Biology 1a

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Fightning Diease

Bacteria

1. Bacteria are very small cells which can reproduce rapidly inside your body

2. They make you feel very ill by doing two things: a) damaging your cells, b) producing toxins (poisons)

Viruses

1. Viruses are not cells. They are tiny.

2. They replicate themselves by invading your cells and using the cells' machinery to produce many copies of themselves. The cell wiill usually burst, releasing all the new viruses

3. This cell damage is what makes you ill

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Fightning Diease

Your Body Has A Pretty Sophisticated Defence System

1. Your skin, plus hairs and mucus in your respiratory tract (breathing pipework) to stop bad things getting into your body

2. And to try and prevent microogranisms getting into your body through cuts, small fragment of cells (called platelets) help blood cot quickly to seal wounds. If the blood contains low numbers of platelets then it will clot more slowly

3. But if something does make it through, your immune system kicks in. The most important part is the white blood cells. They travel around in your blood and crawl into very part of you, constantly patrolling for microbes. When they come across an invading microbe they have three lines of attack

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Fightning Diease - White Blood Cells

White Blood Cells - Three lines of attack

1. Consuming Them:

White blood cells can engulf foreign cells and digest them.

2. Producing Antibodies:

- Every invading cell have unquie molecules (called antigens) ont its surface

-When your white blood cells come across a forgein antigen (i.e one they don't recongise), they will start to produce proteins called antibodies to lock onto and kill the invading cells. The antibodies produced are specific to that type of antigen - they wont lckn on to any others 

- Antibodies are the produces rapidly and carried around the body to kill all similar bacteria or viruses

-If the person is infected with the same patjogen again the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that patjogen and won't get ill.

3. Producing Antitoxins:

These counteract toxins produced by the invading bacteria

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Fightning Diease - Vaccination

Vaccination- Protects from Future Infections

1. When your infected with a new microogranism, it takes your white blood cells a few days to learn how to deal with it. But by that time, you can be pretty ill.

2. Vaccinations invole injecting small amounts of dead or inactive microogranisms. These carry antigens, which cause your body to produce antibodies to attack them- even though the microogransim is harmless (since its dead or inactive) For example, the MMR vaccince contains weakened versions of the virsues that cause measles, mumps and rubella (German measles) all in one vaccine.

2. But if live microogranisms of the same type appear after that, the white blood cells can rapidly mass-produce antobpdies to kill off the pathogen.

3. Some vaccinations "wear off" over time. So booster injections may need to be given to increase levels of antibodies again.

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Pros and Cons of Vaccination

Pros and Cons of Vaccination

Pros:

1. Vaccines have helped control lots of infectious dieases that were once common in the uk (e.g. measles, whooping cough etc.)

2. Big outbreaks of diease - called epidemics- can be prevented if a large percentage of the population is vaccinated. That way, even the people who aren't vaccianted are unlikely to catch the diease because there are fewer people able to pass it on. But if a significant number of people aren't vaccianted , the diease can spread quickly throught them and lots of people will be ill at the same time

Cons:

1. Vaccines don't always work- sometimes they don't give you immunity

2. Sometimes you can have a bad reaction to a vaccine (e.g. swelling or maybe a seizures) But bad reactions are very rare.

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Fightning Diease -Drugs

Some Drugs Just Relieve Symptons - Others Cure the Problem:

1. Painkillers (e.g. aspirin) are drugs that relieve pain. However, the don't tackle the cause of the diease, they just help to reduce the symptoms.

2. Other drugs do similar kind of things- reduce the symptons without tackling the underlying cause. For example, lots of "cold remedies" don't actually cure colds.

3. Antibiotics (e.g. penicillin) work differently- they actually kill (or prevent the growth of) the bacteria causing the problem without killing your own body cells. Different anitboitics kill different types of bacteria, so its important to be treated with the right one.

4. But antibiotics don't destroy viruses (e.g. flu or cold viruses). Viruses reproduce using your own body cells which make it very difficult to develop drugs that destroy jus the viruse without killing the body cells.

