Homeostasis And Feedback Mechanisms Flashcards
Why is homeostasis important
Maintain optimal conditions for enzyme action and cell function
Examples of homeostasis
Body temp
Metabolic waste
Blood pH
Concentration of glucose in blood
Water potential of blood
Concentration of respiratory gases in blood
Two coordiantion systems for homeostasis
Nervous and endocrine system
Describe the nervous system
Allows us to make sense of our surroundings and respond to them and coordinate and regulate bodily functions
Nerves coordinate activities of sensory receptors
Describe the endocrine system
Hormones transmit information from one part of the organsism to another to bring about change
Alters activity of one or more target organs
Describe receptors and hormones
Receptors have to be complementary to hormones for there to be an affect
Why do temperatures and pH’s of the body need to be controleld
Enzymes have a specific optimum temperature and pH to catalyse reactions at the maximum rate
What type of reactions are prevented or slowed down due to low temperatures
Molecules move slower
Lower frequency of successful collisions between substrate molecules and the active site of enzymes
Less frequent enzyme-substrate complex formation occurs
Substrate and enzyme collide with less energy making it less liekly for bonds to be formed or broken
What type of reactions speed up due to high temps
Molecules move more quickly
Higher frequency of successful collisions between substrate molcules and enzymes active sites
More frequent enzyme-substrate complex formation
Substrate and enzyme collide with more energy making it more likely for bonds to be formed or broken
What happens to reactions when temperatures increase too much
Bonds holding enzyme molcules break causing tertiary structure of protein to change
Damaging the active site permanently so substrate can’t bind
Denaturation occurs if substrate can no longer bind
What happens when pH changes
Hydrogen and ionic bonds holding tertiary structure of the protein together
Below and above optimum pH;s of an enzyme solutions with an excess of H+ and OH- ions can cause these bonds to break
Alters shape of active site so enzyme-substrate complexes form less easily
Enzyme-substrate complexes can no longer form
Complete denaturation of an enzyme has now occurred
Why do negative feedback loops occur
To maintain homeosmotic balance
What is involved in a negative feedback loop
Receptor to detect stimulus involved
Coordination system to transfer info between different parts of the body
Effector to carry out the response
Outcomes of a negative feedback loop
Stimulus continuously monitored
Increase in factor = body decreases factor and vice versa
Describe the corrective mechanisms for an increase and decrease in negative feedback loops
1) Factor increases above normal range
2) Receptor detects stimulus change triggering corrective mechanism A
3) factor returns to within normal range
Same with decrease
Whats a positive feedback
ORiginal stimulus produces response causing factor to deviate more from noral range
Descrube the positive feedback loop in bone repair
Osteoblasts secrete osteocalcin
Osteoclasts secrete acid to lower the pH of acidic conditions causing an inactive form of osteocalcin to change into an active form of osteocalcin
The active osteocalcin binsd to receptors on beta cells in the pancreas to stimulate the release of insulin
Define the term homeostasis
Maintaining internal conditions constant
How does the endocrine bring about responses in the body
1) Releases hormones from endocrine glands
2) Transports hormones in the blood
3) binds hormones to complementary receptors
Why is body temperature regulation important
ENzymes function best at optimum temperatures
So below the optimum there would be less kinetic energy and reactions take place too slowly as molecules move slower resulting in less successful collisions so less enzyme-substrate complexse form
So if above optimum temperatures, enzymes denature due to bonds breaking losing their teriary structure and altering active site
How does a negative feedback mechanism work (2 marks)
Receptors detect changes in normal internal conditions
A corrective mechanism acts so the body responds and returns conditions to normal reversing the effects of the change
Why is blood glucose regulation important
It’s a respiratory substrate/ energy is released from it during respiration
Can affect water potential of blood
What organ detects the rise/ fall in blood glucose concentration
The pancreas
what are the three effects of insulin that lead to a fall in blood glucose
1) Increase in uptake of glucose by the cells
2) Glycogenesis
3) Increased respiration at which glucose is used by cells
What hormone is released to increase blood glucose concentration
Glucagon is released for glycogenolysis and gluconeogenesis
How does ADH increase the net movement of water from the lumen of the collecting duct into the blood
ADH causes aquaporins to be inserted into cell surface membrane
Water enters cells through aquaporins by osmosis down the water potential gradient into blood capillary via interstitial fluid
A smaller volume of more concentrated urine is produced
Why does the conc of glucose decrease despite the blood containing no insulin
1) Glucose used in cell respiration
2) Glucose is converted to glycogen
3) Glucose is excreted
WHy does high blood pressure occur when diabetes isnt controlled
1) Blood glucose concentration in blood is high, lowering water potential of blood
2) Water will enter the blood from body tissues by osmosis
3) This measn there will be a greater volume of blood in the circulatory system
Describe selective reabrotption 5 marks
1) Takes place in proximal convoluted tubule
2) from the glomerular filtrate
3) Somem molecules are reabsorbed by active transport into the tubule cells
4) Some urea is is reabsorbed by diffusion
5) Glucose/ amino acids/ mineral ions/ water moves into the blood capillaries by osmosis
How is the loop of henle and antidiuretic hormone adapted to dessert environments
1) Loop of henle allows more water to leave filtrate in descending loop
2) Longer loop of henle, more Na+ and Cl- to leave filtrate in ascending
3) ADH acts on collecting duct
4) ADH makes cells more permeable
5) More water reabsorbed to blood
6) urine more concentrated
Describe how insulin reduces glucose conc in blood
1) Insulin binds to specific receptors
2) This activates carrier proteins causing more channels to form
3) Which increases the permeability of liver cells to glucose
4) insulin activates enzymes involved in glycogenesis (glucose -> glycogen)
WHy does blood gucose increase in the presence of glucagon
1) Glucagon binds to complementary receptors on surface of target cells
2) Glucagon activates adenylate cyclase
3) ATP is converted intp cyclic AMP
4) cAMP activates the enzyme protein kinase A and this results in the breakdown of glycogen to glucose
How is ultrafiltration affected by high blood pressure
Ultrafiltration takes place at high blood pressure so they will be affected by the drop in blood pressure
The rate of ultrafiltration would decrease
