- Created by: xxcjxxevansxx
- Created on: 12-03-19 23:47
Your body needs to be kept at a constant temperature of 37 degrees to be able to function. Homeostasis is the regulation of internal conditions of your body (including cells). There are lots of automatic control systems in your body e.g. for temperature and glucose levels and these automatic control systems are made up of 3 compartments, the receptors, the coordination centre and the effector. When the level of something gets too high or too low your body uses negative feedback to correct itself (go back to normal).
1) Receptor cells detect a stimulus - one level too high,
2) The coordination centre receives that information and organises a response,
3) The effector produces a response which counteracts the change and restores the optimum level - the level decreases,
4) Receptor cells detect a stimulus - one level too low,
5) The coordination centre receives that information and organises a response,
6) The effector produces a response which counteracts the change and restores the optimum level - the level decreases.
This keeps happening as long as an organism lives or as long as the coordination centre is stimulated.
The nervous system
First, a stimulus is created and the receptor then detects the stimulus and creates an electrical impulse that travels along the sensory neurone. Before it hit the central nervous system, it has to cross a synapse, then through the central nervous system whether that is the brain or the spinal cord then carries on its journey past another synapse. After it has passed that synapse, it travels along the motor neurone to the effector and a response is created to keep you out of harm's way.
A great example of this is the knee jerk. This is when someone hits your knee in a certain place and it jerks upwards and this cannot be controlled as it is an involuntary action
Synapses and reflexes
A synapse is a gap between two neurones and to get the electrical impulse across the synapse, a chemical transmitter diffuses it across. Reflexes are rapid and automatic responses that don't involve the conscious part of your brain that keeps you out of danger and reduce your chances of getting injured. The passage of information from the receptor to the effector is called the reflex arc. The quickest responses to prevent you from getting injured go through your spinal cord instead of your brain because it is closer and has fewer synapses. An example is down below:
1) A bee stings your finger
2) Stimulation of the pain receptor
3) Impulses travel along the sensory neurone
4) Impulses are passed along a relay neurone via a synapse
5) Impulses travel along a motor neurone via a synapse
6) When the stimulus reaches the effector it either contracts or secrets and in this case, it contracts.
Investigating reaction time 1/2
Hypothesis - Who in the class has the fastest reaction time?
Equipment - Metre ruler - At least 2 people - Paper
1) Person one should sit down and rest their arm on the edge of the table.
2) Person two should hold a ruler, vertically, with their thumb and index finger whilst making sure that the zero ends of the ruler are level with person twos finger and thumb. Person two should drop the ruler without warning and person one should catch it as fast as they can from when they see it drop.
3) They should put this in a table and do it at least 10 times and then calculate a mean for the distance that person one caught the ruler.
Challenge - You could give the person one something to speed up or slow down their reaction times and wait 10 minutes and do the experiment again and write down the results and compare them to their normal reaction times and see how they differ.
Investigating reaction times 2/2
Independent variable - The substance you give the person to speed up or slow down their reaction times
Dependent variable - How fast they can catch the ruler
Control variables - The person dropping the ruler - Where the person catching the ruler sits - What arm they use.
They can also use a computer to measure the reaction times and this is an advantage because they are more accurate than a stopwatch
The brain 1/2
The brain is the other part of our central nervous system which is made up out of billions of interconnected neurones that control and coordinate everything we do e.g. breathing, movement and even memory.
Cerebral cortex- This is the outer wrinkly bit that is responsible for consciousness, intelligence, memory and language.
Medulla - Control conscious activity like breathing and your heartbeat. (things you don't have to think about).
Cerebellum - Responsible for muscle coordination.
The brain 2/2
Methods of studying the brain:
1) Studying a patience brain with brain damage - This can have a massive effect on the patient and you can tell a lot about what part of the brain is damaged does.
2) Electrically stimulating the brain - This can be done by pushing tiny little electrodes into the tissue and zapping it with electricity.
3) MRI scans - It is a fancy tube-like machine that takes very detailed images of your brain and scientists to use this to see what parts of the brain are working whilst doing certain activities.
Knowledge of the brain has lead to new medical discoveries but that all doesn't come without a price. That price is that you can have physical damage done to the brain or for it to develop problems with it functioning properly.
The eye 1/2
Sclera - The tough supporting wall of the eye.
Cornea - The transparent outer layer found at the front of the eye.
Iris - Contains muscles that allows it t control the diameter of the pupil and therefore how much light it allows to enter the eye.
Lens - Focuses the light onto the retina.