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Fightning Diease -Drugs

Bacteria can become Resistant to Antibiotics

1. Bacteria can mutate- sometimes the mutations cause them to be resistant to (not killed by) an antiboitic.

2. If you have an infection, some of the bacteria might be resistant to antiboitics

3. This means that when you treat infection, only the non-resistant starins of bacteria will be killed.

4. The individual resistant bacteria will surive and reproduce, and the population of the resistant strain will increase. This is an example of natural selection.

5.This resistant strain coul cause a serious infection that can't be treated by antibiotics. E.g. MRSA cause serious wound infectious and is resistant to the powerful antiboitic methicillin.

6. To slow down the rate of development of resistant strains, it is important for your doctor to avoid over-prescribing antiboitics. So you won't get them for a sore throat, only for something more serious.

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Fightning Diease -Drugs

You can investigate antibiotics by growing microogranisms in the Lab

You can test the action of antibiotics or distinfectants by growing cultures of micrrogranisms:

1. Microogranisms are grown (cultured) in a "culture medium". This is usually agar jelly contaning carbohydrates, minerals, proteins and vitamins they need to grown.

2. Hot agar jelly is poured into shallow round plastic dishes called Petri dishes.

3. When the jelly's colled and set, inculating loops (wire loops) are used to transfer microogranisms into the culture medium. The microogranism then multiply.

4. Paper discs are soaked in different types of antiboitics and placed on the jelly. Antiboitic- resistant bacteria will contiune to grow around them but non-resistant strains will die.

5.The petri dishes, culture medium and inoculating loops must be sterlised before use, e.g. the inoculating loops are passed through a flame. If equipment isn't sterilised, unwanted microorganisms in the culture will grow and affect the result

6.In the lab at school, cultures of microgranisms are kept at about 25C because harmful pathogens arent likely to grow at this tempeture.

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Fightning Diease- Past and Future

Semmelweis Cut Deaths By Using Antiseptics

1. While Ignaz Semmelweis was working in Vienna General Hospital in the 1840's, he saw that women were dying in a huge numbers after childbirth from a diease called puerperal fever

2. He believed that doctors were spreading the diease on their unwashed hands. By telling doctorsentering his ward to wash their hands in an antispetic solution, he cut the death rate from 12% to 2%

3. The antispectic solution killed bacteria on doctors hands, though Semmelweis didn't know this (The exictence of bacteria and their part in causing diease wasn't discovered for another 20 years). So semmelewis couldn't prove why his idea worked and his methofs were dropped when he left the hospital (allowing death rates to increase)

4. Nowadays we know that basic hygiene is essential in controlling diease

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Synapes and Reflexes

Synapse Connect Neurones

1. The connection betweeen two neuornes is called a synapse.

2. The nerve signal is transferred by chemicals which diffuse (move) across the gap

3. These chemicals then set off a new electrical signal in the next neurone

Reflexes Help prevent injury

1. Reflexes are automatic responses to certain stimuli- they can reduce the chances of being injured.

2. For example, if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye - this stops it getting damaged

3. Or if you get a shock, your body releases the hormone adrenaline automatically - it doesn't wait for you to decide that you're shocked

4. The ppassage of information in a reflex (Receptor to effector) is called a reflex arc

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Synapes and Reflexes

The Reflec Arc Goes Through The Central Nervous System

1. The neurones in relfex arcs go through the spinarl cord or through an unconscious part of the brain.

2. When a stimulus (e.g. a painful bee sting) is dected by receptors, impluses are sent along a sensory neurone to the CNS

3. When the impulses reach a synapse between the sensory neurone and relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone

4. When the impulses reach a synapse between the relay neurone and a moter neurone, the same thing happens. Chemicals are released and cause impluses to be sent along the motor neurone.

5. The impulses then travel along the motor neurone to the effector (In this example its a muscle)

6. The muscle then contracts and moves your hand away from the bee.

7. because you dont have to think about the response (Which takes time) its quicker than normal responses.

Stimulus- Receptor-Sensory neurone-Relay neurone-Motor neurone-Effector-Response

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Synapes and Reflexes

1. Cheeky bee stings 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 synapse

6. When impluses reach muscle it contracts

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Hormones

Hormones are chemical messengers sent in the blood

1. Hormones are chemicals released directly into the blood. They are carried in the blood plasma to other parts of the body. Hormones control things in organs and cells that need constant adjustment.

