Homeostasis 6.4 Flashcards
What is homeostasis?
Maintaining a constant internal environment within retracted limits
What happens if core body temperature gets too high?
-Hydrogen bonds in enzymes break
-Changes the tertiary structure
-Active site changes shape
-Less enzymes substrate complexes
What happens if core body temperature gets too low?
-Enzymes kinetic energy too low
-Less enzyme substrate complexes form
-Metablolic rate is reduced
What happens if Blood PH gets too high or low?
Hydrogen bonds break within proteins changing their tertiary structure
What happens if Blood glucose concentration gets too high?
Blood has lower water potential than cells
Water leaves cells into blood by osmosis
Cells lack water for metabolic reactions eg hydrolysis
What happens if Blood glucose concentration gets too low?
Glucose is not provided to cells fast enough for a high rate of respiration
What happens if Blood water potential gets too high?
Water enters cells by osmosis
Too much water causes cell lysis
Lots of water in the blood causes high blood pressure
What happens if Blood water potential gets too low?
Water leaves cells into blood by osmosis
Lack of water for metabollic reactions and to act as a solvent
What is the definition of a negative feedback mechanism? Give an example
Reverses the direction of change back to its original level
eg. Regulation of body temp
What is the definition of a positivie feedback mechanism? Give an example
A change in one direction is amplified leading to a further increase
eg. haemoglobin binds to oxygen increasing affinity so oxygen can bind more easily
What is a hormone? Where are they secreted from? How are hormones transported around the body? Where do specific hormones act?
A chemical messenger
Secreted from Glands
Transported in Blood
Target cells
How is the effect of hormones different to the nervous system?
Wide spread vs localised
Long lasting vs short lasting
What cells produce insulin and glucagon?
Insulin- Beta cells in Islets of Langerhans in pancreas
Glucagon- Alpha cells of Islets of Langerhans in pancreas
How does insulin decrease blood glucose concentration?
-(Blood glucose concentration too high)
-(Insulin secreted from beta cells in pancreas)
-Binds to receptors on liver cells
-Causes more channel proteins to be inserted into the cell membane
-Glucose enters by facilitated diffusion (down a conc grad)
-Activates enzymes to convert glucose to glycogen for storage (glycogenesis)
How does Glucagon increase blood glucose concentration?
-(Blood glucose concentration too low)
-(Glucagon secreted from alpha cells in pancreas)
-Binds to receptors on liver cells
-Activates enzymes which hydrolyse glyogen into glucose
-Glucose moves into blood by facilitated diffusion
-(Glycogenolysis)
OR
-activates enzymes which convert Glycerol/Amino acids into glucose
(Glucaneogenesis)
How does Adrenaline increase blood glucose concentration?
-Adrenaline released from adrenal glands
-Binds to receptors on liver cells
-Activates enzymes which hydrolyse glycogen into glucose
-(Glycogenolysis)
What is the second messenger model of adrenaline and glucagon?
-binds to receptors on liver cells
-Activates Adenylate cyclase which produces cyclic AMP
-This activates protein Kinase
-This activates enzymes for Glycogenolysis/Gluconeogenesis
Describe these three processes that occur in the liver:
-Glycogeneis
-Glycogenolysis
-Glucaneogenesis
Glycogenesis- Converting glucose into glycogen for storage
Gylcogenolysis- Hydrolysing glycogen into glucose for storage
Gluconeogenesis- Converting amino acids/glycerol into glucose
What is the difference between type I diabeties and type II diabetes
Type I - Insulin cannot be produced due to Beta cells being destroyed (autoimmune)
Type II - Receptors dont respond to insuling (can produce insulin)
What is the treatment for type I diabeties? Why can’t insulin be taken orally? Why should complex carbohydrates be eaten instead of sugar?
-Insulin injections
-Insulin would be digested or denatured
-Complex carbs hydrolysed and absorbed more slowly than sugar, preventing rapid increase in blood glucose
What is a cause of type II diabeties? What is a treatment of type II diabeties? Why won’t insulin injections treat type II?
