3.7 Homeostasis And The Kidney Flashcards
What is homeostasis ?
Maintenance of a constant internal environment
What does homeostasis maintain ?
pH, glucose concentration, core temperature and solute potential
What is the purpose of homeostasis ?
To protect cells and ensure reactions continue at a constant appropriate rate so cells function correctly
What is negative feedback ?
A change in a system produces a second change which reversed the first change
What are the stages of negative feedback ?
Input, receptor, coordinator, effectors and output
What is positive feedback ?
When an effector increases a change, movement away from the norm causes further movement away from the norm
What is excretion ?
The removal of metabolic waste made by the body
What are the functions of the kidney ?
Excretion and osmoregulation
What is osmoregulation ?
Homeostatic function that maintains concentrations of enzymes and metabolites enabling reactions within cells to occur at a constant and appropriate rate
What part of the nephron is found is the kidney cortex ?
Bowman’s capsule
What parts of the nephron are found in the kidneys medulla ?
Loop of Henle and collecting duct
What are the 3 layers of the kidney cortex ?
Capillary endothelium, basement membrane and podocyte cells
What occurs in the Bowman’s capsule ?
Ultrafiltration
What is ultrafiltration ?
Filtration under high pressure
Which arteriolar has a wider diameter ?
Afferent
What does the glomerular filtrate contain ?
Water
Glucose
Salts
Urea
Amino acids
Does the blood flowing from the glomerulus to afferent arteriole have a low or high water potential ?
Low
What happens in the proximal convoluted tubule ?
Selective re absorption
What is selective reabsorption ?
The uptake of specific molecules and ions from the glomerular filtrate in the nephron back into the blood stream
What are some features if the proximal convoluted tubule ?
Long
Wide
Microvilli= large surface area
Lots of mitochondria
What does the loop of Henle create in the medulla ?
Concentration gradient
What is the loop of Henle known as ?
Counter current multiplier
Which limb of the loop of Henle is permeable ?
Descending
Which limb of the loop of Henle is impermeable ?
Ascending
What is the receptor in osmoregulation ?
Hypothalamus
What is the coordinator in osmoregulation ?
Hypothalamus
What is the effector in negative feedback ?
Posterior pituitary gland
Where is ADH released from ?
Posterior pituitary gland
What does ADH do ?
Increase permeability of cells distal convoluted tubule and collecting duct = increased water reabsorption
What is decreased water potential of blood caused by ?
Reduced water intake
Sweating
High salt intake
What does kidney failure cause ?
The body to be unable to remove urea so concentration reaches toxic levels and metabolic reactions and compromised.
What are the causes of kidney failure ?
Diabetes
High blood pressure
Autoimmune disease
Infection
Crushing injury
What are the 2 types of treatment for kidney failure ?
Transplant
Dialysis
What are the 2 types of dialysis ?
Haemodialysis
Continuous ambulatory peritoneal dialysis (CAPD)
What is transamination ?
An enzyme catalysed reaction that transfers an amino group to an alpha keto acid making an amino acid
What do aquatic organisms excrete ?
Ammonia as it’s extremely soluble in water
What do birds, reptiles and insects excrete ?
Uric acid, insoluble in water and non toxic so conserves limited water stores
What do mammals excrete ?
Urea
What does a longer loop of Henle allow ?
More opportunity to pump ions into the medulla
What are the 2 types of nephrons ?
Cortical
Juxtamedullary
What are the features of a cortical nephron ?
Short loop of Henle
Diluted urine
What are the features of a juxtamedullary nephron ?
Long loop of Henle
Concentrated urine
Water is conserved
What is metabolic water ?
Water produced from the oxidation of food reserves
