14.2 Mammalian Sense Organs (Cambridge (CIE) O Level Biology): Flashcards
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Define receptor.
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Cards in this collection (23)
Define receptor.
A group of specialised cells that detect a change (stimulus) in the environment and start an electrical impulse.
Define sense organ.
An organ containing groups of receptors that respond to a specific stimulus.
What stimulus is the eye sensitive to?
Light.
What are the ear's receptors sensitive to?
Sounds and movement, giving hearing and balance.
Which sense organ detects chemicals in food and drink?
The tongue, giving the sense of taste.
What does a receptor do when it detects a stimulus?
It generates an electrical impulse that passes to a sensory neurone.
Which sense organ detects heat, cold, pressure and pain?
The skin.
The is the sense organ that detects chemicals in the air, giving the sense of smell.
The nose is the sense organ that detects chemicals in the air, giving the sense of smell.
When stimulated, a receptor passes an impulse to a neurone, which carries it to the central nervous system.
When stimulated, a receptor passes an impulse to a sensory neurone, which carries it to the central nervous system.
True or False?
The eye is a sense organ that is sensitive to light.
True.
The eye contains light receptors that respond to the stimulus of light.
True or False?
A receptor is a single cell that responds to every kind of stimulus.
False.
Receptors are groups of specialised cells, and each type responds to a specific stimulus.
Define accommodation.
The way the lens changes shape to focus light from near and distant objects onto the retina.
What is the function of the cornea?
It refracts (bends) light as it enters the eye.
What is the function of the iris?
It controls how much light enters the pupil.
What is the function of the retina?
It contains the light receptors that detect light.
What happens to the pupil in bright light?
It constricts (narrows) to protect the retina from damage.
In dim light, what do the radial and circular muscles of the iris do?
Radial muscles contract and circular muscles relax, so the pupil widens (dilates).
How does the eye focus on a near object?
The ciliary muscles contract, the suspensory ligaments loosen, and the lens becomes fatter, refracting light more.
How does the eye focus on a distant object?
The ciliary muscles relax, the suspensory ligaments tighten, and the lens becomes thinner, refracting light less.
The carries nerve impulses from the retina to the brain.
The optic nerve carries nerve impulses from the retina to the brain.
In bright light the pupil to reduce the amount of light entering the eye.
In bright light the pupil constricts to reduce the amount of light entering the eye.
True or False?
When focusing on a near object, the lens becomes thinner.
False.
When focusing on a near object the lens becomes fatter; the ciliary muscles contract and the suspensory ligaments loosen.
True or False?
The pupil reflex helps protect the retina from damage in bright light.
True.
In bright light the pupil constricts to stop too much light reaching and damaging the retina.
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