nervous system and eye Flashcards
what are the conditions inside your body known as
internal environment
what is homeostasis
homeostasis is the regulation of the conditions inside your body to maintain a stable internal environment in response to internal or external changes
why does your body regulate the internal conditions in your cells
your body regulates the internal conditions in your cells to maintain an optimum temperature for your cells to work properly in response to changes externally or internally
why is it important for your body to respond to changes from the internal or external environment
so your body can maintain an optimum temperature for your cellular enzymes
what conditions are kept controlled in your body
body temperature
water content
blood glucose levels
what does your body use to detect and respond
automatic control system (nervous system)
what does your receptors do
They detect changes from the internal or external environment
what are the changes to your internal and external environment known as
stimuli
what does your coordination centre do and example of it
Your coordination centre receive and process information from your receptors and then sends out signal and coordinates these responses of the body
examples brain and spinal cord
what does your effectors do
these carry out the responses of the stimulus and restore the condition of your body back to its optimum temperature
what sub cellular cells do receptors have and where are they found
receptors have a nucleus, cell membrane and cytoplasm
they are found in clusters in sensory organs e.g eyes
how does your nervous system works
1) your receptors detect a change of stimulus then sends out signals along the sensory neuron to the CNS (central nervous system)
2) your CNS then coordinates the responses of the instruction and sends out signals along your motor neuron to effector organs
3) your effector organs then carry out these responses restoring back the conditions of your body
what are neurons
neurons are clusters of nerves
what is the independent (I) dependent (D) and control (V) variable of the reaction time experiment REQUIRED PRACTICAL
I- person having their reaction time tested
D- reaction time
C - starting distance between ruler and finger, conditions of the room and what we measure the ruler to get our recording
steps of reaction time experiment REQUIRED PRACTICAL
1) student 1 sits with a good posture and places their dominant hand over the edge of the table
2) student 2 then places the ruler vertically above students 1 thumb and first finger
3) student 2 then drops the ruler at a random time and student 1 catches it
4) student 2 then records the measurement of the ruler from the level of the thumb
5) the test is repeated several times then a mean is calculated
what are reflexes
automatic responses
what are reflexes used for
- to avoid danger
- help with your basic body functions e.g breathing
- they help do unconscious act which do not require the conscious part of the brain
how are reflexes so fast
- they do not use the conscious part of the brain so the result time between the stimulus and the effector organ is as short as possible
how does your reflex arc work
1) skin receptors detect a stimulus and send electrical impulses along the sensory neuron
2) the sensory neuros then releases chemicals which diffuses along the synapse to the relay neuron ad this starts a new electrical impulse
3) the electrical impulse continues to travel along the relay neuron until it meets another synapse, which then the relay neuron release chemicals which diffuses across the synapse to the motor neuron starting another new electrical impulse
4) the electrical impulse travels along the motor neuron until it reaches the last synapse which it then releases chemical which diffuse across the synapse to the effector
where is the relay neuron found
spinal cord
what are synapses
their gaps between neurons
what are the disadvantages of synapses
- they slow down electrical impulses, delaying the reflex arc
how do synapses work
1) an electrical impulse is sent to the pre synaptic neuron
2) this cause the neuron vesicle to move towards the membrane of the pre synaptic neuron
3) neuron transmitters (chemicals) then diffuse across the synapse and attach onto the receptors of the post synaptic neuron
4) if enough neuron transmitters attaches onto the receptors it generates a new electrical impulse into the post synaptic neuron
5) some neuron transmitters are recycled back to the post synaptic neuron
where is the brain found and what is it surrounded by
- it is found inside a skull and is surrounded by a protective membrane called meninges
what does the cerebral cortex do
- it is the conscious part of the brain and controls memory language and intelligence
what does the cerebellum do
it controls the muscle activity and balance
what does the medulla do
this is the unconscious part of the brain and controls things like breathing
what does your hypothalamus do
it control your body temperture
what does your pituitary gland do
produces many chemicals
what do MRI scans do and what does it stand for
Magnetic Resonance Imagery
