Homeostastis Flashcards
Negative feedback
Receptors detect levels that are too low or too high, a response is caused to counteract change and restore levels to normal
What do we need to maintain at optimum levels?
Blood- glucose concentration, water concentration, pH
Temperature
Role of adrenaline
Secreted by adrenal glands during periods of stress/ exercise/ low blood glucose concentration
Binds to specific receptors of cell surface membrane on liver cells
Actives enzymes in glycogenolysis
Increases blood glucose concentration
The secondary messenger model
Demonstrated by adrenaline and glucagon abilities to stimulate glycogenolysis
Binds to specific receptors on cell surface membrane on liver cells
Activates adenylate cyclase
Converts ATP into cyclical AMP
cAMP activates protein kinase
Protein kinase activates a cascade of reactions that lead to the the hydrolysis of glycogen into glucose
Consequences of a blood glucose concentration that is too high
Decreases water potential of the blood
Causes water to move out of cells, down wp grad
Kidney unable to absorb all glucose- increases volume of water lost in urine- dehydration
Consequences of a blood glucose concentration that is too low
Not enough glucose to diffuse into cells and be used in respiration
Not enough ATP production to meet ATP demand
Used in processes such as active transport
Factors influencing blood glucose concentration
Eating carbohydrates- digestion- absorption- higher
Exercise- adrenaline- increased rate of respiration of glucose- lower
Type 1 Diabetes
Type 1- gene mutation, autoimmune disease, beta cells of istlets of langerhans no longer produce insulin.
Monitor glucose levels,
match regular injected dosage to need.
Eat regular carbs avoid sudden
Glucagon
Low blood glucose
Alpha cells
Increases b g levels
Insulin
High blood glucose concentration
Beta cells
Lowers b g levels
Process of ultrafiltration
Blood arrives from the renal artery directed through the afferent arteriole
The diameter of the afferent is wider than the efferent- producing hydrostatic pressure
Fluid and small molecules eg water glucose amino acids urea are forced out into the bow man’s capsule
Passing through capillary endothelium, basement membrane, podocytes
Large molecules such as proteins and red blood cells are too large to leave so remain in the blood
What occurs at the PCT?
PTC lined with epithelia cells
Na+ actively out of epithelial cells into capillary
Reduces Na+ conc, est con grad between lumen on PTC and epithelial cell
Na+ diffuse into Epithelial cell down con grad along with glu amino co-transport protein fac diff
Increased con of amino glu
Gluc amino diffuse into blood down con grad via facilitated diffusion through a channel protein
Lowers water potential in epithelial cell, water moves out reabsorbed into blood down wp g via osmosis
What happens at the loop of Henlé?
Na+ actively transported out of the ascending loop, water remains in filtrate as impermeable to water
Increasing the Na+ concentration of the medulla lowering water p
Descending - Water is reabsorbed into blood via osmosis down water potential gradient, lowering water potential
As travel down descending limb filtrate becomes more and more concentrated
Na+ diffuses into descending limb down conc grad, recycling them
What happens at the DCT?
Water is reabsorbed back into blood via osmosis down w p grad
Permeability of walls of DCT controlled by ADH
Where are changes in water potential detected?
By osmoreceptors in the HYPOTHALUMUS
