Biology 1a

Human Biology. 

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  • Created by: Chloe
  • Created on: 23-10-11 14:15

Responding to Change

  • Your nervous system carries impulses around your body.
  • Hormones are carried around the body by blood and are released by glands.
  • They have long lasting effects.
  • Stimuli are picked up by receptors.
  • Receptors are in the sense organs.
  • Information passes along sensory neurones.
  • Impulse reaches CNS (Central Nervous System) made up of the brain and the spinal cord.
  • CNS co-ordinates information.
  • Motor neurones send impulses to the effector organs.
  • Effector organs are muscles or glands.
  • Receptor - Sensory Neurone - Co-ordinator (CNS) - Motor Neurone - Effector
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Reflex Actions

  • Reflexes are there to help you avoid dangers.
  • They involve 3 neurones: sensory, motor and relay.
  • Relay neurones connect sensory and motor and can be found in the CNS
  • The reflex arc is the process of reflexes. 
  • Junctions between the nerves are called synapses.
  • An electrical message travels along neurone and then reaches the synapse and is transferred to a chemical message and back again for the next neurone.
  • Stimulus - Receptor - Co-ordinator - Effector - Response
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The Menstrual Cycle

  • 28 days long - during this time the womb lining thickens and an egg matures.
  • At about day 14 egg released from ovary and lining stays thick for a few days.
  • If egg not fertilised a period takes place.
  • All changes brought about by hormones.
  • FSH secreted by pituitary gland, makes eggs mature and stimulates ovaries to produce oestrogen.
  • Oestrogen is made and secreted by ovaries, stimulates womb lining to thicken and secretion of LH.
  • LH secreted by pituitary gland stimulates release of a mature egg. 
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The Artificial Control of Fertility

  • Oral contraceptives (contraceptive pill) contain female hormones, mainly oestrogen.
  • The pill inhibits FSH production so no eggs mature in the ovaries.
  • If you use the pill you have to use it regularly to keep the hormone levels up.
  • For couples who are infertile, it might be that the female dosen't produce FSH so artificial FSH drugs are available.
  • Fertility drugs are also used when couples are going through IVF. 
  • During IVF eggs are removed from the ovaries and fertilised outside of the body then implanted in the womb.
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The Artificial Control of Fertility (cont)

  • The woman is given fertility drugs to help produce as many ripe eggs as possible.
  • Many advantages and disadvantages. 
  • The pill has helped decrease poverty ans control population growth. 
  • Fertility drugs can lead to multiple births which can be devastating for parents if one is lost and can cost the state a lot of money. 
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Controlling Conditions

  • It is important to keep everything constant internally, this is called homeostasis.
  • Water moves in and out of cells, how much depends on the ions in it. 
  • Water and minerals enter the body through food and drink. 
  • Water and salt leaves when you breathe out, in your sweat and in your urine. 
  • Kidneys change the amount of salt and water lost in your urine depending on body conditions. 
  • It is important that body temperature is kept at 37 because enzymes work best at this temperature. 
  • After a meal is digested glucose passes into your blood. 
  • Glucose levels are kept constant by insulin made in the pancreas. 
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Diet and Exercise

  • A healthy diet contains: carbohydrates, proteins, fats, vitamins, minerals, fibre and water. 
  • If diet is unbalanced then you will end up malnourished.
  • If you don't have enough vitamins and minerals you will have a deficiency disease. 
  • Males need more energy than females - unless they are pregnant. 
  • The more you exercise the more food you need as fitter people have more muscle and muscle tissue burns more energy than fat. 
  • The climate around you affects energy levels, the warmer it is the less energy needed. 
  • The metabolic rate is the rate at which chemical reactions occur in the body. 
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Weight Problems

  • Your BMI compares your mass to your height. 
  • The average BMI ranges between 20 and 30. A BMI below 18.5 or above 35 could indicate health problems.
  • If you take in more energy then necessary the excess is stored as fat. 
  • Obesity can lead to arthritis, diabetes, high blood pressure and heart disease. 
  • You can lose weight by reducing the amount of energy taken in and by exercising. 
  • Starvation is when you become very thin and muscles wear away, your immune system becomes weak and for females periods could become irregular or stop altogether. 
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Fast Food

  • The type and amount of fat in you diet and affect cholesterol levels.
  • Cholesterol is substance made in the liver and carried around in your blood. 
  • It is necessary to make the membranes in cells and hormones. 
  • High levels of cholesterol increase the risk of heart disease or diseased blood vessels as it builds up and eventually blocks them. 
  • The amount of cholesterol in the blood depends on the way your liver works and the amount of fat in your diet. 
  • Cholesterol is carried around the body by two types of liproproteins
  • Low Density Liproproteins are 'bad' cholesterol, raise risk of heart problems.
  • High Density Liproproteins are good. 
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Fast Food (cont)

  • There are 3 types of fat: saturated fats raise cholesterol, mono unsaturated fats reduce cholesterol and improve the balance between LDLs and HDLs and polyunsaturated fats do the same but better.
  • Salt is vital in the diet but too much of it can lead to high blood pressure. 
  • High blood pressure can damage the heart and kidneys and increase the risk of a stroke.  
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Drugs

