Human Physiology: Nephron Function Quiz
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Questions and Answers

What is the process called where substances are selectively moved from the tubule back into the bloodstream?

  • Tubular secretion
  • Tubular reabsorption (correct)
  • Tubular filtration
  • Interstitial exchange

Which process allows the body to eliminate unwanted substances from the bloodstream into the tubule?

  • Tubular filtration
  • Tubular secretion (correct)
  • Tubular reabsorption
  • Glomerular filtration

What percentage of the blood that enters the glomerulus is filtered into Bowman's capsule?

  • 30%
  • 10%
  • 20% (correct)
  • 50%

Which structure surrounds the glomerulus and acts as a filtration barrier?

<p>Bowman's capsule (D)</p> Signup and view all the answers

What is the main function of the nephron during the tubular reabsorption process?

<p>Reclaiming useful substances back into the blood (A)</p> Signup and view all the answers

In which phase of urine formation is glomerular filtration involved?

<p>Filtering of blood (C)</p> Signup and view all the answers

What typically influences the efficiency of glomerular filtration?

<p>Anatomy and size of the glomerulus (A)</p> Signup and view all the answers

Which of the following describes tubular secretion?

<p>Movement from blood to the tubule (B)</p> Signup and view all the answers

What is the primary function of the loop of Henley?

<p>Concentrate urine (C)</p> Signup and view all the answers

What occurs in the descending limb of the loop of Henley?

<p>Urine becomes more concentrated (C)</p> Signup and view all the answers

Which component of the nephron is responsible for reabsorbing variable amounts of water and NaCl?

<p>Distal convoluted tubule and collecting duct (C)</p> Signup and view all the answers

If the filtrate was not processed further after the loop of Henley, how much fluid would potentially be produced per day?

<p>36 liters (A)</p> Signup and view all the answers

What role do the peritubular capillaries play in the nephron?

<p>Secrete hydrogen and potassium into the tubule (B)</p> Signup and view all the answers

Which hormone is primarily involved in regulating water and salt reabsorption in the distal convoluted tubule and collecting duct?

<p>Aldosterone (C)</p> Signup and view all the answers

What is the consequence of the DCT and collecting duct functioning together?

<p>Maintenance of electrolyte balance (C)</p> Signup and view all the answers

In the context of the nephron, what does fine-tuning of the filtrate mean?

<p>Adjusting waste content while retaining water and salt (A)</p> Signup and view all the answers

What is the primary function of the tubular component in the nephron?

<p>To facilitate absorption and secretion (C)</p> Signup and view all the answers

Which part of the nephron is responsible for collecting filtered substances from the glomerulus?

<p>Bowman's capsule (B)</p> Signup and view all the answers

What type of cells compose the tubular component of the nephron?

<p>Single layer of epithelial cells (D)</p> Signup and view all the answers

Why is the tubular component described as 'continuous'?

<p>Each part flows seamlessly into the next. (C)</p> Signup and view all the answers

What role does diffusion play in the nephron's tubular component?

<p>It facilitates the movement of substances between the tubular component and blood. (A)</p> Signup and view all the answers

The tubular component of the nephron is segmented. Which of the following is a characteristic of these segments?

<p>Each segment has a unique permeability profile. (A)</p> Signup and view all the answers

What additional blood vessel network is associated with certain nephrons?

<p>Vasa recta (D)</p> Signup and view all the answers

Where does the nephron originate within the kidney structure?

<p>Cortex (C)</p> Signup and view all the answers

What is the primary function of aldosterone in the body?

<p>To increase sodium reabsorption (C)</p> Signup and view all the answers

Where is aldosterone produced in the body?

<p>Adrenal gland (A)</p> Signup and view all the answers

How does aldosterone affect principal cells in the nephron?

<p>It increases sodium leak channels (B)</p> Signup and view all the answers

What triggers the secretion of aldosterone?

<p>High potassium concentration in blood (B)</p> Signup and view all the answers

What is the role of the sodium-potassium pump in the function of aldosterone?

<p>It pushes sodium out into the peri tubular capillary (A)</p> Signup and view all the answers

What percentage of sodium reabsorption occurs normally in the collecting duct and distal convoluted tubule without aldosterone?

