Homeostasis in Mammals
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Questions and Answers

What primary function does the nephron serve in the kidney?

  • Regulating the composition of blood (correct)
  • Producing red blood cells
  • Regulating blood sugar levels
  • Filtering lymphatic fluid

Which of the following substances are retained in the bloodstream during ultrafiltration?

  • Proteins (correct)
  • Glucose
  • Urea
  • Water

What causes the build-up of hydrostatic pressure in the glomerulus?

  • Narrowing of the efferent arteriole (correct)
  • Presence of the glomerular filtrate
  • Widening of the afferent arteriole
  • High blood volume in the renal vein

Which of the following processes occurs after ultrafiltration in the nephron?

<p>Selective reabsorption (A)</p> Signup and view all the answers

What is the composition of the glomerular filtrate formed during ultrafiltration?

<p>Water, glucose, mineral ions, and small molecules (B)</p> Signup and view all the answers

What is the primary cause of Type 1 diabetes?

<p>Autoimmune destruction of insulin-producing cells (B)</p> Signup and view all the answers

Which of the following describes Type 2 diabetes?

<p>It can lead to insulin resistance in cells. (B)</p> Signup and view all the answers

What condition can arise from the buildup of ketone bodies in the blood due to fat breakdown?

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

What is one of the serious complications of high blood glucose concentration?

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

Which factor is NOT associated with the development of Type 2 diabetes?

<p>Insulin dependency from childhood (C)</p> Signup and view all the answers

What major health issue can result from untreated diabetes?

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

What is a possible long-term complication of diabetes?

<p>Kidney damage leading to failure (B)</p> Signup and view all the answers

How does dehydration occur in individuals with high blood glucose levels?

<p>Osmosis pulling water out of cells (B)</p> Signup and view all the answers

What is the primary function of the nephron?

<p>To filter and excrete waste products from the blood (C)</p> Signup and view all the answers

What is the primary effect of ADH binding in the collecting duct?

<p>Increases permeability to urea (B)</p> Signup and view all the answers

What type of cells line the proximal convoluted tubule?

<p>Cuboidal epithelial cells with microvilli (C)</p> Signup and view all the answers

Which structure within the nephron contains a mass of blood capillaries?

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

How do osmoreceptors respond when the water potential of the blood increases?

<p>They suppress thirst signals (C)</p> Signup and view all the answers

Why does the efferent arteriole have a smaller diameter than the afferent arteriole?

<p>To increase blood pressure within the glomerulus (A)</p> Signup and view all the answers

What is the role of cyclic AMP in cell signaling?

<p>It amplifies the signal through enzyme activation (A)</p> Signup and view all the answers

What is the role of the peritubular capillaries?

<p>To facilitate the reabsorption of essential substances (D)</p> Signup and view all the answers

What happens to water reabsorption if ADH concentration in the blood decreases?

<p>Water reabsorption decreases (B)</p> Signup and view all the answers

Which part of the nephron extends from the cortex into the medulla and then back?

<p>Loop of Henle (A)</p> Signup and view all the answers

What initiates the signal cascade in liver cells when stimulated by adrenaline?

<p>Formation of cyclic AMP (C)</p> Signup and view all the answers

Which of the following best describes the interaction between the nervous and endocrine systems?

<p>Both systems maintain constant internal environments (C)</p> Signup and view all the answers

What distinguishes the distal convoluted tubule from the proximal convoluted tubule?

<p>It absorbs fewer capillaries (B)</p> Signup and view all the answers

Which structure becomes increasingly wide as it empties into the pelvis of the kidney?

<p>Collecting duct (B)</p> Signup and view all the answers

How does water reabsorption by the collecting duct affect blood water potential?

<p>Acts to stabilize blood water potential (B)</p> Signup and view all the answers

What defines a hormone's target cell?

<p>Cells with complementary receptors (C)</p> Signup and view all the answers

What is the primary function of antidiuretic hormone (ADH) in the kidneys?

<p>It increases the permeability of collecting ducts to water. (A)</p> Signup and view all the answers

How do osmoreceptors in the hypothalamus detect changes in blood water potential?

<p>By detecting shrinkage from loss of water. (A)</p> Signup and view all the answers

What initiates the production of ADH in the hypothalamus?

<p>A decrease in water potential of the blood. (C)</p> Signup and view all the answers

What is the role of protein kinase activated by ADH in kidney cells?

<p>To promote the fusion of vesicles with the cell membrane. (D)</p> Signup and view all the answers

Which scenario can lower the water potential of the blood?

<p>High salt intake. (C)</p> Signup and view all the answers

What happens when ADH binds to receptors on kidney cell membranes?

