The brain + THE EYE Flashcards
Purpose of the brain
The brain controls complex behaviour (e.g. language)
What is the brain made up of
The brain controls complex behaviour (e.g. language)
how does the brain do this
It is made of billions of
interconnected neurones and has different regions that carry out
different functions.
parts of the brain
cerebral cortex
medulla
cerebellum
Purpose of cerebral cortex
The highly folded, outer part of the brain
It is responsible for/its functions include language, intelligence, memory and consciousness
Purpose of the cerebellum
The cerebellum controls our balance and coordinates our movements (muscle coordination)
purpose of the medulla
The medulla controls unconscious activities for example heart rate and breathing rate
label parts of the brain
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Describe how methods/ways scientists use to investigate brain function
- Many scientists look at patients who have suffered brain damage
By looking to see where the damage has taken place, they can try to link that part of the brain to its function
- Different parts of the brain can be electrically stimulated and look at the effects on the person behaviour
That allows us to narrow down specific regions to their functions - MRI scanning can be used to look at which parts of the brain are most active during different activities
E.g. when a person is looking at images, we see greater activity in the part of the brain responsible for image processing, we see greater activity in the part of the brain responsible for image processing
spec
Neuroscientists have been able to map the regions of the
brain to particular functions by studying patients with brain damage,
electrically stimulating different parts of the brain and using MRI
scanning techniques
explain some of the difficulties of
investigating brain function and treating brain damage and disease
studying the brain is extremely difficult
It is also difficult to treat brain damage or brain diseases
The brain is protected by the skull so it is very tricky to access
The structures of the brain are extremely complex. So it is difficult to work out exactly which parts of the brain carry out specific functions
The brain is extremely delicate and easy to damage
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spec The complexity and delicacy of the brain makes
investigating and treating brain disorders very difficult
What is the eye
The eye is a sense organ containing receptors sensitive to light intensity and colour (of light)
Name different parts of the eye
Pupil
retina
* optic nerve
* sclera
* cornea
* iris
* ciliary muscles
* suspensory ligaments.
Label diffrerent parts of the eye
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What is the function of the cornea
The cornea is the transparent outer layer found at the front of the eye
Purpose: To refract light rays as they enter the eye
(to start the focussing of the light rays)
cornea: transparent area at front of eyeball that admits light, curved surface to help
focus light coming into the eye on retina;
What is the function of the iris
The iris is the coloured part of the eye
The function of the iris is to control the size of the pupil and therefore how much light enters the eye (the iris contains muscles that allow it to control the diameter of the pupil - and therefore how much light enters the eye
how does the iris control the size of the pupil (and how much light enters the eye)
(the iris contains muscles that allow it to control the diameter of the pupil - and therefore how much light enters the eye
Function of the lens
The function of the lens is to focus the light rays onto the back of the eye
(allows us to focus on near or distant objects)
Describe one key feature of the lens
One key feature of the les is that it can change shape, allowing it to focus on distant or near objects. This is called accommodation
Describe the function of the retina
The back of the eye is called the retina
Contains receptor cells for light. These receptor cells allow us to detect light intensity and light colour (receptor cells sensitive to light intensity and colour)
Describe the function of the optic nerve
Carries impulses from the receptors on the retina to the brain
Describe how the eye works - describe how the eye detects light
Light rays pass through the transparent front of the eye - called the cornea
The function of the cornea is to refract light rays as they enter the eye
(to start the focussing of the light rays)
The light rays pass through the pupil in the centre of the iris
The iris is the coloured part of the eye
Light rays now pass through the lens. The function of the lens is to focus the light rays onto the back of the eye
Lens changes shape to focus light onto retina
The shape of the lens is controlled by the ciliary muscles and suspensory ligaments
One key feature of the lens is that it can its change shape, allowing the eye to focus on distance or near objects. This is called accommodation
The light rays are now focussed onto the back of the eye. This is called the retina.
The retina contains receptor cells for light
These receptor cells allow us to detect light intensity and light colour (receptor cells sensitive to light intensity and colour)
The receptor cells in the retina now send electrical impulses down the optic nerve to the brain
What is the sclera and its function
The white part of the eye is called the sclera
This tough outer structure protects the eye
What is the shape of the lens controlled by
The shape of the lens is controlled by the ciliary muscles and suspensory ligaments
What two parts work with the lens
The ciliary muscles and the suspensory ligaments work with the lens
What do the ciliary muscles and suspensory ligaments allow the eye to do
Together the ciliary muscles and the suspensory ligaments allow the eye to focus on distant or near objects
What is the pupil
The pupil is the space in the centre of the iris which light passes through.
