Homeostasis and The Kidney (DONE) Flashcards
What is homeostasis?
The maintenance of
a constant internal environment
Describe the negative feedback loop
(4 marks)
- Change to the normal conditions/deviation
- Stimuli detected by receptors, which pass on the message to the control centre
- Control centre sends message to effector
- Effector returns the conditions to normal
What are the functions of the kidney?
(2 marks)
- Excretion, which is the elimination of waste products (N-containing)
- Osmoregulation, which is the control of water content and solute composition of body fluids
Draw a diagram of the excretory system
(5 marks)
The diagram should include
- Vena cava and Aorta
- Renal veins and arteries
- Ureter
- Bladder
- Urethra
What is the function of the renal vein, renal artery and ureter in the excretory system?
- Renal vein removes carbon dioxide and has a lower conc of urea
- Renal artery supplies oxygen and glucose and has a high conc of urea
- Ureter transfers urine to the bladder
Draw the gross structure of the kidney
(4 marks)
Diagram should include:
- Cortex
- Medulla
- Pelvis
- Ureter
What is the functional unit of the kidneys and what/where is its components located?
(7 marks)
The nephron
- The glomerulus, Bowman’s capsule, proximal/1st convoluted tubule and distal/2nd convoluted tubule are in the cortex
- The loop of Henle and collecting duct are in the medulla
Describe the hazards, risk and control measures when carrying out a kidney dissection.
Hazard - Scalpels are sharp
Risk - When slicing into kidney there is a risk of cutting or piercing the skin
Control measure - Cut away from the body onto a white tile
Describe briefly how excretion of waste products, such as urea in the form of urine occur.
(5 marks)
- Blood enters the kidney through the renal artery/afferent arteriole (short and wide leading to a low resistant input pathway) at high pressure, into the capillaries in the cortex (glomerulus)
- Ultrafiltration, which filters out small molecules (urea, glucose, water, amino acids, inorganic ions) into the bowman’s capsule into the nephron
- Selective reabsorption in which amino acids, glucose and vitamins are reabsorbed back into the bloodstream
- Substances to be excreted pass along the tubules and ureter and reach the bladder to be disposed of as urine
- Filtered blood passes out of the kidneys throug h the renal vein
Describe the adaptations of cells within the proximal convoluted tubule that allows for selective reabsorption.
(2 marks)
- Microvilli/Brush border > provides large surface area for simple diffusion and transport proteins (channels,carriers)
- Many mitochondria for ATP synthesis for active transport
What is reabsorbed back into the blood from the proximal convoluted tubule, in what quantity and by what means.
(4 marks)
- All glucose and amino acids by co-transport
- Most mineral ions by active transport
- Most water by osmosis
- Some proteins and urea by diffusion
Describe the method of selective reabsorption in the proximal convoluted tubule.
(6 marks)
- Na⁺ are actively transported out of lumen of PCT into blood via Na/K pump
- This sets up [gradient] causing Na⁺ to diffuse out of the PCT
- Na⁺ enter by carrier proteins, which also carry another molecule with Na⁺ (co-transport)
- Amino acids and glucose move out by facilitated diffusion into blood with Na⁺
- Water moves down the water potential gradient into blood via osmosis
- Urea is reabsorbed as it is non-polar and can diffuse across membranes
What is the function of the loop of Henle?
Lowers the water potential gradient of the medulla/create a water potential gradient
Describe the changes in permeability along the loop of henle.
(9 marks)
DESCENDING LIMB
- Impermeable to ions, but permeable to water
- Surrounded by salty tissue fluid and thus water moves out of the tubule by osmosis down a water potential gradient
- The filtrate gets more concentrated as it descends down
- The most negative water potential is at the base of the loop
ASCENDING LIMB
- Impermeable to water, but permeable to ions
- Ions and are actively transported into tissue fluid of medulla
- The filtrate becomes more dilute
Describe the counter-current adaptation in the loop of Henle
(4 marks)
- Na⁺ are actively transported out of the ascending limb into tissue fluid
- This lowers water potential of the tissue fluid in medulla
- Descending limb is permeable to water, so water moves down the water potential into medulla via osmosis and is carried away by the vasa recta
- The longer the loop, the greater concentration gradient between filtrate and tissue fluid
