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Questions and Answers
What is the average percentage of body water in a human?
What is the average percentage of body water in a human?
Dehydration occurs when water gained is greater than water lost.
Dehydration occurs when water gained is greater than water lost.
False
What is the main organ involved in the regulation of body water?
What is the main organ involved in the regulation of body water?
Kidneys
The process by which water and solutes continuously exchange among compartments is called ______.
The process by which water and solutes continuously exchange among compartments is called ______.
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Match the nephron parts with their respective functions:
Match the nephron parts with their respective functions:
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What stimulates the thirst center in the hypothalamus?
What stimulates the thirst center in the hypothalamus?
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The body is in fluid balance when the amounts of water and solutes are present and correctly proportioned among compartments.
The body is in fluid balance when the amounts of water and solutes are present and correctly proportioned among compartments.
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How many nephrons are typically found in each human kidney?
How many nephrons are typically found in each human kidney?
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What is the primary hormone responsible for regulating water balance in the body?
What is the primary hormone responsible for regulating water balance in the body?
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Low levels of ADH lead to concentrated urine and increased body fluid volume.
Low levels of ADH lead to concentrated urine and increased body fluid volume.
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Name one factor that can trigger the release of ADH.
Name one factor that can trigger the release of ADH.
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Dehydration typically results from the loss of __________ fluid (ECF).
Dehydration typically results from the loss of __________ fluid (ECF).
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Match the following conditions with their associated effects:
Match the following conditions with their associated effects:
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What could result from prolonged vomiting or diarrhea?
What could result from prolonged vomiting or diarrhea?
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If water is gained but electrolytes are not, the extracellular fluid (ECF) becomes more concentrated.
If water is gained but electrolytes are not, the extracellular fluid (ECF) becomes more concentrated.
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What is the minimum daily sensible water loss in urine to excrete wastes?
What is the minimum daily sensible water loss in urine to excrete wastes?
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What is the most abundant cation in extracellular fluid (ECF)?
What is the most abundant cation in extracellular fluid (ECF)?
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Potassium (K+) is the most abundant cation in extracellular fluid (ECF).
Potassium (K+) is the most abundant cation in extracellular fluid (ECF).
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What hormone increases renal sodium reabsorption?
What hormone increases renal sodium reabsorption?
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The movement of water between compartments is largely determined by changes in __________ concentration.
The movement of water between compartments is largely determined by changes in __________ concentration.
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Match the following ions with their primary roles:
Match the following ions with their primary roles:
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What happens to cells when the osmolarity of interstitial fluid decreases?
What happens to cells when the osmolarity of interstitial fluid decreases?
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The release of ADH stops when sodium levels are too low.
The release of ADH stops when sodium levels are too low.
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What condition can occur if a person drinks more water than their kidneys can excrete?
What condition can occur if a person drinks more water than their kidneys can excrete?
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Study Notes
Homeostasis: Regulation of Body Water & Electrolyte Balance
- Homeostasis is the regulation of body water and electrolyte balance.
- Body water percentage averages 60%, varying from 45-75%.
- Functions of body water include protecting sensitive tissues, removing waste products, regulating temperature, lubricating joints, and providing a medium for cell function and chemical reactions.
- Body fluids exist in two main compartments: intracellular fluid (ICF) and extracellular fluid (ECF).
- ICF is located inside cells (2/3 of total body water).
- ECF is located outside cells.
- ECF consists of interstitial fluid and plasma.
- Interstitial fluid surrounds cells (3/4 of extracellular fluid).
- Plasma is the fluid component of blood (1/4 of extracellular fluid.)
Fluid Balance
- Two barriers separate ICF and ECF:
- Plasma membrane separates ICF from ECF
- Capillary membrane separates interstitial fluid from plasma.
- Body is in fluid balance when required amounts of water and solutes are present, correctly proportioned, and continuously exchanged between compartments through filtration, reabsorption, diffusion, and osmosis.
Daily Water Gain and Loss
- Daily water gain comes from metabolic water, ingested foods, and ingested liquids.
- Daily water loss comes from GI tract fluids, lungs, skin, and kidneys.
- Amounts are detailed in an image.
Regulation of Body Water Gain
- Primarily determined by the volume of water intake.
- Dehydration occurs when water loss exceeds water gain.
- Dehydration leads to decreased volume and increased osmolarity of body fluids, stimulating the thirst center in the hypothalamus for water intake.
- Other factors affecting water gain include increased blood osmolarity, decreased blood volume, and decreased blood pressure.
Kidneys
- Kidneys are the main organ responsible for water regulation and urine formation.
- They help maintain electrolyte balance.
- Each kidney has millions of nephrons.
Nephron
- Fundamental unit of the kidney.
- Multiple functionally distinct parts, which include glomerulus, proximal convoluted tubules, loop of Henle, distal convoluted tubules, and collecting duct.
- Each part has specific functions, with the combination leading to urine production.