The pupil allows light rays into the eye
Explain how the eye adapts to dim light
If you enter a dark room, the amount of light entering the eye is now low
This drop in light intensity is sensed by light receptors in the retina and these send electrical impulses to the brain
The brain then sends electrical impulses to specific muscles in the iris.
These muscles contract, causing the pupil to become larger
This now allows more light to enter the eye
This is a reflex action because it does not involve the conscious part of the brain
______________
pupils dilated
in dim light
because circular muscles (in iris) relax
(and) radial muscles contract
This now allows more light to enter the eye (pupils are wider
Explain how the eye adapts to bright light
We can see the opposite effect if we walk into a bright room. In this case, the reflex causes the pupil to become smaller.
This now reduces the amount of light entering the eye and protects it from damage (very bright light can damage the retina)
_______________
If you enter a bright room, the amount of light entering the eye is now hight
This increase in light intensity is sensed by light receptors in the retina and these send electrical impulses to the brain
The brain then sends electrical impulses to specific muscles in the iris.
These muscles relax, causing the pupil to become smaller
This now allows less light to enter the eye
In this case, the reflex causes the pupil to become smaller.
This now reduces the amount of light entering the eye and protects it from damage (very bright light can damage the retina)
This is a reflex action because it does not involve the conscious part of the brain
__________
pupils constrict
in bright light
because circular muscles (in iris) constrict
(and) radial muscles relax
this now allows less light to enter the eye (pupils are smaller)
Explain why this change of shape of pupils depending on differing conditions is a reflex action
This is a reflex action because it does not involve the conscious part of the brain
What is a lot of the focussing carried out by
A lot of the focussing is carried out by the cornea (but the cornea is a fixed focus)
What is the rest of the focussing carried out by
The rest of the focussing is carried out by the lens
How does the lens allow us to focus on near and distant objects
The shape of the lens can change to allow us to focus on near and distant objects
What is accommodation
The ability to change the shape of the lens to focus on near or distant objects
What is the lens surrounded by - how is this structure connected to the lens
The lens is surrounded by a circular muscle called the ciliary muscle
This is connected to the lens by fibres which are called suspensory ligaments
How can the ciliary muscle change the thickness of the lens
By contracting or relaxing, the ciliary muscle can change the thickness of the lens
What happens when the ciliary muscle contracts
When the ciliary muscle contracts, the suspensory ligaments loosen (relax)
The lens is now thicker and refracts light rays more strongly
What happens when the ciliary muscle relaxes
When the ciliary muscle relaxes, the suspensory ligaments are pulled tight (contract)
The lens is now pulled thin and only slightly refracts light rays
Explain how the eye accommodates to focus on distant objects
Light from distant objects needs to be focussed only a relatively small amount
When the ciliary muscle relaxes, the suspensory ligaments are pulled tight (contract)
The lens is now pulled thin
Because the lens is thin, the light rays are only slightly reflected
The light rays are now focussed to a point on the retina
Explain how the eye accommodates to focus on near objects
Light from near objects need to be focussed a large amount
When the ciliary muscle contracts, this causes the suspensory ligaments loosen (relax)
The lens is now thicker and refracts light rays more strongly
The light rays are now focussed to a point on the retina
What does it mean when a person is short-sighted or longsighted
In these people the light rays do not focus correctly on the retina
Describe what longsightedness is and how it can be caused
Long sightedness is also called hyperopia
People with long sightedness have no problem at all focussing on distant objects but they cannot focus on nearby objects
In many cases of longsightedness the eye ball is too short so the light is focused at a point behind the retina
However in some cases, especially in the elderly, the lens becomes less elastic. In this case, the lens cannot become thick enough to focus on near objects
Describe how long sightedness are treated
Long sightedness can be treated by using glasses with a convex lens
These partially focus the light before it enters the eye
This leads to the light rays now being able to focus to a point on the retina
Draw the diagram for people with long sightedness
Draw the diagram with people with glasses to treat long sightedness to illustrate how they work
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Describe what short sightedness is
Short sightedness is also called myopia
People with short sight can focus on nearby objects but they cannot focus on distant objects
In people with short sight, the eyeball can be too long, so the light is focused at a point in front of the retina
Short sightedness can also be caused when the lens is too thick
The light is focussed in front of the retina
How can short sightedness be treated
Short sightedness can be treated using glasses with concave lenses to partially unfocus the light before it enters the eye
Draw the diagram for people with short sightedness
Draw the diagram with people with glasses to treat short sightedness to illustrate how they work
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Alternatives to using glasses
People can also use hard or soft contact lenses
These lenses sit on the eyeball and they refract light in the same way as glasses
laser surgery can be used to change the shape of the cornea (so it refracts the light to a greater or lesser extent)
a replacement lens in
the eye (using an artificial lens)
