Homeostasis Flashcards
(22 cards)
Homeostasis definition
Maintains constant internal temperatures within restricted kilts by a physiological control system
What 4 things does homeostasis affect?
Temperature and PH need to be constant at optimum temperature
Water potential so no creation or lysis of cells
Blood glucose concentration so used as respiratory substrate
What is meant by negative feedback
A change to the normal level whch initiates a response whch reduces the effect a change so restores systems back to original level or parents continuation of behaviour pre uni named risk
What is meant by positive feedback
A change to the normal levels whch initiates an additional change in the same direction
Produces more
Describe the response to a higher than normal blood glucose concentration
Eat a meal and increase in blood glucose concentration from the normal
Increase in blood glucose concentration detected by the hypothalamus which produces beta cells and they secrete insulin by EXOCYTOSIS Insulin is a hormone and binds to complementary receptors on the cell surface membrane of the liver and muscle cells stimulates enzymes which activate enzymes in glygonesis whch is the c9nersion of glucose into glycogen and cuses more carrier and Chanel proteins of glucose to move to the cell surface membrane of target cells where glucose them diffuses in by facilitated diffusion into fells which lowers the blood plasma concentration
Describe the response a blood glucose concnetratiin lower than normal
No food for a long time whch causes decrease blood glucose concentration from the normal
Lower blood glucose concentration detected by the hypothalamus which produces alpha cells whch secrete glucagon by exocytosis which binds to complementary receptors on the cell surface membrane of target cells such as liver or muscle cells which activates enzymes in glycogen lysis which hydrolysis glycogydidc bonds into glycogen to release glucose and glycogeonesis which coverts fatty acids and amino acids into glucose. Glucose then diffuses by facilitated diffusion out th cell into the blood to increase blood glucose concentration
Thermoregulation in endotherms
Mammals birds and some fish whch maintain body temperature by physiological and behavioural means
Thermoregulation in ectotherms
Reptiles, amphibians whch maintain body temperature by behavioural means only by exposing them selves to the sun, taking shelter and getting warmth from the ground
Describe the second messenger model of adrenaline and glucagon action
Adrenaline is a hydrophobic molecule
This means it’s can’t just enter the cell surface membrane of liver or muscle cells so has complementary receptors on the cell surface membrane which is complementary to adrenaline which forms an adrenaline receptor complex. This activates adenylate cyclase change the teirtay structure and activates enzyme adrenal cyclase coverts ATP to cAMP and produces a large number of theses molecules which is called the cascade effect. This binds to enzymes called kinase which changes to activate forms which adds phosphates groups onto other enzymes called phoshphorylation which increases glycogenlysis whch converts glycogen into glucose which diffuses out by active transport ad is used in glycolysis
Type 1 diabetes
This is an autoimmune destruction of beta cells which doesn’t produce enough insulin but still remains sensitive to insulin so less insulin binds to complementary receptors so LESS carrier and Chanel proteins move to cells surface. Membrane of target cells so less uptake of glucose and less activation enzymes for glycogenesis. Increase in blood glucose concentration in the blood so symptoms would be more thirst as lower water potential of blood and more concentrated urine more frequent. Take insulin as an injection not by mouth as it’s a protein and can denature.
Type 2 diabetes
Caused by obesity, high glucose diet and smoking, no exercise.
Beta cells still produced but low sensitivity as less effect on target cells. Same symptoms of more concentrated urine and more thirst. LESS glycogenesis and less carrier and channel proteins on the cell surface membrane so more concentrated blood glucose. More excercise so more glucose used in glycolysis and diet low in blood glucose so regain sensitivity.
Kidney knowledge
We have 2 kidneys. Blood enters each kidney by the renal artery and leaves by the renal vein down the ureter into the bladder where it’s stored and pee out the urethra. Many kidneys have lot of nephrons
Structure of a nephron
Renal artery = afferent arteriole = glomerulus= bowman’s capsule = proximal converted tubule = loop of henle= distal convulated tubule = renal vein also effectrent arteriole
Describe ultrafiltration
The lumen of the afferent arteriole is wider than the efferent arteriole. Blood enters through the afferent arteriole through the renal artery. High hydrostatic pressure causes small molecules such as water, glucose, ions and urea to pass out the fenestration in the capillaries in endothelium and through the basement membrane which has specialised cells called podocytes that’s act as a a filter. Proteins, cells and platelets are too large and go through the efferent arteriole
Reabsorption in the proximated convulated tubule
Fluid containing useful molecules such as glucose, water and amino acids are reabsorbed by cells so urea is only excreted out
Active transport of sodium ions out the epithiulum cells living the tubule into blood stream which now have a low concentration of sodium ions in the cells. This allows sodium ions to diffuse into the epithelium cells by facilitated diffusion using carrier protein co transported with glucose. Water reabsorbed by osmosis ans enters via aquaporins
High concentration of mitochondria so active transport can take place using ATP
Membrane is covered with microvilli which is highly folded membrane so incarses surface area for diffusion.
Many Carrier and Channel proteins
What dies urine have to be
Has to be concentrated and not that diluted otherwise it would be lethal
Loop of henle
This happens in the medulla of the kidney
The ascending limb which is impermeable to water actively transports sodium ions iout which increases the concentration ions i the interstitial region so lowers water potential in the tissue fluid.
The descending limb Is permeable to water s water leaves by osmosis as you go down the this limb the fluid becomes more concentrated so makes ions in the ascending limb easier to transport sodium ions.
Water potential in the tissue fluid is lower in the medulla than the collecting duct so waste leaves the collecting duct and urine is more concentrated
A02 for organism Iiving in conditions with low water
Thicker medulla = longer loop of henle so more sodium ions actively transported, so increases water potential gradient so more water reabsorbed by descending limb and collecting duct so more concentrated urine and after water to keep animals cool
Why is high concentration of urine found in blood with person of untreated diabetes
High concentration of glucose in blood
More glucose filtered out basement membrane
Not all glucose reabsorbed by the proxiated convulated tubule as al carrier proteins saturated at co transporter protein so some glucose lost in urine
Why is osmoreguation important
Water leaves cells and causes crenation if water potential is too low Water potential is too high then waste enters the cell and causes lysis
Describe the response that brings an increase in water potential of the blood
Osmoreceptors in the hypothalamus detect water potential of the blood is too low
Water moves by osmosis from receptors to the blood
This shrinks the receptors and causes sodium ion channels to open increasing action potential which causes ADH produced by the hypothalamus and stored by the pituitary to be secreted. This hormone bi to complementary receptors on the collecting duct and distllated tubule causing vesicles contain aquaporins to fuse with cell surface membrane and increase permeability to water
So more water reabsorbed by proximal distillates tubule and collecting duct from cells y osmosis.smaller volume of urea and more concentrated urine
