Topic 4 - Excretion and Homeostasis Flashcards
What is excretion?
Excretion is the removal of toxic materials, waste products of metabolism and substances in excess of the requirements of living organisms.
What is metabolism?
Metabolism is a chemical process which occurs within an organism e.g. respiration or photosynthesis.
Sort this list into excretory and non excretory products:
1. Urea
2. Earwax
3. Glucose
4. Water
5. Snot
6. O2
7. CO2
8. Faeces
9. Tears
10. Ions
EXCRETORY:
- Urea
- Water
- O2
- CO2
- Ions
NON-EXCRETORY:
- Earwax
- Glucose
- Snot
- Faeces (Egested)
- Tears
What are the three excretory organs?
The skin, lungs and kidneys
- What is the job of the kidney?
- What substances will urine contain?
- To filter products from the blood, which will become urine.
- Urine will contain urea, water and mineral ions, along with some other substances
- What are the three processes that filters these products?
- What carries out these processes?
- Ultrafiltration, Selective reabsorption of glucose, Reabsorption of water
- The nephrons carry out these processes
Label this diagram:
What are the functions/purposes of the:
1. Vena cava
2. Aorta
3. Renal Artery
4. Renal Vein
5. Ureter
6. Bladder
7. Urethra
8. Urethral Sphincter
- Carries filtered & deoxygenated blood away from kidneys
- Carries unfiltered & oxygenated blood towards the kidneys
- Takes oxygenated blood between the aorta and kidneys
- Takes deoxygenated blood between the kidneys and vena cava
- To transport urine from the kidney to the bladder
- To store urine until it can exit the body
- To excrete urine out the body
- A ring of muscle that controls access to the urethra from the bladder
- What is the kidney packed with (That carry out reabsorption)?
- Where are these located?
- The kidney is packed with around a million structures called nephrons
- The nephrons start in the cortes of the kidney and loop down into the medulla and back to the cortex
What do the nephrons regulate? What do they remove from the blood?
The nephrons regulate the level of water and salts, and remove urea from the blood.
Label the diagram:
- Where does ultrafiltration occur?
- What does this process involve?
- Ultrafiltration occurs in the glomerulus (Which sits inside the Bowman’s capsule)
- The glomerulus has thin walls, which allows small molecules, wastes and fluid (Mostly water) to pass into the proximal convoluted tubule (PCT) - This works similarly to a sieve. Larger molecules such as proteins and blood cells stay in the blood as they are too big for the small walls (Sieve) of the glomerulus
- Where does the selective reabsorption of glucose occur?
- What does this process involve?
- The selective reabsorption of glucose occurs in the proximal convoluted tubule (PCT)
- Glucose is the first component to be reabsorbed in the PCT by active transport (Against the concentration gradient). PCT cells have lots of mitochondria to release the energy for this to take place.
This can only take place in the PCT as it is the only place in the nephron which has the gates that facilitate the active transport of glucose.
- Where does the reabsorption of water and salts occur?
- What does this process involve?
- The reabsorption of water and salts occurs in the loop of Henle
- As the filtrate drips through the loop of Henle, salts are reabsorbed back into the blood by diffusion (high to low concentration)
As salts are reabsorbed back into the blood, water follows by osmosis (as the salts lower the water concentration in the blood)
- Where is remaining water absorbed?
- Under what circumstances would the body reabsorb water here?
- Remaining water is reabsorbed in the Collecting Duct
- This is only if the body needs any extra water, usually if you are dehydrated - more water is reabsorbed if the water concentration in the blood is lower. (And vice-versa)
- What controls how much water is reabsorbed in the collecting duct?
- Where is this produced?
- The hormone ADH (Antidiuretic Hormone)
- AHD is produced in the pituitary gland
- When is more ADH released?
- How does more ADH cause more water to be absorbed, how does this affect urine?
- More ADH is released when there isn’t enough water in the blood (Water concentration in blood is low)
STEPS:
1. ADH causes the walls of the collecting duct to become more permeable to water
2. More water is reabsorbed into the blood
3. Less volume of urine is produce (More concentrated)
What would happen if the body was overhydrated?
- Less ADH is produced
- Collecting duct walls become less permeable to water
- Less water reabsorbed into body
- More urine produced (Less concentrated)
Step by step of what happens if water concentration in blood is low/high.
- What is dialysis?
- How does dialysis work?
- Dialysis is a method to remove waste products for patients with kidney failure
- Dialysis uses diffusion to draw urea and other unwanted substances out of the blood. Patients typically need dialysis treatment multiple times per week.
What are 3 advantages and disadvantages of kidney transplants compared to dialysis?
ADVANTAGES:
1. The patient can return to a normal lifestyle, instead of having to go into the hospital multiple times a week
2. A dialysis machine will be available for other patients if someone has had a kidney transplant
3. Dialysis machines are expensive to buy and maintain
DISADVANTAGES:
1. Transplants require a suitable donor, with a good tissue match, it is hard and a long process to find a suitable donor
2. The operation is very expensive
3. There is a risk of the new kidney being rejected by the body- expensive immunosuppressive drugs have to be used, but these make the body more easily ill.
What detects the water concentration of the blood?
Osmoreceptors in the hypothalamus
- What happens if the body temp is above 40°C for a significant time? What will happen to enzymes?
- What happens if the body temp is below 35°C for a significant time? What will happen to enzymes?
- The body will suffer from heatstroke, enzymes will denature and you will no longer be able to carry out metabolic reactions.
- The body will suffer from hypothermia, enzymes will work slower and slower, you will no longer be able to carry out metabolic reactions.
What is maintaining temperature within a narrow range an example of?
Maintaining temperature within a narrow range is an example of homeostasis
Mammals and birds are ‘warm-blooded’, or ___/___. This means that despite external changed they maintain their body temperature at ___
Mammals and birds are ‘warm-blooded’, or homeotherms/endotherms. This means that despite external changed they maintain their body temperature at 37°C.
- How do mammals and bird generate heat?
- Why is being a homeo/endo therm an advantage?
- By using forced respiration
- This is an advantage as it means a homeotherms metabolism does not slow down in a cold environment
Step by step of what happens if blood glucose levels are low/high.
What is a hormone?
A hormone is a chemical messenger produced by a gland and carries in the bloodstream, which alters the activity of specific target organs.
What are 6 differences between hormonal and nervous communication?
- Nervous is an electrical message, hormonal is a chemical message
- Nervous is transmitted through nerve cells/neurons, hormonal is transported in the bloodstream
- Nervous communication is transmitted quicker, hormonal is transmitted slower
- Nervous has a shorter response, hormonal has a longer response
- Nervous has a localised response, hormonal has a widespread response
- Nervous has a permanent effect, hormonal has a reversible effect
What are three ways that the skin regulates body temperature, how do each of these work?
- Sweating - The body releases water to cool you down
- Vasodilation - The body expands blood vessels so they flow nearer to the skin’s surface, and radiate heat to the environment, which cools you down
- Vasoconstriction - The body shrinks blood vessels so they flow further from the surface of the skin and do not radiate heat energy into the environment, this keeps you warmer.
What are two more methods the body regulates body temp when it is cold, how do they work?
- Erect Hairs - Hairs on the skin stand on end, which traps a layer of air around the skin, which acts as a very good insulator and stops you losing too much heat
- Shivering - Quick muscle contractions, which generates heat energy
