REGULATION AND   CONTROL                 ALBIO9700/2006JK
Importance of homeostasis• In both animals and plants, chemical  messengers called hormones/plant  growth regulators help ...
Homeostasis• Maintaining a constant environment for the cells within  the body• Many features of the environment affect th...
• Most control mechanisms use a negative  feedback control loop (involving a  receptor /sensor and an effector )• Input : ...
Negative feedback control loop                           ALBIO9700/2006JK
Excretion• The removal of toxic or excess products of  metabolism from the body• Two main excretory products are carbon  d...
• Deamination  – The breakdown of excess amino acids in the liver, by    the removal of the amine group; amine and eventua...
The structure of the kidney•   Renal artery; renal vein•   Ureter•   Urethra•   Capsule; cortex; medulla; pelvis•   Nephro...
ALBIO9700/2006JK
Ultrafiltration• Involves filtering small molecules (urea) out of  the blood and into the renal capsule, from here  they f...
ALBIO9700/2006JK
• Factors affecting glomerular filtration rate   – Glomerular filtration rate : rate at which fluid     seeps from the blo...
Reabsorption• Involves taking back any useful molecules from the fluid  in the nephron as it flows along• Reabsorption in ...
ALBIO9700/2006JK
• Reabsorption in the loop of Henle and  collecting duct  – The function of the loop of Henle is to create a very high    ...
ALBIO9700/2006JK
• Reabsorption in the distal  convoluted tubule and collecting  duct  – First part behaves in the same way as the    ascen...
Control of water and          metabolic wastes• Osmoreceptor, the hypothalamus and  ADH  – Osmoregulation : the control of...
• How ADH affects the kidneys  – ADH acts on the plasma membranes of the cells    making up the walls of the collecting du...
• Negative feedback in the control of  water content  – When blood water content rises, the    osmoreceptor are no longer ...
Upcoming SlideShare
Loading in …5
×

01 Importance of Homeostasis; Excretion; Control of Water

5,166 views
5,043 views

Published on

Published in: Education
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
5,166
On SlideShare
0
From Embeds
0
Number of Embeds
698
Actions
Shares
0
Downloads
51
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

