B3.3 Homeostasis Flashcards
Define homeostasis.
The maintenance of a constant internal environment
What are the three main roles of the kidney?
- Removal of urea
- Adjustment of ion content
- Adjustment of water content
How does carbon dioxide leave the body?
Through the lungs when you exhale
How is carbon dioxide produced in the body?
As a product of respiration
Where is urea produced?
The liver
How is urea produced?
- Excess amino acids are broken down into fats and carbohydrates (the body can’t store proteins)
- Urea is a waste poisonous product of this reaction
How does urea leave the body?
- Stored temporarily in the bladder as urine
- Is excreted from the body
What are six things the body has to regulate?
- Body temperature
- Glucose levels
- Ion content
- Water content
- Carbon dioxide removal
- Urea removal
Where do ions (e.g sodium) enter the body?
In the food we eat
What happens if ion/water content is wrong?
The balance between ions and water will be upset, causing too much or too little water to be draw into body cells by osmosis.
Name 3 ways water is lost.
- Urine - Sweat - Air we breathe out
When we sweat little, what is the urine produced by our bodies like?
- Dilute and pale
- Lots of it
When we sweat a lot, what is the urine produced by our bodies like?
- Minimal
- Dark coloured and concentrated
Describe the process in the kidneys.
1) Ultrafiltration. High pressure squeezes glucose, ions, water and urea out of the blood (that entered through the renal artery) and into the Bowman’s capsule.
2) Reabsorption. These molecules travel along the nephron which reabsorbs all glucose and some ions and water into the blood
3) Waste molecules are carried out of the nephron to the bladder where they are temporarily stored before excretion.
What are nephrons?
Filtration units in the kidneys
Why does the body need to control temperature?
Enzymes work best at 37 degrees C.
If temperature is too hot/cold it will cause enzymes to stop working and important reactions will be disrupted,
What part of the brain detects temperature change?
The thermoregulatory centre
How does the thermoregulatory centre detect temperature change?
- Receptors in the brain sense the temperature of the blood flowing through it.
- Receptors in the skin send impulses to the brain when the skin temperature changes.
What happens when temperature increases too much?
- Sweat increases (evaporation cools skin)
- Hair lies flat
- Vasodilation (vessels wider and closer to the skin surface)
What happens when temperature decreases too much?
- Hairs stand up (insulating layer)
- Vasoconstriction (vessels thinner and move deeper)
- Minimal sweating
- Shivering - contracting muscles respire - releasing energy
What organ controls and monitors blood glucose?
The pancreas
Describe the process when there is too much glucose in the blood.
- Insulin secreting cells in the pancreas are stimulated
- Insulin is secreted
- Insulin stimulates glucose uptake from the blood
- Glucose is stored as glycogen in the liver
Describe the process when there is too little glucose in the blood.
- Glucagon secreting cells in the liver are stimulated
- Glucagon is secreted
- Glucagon stimulates the liver breakdown of glycogen into glucose
What is type 1 diabetes?
A disease in which a person’s blood concentration level may rise to a high level because the pancreas doesn’t produce enough insulin.
How can type 1 diabetes be controlled? (3)
- Avoid foods high in simple carbohydrates (e.g sugars)
- Take exercise after eating to use up extra glucose released in digestion
- Inject insulin into the blood at mealtimes making the liver remove glucose as soon as it enters the gut making it more effective.
What do insulin injection dosages depend on?
Level of activity and diet
Describe and evaluate a treatment for diabetes used in the past.
- Insulin was taken from pigs and cows and injected into diabetics.
- Advantage: saved many diabetic people’s lives
- Disadvantages: animal insulin isn’t the same as human insulin so can cause reactions, animals are killed, there isn’t enough insulin all the time.
Describe and evaluate two treatments for diabetes used now.
1) Genetically engineering bacteria to produce insulin
- Advantage: constant supply of insulin, no harm to creatures
- Disadvantage: ethical objections from some
2) Pancreas transplants
- Advantage: Normal life, more ease
- Disadvantages: rejection, infection
What are two methods that could be be used to treat diabetes in the future?
- Stem cell therapy
- Artificial pancreases
What does dialysis do?
It restores the concentration of dissolved substances in the blood to normal levels.
Describe the dialysis process.
- The person’s blood flows alongside a selectively permeable membrane (surrounded by dialysis fluid)
- This is permeable to ions, glucose, water and urea but not big molecules (e.g amino acids) - like kidney filters
- The dialysis fluid has the same concentration of glucose and ions and water as healthy blood - only excess ions and water and urea will diffuse across the barrier.
How does rejection occur?
Foreign antigens are attacked by the person’s antibodies
What are the two ways to prevent rejection?
- ‘Tissue-typing’, finding a donor with a tissue type (similar antigens) most closely matching the patient
- Immunosuppressant drugs (this can have serious side effects as immune system is lowered)
What are the disadvantages of kidney transplants? (5)
- Immunosuppressant drugs
- Waiting for a donor
- Waiting for a match tissue
- Risk of infection
- Dangers of operation
What are the disadvantages of dialysis? (3)
- Diet restrictions
- Long regular hours at the machine
- Blood clots