2. Hormones are produced in various glands. They travel through yout body at "the speed of blood"

2. Hormones tend to have relatively long lasting effects

The Pituitary Gland:

This produces many important hormones including FSH and LH, which are involved in the menstrual cycle.

Ovaries:

Produce oestrogen, which is involved in the menstrual cycle..

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Hormones

Hormones and Nerves Do Similar Jobs, but There Are Differences

Nerves:

1. Very FAST action

2. Act for a very SHORT TIME

3. Act on a very PRECISE AREA

Hormones:

1. SLOWER action

2. Act for a LONG TIME

3. Act in a more GENERAL way.

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The Menstrual Cycle

The Menstrual Cycle Has Four Stages

Stage 1:

Day 1 is when the bleeding starts. The uterus lining breaks down for abour four days.

Stage 2:

The linning of the uterus builds up again, from day 4 to day 14 into a thick spongy layer full of blood vessels, ready to recieve a fertilsed egg.

Stage 3:

An egg is released from the ovary at day 14

Stage 4: The wall is then maintanied for about 14 days, until day 28. If no fertilsed egg has landed on the uterus wall by day 28 the spongy lining starts to break down again and the whole cycle starts again.

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Hormones

There are three main hormones involved:

1. FSH (Follicle-Stimulating Hormone):

-Produced by the pituitary gland.

-Cause an egg to mature in one of the ovaries

- Stimulates the ovaries to produce oestrogen.

2. Oestrogen:

-Produced in the ovaries

-Causes pituitary to produce LH

-Inhibits the futher release of FSH

3. LH (Lutenising Hormone):

-Produced by the pituitary gland   -Stimulates the release of an egg at around the middle of the menstrual cycle

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Controlling Fertility

Hormones can be used to reduce fertility

1. Oestrogen can be used to prevent the release of an egg- so it can be used as a method of contraception

2. If you take Oestrogen everyday to keep the level of it permanently high, it inhibits the production of FSH

3. Progestrogene also reduces fertillity e.g. by stimulating the production of thick cervical mucus which prevents any sperm getting through and reaching an egg

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Controlling Fertility

Hormones can be used to reduce fertility

1. Oestrogen can be used to prevent the release of an egg- so it can be used as a method of contraception

2. If you take Oestrogen everyday to keep the level of it permanently high, it inhibits the production of FSH

3. Progestrogene also reduces fertillity e.g. by stimulating the production of thick cervical mucus which prevents any sperm getting through and reaching an egg

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Controlling Fertility

Pill

'The pill' is an oral contraceptive that greatly reduces the chances of mature eggs being produced. The pill contains oestrogen, or oestrogen and progesterone. These hormones prevent eggs from maturing in the ovaries.

Pros:

1. The pills over 99% effective at preventing pregnancy

2. Reduces the risk of getting some types of cancer

Cons:

1. It isn't 100% effective- there's still a very slight chance of getting pregnant

2. It can cause side effect like headaches, nauses

3. It doesn't protect against STD's

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IVF

IVF- In vitro fertilisation 

If a couple are having difficulty conceiving a child because the quantity or quality of the man’s sperm is poor then IVF can be used. This is where the egg is fertilised outside the woman’s body and then implanted back into her uterus. As FSH can also be used to encourage the production of several mature eggs at once, it is used as part of IVF to increase the number of eggs available for fertilisation.

Pros:

- Fertility treatment can give an infertile couple a child

Cons:

-Some women have strong reactions to the hormones - e.g. abdominal pain.vomiting

- increase of cancers

-Mulitiple births

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Plant Hormones

Auxin is a Plant Growth Hormone

1. Auxin is a plant hormone that controls growth near the tips of shoots and roots

2. It controls the growth of a plant in respone to light (Phototorpism), gravity (gravitropism or geotropism) and mositure

3. Auxin is produced in the tips and moves backwards to stimulate the cell elongation (enlargement) process which occurs in the cells just behind the tips

4. If the tip of a shoot is removed, no auxin is available and the shoot may stop growing.

5. Extra auxin promotes growth in the shoot but inhibits growth in the root - producing desired results.

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Homeostasis

Your body needs some things to be kept constant

To keep all your cells working properly, certain things must be kept at the right level - not too high, and not too low.

