Ears and eyes Flashcards
What is the optic nerve?
A sensory nerve.
What is the oculomotor nerve?
The output nerve from the brain back to the eye.
What happens if the ciliary muscle in the eye is contracted?
releases tension on the zonular fibres, which allows lens to return to a spherical shape
Focus on close objects
What happens if the ciliary muscle is relaxed?
zonular fibres pull lens into flattened, oval shape
Focus on distant objects
What is shortsightedness?
When the eyeball is too long and the lens is too rounded
can’t focus on far objects.
What is longsightedness?
The eyeball is slightly too flat.
Can’t focus on near objects
What is cataracts?
When the lens becomes cloudy.
What is glycoma?
Too much pressure inside the eyeball.
can damage the retina
What are the two possible causes for glycoma?
Too much fluid (aqueous humour) may be being produced or the draining process may not be occurring correctly.
What are the two treatments for glycoma?
Prostaglandin analogues to increase the drainage or beta-blockers to decrease production of the fluid.
What do rods do?
Perceive light and dark.
sensitive and respond well to low light
What do cones do?
Perceive red/green/blue light.
respond to bright light
How are neurones in the eye different to other neurones?
They constantly fire action potentials in the dark - a silent neurone is firing action potentials.
How does light change the way the neurones act?
Light causes the molecules in redopsin receptors to change shape and the the cell becomes less depolarised and is less likely to fire action potentials when light is present.
What happens to rods if they are constantly exposed to light?
They become bleached.
How is the input from the eyes to the brain different to the body?
The right side of the brain receives a little bit of input from the right eye and vice versa for the left side due to the overlap of the left and right visual fields.
Why can you not see colour in the dark?
Cones can only function in bright light conditions.
How does colourblindness arise?
The wavelengths of the different cones overlap as the cones are slightly different to normal.
What is the difference between the primary visual cortex and the secondary visual cortex?
The primary receives input from the eyes and the secondary interpret what our eyes are telling us to see.
What does the frontal lobe association area/cortex do?
Interprets our emotion from the images we see and can tell us whether something should be feared.
What does the chochlea do?
Turns vibrations into sound. The fluid in the cochlea vibrates and hair cells respond to the sound coming into the ear.
What is the cochlea?
The fluid filled inner ear.
What are the semi-circular canals of the vestibular involved in?
Balance.
How is the sensation of dizziness created?
When spinning around, the fluid in the vestibular continues moving which creates the sensation.
