Chapter 15 Special Senses

Question 1

In the Fibrous Layer of the Eyeball what are the two regions that make it up?

Answer 1

1- Sclera: forms posterior portion and helps shape eyeball. It is pierced by the optic nerve.

2- Cornea: Crystal clear, acts like a window that allows light to enter the eye. Major player in LIGHT BENDING APPARATUS.

Question 2

In the Vascular Layer of the Eyeball what are the 3 key features?

Answer 2

1- Choroid: is blood vessel rich and forma majority of the vascular layer. Helps to nourish eyeball and its color •comes from brown pigment MELANOCYTES that help absorb light with cells.

2- Ciliary body: Found encircling our lens to help shape it. Consists of smooth muscle to control shape of lens.

3- Iris: Visible colored part of eye, contains round central opening called PUPIL that allows light into the eye.

Question 3

In the Inner Layer (Retina) what are the two layers that make it up?

Answer 3

1- Pigmented Layer of the retina: the outer layer found right next to the choroid. helps to prevent light from scattering. The cells here store VITAMIN A.

2- Neural Layer of the retina: has 3 main types of neurons.
•Photoreceptors
•Bipolar cells
•Ganglion Cells

Question 4

What are the four components of the eyeball? (3 layers, one component)

Answer 4

1- Fibrous layer- outermost coat of the eye.

2- vascular layer- forms middle coat of the eyeball.

3- inner layer (retina): inner most layer contains millions of photoreceptors.

4- Lens: bi-convex shaped, transparent, smooth muscle helps to allow flexibility to change shape to precisely focus light.

Question 5

What is in the fibrous layer of the eye?(2)

Answer 5

1- Sclera: forms posterior portion helps shape eyeball

2- Cornea: crystal clear acts like a window that allows light to enter the eye.

Question 6

What is electromagnetic radiation?

Answer 6

Includes all energy waves, from long radio waves, X-rays, gamma rays.

Question 7

What are photons?

Answer 7

Small particles or packets of energy traveling in waves in high speeds

Question 8

What is a visible spectrum?

Answer 8

When light passed through a prism each of its component waves bends to a different degree, so that the beam of light is dispersed and a band of colors is seen

Question 9

Describe objects that look white, and objects that look black

Answer 9

Things that look white REFLECT all wavelengths of light.

Black objects ABSORB all the wavelengths.

Question 10

Describe refraction.

Answer 10

Is when light is traveling through a given medium it’s speed alters. Through a less dense medium light speeds up, but through a more dense medium light slows down. Which in turn can cause the light to bend or refract when it meets the surface of a different medium at an oblique angle rather than at a right angle.

Question 11

What is a Lens?

Answer 11

Is a transparent object curved on one or both surfaces. Since light hits the curves at an angle, it is refracted.

Question 12

What is the focal point?

Answer 12

Is when the surface of the lens is convex .. ) … The light rays are bent so that they converge and come together at a single point.

Question 13

What is the real image?

Answer 13

Is when the image formed by a convex lens is upside down and reversed from left to right and sent to the retina to be interpreted.

Question 14

Describe the far point of Vision

Answer 14

Is the distance beyond which No change in lens shape is needed for focusing. For the normal eye the distance is 20 feet.

Question 15

What 3 processes need to occur to the lens in order to see close vision?

Answer 15

1) Accommodation of the lenses: process that causes the lens to bulge and then you have shorter focal length needed to focus the image of a close object on the retina.
2) Constriction of the pupils: the size of the pupil reduces.
3) Convergence of the eyeballs: have medial rotation of the eyeball, makes the eyeballs come in.

Question 16

Describe the far point of Vision

Answer 16

Is the distance beyond which No change in lens shape is needed for focusing. For the normal eye the distance is 20 feet.

Question 17

What 3 processes need to occur to the lens in order to see close vision?

Answer 17

1) Accommodation of the lenses: process that causes the lens to bulge and then you have shorter focal length needed to focus the image of a close object on the retina.
2) Constriction of the pupils: the size of the pupil reduces.
3) Convergence of the eyeballs: have medial rotation of the eyeball, makes the eyeballs come in.

