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Definition
| a change in the environment, either internal or external, that is detected by a receptor and elicits a response |
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Definition
| to carry out a res[pmse after receiving a message from a motor neuron; effectors can be muscles, which respond by contracting, or glands, which respond by secreting |
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| components of a reflex arc |
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Definition
1. receptors
2. sensory neurons
3. relay neurons
4. motor neurons
5. effectors |
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Definition
mechanical energy in the form of sound waves, movements due to pressure or gravity
e.g. hair cells in the cochlea of the ear,
pressure receptor cells in the skin |
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Definition
chemical substances dissolved in water (tongue)
chemical substances as vapours in the air (nose)
e.g. receptor cells in the tongue, nerve endings in nose |
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Definition
temperature
e.g. nerve endings in the skin detect warm or cold |
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Definition
electromagnetic radiation, usually in the form of light
e.g. rod and cone cells in the eye |
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Term
| perception of sound in the eardrum |
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Definition
| when sound waves reach the eardrum at the end of the outer ear, they make it vibrate. The vibration consists of rapid movements of the eardrum, towards and away from the middle ear. The role of the eardrum is to pick up sound vibrations from the air and transmit them to the middle ear |
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Term
| perception of sound in the bones of the middle ear |
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Definition
| there is a series of very small bones in the middle ear, called ossicles. Each ossicle touches the next one. The first ossicle is attached to the eardrum and the third one is attached to the oval window. The ossicles' role is to transmit sound waves from the eardrum to the oval window. They also act as levers, reducing the amplitude of the waves, but increasing their force, which amplifies sounds by about 20 times. The oval window's small size, compared with the eardrum, helps with amplification. Muscles attached to the ossicles protect the ear from loud sounds, by contracting to damp down vibrations in the ossicles |
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Term
| perception of sound in the oval window |
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Definition
| this is a membranous structure, like the eardrum. It transmits sound waves to the fluid filling the cochlea. This fluid is incompressible, so a second membranous window is needed, called the round window. When the oval window moves towards the cochlea, the round window moves away from it, so the fluid in the cochlea can vibrate freely, with its volume remaining constant |
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| perception of sound in the hair cells in the cochlea |
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Definition
| the cochlea consists of a tube, wound to form a spiral shape. Within the tube are membranes, with receptors called hair cells attached. These cells have hair bundles, which stretch from one of the membranes to another. When the sound waves pass through the fluid in the cochlea, the hair bundles vibrate. Because of gradual variations in the width and thickness of the membranes, different drequencies of sound can be distinguished, because each hair bundle only resonates with particular frequencies. When the hair bundles vibrate, the hair cells send messages across synapses and on to the brain via the auditory nerve |
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Term
| differences between rod and cone cells |
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Definition
1. rod cells are more sensitive to light than cone cells, so they function better in dim light. Rode cells become bleached in bright light, but cone cells function well
2. rod cells absorb all wavelengths of visible light, so they give monochrome vision, whereas there are 3 types of cone cell sensitive to red, green and blue light
(giving colour vision)
3. groups of up to 200 rod cells pass impulses to the same sensory neuron of the optic nerve, whereas many cone cells have their own individual neuron through which messages can be sent to the brain - cone cells therefore give greater visual acuity than rod cells
4. rod cells are more widely dispersed through the retina so they give a wider field of vision, whereas cone cells are very concentrated near the fovea, giving one acute area of the field of vision |
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