Ciliary muscles and suspensory ligaments - These control the shape of the eye.
Optic nerve - Carries impulses from the receptors on the retina to the brain.
As light enters the eye, the pupil can do one of two things, either dilate or contract. When there is too much light the eye contracts so the pupil is smaller and they do this by contracting the radial muscles and relaxing the rods. But if there is very little light they the eye would dilate by relaxing the radial muscles and contracting the rods.
The eye 2/2
To look at near objects:
- The ciliary muscles contract whilst the suspensory ligaments slacken and the lens becomes fatter. This increases the amount by which it refracts light.
To look at far away object:
- The ciliary muscles slacken whilst the suspensory ligaments contract and the lens becomes thin. This decreases the amount by which it refracts light.
Correcting vision defects
Long-sighted people are unable to focus on near objects and this is because the lens is the wrong shape (too thin) so that the light ray crosses just before the retina or another reason is that their eyeball is too short. One way to correct this is to wear glasses or contacts because they refract the light rays to focus on the retina. Another word for long sightedness is hyperopia.
Short-sighted people are unable to focus on far objects and this is because the lens is the wrong shape (too big) so that the light rays cross just after the retina or another reason is that their eyeball is too long. One way to correct this is to wear glasses or contacts because they refract the light rays to focus on the retina. Another word for short-sightedness is myopia.
There are 4 main ways to correct vision defects;
- contact lenses,
- laser eye surgery,
- replacement lens surgery
Controlling the body's temperature 1/2
The body's temperature needs to be kept at 37 degrees Celsius as it is the optimum temperature for enzymes.
1) The temperature receptors detect that the core body temperature is too high,
2) The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically.
3) Effectors produce a response and counteract the change.
4) The temperature receptors detect that the core body temperature is too low,
5) The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically.
6) Effectors produce a response and counteract the change and then goes back to step one.
Controlling the body temperature 2/2
When you're too hot:
- Sweat is produced by your sweat glands and evaporates off your skin.
- As well as that, the blood vessels dilate ( expand) so there is more blood to the surface of the skin to cool you down (vasodilation).
- Also, the hairs on your arms flatten so they trap as less air as they can and more heat can escape.
When you're too cold:
- Hairs stand up to trap a layer of air next to your skin.
- No sweat is produced.
- Vessels constrict (shrink) so not much heat is lots next to the surface of the skin.
- You can also shiver and your body needs respiration for this as your muscles contract and use up energy in the process.
The endocrine system 1/2
The pituitary gland:
- Produces many hormones that regulate the body.
- These hormones act on glands telling them what they need to release and how much.
- Produces thyroxine.
- Regulates the rate of metabolism, heart rate and temperature.
The adrenal gland:
- Produces adrenaline
- Prepares the body for the 'fight or flight' response.
- Produces insulin.
- Regulates blood glucose.
The endocrine system 2/2
The ovaries (females only):
- Produces oestrogen.
- It is involved in the menstrual cycle.
The testes (males only):
- Produces testosterone.
- Controls puberty and sperm production.
- Very fast.
- Acts for a short time.
- Acts in a precise area.
- Slower action.
- Acts for a longer time.
- Acts in a general way.
Controlling glucose in blood
Eating carbohydrates puts glucose into the bloodstream and then insulin takes it out. the more exercise you do the more glucose is burned off in your energy. Excess glucose is stored in the liver and muscles as glycogen.
When blood glucose levels are too high, your body does this:
- insulin is secreted by the pancreas into the bloodstream.glucose then moves into the liver, with the insulin, and the insulin turns the glucose into glycogen. Therefore the bloodstream now has less glucose in.
When blood glucose levels are too low, your body does this:
Glucagon is secreted by the pancreas into the bloodstream. The glucagon makes the liver turn glycogen back into glucose The the liver diffuses the glucose into the bloodstream and therefore the blood now has more glucose.
if you have diabetes, you can have two types of it. type one is where your pancreas doesn't produce enough insulin whereas type two is when you don't do enough exercise to get rid of the glucose and glycogen in your body.
The kidneys basically act as a filter and clean out all of the waste products but keep the ones that our body needs (selective reabsorption).
1) proteins cannot be stored and so are changed into fats and carbohydrates so they can be stored. This happens in the liver and is called deamination.
2) Ammonia is produced as a waste product from deamination.
3) Ammonia is toxic so it is converted into urea in the liver, then is transported into the kidneys. It is then filtered out and excreted from the body as urine.
1) Ions enter the body through the food we eat and absorbed by the blood.
