The Nervous System Flashcards
What is the job of the cornea and the lens?
The cornea refracts the light rays that enter the eye slightly, and the lens refracts them even more so that the light rays are focused on the retina at the back of the eye.
How is binocular vision useful for predators?
It helps to judge distance. The more different the two images are, the closer they are.
What is accommodation?
When the eye changes shape so the light can be focused on the back of the retina.
What is the process of focusing on something in the distance?
1) Ciliary muscles relax
2) Suspensory ligaments tighten
3) Lens becomes less rounded
What is the process for focusing on something close up?
1) Ciliary muscles tighten
2) Suspensory ligaments relax
3) Lens becomes more rounded
What is red-green colourblindness caused by?
A lack of receptors in the retina.
How can someone be long sighted?
- Eyeball is too short
- Lens is too thin
- The light is focused behind the retina because it refracts too little
How can someone be short sighted?
- Eyeball is too long
- Lens is too thick
- The light is focused in front of the retina because it refracts too much
What corrects long sight and short sight?
- Long sight: convex lens
- Short sight: concave lens
- Both: corneal surgery
How do nerve cells give commands?
Impulses are passed along the axon of a neurone.
What is the sequence of a reflex arc?
1) Stimulus
2) Receptor
3) Sensory neurone
4) Central nervous system
5) Motor neurone
6) Effectors
7) Response
What is the sequence of a spinal reflex?
1) Receptor
2) Sensory neurone
3) Relay neurone
4) Motor neurone
5) Effector
How is a neurone adapted?
- Long
- Branched endings (dendrites) for picking up impulses
- Insulator sheath so impulses can hop over
What is a synapse and what is its purpose?
A synapse is the gap between neurones. As an impulse arrives it trigger neurotransmitter to diffuse across it and the transmitter bind to the receptor molecule of the next neurone.
