Homeostasis Flashcards
what is homeostasis?
physiological control systems that maintain a constant internal environment
describe positive feedback
a response that amplifies a change eg) voltage gated channels Na +
describe negative feedback
receptors detect change away from normal/optimum and affectors return to normal/ optimum eg) blood temp.
what cells secrete insulin?
beta cells in the islets of Langerhan
what is the role of insulin?
to decerase bllod sugar conc.
describe 3 ways insulin decreses blood sugar conc.
binds to liver and muscle causing increased permeability to glucose……more glucose is absorbed by facilitated diffusion………… glycogenesis…..increased rate of respiration
what cells secrete glucagon?
alpha cells in the islets of langerhan.
how does glucagon restore normal blood sugar level?
gluconeogenesis - non carbs are converted to glucose……glycogenolysis…..decrease rate of respiration.
what is glycogenesis?
the conversion of glucose to glycogen
what is glycogenolysis?
the hydrolysis of glycogen into glucose
what is gluconeogenesis?
the conversion of non carbs eg)lipids/ amino acids into glucose
which hormone decreases blood sugar levels?
Insulin
which hormone increases blood sugar levels?
glucagon
when is glucagon secreted?
when the blood sugar is low
when is adrenaline secreted?
low
when is insulin secreted?
when the bloood sugar is HIGH
where does glucagon attach to receptors?
liver
where does adrenaline attach to receptors?
liver
where does insulin attach to receptors?
liver and muscle
what are the mechanisms of glucagon?
decreases rate of respiration, glycogenolysis, gluconeogenesis
what does adrenaline activate?
glycogenolysis, secretion of glucagon
what does adrenaline inhibit?
glycogenesis, and insulin secretion
what are the mechanisms of insulin?
icrease rate of respiration, glycogenesis, increasing cell permeability to glucose
how does insulin increase cell permeability?
glucose carrier molecules are in vesicles in L + M cells, insulon binds with specific receptors on the cell membrane, causing the fusion of the vesicles with the cell membrane, carrier proteins join the cell membrane (fluid mosaic), so glucose is absorbed by fac dif.
Define diabetes
an illness where blood glucose levels are not fully controlled
Describe Hyperglycaemia
dangerously high blood glucose concentration
Describe hypoglycaemia
dangerously low blood glucose concentration
What causes Type I diabetes
immune system destroys B cells on the Islets of Langerhan so cannot make insulin
What age does Type I diabetes affect?
Children and adolescents
What affect does Type I diabetes have on blood glucose concentration
rise after eating carbohydrates
hyperglycaemia - stays high
glucose present in urine
how can we treat Type I diabetes?
- Insulin injections/ pump
- avoid sugars
- eat at regular intervals
- regular exercise
What causes Type II diabetes?
Obesity/ lack of exercise
B don’t make enough insulin or liver and muscle stop responding to insulin
What age does Type II affect?
adults and elderly
What is the affect of Type II on blood glucose conc?
hyperglycaemia
What is the treatment for Type II diabetes/
- eat healthy, lose weight, regular exercise
- drugs - which increase sensitivity to insulin, produce more insulin
- insulin injections
describe how secondary messengers aid Glycogenolysis.
- The hormone (first messenger) eg) adrenaline or glycogen is complementary to the receptor protein on the target cell
- The enzyme Adenyl Cyclate converts ATP to cAMP
- cAMP activates protein kinase A by altering the tertiary structure
- cAMP is the secondary messenger
What are the 2 parts of the kidney?
medulla and the cortex
Describe the process of ultrafiltration
takes place in between the capillaries and the bowmans capsule
high hydrostatic pressure forces small molecules out to form the filtrate
What is the larger capillary entering the glomelurus?
Afferent arteriole (lArge)
What is the smaller capillary entering the glomelurus?
Efferent arteriole
What three layers are the small molecules filtered through between the blood and the Bowman’s capsule?
capillary membrane, basement membrane, podocyte
Define selective reabsorbtion
useful products are reabsorbed by the nephron from the glomerular filtrate.
Describe the process of selective reabsorption
Ultrafiltration makes glomerular filtrate
capillaries wrap around nephron and useful substances are reabsorbed into the blood
Proximal Convuluted Tube (PCT) absorbs most of the molecules (including water)
How is the PCT adapted for reabsorption
microvilli increase SA for absorption
How are Glucose and Amino acids reabsorbed
Facilitated diffusion
How is Urea reabsorbed
simple diffusion
How is water reabsorbed?
osmosis
What is reabsorbed by Active transport using ATP?
glucose, amino acids, and ions
describe what happens at the ascending limb of the loop of Henle (stage one) `
Na+ and Cl- are pumped out
This decreases the water potential of the medulla
water cannot move out of the ascending limb because it is impermeable to water
Describe what happens at the descending limb of the LoH (stage two)
the descending limb is permeable to water
water moves out by osmosis
this is absorbed by the capillaries that wrap around the nephron
water leaving the nephron at the descending limb increases the concentration of the urine
How would the length of the LoH be different in a camel?
The loop would be longer
increasing the conc of the medulla
increasing the amount of water leaving the nephron
therefore the urine is more concentrated
What is the affect of ADH binding to the receptor at the collecting duct of the nephron?
ADH increases the permeability to water so water moves out by osmosis because the medulla has a more negative water potential
describe the process of osmoregulation when dehydrated. (6 steps)
1) dehydration means the water potential of blood is more negative
2) this is detected by osmoreceptors in the hypothalamus
3) posterior pituitary secretes ADH into the blood stream
4) ADH binds to the specific receptor at the collecting duct
5) this increases the permeability to water
6) water moves out by osmosis because the medulla is more negative