01 Importance of Homeostasis; Excretion; Control of Water

  1. 1. REGULATION AND CONTROL ALBIO9700/2006JK
  2. 2. Importance of homeostasis• In both animals and plants, chemical messengers called hormones/plant growth regulators help to transfer information from one part to another and so achieve coordination• In many animals, nerves transfer information in the form of electrical impulses ALBIO9700/2006JK
  3. 3. Homeostasis• Maintaining a constant environment for the cells within the body• Many features of the environment affect the functioning of the cell: – Temperature – low temperatures slow metabolic rates/high temperatures cause denaturation of proteins – Amount of water – lack of water in tissue fluid causes water to be drawn out of cells by osmosis, causing metabolic reactions in the cell to slow or stop/too much water entering cell may cause it to swell or burst – Amount of glucose – lack of it causes respiration to slow or stop (no energy source)/too much glucose may draw water out of the cell by osmosis• Homeostatic mechanisms work by controlling the composition of blood, which controls the composition of tissue fluid ALBIO9700/2006JK
  4. 4. • Most control mechanisms use a negative feedback control loop (involving a receptor /sensor and an effector )• Input : receptor picks up information about the parameter being regulated• Output : action by the effector• Continuous monitoring of the parameter by the receptor produces continuous adjustments of the output, which keep the parameter oscillating around a particular ‘ideal’ level, or set point.• A rise in the parameter results in something happening that makes the parameter fall ALBIO9700/2006JK
  5. 5. Negative feedback control loop ALBIO9700/2006JK
  6. 6. Excretion• The removal of toxic or excess products of metabolism from the body• Two main excretory products are carbon dioxide and urea• Urea produced in the liver (from excess amino acids) and is transported from the liver to the kidneys, in solution in blood plasma• The kidneys remove urea from the blood and excrete it, dissolved in water, as urine ALBIO9700/2006JK
  7. 7. • Deamination – The breakdown of excess amino acids in the liver, by the removal of the amine group; amine and eventually urea are formed from the amine group – Urea is the main nitrogenous excretory product of humans other than creatinine and uric acid – Creatine is made in the liver from certain amino acids, used in the muscles (creatine phosphate) where it acts as an energy store and some converted to creatinine and excreted – Uric acid is made from the breakdown of nucleic acids – Urea made in liver passes from liver cells into blood plasma. As blood passes through kidneys, the urea is extracted and excreted ALBIO9700/2006JK
  8. 8. The structure of the kidney• Renal artery; renal vein• Ureter• Urethra• Capsule; cortex; medulla; pelvis• Nephrons• Renal (Bowman’s) capsule• Proximal convulated tubule• Loop of Henle• Distal convulated tubule• Collecting duct• Afferent arteriole• Glomerulus• Efferent arteriole ALBIO9700/2006JK
  9. 9. ALBIO9700/2006JK
  10. 10. Ultrafiltration• Involves filtering small molecules (urea) out of the blood and into the renal capsule, from here they flow along the nephron towards the ureter• Blood in the glomerular capillaries is separated from the lumen of the renal capsule by two cell layers and a basement membrane• Capillary endothelium – more gaps than other capillaries• Basement membrane – made up of a network of collagen and glycoproteins; stops large protein molecules and blood cells from getting through (filter)• Epithelial cells – make up the wall of the renal capsule; have podocytes ALBIO9700/2006JK
  11. 11. ALBIO9700/2006JK
  12. 12. • Factors affecting glomerular filtration rate – Glomerular filtration rate : rate at which fluid seeps from the blood in the glomerular capillaries into the renal capsule(125 cm3min-1 in humans) – Determined by the differences in water potential between contents of the glomerular capillaries and the renal capsule – Afferent arteriole is wider than the efferent arteriole causing a ‘traffic jam’ inside the glomerulus; blood pressure rises and so raising the water potential as well – Concentration of solutes in blood plasma in the capillaries is higher than the concentration of solutes inside the renal capsule (plasma protein still remain) – Overall, the effect of difference in pressure outweighs the effect of the differences in solute concentration so water move down water potential gradient from the blood into capsule ALBIO9700/2006JK
  13. 13. Reabsorption• Involves taking back any useful molecules from the fluid in the nephron as it flows along• Reabsorption in the proximal convoluted tubule – Many of the substances in the filtrate (identical to blood plasma except large protein molecules) need to be kept in the body, so they are reabsorbed into the blood as the fluid passes along the nephron (selective reabsorption ) – Na+ transport – All glucose in glomerular filtrate is transported out of the proximal convulated tubule and into blood (amino acids , vitamins , sodium and chloride ions are actively reabsorbed) – 65% of water in the filtrate is reabsorbed as water can move freely out of the filtrate, through the walls of the tubule and into the blood by osmosis – About half the urea in the filtrate is reabsorbed by diffusing passively through the wall into the blood – Uric acid and creatinine are not reabsorbed – Creatinine is actively secreted by the cells of the proximal convulated tubule into its lumen ALBIO9700/2006JK
  14. 14. ALBIO9700/2006JK
  15. 15. • Reabsorption in the loop of Henle and collecting duct – The function of the loop of Henle is to create a very high concentration of salts in the tissue fluid in the medulla of the kidney – This allows a lot of water to be reabsorbed from the fluid in the collecting duct as it flows through the medulla – The loop of Henle allows water to be conserved in the body rather than lost in urine – Counter-current multiplier : an arrangement in which fluid in adjacent tubes flows in opposite directions, allowing relatively large differences in concentration to be built up – Collecting duct runs down into medulla where the solute concentration of the tissue fluid is very high – Water moves out of collecting duct by osmosis until the water potential of urine is the same as the water potential of the tissue fluid in the medulla – The degree to which this happens is controlled by antidiuretic hormone (ADH ) – The longer the loop of Henle, the greater the concentration that can be built up in the medulla and the greater the concentration of the urine which can be produced ALBIO9700/2006JK
  16. 16. ALBIO9700/2006JK
  17. 17. • Reabsorption in the distal convoluted tubule and collecting duct – First part behaves in the same way as the ascending limb of the loop of Henle and second part as the collecting duct – In distal convoluted tubule and collecting duct, sodium ions are actively pumped from the fluid in the tubule into the tissue fluid, from where they pass into the blood – Potassium ions are actively transported into the tubule – The rate at which these 2 ions are moved into and out of the fluid in nephron can be varied and helps regulate the amount of these ions ALBIO9700/2006JK
  18. 18. Control of water and metabolic wastes• Osmoreceptor, the hypothalamus and ADH – Osmoregulation : the control of the water content of the fluids in the body/regulating the concentration of water in body fluids (kidney) – In osmoregulation in mammals, the receptor is cells in the hypothalamus (osmoreceptors ), and the effectors are the pituitary gland and the walls of the distal convulated tubules – Nerve cells produce a chemical called antidiuretic hormone (ADH – polypeptide of 9 amino acids) – ADH passed along to the endings in the posterior lobe of the pituitary gland – Action potentials from stimulation by osmoreceptor cells causes ADH to be released from endings into blood in capillaries in the posterior pituitary glandALBIO9700/2006JK
  19. 19. • How ADH affects the kidneys – ADH acts on the plasma membranes of the cells making up the walls of the collecting ducts, making them more permeable to water than usual – This change in permeability is brought about by increasing the number of water-permeable channels in the plasma membrane – As the fluid flows down through the collecting duct, water is free to move out of the tubule and into the tissue fluid and it does so because this region of the kidney contains a high concentration of salts – Secretion of ADH caused the increased reabsorption of water into the blood – Diuresis: production of dilute urine (antidiuretic hormone stops production of dilute urine) ALBIO9700/2006JK
  20. 20. • Negative feedback in the control of water content – When blood water content rises, the osmoreceptor are no longer stimulated and stop stimulating their neighboring nerve cells. So ADH secretion slows down – The collecting duct cells do not respond immediately to the reduction in ADH secretion by the posterior pituitary gland – It takes some time for the ADH already in the blood to be broken down ALBIO9700/2006JK

×