Special Senses - Lecture 2 Flashcards
sensory signals are subject to extensive modification before they reach higher levels of the
Central nervous system
what part of the brain plays an important rile in the control of afferent information?
cortex
every cell in the CNS receives 10,000 to 40,000 synapses from other cells, some of them will be _______ and some of them will be _________
excitatory
inhibitory
how do inhibitory inputs affect the response of a projection neuron to a stimulus
turns down or lowers the response
T/F inhibition of painful stimulation can vary based on the situation. This is due to cortical control of sensory pathways
T
all info from periphery travels to the somatosensory cortex via a
projection neuron
the anterolateral system is a pathway that carries what information to where?
pain or hot/cold information to the somatosensory cortex
the dorsal column system is a pathway which carries what information to where?
fine touch mechanoreception to the somatosensory cortex
***see slides for mechanisms of anterolateral and dorsal systems
Both the anterolateral and dorsal column pathways end in the somatosensory cortex on the _______ side of the body
contralateral
which pathway crosses immediately and which one crosses at the level of the brainstem
anterolateral - immediately
dorsal column - brainstem
all sensory information goes from the ______ to the ____________
thalamus
somatosensory cortex
The smaller and more densely packed the sensory receptors are, the ______ the region in the somatosensory cortex that they will occupy
larger
photoreceptors in the eye are _____ at rest and _______ when activated
depolarized
hyperpolarized
the optical component (front part of the eye) is responsible for:
focusing the image on the receptor cells
the neural component (back part of the eye) is responsible for:
transforming image into a pattern of graded potentials and AP’s
the white part of the eye
sclera
attached to the sclera; responsible for eye movements such as looking up, down or side to side
extraocular muscle
where the sclera becomes clear at the very front; responsible for refracting light waves
cornea
hole that allows light to pass through into back of the eye
pupil
regulates the size of the pupil and the amount of light entering eyeball - colour of eye
iris
parasympathetic innervation causes pupils to __________ while sympathetic innervation causes pupils to ___________
constrict
dialate
is behind the iris and works the cornea to focus the image on the retina; shape and size can change
lens
light passes through it and refracts a certain amount
cornea
T/F the cornea is mobile and changes it’s shape
False - it is static and stays in place
attached to the lens and ciliary muscles
zonular fibers
contact/relax to change the shape of the lens
ciliary muscles
located behind the lens, against back of the eye and is where photoreceptors are found
retina
what are the two types of photoreceptors, when are they activated and what type of vision are they responsible for
Rods: low light conditions, monochromatic
Cones: more light present, colour vision
cells activated by rods and cones; take info to brain
retinal ganglion cells
leaves through the back of the eyeball towards the thalamus and cortex; made of axons and retinal ganglion cells
optical nerve
a gelatinous fluid that fills the space b/w the lens and cornea
aqueous humour
gelatinous fluid found behind lens
vitreous humor
light waves bend once they hit they
cornea
the cornea is primarily responsible for __________ and the ________ will change shape to focus the image on the ________ of the eye
refraction
lens
retina
when an object comes very close to the eyes, what does the ciliary muscle do to focus the image on the back of the retina
contracts, causing the lens to get fatter and shorter; increasing the amount of refraction
what is accommodation?
the process of using ciliary muscles in the lens in order to focus on objects that are very close
loss of elasticity of the lens resulting in the inability to accommodate for
near vision; due to the breakdown of the ciliary muscles; age-related
Presbyopia
what is myopia or nearsightedness?
when does it occur?
what lens corrects it?
- focus on objects up close but not far away
- occurs when the eyeball is too long and there is too much refraction; visual image is reconstructed at a point in front of the retina
- concave lens
what is hyperopia or farsightedness?
when does it occur?
what lens fixes it?
- see far but not close
- eyeball is too short; not enough refraction and visual image is reconstructed behind retina
- convex lens
what is astigmatism
oblong shape of the eyeball
glaucoma is
damage to the photoreceptors due to increased intraocular pressure
cataracts are
clouding of the lens and is age-related
what do bipolar cells do
take information from the photoreceptors and transfer to the retinal ganglion cells
what are disks
- little flaps or layers of membrane in the outer segment of cones
- site of actual processing of visual information
synaptic terminals of cones make contact with
bipolar cells
what enzyme converts GTP into cyclic GMP
guanylyl
when no light is present, photoreceptors are relatively
depolarized
**see document for phototransduction
the disk of the cones contains a _______ which contains a chromophore called _____
photopigment
retinal
when light hits the photopigment what happens to the retinal? what molecule does this activate?
- changes conformation
- cyclic GMP phosphodiesterase
cyclic GMP phosphodiesterase is an _____ which breaks down _____
enzyme
cGMP
the photoreceptor is relatively ______ when light is polarized
hyperpolarized
Activation of one single cone activates
two bipolar cells and two retinal ganglion cells
at all times the photoreceptor is giving information via the ________ cell that says:
retinal ganglion
yes light is hitting me or no it’s not
***see document for ON and OFF pathways
the OFF bipolar cell is ______ by glutamate and the ON bipolar cell is _______ by glutamate
activated
inhibited
ON bipolar cell is inhibited by ______ being present
glutamate
when light is present, the ON pathway is activated due
the release of inhibition on the ON bipolar cell by glutamate
