B3.1 Flashcards
Okay so explain in detail what different things of a nervous system are, and say how something happens…
What is basic function of nervous system
What is the CNS mad out of
What are effectors
Nervous system coordinates a response to a change in external environment
1) A change in environment, stimulus, happens. This could be something like light or pressure or smell or taste etc.
2) Receptor cells in a part of a body detect this stimulus
3) receptors send an electrical impulse (message) to the spinal cord via a SENSORY NEURONE, which then goes to the brain. The SPINAL CORD AND THE BRAIN MAKE UP THE CNS.
4) The brain coordinates a response and and sends another electrical impulse , back down the spine and via the MOTOR NEURONE of something to effectors.
5) effectors can be MUSCLES OR GLANDS. These carry out what the brain said…
What is the steps involved ina coordinated response and how long does this take?
Stimulus —> sreceptor cells—> sensory neuruones —> spine —> brain (response)—> spine —> Motor neurone —> effectors (muscle or gland)
Takes 0.7 seconds roughly.
What about a reflex arc? How is it different to a normal response?
How long does this take ? What does a relay neurone do?
A reflex arc skips going to the CNS for a response- it happens automatically. They din’t use conscious brain… some examples like sunshine in your pupils, cutting your hand on broken glass, sand in your eye, exposure to stressful situation adrenaline released… often the stimulus is what happens not pain- you anticipate because if you waited for pain it would be too late.
Stimulus—> sensory neurone—> spinal cord (relay neurone)—> motor neurone—> effectors—> response
0.2 seconds
Hwhatis the connection between two neueones? How does messages still go through?
Why do we need them when one big neurone line is more efficient?
Synapse is the gap between two neueones.
It works like
1) electrical impulse goes to end of neurone, triggering release of chemical neurotransmitters.
2) These diffuse across the Gap
3) These then bind with receptor molecules at the start of next neurone. Based on the amount released , will determine what happens
4) once this happens, a new electrical impulse is started. This is how an electrical impulse can be conducted across a gap…
We need synapses in case we need to change the signs along sent on case of emergency. For example, if you cross road and car come, you need to be able to stop walking and move. Synapses have ability to stop signal going through.
How are neurones adapted for their function?
- Neueones have branched endings called DENDRITES, which a low them to connect with other neuerones.
- The axons of neurones (square part) are surrounded by a fat MYLEIN SHEATH. This acts like an electrical insulator, so the electrical impulse is speeded up.
- generally neurones are long- allowing for efficiency as longer ones are faster then a lot of short ones…
How to investigate reaction time? And what conditions effect it?
What formula do we use to calculate time (physics…)
Use ruler drop test.
1) drop a ruler from a certain pint and measure the distance the ruler falls before it is caught. You can then use equation D= 1/2AxT^2, and rearrange for time to find the reaction time. (Acceleration is 9.81 due to gravity.)
You control things like height you drop it at, finger hand position, whether it is sting or weak hand, mass type of ruler, and TIME FOLLOWING CAFFEINE INTAKE.
- This is important because you can investigate how caffeine effects reaction time (faster) so it has to be controlled.
- you can also investigate how a distraction affects it
- how are affects it. Just change these variables up.
Just in case explain how a motor neuen one and sensory neurone look like
Sensory neurone- has its axons straight line with nucleus half way through. Random branch at the end
Motor Neurone big branch at the start with nucleus in, then axons and same random branch at the end,
Wheat are the different things in an eye? How are images formed in the eye?
Also what once the image is focussed on the retina, what happens after that?
1) Light is refracted by the cornea. This provides MOST of the focus for the retina of the incoming light.
2) Light then passes through the pupil, a hole which the size of this is controlled by the iris….
3) the Light then gets refracted even more by the lens. Based on near or far objects, the shape of the lens has to change to refract the light on the SURFACE of the retina. This happens with the combination of the ciliary muscles and suspense Roy ligament contracting / relaxing.
4) a clear image is then focussed on the retina.
5) LIGHT SENSITIVE CELLS CALLED PHOTORECEPTORS THEN produce a nervous impulse that is sent down the optic nerve to the brain, which interpreted it is an image.
How does the lens ( ciliary muscles and suspensory ligaments) adjust to look at near and far objects?
(Accommodation)
To understand this remember fatter lens (more convex) refracts light more, whereas thinner lens (less convex) does it less.
Light from a distant object generally comes in parallel lines. This means the lens doesn’t have to refract it that much, so a thinner lens is used. To make it thinner the suspensory ligament must contract to stretch it, and so if the suspensory ligament contacts the ciliary muscles must relax, and this makes the lens thinner so the light is focused correctly on the retina.
However if light is coming from a distant object, the light comes in diagonal lines, which need to be REFRACTED MORE then the long distance. A more fatter (convex) lens is needed therefore. The ciliary muscles contract this time, to make the suspensory ligaments relax, allowing the lens to become more fatter, and refract the light onto the retina clearly….
More on the photoreceptors cells- what are they actually?
Two types = rod cells, and cone cells
Rod cells are sensitive to light and allow you to see in low light levels, and are not sensitive to colour at all
Cone cells: these respond to colour : there are 3 CONE CELLS FOR RED GREEN BLUE light, which makes the other colours.
what is colour blindness
Who is it most common in wand what is the most common form?
Is there a cure?
Colour blindness is when some people can’t tell a difference between colours. The most common is red- green colour blindness- which means people can’t distinguish between them because one of these cones aren’t working properly.
Most common in men- genetically inherited condition.
Not a real cure, but so,e tinted glasses can help…
How does the eye adapt to see in dim light?
The pupil constricts to allow less light in the eye, so that the rod and cone cells don’t get damaged in intense light.
However when there is low level of light, the pupil dilates (gets bigger) and lets more light In to see more, particularly for the rod cells…
What is short and long sightedness? What are the scientific names for them?
Long sightedness means you can only focus on longer objects, and short means you can only see short, the other one does not form an image on your eye properly…
For long sightedness = HYPEROPIA
For short sightedness = myopia
Why do people have short sightedness. As a result, what adjustments need to be made for this problem?
How do we correct short sightedness
People with short sightedness lens are TOO STRONG, or the eyeball is too LONG.
- As a result, when focussing on distant objects, where not much refraction is needed, too much refraction (and bending) happens causing the image to be formed just before the retina… BUT NOT ON IT= BLURRED
- THEREFORE, a lens which bends the light outwards first, so the powerful lens can then bend it inwards , but this time on the retina is needed, this lens is a CONAVE LENS. (Lens that is shaped inwards).
Light bends outwards, string lens bends it inwards again… fixed
Must remember al, this time the cornea still refracts light a bit in both cases , but this is taken account for when choosing a lens…)
Why do people have long sightedness? How do we correct it and what lens we need?
People who can only see distant objects, where not much refraction is ended, have lens which are too WEAK or the eyeball being too SHORT. Think about it, when light coming from short object, it needs to be refracted more, but because the lens is weak/ eye short, the light can’t be refracted enough, therefore the image is formed beyond the retina and so it is BLURRED.
To fix this we need a lens that bends the light inwards first, so that the weak lens doesn’t have to bend it that much to correct it. This lens is a CONVEX LENS.
(Must remember al, this time the cornea still refracts light a bit in both cases , but this is taken account for when choosing a lens…)
