INTERNATIONAL TURKISH HOPE SCHOOL ACADEMIC YEAR CHITTAGONG SENIOR SECTION BIOLOGY CO-ORDINATION CLASS 09 and 10 Name :... Date :...

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Tobias Logan
5 years ago
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15 play important role in Homeostasis. 15 P a g e

16 Q. A girl is seated at a desk reading from a chart at the end of the classroom. The girl then looks at her book on the desk in front of her. What changes occur in the girl's eyes so that she can focus on the book? Accommodation is the adjustments made in the eye for near and far sights. The majority of the bending or refraction that brings about image formation takes place at the surface of the cornea, with the lens contributing only about one quarter of the total refraction. The refraction at the cornea remains constant, so the lens must adjust the bending of light rays. The light rays become more diverging as the girl s view moves from the chart at the end of the classroom to her book on the desk in front of her. To keep rays from the book focused on the retina (on the fovea), the ciliary muscles contract and the suspensory ligaments slacken. As a result the lens is no longer stretched, i.e. no longer pulled into a thin shape. The elasticity of the lens allows it to become more rounded and so the girl s eyes can focus on the book. Q. In a mammal, describe how the focus of the eye is changed when looking at a distant object after a near object. The majority of refraction in the eye, that brings about image formation, occur at the surface of the cornea, with the lens contributing only about one quarter of the total refraction. The refraction at the cornea is constant and therefore the lens must adjust to bend the rays of light as required. This is known as accommodation. When the eye focuses on something close such, as a pencil, the ciliary muscles contract, and the ligaments surrounding it pull less strongly on the lens. The lens springs to a round shape, allowing the eye to focus rays of light from the object on the retina (on the fovea). Lights rays from distant objects are more converging and to focus on something far away, the ciliary muscles relax and the ligaments surrounding the lens become taut. The lens becomes flatter allowing the eye to focus on the distant object. Q. Describe what happens to light from the time it passes through the cornea of the eye of a human until it stimulates the receptor in the retina. Humans can see when light from an object falls on the retina (on the fovea), where sensitive cells are stimulated sending impulses along the optic nerve to the brain. The majority of refraction in the eye, that brings about image formation, occur at the surface of the cornea, with the lens contributing only about one quarter of the total refraction. The refraction at the cornea is constant and therefore the lens must adjust to bend the rays of light as required. This is known as accommodation. When the eye focuses on something close such, as a pencil, the ciliary muscles contract, and the ligaments surrounding it pull less strongly on the lens. The lens springs to a round shape, allowing the eye to focus rays of light from the object on the retina (on the fovea). 16 P a g e

17 Lights rays from distant objects are more converging and to focus on something far away, the ciliary muscles relax and the ligaments surrounding the lens become taut. The lens becomes flatter allowing the eye to focus on the distant object. Q. What do you mean by Antagonistic Muscles? Describe their importance during the movement of your arm. Two muscles work simultaneously, when one contracts the other relaxes. Pairs of muscles like that are called antagonistic muscles. The most known antagonistic muscle pair is the biceps and triceps of the arm. The bi and the tri for short, they are what causes the movement of the arm. They work simultaneously to bend or straighten the arm. The biceps is located in front of the humerus bone of the upper arm. The biceps is joined to the radius bone of the lower arm and the triceps is joined to the ulna bone of the lower arm. Muscles are attached to bones by strong fibres called tendons. When you want to bend your arm the brain send two electrical impulses, one to the bi making it contract and one to the tri telling it to relax. When the bi contracts, it becomes shorter pulling the bones to which it is attached close and bending the arm. This causes the fibres of the tri to stretch while they are relaxed. To straighten your arm, the brain send electrical impulses to both muscles making the bi relax in order to leave the muscle it is attached to free. The tri contracts and becomes shorter pulling the muscle it is attached to into place and straightening the arm. The biceps can be called a flexor because it flexes (bends) the arm. The triceps can be called an extensor because it extends (straightens) the arm. 17 P a g e

EYE. The eye is an extension of the brain

EYE. The eye is an extension of the brain I SEE YOU EYE The eye is an extension of the brain Eye brain proxomity Can you see : the optic nerve bundle? Spinal cord? The human Eye The eye is the sense organ for light. Receptors for light are found