CHAPTER 27

• What is the primary focus of Chapter 27 in Seeley’s Anatomy & Physiology?

  Fluid, electrolyte, and acid-base balance
• Why is maintaining a homeostatic balance of electrolytes and fluids important?

  It is essential for the proper functioning of the body.
• What percentage of the total body weight is water?

  At least half
• What are the two major compartments that separate the total amount of water in the body?

  Intracellular fluid compartment and extracellular fluid compartment
• What determines the concentration of solutes in body fluids?

  Osmolality (Osm)
• What happens to the concentration of solutes when water is added to a solution?

  The concentration is diluted.
• What occurs when water is lost from a solution?

  The solution becomes more concentrated.
• What is the intracellular fluid compartment composed of?

  All fluids inside the cells of the body
• What percentage of total body weight does the extracellular fluid compartment account for?

  About 20%
• What are the sub-compartments of extracellular fluid?

  Interstitial fluid, plasma, lymph, cerebrospinal fluid, and synovial fluid
• Where is most extracellular fluid found?

  In the interstitial fluid and plasma
• What can cause edema?

  A blockage of the lymphatics
• Where is the highest concentration of bicarbonate ion found?

  In the interstitial fluid
• What are the two major forces that determine fluid movement into and out of the blood?

  Hydrostatic pressure and osmotic pressure
• What happens when osmotic pressures on each side of a plasma membrane are equal?

  There is no net movement of water molecules.
• What occurs if osmotic pressure is higher in the interstitial fluid than in the blood?

  There is a net movement of water out of the blood.
• What is the role of selectively permeable plasma membranes in regulating intracellular fluid?

  They prevent large molecules synthesized by the cell from leaving.
• What are the primary sources of fluid input into the body?

  Food and beverages (90%) and cellular respiration (10%)
• What is the primary route of fluid loss from the body?

  Kidneys (61% of fluid loss as urine)
• What is insensible perspiration?

  Water lost through the skin that regulates heat loss.
• What is the effect of working in the hot sun on water loss?

  The greatest amount of water is lost through the skin.
• What is the sensation of thirst induced by?

  Hypothalamic osmoreceptors, arterial baroreceptors, dryness of the mouth, and stomach distention.
• How do hypothalamic osmoreceptors function in thirst regulation?

  They detect increases in the concentration of extracellular fluid.
• What happens when the solute concentration of extracellular fluid increases?

  Water moves out of osmoreceptors by osmosis, triggering thirst.
• What role do baroreceptors play in thirst regulation?

  They send action potentials to the thirst center in response to low blood pressure.
• How does mouth dryness contribute to the sensation of thirst?

  A reduction in saliva production stimulates sensory neurons to signal thirst.
• What is the effect of stomach distention on thirst?

  It is more influential in decreasing thirst.
• What mechanisms regulate fluid output?

  They influence urine output and reduce thirst.
• Which receptors monitor systemic blood pressure related to fluid output regulation?

  Carotid sinus and aortic arch baroreceptors
• What is dehydration?

  When body fluid volume drops below its set point, increasing osmolarity.
• What is hyperhydration?

  Occurs when too much water is ingested, making extracellular fluid hypotonic.
• What is the consequence of hyperhydration in infants?

  It can be very dangerous due to diluted formulas.
• What are electrolytes?

  Formed when molecules dissociate into ions in water.
• What is the role of sodium in the body?

  It is the dominant extracellular cation that exerts substantial osmotic pressure.
• How do kidneys regulate sodium excretion?

  They are the major route for sodium excretion.
• What effect does aldosterone have on sodium?

  Aldosterone increases sodium reabsorption in the kidneys.
• How does ADH influence fluid balance?

  ADH stimulates both water reabsorption in the kidneys and thirst.
• What is hyponatremia?

  Low plasma sodium levels that can lead to confusion, seizures, and coma.
• What is hypernatremia?

  High plasma sodium levels that can lead to pulmonary edema and muscle convulsions.
• What are the symptoms of hyponatremia?

  Lethargy, confusion, apprehension, seizures, and coma.