Osmoregulation and Temperature Regulation

• Describe the Gross structure of the urinary system

  A)Right kidney

  B)Ureter

  C)Urethra

  D)Bladder

  E)Left Kidney

  F) Renal Vein

  G) Renal artery

  
• Describe the gross structure of the mammalian kidney


  A)Pelvis

  B)Medulla: inner region which consists of collecting ducts, loop of Henle, blood vessels

  C) Cortex: Outer region which consists of Bowman’s capsule, convoluted tubules and blood vessels

  
• Describe the structure of the nephron

  A)glomerulus

  B)bowman’s capsule

  C)proximal convoluted tubule

  D)collecting duct

  E) afférent arteriole

  F)efferent arteriole

  G) loop of henle

  H)distal convoluted tubule

  
• describe the blood vessels in the nephron:

  The wide afférent arteriole from the renal artery, enters the renal capsule and forms the glomerulus. The Efferent arteriole branches to form a capillary network that surrounds tubules
• how is urea produced?

  1. Hepatocytes deaminate (remove amino group) excess amino acids to form ammonia
  2. Ammonia enter ornithine cycle in the liver, which joins with CO2 to form urea, which is less toxic
• How is urea removed from the bloodstream?

  It moves via ultrafiltration in the Bowmans capsule

  • The wider afférent arteriole has a higher pressure, which forces small molecules (urea, water, glucose and mineral ions) out of capillary fenestrations AGAINST the osmotic gradient
  • the basement membrane acts as a filter, stopping large proteins and blood cells from leaving the capillary
• adaptations of Bowman’s capsule cells for ultrafiltration

  • wider afférent arteriole to generate a pressure gradient
  • Fenestrations between epithelial cells of capillaries
  • Fluid can pass between and under folded membrane of podocytes
• What is reabsorbed during selective reabsorption?

  • 80% water
  • all glucose, amino acids
  • 85% mineral ions
• What is happening in 1?

  1. Sodium-potassium pumps use ATP from the mitochondria to pump sodium ions out of the proximal convoluted tubule and into the blood.

  
• What is happening at 2?

  2)This reduces the sodium ion concentration inside the cells lining the PCT. This creates an electrochemical gradient.

  
• What is happening at 3

  Therefore sodium ions from the PCT diffuse into the cells through a co transport Protein- this carries glucose or amino acids at the same time

  
• What is happening at 4?

  Because this reduces the water potential inside the cells lining the pct, water also moves into the cells by osmosis.

  
• What is happening at 5?

  Because the concentration of glucose and amino acids has increased inside the cells lining the PCT, they diffuse out into the blood (which is at much lower concentration due to ultrafiltration)

  
• What is happening at 6?

  This causes the water potential of the blood to be lower than the cells, causing water to follow by osmosis.

  
• How are cells in the proximal convoluted tubule adapted for selective reabsorption?

  • Microvilli create a large surface area for co-transporter proteins
  • many mitochondria Provide energy for sodium-potassium pump proteins + ATP for active transport
  • Folded basal membrane provides large surface area
• What happens in the descending limb of loop of henle?


  • descending limb is permeable to water but impermeable to ions
  • Filtrate enters fairly dilute as most solutes have been removed in the PCT
  • the medulla is more concentrates, so water leaves filtrate by osmosis.
  • This causes the filtrate to become more concentrated
  • but as the filtrate moves down the descending limb, the medulla continues to become more concentrated, so water keeps passing out by osmosis, causing the filtrate to be very concentrated at the bottom Of the loop
• What happens in the ascending limb of the loop of henle?

  • the ascending limb is permeable to ions but impermeable to water
  • The Na-K-Cl cotransporter proteins as well as Na-K-ATPase pump, pump ions out of filtrate and into medulla.
  • This makes medulla more concentrated, and filtrate less concentrated.
  • The ion pumps work at a constant rate, keeping medulla more concentrated than filtrate, maintaining a concentration gradient
• Explain the role of the distal convoluted tubule

  Reabsorption:

  • of water via osmosis
  • of ions via active transport
  • the reabsorption of water is controlled by the permeability of walls, determined by ADH
• How does the loop of henle act as a counter current multiplier

  • it ensures the flow of filtrate in the ascending and descending limbs occurs in opposite directions, to maintain a steep osmotic gradient.
  • the movement of ions out of the descending limb, enhances the movement of water out of the ascending limb
  • allowing for maximum reabsorption of water
• What is osmoregulation?

  Osmoregulation is the process by which organisms regulate the concentration of water and solutes in their bodies to maintain internal balance.
• What can change blood water potential?

  • level of water intake
  • sweating
  • level of ion intake in diet
  • level of ions used in metabolic processes or excreted
• Explain the role of the hypothalamus in osmoregulation

  • contains osmoreceptors which detect changes in osmolarity, causing them to shrink (if high) or swell (if low)
  • osmoreceptors stimulate the release of ADH from the posterior pituitary gland
• Describe what happens when the body is dehydrated

  1. Increased sweat, drinking less
  2. This causes the water potential of the blood to decrease
  3. This decreases in water potential is detected by osmoreceptors in the hypothalamus
  4. Nerve impulses pass to the posterior pituitary gland
  5. Pituitary gland secretes more ADH, which travels to kidney
  6. it increases the permeability of the walls of the DCT and CD to water.
  7. More water is reabsorbed into the blood from filtrate in tubule.
  8. This restores the water potential of the blood
  9. Producing a small volume of dark urine, which is hypertonic to blood.
• What happens when the body has too much water?

  1. No sweat, drinking lots
  2. This causes the water potential of the blood to increase
  3. This increase is detected by osmoreceptors in the hypothalamus
  4. fewer Nerve impulses pass to the posterior pituitary gland.
  5. pituitary gland produces less ADH
  6. less ADH travels towards the kidney, so walls of the DCT and CD are less permeable to water
  7. so less water is reabsorbed into the blood from filtrate in the tubule
  8. So the WP of blood is lower, and the WP of urine is higher.
  9. This produces a larger volume of pale urine, which is hypotonic to blood.
• How is the kidney of a desert kangaroo rat adapted for life in a dry environment?

  • Long loop of henle —> efficient counter current system Which maintains a steep osmotic gradient, so lots of water can be reabsorbed
• what is an ectotherm?

  Cold-blooded

  • an organism that can’t increase its rate of respiration to increase the internal production of heat.
  • it relies on external sources to regulate its body temperature
• what is an endotherm?

  Warm blooded

  • an organism which can regulate its body temperature independently of external resources
  • Thermoreceptors send impulses to the hypothalamus which triggers a physiological or behavioural response
• Behavioural methods that endotherms use to regulate body temperature

  • basking in sun
  • digging burrows
  • hibernation
  • panting
• how does the autonomic nervous system enable endotherms to thermoregulate?

  • thermoreceptors in the hypothalamus detect changes in blood temp
  • hypothalamus sends impulses to effectors
  • resulting in: vasodilation/ vasoconstriction, sweating, piloerection, shivering