Fluid Compartments and Body Composition
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Fluid Compartments and Body Composition

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Questions and Answers

What is the primary composition of body fluids?

  • Lipids and minerals
  • Proteins and carbohydrates
  • Electrolytes only
  • Water and solutes (correct)

    • Which compartment has the highest volume of total body water?

  • Extracellular fluid
  • Intracellular fluid (correct)
  • Interstitial fluid
  • Plasma

    • What percentage of body weight is attributed to total body water in a typical adult?

  • 60% (correct)
  • 70%
  • 40%
  • 50%

    • Which fluid is considered part of the interstitial fluid?

    <p>Lymph</p> Signup and view all the answers

    How does water content change with age?

    <p>Declines to about 45%</p> Signup and view all the answers

    Which of the following is classified as a non-electrolyte?

    <p>Glucose</p> Signup and view all the answers

    What is a significant reason for water balance disorders?

    <p>Electrolyte imbalance</p> Signup and view all the answers

    Which physiological factor increases total body water content?

    <p>Higher testosterone levels</p> Signup and view all the answers

    What is the minimum daily sensible water loss in urine required to excrete wastes?

    <p>500 ml</p> Signup and view all the answers

    What effect does an increase in Antidiuretic Hormone (ADH) have on urine concentration?

    <p>Urine becomes concentrated</p> Signup and view all the answers

    What type of feedback system regulates the release of ADH?

    <p>Negative feedback</p> Signup and view all the answers

    Where are osmoreceptors located that sense ECF solute concentration?

    <p>In the hypothalamus</p> Signup and view all the answers

    What happens to the body fluids when ADH levels decrease?

    <p>Body fluids decrease volume</p> Signup and view all the answers

    What triggers the release of antidiuretic hormone (ADH)?

    <p>Low blood pressure</p> Signup and view all the answers

    Which hormone is responsible for stimulating water reabsorption in the collecting ducts?

    <p>Antidiuretic Hormone (ADH)</p> Signup and view all the answers

    What is the general response of baroreceptors in conditions of high blood pressure?

    <p>Inhibit ADH release</p> Signup and view all the answers

    Which condition is characterized by ECF water loss?

    <p>Dehydration</p> Signup and view all the answers

    What is the primary ion concentration monitored by osmoreceptors that influences ADH release?

    <p>Sodium (Na+)</p> Signup and view all the answers

    What is a potential consequence of dehydration?

    <p>Mental confusion</p> Signup and view all the answers

    What is the primary result of hypotonic hydration?

    <p>Cell swelling</p> Signup and view all the answers

    Which mechanism leads to an atypical accumulation of interstitial fluid (IF)?

    <p>Increased capillary permeability</p> Signup and view all the answers

    How does renal insufficiency contribute to water balance disorders?

    <p>It causes hypotonic hydration</p> Signup and view all the answers

    What condition results from an impairment in colloid osmotic pressures?

    <p>Oedema</p> Signup and view all the answers

    What is a common treatment for hypotonic hydration?

    <p>Hypertonic saline</p> Signup and view all the answers

    What effect does increased colloid osmotic pressure in interstitial fluid have on blood pressure?

    <p>It lowers blood pressure due to fluid being drawn from the blood</p> Signup and view all the answers

    Which ion is most critical for regulating extracellular fluid (ECF) volume and water distribution?

    <p>Sodium (Na+)</p> Signup and view all the answers

    What regulates sodium balance in the body?

    <p>Hormonal and neural control linked to blood pressure</p> Signup and view all the answers

    Which hormone is primarily responsible for the reabsorption of sodium in the kidneys?

    <p>Aldosterone</p> Signup and view all the answers

    Where in the nephron is the majority of sodium reabsorption occurring?

    <p>Proximal tubules</p> Signup and view all the answers

    What happens to sodium during the filtration process in the nephron?

    <p>Sodium is never secreted into the filtrate</p> Signup and view all the answers

    Which of the following mechanisms is not part of sodium transport regulation?

    <p>Sodium secretion into sweat</p> Signup and view all the answers

    How is excess potassium (K+) affected by aldosterone?

    <p>Leads to potassium secretion in exchange for sodium</p> Signup and view all the answers

    What bodily functions do electrolytes primarily control?

    <p>Fluid movements and membrane permeability</p> Signup and view all the answers

    Which of the following is NOT a way electrolytes are lost from the body?

    <p>Digestion</p> Signup and view all the answers

    What is the primary trigger for the release of aldosterone?

    <p>Elevated potassium levels in extracellular fluid</p> Signup and view all the answers

    How does angiotensin II affect kidney function?

    <p>Stimulates sodium reabsorption</p> Signup and view all the answers

    What effect does Atrial Natriuretic Peptide (ANP) have on blood pressure?

    <p>Decreases both blood pressure and blood volume</p> Signup and view all the answers

    In which part of the body is aldosterone produced?

    <p>Adrenal cortex</p> Signup and view all the answers

    What is the primary function of ADH in relation to sodium?

    <p>Allows water to follow sodium</p> Signup and view all the answers

    Which of these physiological actions does aldosterone NOT perform?

    <p>Promotes diuresis</p> Signup and view all the answers

    What is the relationship between K+ levels in the ECF and aldosterone secretion?

    <p>Increased K+ levels trigger aldosterone release</p> Signup and view all the answers

    What releases Atrial Natriuretic Peptide (ANP) in response to increased blood pressure?

    <p>Atrial myocytes</p> Signup and view all the answers

    Which of the following effects does not result from the action of renin-angiotensin-aldosterone mechanism?

