Homeostasis Flashcards
define homeostasis
the maintenance of a stable internal environment
what factors affect enzyme activity
increase in temp
increase in pH
decrease in temp
decrease in pH
control mechanisms process
receptors detect changes around the body
effectors carry out corrective measures in response to the change
the brain acts as a control centre
feedback loop informs the receptor of the changes to the system brought about the effector
negative feedback definition
when there is an increase/decrease from the set point
the opposite effect is instigated
produces a response that returns the value to the norm
positive feedback definition
a deviation from an optimum causes changes that result in an even greater deviation from the normal
what happens to the body if body temp is too low
enzyme-controlled reactions take place too slowly
due to lack of kinetic energy
what happens to the body if the body temp is too high
enzymes could be denatured
due to breaking of Hydrogen & Ionic bonds that hold the specific 3D tertiary structure
what happens if pH deviates
enzymes and other proteins will be denatured
important info about hormones
each hormone is chemically, structurally different
complementary to receptors
which hormone does an alpha cell produce
glucagon
which hormone does a beta cell produce
insulin
influence of insulin
high levels of blood glucose conc are detected by B cells
B cells release insulin to lower it
insulin binds to complementary receptors on target cells
increases no. glucose carrier proteins
activates enzymes to stimulate glycogenesis
influence of glucagon
low levels of blood glucose conc are detected by Alpha cells
Alpha cells release glucagon to increase it
glucagon binds to receptors on target cells
activates enzymes involved in the hydrolysis of glycogen to glucose
activates enzymes involved in gluconeogenesis
second messenger model
adrenaline and glucose bind to receptor
hormone receptor complex formed
activates adenylate cyclase
results in conversion of ATP to cAMP
cAMP activates protein kinases to allow for
glycogenolysis
what is diabetes caused by
failure of glucose homeostasis
type 1 diabetes
severe insulin deficiency due to autoimmune killing of β cells
type 2 diabetes
Insulin is produced
but the insulin receptors in the target cells are unresponsive
a lack of sensitivity to insulin
symptoms of diabetes
- High thirst due to osmosis of water from cells to the blood, which has a low water potential
- Large volumes of urine production due to excess water in blood
- Poor vision due to osmotic loss of water from the eye lens
structure of the kidney
medulla
cortex
fibrous capsule
renal pelvis
ureter
renal artery
process of osmoregulation
osmoreceptor cells in the hypothalamus detect fall in water potential
ADH is secreted into capillaries by posterior pituitary gland
ADH travels to kidneys in blood and increases permeability of cells of DCT and collecting duct
formation of glomerular filtrate
blood enters through renal artery
enters bowman’s capsule
afferent arteriole is wider than efferent arteriole
high hydrostatic pressure
pushes glucose,water,urea and mineral ions out the fenestrations
forms glomerular filtrate
How is urea removed from the blood?
Hydrostatic pressure
Causes ultrafiltration
Through basement membrane
Enabled by small size of urea molecule
Describe how ultrafiltration produces glomerular filtrate
High hydrostatic pressure
forces glucose, water, urea out
Pass through basement membrane
Protein too large to go through
Presence of fenestrations in capillary endothelium
Presence of podocytes
Explain how urea is concentrated in the filtrate
- Reabsorption of water by osmosis;
- At the PCT and descending LoH;
- At the DCT and CD;
- Active transport of ions
process of re-absorbance of water
Na+ are actively transported out of the ascending limb using ATP
Na+ ions re-enter the descending limb
lowering water potential
drawing water out of the permeable descending limb by osmosis
The water from the descending limb then enters capillaries returning to the blood
Distal convoluted tubule
make final adjustments to the water and salts that are reabsorbed
To achieve this, the permeability of its walls becomes altered under the influence of various hormones = osmoregulation
collecting duct
collecting duct is permeable to water and so water continues to move out by osmosis as the countercurrent multiplier
ensures there is always a water potential gradient along the entire collecting duct