Bodlily levels that need to be controlled include:

1. Ion content

2. Water content

3. Sugar content

4. Temperature

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Homeostasis

Ion content is regulated by the kidneys

1. Ions are taken into the body in food, then absorbed into blood

2. If the food contains too much of an kind of ion then the excess ions need to be removed. E.g. a salty meal will contain far too much

3. Some ions are lost in sweat

4. The kidneys will remove the excess from the blood - this is then got rid of in urine.

Body temperatue is controlled by the brain

1. All enzymes work best at a certain temperture - 37C and so this is the temperature your body tries to maintain.

2. A part of the brainacts as your own personal thermostat. It's sensitive to the blood temperature in the brain, and recieves messages from the skin that provide information about skin temperature

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Drugs

A drug is a substance taken into the body that modifies or affects chemical reactions in the body. Some drugs are beneficial, while others are harmful.

Type of drugEffect on bodyExample Depressant Slows down nerve and brain activity Alcohol, solvents, temazepam Hallucinogen Alters what we see and hear LSD Painkiller Blocks nerve impulses Aspirin, paracetamol Performance enhancer Improves muscle development Anabolic steroids Stimulant Increases nerve and brain activity Nicotine, caffeine, ecstasy

Illegal drugs are classified from Class A to Class C. Class A drugs are the most dangerous, with the most serious penalties for possession or dealing. Class C are the least dangerous, with the lightest penalties, but this does not mean they are safe to use.

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Drugs

Three stages of testing drugs

There are three main stages of testing:

  1. The drugs are tested using computer models and human cells grown in the laboratory. Many substances fail this test because they damage cells or do not seem to work.
  2. Drugs that pass the first stage are tested on animals. In the UK, new medicines have to undergo these tests. But it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects.
  3. Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check that they are safe. The substances are then tested on people with the illness to ensure that they are safe and that they work.
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Drugs

Clincal Trials -

In clinical trials, one group of volunteers - called the test group - receives the new drug. Another group - the control group - receives the existing drug for that illness. If there is no existing treatment, the control group is given a placebo. The researchers look for differences between the test group and the control group.

blind trials – the volunteers do not know which group they are in but the researchers do

The problem with blind trials is that the researchers may give away clues to the volunteers without realising it. This can make the results unreliable.

double-blind trials – neither the volunteers nor the researchers know which group the volunteers are in until the end of the trial

Double-blind trials are more complex to set up, but they remove the chance of bias and so the results are more reliable.

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Performance enhances

Performace- Enhancing drugs have health and ethical impacts

1. Some althetes take performce- enhancing drugs to make them better at sport.

2. There are severel different types, including anabolic steroids (that increase muscle size) and stimulants (that increase heart rate)

3.These drugs have a negetive health effects

4. Some of these drugs are banned by law some are prescreption only

5.There are ethical problems behind enhacning drugs

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Performance enhances

Against Drugs:

1. Its unfair if people gainadvantage by taking drugs not just through training

2. Athletes may not be fully informed of the serious health risks of the drugs they take

For drugs:

1. Atlees have the right to make their own decisions about whether taking drugs is worth the risk or not

2. Drug free sport isn't really fair anway- different athlettes have acces to different traning facilities, coaches, equipment etc

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Drugs

Cannabis is a "stepping stone":

The effects of cannabis create a desire to try harder drugs

Cannabis is a "gateway drug":

Cannabis use brings people into contact with drug dealers

It's all down to gentics:

Some peple are more likely to take drugs generally, so cannabis users will also try other drugs

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Thalidomide

Thalidomide

1. Thalidomide was intended as a sleeping pill and was tested for that use. But later it was also found to be effective in relieving moring sickness in pregnant women

2.Unfortunely, Thalidomide hadn't been tested as a drug for moring sickness and so it wasn't known that it could pass through the placenta and affect the fetus, causing abnormal limb development. In some cases, babies were born with no legs or arms

3. About 10,000 babies were affected by thalidomide and only about half of them survied

4. The drug was banned and more rigorous testing procedures were introduced

5. More recently thalidomide has been used in the treatment of leporsy and other dieases e.g. some cancers

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