

somatosensory information from the neck up synapses in the ventral posterior medial nucleus of the thalamus

third order neurons

from the thalamus to cortex

second order neurons

from the spinal cord or the brainstem to thalamus (VPLN)

first order neurons

receptors to spinal cord or brainstem

(first order neuron) epicritic

ascends ipsilaterally and synapses in the medulla.

(first order neuron) protopathic

synapses in the spinal cord

epicritic (second order neuron)

decussates in the medulla, synapses in the thalamus

protopathic (second order neuron)

decussates in the spinal cord, from lateral and anterior spinothalamic tracts ascend and synapses in the thalamus

third order neuron desscusation

fibers pass from VPL of thalamus to upper 2/3 of primary somatosensory cortex

damage to spinal cord (complete transection)

results in loss of all sensation below the level of damage. all sensation above remains intact since axon pathways above the cut can still send signals in the brain

brown-sequard syndrome (hemisection)

loss of touch (epicritic) ipsilaterally due to damaged DCML which ascends ipsilaterally up spinal cord.. loss of pain and temperature (protopathic) sensation contra laterally due to damage to damaged anterolateral which ascends contralaterally up spinal cord

thalamic damage

may cause thalamic pain syndrome. and result in loss of perception of touch as pain, and painful stimuli is more painful

damage to the cortex

sensory loss in the contralateral body. all sensation (epiciritc and protopathic) are affected. may also cause hemiparesis (half-weakness) since primary and sensory ares are close together

finger agnosia

deficit in localizing or naming fingers

autotopagnosia

inability to identify body parts, ones own, another persons or even a picture

right left confusion

occurs in patients with dementia

Gerstmann syndrome

combination of finger agnosia, impairment In math (acalculia) and writing disorder (agraphia)

pupil

opening in which light waves enter

ciliary muscles

located in the iris. control the size of the pupil, innervated by the cranial nerves

pupil dialation

contraction of pupil=decreases amount of light, dilation=increases amount of light

refraction

focus light waves in the center of the retina on the posterior wall of the eyeball

retina

multilayered structure, photoreceptors, bipolar cells, ganglion cells…convert light into action potentials

Fovea

fovea and foveal pit are where visual acuity and color vision are the best due to high concentration of cones. maximal visual acuity

visual fields

the entire area you can see with one eye

retinal fields

the images represented on your retina, the same images as those you see in your visual field except that they are upside down and the right and left halfs are reversed

optic nerve

goes from retina to optic chaism

optic tract

goes from chaism, to LGB (lateral geniculate body/nucleus)

optic radiation fibers (geniculocalcarine)

goes from LGB (lateral geniculate body) to visual cortex

parallel processing

means the same information can travel along different cells and pathways…information is later reconstructed in the pathway

optic radiations (lower)

information from the lower visual fields take a more dorsal route and is delivered above the calcimine fissure in the occipital lobe

optic radiations (upper)

information from the upper visual fields takes a more ventral route and is delivered below the calcarine fissure in the occipital lobe

parietal lobe-visual processing

visual spatial processing and perception (right), reading, writing (left)

temporal lobe-visual processing

speech and language

dorsal pathway-visual

extending from the occipital lobe to the parietal lobe, known as the “where” pathway. functions: puts items into context of the environment, detecting and processing motion, using visual input to direct action…neurons in this pathway respond to movement and perceived movement

The ventral pathway

from occipital lobe to the parietal lobe and into the inferior temporal lobe known as the “what” pathway. functions= processing shape, color, and size of objects. recognizing faces, and objects. reading and writing

cortical blindness

can be bilateral but this is more rare, can sense and follow light, cannot process any other visual information

Anton syndrome (visual anosognosia)

person has cortical blindness but believes they can see, they will deny vision impairments when asked

damage to the dorsal pathway

difficulty recognizing an object, name it and describe it but not be able to point to it without searching with their hand

damage to the ventral pathway

results in deficits in recognizing objects known as apperceptive agnosia. can see object but looks like an unfamiliar mass. typically unable to read letters, copy simple shapes and lines/drawings

prosopagnosia

deficits in face recognition even though they are seeing and perceiving the face

Alexia without agraphia

can’t comprehend written language but can still write. very rare, damage to the occipital cortex and posterior portion of the corpus callousum

akinetopsia

inability to visually process motion/movement, like having a strobe light on constantly

visual apraxia

deficits in visa-spatial tasks like map reading

pinna

cartiligous outer ear, important for localizing sounds on the vertical plane

external auditory meatus

ends at the tympanic membrane, acoustic energy enters the outer ear in the form of sound pressures

middle ear

converts acoustic sound energy to mechanical energy, provides intensity amplification of sound before energy reaches the fluid filled middle ear

inner ear consists of

cochlea, vestibule, semicircular canals.

inner ear

converts hydraulic energy in the cochlea to neural impulses that can travel through the CNS to the brain

cochlear structure: scala vestibuli

filled with perilymph (high Na+ concentration)

cochlear structure: scala media

filled with endolymph (high K+ concentration)

cochlear structure: scala tympani

filled with perilymph (high Na+ concentration)

stria vascularis

absorbs NA and excretes K to maintain the correct concentrations in the endolymph

cochlear function

absorbs mechanical energy from ossicles, inside perilymph inside cochlea which displaces basilar membrane, transfers sound vibrations into neural impulses via the organ of corti

basilar membrane

narrow at the base and wider at the apex, narrow base is stiffer than wide apex. high frequencies=affects base, low frequencies=affects the apex

inner hair cells

afferent-ascending sensory neurons. info Into the cortex

outer hair cells

mostly efferent-descending motor neurons, returns feedback to the cochlea . generally inhibitory → important for impedance

properties of the auditory system

bilateral auditory representation- both ears send info to both hemispheres, tonotopic representation, sound source localization, descending auditory projections

vertical localization

sound waves are reflected off the structures in the pinna

horizontal localization

based on differences in timing and intensity of the signals from the left and right ears

conductive hearing loss

outer and middle ear issues, buildup of cerumen, torn or ruptured tympanic membrane, ear infections, damage to ossicles

sensorineural hearing loss

caused by damage to the cochlea or the auditory nerve, can be caused by presbycusis- normal wear and tear of hair cells associated with aging, exposure to loud noises, damage to the auditory nerve

cortical deafness

bilateral lesions of the primary auditory cortex, cochlea and nerves may continue to function but will not be able to make meaningful distinctions

auditory agnosia

pure word deafness: bilateral lesion in fibers connecting primary auditory cortex to the wernickes area. impaired: comprehension, repetition, writing of spoken words. intact: normal hearing thresholds, localization, can recognize reading, writing, speaking normal, can recognize non-speech sounds.

wernickes aphasia

impaired comprehension of language, produces words with intact grammar, syntax, rate and intonation but without meaning (words dont make sense)

Auditory verbal agnosia

impaired comprehension, repetition and writing of spoken words, able to read and write and speak normally .

semicircular canals

detect rotational acceleration, three canals (superior, posterior, lateral/horizontal)…end of canals called ampullae, ampullae each contains a Cristae

cristae

sheet of sensory cells into which hair cells are embedded

the vestibule

contains the utricle and the saccule. detects linear acceleration

contained in the vestibule: utricle and saccule

macula- sensory epithelium containing hair cells

gelatinous structure where cilia are embedded

otoconia- calcium carbonate crystals on top of the gelatinous portion