eye+ear
Light rays are refracted when:
(1) They pass between two media of different densities (2) These media meet at a curved surface
production of aqueous humor
-It is continuously produced by the ciliary processes. ----The circulation of aqueous humor provides nutrients and oxygen to both the avascular cornea and the lens
Age-related macular disease (AMD)
-also known as macular degeneration -In AMD, abnormalities occur in the region of the macula lutea, which is ordinarily the area of most acute vision
Before light can reach the photoreceptor cells, it must pass from the air through the
1.Cornea 2.Aqueous humor 3.Lens 4.Vitreous humor 5.Cells forming the inner layers of the retina
Angle-closure glaucoma
1.a direct consequence of the narrowing of this angle consists about one-third of all cases of glaucoma
Open-angle glaucoma accounts
1.for about two-thirds of glaucoma cases. In the drain angles are adequate but fluid transport out of the anterior chamber is impaired
Congenital glaucoma
1.occurs only rarely and is due to hereditary factors or intrauterine infection
The relative tension in the suspensory ligaments is altered by
1.relaxation and contraction of the ciliary muscles in the ciliary body
pupil dilation
Dilator pupillae sympathetic
The eye is spherical, measuring about
The eye is about 2.5 cm
characteristics of rods
They function well in dim light. There are more than 100 million rod cells per eye.
The lens is
a transparent, biconvex structure, composed of precisely arranged layers of cells that have lost their organelles and are filled completely by a protein called crystallin.
Retina (inner layer)
a)Pigmental layer b)Neural layer
sphincter pupillae muscle
a)is arranged in concentric circles around the pupil. This muscle contracts when stimulated by parasympathetic division through the oculomotor nerve (CN III).
Which cavity of the eyeball is divided into an anterior and posterior chamber
anterior cavitity
What type of fluid is found in the anterior cavity of the eyeball
aqueous humor
The most visible part of the external ear is called the
auricle or pinna
Gustatory cells are
chemoreceptors
What is the largest structure of the vascular tunic
choroid
What structure is filled with pigment from melanocytes
choroid
Which structure of the eye absorbs light to prevent it from scattering within the eye
choroid
Vascular tunic (middle layer)
choroid, ciliary body, iris
The iris is continuous with the
ciliary body
suspensory ligaments attach the lens to
ciliary muscle
Sensory receptors
components of the nervous system that provide us with information about our external and internal environments.
What type of photoreceptors detects color
cones
As we adjust to low light, our ______ becomes nonfunctional and it may take ______ for rhodopsin to become regenerated sufficiently so that you can see well in low-light conditions.
cones; 20-30 minutes
Closer objects less than 20 feet, the ciliary muscles
contract
transducers
convert stimulus energy into electrical energy
The limbus is the junction between
cornea and sclera
When you go from a bright light environment to a dark environment, you have a slow sensitivity to low light levels. This is called
dark adaption
lens shape determines
degree of light refraction
Light rays are refracted or bent when they pass through two media of different
densities
Cutaneous receptors are a type of
exteroceptors
The external layer of the eye wall is the
fibrous tunic
The eyeball contains two tunics
fibrous tunic and vascular tunic
the center of the macula lutea is the
fovea centralis
the portion of the retina that is predominantly composed of cones and provides the sharpest vision
fovea centralis
Where do the fibers of the optic nerve come from?
from the axons of the ganglion cells
Where are photoreceptors located
in the neural layer of the retina
When the photoreceptors stop _____________ the bipolar cells, the bipolar cells can then release their neurotransmitter that binds to receptors on the ganglion cells.
inhibiting
The segment of the photoreceptors that connects directly to the cell body is the
inner segment
The segment of each photoreceptor that contains organelles for the cell such as mitochondria is the
inner segment.
The retina is the ______ layer of the eye wall.
internal
The most anterior region of the vascular tunic is the
iris
What structure is the dividing line between the anterior and posterior chambers
iris
vitreous humor
is a transparent, gelatinous fluid that completely fills the posterior cavity.