<p>It activates a secondary messenger system. (B)</p> Signup and view all the answers

Flashcards

Ultrafiltration

The process of filtering blood in the nephron, where water, glucose, and small molecules are forced out of the glomerular capillaries into Bowman's capsule.

Selective Reabsorption

The selective reabsorption of water and essential nutrients from the glomerular filtrate back into the bloodstream, occurring in the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

Hydrostatic Pressure in the Glomerulus

The pressure created within the glomerulus due to the smaller diameter of the efferent arteriole compared to the afferent arteriole, which drives ultrafiltration.

Peritubular Capillaries

Tiny blood vessels that wrap around the various tubules of the nephron, involved in reabsorbing water and nutrients back into the bloodstream.

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Renal Artery

Blood enters the kidney through this artery, which branches into smaller arterioles leading to the nephrons.

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What is a nephron?

The functional unit of the kidney responsible for filtering blood and producing urine.

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What is the renal capsule?

A cup-shaped structure at the beginning of the nephron that encloses a cluster of capillaries called the glomerulus.

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What is the glomerulus?

A network of blood capillaries within the renal capsule, where filtration of blood occurs.

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What is the proximal convoluted tubule?

The first part of the nephron, characterized by a series of coiled loops surrounded by blood capillaries.

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What is the loop of Henle?

A long, hairpin-shaped loop that extends from the cortex into the medulla of the kidney and back. It plays a crucial role in water reabsorption.

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What is the distal convoluted tubule?

The second part of the nephron, a series of coiled loops surrounded by blood capillaries. It reabsorbs specific substances.

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What is the collecting duct?

A tube into which several distal convoluted tubules empty. It carries urine to the renal pelvis.

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What is the efferent arteriole?

A small blood vessel that carries blood away from the glomerulus and toward the peritubular capillaries.

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ADH (Antidiuretic Hormone)

The hormone that controls the concentration of water and salts in the blood.

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Hypothalamus

A region of the brain that regulates water balance and body temperature.

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Posterior Pituitary

The part of the pituitary gland that stores and releases ADH.

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Collecting Ducts

The region of the nephron where water reabsorption is regulated by ADH.

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Osmoregulation

The process of regulating the concentration of water and salts (solutes) in the blood.

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Effect of ADH on Collecting Ducts

ADH increases the permeability of collecting duct cells to water, allowing more water to be reabsorbed back into the bloodstream.

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Diabetes Insipidus

A condition characterized by excessive urination due to insufficient ADH production.

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Diuresis

The production of large volumes of dilute urine.

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What is Type 1 diabetes?

Type 1 diabetes is an autoimmune disease where the body's immune system mistakenly destroys insulin-producing cells in the pancreas, preventing the production of insulin.

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What is Type 2 diabetes?

Type 2 diabetes is caused by a combination of factors, including genetic predisposition, obesity, and lifestyle choices, leading to insulin resistance or insufficient insulin production.

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What is hyperglycemia?

When the blood glucose concentration remains high due to lack of insulin or insulin resistance, it's called hyperglycemia.

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How does diabetes cause dehydration?

A high blood glucose concentration can lead to dehydration because it reduces the water potential in the blood, causing water to move out of cells.

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What is ketoacidosis?

When the body breaks down fats for energy in the absence of glucose, it produces acidic ketone bodies, leading to ketoacidosis.

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What are some long-term effects of diabetes?

Diabetes can damage blood vessels in the eyes, kidneys, and nerves, leading to potential complications like blindness, kidney failure, and neuropathy.

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What is insulin?

Insulin is a hormone produced by the pancreas that regulates blood glucose levels by allowing glucose to enter cells for energy.

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What is insulin resistance?

Insulin resistance occurs when cells don't respond properly to insulin, preventing glucose from entering cells effectively.

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What is ADH?

A hormone produced by the hypothalamus and secreted by the posterior pituitary gland. It acts on the kidneys to increase water reabsorption, reducing urine volume and concentrating urine.

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What are osmoreceptors?

Specialized cells located in the hypothalamus of the brain that detect changes in blood water potential. They shrink when blood water potential is low, triggering the release of ADH.

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Hormone

A chemical messenger produced by endocrine glands and transported in the blood that acts on specific target cells, tissues, or organs with complementary receptors.

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What is osmosis?

The process by which water is passively transported from a region of higher water potential (low solute concentration) to a region of lower water potential (high solute concentration).

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Homeostasis

The process of maintaining a stable internal environment within an organism, often involving negative feedback loops.

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Negative Feedback

A regulatory mechanism where a change in a factor triggers a response that counteracts the initial change, bringing the system back to its set point.

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How do osmoreceptors respond to low blood water potential?

When blood water potential decreases, water is lost from osmoreceptors via osmosis, causing them to shrink. This shrinkage signals these specialized brain cells to release ADH.