-Obesity
-Regular exercise to decrease blood glucose concentration (respiration, glucose enters cells by facilated diffusion)
-Loss of weight
-Glucose lowering medication
-Insulin injections do not help as the body can produce insulin but receptors do not respond to it
What is osmoregulation?
The control of the blood water potential
Name each part of the nephron and their function?
1.Glomerulus -Ultrafiltration
2. Basement membrane -Ultrafiltration
3. Bowmans capsule
4. Proximal convoluted tubule - Selective reabsorption
5. Loop of Henle - reabsorbing more water from glomerular filtrate by producing Na+ concentration gradient in the medulla
6. distal convoluted tubule
7. collecting duct - reabsorbing water into blood (osmoregulation)
What are the 3 layers the substances pass through in Ultrafiltration?
-pores in the capillary endothelium
-Basement membrane
-Bowmans capsule epithelium (made of podocytes)
What is the process of ultrafiltration?
-High blood pressure in glomerulus
-small molecules eg water glucose and amino acids forced out (of blood into Bowmans capsule)
-Forms glomerular filtrate in the Bowmans capsule
- Proteins and cells are too large to pass through so stay in the blood
What is proteinurea?What is it caused by?
High quantity of protein in the urine, caused by damage to the basement membrane
What is selective reabsorption where does it take place?
85% of useful molecules and water reabsorbed at the proximal convoluted tubule into the blood
-Water reabsorbed by osmosis (lower water potential in blood due to higher concentration of proteins)
-Glucose reabsorped by active transport
How are the epithelial cells lining the proximal convoluted tubule adapted for absorption?
Microvilli which increase surface area to maximise rate of diffusion.
Many mitochondria for active transport of glucose into capillary
Epithelium cells are 1 cell thick so short diffusion pathway
What does the Loop of Henle do and how does it do this (generally)
Involved in reabsorbing more water from the glomerular filtrate
By producing a Na+ concentration gradient in the medulla
How does the descending limb cause water to move out by osmosis?
-Descending limb is permeable to water
-Water moves out by osmosis into the lower water potential of the medulla
-Na+ is actively transported into the descending limbb
-Due to the loss of water and Na+ moving in the filtrate becomes more concentrated down the descending limb
-Creates an increasing Na+ concentration deeper into the medulla
How does the ascending limb of the Loop of Henle lower water potential in the medulla and lower the concentration of the filtrate?
-Na+ are actively transported out of the ascending limb
-This creates a lower water potential in the medulla
-The ascending limb is impermeable so water stays in the tubule
-Filtrate becomes less concentrated (higher water potential)
How is water reabsorbed along the collecting duct?
-A water potential gradient is maintained along the whole length of the collecting duct (lower water potential in the medulla
-Water will leave along the whole length of the collecting duct into the medulla
-Water is then reabsorbed into the surrounding capillaries
What are the steps that occur when Dehydrated to increase blood water potential?
-Decrease in blood water potential
-Water moves out of osmoreceptors into blood by osmosis (inhypothalamus in brain)
-This sends an impulse to the posterioir pituitary gland which releases more ADH into the blood
-ADH causes collecting duct membrane to become more permeable to water
-More aquaporins are inserted into membrane of distal convoluted tubule
-More water reabsorbed into the blood
-Urine volume less and more concentrated
What are the steps that occur when blood water potential too high? (in terms of ADH)
-Water moves into osmosreceptors from blood by osmosis (in the hypothalamus in the brain)
-This sends an impulse to the posterior pituitary gland which releases less ADH into the blood
-ADH causes collecting duct membrane to become less permeable less aquaporins are inserted
-less water reabsorbed into the blood
-Urine volume more and is less concentrated
explain why glucose is found in the urine of someone with untreated diabetes
-High concentration of glucose in the blood filtrate
-All carrier proteins are in use maximum rate
-Not all glucose reabsorbed at the proximal convoluted tubule
