B3.3 Homestasis NOT FINISHED Flashcards
What is homeostasis?
The maintenance of a constant internal environment
Why is homeostasis important?
If the conditions aren’t controlled in body, cells can become seriously damaged
What needs to be controlled in the body? (4)
Water content, ion content, body temperature, and blood glucose level
What are the 2 main waste products in the body?
Carbon dioxide and Urea
Why do waste products need to removed from the body?
Because they can cause damage to the body
How is carbon dioxide produced in the body?
It is a waste product of respiration in cells
Why is carbon dioxide removed from the body? And how is it removed?
It is toxic in high quantities and removed when you breathe out
How is Urea produced?
Proteins can’t be stored in the body - so excess amino acids are broken down into fats and carbs, which can be stored, this process produces urea as a waste product
Where is Urea produced?
In the liver
Why is Urea removed?
It is poisonous
Where is Urea found?
After being produced in the liver it is released into the bloodstream
How is Urea removed from the bloodstream?
The kidneys filter it out of the blood
Where is Urea stored before it is removed in urine?
In the bladder in urine
What are the main jobs of the kidneys? (3)
To remove urea, to adjust ion content and to adjust water content
How is water lost from the body? (3)
In urine, in sweat and in the air we breathe out - these factors are what water balance is between
What are the filtration units in kidneys called?
Nephrons
What are nephrons?
Tiny structures within the kidney that filter the blood - this is what produces urine
How many nephrons are found in each kidney?
Thousands
What are the 3 main steps of urine production?
Ultrafiltration, reabsorption and release of waste products
Where does the blood come from when entering the kidneys?
The renal artery
What happens in the renal artery? Where do the waste products go?
A high pressure builds up in the artery which squeezes water, urea, ions and sugar out of the blood into an area called the capsule at the start of the nephron
How does blood get into capsule?
The membrane between the artery and capsule acts like a filter preventing large molecules like proteins and blood cells from getting into the kidneys
What process in the production of urine involves active transport?
Reabsorption
What is reabsorbed from the production of urine? (3)
All the sugar (glucose), sufficient ions and sufficient water
What happens in the final step of the production of urine?
The remaining substances continue out of the nephron, into the ureter and down to the bladder as urine
How can people with kidney failure be kept alive? (2)
By having dialysis treatment, or by having a kidney transplant
What is dialysis treatment?
Where machines do the job of the kidneys
What is a kidney transplant?
Replacing the diseased kidney with a healthy one
What does the blood flow alongside in a dialysis machine?
A partially permeable membrane, that allows thing like ions and waste substances through but not big molecules like proteins, which is then surrounded by dialysis fluid
What does dialysis fluid contain? Why?
The same concentration of dissolved ions and glucose as healthy blood, so that useful dissolved ions and glucose won’t be lost from the blood during dialysis
What diffuses across the partially permeable membrane in dialysis? (3)
Waste products, and excess ions and water
What problems are there with dialysis? (5)
It’s not a pleasant feeling, it can lead to infections and cause blood clots, patients have to be careful on what they eat (e.g. they need to avoid eating too much of a particular ion), patients need to limit the amount of fluid they take in and dialysis machines are expensive to run
Why does rejection occur in kidney transplants?
Because the antigens on the donor kidney aren’t being recognised as part of the body so WBC produce antibodies to attach the donor kidney
How can rejection be prevented? (2)
By choosing a donor with a similar tissue type and/or by taking drugs that supress the immune system and reduce the production of antibodies
What are problems with kidney transplants (besides rejection)? (4)
There are long waiting lists for kidneys, even donors with matching tissue-type can still be rejected, the drugs taken to supress the immune system means that the patient is vulnerable to illness/infections and a kidney transplant is a major operation which can be risky
Why does the body temperature need to be kept at around 37°C?
Because this is the temperature at which enzymes in the human body work best
What a human’s ‘personal thermostat’?
The thermoregulatory centre - a part in the brain
How does the thermoregulatory centre monitor body temperature?
By receiving information from receptors
Where are the receptors found which send information on temperature to the thermoregulatory system? (2) What exactly do they measure?
Receptors in the thermoregulatory centre are sensitive to the temp. of the blood flowing through the brain, and receptors in the skin send information about skin temp. via nervous impulses
How does the body respond to your core body temp. being too hot?
The hairs on the skin lie flat, sweat is produced by sweat glands and the blood vessels supplying the skin capillaries dilate
What is vasodilation?
When they core body temperature is too high, the skin capillaries dilate (get wider) so more blood flows closer to the surface of the skin allowing heat to be transferred to the environment
How does sweat cool you down?
As sweat evaporates from the skin it removes heat
How do hairs on skin lying flat help to cool you down?
Because it prevents air from being trapped near the surface of the skin (as air is an insulator)
How does the body respond to your core body temp. being too cold?
Hairs on the skin stand up, no sweat is produced, blood vessels supplying blood to the skin constrict, and you shiver
How do hairs on skin lying flat help to keep you warm?
It traps air which is an insulator
What is vasoconstriction?
Blood vessels supplying blood to the skin constrict (get narrower) to reduce the skin’s blood supply, so less heat is being transferred to the surroundings from the blood
How does shivering help to keep you warm?
Shivering is just your muscles contracting, this contraction need respiration which releases energy to warm the body
How does glucose get into the body?
Through the food we eat
How is glucose used? (2)
The normal metabolism of cells removes glucose from the blood and so does vigorous exercise
What are changes in blood glucose levels monitored by?
The pancreas
What hormones does the pancreas release which help to control the blood glucose level? (2)
Insulin and glucagon
What does insulin do?
It decreases the blood glucose level when it gets too high
How does insulin decrease the blood glucose level?
It causes cells to take up more glucose from the blood
How is glucose stored?
It can’t be, so cells in the liver and muscles can take up glucose and convert it into a storage molecule called glycogen
What does glucagon do?
It increases the blood glucose level when it gets too low
How does glucagon increase the blood glucose level?
It causes the stored glycogen to convert back into glucose which enters the blood
What is type 1 diabetes?
A condition where the pancreas produces little or no insulin - blood glucose levels can get so high that they can die
How is type 1 diabetes controlled? (3)
By limiting the intake of food rich in simple carbs, by exercising regularly and by insulin therapy
What is insulin therapy?
Injecting yourself with insulin
What determines how many times you need to undergo insulin therapy in a day? (2)
It depends on how active they are and their diet
How is insulin extracted for insulin therapy? (3)
They normally come from the pancreas of pigs or cows, but now human insulin is made from genetic engineering
What are modern treatment options for diabetes? (3)
You can have a pancreas transplant, or, modern research into artificial pancreases and stem cell research is being developed
