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CHAPTER 1

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Pathway from stimulus to response

Stimulus

Effectors (e.g:

Muscle, glands)

Nerves

Brain

NervesReceptors in

sensory organ

Response

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SKIN

Muscle Nerves

Brain

Nerves

Receptors

(touch, pain,

heat, cold,

pressure)

Touch,

pressure,

pain &

temperature

Response

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Touch

receptors

Pain

receptors Cold

receptors

Pressurereceptors

Blood

vessels

Heatreceptors

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NOSE

Muscle Nerves

Brain

NervesReceptors

(sensory cells)

Smell

(chemical in

air)

Response

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Sensory Cells

Nostrils

Nasal

cavity

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Tongue

Muscle Nerves

Brain

NervesReceptors

(taste buds)

Taste

(chemical in

food)

Response

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EAR

Muscle Nerves

Brain

NervesReceptors in

cochleaSound

Response

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Pinna

Ear canalOssicles

Oval

windows

1. Pinna 2.Ear canal - 3. Eardrum (vibrate) - 4. Ossicles

(amplify) - 5. Oval Windows (transfer) -6.Cochlea (fluid,

receptors) - 7. Auditory nerves 8.Brains

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EYE

eye lid Nerves

Brain

NervesReceptors

(Photoreceptors)Light

Response

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Conjunctiva

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Conjunctiva

1. Light rays travel to eyes

2. Refracted (bent) by cornea, aqueous humour, lens,

vitreous humour3. Upside down image formed on retina

4. Photoreceptors on retina send impulses along optic

nerve to brain

5. Brain interprets impulses and see object right way up.

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Reflection- light bounces off the

surface of object.

Refraction- bending of light ray

when enters medium of different

density

LIGHT

REFELCTION AND REFRACTION

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DEFECT OF VISION

1. Short-sightedness

2. Long- sightedness

3. Astigmatism4. Limitations of sight

- optical illusions

- blind spot

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Visual field of both eyesoverlap.

Brain combines 2 images into

1 so can see things 3dimensionally

Helps animals to judge

distances accurately. Predators - Tiger, owls,

wolves

STEREOSCOPIC VISION

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Visual field little and nooverlapping

Helps them to detect enemies

from wide range of directions Prey- Rabbits, chickens, deer

MONOCULAR VISION

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Hear sounds fromsurrounding with 2 ears

Enables us to distinguishdirection of sound

Enables us to determine thesource of sound.

STEREOPHONIC HEARING

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Produced by vibrations

Needs medium to travel Hard, smooth surface good

reflector

Soft, rough surface

goodabsorbers

SOUND PRODUCTION,

REFELCTION, ABSORPTION

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Stimuli and Responses

in Plants

Plants respond by growing in

certain direction.

Plant growth responses

tropisms

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Hydrotropism Response to water

Growth movement of plant in response to water.

Roots tends to grow towards water. (Positive

hydrotropism)

Plant absorb water from soil through roots.

Ensures plant get enough water and minerals tomaintain growth.

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Geotropism Response to gravity

Plant growth movement in response to gravity.

Roots always grow downwards, in the direction of

gravity (Positive geotropism) to find water and to

anchor firmly into soil.

The shoots grow upwards away gravity (Negative

geotropism) Ensures shoots receive sunlight for

photosynthesis.

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Phototropism Response to light

Plant growth movement response to light.

Shoots (Positively phototropism) - ensures

leaves receive enough sunlight forphotosynthesis.

Roots (Negatively phototropic).

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Thigmotropism Response to

touch

Response by plants to contact with a solid

structure.

Climbing plants are too weak to support their

own weight, so they rely on other objects tokeep them upright.

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Nastic movement

Two kinds of growth movement tropisms and nastic

movement.

Tropisms or tropic movement

response to stimuli whichcome from one direction.

Nastic movement response to stimuli which come from

any direction, not depend on the direction of stimuli.

Mimosa pudica, Venus fly trap respond quickly to touch.