<p>8% (D)</p> Signup and view all the answers

Which condition will most likely stimulate the secretion of aldosterone?

<p>Excessive potassium intake (A)</p> Signup and view all the answers

What is the function of the special cell type called principal cells?

<p>Transporting sodium and potassium (D)</p> Signup and view all the answers

What is the primary function of macula densa cells?

<p>To monitor the composition of filtrate (D)</p> Signup and view all the answers

What do granular cells secrete when they are stimulated?

<p>Renin (D)</p> Signup and view all the answers

What is the primary purpose of the loop of Henley in urine formation?

<p>To concentrate urine by reabsorbing water and salt. (B)</p> Signup and view all the answers

What happens if the glomerular filtration rate (GFR) is too high?

<p>Urine contains more salt and water than normal (C)</p> Signup and view all the answers

What indicates a more concentrated solution?

<p>A higher milli osmolality value. (B)</p> Signup and view all the answers

Which cells have a lesser role compared to granular cells in regulating blood flow?

<p>Masango cells (C)</p> Signup and view all the answers

How does the descending limb of the loop of Henley primarily function?

<p>It allows water to leave the filtrate due to osmosis. (D)</p> Signup and view all the answers

What do macula densa cells signal when they detect an issue in the filtrate composition?

<p>They activate the granular cells (A)</p> Signup and view all the answers

What happens to the concentration of the filtrate as it travels down the descending limb of the loop of Henley?

<p>The filtrate becomes more concentrated. (D)</p> Signup and view all the answers

Which statement best describes granular cells?

<p>They are smooth muscle cells surrounding the afferent arteriole (B)</p> Signup and view all the answers

At what concentration does the filtrate typically enter the loop of Henley?

<p>300 milli osmos per liter. (A)</p> Signup and view all the answers

What do the macula densa cells monitor in the filtrate?

<p>Concentrations of salt and water (D)</p> Signup and view all the answers

What role does the renal medulla play in urine concentration?

<p>It contains high levels of salts that contribute to the osmosis process. (D)</p> Signup and view all the answers

Which cell type is involved in controlling the diameter of glomerular capillaries?

<p>Mesangial cells (D)</p> Signup and view all the answers

What would be the consequence of urinating out a filtrate with a concentration of 1200 milli osmos per liter?

<p>There would be a loss of important salts from the body. (D)</p> Signup and view all the answers

Why is it important to reabsorb salts in the loop of Henley?

<p>Salts are necessary for various bodily functions. (C)</p> Signup and view all the answers

Flashcards

Tubular Reabsorption

The selective movement of substances from the inside of the renal tubule back into the bloodstream. It is how the body chooses to keep certain substances.

Tubular Secretion

The selective movement of substances from the bloodstream into the renal tubule. It's how the body gets rid of unwanted substances.

Glomerular Filtration Rate (GFR)

The rate at which blood is filtered by the glomerulus. This rate is dependent on the anatomy and size of the glomerulus.

Afferent Arteriole

The blood vessel that carries unfiltered blood into the glomerulus.

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Glomerulus

A network of capillaries within the kidney that filters blood. It is responsible for the first step in urine formation.

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Bowman's Capsule

The cup-shaped structure surrounding the glomerulus that collects the filtered fluid.

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Filtration Membrane

The barrier between the glomerulus and Bowman's capsule that controls what substances are filtered from the blood.

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Why GFR is Only 20%

The glomerulus only filters a portion of the blood due to the size and anatomy of the filtration membrane. The filtration membrane is designed to only allow certain substances to pass through, which is influenced by the structure of the glomerulus itself.

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Tubular component

A hollow tube within the nephron that carries filtered fluid from the blood. It's made of a single layer of epithelial cells, allowing for efficient diffusion.

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Diffusion in the tubular component

Substances can move back and forth between the tubular component and the surrounding blood supply. This allows the kidneys to adjust the composition of the final urine.

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Segments of the tubular component

The tubular component is divided into different segments, each with unique permeability properties, allowing for specialized functions.

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Cortex

The outer layer of the kidney where the glomerulus and Bowman's capsule are located.

