Ch#17 Flashcards
what includes in fibrous layer of eye
cornea
sclera
key things about cornea
- Clear – avascular
- Collagen covered by stratified squamous
epithelium - Significant role in refraction (bending) of
light
why cornea requires transplant and not repair
it is avascular
key things related to sclera
- “white” of the eye
- Protects and shapes eye
- Attachment extrinsic eye muscles
- mainly composed of collagen and elastic fibers
why people have stigmatism
if their cornea is curved.
Second also called as vascular layer composed of
- Iris
- Ciliary body
- Choroid
define iris
iris controls the diameter of
the pupil
ciliary body
- it holds the lens in
- place controls lens shape,
- Produces aqueous
humor - release the tension from muscle to lens.
choroid
it contains blood
vessels and melanocytes
Structure of Iris
Iris has two types of muscles
- Sphincters pupillae
- Dilator pupillae
Sphincters Papillae
they form series of concentric circles around the pupil. When they contracts, the pupil constricts => diameter decrease
- it is activated during Parasympathetic system.
Dilator pupillae
It extends radially from the pupil edge. when these muscles contract, the pupil dilates => increase diameter.
what are the parts of eye cilicary body.
- cilairy muscle
- ciliary processes
- ciliary zonules =. suspensory ligaments
how the lense shape effect the light focus
- Muscles relaxed = flatter lens
- Muscles contracted = bulging/rounder lens
we talking about ciliary muscle
How aqueous humor made?
this forms by the filtration from the capillaries in the ciliary process.
flow of aqueous humor
it flows from the posterior chamber through the pupil into the anterior chamber. some also flows through the vitreous humor.
what are the important to know about vitreous humar
it is continuously remade and reabsorbed into the venous blood by scleral venous sinus.
Explan about vitrous humor
- vitreous humor is gel-like, forms during embryonic development, and is not replaced.
- Transmitting light
- Supporting the lens and retina
- Counteracting pulling forces
exerted by extrinsic eye muscles
Innermost layer of eye
- Retina
- Neural layer
- Pigmented layer
Specialty of photoreceptors
Rods and cones cells keep getting replaced. the older ones are phagocytosed and accumulated Vitamin A to make new cells.
what is pathway of flow of light in the eye musle
Light travels: cornea → aqueous humor → lens → vitreous humor → neural layer of
retina → reaches outer segments of rods and cones embedded in pigmented layer
How refraction happens
Cornea shape and size stay constant but it refracted the light as it enters. the shape of lense keep of changing to focus the object properly
how lens adjust for shortened focal distance
Far object → short focal distance → need to lengthen (increase) the focal distance to get
the light to strike the retina properly
explain Myopia
Eye too deep or lens curvature too great
(myopia):
* For near objects, the focal distance does not
need to be shortened as much → can see near
objects well
* For far objects, need to increase focal distance even further → limitation to how much can flatten the lens → far objects appear blurry
Solution of problem is using concave (diverging lens)
hyperopia
Eye too shallow or lens too flat (hyperopia):
* For near objects, the focal distance needs to be shortened even further → limitation to how
much lenses can bulge → near objects appear
blurry
* For far objects, do not need to increase focal
distance as much → far objects appear clearer
The solution of the problem is to use the convex lens (converging lens)
what are the special senses?
- Olfaction
- Gustation
- Vision
- Hearing
- Equilibrium
Define gustation and olfaction
Dissolved chemical stimuli in saliva and mucous detected by the chemoreceptors associated with specialized epithelium
Define vision
Light detected by the photoreceptors (rods and cones) located on the retina back of the eye.
Define Hearing and Equilibrium
Hairs cells within specialized structures in the inner ear detect mechanical stimuli
where are the olfactory receptors are located?
Olfactory organs are located in the
superior portion of the nasal cavity
on each side of nasal septum. layer name name is Lamina Propria
pathway of the olfactory to the cerebrum
Olfactory epithelium => Olfactory nerve fiber => olfactory bulb => olfactory tract => central nervous system
How stimuli get detected by the olfactory nerve fibers
Odorants must be dissolved to bind receptor proteins on dendrites → binding leads to receptor
potential → if get sufficient depolarization, get an action potential
at kind of neurons are olfactory
they are bipolar sensory neurons with two extensions and cell body.
how does olfaction transmission determine the order?
Axons from neurons with the same kind of receptor converge, which means from different locations come to one place.
But the pattern of which the neurons activated determine the odor.
define gustation specific about organs and receptors involve.
Gustation sense taste with the help of taste buds found in the lingual papillae, larynx and pharynx.
many papillae are there on the tongue and which once have taste buds.
Tongue has lingual papillae of four types.
taste buds are located in the pockets of the epithelium fungiform, vallate, and follate. filliform do not have buds but can sense frictionand abrasiveness of moving food.
define structure of taste buds
- taste hairs are bathed in salva, then detect stimuli
- in vallate papillae we have transitional cell, gustatory epithelial cells and basal epithelial cell.
- Gustatory epithelial cells are
associated with the dendrites (Taste hairs)
of sensory neurons
the receptor of senses like taste, hearing, equilibrium, and vision cells have unexcitable membrane. they form synapses with the processes of sensory neuron.
-Membrane => graded depolarization => neuroransmiter release => sensory neuron depolarizes => create generator potential => action potential => CNS
what are the taste sensation
-Sweet => organic (carbon-based) sugar, amino acids, alcohols
-Salty > metal based (Na+, Iron)
- bitter => alkaloids (food spoilage, poison)
-Sour => aid based more H= concentration, citrus fruits
- Umami => Glutamate and asparatete (amino acid)
Relations between special senses
- Olfactory information contributes to
our perception of taste - Other stimuli we perceive related to
our food (temperature, texture,
spiciness) are associated with the
general sensory receptors
whichcranial nerves involve with the gustatory relay pathway
- Involves cranial nerves:
- facial (VII),
- glossopharyngeal (IX)
- vagus (X)
which brain parts receive info about gustation
Relay information to cerebral cortex,
hypothalamus, and other limbic system structures
why we do vomiting
Medulla is the center to initiate the digestive reflexes, which are also called as protective reflexes.