Unit 3.3 (Keeping Internal Conditions Constant)

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  • Homeostatis
    • Controlling Temperature
      • Why?
        • If the temperature is too hot then the enzymes will denature and will no longer be able to catalyse the reactions in the  body, such as respiration.
        • If the core body temperature is too low then the enzymes will not be able to catalyse the reactions at a fast enough rate.
      • Cooling Down
        • The blood vessels that supply the capillaries near the surface of the skin dilate (widen) so that more blood can reach the skin's surface. The skin becomes redder so that more heat is lost through radiation.
        • The body starts to shiver. The muscles need energy to contract and relax and this energy is released through respiration in the cells. Respiration is exothermic, and this heat helps to warm the body up.
        • Hypothermia
          • If the weather is too cold and your core body temperature falls below 35°c you will suffer from hypothermia. Extreme hypothermia will result in the enzymes no longer working (vital reactions in your cells such as respiration will no longer be able to take place) which will result in you becoming unconscious and may lead to death. 
          • Keeping active when it is cold can help the body to warm up.During exercise your muscles contract and this needs lots of respiration which releases energy to keep you warm.
          • A healthy diet with plenty of fluid, warm drinks and regular meals can help give you energy so that your body can generate heat. Avoiding alcohol, caffeine and nicotine can help as they all increase the rate at which the body loses heat.
      • Warming up
        • The body produces sweat. This sweat needs energy to evaporate from the skin's surface, this helps to remove excess heat.
        • Heat Stroke
          • Heat stroke happens when your body gets too hot. At high temperatures the enzymes denature and stop working. Eventually if the body is unable to cool down you will go into a coma and die.
          • If the weather is really hot it is important to take in water to the replace the water lost through sweating. An isotonic drink which restores ion, glucose and water content in the body is also recommended.  
          • Eat foods with a high water contents such as salad and fruit, this combined with drinking regularly will help to prevent dehydration. It is advisable to go indoors into a cooler environment in order to decrease your core body temperature. 
      • How?
        • Temperature is controlled by the thermoregulatory centre in the brain. This centre has detectors which monitor the temperature of the blood flowing through the brain.
        • Temperature receptors in the skin also send impulses to the brain to give information about skin temperature.
    • The KIdney
      • Function?
        • The kidney filters the blood, excreting substances that you do not want and  keeping the substances that the body needs.
      • Filtering the Blood
        • The kidneys filter the blood, then reabsorbing sugars, mineral ions and any water that the body needs. Any excess water, excess ions and urea is temporarily stored in the bladder before being removed from the body.
      • What is urea?
        • Urea is produced in the liver from the breakdown of amino acids, removed by the kidneys in the urine and temporarily stored in the bladder.
      • Kidney Failure
        • if the person suffers from untreated kidney failure  they will eventually die due to the build up of toxins in the body.
        • Dialysis
          • A dialysis machine acts as an artificial kidney.
          • A dialysis machine acts as a partially permeable membrane, on one side is the patient's blood  and on the other is the dialysis fluid. The dialysis fluid contains the same concentration of glucose and ions as normal blood. If the patient's blood as too much or too little glucose and ions they will diffuse in and out accordingly. .
          • The dialysis fluid contains no urea, so the step concentration gradient causes all urea to diffuse out of the patient's blood
          • Advantages:
            • Dialysis is readily available
            • It keeps the patient alive while they wait for a transplant.
          • Disadvantages
            • It performs only 10% of the work a functioning kidney does.
            • Can cause serious health problems such as anemia, bone disease, nerve infection and heart disease.
            • Haemodialysis involves using the machine three times a week,with each session usually lasting for about four hours - very inconvenient.
            • Diet has to be controlled
        • Transplant
          • A diseased kidney is replaced with a healthy one,, donated from either a living donor or a victim of a fatal accident
          • The kidney must be a very good tissue match to prevent rejections. The recipient's antibodies may attack the antigens on the donor organ because they recognize them as being foreign.
          • Advantages
            • Kidney transplants are gernerally cheaper than dialysis.
            • The patient is free to live a normal life and eat what they like.
            • Patients who receive a kidney transplant generally live longer than those who stay on dialysis.
          • Disadvantages
            • A patient often has to wait for a kidney to become available. In America there are over 93000  people on the kidney transplant lsit
            • The patient has to take immonosuppressant drugs for the rest of their lives so that the new kidney is not rejected.
            • Transplanted organs do not last forever. The average kidney works for around 9 years.
    • Controlling Blood Glucose
      • The pancreas monitors and controls blood glucose.
      • Too much glucose?
        • The pancreas produces insulin. Insulin causes glucose to move from blood into the cells.
        • Excess glucose is converted into glycogen for storage by the liver.
      • Too little glucose?
        • The pancreas releases glucagon which causes glycogen in the liver to convert to glucose and is then released back into the blood.
      • Type 1 Diabetes
        • If no, or too little, insulin is produced by the pancreas the blood glucose level may become very high. Type 1 diabetes is controlled by injections of insulin and careful attention to diet and levels of exercise.
        • Potential methods for treating diabetes include: pancreas transplants, using embryonic stem cells to produce insulin secreting cells and genetically engineering pancreas cells to make them work properly.


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