  • Drug is a substance which alters the way the body works.
  • They are everywhere: coffee, tea, cigarettes and alcohol. 
  • There are some illegal drugs: cocaine, ecstacy and heroin. 
  • Sometimes you become addicted to a drug, then when you stop taking it you exprerience withdrawal symptoms. 
  • These can be aches, sweating, shaking, headaches and cravings. 
  • Drugs can make you feel very good about yourself.
  • Cannabis can be thought of as a safe or soft drug but it can cause psychological  problems. 
  • Hard drugs like cocaine and heroine are extremely addictive and can lead to severe health problems 
  • Sometimes they can lead to diseases like hepatitis, STDs and HIV/AIDS. 
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Legal and Illegal Drugs

  • All recreational drugs affect the way your brain and nervous system work. People enjoy this change and it makes them addicted. 
  • Caffeine, nicotine and cocaine speed up the activity of the brain. 
  • Alcohol and cannabis slow down the brain. 
  • Heroin stops impulses travelling in your nervous system. 
  • The sport world has a major problem with illegal drug usage. 
  • Drugs can build up muscle mass, make the body produce more blood, make you more alert and speed up reactions. 
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Alcohol

  • In small amounts alcohol makes people feel relaxed and cheerful. 
  • It is poisonous but your liver can get rid of it before it does damage
  • The alcohol goes into your boodstream and eventually slows down reactions. 
  • If you drink large amounts, your liver can't cope and you would suffer from alcohol poisoning. 
  • This can lead to unconsciousness, coma and even death.
  • Alcoholics' livers and brains suffer long term damage. 
  • They could develop cirrhosis of the liver and liver cancer. 
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Smoking an Health

  • Nicotine is the addictive drug in tobacco smoke. 
  • Non smokers have tiny hairs called cilia which move mucus away from the lungs. 
  • Smoking anaethetises cilia, allowing dirt down the lungs and the mucus to build up and cause coughing. 
  • Tar builds up in the lungs and turns them grey, it leads to alveoli breaking down and emphysema. 
  • Tar is a carcinogen (cancer causing substance).
  • Smoking raises blood pressure, causing heart attacks, strokes and thrombosis. 
  • Carbon Monoxide is in cigarette smoke; it reduces amount of oxygen carried in the blood.
  • This is why expectant mothers may suffer a premature birth, a baby with a low birth rate or a stillbirth. 
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Pathogens

  • Microorganisms which cause disease are called pathogens. 
  • Bacteria are single celled organisms, some cause disease but most are harmless. 
  • Viruses are smaller than bacteria. They can only reproduce by taking over another cell. 
  • Bacteria and viruses reproduce rapidly in the body. (Bacteria divide into two) 
  • Bacteria produce toxins which affect the body, viruses rarely produce toxins. 
  • Common disease symptoms are a high temperature, headaches. 
  • Many women in Ignaz Semmelweiss' hospital died of childbed fever. 
  • Semmelweiss realised medical students were goin straight from the mortuary to the delivery room so he insisted people wash their hands and fewer mothers died. 
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Defence Mechanisms

  • There are 4 main ways that pathogens spread: droplet infection, direct contact, contaminated food and through a break in the skin. 
  • Skin covers body and prevents pathogens reaching tissues. 
  • When skin is cut platelets in the blood form a clot which dries into a scab, sealing the cut and stopping pathogens entering. 
  • Breathing organs produce mucus to trap pathogens. 
  • Stomach acid destroys pathogens which enter through the mouth. 
  • The white blood cells are put of the immune system. 
  • They ingest microorganisms. 
  • They produce antibodies which target particular pathogens through the antigens. 
  • Once you have produced an antibody once it is easier to make again
  • Some white blood cells produce antitoxins which counteract toxins. 
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Using Drugs to Treat Disease

  • Often medicine has no effect on the pathogen, just the symptoms. 
  • Antiseptics an disinfectants are used outside of the body. 
  • Antibiotics kill disease inside the body. 
  • Antibiotics damage bacterial cells without damaging your cells.
  • They do not work on viruses. 
  • It is very difficult to kill a virus without killing your own cells. 
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Changing Pathogens

  • If you use antibiotics properly, the bacteria are almost killed.
  • The ones that are left may mutate and become resistant. 
  • If you don't finish the course or use them too often then bacteria become resistant due to natural selection. 
  • Hospitals often contain bacteria which aren't affected by common antibiotics, this is why diseases like MRSA are spread.
  • To stop MRSA all medical staff must wash their hands between patients, visitors must wash their hands on entering, infected patients must be kept in isolation, the hospital should be clean. 

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Developing New Medicines

  • A good medicine is effective, safe, stable and easy to consume and excrete. 
  • To develop a new drug researchers target a disease, then start computer testing, possible drugs are sythesised in the lab.
  • To test, first in vitro screening occurs with cell cultures, then it's animal testing, human testing on humans without the disease, a small amount of humans with the disease then a large amount. 
  • Meanwhile animal testing continues to test for long term side affects
  • Then the medicine has to be granted a license, before it is monitored for a time. 
  • We test drugs so thoroughly after thalidomide in the 50s, when animal tests on pregnant animals weren't carried out. 
  • Thalidomide successfully stopped morning sickness but had a tragic effect on developing fetuses. 
  • Many babies were born with limb abnormalities.
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Immunity

  • Antigens are proteins found on the outside of every cell.
  • White blood cells produce antibodies to attach antigens.
  • As white blood cells remember antibodies you can become immune to diseases. 
  • Vaccines are dead or weakened forms of diseases which help white blood cells form the right antibody. 
  • Society needs as many people as possible to be immunised for it to be effective. 
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