Nephron: Parts & Function
- Glomerulus: acts as a filter of blood.
- Proximal convoluted tubules: reabsorb glucose, salts, and amino acids.
- Loop of Henle: responsible for water reabsorption.
- Distal convoluted tubules: reabsorb salts.
- Collecting duct: reabsorbs water and salts.
Selective Reabsorption in the Nephron
- The nephron reabsorbs water and specific components from the filtrate.
- The image clarifies the reabsorption path of various substances in the different parts of the nephron.
Large Volume of Filtrate
- The kidneys produce a high volume of filtrate (180 liters per day).
- The normal filtration is known as ultrafiltration.
- Components of urine are selectively reabsorbed by the nephron tubules, and waste products (e.g., urea) are concentrated in urine.
Hormone Regulating Water Balance
- The primary water balance hormone is ADH (antidiuretic hormone).
- ADH is produced by the hypothalamus and released from the posterior pituitary.
- ADH increases water reabsorption in the nephron's distal tubules and collecting ducts.
- More ADH = less urine = more concentrated urine
Factors Maintaining/Regulating Body Water Balance
- Several factors maintain body water balance, including: thirst center in hypothalamus, angiotensin II, aldosterone, ANP (atrial natriuretic peptide), and ADH (antidiuretic hormone).
Regulation of Water Output
- Essential for fluid and electrolyte balance.
- Insensible water loss happens through lungs and skin.
- Faeces also account for water output.
- The minimum daily output of water in urine is at least 500ml, essential for excreting waste products.
Influence of ADH on Water Output
- Water reabsorption in collecting ducts is directly related to ADH release.
- Low ADH leads to diluted urine and lower body fluid volume.
- High ADH results in concentrated urine and higher body fluid volume.
- Hypothalamic osmoreceptors regulate ADH release.
- Other factors cause ADH to also change.
Disorders of Water Balance: Dehydration
- Dehydration occurs due to extra cellular fluid (ECF) water loss.
- ECF water loss can be caused by hemorrhage, severe burns etc.
- Signs and symptoms of dehydration include thirst, dry flushed skin, low urine output, weight loss, and dehydration shock.
Disorders of Water Balance: Hyponatremia
- Hyponatremia happens when there's water excess, and the ECF loses sodium (Na+) in body fluids.
- It results in the water moving into cells, which leads to swelling.
If Water is lost but electrolytes are retained
- ECF osmotic concentration rises.
- Water moves from ICF to ECF reducing ICF volume.
- Both ECF and ICF become slightly concentrated but osmotically balanced.
- Homeostatic mechanisms (increased ADH release) result.
If Water is gained but electrolytes are not
- ECF becomes dilute with lower osmotic concentration,
- ADH release decreases.
- Fluid loss.
- Water moves from ECF to ICF, restoring balance
Electrolytes in Body Fluids
- Ions formed when electrolytes dissolve,
- Functions of electrolytes in the body include: controlling osmosis of water, helping maintain acid-base balance, carrying electrical currents, and acting as co-factors.
Movement of Water Between Compartments
- Intracellular and interstitial fluids have the same osmolarity, preventing water shifts.
- Increased osmolarity of interstitial fluid draws water out of cells, causing them to shrink.
- Decreased osmolarity of interstitial fluid causes cells to swell and gain water.
ICF Differs
- ICF has a higher concentration of potassium (K+) than extracellular fluid while ECF has a higher concentration of sodium (Na+).
Sodium (Na+)
- The most abundant cation in ECF.
- Plays a significant role in maintaining fluid and electrolyte balance of ECF.
- The osmolarity of ECF depends largely on sodium concentration in the blood.
- Controlled by aldosterone, ADH, and ANP.
Chloride (Cl-)
- Chloride is a major anion in ECF, along with sodium.
- Helps balance the anion levels of various bodily fluids.
- Plays a role in regulating water loss by either controlling, or being controlled by, levels of ADH in the urine.
Potassium (K+)
- ICF's most abundant cation.
- Essential for establishing resting membrane potential in neurons and muscle fibers, influencing their electrical functions.
- Important for maintaining normal ICF fluid volume.
- Its levels are controlled by hormonal regulation (including aldosterone) and renal (kidney) excretion.
Dangers of Too Much Water
- Drinking too much water can dilute electrolytes in blood (hyponatremia).
- Kidneys have limits in water output.
- It can lead to serious health complications if not corrected.
Series of Events in Water Intoxication
- Excessive water intake with inadequate electrolyte intake leads to water imbalance.
- ECF fluid becomes dilute, increasing water intake into cells, possibly causing cell swelling, and potentially causing serious health problems.
Dialysis
- A procedure for removing waste products and excess fluids from the blood in people whose kidneys are not functioning correctly.
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Description
Test your knowledge on the human body's water regulation and balance. This quiz covers essential concepts like body water percentage, nephron functions, and the role of hormones in hydration. Challenge yourself with questions on dehydration causes and effects.
