F2 Cp1 Express Notes.docx

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HOTS: Explain how the nervous system responds to a stimulus. -The nerves send nerve impulses (information) from the receptors to the spinal cord and brain. -The brain and spinal cord interprets the message and decide what to do. -Nerve impulses are sent to effectors (muscle, glands, etc.) to respond to the stimuli through nerves.

HOTS:  Blind people use the high sensitivity of their fingertips to read in Braille. Raised dots are used to represent letters and numbers.  Doctors give injections to their patients at the forearms or hips. One of the reasons for this is these areas are less sensitive to pain.  The back of the hands has a lot of heat and cold receptors (temperature). Mother test the temperature of their babies' milk on the back of their hands.

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Sensitivity of Skin depends on: -Thickness of epidermis -Number of receptors/ Distance between the receptors. ©Eric K. 120817

How is the structure of the skin of a snake? The outer layer of scales, called the epidermis, is very thin--only 1/10 of a millimetre at most. This is where cells constantly divide from the base layer and move up to the surface to be sloughed off. Just below the epidermis is a second layer, the dermis, which doesn't undergo the same process of constant replacement. Their bodies are covered with scales, small diamond shapes on the top and long rectangles on the bottom side. The underside scales are called "scutes." How is it different from human skin? Which structures are present and which are missing? Human skin have three basic layers: epidermis, dermis containing receptors and nerve endings, subcutaneous layer that mostly made up of fats. Snakeskin has two layers--an outer layer of scales and an inner layer containing the nerve endings and colour pigment cells. Snakes have smooth dry skin. They are not wet and slimy. Their bodies are covered with scales. There are no scales in human body.

Consider how a snake moves and predict what would happen if snakes had human skin. The "scutes". help the snake move by catching on stones, branches and other irregularities on the ground. If snakes had human skin they wouldn't move easily on the ground.

HOTS:  When a person catches a cold, they cannot detect smell well. The nose produces too much mucus which prevents chemicals from stimulating the smell receptors.  A dog's sense of smell is hundred times more sensitive than human. Therefore, dogs are being used to track criminals and to sniff out drugs or explosives.  Our nose commonly acts as an early warning system for our body. E.g. of situations in which we use our

nose to detect danger before we detect it with our other senses are: Gas leakage, smoke, burned food, rotten food, heavy smell of gasoline

related. The nasal cavity and mouth are connected. When we eat/ drink, chemicals from food move up to nasal cavity and stimulate the smell receptors in the nose as well.

Hearing Mechanism 1. The pinna gathers sound waves and directs them to the auditory canal. 2. The sound waves travel along the auditory canal and reach the eardrum. It vibrates at the same frequency as the sound waves. 3. The vibrations are transferred to the ossicles. The ossicles amplify the vibration 20 times in magnitude before passing to the oval window. 4. Vibration of the oval window cause the fluid in the cochlea to vibrate. 5. The movement of the fluid stimulates the receptors in the cochlea. Nerve impulses are generated. 6. The auditory nerve sends the nerve impulses to the brain. 7. The brain interprets the message as sound.

HOTS: When a person get cold, the air passages in the nose are blocked. This reduces the sensitivity of the smell receptors. Food become less tasty or different from its original taste as the sense of smell and taste are closely ©Eric K. 120817

HOTS:  Parts of the ear which are not involved in hearing: Semicircular canal- Help the body to maintain its balance Eustachian tube- Help to balance the air pressure on

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both side of the eardrum. Why we feel dizzy when taking a lift? Semicircular canal is disturbed. This part of the ear controls the body balance. Why sometimes we have the sensation of popped ears?

©Eric K. 120817

Our ears sometimes pop because of the change of air pressure. When we fly on an airplane, climb a mountain, dive under the water, etc... It is the middle ear that causes trouble during pressure changes, because it is an air pocket inside the head. Yawning or swallowing remedy the discomfort in the ear.

Application on Reflection of light:

Phenomenon of Refraction of light

©Eric K. 120817

©Eric K. 120817

©Eric K. 120817

©Eric K. 120817