B9.2 and B9.3 - The Eye and Hormones Flashcards
List the structures of the eye. [9]
Cornea
Iris
Pupil
Lens
Retina
Optic nerve
Ciliary muscles
Suspensory ligaments
Blind spot
What is the function of the cornea and where is it located?
To refract light. It is the transparent outer layer found at the front of the eye.
What is the function and of the iris?
To control how much light enters the pupil through contracting and relaxing the muscles.
What sort of organ is the eye?
Sense organ.
What are sense organs?
Groups of receptor cells that respons to specific stimuli.
What is the lens?
It is a large disc that changes shape to focus light on the retina.
What is the optic nerve?
A nerve that carries impulses from the receptors on the retina to the brain.
What is the area where the optic nerve located called and why?
The blind spot because there aren’t any light receptors.
What is the fovea?
A dip in the back on the retina that contains cones.
What are rods?
- Found in peripheral part of retina
- Very sensitive to light (work well in dim light)
- Gives info in black and white
What are cones?
- Mainly found in the fovea
- Less sensitive to light
- Three types which give info in red, green, and blue
What is the vitreous humour?
Jelly-like fluid in rear chamber of eye that maintains eye shape.
What are the suspensory ligaments?
Attach lens to ciliary body.
What is the pupil?
Circular opening for directing light to the lens.
What are the ciliary muscles.
Contains circular muscles that alter the shape of the lens during focusing.
What is the retina?
Photosensitve layer containing rods and cones.
What is the choroid?
Pigmented layer which absorbs light and prevents internal reflection, and contains blood vessels.
What is the conjunctiva?
Thin membrane protecting the cornea.
What is the aqueous humour?
Watery fluid that fills the front chamber of the eye.
What happens to the iris muscles in bright light?
- Circular muscles contract
- Radial muscles relax
- Pupil constricts
What happens to the iris muscles in low light?
- Circular muscles relax
- Radial muscles contract
- Pupil dilates
What happens when the eye focus on a distant object?
- Light needs to be bend less
- Ciliary muscles relax
- Suspensory ligaments become tight/taut
- Lens is long and thin
What happens when the eye focuses on a close object?
- Light is greatly bent
- Ciliary muscles contract
- Ligaments slacken
- Lens is short and fat
What is a reflex action?
A fast, automatic response to a stimuli.
What type of lens does the eye contain?
A convex lens.
What is a hormone?
A chemical substance produced by a gland, carried by the blood, which alters the activity of one or more specific target organs.
What produces adrenaline?
The adrenal glands.
What changes does adrenaline do to your body? [5]
- Increase breathing rate
- Increase pulse rate
- Dilates pupils
- Hightens sensitivity
- Increases blood glucose levels
Why does the pulse and breathing rate increase with adrenaline?
So glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, more quickly.
Why is blood glucose concentration increased with adrenaline?
To increase respiration in muscle cells.
Why are pupils dilated with adrenaline?
To allow as much light as possible to reach the retina so more info can be sent to the brain.
Which target organ releases glucose into the blood-stream as a result of the action of adrenaline?
Liver.
