Vert ch 10
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Vert ch 10
Vert Physiology chapter 10
What are the modalities of sense? How are they sensed?
light, taste, touch, pressure, etc
What do sensory receptors do?
transduce sensation into impulses to be transmitted to sensory nerves
what do sensory nerves do?
transmit impulses to the CNS for processing and appropriate response
How are sensory receptors classified?
according to the type of sensation they transduce & according to the type of sensory info delivered to the brain
List the 5 types of sensory receptors based on type of sensation
what do chemoreceptors do?
sense chemical stimuli in the environment of the blood
what do photoreceptors do?
sense light sensation for vision
what do thermoreceptors do?
sense heat and cold
what do mechanoreceptors do?
sense mechanical deformation due to pressure or touch
what do nocireceptors do?
List the 2 types of sensory receptors based on the type of sensory info sent to the CNS
what do proprioreceptors do?
sense body position and allow for fine motor activity
what do cutaneous receptors do?
include sensation for touch, pressure, heat, cold and pain
what do special senses mediate?
sight, hearing and equilibrium
How do phasic receptors work?
respond to stimuli with a burst of of activity then quickly adapt by decreasing their firing rate
what is sensory adaptation
ability of phasic receptors to adapt to stimuli
what are tonic receptors?
receptors that maintain their firing rate in response to stimuli (ex: pain)
what are some physical examples of sensory receptors?
free nerve endings, pacinian corpuscle, and Meissner's corpuscle
what happens when sensory receptors are stimulated?
they are depolarized generating a change in the membrane potential called receptor potential or generator potential thus stimulating an action potential in the receptor
how are cutaneous receptors mediated?
by dendritic nerve endings of different nerves
how is info transmitted from proprioreceptors and pressure receptors?
proprioreceptors--> spinal cord--> medulla oblongata--> (via lateral leminiscus) thalamus--> postcentral gyrus
what do the eyes do?
transduce light energy into nerve impulses for vision
what is the sclera?
outermost layer of the eye, connective tissue seen externally as the white of the eye
what is the cornea?
continuation of the sclera
how does light pass through the eye?
through the cornea into the anterior chamber of the eye then through the pupil
what is the iris?
the smooth muscle that surrounds the pupil
where does light go after passing through the pupil?
to the lens
what does the iris do?
increase or decrease diameter of the pupil by constricting (miosis)
how does miosis take place?
parasympathetic nerve stimulates circular muscle of the iris
what is mydriasis?
how does it take place?
dilation of the pupil
sympathetic nerve stimulates radial muscle of the iris
How is the lens of the eye suspended?
from a muscular process (ciliary body) by the suspensory ligament
what is the space between the iris and the ciliary body?
what is the space between the cornea and the iris?
what fills the anterior and posterior chambers?
aqueous humor secreted by ciliary body
what is the purpose for aqueous humor in the anterior chamber?
provides nutrition for avascular lens and cornea
what is the canal of schlemm?
where aqueous humor drains to from the anterior chamber
what does the canal of schlemm do with aqueous humor?
returns it to veinous blood
What happens when aqueous humor is drained inadequately?
What is this condition called?
accessive accumulation of the fluid leading to increase in intraocular pressure
what is the danger of glaucoma?
damage retina and cause loss of vision
what is vitreous humor?
thick viscous fluid located in the part of the eye behind the lens
where does the light go from the lens?
to the retina
what is the retina?
neutral part of the eye
what absorbs light in the retina?
what happens when light reaches the retina?
stimulates photoreceptors which activate retinal neurons
what are the photoreceptors in the retina?
cones and rods
what do the neurons in the retina do?
contribute fibers that are gathered together exiting the eye at the optic disc as the optic nerve
what happens when normal eyes view an object?
parallel light rays are refracted by the lens to the focus which is located on the retina
what is accomidation?
ability of the eyes to keep the retina focused on an object as it moves closer to the eye
how does accomidation occur?
contraction of ciliary muscle causes the lens to be more rounded and convex resulting in near vision
how does far vision occur?
ciliary muscle relaxes causing the lens to b flatter and less convex so the eye can focus on objects further away
define visual activity
sharpness of the eyes (ability to distinguish closely placed dots)
how is 20/20 vision confirmed?
if the person can stand 20 feet from a Snellen eye chart and read the line marked "20/20"
in nearsightedness (myopia) what is the problem with the eye?
the eye ball is too long and the image is focused in front of the retina
what is the problem with the eye in farsightedness (hyeropia)?
the eyeball is too short and the image is focused behind the retina
what causes astigmatism?
the curvature of the lens and the cornea are not perfectly symmetrical
which type of lense corrects myopia?
what type of lesne corrects hyeropia?
what type of lenses corrects astigmatism?
a cylindrical lens
what is emmetropia
what activates the photoreceptors (cones and rods) of the retina?
light reaching the retina. this causes a chemical change in the pigmented molecules of the photoreceptors
What is rhodopsin?
purple pigment in rods
What does rhodopsin do?
transmits light in the red and blue regions of the visible spectrum and absorbs light in the green region
what are the 2 components of rhodopsin?
retinaldehyde- derived from vitamin A
opsin- a protein
what is the bleaching reaction?
rhodopsin's reaction to light
what are rods primarily responsible for?
How do eyes adjust in dark rooms?
pupils dialate to absorb more light and photoreceptors, especially rods, increase their sensitivity to light
what is dark adaptation?
the eyes ability to adjust to when entering a dark room
What are cones responsible for?
color vision and greater acuity
explain the trichromatic theory of color vision?
color vision is the result of the 3 types of cones designated as blue, green or red according to which each type absorbs to allow for color vision
according to the trichromatic theory of color vision what protein is associated with the retinine of the cones?
what happens when viewing an object in daylight?
the image falls on the fovea centralis of the retina which contains only rods
how do the fibers of the optic nerve decussate?
1/2 to the contralateral side
1/2 to the ipsilateral side
where do optice nerve fibers travel after the optic chiasma?
up the optic tract to the superior colliculus
what happens in the superior colliculous?
visual reflexes are processed?
where do the optic nerve fibers in the optic tract synapse?
at the lateral geniculate nucleus with neurons that end in the occipital lobe
what are interoceptors?
chemoreceptors that respond to chemical changes in the internal environment
what are externoceptors?
chemoreceptors that respond to chemical changes in the extrernal environment
what mediates the sense of taste?
taste buds on the tongue
list the 4 modalities of taste
sweet sour bitter salty
which region of the tongue tastes sweet things?
tip of the tongue
what region of the tongue tastes sour things?
sides of the tongue
what region of the tongue tastes bitter things?
back of the tongue
what region of the tongue tastes salty things?
most of the tongue
what is the suggested 5th modality of taste?
taste for water found only in humans
what causes salty tastes?
presence of Na+ or other cations
what causes the taste of sour things?
presence of H+
How are sweet and bitter tastes produced?
interaction of taste molecules with specific membrane receptor proteins
what receptors are responsible for the sense of smell?
dendritic endings of sensory neurons located in the nasal cavity
whats different about olfactory neurons?
they replace themselves every 1-2 months
whats different about sensory receptors for smell?
they go directly to the cerebral cortex