Flashcards in B1d-the nervous system Deck (31)
How do animals detect changes in their environment(stimuli) ?
Using receptors which generate nerve impulses
What does cornea do?
What does iris do?
Controls how much light enters pupil
What does lens do?
Focuses light onto retina
What does retina do?
Contains light receptors, some sensitive to light of different colours
What does optic nerve do?
Carries impulses to the brain
What is the pathway of light?
Refracted by cornea and lens
Brought to focus on the retina
What is accommodation?
The eye focusing light by changing shape of lens
How does the eye focus on distant objects?
-ciliary muscle relaxes
-suspensory ligaments pull tight
-lens less rounded light refracted less
How does the eye look at near objects?
Ciliary muscles contracts
Suspensory ligament slackens
Lens more rounded light refracted more
What is monocular vision?
Eyes on each side of head
Wider field of view
poorer judgement of distance
What is binocular vision?
-eyes side by side
-narrow field of view
-good judgement of distance
How does binocular vision help to judge distances?
-brain compares two images
-more similarities, further away the object
What is the cause of red green colour blindness?
Lack of specialised cone cells in retina
What is short sightedness?
Lens bends light too much
Images focused in front of retina
Cant see far away
What is long sightedness?
Lens doesn't bend light enough
Images focused behind retina
Cant see close up
What kind of lenses are used to correct short sightedness?
What kind of lenses are used to correct long sightedness?
What is a nerve impulse?
An electrical signal that is carried by nerve cells called neurones
What are reflex actions?
Fast,automatic and protective responses
What are voluntary responses?
Responses that are under the conscious control of the brain
What are the parts of a motor neurone?
What happens on the axon of a neurone?
Nerve impulses pass along the axon
What is the pathway of a reflex arc?
Central nervous system
What is the pathway for an involuntary response?
Relay neurone in spinal cord
How does the length of neurone help their function?
They're long which speeds up the impulse
How does a neurones insulating sheath help their function?
The sheath along the axon acts as an electrical insulator which speeds up the electrical impulse
How do neurones dendrites help their function?
These branched endings means they can connect with lots of other neurones
What is a synapse?
The gap between neurones
What does an impulse trigger in a synapse?
An impulse triggers the release of a transmitter substance in a synapse and it diffuses across to bind with receptor molecules in the membrane of the next neurone causing the impulse to continue