noxious stimuli = pain receptors
Describe the olfactory receptor cells
olfactory cilia are chemoreceptors, odours dissolve in mucus and bind to receptors
unusual that second order neuron is CN
first order afferent goes through the cribiform plate
Describe the olfactory pathways
first order neurons - through cribiform plate and synapse with the second order neurons in the olfactory bulb
second order neurons - travel along olfactory tract (CN1) to the primary olfactory area
third order neurons -thalamus and on to primary olfactory cortex
what is anosmia, hyposmia & hypersmia
unilat = inability to perceive odours
caused by colds, trauma, nasal polyps, allergy
Hyposmia - reduction in ability to perceive smells - caused by cold hay fever and sinusitis
Hyper - psycholgical background (AKA olfactory hyperesthesia)
specific anosmia - loss of selective odurant receptor - poss genetic basis
what is Olfactory Agnosia?
Can physically smell but not name odour, caused by Central Lesions
what is parosmia, phantosmia, cacosmia
distortion of smell
nasty/bad olfactory auras
what are the four primary modalities of taste?
sweet, salt, sour, bitter, savoury
name the four types of papilla, what is their function, which does not have taste buds
Filiform - have no taste buds
mircovilli act as chemoreceptors
name the nerve that are involved with taste
CNVII - Facial nerve - anterior 2/3 of tongue
CNIX - Glossopharyngeal - posterior 2/3 of tongue
CNX - Epiglottis and Pharynx
what is the taste pathway - Gustatory
first order neuron - receptor to brainstem via CN VII, IX, X
second order neuron - cross at level of the medulla ascend via central Tegmental tract to the thalamus
third order neuron - thalmus to the primary Gustatory cortex
what does Aguseia, hypogeusia, Dysgeusia and Cacoguesia mean?
Aguseia - bi lat taste loss
hypogeusia - decreased taste - age related
Dysgeusia - distortions in taste
Cacoguesia - bad tastes - linked with tumours or epilepsy
Describe the basic structure of the Ear
external ear - Pinna, ear canal sep by tympanic membrane
Middle Ear - Eustacian tube - links pharnx to the middle earossicular chain - pressure transmission and attenuation
inner ear - vestibular system and cochlea
controlled by CN 8
what is the purpose of the middle ear?
movement of the ossicular chain transmits sound waves to the inner ear through vibration. There are muscle that act to reduced the movement of the tympanic membrance and dampen vibration of the staples
what is the labyrinth of the ear comprised of?
bony: cavities in temperal bone filled wit PERILYMPH made of;
membranous: inside the bony part and filled with ENDOLYMPH
what is the role of the cochlea in hearing?
The cochlea is auditory portion of inner ear.
It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis
A core component of the cochlea is the Organ of Corti, contains sensory receptors
How do the hair cell help with hearing?
vibration is transmitted through the perilymph cause movement of the membrane boundaries of the organ of corti
this bend the cilia on the hair cell which activates the sensory fibres for CNVIII
the outer hair cells can change length to act as a cochlea amplifier
Describe the auditory pathway
First order: spiral ganglion to the cochlear branch of the CNVIII to the medulla to snapse with the second order neurons in the cochlear nuclei or the superior olive
second order: ipslat to the inferior colliculi or medial genticule nucleus
third to the auditory cortex
name the three types of auditory disturbances
How do you test for the difference
tuning folk test 256HZ - weber/rinne
comparison of air vs bone conduction , place tuning folk on the mastoid and then vibrate the folk by the person ear, bone should be shorter than ear this is a positve rinne test
in a conductive hearing loss bone will be better than air
in a sensory neurone loss there should be equal difference between the conduction and air loss thus no real difference should be noted
unilateral conductive hearing loss would be in ear with the hearing loss.
unilateral sensorineural loss would be heard better in the ear with out loss
what is conductive hearing loss? what are the causes
prevention of transmission of sound to the inner ears
causes include: wax, otitis media, tumour, otosclerosis
what is sensorineural hearing loss? what are the causes?
cause by damage to the cochlea of the CVVIII
common cause: old age, noise exposure, trauma, immune disorders, tumour (acoustic neuroma), medications (NSAIDS)
what are the causes of central hearing loss? causes
due to multiple areas involved
causes by brainstem lesions - damage to the inferior colliculi
define: auditory agnosia
able to hear the sounds but unable to interpret them
define pure word deafness
unable to distinguish between of verbal sounds
define cortical deafness
combination of auditory agnosia, pure word deafness, cortical deafness
how is balance controlled?
vestibular system comprises of the;
3 semicircular canals (each canal contains a ampulla which contrains a crista
utricle and saccule (otolith organs) - each contain a macula
macula - sense static head position
cristae sense kininetic/dynamic movement
describe the static Labyrinth
contains the macula which is in the uricle and the saccule
muculae contain hair cell embedded in the gel matrix (Ca crystals called otoconia)
each long hair cell has a long body and shorter cilia
when gravity acts on the sterocilia this cause movement towards the body and then depolarisation
Describe the dynamic
semicircular canals, ampulla contains a cristae
contain kinocilium hairs
head movement cause perilymph to move in the same direction an the endolymph to move in the opposite direction
displacement of the capula excites the nerve endings
describe the vestibular pathways
first order: afferent for the cristea and the macula travel vis CNVIII to the vestiular neclei of the brainstem
second order - give rise to vestibulo spinal tracts and project to hte medial longitudinal fasciculus to the thalamus
third order - from the thalamus project to the cortex
what is the vestibulo-ocular reflex?
vestibular rotation for the eye to maintain focus of an object
if head rotate to far than the ear flick back to find a new object to focus on
further rotation will cause a flicking back of the eye in alternating fast and slow movements -Nystagmus
Name some disorders of balance
explain their formation
vertigo - spinning sensation
caused by a misplacement of the ca crystals in the ear or central brain lesion
vestibular Nystagmus - uncontrollable oscillation of the eyes - fast phase is AWAY from side of the lesion
peripheral lesion = delayed
central = delayed or intermediate
How do you assess the vestibular nerve?
clinical tests - head thrust test - get pt to focus on your nose and move their head 30o
they should be a delay when pt is rotated to the side of the lesion
caloric tests - vestibulo-ocular reflex that involves irrigating cold or warm water or air into the external auditory canal.
COWS: Cold Opposite, Warm Same.
opposite side of the cold water filled ear