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Renal medulla

The middle layer of the kidney, where the loop of Henle and collecting duct are located.

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Vasa recta

A special blood vessel network that surrounds the loop of Henle in certain nephrons. It helps regulate the concentration of urine.

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What is the goal of the loop of Henle?

The loop of Henle aims to create a salt gradient in the renal medulla to reabsorb water and salt, resulting in concentrated urine with minimal water and salt.

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What is milliosmolarity?

Milliosmolarity (mOsm) measures the concentration of a solution, indicating the number of solute particles (like salt) per unit volume of water.

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What is the initial concentration of filtrate entering the loop of Henle?

Filtrate entering the loop of Henle has a concentration of about 300 mOsm/L, which is not highly concentrated.

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What is the descending limb of the loop of Henle permeable to?

The descending limb is permeable only to water. This allows water to move out of the filtrate into the surrounding salty medulla.

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What happens to the concentration of filtrate as it descends the loop of Henle?

The filtrate becomes more concentrated as it descends, reaching 1200 mOsm at the bottom. This is due to water leaving the filtrate.

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Why is the concentration of filtrate at the bottom of the loop of Henle a concern?

Despite the concentrated filtrate at the bottom, the body aims to conserve salt. Having 1200 mOsm in urine would mean losing valuable salt.

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What is the role of the ascending limb of the loop of Henle?

The ascending limb reabsorbs salt but is impermeable to water, further concentrating the surrounding medulla.

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Describe the overall process of the loop of Henle.

Through the loop of Henle and its salt gradient, water and salt are reabsorbed, concentrating urine. This helps the body conserve these essential substances.

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Aldosterone's Role

Aldosterone is a steroid hormone produced by the adrenal cortex that helps regulate salt (sodium) levels in the blood. It increases sodium reabsorption in the distal convoluted tubule and collecting duct of the kidney.

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Aldosterone Secretion Trigger

Aldosterone secretion is triggered by a decrease in blood sodium levels or an increase in blood potassium levels.

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Principal Cells

Specialized cells in the collecting duct and distal convoluted tubule of the kidney that are the target of aldosterone.

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Aldosterone's Mechanism

Aldosterone increases sodium reabsorption by increasing the number of sodium leak channels on the lumen side of principal cells and sodium-potassium pumps on the capillary side.

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Sodium Leak Channels

Proteins embedded in the cell membrane of principal cells that allow sodium ions to passively move from the tubule lumen into the cell.

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Sodium-Potassium Pumps

Active transport proteins in the cell membrane of principal cells that pump three sodium ions out of the cell and two potassium ions into the cell.

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Aldosterone's Effect on Reabsorption

Aldosterone increases sodium reabsorption in the collecting duct and distal convoluted tubule, resulting in increased sodium levels in the blood.

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Aldosterone's Impact on Urine

Aldosterone's effect on sodium reabsorption leads to an increase in water reabsorption, resulting in less urine production.

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What are the macula densa cells?

Specialized cells located in the distal convoluted tubule that monitor the composition of the filtrate (fluid filtered from the blood). They act as sensors for salt and water concentration.

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What happens when the macula densa cells detect an issue?

When they detect an error in the filtrate, like too much salt or water, they send a signal to the juxtaglomerular (JG) cells.

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What are JG cells?

Specialized cells located in the walls of the afferent arteriole (blood vessel supplying the glomerulus) that secrete the hormone renin.

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What is the role of renin?

Renin is an enzyme that activates the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and electrolyte balance.

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What are mesangial cells?

Cells found in the space between glomerular capillaries that can contract or relax, controlling the diameter of the capillaries.

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How does the macula densa-JG cell system regulate GFR?

If the GFR is too high, the macula densa cells will send a signal to the JG cells, which will release renin. This leads to a cascade of events that ultimately constrict the afferent arteriole, reducing blood flow to the glomerulus and decreasing GFR.

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What does a high GFR mean for urine?

A high GFR results in more water and salt being present in the urine.

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How do the macula densa cells signal JG cells?

They use a paracrine signal, which means they release a chemical messenger that acts on nearby cells.

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What are the DCT and collecting duct responsible for?

