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.
Where eye ball is located and what help maintain its shape!
Eyeball is located within the orbit
- extrinsic eye muscles help maintain the shape of eye ball and hold it in place
What to call the fluid in eye
It is vitreous humor is the thick fluid filled in posterior compartment
What are the accessory structures of eye
- eye brows
- eye lashes
- eyelids (palpebra)
- Lacrimal caruncle
- Tarsal glands
Eyebrows
• Eyebrows shade and keep perspiration from reaching the eye
Eyelids protection
“Palpebra”
• Reflexive blinking of eyelids helps prote the eye from debris, spread secretions oil, mucus, saline) across eye
Eyelashes
lash hairs are associated with lots of
• nerve endings, reflexive blinking
Lacrimal caruncle
Lacrimal caruncle contains sebaceous a sweat glands
Which of the following is incorrectly matched?
ciliary body: site of extrinsic eye muscle attachment
Which of the following is correctly matched?
anterior chamber: between the cornea and the iris
posterior chamber: between the iris and the lens
sclera: covers most of the ocular surface
retina: consists of a pigmented layer and a neural layer
Tarsal glands
• Tarsal glands are modified sebaceous glands with ducts that open at the eyelid edge
oil film - prevents water loss
Conjunctiva
- Begins where cornea ends
Palpebral conjunctiva
Eyelash
Bulbar conjunctiva
Which of the following is a function of the pigmented layer of the retina?
absorb light passing through the neural layer
How information is relayed helps explain the differences in acuity between rods and cones
- 1 cone to 1 bipolar cell to 1
ganglion cell - Rods – multiple rods to one
bipolar cell, sometimes multiple
bipolar cells to 1 ganglion cell - Amacrine and horizontal cells
serve neuromodulatory roles
What part of the ear is most impotant for the hearing and equilibrium
Inner ear
Inner ear structures
Cochlea -it has perilymph surround by bony labyrinth & endolymph surround by membraneous labyrinth
Vestibule - it has mechanoreceptors
Semicircular canals
Conduction of sound wave to the cochlea
- Sound waves arrive at the tympanic membrane.
- movement of the tympanic membrane displaces the auditory ossicles.
- movement of the stapes at the oval window produces pressure waves in the perilymph of the scala vestibuli.
What is the purpose of these
muscles of the middle ear?
- Tensor tympani stiffens the tympanic membrane
- Stapedius reduces the movement of the stapes
what does cochlear duct contain?
- Endolymph
- Spiral organ of Corti (where
mechanoreceptors found, located on top
of basilar membrane)
Define pitch and loudness
Location of maximal distortion = Pitch
Frequency of the action potential = loudness
wave transduction inside the cochlea
- Waves distort the basilar on their way to the round window of the scala tympani
- basilar vibration cause IHC to vibrate against the tectorial.
- info about the region and intensity relayed ti the CNS over the cochlear nerve.
Where the basilar membrane vibrates?
It depends on the sound frequency.
* Basilar membrane is stiffest at its
base
* Hight frequency sounds vibrate it
near the base, low frequency
sounds towards the end
Where do you find hair cells within the vestibular complex?
Hair cells associated with semicircular canals are found in expanded areas called ampullae
Role of otolith membrane
- In maculae, hairs are embedded in otolith membranes Otoliths increase membrane’s weight and inertia
- With linear or vertical acceleration, otoliths lag due to inertia
- Distinguishing tilt from linear acceleration often involves visual inputs
The purpose of the intrinsically photosensitive retinal ganglion cell (ipRGC) photoreceptors are
influence the circadian rhythm.
Injury to the neurons of a collateral ganglion would affect the function of the
digestive tract.
If the receptor on the postsynaptic membrane binds to norepinephrine, the synapse is called
adrenergic.
Drugs that have effects similar to those of sympathetic activation are called sympathomimetic drugs. Which of the following would you not expect to observe in a person who has taken a sympathomimetic drug?
decreased blood pressure
When reviewing the general functions of the parasympathetic division, which of the following statements best summarizes the physiologic outcome?
