kidney Flashcards
Homeostasis
it is the process by which the body adjusts to changes to keep essential internal conditions steady.e.g when body is too hot or too cold…
How does homeostasis work?
Many of the body’s systems work best under specific chemical and physical condition. To keep things in a steady state, the body uses a system of receptors and effectors. The receptors detect the rise or fall in temperature of the skin. The effectors then brings about the changes in the opposite direction to restore the equilibrium. keeping the body’s internal temperature at 37’C is an example of homeostasis
Negative feedback
Controlling water balance is an example of negative feedback, where one system is the reverse to another in order to maintain a steady state
Give examples of homeostasis
body maintenance of water content, temperature and composition of blood are examples of homeostasis
How does negative feedback mechanism work?
If a variable in the body becomes too low (e.g. pH, temperature) negative feedback mechanisms will rise to that variable and vice versa.
How does kidneys control the water content of the body? Use negative feedback in your answer.
Receptors in brain measure water potential of blood. Changes in water potential alter the amount of ADH (Anti Diuretic Hormone) released. This hormone then controls the amount of water ‘saved’ by the kidney and so not lost in the urine. This demonstrates negative feedback, since a reduction in water intake eventually causes greater saving of water and so ‘cancels out’ the original change.
When there is Too much Water in the Blood
- Receptors in your hypothalamus detect a decrease in salt concentration, no stimulus is sent to the pituitary gland.
- Less ADH is secreted into the blood.
- The collecting ducts of your kidneys become less permeable, so less water is reabsorbed.
- Your bladder fills with large quantity of dilute urine
When there is NOT enough Water in the Blood
- Receptors in your hypothalamus detect an increase in salt concentration. A stimulus is sent to the pituitary gland. Thirst is stimulated to encourage drinking.
- More ADH is secreted into the blood.
- The collecting ducts of your kidey become more permeable, so more water is reabsorbed.
- Your bladder is filled with a small quantity of concentrated urine.
Give two possible advantages of using a dialysis machine rather than having a kidney transplant.
It does not depend on the availability of a kidney for transplant/it should not challenge the patient’s immune system/drug treatment can go on through the
dialysis fluid entering the body
Give two possible disadvantages of using a dialysis machine rather than having a kidney transplant.
it is inconvenient – the patient must spend long periods on the machine/long-term treatment is very expensive
Explain why: protein molecules are not normally present in urine.
The protein molecules are too large to cross the filtration membrane and enter the urine
Explain why glucose molecules are not normally present in urine.
glucose molecules can cross the filtration membrane, but it is possible for them to be selectively reabsorbed and returned to the blood
Name organs for excretion
lungs, kidneys and skin
Name two functions of kidney
It’s a homeostatic organ, controlling the water and salt (ion) concentration in the body as well as an excretory organ, concentrating nitrogenous waste in a form that can be eliminated.
An athlete trained for two hours on a hot summer’s day. At the end of the training session, the athlete had a higher concentration of ADH in his blood than at the start of the training session. Explain why.
Training on a hot day means that much water will be lost in sweat/reduces the water potential of the blood/osmoreceptors in brain detect this change/more ADH is released to ‘instruct’ the kidney to recover more water from the urine.
Define the term excretion.
Excretion is the removal of metabolic waste, including urea, carbon dioxide and water of metabolism
Define the term egestion.
Egestion is the removal from the body of food materials that have not been digested and absorbed from the gut e.g dietary fiber.
State where in the body urea is formed.
In the liver
State when urea is formed from.
from excess amino acids (by the process
of deamination)
Suggest why the concentration of the urea in the patient’s blood rises between dialysis treatments.
Urea is still being formed but it is not being excreted
State two treatments which may help patient to prevent rejection of the transplanted kidney.
The patient may be treated with drugs which suppress the activity of their immune system, so that the body’s defences no longer attack the donor kidney/the donor kidney may be treated so that it has no antigens on its surface and so it is not recognized by the host defense.
Renal artery
blood with high urea concentration
Renal vein
blood with lowered urea concentration
Urea
Urea is produced in the liver but excreted from the kidney. It’s is removed by ultra filtration of the blood in the kidney, and expelled from the body in the urine.
Bladder
Storage of up to about 500cm3 of urine before expulsion from body
Sphincter
ring of muscle that controls flow of urine from bladder to urethra
Urethra
urine flow from bladder to outside
Cortex
contains the Bowman’s capsules in which ultra filtration of blood takes place
Medulla
Medulla contains loops of Henle and collecting ducts.
First coiled tubule (Proximal convoluted tubule)
here the useful solutes, glucose, amino acids and some minerals are selectively reabsorbed into the blood. Up to 90% of water is reabsorbed here.
Urine
is mainly water with concentrated urea and excess salts
Renal capsule
filtration of blood under high pressure to remove toxic urea. Unfortunately useful glucose, amino acids, salts and water also leave the blood.
Collecting ducts
kidney can reabsorb water from here and return it to the blood according to the body’s demand
Anti-diuretic hormone (Anti Urine) - also known as vasopressin is a powerful vasoconstrictor
When the hypothalamus detects that the blood plasma has a low water potential, it stimulates the pituitary gland to release ADH.
When ADH is released into the bloodstream, it causes constrictuion of blood vessels, raising blood pressure.
It then reaches the kidneys causing more water to be reabsorbed. Therefore water is conserved and the water potential of blood is increased.
Why is regulation of water potential important?
to prevent hydration or the bursting of cells
How kidneys work?
The kidneys contain millions of tiny filtering units called nephrons. 3 stages took place: ultra-filtration, selective reabsorption, and salt and water regulation.
Ultrafiltration
the blood from the renal artery is forced into the glomerulus under high pressure. Most of the water is forced out of the glomerulus and into the Bowman’s capsule, including all the small molecules like urea, salts and glucose.
The liquid filtered into the Bowman’s capsule is called glomerular filtrate.
The cup shape of the Bowman’s capsule allows the glomerulus to sit indide and allows high pressure to be maintained.
Selective reabsorption
in the Proximal convulted tubule useful substance such as glucose are reabsorbed into the blood, which runs very close by. The coiled-up tubule is long and folded to allow time for the useful substances to pass back into the blood.
Salt and water regulation
the collecting duct is where water is reabsorbed into the blood. The hairpin-shaped loop of Henle and collecting duct extend from the cortext to the medulla, allowing plenty of time for reabsorption of water and ions. Complex movements of ions and water across the loop result in the production of concentrated urine.
Starting from glomerulus, name the structures that a urea modulecule passes through on its way from blood to the bladder
Glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct, ureter, bladder
Glucose is filtered out of the blood in the kidney. Why is glucose not found in the urine of the healthy people?
In a healthy kidney all the glucose that is filtered out of the glomerulus is reabsorbed in the proximal convoluted tubule.
Name the hormone involved in the regulating water loss in the urine.
ADH (anti diuretic hormone)
How does an increase in ADH affect the color, concentration, and volumne of urine?
small volumne of dark-coloured, concentrated urine produced
Explain why blood protein is not normally found in urine.
Blood proteins are too large to pass out of the glomerulus into the Bowman’s capsule.
Explain why glucose is found is the filtrate but is not found in the urine.
glucose molecules can cross the filtration membrane, but it is possible for them to be selectively reabsorbed and returned to the blood by diffusion and active transport
Describe how you could use Benedict’s Reagent to test a sample of urine for the presence of glucose.
Heat a urine sample with Benedict’s Reagent; a change in colour to red/orange indicates that glucose is present
Suggest why protein appears in the urine of people with high blood pressure.
The high pressure damages the delicate glomerulus walls and allows large protein molecules to be forced through.
