special senses Flashcards
what are the 4 senses?
1.Vision - sight
2.Olfaction - smell
3.Gustation - taste
4.Audition - hearing
5.Balance
what are special senses?
senses are called ‘special’ as they all utilise specialised organs and receptors in order to generate their sense
what is a specialised sensory cells?
transduces the stimulus, located within a specific sensory organ.
what 3 things do specific sensory organs include?
1.Smell and taste utilise specialised chemoreceptors.
2.Hearing and balance detect vibration and movement using specialised mechanoreceptors – hair cells.
3.Vision uses specialised photoreceptors
what nerves is sensory information carried through?
via cranial nerves into CNS for processing
vision - where are photosenstive cells located?
retina of the eye
what do photosensitive cells induce?
light waves into electric signals (phototransduction) and information travels along a distinct pathway to the occipital lobe and visual cortices for processing
what is the visual pathway made up of ?
Eye (retina)
Cranial nerve II – Optic nerve
Optic tract
Optic chiasm
Optic radiations
what information does the right side of the visual cortex receive?
receives information about the left field of vision and vice-versa
what 2 features the the eyeball exterior have?
Sclera - white
Cornea -clear
what 3 chambers does the eye have?
Anterior (aqueous humour)
Posterior (lens, supporting structures)
Vitreous (vitreous (gel-like) humour)
what is the iris of the eye?
muscular ring (ANS control CNIII)
what is the lens of the eyes?
focus light onto macula and fovea (focal point
what Is the retinal of the eye?
contains sensory receptors
what are the 2 features in the retinal?
Rods (low light - acuity)
Cones (colour – tuned to particular wavelengths – red/green/blue))
what is refraction?
light passes through a substance it is ben
how does refraction work in the eye?
eye light passes through the curved cornea, the differing densities of fluid, gel in the chambers and the curved dense structure of the lens.
what happens to the image when there is curves dense structures of the lens reaches the retina?
image is inverted
what happens after the retina- accommodation?
alters shape of the lens allowing the image to be focused on the macula and fovea
what is accommodation?
process of focussing light onto the macula and fovea by changing the lens shape, to get the best acuity (sharpness, clarity) of image
in accommodation what happens to the distant objects
Ciliary muscles are relaxed
Zonula fibres tense
Lens becomes stretched and thinner.
what are the close objects of accommodation ?
Ciliary muscle contracts
Zonula fibres relax
Lens becomes fatter and rounder
what are the function of distant object
keeps the light waves more spread out so that they don’t converge before they hit the retina
what are the function of close object?
bends the light waves at a greater angle to focus them on the fovea
what are the 6 muscles control the movement of the orbit in its socket?
4 x rectus muscles
2 x oblique muscles
what are controlled by 3 cranial nerves?
CNIII (oculomotor)
CNIV (trochlear)
CNVI (abducens)
what are the types of eye movement
1.vergence movement
2.saccades
3.smooth pursuit movement
4.vestibulo-cocular reflex(VOR)
Vergence movement
convergent and divergent eye movements to aid focus on near, distant objects
Saccades
rapid movement to change point of fixation (REM
Smooth pursuit movement
track moving objects to maintain focus on fovea
Vestibulo-ocular reflex (VOR)
account for head movements to maintain fixed point
what are some vergence movements ?
as disconjugate movement as the eyeballs work in opposite directions. Slow to occur (can be up to a second) and stops if focus on object terminated
what are 3 near objects (near-reflex) train of movement ?
1.Convergence of the eyes (move inwards)
2.Accommodation reflex to fatten lens
3.Pupillary constriction to focus more light on fovea
what are the 3 distant objects for vergence movement?
Divergence of the eyes (move outwards)
Relaxation of the ciliary muscle to stretch lens
Pupil dilation allowing optimal light reflection from object
what is olfaction?
utilises chemoreceptors located in the olfactory epithelium to detect chemical odourants
what is primary modalities each odour made up for in olfaction?
1.Putrid
2.Pungent
3.Floral
4.Fruity
5.Aromatic
6. Sweaty
7.Musk
what are the 3 steps in olfaction?
1.Air is channelled by concha to the olfactory mucosa.
2.Odourants dissolve in mucus to bind to receptors on the cilia of receptor cells.
3.Depolarise the receptor cells activation an action potential.
what is the scent linked to?
general sensation from CNV (trigeminal).
what do noxious odours stimulate?
stimulate pain receptors rather than olfactory!