Nerves and hormones Flashcards
What is a stimulus?
A change in the environment
What are the 5 senses and what are their receptors?
Sight - eyes have light receptors
Ears - sound and balance receptors
Nose - smell receptors, chemical stimuli
Tongue - taste receptors, chemical stimuli
Skin - nerve cells carry signals as electrical impulses from the skin receptors
What are receptors?
Groups of cells which are sensitive to a stimulus, changing stimulus energy into electrical impulses
What are effectors?
Something that does an action due to a stimulus (muscle or hormone glands)
What is a synapse?
A gap between neurones where the electrical signal turns into a chemical signal to cross the gap by diffusion
What is the CNS?
Located in the spine, the central nervous system is where the information from the sense organ goes
It consists of the brain and the spinal cord
Why are reflexes useful?
They are automatic responses and can reduce the chance of being injured as you act quickly without thinking
What is the route taken by the information in a reflex called?
The reflex arc
What does the reflex arc consist of?
Stimulus
Receptors receive the energy
Converts it into an electrical impulse and sends it across the sensory neurone
Message is passed through the CNS on the relay neurone
Message travels through the motor neurone to the effector
The effector activates when the electrical impulse hits
What do neurones look like and why?
They have branched endings to connect to other neurones and they’re long to speed up the impulse (fewer connections mean a quicker signal
What does the cornea do?
The transparent bit at of the sclera at the front of the eyeball. This bends light into the eye, focusing it on the retina
What is the pupil?
A hole in the eye to let light through
What is the iris?
A muscle which contracts and relaxes to control the size of the pupil and therefore the amount of light that enters
What is the lens?
A clear disc which is controlled by the ciliary muscles and suspensory ligaments. It focuses light rays in order to produce a clear image
What are suspensory ligaments and ciliary muscles?
Suspensory ligaments - sit either side of the lens and hold it in position
Ciliary muscles - attached to the suspensory ligaments and by contracting of relaxing, can position the lens
What is the sclera?
The white outer layer of the eye, it’s quite tough and strong so little damage can come to the eye
Why do you have a blind spot?
The optic nerve is attached to the retina, so there is a point on the retina where there are no light sensitive cells
What does the optic nerve do?
When sensors on the retina detect light, an electrical signal is emitted which travels up the optic nerve to the brain to be interpreted
What happens to the radial muscles in dim and bright light?
In bright light they relax so the pupil is smaller
In dim light they contract so the pupil gets bigger
What is accommodation?
When the lens changes shape to focus light
What do the ciliary muscles do to see distant and close objects?
Distance - the ciliary muscles relax which makes the suspensory ligaments to pull tight, making the lens go thin
Close - the ciliary muscles contract, slackening the suspensory ligaments so the lens becomes fat
Why does Myopia happen? (short sightedness)
The light focuses on front of the retina, so distant objects are blurry.
This can be because of a curved lens or the eyeball being too long
This can be fixed by wearing concave lens glasses to spread the light rays out so it focuses on the retina
Why does Hyperopia happen? (Long sightedness)
The light rays are focused behind the retina, so distant objects are in focus but near objects aren’t.
This could be because the lens is too flat or because the eyeball is too short
This can be treated by wearing convex lens glasses, bringing the light rays together so they focus on the retina
What is binocular vision and why is it important?
When animals have two eyes, this judges depth perception and how fast things are moving