The distal convoluted tubule (DCT) and collecting duct fine-tune the filtrate by secreting hydrogen, potassium, and ammonium, and reabsorbing variable amounts of water and salt.

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What are the three hormones influencing DCT and collecting duct?

Three hormones regulate the activity of the DCT and collecting duct: Aldosterone, ADH, and ANP.

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What is the role of Aldosterone?

Aldosterone promotes sodium reabsorption and potassium excretion in the DCT and collecting duct, leading to increased blood volume and pressure.

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What triggers Aldosterone secretion?

Low blood sodium levels or high blood potassium levels trigger the release of Aldosterone from the adrenal glands.

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What are macula densa cells and JG cells?

Macula densa cells monitor filtrate composition in the DCT. If the filtrate is too concentrated, they signal JG cells to release renin.

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What does renin do?

Renin activates the renin-angiotensin-aldosterone system (RAAS), a hormonal cascade leading to increased blood volume and pressure.

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How do macula densa and JG cells regulate GFR?

Macula densa cells detect changes in filtrate concentration and signal JG cells to release renin. This ultimately constricts the afferent arteriole, reducing blood flow to the glomerulus and decreasing GFR.

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Study Notes

Urinary Physiology

  • Urinary system is a complex and intuitive system
  • Consists of key structures: two kidneys, two ureters, bladder, urethra
  • Kidneys are bean-shaped organs in the lower abdominal region, responsible for waste removal
  • Ureters transport urine from the kidneys to the bladder
  • Bladder is a muscular sac that stores urine
  • Urethra transports urine out of the body
  • Other systems play a role in waste removal, including respiratory, digestive, and sweat glands

Kidney Function

  • Kidneys are major organs of the urinary system, responsible for forming urine
  • Blood flows through the kidneys, where waste and excess substances removed
  • Blood is filtered by nephrons, functional units in the kidney
  • Renal artery brings unfiltered blood to the kidney
  • Blood travels through a network of smaller blood vessels, delivering waste and excess substances to the nephron.
  • Nephrons filter blood, return useful components, and remove waste products as urine
  • Filtered blood is collected as urine, flowing through the renal pelvis and ureter.
  • Urine is expelled from the body via the urethra

Kidney Functions

  • Filtering blood plasma: removing waste products from blood
  • Regulating blood volume and blood pressure: controlling water retention
  • Regulating osmolarity of body fluids: balancing salt and water content in the blood

Nephons

  • Functional units of the kidney
  • Have vascular and tubular components: blood vessels and tubes
  • Blood vessels are called Perry tubular capillaries, surrounding the nephron.
  • Tubular components collect filtrate (filtered blood plasma) becoming urine.
  • Filtration, reabsorption, and secretion are important functions

Glomerular Filtration

  • First step in urine formation
  • Occurs in glomerulus: a cluster of capillaries
  • 20% of blood is filtered into Bowman's capsule
  • Filters out small molecules and ions (water, electrolytes, sugars), but larger molecules (proteins, blood cells) remain

Tubular Reabsorption

  • Second step in urine formation
  • Occurs in the tubules: reabsorbing essential substances back into the blood stream
  • Important substances (water, glucose, electrolytes) and needed components in the filtrate are reabsorbed into blood supply.
  • Important to control salt and water balance in the body.

Tubular Secretion

  • Third step in urine formation
  • Substances are actively transported from the blood into the tubule.
  • Helps to regulate pH and remove additional waste products

Tubular Glomerular Feedback

  • Negative feedback mechanism to regulate glomerular filtration rate
  • Macula densa cells and granular cells (JG cells) are involved.
  • Changes in filtrate composition lead to renin release, affecting blood pressure and GFR

Hormonal Control

  • Several hormones affect urine production and water balance: ADH, Aldosterone, ANP
  • Aldosterone regulates salt reabsorption; ADH regulates water reabsorption
  • ANP regulates blood pressure, impacting GFR

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Description

Test your knowledge on the nephron's role in kidney function with this quiz. Questions focus on the processes of glomerular filtration, tubular reabsorption, and secretion. Understand the essential components and steps involved in urine formation.

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