Coordination and Response (The Sense Organs).

Question 1

What are sense organs?

Answer 1

Sense organs are a group of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals.

Question 2

What is the function of the cornea of the eye?

Answer 2

Cornea is transparent and refracts light.

Question 3

What is the function of the iris of the eye?

Answer 3

Iris controls how much light enters the pupil.

Question 4

What is the function of the lens of the eye?

Answer 4

Lens is transparent and can change shape to focus light onto the retina.

Question 5

What is the function of the retina of the eye?

Answer 5

Retina contains light recepetor cells, some sensitive to light of different colours (rods - detect light intensity; cones - detect colour).

Question 6

What is the function of the optic nerve of the eye?

Answer 6

Optic nerve sensory neurone that carries impulses from the eye to the brain.

Question 7

What is the function of the pupil of the eye?

Answer 7

The pupil is a hole that allows light to enter the eye.

Question 8

What is the pupil reflex?

Answer 8

This is an involuntary reflex action carried out to protect the retina from damage in bright light and allows more light to enter your eye in dim light.

Question 9

Explain the pupil reflex limited to changes in dim light intensity and pupil diameter.

Answer 9

In dim light, the pupil dilates to allow more light to enter the eye to improve vision.

Question 10

Explain the pupil reflex limited to changes in bright light intensity and pupil diameter.

Answer 10

In bright light, the pupil constricts to allow less light to enter the eye to protect the retina from damage (bleaching).

Question 11

Explain the pupil reflex in terms of the antagonistic action of circular and radical muscles in the iris in regards to dim light.

Answer 11

In dim light, radical muscles contract, circular muscles relax and the pupil dilates and more light to enter the eye.

Question 12

Explain the pupil reflex in terms of the antagonistic action of circular and radical muscles in the iris in regards to bright light.

Answer 12

In bright light, radical muscles relax, circular muscles contract and the pupil constricts and less light enters the eye to protect the retina from damage by bleaching.

Question 13

What muscles work antagonistically in the eye?

Answer 13

The muscles that work antagonistically are the radical muscles and the circular muscles of the eye.

Question 14

Define the accommodation of the eye?

Answer 14

Accommodation is the function of the eye in focusing on near and distant objects.

Question 15

How can the shape of the lens be changed?

Answer 15

The lens is elastic and its shape can be changed when the suspensory ligaments attached to it become tight of loose.

Question 16

Explain accommodation to view near objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light.

Answer 16

The ciliary muscles contract which causes the suspensory ligaments to loosen making the lens fatter and curved and light is refracted more by the lens to focus on the nearby object.

Question 17

Explain accommodation to view distant objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light.

Answer 17

The ciliary muscles relax which causes the suspensory ligaments to tighten and pull on the lens marking it thinner and less curved and light is refracted less, allowing the eye to focus on the distant object.

Question 18

There are two types of receptor cells in the retina: NAME THEM.

Answer 18

There are two types of receptor cells in the retina:
- Rods which are sensitive to dim light.
- Cones which distinguish between different colours in bright light.

Question 19

Describe the distribution of rods in the retina of a human.

Answer 19

Rods are evenly distributed and less tightly packed at the periphery of the retina; absent at the fovea.

Question 20

Describe the distribution of cones in the retina of a human.

Answer 20

Cones are found tightly packed in the fovea.

Question 21

Outline the function of rods.

Answer 21

Greater sensitivity of rods for night vision.

Question 22

Outline the function of cones.

Answer 22

Three different kinds of cones, absorbing light of three different colours (red, blue, green) for colour vision.