Homeostasis & Kidney Flashcards
What is homeostasis
The maintenance of constant or steady conditions within the body
Ultimately, why is it so important that conditions such as water potential, pH and temperature remain constant inside our bodies and do not fluctuate too much
It is important that enzymes that control our cell reactions do not denature
What are the three main components of homeostatic mechanisms?
->Sensors or receptors-detect the change away from the set point
->Corrective mechanism- effectors bring about responses to return the factor to its set point
->Negative feedback- prevents over correction of the factor by switching off the corrective mechanism
What are the two main roles of the kidney
-EXCRETION- the removal of the waste and toxic products of metabolism i.e urea and creatine
-OSMOREGULATION-maintains the body’s water potential at a constant optimal level
Name the functional units of the kidney and say where they are found
Nephrons-extend from the cortex into the medulla
Label the kidney
See notes
Label the nephron
See notes
What 2 processes does exertion of the urine involve
Ultrafiltration and reabsorption
What is ultrafiltration and where does it occur?
The filtering of small molecules, under pressure, from the blood in the glomerulus into the Bowman’s Capsule
What is the significance of the afferent arteriole being wider than the efferent arteriole?
The builds up a HYDROSTATIC PRESSURE to help force the small molecules, such as water, urea, amino acids and glucose from the glomerulus into the Bowman’s Capsule
What substances will not be present in the filtrate?
Red blood cells, white blood cells, platelets and plasma proteins which are too large to fit through the basement membrane of the glomerulus
Describe the three parts of the filter system
-Squamous endothelium of glomerular capillaries: a porous, coarse filter
-Basement non-porous membrane of glomerular capillaries:is a fine filter so determines what is in the filtrate
-Podocyte cells of Bowman’s Capsule wall: porous’ coarse filter
What is the equation for water potential and what is the rule?
Y=Yp + Ys
Water always moves from the higher (or less negative) to the lower (or more negative) water potential
How is net filtration force worked out for ultrafiltration?
It is the difference between water potential in the glomerulus and water potential in the Bowman’s Capsule
What gets reabsorbed into the vasa recta at the proximal convoluted tubule?
-65% of the water (i.e most of the water absorption)
-all of the glucose, amino acids, salts and vitamins
By what means are substances reabsorbed?
-active transport and facilitated diffusion
-pinocytosis for very small proteins
-osmosis for water
Which substances are selectively reabsorbed into the vasa recta by active transport?
Salt, glucose and amino acids
Some urea ends up diffusing down its concentration gradient from the proximal tubule into the vasa recta. So how are we still able to excrete urea efficiently?
The urea left in the proximal tubule is actually highly concentrated due to the fact that 65% of the water has been osmotically reabsorbed
What type of cells line the proximal tubule and give three fractures they have for active uptake and facilitated diffusion
Cuboidal epithelium
-mitochondrial to provide ATP
-microvilli and basal invaginations to increase SA
-close proximity to capillaries
What is the key role of the LOOP OF HENLE?
The Loop of Henle is important for creating a high solute concentration or very negative solute potential in the tissues of the medulla
What is the significance, especially to land swelling organisms, of the medulla having a high solute concentration and thus providing a salt gradient?
It means that water can be reabsorbed osmotically from the collecting duct, distal convoluted tubule and descending limb of the Loop of Henle, creating a hypertonic urine and thus conserving water.
How is having the region of high solute concentration achieved?
Sodium and chloride ions (SALT) are actively pumped out of the ascending limb of the Loop of Henle into the tissues of the medulla
What term is used to describe the processes by which water potential and salt potential of body fluids is regulated?
Osmoregulation
Name the hormone involved in osmoregulation and say where it acts
ADH (anti diuretic hormone) and it acts on the aquaporin channels of the collecting ducts and distal tubules
Where is a change in water potential/solute potential of the body fluids detected?
It is detected by osmoreceptor cells in the hypothalamus of the brain
Where is ADH produced?
The hypothalamus of the brain
Where is ADH stored?
The pituitary gland in the brain
What stimulates ADH release?
A decrease in water potential or solute potential (hypertonic plasma)
What effect, exactly, does ADH have on the collecting ducts and distal tubules
ADH makes the membranes of the collecting ducts and distal tubules more permeable (by opening aquaporin channels) allowing more water to be reabsorbed
