Question

2. Categorise the following under stimulus and
response
(i) Withdrawal of hand on touching a hot plate
(ii) Seeing a green light turning into red at a road crossing
before applying the brakes
(iii) Pain in the eye if something falls into it.​

Answer 1

Explanation:

(I)Withdrawal of hand on touching a hot plate: Response

Explanation: When we touch a hot plate, the sensory neurons get activated. These sensory nerve cells carry information to the brain/spinal cord which activates the motor neurons. The motor neurons transmit the signal to the hand muscles to remove the hand from the hot plate. Hence the withdrawal of hand on touching a hot plate is the response.

(ii) Seeing a green light turning red at a road crossing before applying the brakes: Stimulus

Explanation: Here the emphasis is given to “seeing” the green light turning red at a road crossing. The sensory nerves sense the message of green light turning to red. These nerve cells transmit this message to the brain. The brain interprets the message (that we should apply the brake) and sends it via the motor nerves to the muscles which express the response (applying the brake).

(iii) Pain in the eye if something falls into it: Response

Explanation: The transparent cornea of the eye contains many fine nerve fibers, which react very sensitively to touch and injury. That is why it is so uncomfortable when a foreign object like a grain of sand or an insect enters the space between your eyeball and your eyelid or gets under your contact lens. Your eye starts to hurt and it waters a lot. If the cornea is scratched, it will feel as though something is stuck in your eye. And this can also cause other symptoms, like sensitivity to light and blurry vision.

Answer 2

Answer: A stimulus is an event or condition which initiates a response whereas response is the organism's reaction to any particular stimulus.

Explanation:

Here,

1.Withdrawal of hand on touching a hot plate: Response

Explanation: When we touch a hot plate, the sensory neurons get activated. These sensory nerve cells carry information to the brain/spinal cord which activates the motor neurons. The motor neurons send the signal to the hand muscles to remove the hand from the hot plate. Hence it is a response.

2.Seeing a green light turning red at a crossing before applying the brakes: Stimulus

Explanation: Here the event is  “seeing” the green light turning red at a road crossing. The sensory nerves sense the message to the brain. The brain interprets the message (that we should apply the brake or wait for the signal to turn green again) and sends it via the motor nerves to the muscles which express the response required.

3. Pain in the eye if something falls into it: Response

Explanation: The transparent cornea of the eye has  many fine nerve fibers, which are sensitive to touch and injury. Our eye starts to hurt if a foreign object enters the eye. If the cornea is scratched, it shows response like action to clear the eyes.  Thus it is an example of response.

SPJ2