Senses! Flashcards
Name the types of chemoreceptors
Olfactory neurons, gustatory cells, other
Describe general, mechanism of senses
1) Stimulus opens Channels (directly: Ligand gated or mech gated or indirectly: enzymatic pathway)
2) depolarization (more positive) produces graded potential which is converted into AP for relaying
3) Projection where AP passes through specific neutron pathways to area of cortex
4) Brain decodes- type of stimulus, location of stimulus and strength
What are tonic receptors
Always on, slow or no adaptation: Muscle receptors for pain and balance
What are phasic receptors
adapt, fire @ beginning and end of stimulus. Eg. Meisner corpuscle or hearing
What does the utricle detect
horizontal movement (acceleration)
what does the saccule detect
vertical movement (jumping, elevator)
Semicircular ducts
detect changes in rate of rotation
When the stereocillia bend toward the kinocillium causes…
depolarization
when the stereocillia bend away from the kinocillium causes…
hyper polarization
where are hair cells for balance found
In the semicircular ducts, embedded in the ampulla where a cupola sways when the endolymph moves
How is hearing similar to balance
- Both have hair cells
- both happen in ear
- both have hair cells in endolymph
- both use vestibulocochlear nerve
Difference between balance and hearing
Location of receptor: Scala media & semicircular ducts.
Structure of receptor: Balance has a kino cilliim
Mechanism: Fluid waves in scala vestiboli cause waves in the scala media, where the hair cell will brush against the tectorial plate and depolarize as mechanical gated K+ channels are opened.
where as balance: when head moves, sterocilia will bend toward the kinocillium which will open K+ ch causing depolarization or hyperpolarazation. Synapse with the afferent neutron and vestibulocochlear nerve
Explain what is happening in distance vision.
What the Lens and cornea are doing:
The lens is flat (think flat, far away) it reflects light
the cornea does not change shape
Explain what is happening in distance vision.
what neurons are involved?
Sympathetic neurons
Explain what is happening in distance vision.
What are the cilliary muscles doing?
they are relaxed/dilated
Explain what is happening in distance vision.
what are the suspensory ligaments doing?
pulled taut
Explain what is happening in distance vision.
What is the binocular vision doing?
Parallel rays can land on fovea when yes are forward.
Explain what is happening in distance vision.
What are the pupils doing?
Dilated. (large)
Pupillary dilator muscles contract and constrictor muscles relax, pulled open
Explain what is happening in close vision.
What is the lens doing
accommodates to become round.
Reading & relaxed = round
Explain what is happening in close vision.
What are the neurons involved
Parasympathetic
Explain what is happening in close vision.
What are the ciliary muscles doing
Contracted
Explain what is happening in close vision.
What are the suspensory ligaments doing
loose relaxed
Explain what is happening in close vision.
what are the binocular vision doing
Requires convergence, extrinsic eye muscles rotate medially so divergent rays land on fovea
Explain what is happening in close vision.
What are the pupils doing
Constricted.
Explain what is happening in close vision.
What are the pupillary constrictor and dilator muscles doing
Parasympathetic system stimulates pupillary constrictor muscles to reduce light entering the periphery. The dilator muscles relax and the constrictor muscles constrict.
Explain what happens at the photoreceptor in the retina in total darkness
Photopigment is inactivated. cGMP molecules bind to Na+ Channels, Na+ continually enters. Cell is depolarized. Ca2+ enters synaptic knob. Inhibitory NT are released continuously.
Explain what happens to the bipolar cell in total darkness
Bipolar cell is inhibited and hyper polarized.. doesn’t release NT.
Explain what happens to the ganglion cell in total darkness.
Not stimulated, no AP to brain.
Explain what happens to the Photoreceptor in dim light.
The light turns Cis-retinal to trans retinal. Bleaching occurs because the opsin and trans retinal separate (photopigment needs to be regenerated). Transretinal activated enzymes which degrade cGMP. w/ fewer cGMP, some Na+ channels close, so fewer Na+ enter. Na+ pumps will continue to remove Na+ causing hyper polarization, fewer v. gated calcium ch. open. Less enter synaptic knob so fewer inhibitory NT are released.
Explain what happens to bipolar cell in dim light.
Bipolar cell is less inhibited. Cell can build up positive ions. Depolarizes, releases excitatory NT.
What happens in dim light at ganglion cell.
NT bind to ganglion cell, open Na+ ch. Depolarization occurs, AP to brain.
What happens at photoreceptor during bright light.
More trans retinal. More enzymes and even less cGMP. More Na+ close. More hyper polarized. little/ no inhibitory NT released bc no Calcium let in to trigger it.
What happens to bipolar cell in bright light
Bigger EPSP. more NT released
what happens to ganglion cell in bright light.
increased frequency of AP to the brain.
Why can’t we see details at night
Many rods converge to one single ganglion cell, fewer neurones = less detail. We can’t tell where the individual rods were stimulated. 100s of rods pick up dim light bc of spatial summation.
Why is night vision clearest in periphery
More rods in periphery, none in fovea.
