Homeostasis Flashcards
(24 cards)
What is Homeostasis?
The maintenance if constant conditions in the body
What are the 3 main features of every homeostatic response?
Control system
Corrective mechanism
Negative feedback system
What does the control system do?
Detects any deviation from normal using sensors (receptors)
What does the corrective mechanism do?
Beings about changes resulting in the regulation of this factoe
What does the negative feedback system do?
Stops the correct mechanism when conditions are back to normal, and prevents over-correction
What are the roles of the kidney?
Excretion and osmoregulation
What is excretion?
The removal of toxic waste products of metabolic processes eg urea and creatine
What is osmoregulation?
The control of water potential of bodily fluids.
Describe the structure of Bowman’s Capsule in the nephron
Between the inner and outer walls there’s a capsular space
- outer walls - unspecialised epithelial cells
- inner wall as - has pod of two, which have gaps allowing substance to ‘leak’
Blood enters via wide afferent arteriole and leaves via narrow efferent arteriole
Describe the structure of the Proximal Convoluted Tubule in the nephron
Cubicle epithelial cells, which contain mitochondria, microvilli and folding.
Describe the structure of the Loop of Henle in the nephron.
Descending limb - permeable or water
Ascending limb - impermeable to water
Describe the structure of the Distal Convoluted Tubule and Collecting Duct.
Cuboidal epithelium
Permeable to water with ADH
Describe the structure id the Filter.
Squamous endothelium of capillaries
Basement membrane - effective filter
Inner wall of bowman’s capsule - podocytes with slits
What is ultrafiltration?
A process which relies on high hydrostatic pressure
During ultrafiltration, where does the high hydrostatic pressure come from?
- renal arteries are short and close to the heart
- coiling of capillaries restricts blood flow
- efferent arterials is narrower than the afferent arteriole, creating a bottle neck.
How does the filtration force occur?
Water potential within the glomerus capillaries (plasma) must exceed the water potential within the Bowman’s capsule (filtrate).
What is back pressure?
Filtrate can cause pressure to build in capsular space and force liquid back into the glomerus
What die arge glomerate filtrate consist of, and why?
Similar to blood except, plasm, proteins and blood cells as ther are too large to pass through the basement membrane.
Where does selective reads option occur?
Proximal convoluted tubule
What molecules are selective reabsorbed?
Active transport of salt, glucose and amino acids from the filtrate, into the blood, as they are useful
How does selective re absorption affect the water potential of blood?
Lowers the water potential, causing water to be reabsorbed by osmosis into capillaries
What happens in the descending limb of the loop of henle?
As filtrate moves down, it’s carried through interstitial tissue with increasing solute concentration. This causes water to be drawn out by osmosis, then the remaining filtrate becomes more concentrated. Water loss continues until the concentration of descending limb and interstitial tissue are equal.
What happens in the ascending limb of the loop of henle?
Sodium and chloride ions are pumped into interstitial tissue by active transport, causing the filtrate to be less concentrated.
How does osmoregulation correct a decrease in water potential of blood, using a negative feedback system?
- osmoreceptors in the hypothalamus detects decrease in water potential
- send impulse to pituitary gland, releasing ADH into the blood and travels to the kidney
- collecting ducts become more permeable to water
- more water absorbed by osmosis
- very little, concentrated urine produced
- increases water potential of blood
- as water potential returns to normal, the amount of ADH released returns to normal.
