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9 Cards in this Set
- Front
- Back
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Describe the central nervous sytem (CNS) |
- The central nervous system (CNS) includes the brain and spinal cord but excludes the peripheral nervous system (PNS). - 31 one pairs of spinal nerves (left to right ) fan out from the spinal cord to form the PNS. |
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Describe the nerve impulse path |
- Nerve impulse path - Sensory receptor stimulated (e.g. skin), nerve impulses ( electrical messages ) sent via a sensory (afferent) nuerone ( asecending pahtway ) of the peripheral nervous system (PNS) to the central nervous sytem (CNS ) via a motor (effrent ) neurone (of the PNS) to an effector (muscle or gland). |
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Describe the action of the Reflex arc |
Reflex arc - sesnory receptor neurone stimulated (e.g. hot surface); nerve impulse sent via an afferent neurone to a motor neurone via an internuerone ( a relay neurone ) in the spinal cord ( the brain receives an impulse latter). - the carebral cortex can ovverride the reflex arc (e.g. not wishing to drop a valuable hot object). |
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Desscribe the Autonomic (involuntary ) nervous system (ANS)
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- ANS controls the automatic fucntion of the body that maintains stable internal conitions (i.e. homeostatis ) e.g. respiration, heart rate , blood pressure , temperature and salt-water balance. - The hyothalamus regulates many of the body's autonomic systems (e.g. temperature through vasodilation/constriction) |
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What is the function of the iris |
- Iiris controls the amount of light enerting the pupil by contracting the ciruclar muscle (for bright light ) or the radial muslce ( in dim light) - the dilation or constriction of the pupil is by autonomic reflex arc. |
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What is the function of the Photoreceptors |
- Photorecepotrs (light - sensitive rod and cone cells), contained in the ratina , measure intensity, wavelenght and poistion of light. |
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How are impulses transmited from the eye to the brain |
-Impulses are relayed via ganglion cells to the optic nerve, which transmits impluses to the brain. -The image on the retina is inverted and results from the reflection of light at the cornea with fine adjustment at the lens : the image is sharpest near the centre of the retina at the lovea. |
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How can the focus of the lnes be altered from infinity (parallel light ) to a near object? |
- focus of the lens can be altered from infity ( parallel light ) to a near object by the accomodation reflex |
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Which muslces ares responsible for changing the sahpe of the lens ? |
The ciliary musclers are respionsible for changing the shape of the lens; near objects =ciliary muscles contract = suspensory ligaments loose = more convex lens ( fatter) = more diffractionm distant object = cillary muslces relaxed = suspensory ligaments taut = less lens (thinner ) = less diffraction. |
