Flashcards in Physiology Deck (42):
What is the formula for Total Body Water?
TBW=ECF+ICF+ luminal fluid =.60 x body weight in kg.
What is ECF composed of?
3/4 ISF and 1/4 plasma
What happens if there is excessive loss of luminal fluid? E.g. losing dilute sweat
Higher salt, smaller compartment of ECF, ICF will decrease to balance it out. ECF and ICF osmolality increases.
What is the distribution of Na+, K+, Cl- in body compartments?
-Na+ is half in bone/other and half in ECF
-K+ is mostly in ICF
-Cl- is mostly in ECF
What is ECF volume determined by?
What happens when excess salt is added to the diet (ignoring thirst)?
Osmolality increases, water moves to the ECF. ECF vol increases, ICF vol decreases.
What happens if there is a loss of isotonic fluid? e.g. blood loss
osmolality remains the same. ECF volume decreases
What happens after you drink a lot of water after excess salt intake?
Osmolality decreases. Volume in ECF decreases and in ICF increases (returns to original state)
Describe the Na, K- ATPase transport system?
Na pump moves Na out and K in.
A person has diarrhea and has low bicarbonate levels might have ...?
How does the body respond to metabolic acidosis?
-want to decrease CO2-->hyperventilation to lose more CO2
A person with COPD is short of breath and is not expelling enough CO2 may have...?
How does the body respond to respiratory acidosis?
-metabolic compensation by increasing acid output and bicarbonate reabsorption
What can cause metabolic alkalosis?
-vomiting, gastric suction for loss of acid
-over ingestion of base
How does the body respond to metabolic alkalosis?
Hypoventilation to increase CO2
What can cause respiratory alkalosis?
Hyperventilation causing loss of CO2
How does the body respond to respiratory alkalosis?
Decrease renal output of acid and renal reabsorption of bicarbonate
What are some extracellular buffers?
bicarbonate, CO2, plasma proteins, inorganic phosphate
What are some intracellular buffers?
bone, proteins, organic and inorganic phosphates
What senses low or high Na mass/volume in the body?
stretch receptors in the atria/cardiovasculature and baroreceptors in cariovasculature
How does the body respond to low sodium mass/volume?
Increase sodium and volume reabsorption by kidney
How does the body respond to high sodium mass/volume?
inhibit renal sodium and volume reabsorption, increase urine output
What are the organ systems that help control potassium levels in the body?
-muscle-potassium stores, releases K when levels are low
-kidney-excretes K when levels are high
What organ systems are responsible for maintaining osmolality?
-brain senses osmolality
-kidneys: dilution or concentration of urine output
-brain regulates thirst output
(vasopression from pituitary=anti diuretic)
What organ systems are responsible for maintaining glucose levels?
pancreas-senses ECF glucose, amino acids, and fatty acids. And releases insulin
How does the cholera toxin cause diarrhea?
It inhibits Na/H antiporter in intestinal villus cells. Activates chloride efflux through Cl channels.-->reduction of NaCl reabsorption, increase in Cl- secretion leads to diarrhea.
How is hyponatremia?
-brain and skull swelling due to excessive water intake
What can loss of excessive dilute sweat and ptyalism (excess saliva) do to ICF, ECF?
Decreases ICF and ECF volume, increases osmolality.
What does intestinal loss of isotonic NaCl do to ICF and ECF volume and osmolality?
ECF volume decreases
ICF volume stays same
osmolality statys the same.
What is conductance determined by?
The number of open ion channels in the cell membrane
What generates voltage differences across membranes?
Different rates of ion diffusion due to difference in size of hydrated ions
What does the chord conductance equation measure?
Membrane potential as weighted average of equilibrium potential of each indiv ion
Define equilibrium potential difference?
Difference in voltage is that is equal to difference in concentration.
What is the mechanism behind high NaCl in sweat of patients with CF?
Defects in Cl channel that reduces membrane permeability to Cl- ions. Cl- not reabsorbed from sweat in sweat glands and Na+ does not follow.
What are types of passive transport?
Voltage gated, ligand gated, ion channels
What is primary active transport?
E.g. Na+/K -ATPase, requires ATP to pump against electrochemical gradient
What is secondary active transport?
Uses potential energy stored in sodium gradient to move Na +another solute across the membrane. E.g. symport: Na/glucose
antiport: Na/Ca2+, Na+/H+
What are cardiac glycosides?
class of drugs that inhibit Na/K ATPase, includes digitalis and ouabain.
What is the mechanism behind CFTR defects in the pancreas?
-Cl-/HCO3- exchanger-Cl- enters the cell (bicarb out) and Cl- recycled out the cell through CFTR
-In CF, pancreatic ducts can't secrete enough NaHCO3 and water because Cl- is not being recycled out the cell
-pancreatic ducts become clogged
How is tracheal epithelia affected in patients with CF? how can it be treated?
-NaCl and water absorption is higher-->airway dehydration
-trachea epithelia normally have both absorptive and secretory functions
-a drug can inhibit epithelial absorption of NaCl and water without affecting secretory function to promote water retention in trachea
What is the major pathways of sodium entry across the apical membrane of absorptive epithelia?
-Na/Solute co transport