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How does ADH affect the kidneys?

ADH increases the permeability of the distal convoluted tubule and collecting duct to water by activating a second messenger system within the cell.

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Cyclic AMP (cAMP)

A molecule that acts as a second messenger inside a cell, triggered by the binding of a hormone to its receptor on the cell surface.

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Kinase

A type of enzyme that adds a phosphate group to a molecule, often involved in activating or deactivating other enzymes or proteins.

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What is the role of protein kinase in the ADH pathway?

A protein kinase is activated by the second messenger system, which then activates other proteins, ultimately leading to the insertion of aquaporin proteins into the cell membrane.

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What are aquaporins?

Aquaporin proteins are water channels that are inserted into the cell membranes of kidney tubules by ADH, increasing their permeability to water.

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Enzyme Cascade

A series of enzyme activations triggered by a cascade of phosphorylation events, often amplifying a signal initiated by a hormone.

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What is urea?

A small, uncharged molecule that can cross the phospholipid bilayer of the cell membrane, passing through the spaces between the phospholipid molecules.

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Hormone-receptor interaction

The process by which a hormone binds to its receptor on a cell surface, triggering a cascade of events leading to a cellular response.

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Phosphatase

An enzyme that removes a phosphate group from a molecule, often involved in deactivating enzymes or proteins.

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Study Notes

Homeostasis in Mammals

  • Homeostasis is the maintenance of a constant internal environment, including chemical composition, volume, and other features of blood and tissue fluid. It's crucial for cell function despite external changes.

  • Organisms evolved from simple cells to complex, specialized multicellular ones. This specialization created dependencies among cells, requiring coordination for efficient function.

  • Nervous and endocrine systems coordinate bodily functions through communication. The nervous system communicates rapidly, while the endocrine system is slower and less specific.

  • The internal environment consists of extracellular fluids that bathe cells, providing nutrients and removing wastes, protecting them from external conditions.

Importance of Homeostasis

  • Enzymes and other cell proteins are sensitive to changes in pH and temperature. Adverse changes reduce enzyme efficiency and can lead to denaturation or affect membrane protein transport.

  • Changes in water potential of blood and tissue fluids can cause cells to shrink or swell beyond repair, hindering normal function.

Control Mechanisms

  • Control mechanisms involve set points, receptors (detecting stimuli), central control (analyzing information), and effectors (bringing about necessary changes).

  • Negative feedback is a common mechanism in homeostasis, where responses counteract deviations from the set point, restoring balance.

  • Positive feedback (less common) amplifies deviations from the set point, resulting in a more significant change. Examples include childbirth contractions and nerve impulses.

Coordination of Mechanisms

  • Organisms use multiple receptors and effectors, analyzing information from many sources for effective control. Coordination is vital.

  • The brain and other control centers receive information from various receptors and coordinate effector responses to counter change. This integrates information from different sources before response.

Excretion and Kidney Structure

  • Excretion is the removal of metabolic wastes from the body.

  • Urea is produced in the liver from excess amino acids via deamination and the urea cycle.

  • Kidneys are bean-shaped organs responsible for filtering blood and producing urine to eliminate waste products.

  • Key kidney structures include the fibrous capsule, cortex, medulla, renal pelvis, ureter, renal artery, and renal vein.

Nephron Structure

  • The nephron is the functional unit of the kidney, a narrow tube consisting of the renal capsule, proximal convoluted tubule, loop of Henlé, distal convoluted tubule, and collecting duct.

  • Blood vessels like afferent and efferent arterioles, glomerulus, and peritubular capillaries are associated with each nephron.

  • Specialized cells such as podocytes are part of the structure for rapid filtration.

Kidney Function (Ultrafiltration & Selective Reabsorption)

  • Ultrafiltration is the pressure-driven filtration of blood plasma in the glomerulus, producing a filtrate similar to blood plasma but lacking large proteins.

  • Selectively reabsorbing valuable substances (glucose, salts, water) back into the bloodstream from filtrate is a crucial kidney function, ensuring homeostasis.

Control of Water and Solute Concentration (Regulation)

  • The hypothalamus (brain region) monitors water potential of blood. Osmoreceptors detect changes and stimulate the posterior pituitary to release ADH (antidiuretic hormone).

  • ADH increases the permeability of collecting duct cells, allowing more water reabsorption and producing concentrated urine. Maintaining a constant blood water potential is critical for homeostasis.

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Homeostasis in Mammals PDF

Description

Explore the concept of homeostasis in mammals, focusing on how internal environments are maintained despite external changes. Learn about the roles of the nervous and endocrine systems in coordinating bodily functions and the impact of pH and temperature on cell proteins.

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