Lecture 10: Vision and Hearing

Light is a form of electromagnetic radiation composed of photons that travel in __________.

waves.

__________ is the distance between two wave peaks.

wavelength.

Wavelength represents __________ carried by the photon.

energy.

Amplitude represents the __________ of light.

intensity.

Visible light is only a __________ portion of the total electromagnetic spectrum.

small.

The eye is a spherical fluid filled structure enclosed by __________ layers.

three.

Three layers (tunics) enclosing the eye fluid:

sclera & cornea
choroid, ciliary body, & iris
retina

__________ is the white part of the eye.

sclera.

__________ is the transparent front part of the eye.

cornea.

__________ contains the blood vessels that nourish the retina.

choroid.

__________ is the muscle that regulates the amount of light entering the eye.

iris.

__________ __________ are the muscles that play a role in accommodation (focusing) in the eye.

ciliary body.

The __________ has an outer pigmented layer of the eye and an inner nervous tissue layer.

retina.

Two fluid filled cavities in the eye are separated by the __________.

lens.

Two fluid filled cavities of the eye:

aqueous humor
vitreous humor

The __________ humor of the eye is anterior.

aqueous.

The __________ humor of the eye contains the nutrients for the lens and corena.

aqueous.

The aqueous humor is produced by __________ __________.

ciliary body.

The __________ humor of the eye is posterior.

vitreous.

The __________ humor helps maintain the shape of the eyeball.

vitreous.

The __________ helps to focus light on the retina.

lens.

Focusing light on the retina involves bending light (__________) to focus on the light sensitive cells.

refraction.

The focusing of light on the retina primarily occurs at the __________.

cornea.

Every structure (and liquid) that light passes through the eye affects the __________ of light.

course.

The __________ is a transparent structure that focuses light onto the retina.

lens.

The __________ of the lens determines the degree of light refraction.

shape.

Lens shape is modified by the __________ __________ and __________ __________.

suspensory ligaments;
ciliary muscles.

The default (resting) position of the eye is when the lens is __________, and the suspensory ligaments are __________.

flat;
taut (pulled).

In the default (resting) position of the eye, __________ objects are viewed.

distant.

When ciliary muscles are contracted, __________ objects are viewed.

near.

When ciliary muscles are contracted, suspensory ligaments are __________, and the lens becomes __________.

loose;
rounded.

Process of changing shape of lens from flattened to round is called __________.

accomodation.

The __________ is thin pigmented smooth muscle.

iris.

The iris controls the amount of light entering the eye through __________ __________ __________.

pupillary light reflex.

The iris controls the amount of light entering the eye and affects __________ __________.

image quality.

The __________ is the opening in the center of the iris through which light passes.

pupil.

Two smooth muscles of the iris:

sphincter pupillae;
dilator pupillae.

The __________ pupillae is circular, contractile, and has parasympathetic innervation.

sphincter.

The __________ pupillae is radial, dilating, and has sympathetic innervation.

dilator.

The __________ is the innermost tunic of the eye.

retina.

The retina has 2 layers:

pigmented;
neural.

The __________ layer of the retina is adjacent to the choroid.

pigmented.

The pigmented layer of the retina provides __________ for the neural layers.

vitamin A.

The __________ layer of the retina absorbs light passing through the neural layer.

pigmented.

The __________ layer of the retina is the innermost layer of the eye.

neural.

The __________ layer of the retina contains photoreceptor cells and associated neurons.

neural.

The __________ layer of the retina transduces light energy into nerve signals.

neural.

Cells of the neural layer:

photoreceptor cells
bipolar cells
ganglion cells
horizontal cells
amacrine cells

__________ cells convert light energy into a nerve signal.

photoreceptor.

__________, __________, and __________ cells generate graded potentials.

photoreceptor;
bipolar;
horizontal.

Rods and cones are __________ cells.

photoreceptor.

__________ cells are the outermost cells of the neural layer.

photoreceptor.

__________ cells lie between photoreceptor cells and ganglion cells.

bipolar.

There are fewer __________ cells than photoreceptor cells.

bipolar.

__________ cells converge visual input onto the ganglion cells.

bipolar.

__________ cells are the innermost layer of neurons of the neural layer.

ganglion.

Axons of the __________ cells send signals to the CNS via optic nerve.

ganglion.

__________ and __________ cells generate action potentials.

ganglion;
amacrine.

__________ cells integrate stimuli between photoreceptor and bipolar cells.

horizontal.

__________ cells integrate visual information between bipolar and ganglion cells.

amacrine.

Photoreceptor cell that only has one type:

rods.

Rods are sensitive to wavelengths between __________-__________ nm.

400-600.

S (supra-frequency) cones are __________ cones.

blue.

M (mid-frequency) cones are __________ cones.

green.

L (low-frequency) cones are __________ cones.

red.

S cones are sensitive to wavelengths between __________-__________ nm.

380-550.

M cones are sensitive to wavelengths between __________-__________ nm.

400-650.

L cones are sensitive to wavelengths between __________-__________nm.

400-700.

There are 5% of __________ cones.

S (blue).

There are 30% of __________ cones.

M (green).

There are 60% of __________ cones.

L (red).

There is less __________ at the fovea.

convergence.

The fovea has high concentration of __________.

cones.

The fovea has no __________.

rods.

The fovea has a high concentration of __________ cells.

ganglion.

There is greater convergence in the __________.

periphery.

There is a low concentration of __________ in the periphery.

cones.

There is a high concentration of __________ in the periphery.

rods.

There is a low concentration of __________ cells in the periphery.

ganglion.

Acuity is dependent on the number of photoreceptor cells per __________.

ganglion.

Low convergence yields more __________.

acuity.

High convergence yields less __________.

acuity.

The degree of convergence correlates to __________ __________.

receptive field.

Low convergence yields __________ receptive fields and __________ acuity.

smaller;

greater.

High convergence yields __________ receptive fields and __________ acuity.

larger;
reduced.

__________ __________ produces cGMP from GTP.

guanylate cyclase.

__________ is stimulated by light absorption.

photopigment.

__________ is a G-protein that activates PDE when activated.

transducin.

__________ is an enzyme that converts cGMP to GMP.

phosphodiesterase (PDE).

__________ channel is activated cGMP.

CNG (cyclic nucleotide-gated).

Cyclic nucleotide-gated (CNG) channel allows __________ into cell when open.

Na+

In the dark, rod is __________.

depolarized.

In the dark, open CNG channels allow for the inflow of __________.

cations.

Inflow of cations in the dark results in the __________ of the photoreceptor cell.

depolarization.

Depolarized rod cell releases neurotransmitters to __________ the activity of the downstream bipolar cell.

inhibit.

Retinal __________ initiates visual transduction.

shape.

Light absorption results in retinal __________.

isomerization.

Absence of light causes retinal to be in __________ form.

cis.

Light absorption results in the retinal converting to its __________ form.

trans

Trans retinal form must be converted back to cis form before it can absorb another __________.

photon.