Biology Chapter 44 Osmoregulation and Excretion

Define osmolarity and distinguish among isoosmotic, hyperosmotic, and hypoosmotic solutions

-[solutes]/[water] -removes nitrogenous base -isoosmotic is equal pressure in and out of cell hyposomotic is high water concentration and low solute hypersomotic is high solute concentration and low water

Explain how the loop of Henle functions as a countercurrent multiplier system

-as filtrate reaches ascending loop it has high salt concentration -ascending is permeable to salt ions but not water -countercurrent because it uses active transport and osmolarity of vasa recta to maintain the gradient -both carry blood in opposite direction -so in the descending water is gained to the vasa recta but in the ascending water is lost and NaCl is gained

Discuss the osmoregulatory strategies of marine animals

-gains water and salt from breathing and food -salt ions excreted from gills -osmotic water loss through gills -excretion of salt water from scanty urine from kidneys

Describe and explain the relationships among the processes of filtration, reabsorption, and secretion in the mammalian kidney

-kidney has renal cortex and renal medulla -supplied blood by the renal artery -tightly packed excretory tubules -tubules carry and process a filtrate entering the kidney -fluid reabsorbed into cells -secretion to the renal plebes and excreted by the ureter

Using a diagram, identify and describe the function of each region of the nephron

-long tubule -glomerulus which is a ball of capillaries -glomerulus is surrounded by the bowman capsule -filtrate is formed when blood pressure forces fluid from the glomerulus into bowman capsule -proximal tubule -loop of henle -distal tubule -capillaries of the golfers are formed by branches of the renal artery -capillaries converge to formed the efferent arteriole which branches of this form the peritubular capillaries -vasa recta are branches that go downward that serve the renal medulla and loop of henle for juxtamedullary nephrons

Describe the Malpighian tubule excretory system of insects

-organs that remove nitrogenous wastes and function in osmoregulation -extend from dead end tips immersed in hemolymph to openings in the digestive tract -filtration step is absent -transport epthileium lines the tubules secretes solutes such as nitrogenous wastes into the lumen -water goes into the tubule -solutes pumped back into the hemolymph -water is reabsorbed -dry matter removed with feces (uric acid)

Describe the nervous and hormonal controls involved in the regulation of the kidney

ADH (vasopressin) -released from pituitary bind and activate membrane receptors -receptors activate a signal which initiates signal transduction which. inserts aquaporins into the the membrane -reduces urine volume and reabsorbs more water -when blood osmolarity increases osmoreceptors in the thalamus trigger release of ADH as osmolarity falls a negative feedback mechanism stops the release of ADH ADH Secondary Messenger Protein Kinase

Explain how the loop of Henle enhances water conservation by the kidney

As the filtrate flows to the descending limb of the loop of Henle, solutes become more concentrated due to water leaving the tubule by osmosis interstitial fluid in loop of henle is hypersomotic -aquaporin form water channels which makes transport epithelium permeable to water

Explain how the osmoregulatory problems of freshwater animals differ from those of marine animals

Freshwater does not get enough salt while marine gets too much. Freshwater gets salt from gills while marine loses water gain through gills large amounts of water excreted through dilute urine from kidneys

Distinguish between osmoregulators and osmoconformers. Explain the cost of osmoregulation

Osmoconformers-available to only marine animals Be iso-osmotic with surroundings Internal = external, no gain or loss of water Usually live in stable environment Osmoregulator-Not iso-osmotic so need to control Allows living in freshwater and land habitats where an osmoconformer could not live. Has an energy cost to maintain osmotic gradients dependent on how different the environment is from internal. Energy cost decreases if body fluids and environment are more similar.

Describe some adaptations that reduce water loss in terrestrial animals

Plants have waxy cuticle on leaves, waxy exoskeletons in insects, layers of dead skin covering most land vertebrates behavior changes

Describe the key steps in the generalized process of urine production

filtration- excretory tubule collects filtrate from the blood using blood pressure reabsorption-transport epithelium reclaims valuable substances secretion-substances such as toxins and excess ion added to the excretory tubule excretion-urine leaves the body

Compare the strategies to eliminate waste as ammonia, urea, or uric acid. Note which animal groups are associated with each process and why a particular strategy is most adaptive for a particular group

fish-ammonia low cost high toxicity mammals-urea less toxic but requires more energy uric acid-birds non toxic saves water most costly

Distinguish between cortical and juxtamedullary nephrons. Explain the significance of the juxtamedullary nephrons of birds and mammals

nephrons are the function units of the kidney -cortical units are in the cortex and go slightly into the renal medulla -juxtamedullary nephrons extend deep into the medulla -essential to production of hypersomotic urine key for water conservation

Define osmoregulation and central problem of osmoregulation

rates of water uptake and lost must balance or else the result is lysis or shriveling osmoregulation balances the concentrations of water and solute

Explain the role of transport epithelia in osmoregulation and excretion

specialized cells that regulate solute movements, usually in specific directions Bound by tight junctions May form complex tubular networks Maintain fluid composition: depends on specialized structures, such as transport epithelia. They are essential for osmotic regulation and waste disposal