Temperature and the Urinary System Chapter 50

Temperatureis determined through multiple factors Internal Factors Metabolic Rate All metabolic reactions produce heat as a by-product External Factors Sunlight, Water, Underground Behavior

Body Temps Low body temperatures do not allow high metabolic rates because of the temperature dependence of enzymes High metabolic rates may cause excessive heating (which requires cooling)

Heat Transfer 4 types Radiation – transfer of energy by electromagnetic radiation (hot to cold) Conduction – direct transfer of heat between two objects that are touching (hot to cold) Convection – transfer of heat by movement of a gas or liquid Evaporation – energy used to vaporize a liquid Other factors Surface area Small animals lose heat faster than larger ones Temperature Difference – larger the difference the faster the transfer Heat conductance Those with a surface with high conductance will gain or lose heat faster Fur, Feathers, and Blubber

Organisms are classified based on heat source Homeotherms – regulate their temp around a set point (warm blooded, endotherms) Poikilotherms – allow their body to conform to their environment (cold blooded, ectotherms) Heterotherms – fall in between these groups

Ectotherms Regulate Temp with behavior Sunbathing, increased movement Shade, Bathing Have a generally low metabolic rate Endotherms Create internal Metabolic Heat Warm the organism when cold Body must be cooled if overheated Vasoconstriction/dilation Sweating/Panting

Hypothalamus If the body overheats, then the hypothalamus tells your body to exhibit heat loss reactions If the body temp falls then the hypothalamus tells the body to create more heat Fever Reseting the bodies normal temp to a higher number Many bacteria can not survive at higher temperatures Torpor Reduction of metabolic rate and body temp to produce a state of dormancy (hibernation)

The Mammalian Kidney Blood is delivered to the kidney through the renal artery It is filtered and urine is produced Urine drains from each kidney through the ureter to the urinary bladder Upon filling the bladder urine is passed out of the body through the urethra

Functions of the Kidney Filtration Blood is filtered into the tubule leaving cells and large proteins in the blood Reabsorption Selective movement of important solutes out of the filtrate to be put back into the blood Secretion Movement of substances from the blood into the filtrate (toxic substances)

The Nephron Filtering Unit of the Kidney 1 million nephrons in each kidney Afferent arteriole brings blood to the glomerulus blood pressure forces fluid through capillary walls (blood cells and plasma proteins are too large to go through) Glomerulus is surrounded by Bowmans capsule. Capsule has slits so that filtrate can enter the nephron tubules. Blood components not filtered drain into the efferent arteriole Next the filtrate enters a portion of the nephron called the proximal convoluted tubule then proceeds into the Loop of Henle and finally through the distal convoluted tubule. Reabsorption and secretion occur in these tubules. The Distal convoluted tubules drain into a collecting duct that will combine with others to drain urine into the renal pelvis

Reabsorption& Secretion Water Blood is filtered many times each day to produce 1-2L of urine Water is reabsorbed from the filtrate by the proximal convoluted tubule, the descending loop of Henle, and the collecting duct Secretion of water can help to regulate blood volume Glucose/other Nutrients Reabsorbed by active transport and cotransport Secretion of wastes Done by the same methods as reabsorption but in the opposite direction Secretion of H+ into the urine maintains the blood at a neutral pH

Proximal Convoluted Tubule Virtually all nutrient molecules present in the filtrate are reabsorbed by the proximal convoluted tubule 2/3 of NaCl and Water is reabsorbed here too Na+ is actively transported out of the tubule Cl- follows it by electical attraction Water follows it by osmosis

Loop of Henle Ascending Limb Impermeable to water Thick Portion has Na+ actively transported out, Cl- follows Thin portion has NaCl flow out by diffusion Descending Limb Permeable to water but not to NaCl Water moves out by osmosis because of the concentration of NaCl in the fluid that is secreted by the ascending limb

Distal Convoluted Tubule and Collecting Duct The very dilute fluid from the distal convoluted tubule enters the collecting duct. Water diffuses out due to the higher concentrations of salt outside This concentrates the urine