B1.6/7 - The Nervous System & The eye Flashcards
What detects light in our eyes?
Receptors
How does our brain process what we see with our eyes?
Receptors detect light and change this light into electrical impulses. The impulses pass along the optic nerve into the brain.
Animals with both eyes facing forwards have
_______ vision.
Binocular
What is one disadvantage of binocular vision?
Animals with binocular vision do not have a very wide field of view.
Why may binocular vision be good for predators when hunting?
Since both eyes focus on the same thing, this allows them to judge distance accurately and focus well.
Animals with eyes on each side of their head have ________ vision.
Monocular
State two advantages of animals with monocular vision
- They have a much wider field of view
- They can see all around and notice predators in time to run.
What sort of vision do humans have? And what does this allow them to do well?
Binocular vision. This allows humans to judge distance accurately and focus on objects.
How does the human brain judge distance?
To judge distance the brain compares the images from each eye. If the images are very similar the brain knows you are looking at something from distance and vice versa.
You can test this. Look at something from a close distance. Cover one eye and then the other. You can see the object from a different view.
What is it called when the lens in the eye has to change shape when focusing on a near or distant object?
Accomodation
What is a symptom of red-green colour blindness and how can someone get this? And why does this symptom occur?
Red-green colour blindness is an inherited condition. It is when someone cannot tell the difference between the colour red and green. This happens because they do not have certain specialised cells in the retina.
What is the retina?
A layer at the back of the eyeball that contains cells sensitive to light, which trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.
What are the impacts to people with long sight?
People with long sight can see things in the distance clearly, but cannot focus on thing close by clearly.
What are the impacts to people with short sight?
People with short sight can see things close by clearly, but cannot focus on things in the distance clearly.
In short sight the eyeball is too (i)_____. In long sight the eyeball is too (ii)____.
(i) long
(ii) short
Why are distant objects blurred to people with short sight?
Distant objects are blurred to people with short sight because the light rays meet in front of the retina instead of on it. This causes the final image to become blurred.
How do lenses in glasses correct short sight?
Lenses in glasses for a person with short sight are called diverging lenses. Lenses in glasses for a person with long sight are called converging lenses.
Diverging lenses in glasses for people with short sight correct an image as it bends light rays outwards before they enter the eye. This causes the light rays to meet on the retina instead of in front of it, meaning a clear final image can be seen,
What is a stimuli?
A stimuli is a change in the environment or in your body.
Why do we need to be able to respond to changes in the environment or our bodies?
If you could nor respond to or detect a stimuli you would not be able to find food or avoid danger. E.g withdrawing your hand from a hot object.
What is the nervous system?
The network of nerve cells and fibres which transmits nerve impulses between parts of the body
There are two main parts of the nervous system and what do these include?
- The Central Nervous System (CNS) - the spinal cord and brain
- The peripheral Nervous System - nerves taking information from sense organs into the CNS, and from the CNS to effectors (muscles or glands)
What is an effector?
An effector is any part of the body that produces the response to a stimuli. These are usually glands or muscles.
What are receptors cells?
Receptors cells are special cells adapted to detect stimuli. Like most animal cells, they have a nucleus, cell membrane and cytoplasm.
Name the 5 human sense organs and what information do they detect?
Skin - pressure, temperature, touch and pain Nose - chemicals in air (smell) Tongue - chemicals in food (taste) Eyes - light (sight) Ears - sound (hearing), balance
How does information from the receptors pass as electrical impulses to the brain?
They travel along nerve cells called neurones, to the brain. The brain then coordinates the response.
What is a voluntary response?
A voluntary response is for example when you hear a song on the radio and decide whether to turn up the radio, turn it off or leave it as it is.
Sometimes you need to respond to a potentially dangerous situation very quickly. For example, you may need to withdraw your hand from a hot object before you get burnt. There is no time to think so the brain is not involved. Instead the response is coordinated by another part of the CNS, the spinal cord. These responses are fast, automatic and protective. What are they called?
Reflex actions
Describe the order of the reflex arc pathway
Stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
What is a neurone?
A specialized cell transmitting nerve impulses; a nerve cell.
In the situation of a pin prick, what would the effector be according to the reflex arc pathway?
The effector would be the finger muscle as this is what pulls your hand away from the prick.
What is a synapse?
a junction between two nerve cells, consisting of a tiny gap across which information travels from neurone to another.
In terms of a muscle and gland being an effector, how would they respond.
Muscle: A muscle responds by contracting.
Gland : A gland responds by secreting chemical substances.
Name two example of a reflex action
- Withdrawing a hand from a hot plate
- Withdrawing a hand from a pin