The parasympathetic division works at counterbalancing the sympathetic division by conserving energy and lowering metabolic rate.
Parasympathetic effects are localized and short-lived because
acetylcholine is inactivated at the synapse by acetylcholinesterase.
Parasympathetic blocking agents can be useful in treating
urinary incontinence.
In general, autonomic tone of peripheral blood vessels increases when
sympathetic stimulation is increased.
Autonomic tone is an important aspect of ANS function because it
allows ANS neurons to increase or decrease their activity, providing a range of control options.
During ________ sleep, dreaming occurs.
REM
The conscious state is maintained by the
reticular activating system.
Most long-term memories are stored in the
cerebral cortex.
Which of the following is essential for memory consolidation?
hippocampus
The olfactory organ consists of the ________ and the lamina propria.
olfactory epithelium
The olfactory receptors are highly modified
sensory neurons
Olfactory sensory neurons are short-lived and, therefore, replaced frequently. How does this turnover happen?
mitotic division and differentiation of basal epithelial cells
The first step in the olfactory process is __________
when an odorant dissolves in the olfactory mucus fluid
Some neural tissues retain stem cells and thus the capacity to divide and replace lost neurons. Which of these special senses can replace its damaged neural receptors?
olfaction
The taste sensation that is triggered by the amino acid glutamate is known as
umami.
All of the following are true of the neural layer of the eye
- contains bipolar cells.
- contains the photoreceptor cells.
- is the innermost layer of the eyeball.
- contains ganglion cells.
Tears pass through which of the following structures before emptying into the nasal cavity?
nasolacrimal duct
All of the following are true of the fibrous layer of the eye
consists of the sclera and cornea.
is where extrinsic eye muscles insert provides mechanical support and some protection for the eye contributes substantial focusing power.
The human lens focuses light on the photoreceptor cells by
changing shape.
Which of the following produces a lipid-rich secretion that prevents the upper and lower eyelids from sticking together at their edges?
tarsal gland
The shape of the lens is controlled by the
ciliary muscles.
Pupillary muscle groups are controlled by the ANS. Parasympathetic activation causes pupillary ________, and sympathetic activation causes ________.
constriction and dilation
What structure regulates the amount of light that passes to the photoreceptors of the eye?
iris
The optic disc is a blind spot because
there are no photoreceptors in that area.
Amacrine and ________ cells facilitate or inhibit communication between photoreceptors and ganglion cells.
horizontal
Which of these functions does the vascular layer serve?
It supports blood vessels and lymphatics.
It controls the shape of the lens.
It regulates the amount of light that enters the eye.
The first step in the process of photoreception is
absorption of a photon by a visual pigment.
A period of adjustment is required when moving from a dark room into bright light because
rods exposed to strong light need time to regenerate rhodopsin.
The vitreous body
helps to stabilize the eye and holds the retina up against the eyewall.
The transparent portion of the fibrous layer is the
cornea
An area of the retina that contains only cones and is the site of sharpest vision is the
fovea.
Which of the following is not true regarding image formation?
To view a distant object the lens will become rounder.
As light passes through the cornea and lens, it is directed onto the __________, a region of the retina that contains only __________.
macula, cones
Which of the following is NOT a property of the palpebrae?
They comprise the eyebrows.
Light refraction takes place at the
cornea and lens.
The ability of the lens to change shape in order to correctly focus an image on the retina is called __________.
accommodation
__________ provide information about __________, giving us the perception of color.
Cones, the wavelength of arriving photons
Visual information travels from the retina along the optic nerve to the lateral geniculate nucleus. Visual information can then travel to which of the following structures?
visual cortex of the occipital lobes
superior colliculi of the midbrain
suprachiasmatic nuclei of the hypothalamus
The receptors responsible for auditory sensations are located in a structure called the __________.
spiral organ
