homeostasis exam Q

• Describe the function of the proximal convoluted tubule

  allows selective reabsorption to occur
• describe and explain the adaptations found in the proximal convoluted tubule

  walls of the pct are one cell thick to reduce diffusion distance

  microvilli on the cell surface to increase surface area for reabsorption to take place

  many mitochondria to provide ATP for active transport, which increases the rate of active transport

  many co-transport proteins found on cell surface membrane increases the rate of active transport
• how does having a long loop of henle allow camels to function despite many days without water

  a longer ascending limb means that more solutes are reabsorbed into the blood, and a longer descending limb means that more water is reabsorped into the blood. the filtrate will be more concentrated so there will be less water lost through the urine. it also means that healthy water levels are retained in the blood for longer
• describe how less water is lost in the urine in response to low water potential of the blood

  low water potential is detected by osmoreceptors in the hypothalamus. so hypothalamus produces more ADH which is secreted by the pituitary gland. the membrane of the collecting duct becomes more permeable to water so more water is reabsorped into the blood by osmosis, so less water lost in urine.
• why is homeostatic control of osmoregulation not sufficient enough to prevent dehydration ?

  as homeostatic control of osmoregulation only prevents the water potential of blood from decreasing any further, as a result further intake of water is needed to prevent dehydration
• describe how ultrafiltration occurs

  during ultrafiltration, there is high hydrostatic pressure in the glomerulus, this causes small molecules such as glucose and water to pass out of the glomerulus. they then pass through gaps in the capillary endothelium and through the basement membrane to form glomerular filtrate.
• how does ADH cause urine to become more concentrated ?

  ADH causes the permeability of the membrane of the distal convoluted tubule and collecting duct to increase , this causes more water to be reabsorbed into the blood through osmosis