Kidneys and homeostasis Flashcards
What is homeostasis?
Mechanisms in which a constant internal environment is maintained
Describe the homeostatic mechanism
1) Stimuli detected by coordinator
2) Message sent to effector
3) Effector returns conditions to normal
(negative feedback loop)
What happens when high blood glucose is detected?
-Pancreas releases insulin, converting glucose to glycogen which is stored in liver
What happens when low blood sugar is detected?
Pancreas releases glucagon, converting glycogen into glucose
What is excretion?
Elimination of Nitrogen waste
What happens to amino acids?
-They are deaminated in liver, forming ammonia
-Ammonia converted to urea
What are the steps of excretion?
-Ultrafiltration
-Selective reabsorption
What are the three types of pressure in the glomerulus?
-Glomerular pressure (out)
-Osmotic pressure (in)
-Capsular pressure (up)
What molecules move from glomerulus to Bowman’s capsule?
-Glucose
-Water
-Amino acids
-Urea
-Inorganic ions
What molecules are too big to move from glomerulus to Bowman’s capsule?
-Proteins
-Red blood cells
What are the three barrier membranes?
1) Endothelial capillary membranes
2) Basement membrane
3) Podocytes
Describe endothelial capillary membrane
Has tiny gaps to allow dissolved substances through
Describe the basement membrane
Network of collagen fibres and glycoproteins, acts as filter (damaged by hypertension)
Describe podocytes
Specialised cells with finger-like projections (major processes), ensure filtration slits between cells
What is reabsorbed in the proximal convoluted tubule?
-All glucose and amino acids (Cotransport)
-Most mineral ions (active transport)
-Most water (osmosis)
-Some filtered proteins and urea (diffusion)
Describe how a Sodium concentration gradient is maintained in the proximal convoluted tubule
1) Sodium actively transported from lumen of PCT to surrounding cells and then into blood (cotransport)
2) Sodium diffuse out of PCT
How is the water potential gradient maintained in the loop of henle?
-Sodium and Chloride are actively transported out of ascending limb to tissue fluid
-Lowers water potential of tissue fluid
-The descending limb is permeable to water, so water moves down water potential gradient to medulla
-Water carried away by Vasa Recta
How is ADH released?
-Osmoreceptors in hypothalamus detect drop in blood water level
-Cells lose water and shrink, stimulating neurosecretory cells
-These cells are neurones which produce ADH and sends it down axon to post/pit
-When cells are stimulated they send action potentials and cause ADH to be released
How does ADH affect the collecting duct?
-ADH in blood binds to complimentary receptors in cell surface of CD
-This causes aquaporins to incorporate into plasma membrane from within cytoplasm
-Water moves out of CD and back into hypertonic tissue fluid
What are the symptoms of Kidney failure?
-Tiredness/weakness
-Bubbly/foamy urine
-Fluid accumulation
-Muscle cramps
What are the treatments of kidney failure?
-Medication to control blood potassium and Calcium levels (stops buildup and bone damage)
-Lower protein diet (lowers plasma protein conc)
-Drugs to reduce blood pressure
-Dialysis
-Kidney transport
How does haemodialysis work?
-Counter current system with blood and dialysis fluid (ensures diffusion gradient)
-Dialysis fluid contains optimal glucose, amino acids, water, and ions
What are the benefits of peritonial dialysis?
-Can be carried out at gome
-Less diet and fluid restrictions
What are the disadvantages of peritoneal dialysis?
-Needs to be carried out every day
-Catheter can be upsetting
-Risk of peritonitis