    <p>Inhibition of vasoconstriction</p> Signup and view all the answers

    What effect does an increase in blood pressure have on the release of renin?

    <p>Inhibits renin release</p> Signup and view all the answers

    Study Notes

    Fluid Compartments

    • Total body water is approximately 60% of body weight.
    • Two main fluid compartments: intracellular fluid (ICF) and extracellular fluid (ECF).
    • ICF is approximately 2/3 of total body water, ECF is approximately 1/3
    • ECF is further divided into plasma and interstitial fluid.
    • Extracellular fluid (ECF) is composed of:
      • Plasma (~3 L)
      • Interstitial Fluid (IF) (~13 L)
      • Other (Lymph, Cerebrospinal fluid (CSF), Humors of the eyes, Synovial fluid, Serous fluid, Gastrointestinal secretions)

    Composition of Body Fluids

    • Water acts as a universal solvent.
    • Solutes are dissolved substances in water and are either electrolytes or non-electrolytes.
    • Electrolytes are charged particles and include sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate.
    • Non-electrolytes are uncharged particles, such as glucose, lipids, creatinine, and urea.

    Regulation of Water Output

    • Water loss occurs through obligatory and sensible mechanisms.
    • Obligatory water loss refers to the continual loss of water from the skin and lungs.
    • Sensible water loss includes water loss through urine and faeces, which is subject to physiological regulation.
    • The body requires a minimum daily waste excretion volume of 500 ml through urine.

    Regulation of Water Output: Antidiuretic Hormone (ADH)

    • ADH is a hormone released from the posterior pituitary gland.
    • Main role is to control water reabsorption in the kidneys.
    • ADH release is triggered by an increase in ECF osmolality (concentration of solutes).
    • High ADH leads to concentrated urine to conserve water, and low ADH leads to dilute urine, losing water.
      • Other triggers for ADH release include:
        • Changes in blood volume or pressure (e.g., low blood pressure).
        • Blood vessel baroreceptors.
        • Renin-angiotensin-aldosterone mechanism.

    Water Balance Disorders

    • Dehydration is a condition characterized by excess ECF water loss

      • Causes: Haemorrhage, burns, vomiting or diarrhea, sweating, water deprivation, diuretics, endocrine disturbances.
      • Symptoms: "cottony" mouth, thirst, dry skin, low urine output.
      • May lead to: weight loss, fever, mental confusion, hypovolemic shock, electrolyte depletion.

    • Hypotonic hydration (water intoxication) is caused by an excess of water in the ECF.

      • Characterized by low ECF osmolality and hyponatremia (low sodium levels).
      • Water moves into cells due to osmosis, causing cells to swell and potentially lead to metabolic disturbances.
      • Treatment involves administering hypertonic saline.

    • Oedema is the accumulation of fluid in the interstitial space (IF) leading to swelling.

      • Causes include:
        • Increased capillary hydrostatic pressure due to factors like incompetent venous valves, blood vessel blockage, congestive heart failure.
        • Increased capillary permeability due to inflammation.
        • Decreased venous return to blood caused by imbalances in colloid osmotic pressures, leading to fluid retention.

    Electrolyte Balance

    • Electrolytes play a crucial role in regulating fluid movements, providing minerals for nerve excitability, secretory activity, and membrane permeability.
    • Electrolyte balance primarily refers to salt balance, which is essential for maintaining fluid balance and body function.
    • Sodium (Na+) is the most abundant cation in the ECF, and plays a critical role in regulating fluid movement and osmotic pressure.

    Regulation of Sodium Balance

    • Na+ balance is closely tied to blood pressure and blood volume control mechanisms.
    • Changes in blood pressure or volume trigger neural and hormonal responses to regulate Na+ content via the Renin-Angiotensin-Aldosterone mechanism, Aldosterone, and Atrial Natriuretic Peptide (ANP).

    Regulation of Sodium Balance: Aldosterone

    • Aldosterone is a steroid hormone produced by the adrenal gland.
    • It stimulates the kidneys to increase Na+ reabsorption and K+ secretion, decreasing urine output and increasing blood volume.
    • Triggered by:
      • Angiotensin II (a product of the renin-angiotensin mechanism).
      • High K+ levels in the ECF.

    Regulation of Sodium Balance: Renin-Angiotensin-Aldosterone Mechanism

    • This mechanism is the primary pathway for aldosterone release.
    • A drop in body Na+ content stimulates renin production by the kidneys.
    • Renin triggers the formation of angiotensin II, which ultimately leads to aldosterone release.
    • Angiotensin II also promotes vasoconstriction (narrowing of blood vessels) to increase blood pressure.
    • This mechanism helps to restore normal Na+ and K+ levels in the blood.

    Regulation of Sodium Balance: Atrial Natriuretic Peptide (ANP)

    • ANP is a hormone released by the heart in response to atrial stretch (increased blood pressure).
    • ANP acts to decrease blood pressure and volume.
    • Effects include:
      • Inhibition of ADH, renin, and aldosterone release.
      • Promotion of Na+ and water excretion in the kidneys.
      • Direct vasodilation and the reduction of angiotensin II levels, which is a vasoconstrictor.
    • This helps to lower blood pressure and volume.

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    Lecture 10: Regulation of Body Fluids PDF

    Description

    This quiz explores the fluid compartments of the body, including intracellular fluid and extracellular fluid, and their respective compositions. It also discusses the roles of water as a solvent and the types of solutes in body fluids, including electrolytes and non-electrolytes. Test your knowledge on how water output is regulated in the body.

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