b10 - the nervous system Flashcards
homeostasis
the maintenance of a stable internal environment in response to changes in environment
stimulus
a change in your environment that may require a response
examples of stimuli
- temperature
- light
- sound
- chemical
- position
- pain
- pressure
- touch
receptors
special cells that detect changes in the internal or external environment
coordination centres
- areas that receive and process information from the receptors
- they then send out signals to coordinate the response of the body
what does the CNS consist of?
the brain and the spinal cord
effectors
- muscle or gland that carries out the response to the stimulus
- the response will restore the conditions to their optimum levels
what does the human control system contain?
- receptors
- coordination centres
- effectors
what is the purpose of the central nervous system?
enables humans to react to their surroundings and to coordinate their behaviour
process of the body responding to stimuli
stimulus > receptor generates impulse after detecting a change in the environment > sensory neurone conducts impulses to spinal cord (CNS) > passes synapses between neurones > chemical stimulates
why does homeostasis take place?
- an optimum environment is maintained to prevent the denaturing of enzymes
- denaturing reduces the enzyme’s ability to catalyse metabolic reactions
which internal conditions need to be regulated?
- blood sugar
- water levels
- carbon dioxide levels
- urea conc (in urine)
- internal body temperature
which type of neurone carries impulses to the central nervous system?
sensory neurone
which type of neurone carries the impulses away from the central nervous system
motor neurone
one factor that may affect reaction time
energy drinks/caffeine/exercise
reflex actions
automatic and rapid reactions that do not require conscious parts of the brain
where is the relay neurone found in the reflex arc?
spinal cord
reflex pathway
stimulus > receptor > sensory neurone > relay neurone > motor neurone > effector > response
synapses
the physical gap between neurones
how is information passed through the synapse
via neurotransmitters
neurotransmitters
chemicals that are released which travel through the synapse and bind to the receptor cells in the next neurone
cerebral cortex
region in the brain which controls conscious activity, intelligence, memory and language
cerebellum
region that co-ordinates muscle activity and balance
medulla
region that controls automatic, unconscious activity
name a method that scientists use to find out the functions of each part of the brain
- studying brain damage patients
- use of electrical impulses to stimulate the brain
- MRI scans
function of the sclera
white outer layer to protect the eyeball
function of the cornea
- transparent area at the front of the eyeball
- allows light into the eye and then refracts/focuses it
function of the iris
- controls the size of the pupil
- can contract and relax to change the size of the pupil so as to control the amount of light focused on the retina
hypothalamus
coordination centre in the brain
pituitary gland
produces many different hormones (like ADH), which play a big part in coordinating and controlling body systems
advantages of MRI
- non invasive
- doesn’t use ionic radiation
- produces detailed images of the nervous system
disadvantages of MRI
- claustrophobia - requires you to be in a small space for a long period of time
- takes a while to acquire results
- expensive
lens
- held in place by the ciliary muscles and suspensory ligaments
- fine tunes the focus of the light on the retina to produce a clear image
function of the retina
filled with receptor cells which are sensitive to both the brightness and the colour of the light
two main types of light receptor cells
rods and cones
rods
sensitive to light intensity
cones
produce colour vision
what do the light sensitive cells do?
they send impulses to the brain along sensory neurones in the optic nerve
optic nerve
sends impulses between the eye and the brain
process of light being focused
light > cornea > bent onto the lens > falls on the retina > the light is focused by the process of refraction by the cornea
process of the refraction of light
light refracted by the cornea and lens > cornea always refracts the same amount of light > the shape of the lens change to alter the amount of refraction > contraction of the ciliary muscles
what happens to the pupils in bright light?
it constricts (becomes smaller) so as to limit the amount of light that enters the eye
what happens to the pupil in dim light/darkness?
it dilates (becomes much bigger) because it needs to take in as much light as possible
suspensory ligaments
a ring of fibres that connect the ciliary muscles to the lens
ciliary muscles
a ring of smooth muscle that changes the shape of the lens to focus light
pupil
a hole in the centre of the iris through which light passes to reach the retina
accommodation
the process of the lens changing shape to focus on an object as its distance from the eye changes - this is done by the ciliary muscles and the suspensory ligaments
focusing on a close object
- contraction of the ciliary muscles
- loosening of the suspensory ligaments
- causing the lens to become rounder and thicker
- results in significant refraction
focusing on a far object
- relaxation of the ciliary muscles
- tightening of the suspensory ligaments
- lens becomes flatter and thinner
- results in less refraction
hyperopia
long-sightedness
- rays of light focus BEHIND the retina
myopia
short-sightedness
- rays of light focus IN FRONT of the retina
reasons for myopia happening
lens too curved, long eyeball
treatment options for myopia and hyperopia
contact lenses/laser eye surgery/glasses