Question 18

What is presbyopia?

Answer 18

Old person’s vision , where the lens is nonaccomodating

Question 19

What is phototransduction?

Answer 19

Is the process by which light energy is converted into a graded receptor potential

Question 20

Describe the outer segment and visual pigments(photo pigments)

Answer 20

The outer segments are turned upside down and have tips (receptive region) embedded into pigmented layer. The outer segment contain an elaborate array of visual pigments that change shape as they absorb light

Question 21

Describe the inner segment

Answer 21

It connects to the cell body, which is continuous with an inner fiber bearing synaptic terminals.

Question 22

What is rhodopsin?

Answer 22

Consists of retinol and Olson where it is embedded in the membrane in rod discs.

Question 23

What is the difference between Rod vision vs Cone vision?

Answer 23

Rods are very sensitive to dim light, they are best suited for NIGHT vision & PERIPHERAL vision. Contain only one pigment and perceive only Gray Tones.

Cones need BRIGHT LIGHT for activation. Not as sensitive to light. Have 1 of 3 types of pigments: Blue, Red, or Green pigment and provide us with color of the world.

Question 24

What is retinal?

Answer 24

A light absorbing molecule. It combines with a protein called Opsin to form four visual pigments. It is made up of Vitamin A. Has two different forms.

Question 25

What are the two different types of Retinal?

Answer 25

1) 11-cis retinal bound to Opsin and forms a kink shape.

2) all-trans retinal gets formed when light strikes it and absorbs photons it snaps into this new configuration.

Question 26

Describe the visual pathways and processing.

Answer 26

1) The axons of the retinal ganglion cells issue from the back of the eyeballs in the OPTIC NERVES
2) at the X shaped OPTIC CHIASMA, fibers from the medial aspect of each eye cross over to the opposite side
3) and then continue via the OPTIC TRACTS. Which contain fibers from the lateral aspect of the eye on the same side and fibers from the medial aspect of the opposite eye.

Question 27

What is myopia?

Answer 27

“Near-sightedness” occurs when distant objects are focused not on, but in front of the retina. Results from the eyeball being too long. Correction is made by concave lenses that diverge the light before it enters the eye.

Question 28

What is Hyperopia?

Answer 28

“Far-sightedness” occurs when the parallel light rays from distant objects are focused behind the retina.
Results from eyeball being too short. Correction is done by convex lenses and bifocals.

Question 29

What is an astigmatism?

Answer 29

Is unequal curvatures in different parts of the cornea or lens and leads to blurry images.

Question 30

What are chemoreceptors?

Answer 30

They are receptors for smell/taste and respond to chemicals in aqueous solutions.

Question 31

Describe Olfactory epithelium. 3 cell types?

Answer 31

Located at the roof of the nasal cavity, consists of psuedostratified epithelium (olfactory epithelium). It is found covering the concha on both sides of the septum, contains olfactory receptor cells, supporting cells and basal cells

Question 32

What are olfactory receptor cells?

Answer 32

There are millions of these receptors that are bowling pin shaped in the olfactory epithelium

Question 33

What is the activation of the olfactory receptors?

Answer 33

In order for us to smell an odorant, it must be volatile(gaseous state) to enter the nasal cavity. It then must Dissolve in the fluid coating the Olfactory epithelium. The dissolved odorants stimulate the olfactory receptors by binding to protein receptors in the cilium membrane and opening cation channels. This leads to receptor potential and ultimately to an action potential(if threshold is met) that is conducted to the first relay in olfactory bulb.

Question 34

Describe smell transduction.

Answer 34

This uses a receptor which activates a G protein which activates enzymes that synthesize cyclic AMP as a second messenger. Cyclic Amp acts directly on a plasma membrane cation channel, opens gate and allows Na and Ca to enter. Na leads to depolarization. In turn causes membrane potential to change, if excitatory action potential is generated

Question 35

What are olfactory bulbs?

Answer 35

Are distal ends of the olfactory tracts.

Question 36

What are mitral cells?

Answer 36

When synapse come together with olfactory nerves to brain.