36 Questions
What is the role of afferent and efferent arterioles in the mammalian kidney?
Afferent arteriole brings blood to the glomerulus, while efferent arteriole removes it
What is the normal diameter relationship between afferent and efferent arterioles?
The afferent arteriole has a larger diameter
How does the higher resistance in the efferent arteriole affect GFR?
It increases filtration
What are the intrinsic mechanisms used to regulate GFR?
Mechanisms initiated by the kidneys themselves
When are intrinsic mechanisms used to regulate GFR?
During transient changes in blood pressure that accompany daily activities
How do marine mammals like dolphins obtain their water?
From metabolic processes
What is the term used for animals that can adapt to a wide range of salinities?
Euryhaline animals
In freshwater, how do teleost fish counteract obligatory solute movement?
By actively taking up ions from water through their gills
How do teleost fish in saltwater excrete excess ions?
Through their gills
What process yields nitrogenous waste products in animals?
Amino acid catabolism
What is the main function of the kidneys in teleost fish osmoregulation?
Produce large amounts of dilute urine in freshwater
What is the primary function of aldosterone in the mammalian kidney?
Regulates Na+ reabsorption and K+ secretion
Which cells in the distal tubule or collecting duct are affected by aldosterone?
Principal cells
What is the net effect of aldosterone activity in the distal tubule or collecting duct?
Increased Na+ and water reabsorption
What is the function of atrial mechanoreceptive fibers in the mammalian heart?
Detect changes in atrial filling and rate
What is the role of stretch-sensitive secretory cells in the mammalian heart?
Produce and release atrial natriuretic peptide (ANP)
What is the effect of atrial natriuretic peptide (ANP) on the kidney?
Increases renal Na+ excretion
What is the main function of basolateral Na+/K+ ATPase in proximal tubule cells?
Pumping Na+ out of the cell into the blood
What is the function of aquaporins in the descending limb of the loop of Henle?
Allowing passive movement of water out of the tubule
What is the significance of the thick ascending limb of the loop of Henle being impermeable to water?
Allows for reabsorption of NaCl into the interstitium
What is the function of loop diuretics like Furosemide in the loop of Henle?
Inhibiting active transport of NaCl
What is the role of countercurrent exchange in the loop of Henle?
Preserves concentration gradient in the interstitium
What distinguishes a juxtamedullary nephron from a cortical nephron?
Presence of vasa recta
What is the primary function of the collecting duct in the nephron?
Reabsorption of Na+ via secretion of K+ and H+
What triggers the production and secretion of anti-diuretic hormone (ADH) from neurosecretory neurons?
Increased plasma osmolarity
How does ADH impact water reabsorption in the distal tubule and collecting duct?
Promotes aquaporin-2 synthesis
What is the primary requirement for cell survival?
Retention of appropriate quantities of water
What is the difference between Osmoconformers and Osmoregulators?
Osmoconformers have internal levels of ions and water that fluctuate with levels in the environment, while Osmoregulators maintain the levels of ions and body fluid across changing environmental levels
Which of the following factors contribute to obligatory osmotic exchanges?
All of the above
How do small animals differ from large animals in terms of hydration and dehydration?
Small animals hydrate or dehydrate much faster than larger animals
Which of the following factors contribute to the permeability of the integument (body covering)?
Both a and b
What is the role of metabolic water in osmotic exchanges?
Both a and c
What is the primary function of the mammalian kidney?
Elimination of nitrogenous wastes
How do teleost fish in seawater maintain hydration?
By controlling ion levels
What is the role of active epithelial transport in osmoregulation?
Controlling water and salt exchange
What is the difference between obligatory and controlled osmotic exchanges?
Controlled osmotic exchanges are physiologically regulated, while obligatory osmotic exchanges occur in response to factors over which the animal has little or no physiological control
Study Notes
Osmoregulation in Animals
- Body fluids constitute the immediate environment for cells and molecules
- The composition of body fluids provides the context in which cells, organelles, and molecules function
- The major requirement for cell survival is the retention of appropriate quantities of water
- Water is the most important inorganic constituent in living cells
- Enzyme activity depends on the degree of hydration
- Water is a solvent for organic and inorganic substances
- Water determines the volumes of cells and tissues
Osmoregulators and Osmoconformers
- Osmoregulators maintain the levels of ions and body fluid across changing environmental levels
- Osmoconformers' internal levels of ions and water fluctuate with levels in the environment
Osmotic Exchanges
- Osmotic exchanges occur between an animal and its environment through:
- Transepithelial diffusion
- Ingestion
- Defecation
- Metabolic water production
- There are two types of osmotic exchanges:
- Obligatory osmotic exchanges (occur in response to factors over which the animal has little or no physiological control)
- Controlled osmotic exchanges (physiologically regulated to aid in maintaining homeostasis)
Factors Contributing to Obligatory Osmotic Exchanges
- Gradients between external and internal environments
- Surface area to volume ratios
- Permeability of the integument (body covering)
- Feeding, metabolic water, and excretion
Endocrine Regulation of Mammalian Kidney
- Aldosterone regulates Na+ reabsorption and K+ secretion by binding to cytosolic receptors in cells of the distal tubule or collecting duct
- Aldosterone activity:
- Increases Na+ and K+ channel synthesis and insertion in apical membrane
- Increases synthesis and number of Na+/K+-ATPases in basolateral membrane
- Net effect: more Na+ and water reabsorption (smaller urine volume produced)
Mammalian Kidney
- Nephron is the functional unit of the kidney
- Nephron has five major regions:
- Bowman's capsule
- Proximal tubule
- Loop of Henle
- Distal tubule
- Collecting duct
- Loop of Henle has three regions:
- Descending limb
- Thin ascending limb
- Thick ascending limb
- The countercurrent multiplier system multiplies the osmotic gradient between the filtrate and interstitium
Elimination of Nitrogenous Wastes
- Amino acid catabolism yields nitrogenous waste products, which are toxic to the animal
- Nitrogenous wastes are excreted through the kidney
Test your knowledge on iono- & osmoregulation in animals with this quiz. The quiz covers topics such as osmoregulatory challenges on land, mammalian kidney structure and function, endocrine regulation, elimination of nitrogenous wastes, and osmoregulation in aquatic animals.
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