B1d Flashcards
How do animals detect changes in their environment (stimulus)?
When you detect a change in your environment (a stimulus) your sensory neurones carry the information from receptors to the CNS. The CNS then sends information to an effector (muscle or gland) along a motor neurone. The effector then responds accordingly.
What are the main parts of the eye?
Cornea Iris Pupils Lens Retina Optic Nerve Blind Spot
What is the function of the main parts of the eye?
Cornea - Refracts light into the eye
Iris - Controls how much light enters the pupil
Lens - Refracts light, focusing it on the retina
Retina - The light sensitive part and it’s covered in receptors called rods and cones, which detect light
Optic Nerve - Carries impulses from the receptors to the brain
What is the pathway of light through the eyeball?
Refracted by the cornea and lens and brought to focus on the retina.
How does they eye focus light (accommodation) from near and distant objects?
The lens is elastic, so the eye can focus light by changing the shape of the lens - this is known as accommodation.
To look at distant objects:
1) The ciliary muscles relaxes, which allows the suspensory ligaments to pull tight.
2) This pulls the lens into a less rounded shape so light is refracted less.
To look at close objects:
1) The ciliary muscle contracts, which slackens the suspensory ligaments.
2) The lens becomes a more rounded shape, so light is refracted more.
What are the advantages and disadvantages of monocular vision?
Wider field of view but poorer judgement of distance.
What are the advantages and disadvantages of binocular vision?
Narrower field of view but better judgement of distance.
How does binocular vision help to judge distances?
When you look at an object, your brain compares the images seen by each eye. The more similarities between the images, the further away the object.
What are the main problems in vision?
Long sighted
Short sighted
Red- green colour blindness
What is long sightedness caused by?
Long sighted people are unable to focus on near objects. This occurs when the lens is the wrong shape and doesn’t bend the light enough or they eyeball is too short. The images of near objects are brought into focus behind of the retina.
What is short sightedness caused by?
Short sighted people are unable to focus on distant objects. This occurs when the lens is the wrong shape and bends the light too much or the eyeball is too long. The images of distant objects are brought into focus in front of the retina.
What is the cause of red-green colour blindness?
A lack of specialised cone cells.
How can long and short sightedness be repaired?
Long sighted people can use glasses or contact lenses with a convex lens to correct it. Short sighted people can use glasses or contact lenses with a concave lens to correct it.
An alternative to glasses or contact lenses is to have corneal laser surgery.
What are the main parts of the nervous system?
The central nervous system - brain and spinal cord which coordinates information
The peripheral nervous system - consists of motor and sensory neurons that carry impulses from the receptors to the CNS, as well as impulses from the CNS to the effectors
What is a nerve impulse?
An electrical signal that is carried by nerve cells called neurones.