they doctors see the part of the brain that is affective and help scientist link the affected area to the function of the body that is not working
why is it hard to treat the brain
- drugs do not always reach the brain due to the membrane surrounding it
- it hard to perform surgery on the brain as we don’t fully understand it and surgeons do not want to cause any unintended damage to the brain
except MRI scans how else can we see what part of the brain is affective
- by electrically stimulating the brain by zapping it with an electrode at different parts of the brain and seeing what it does
characteristics of the sclera
its the white outer layer of the eye
relatively strong and tough so it cannot be easily damage
has a transparent layer at the front of the eye called the cornea
characteristics of the cornea
- it has a curved surface so it can change the change direction of the light rays entering the eye so it focuses on the retina
what is the pupil
- its a hole that lets light in
what is the iris
- a muscle that contracts or relaxes so the pupil can control the amount of light entering the eye and determines your eye colour
what happens to your pupils in dark and bright light
- in a dim light your pupils get larger so as much light as possible can enter
- in bright light your pupils get smaller as too much light can damage your light sensitive cells
what does the lens do and what is it
- your lens is a clear disc held by your ciliary muscles and your suspensory ligaments
- changes the direction of light to produce a clear image on the retina
- changes shape so you can focus on far and distant
what does your optic nerve do
- sends impulses generated by the light sensitive cells to the brain so you can produce an image
what is the fovea
- its the part of the eye where light focuses on
what is the aqueous humour and what does it
- transparent thick jelly which refracts light
what does your ciliary muscles do
- determines how much light your lens refract as it changes the shape of your lens
how does light pass through your eye
- by refraction
what happens if light focuses behind or infront of the retina
the image would be blurred
what do your circular muscles and radial muscles do if its bright
circular muscles
contract to squeeze the pupil smaller
radial muscles
relax to stretch the pupil larger
what do your circular muscles and radial muscles do if its dark
circular muscles
relax
radial muscles contract to make pupil shorter and pulling it open
what happens to the light when your looking at an object that is close
- the light diverges strongly when it reaches your eye
what happens to the light when your looking at an object that is far away
- the light travels parallel to your eye
what happens to your ciliary muscles, suspensory ligaments and your lens when you focus on distant objects
- your ciliary muscles relax making your suspensory ligaments get pulled tightly making your lens thinner so the light entering your eye refracts slightly
what happens to your ciliary muscles, suspensory ligaments and your lens when you focus on close objects
- your ciliary muscles contract and the suspensory ligaments loosen, this causes the lens get thicker and fatter so the light entering your eye refracts strongly
what is myopia
short sightedness ( so long distance appears blurry)
what is hyperopia
long sightedness ( so short distance appears blurry)
how can myopia be treated
with glasses with concave lens so it can spread out the light before it enters the eye
how can hyperopia be treated
with glasses with convex lens so it can bring the light rays closer together before it enters the eye
what causes myopia
the eye being too long or the cornea being to curved so images on the retina appear blurry
what causes hyperopia
they eye being too short or the cornea being to flat so the cornea cant refract
where does the light focus in myopia
in front the retina
where does the light focus in hyperopia
behind the retina
what is accomodation
the process where your lens change shape so that you can focus on objects that are far or close
advantages of contact lenses
- less visible - this makes it easier for people who play sport and complete general activities
- hard contact lenses made from strong rigid material last long
- modern contact lenses are comfortable
disadvantages of contact lenses
- hard contact lenses are uncomfortable
- modern contact lenses don’t last long
- contact lenses have to be removed before bed and sterilised
advantages of laser surgery
- can help with hyperopia and myopia
disadvantages of laser surgery
- requires surgery
how can laser surgery help with myopia
- reduces the thickness of the cornea so the light can refract less
how can laser surgery help with hyperopia
- can curve the cornea more so the light is refracted more efficiently
advantages of replacement lens
- your lens can be replaced to stop visual defects permanently by adding a new lens and leaving your natural lens in place or replacing your natural lens with artificial lens
disadvantages of replacement lens
- can cause cataracts (where your vison gets blurry) ,infections or damage to the retina