Aqueous humor
is a transparent, watery fluid that circulates within the anterior cavity.
The sclera
is made of dense connective tissue provides for eye shape
Dilator pupillae muscle
is organized in a radial pattern through the iris. This muscle contracts when stimulated by the sympathetic division.
the posterior and anterior cavities are separated by the
lens
The posterior cavity
lies behind the lens, contains a permanent fluid called vitreous humor.
The process by which your eyes adjust from low light to bright light conditions is
light adaption
The exact center of the retina is the
macula lutea.
Tactile receptors are a type of
mechanoreceptor
The optic (II) nerve is also visible located
medially from the fovea centralis
The optic disc contains ______ photoreceptors
no
The optic disc contains ______ photoreceptors.
no
Referred pain
occurs when impulses from an organ are perceived as originating from the skin
A lack of photoreceptors in this structure creates the "blind spot"
optic disc
The point at which the optic nerve exits the eye is the
optic disc (blind spot)
The fat surrounding the eye is called
orbital fat
The segment of each photoreceptor that is composed of hundreds of discs containing photopigments that are capable of absorbing light energy is the
outer segment
The sphincter pupillae is controlled by the ______ division of the nervous system
parasympathetic
If stimulated over a period of time receptors eventually lose sensitivity
phasic
What type of receptor can undergo adaptation
phasic
In phototransduction, the ____________ responds to light stimulation by changing its resting membrane potential, resulting in a change in the neurotransmitter it releases.
photoreceptor
The process by which photoreceptors become activated when the photopigments are altered by light entering the eye is
phototransduction
Each type of photoreceptor has an outer segment that extends into the
pigmented layer of the retina.
The retina lines the
posterior 3/4 of inner layer of eyeball
The iris controls the size of the
pupil
aqueous humor moves from the posterior chamber through the
pupil and to the anterior chamber
Which events occur during bright light adaptation
pupils constrict cones gradually adjust rods become inactive
The apparent distortion of the spoon in the water glass is due to the phenomenon called
refraction
When we view objects greater than 20 feet away, the ciliary muscles
relax
The most internal layer of the eye wall is the
retina
What structure makes up the posterior 5/6 of the fibrous tunic
sclera
Which part of the eye is an attachment site for extrinsic eye muscles
sclera
fibrous tunic (outer layer)
sclera and cornea
excess aqueous humor is reabsorbed into the
scleral venous sinus
Receptors for general senses are usually
simple in structure
pupil constriction
sphincter pupillae parasympathetic
The general function of all sensory receptors is to detect and respond to a
stimulus
Optic tracts extend to which structures after they leave the optic chiasm
superior colliculi the lateral geniculate nucleus of the thalamus
The lens is held in place by the
suspensory ligaments
Mechanoreceptors located in the skin and mucous membranes are called
tactile receptors
the vascular tunic is composed of
the choroid, ciliary body (both the ciliary processes and ciliary muscle), and iris.
The process is called accommodation and is controlled by
the parasympathetic within the oculomotor nerve (CN III).
the retina is composed of
the pigmented layer and neural layer (the layer containing the visual receptors)
The interior of the eye consists of two fluid-filled cavities
the posterior cavity and the anterior cavity
the fibrous tunic is composed of
the sclera and the cornea
when ciliary muscles contract
the tension on the suspensory ligaments decreases and the lens can become more spherical.
when ciliary muscle relaxes
the tension on the suspensory ligaments increases and causes the lens to flatten
The primary purpose of the eyebrows is
to keep sweat out of the eyes.
The suspensory ligaments attach to the lens capsule at its periphery, where they
transmit tension that enables the lens to change shape
characteristics of the cornea
transparent and avascular
The vascular tunic of the eye is also called the
uvea
The middle tunic of the eye wall is the
vascular tunic
An ophthalmoscope is used to
view the retina through the pupil.