Physiology Flashcards
what is the purpose of the cornea in the eye?
focusing power of the eye.
what is the purpose of the iris in the eye?
controls the diameter and size of the pupil.
its the eye colour.
what is the purpose of the lens in the eye?
aids focusing of the eye onto the retina.
what is the curvature of the lens of the eye control by?
cilliary muscles and zonule fibres.
what is the purpose of the aqueous humor in the eye?
maintains intracular pressure, nourishes and removes debris.
what is the scera in the eye?
connective tissue layer
what is the purpose of the the choroid in the eye?
nourishes outer 1/3 of the retina.
what is the retina layer in the eye?
light sensing layer
what does the vitreous humor/bodys purpose in the eye?
provides structure to the eyeball.
in which layer would you find the photoreceptors?
in the bottom layer - closest to the back of the eye.
what are the 2 types of photoreceptors?
cones and rods.
why does absorption of light occurin the outer segments of the photoreceptor?
as it contains stack of membranous discs which contain the light sensitive photopigment.
what do photoreceptors transduce light energy into?
changes in membrane potential.
what cells connect the photoreceptors to the ganlion cells in the eye?
bipolar cells.
what is the function of amacrine cells in the eye?
control and modulate the majority of imputs to the retinal ganglion cells and their responses,
where are amacrine cells located in the eye?
between the connection between the gangion cells and the bipolar cells.
what is the purpose of the bipolar cells in the eye?
create direct pathway from photoreceptor to gangion cells.
what is the function of horizontal cells in the eye?
feed info laterally in the outer plexi for layer to influence neighbouring cells.
where are horizontal cells in the eye found?
between the connects of where the bipolar and photoreceptors meet.
what is the function of muller cells?
they ensheath all retinal neurons and contribute in mediating their functions and stability
where are muller cells in the eye found?
located in the neuronal retina and span its entire depth.
why is the fovea (in the eye) dipper?
so all light can go straight to the photoreceptors.
what are the only types of photoreceptors in the fovea?
only has cones.
what causes the blind spot in our vision?
it is where the optic never is so there are no photoreceptors.
what is the pigment in rods called?
rhodopsin
what are the 3 types of opsin in cones that allows us to detect colour?
- red
- green
- blue.
how is colour perception determined by the cone photoreceptors?
is determined by the relative contribution of blue, green and red cones to the retinal signal.
what is achromatopsia?
total colour blindness.
what causes achromatopsia?
genetic mutation where they individual have no cones.
what is dichromacy?
a form of colour blindness where 1/3 of the basic colour mechanisms not functioning.
what is the phototransduction pathway?
process where light is converted into electrical signals into the rod and cone cells.
Rods or Cones:
low sensitivity to light?
Cones (ideal for day vision)
Rods or Cones:
have the most photopigment?
Rods (as they need to capture more light)
Rods or Cones:
have higher amplification?
Rods
Rods or Cones:
Higher temporal resolution?
Cones (fast response)
Rods or Cones:
more sensitive to scattered light?
rods
Rods or Cones:
more sensitive to direct light?
cones
How are photoreceptors set up?
in fields - where some turn on and some turn off.
How is the visual pathway carried out?
- retina
- optic nerve
- optic chiasm
- optic tracts
- lateral geniculate nuclei
- optic radiations and the visual coretx in the occipital lobe.
where is visual motion processed in the brain?
striate cortex towards the parietal lobe.
where is the recognition of objects processed in the brain?
striate cortex towards the temporal lobe.
what are the parts of the outer ear?
- Pinna
- Auditory canal
what is the purpose of the pinna in the ear?
funnel to collect sound waves/ aid in determining sound location.
what is the function of the auditory canal in the ear?
focuses sound waves- increasing pressure on the tympanic membrane.
where does the middle ear start and finish?
starts at the tympanic membrane and ends at the oval window.
what are the names of the 3 ossicles in the middle ear?
- malleus (the hammer)
- incus (the anvil)
- stapes (the stirrup)
what is the purpose of the middle ear?
- to convert waves to fluid.
- increasing the size of vibrations.
- stop of loosing signals.
what does the attenuation reflex aid us in preventing?
ear damage - way for the ear to protect its self from loud noises.
how does the attenuation reflex aid in preventing ear damage?
the tensor tympani and stapedius muscles contract - pulling tthe malleus inwards and the stapes outwards. Causing the ossicular system to become more ridged and decrease in ability to conduct sound.
what is one problem with the attenuation reflex?
there is a delay in the response of 40-80ms. So damage can be caused in this time.
what is the name of the tube that connects the middle ear to the nasopharynx?
Eustachian tube.
what is the purpose of the Eustachian tube?
to equilibriate air pressure in middle ear to pressure in atmosphere.
what happens if there is a difference in pressure in the middle ear and the atmosphere?
- decreased motion of tympanic membrane so decrease in hearing.
what structures of the inner ear?
- Cochlea
- 3 semicircular canals
what is the function of the cochlea in the ear?
auditory component of the inner ear.
what is the function of the 3 semicircular canals in the eaR?
they are the balance component of the inner ear.
is the basila membrane wider at the start of the cochlea or towards the apex?
at the apex.
what is important to know about the basilar membrane?
different frequency sound waves travel different distances along it - high frequency a the base and low frequency at the apex.
what type of hair cells make the majority of hearing?
inner hair cells.
what is the importance of the hair cells?
they convert mechanical energy into changes in memebrane potential.
how does a sound wave get to the brain?
- sounds waves cause the basilar membrane to vibrate
- causing hair cells to push against the tectorial membrane.
- causing cillia on the hair cells to bend
- this activates signals to be sent to the brain.
what is the purpose of the outer hair cells?
the modulate the response of the inner hair cells.
what is damage to hearing normal caused by inside the ear?
due to damage to the hairs that connect the cell to the membrane.
how are the hair cells linked together?
via elastic filaments.
how are the hair cells depolarized?
- potassium gates channels open
- after polarisation in the cell, calcium channels open.
- this activates the release of vesicles filled with excitatory neurotransmitter.
- This starts an action potential.
what fluid are the hairs of the hair cells in?
endolymph
what fluid are the hair cells body in?
perilymph
what are the steps of the ascending auditory pathway?
- cochlea
- cochlear nucleus
- left superior olive/ right superior olive (in the pons)
- inferior colliculus
- medical geniculate nucleus (thalamus)
- auditory cortex.
what happens to the tonotopic possition from the basilar membrane during the auditory pathway?
it is maintained all the way up to the auditory cortex.
