The Kidneys Flashcards
What is osmoregulation?
The maintenance of the osmotic potential in the tissues of living organisms
What is the liver and kidneys involvement in homeostatic control?
-The liver breaks down excess amino acids and removes toxins from the blood
-The kidneys remove these from the blood
What is deamination?
Breakdown of amino acids
What do the kidneys do?
-Control the water potential of blood
-Filter blood by removing unwanted or excess products as urine
What products do the kidneys remove and reabsorb?
Remove:
-Urea
-Excess ions and water
Reabsorb:
-Glucose
-Dissolved ions
-Some water
What is the general structure of the kidneys?
-Fibrous capsule = membrane which protects the kidney
-Cortex = light coloured outer region
-Medulla = darker coloured inner region
-Ureter = carries urine to the bladder
-Renal artery = supplies kidney with oxygenated blood
-Renal vein = returns blood to the heart from kidney
What are the two main types of nephrons?
-Cortical nephron
-Juxtamedullary nephron
What is the cortical nephron?
-85% of human nephrons
-Mainly found in renal cortex
-Have a loop of Henle that only just reaches into the medualla
What is the juxtamedullary nephron?
-Have a long loop of Henle that penetrates right through the medulla
-Efficient at producing concentrated urine
What is ultrafiltration?
-Blood is filtered to form filtrate
-Everything small enough leaves e.g. water, urea, glucose, salt, hormones
-Blood cells and proteins are too large to leave
What happens at the proximal convoluted tubule (PCT)?
-Selective reabsoption e.g. glucose is absorbed back into the blood
How are cells in the proximal convoluted tubule (PCT) adapted?
-Microvilli to increase surface area
-Lots of mitochondria to provide ATP for active transport
What does the loop of Henle do?
Acts as a counter current multiplier to increase the reabsorption of water
What happens at the descending limb?
-Permeable to water
-Water moves out by osmosis
What happens at the ascending limb?
-Impermeable to water
-Water can’t leave
-Sodium and chloride ions are moved out by active transport
-This increases the concentration of medulla
What happens at the distal convoluted tubule (DCT)?
-Permeable to water
-Permeability varies with ADH
-Balances water in the body
What happens at the collecting duct?
-Permeable to water
-Permeability varies with ADH
-Water moves out the collecting duct down the water potential gradient
What is anti diuretic hormone (ADH)?
-Used in dehydration
-It is a chemical messenger released from gland and transported in bloodstream
-If ADH is released, urine is highly concentrated and volume is lower
How does ADH work?
-Osmoreceptors in the hypothalamus monitors water content of blood and how much ADH should be released from the pituitary gland
-ADH joins to receptors on collecting duct, making it more permeable to water
-Water leaves and moves to blood
What is diabetes insipidus?
-Individuals produces large volumes of very dilute urine
-Happens when people don’t produce any/little ADH or kidneys don’t respond to it
-Makes the collecting duct and DCT permanently impermeable to water
-Treated with drugs to replace ADH
What happens when there is fluid intake?
-Osmoreceptors in the hypothalamus detect an increase in blood water levels
-Pituitary gland releases less ADH into the bloodstream
-ADH decreases permeability of collecting duct so less water is reabsorbed
-Produces large volumes of dilute urine
What happens when there is no fluid intake/sweating?
-Osmoreceptors in the hypothalamus detect a decrease in blood water levels
-Pituitary gland releases more ADH into bloodstream
-There is more ADH so permeability of collecting duct increases and more water is reabsorbed
-Produces a small volume of concentrated urine
What is an endotherm?
-Rely on their own metabolism to provide warmth
-Can survive in most environments
-Often have much higher metabolisms than ectotherms so need to eat more to supply metabolic needs
e.g. mammals and birds
What is an ectotherm?
-Rely heavily on their environment to control their body temperature
-Often require less food as they have lower metabolisms
How are changes in body temperature controlled?
Negative feedback
What is the role of the hypothalamus?
-Acts as a thermostat
-Receives impulses from sensory neurones from hot or cold thermoreceptors in the skin
-Processes information in the thermoregulation centre
-Sends information as electrical impulses via motor neurones to effectors to correct body temperature
What is an effector?
Either muscles or glands that bring about a response
-Skin
-Blood vessels
-Skeletal muscles
What is piloerection/pilorelaxation?
-Erector muscles in the skin cause hairs to stand on end
-This causes air to be trapped for insulation
What is vasoconstriction?
Capillaries constrict, arteriovenous shunt shuts, reducing blood flow to the skin to avoid heat loss
What is vasodilation?
Capillaries dilate, arteriovenous shunt shuts, increasing blood flow to the skin to increase hear loss
What does sweating do?
-Sweat is produced when body is too warm
-When sweat evaporates it takes heat energy with it to cool the skin
What does shivering do?
-Muscles contract and relax quickly when cold
-Some of the energy produced in respiration warms up the body
What is the adaptation of the kangaroo rat?
-Extremely long loops of Henle allowing water to be reabsorbed efficiently
-Produces small volumes and highly concentrated urine
