Cells and control (2) Flashcards
What does the nervous system do?
protects organisms from harm by responding to changes in the environment.
How does the nervous system work?
Coordinating the communication between different parts of the organism
What is the nervous system made up of?
The brain, the spinal cord, neurones
What are effectors?
Muscles or glands that act in response to a change in the internal or external environment,
Why is the spinal cord important?
it, like the brain, coordinates the response of effectors to changes in the environment.
What do neurones (nerve cells) do?
carry electrical impulses between receptors, the CNS and effectors.
What are synapses?
gaps between neurones in which the nerve impulses must travel across
What do axons do?
Carry electrical impulses away from the cell body
What do dendrites do?
Carry electrical impulses towards the cell body
What are axons covered in?
a layer called myelin sheath which insulates the neuron.
Name three reflex actions
Blinking, dropping hot objects, sneezing.
How does the nervous system respond to stimuli
via a reflex arc
What are the different parts of a reflex arc?
stimulus, receptor, neurones, effector
Whats a stimulus?
any change in the environment to which the body needs to respond; detected by a receptor.
Whats a receptpr?
they detect a change in the environment and initiate a signaling process all over the body which is then picked up by a neurone.
What are the three types of neurone?
sensory (carries signals via electrical impulse), relay (relays the electrical impulse from the sensory neurone to the right motor neuron), Motor (carries the electrical impulse to an effector)
whats a response
an action that helps the organism to avoid a dangerous situation.
what is the brain
an organ that controls conscious and unconscious thoughts to keep an organism alive.
what are the three main parts of the brain?
cerebral hemispheres (responsible for all conscious thought), Medulla oblongata (responsible for unconscious activities) and the cerebellum (responsible for muscle coordination)
How does CT scanning work?
Many X-Rays are taken of the brain and a 3D image is then built. Brian tumors show as white blotches.
How do PET scans work?
using radioactive glucose, the amount of glucose being used by each part of the brain can be monitored. an image of brains activity is then made from this.
what happens if the spinal cord is cut
electrical impulses can no longer be sent to the brain. wires can partially re connect it, but it isn’t very effective.
how do you treat neurone damage
you can’t neurone damage is permanent and irreversible. they cant be replaced unlike other cells in the body.
what is a brain tumor?
lumps of dividing cancer cells, can block bloodflow to other parts of the brain
how can brain tumors be treated?
chemotherapy, radiotherapy or surgery.
what is the cornea
the frontal part of the eye that refracts light
what is the retina
full of receptor cells which are sensitive to brightness and colour of light.
what’s the sclera?
the white of the eye which is the opaque, protective outer layer
what is the optic nerve
the thing that transmits visual information from the retina to the brain.
what is the pupil
a hole in the centre of the iris, through which light passes to get to the retina.
what is the iris
controls the pupil diameter, therefore, the quantity of light reaching the retina.
what are the ciliary muscles
a ring of smooth muscles that can change the shape of the lens.
what are the suspensory ligaments
a ring of fibres that connect the ciliary muscles to the lens.
what is accommodation
the process in which the lens changes shape to focus on an object as the distance changes.
what are three ways to treat eye defects
glasses fitted with lenses that refract light (contact lenses and laser eye surgery too), synthetic lenses (for cataracts).
when does short sightedness happen?
when rays of light focus in front of the retina
when does long sightedness happen
when rays of light focus behind the retina
how is colour blindness caused?
it’s inherited and caused by the defects in the cone cells.
what do cone and rod cells do
detect light colour and light intensity respectively
what causes cataracts
build up of protein in the lens that makes the pupil cloudy.
