Homeostasis - the brain, eye and body temp 122-127 Flashcards
what are the different regions of the brain and their functions
4 points
1) cerebral cortex - responsible for consciousness, intelligence, memory and language
2) medulla - controls unconscious activities, like breathing, or heartbeat
3) cerebellum - responsible for muscle coordination
4) spinal cord
how can scientists study the brain
3 points
1) studying people with brain damage - if a part of the brain is damaged it can tell you a lot about what that part does
2) electrically stimulating the brain - this can be done by pushing a tiny into the tissue and giving it a small zap of electricity, by doing this it can give you an idea of what different parts do
3) MRI scans (magnetic resonance imaging scanner) - this can produce a detailed picture of the brain’s structure, scientists use it to find out what area of the brain is active when people are doing certain activities
how can investigating the brain be risky
2 points
1) the brain is very complex and delicate
2) so investigating it can cause physical damage or increased problems with brain function
what are the different parts of the eye and their function
6 points
1) sclera - the tough supporting wall
2) cornea - transparent outer layer at the front of the eye, it refracts light into the eye
3) iris - contains muscle that allow it to control the diameter of the pupil and therefore how much light enters the eye
4) lens - focuses light onto the retina (which contains receptor cells sensitive to light intensity and colour)
5) ciliary muscles and suspensory ligaments - controls the shape of the lens
6) optic nerve - carries impulses from receptors on the retina to the brain
draw and label an eye
pg 123 of bio book
how does the iris reflex adjust for different light levels
3 points
1) when light receptors in the eye detect very bright light, a reflex is triggered that makes the pupil smaller
2) the circular muscles in the iris contract and the radial muscles relax which reduces the amount of light that can enter the eye
3) the opposite happens in dim light, the radial muscles contract and the circular muscles relax making the pupil wider
how does the eye focus to look at near objects
3 points
1) the ciliary muscles contract which slackens the suspensory ligaments
2) the lens becomes fat (more curved)
3) this increases the amount by which it refracts light
how does the eye focus to look at distant objects
3 points
1) the ciliary muscles relax which allows the suspensory ligaments to pull light
2) this make the lens go thin (less curved)
3) so it refracts light by a smaller amount
how are people long-sighted
5 points
1) long-sighted (or hyperopia) people aren’t able to focus on near objects
2) this happens when the lens is the wring shape and doesn’t refract light enough or the eyeball is too short
3) the images of near objects are brought into focus behind the retina
4) you can use glasses with convex lens to correct it
5) the lens refracts light rays so they focus on the retina
how are people short-sighted
4 points
1) short-sighted (or myopia) people can’t focus on distant objects
2) this happens when the lens is the wrong shape and refracts light too much or the eyeball is too long
3) the images of distant objects are brought into focus in front of the retina
4) you can use glasses with a concave lens to correct it so the light rays focus on the retina
what are some alternative treatments for vision defects other than glasses
3 points
1) contact lenses
2) laser eye surgery
3) replacement lens surgery
how do contact lenses work
3 points
1) they are thin lenses that sit on the surface if the eye and are shaped to compensate for the fault in focusing
2) they’re popular because they’re lightweight and almost invisible and more convenient than glasses for activities like sports
3) the two main types of contact lenses are hard and soft lenses- soft lenses are generally more comfortable but carry more risk of infection
how does laser eye surgery work
4 points
1) a laser can be used to vaporise tissue, changing the shape of the cornea and so changing how strongly it refracts light
2) slimming it down makes it less powerful and can improve short sight, changing the shape so it’s more powerful will improve long sight
3) the surgeon can precisely control how much the laser takes off completely correcting vision
4) however there are risks of infection or the eye reacting in a way that makes your vision worse
how does replacement lens surgery work
3 points
1) sometimes long-sightedness can be more effectively treated by replacing the lens
2) in the surgery, the natural lens of the eye is removed and an artificial lens is inserted, made of clear plastic
3) however it does carry higher risk that laser eye surgery, including possible damage to the retina
how can body temperature be kept constant
3 points
1) the body has to balance the amount of energy gained and lost to keep the core body temp constant
2) there’s a thermoregulatory centre in the brain which contains receptors that are sensitive to the temperature of the blood flowing through the brain
3) the thermoregulatory centre also receives impulses from temperature receptors in the skin, giving info about skin temp
how is body temperature controlled by negative feedback
3 points
1) temperature receptors detect the core body temp it too high/low
2) the thermoregulatory centre acts as a coordination centre - it receives information from the temp receptors and triggers the effectors automatically
3) effectors produce a response and counteract the change
how do antagonistic effectors work
2 points
1) some effectors work antagonistically e.g. one heats and another cools - they’ll work at the same time to get a precise temperature
2) this mechanism allows a more sensitive response
what are some responses produced by effectors to counteract an increase in body temp
3 points
1) hairs lie flat
2) sweat is produced by sweat glands and evaporates from the skin, which transfers energy to the environment
3) blood vessels supplying the skin dilate so more blood flows close to the surface of the skin - this is called vasodilation and helps transfer energy to the environment
what are some responses produced by effectors to counteract an decrease in body temp
4 points
1) hairs stand up to trap an insulating layer of air
2) no sweat is produced
3) blood vessels supplying skin capillaries constrict to close of the skins blood supply - called vasoconstriction
4) you shiver (your muscles contract automatically), this needs respiration, which transfers some energy to warm the body