2) If the ion content is too high or too low, it can upset the balance of water and how much water the cell takes in via osmosis. This can really damage cells by making them shrink or burst.
Kidney failure 1/2
You can survive with one kidney but when that one kidney fails it becomes a big problem. You either have to have a transplant or dialysis.
- Advantage - live longer
- Disadvantage - majour opperation.
This is when you go into hospital 3-4 times a week and sit hooked up to a machine for 4-6 hours whilst it cleans your blood and put in anything you need; water, ion and glucose.
- Advantage - live longer
- Disadvantage - you have to go to the hospital multiple times a week.
But there is always the risk of rejection.
The kidneys 2/2
3) The right amount of ions are reabsorbed by the kidneys and some are lost in sweat.
1) The body has to constantly balance the water level in your body because we lose water when we sweat from the skin and from the lungs when we breathe.
2) We can't control how much comes out only how much goes in, so the amount of water in our blood is balanced by how much we consume and how much is removed by the kidneys.
The concentration of urine is controlled by the hormone ADH (anti-diuretic hormone).
1) A receptor in the brain detects that the water content is too high.
2) The coordination centre in the brain receives the information and coordinates a response.
3) The pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules.
4) A receptor in the brain detects that the water content is too low.
5) The coordination centre in the brain receives the information and coordinates a response.
6) The pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules.
Puberty and the menstural cycle
Day 1-4 = Menstruation starts and the uterus lining breaks down around day 4. (stage 1)
Day 4-14 = The uterus lining builds up again into a thick spongy layer full of blood vessels, ready to receive a fertilised egg. (stage 2)
Day 14 = The eggs develop and it released from the ovary, this is called ovulation. (stage 3)
Day 14-28 = The wall is then maintained. If no fertilized egg has landed on the uterus wall by day 28, the lining breaks down and the whole cycle starts again. (stage 4)
FSH (follicle stimulating hormone) - produced in the pituitary gland - causes the egg to mature in the follicle - stimulates the ovaries to produce oestrogen.
Oestrogen - produced in the ovaries - causes the uterus wall to build up - stimulates the release of LH and stops the production of FSH.
LH (luteinising hormone) - produced by the pituitary gland - stimulates the release of the egg.
Progesterone - Produced in the ovaries - maintains the uterus wall and when the progesterone levels fall, the wall breaks down - stops LH and FSH
Barrier methods: (stops the sperm from meeting the egg)
- Condom - advantage - protects against STI's - disadvantage - can be spilt/come off
- Diaphragm - advantage - stops sperm and egg meeting - disadvantage - can come out of place/ has to be fitted by a specialist.
- The pill - advantage - reduces heavy periods/very effective - disadvantage - if you forget it one day, you can get pregnant.
- Sterilisation - advantage - you can have sex without getting pregnant - disadvantage - it can take months for all the sperm to leave the male's body/operation.
- Natural methods - advantage - pregnancy can be avoided - disadvantage - can be difficult and not effective.
- Abstinence - advantage - you won't get pregnant.
If couples can't seem to produce a fertilized egg, they can go for IVF. Against - can be harming a potential life or it is unethical. For - the embryos are going to be chucked anyway.
Auxin is a plant hormone that controls the growth of the plant in response to the light ( phototropism) and gravity ( gravitropism or geotropism). Shoots grow towards the light and away from gravity whilst the roots grow towards gravity.
Plant hormone investigation
1) Put a bulb into the soil the right way up and one in another container upside down. Cover them up with soil and leave for a few weeks in a well-lit room and a warm room.
2) The bulb that is the right way up should grow normally towards the light whilst the bulb that is upside down the roots should grow downwards and the shoot will curve upwards towards the light.
independent variable - the way the bulb is positioned
dependent variable - how tall the shoot grows.
control variable - where the plant is placed, temperature and the amount of water given.
Homeostasis - the optimum conditions organs need to stay at (37 degrees Celsius).
Optimum - the top conditions.
Central nervous system - the brain and the spinal cord
Sensory neurone - the neurone that takes the electrical impulse to the central nervous system.
Motor neurone - the neurone that takes the electrical impulse away from the central nervous system.
Effectors - an organ or cell that acts in response to a stimulus.
Receptors - an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve. (an organ that can be stimulated)
Synapses - these are the gaps between the neurones. To get the electrical impulses across the synapses, they have to chemically transmitted/ diffused to the other side.
Control variable - what we keep the same.
Dependent variable - what we measure.
Independent variable - what we change.
Hormone - is a chemical messenger that travels in the blood to target organs.