What does physiology study in living organisms?
The roles, functions, and interactions of organisms and their parts.
How is the human body organized at different levels?
Into chemical, cellular, tissue, organ, systemic, and whole-organism levels.
What forms each level of human body organization?
The association of units from lower levels.
What defines a tissue in biological organization?
A group of similar cells performing the same specialized function.
What is an organ in terms of tissue organization?
A coordinated group of tissues performing a defined function.
What constitutes a system in biological terms?
A group of organs or tissues forming a functional unit.
What is a physiological variable?
A biological measurement that can change over time.
What percentage of the adult body consists of fluid in the course assumption?
60% of the adult body consists of fluid in the course assumption.
What two components make up the extracellular fluid volume?
Plasma and interstitial fluid make up the extracellular fluid volume.
What is the definition of homeostasis according to Claude Bernard?
Homeostasis is the capacity to preserve functional equilibrium despite constraints.
What plasma sodium concentration defines hyponatremia?
A plasma sodium concentration below 120 mmol/L defines hyponatremia.
What effect does hyponatremia have on plasma tonicity and brain cells?
Hyponatremia makes plasma hypotonic and can cause cerebral cellular swelling.
What plasma potassium concentration defines hyperkalemia?
A plasma potassium concentration above 5 mmol/L defines hyperkalemia.
What are the cellular and clinical consequences of hyperkalemia?
Hyperkalemia depolarizes cells and can cause fatal arrhythmias.
Why does body water percentage decrease with age and differ by sex?
Body water percentage decreases with age and is lower in women due to less muscle mass.
How are body fluid volumes measured indirectly?
By allowing a marker to dilute within the compartment of interest.
What are the requirements for a suitable volume marker?
It distributes homogeneously, stays in the compartment, is not metabolized, non-toxic, and measurable rapidly and simply.
What does hematocrit measure?
The percentage of total blood volume occupied by red blood cells.
What is blood volume composed of?
The sum of plasma volume and blood-cell volume.
What is the average plasma volume in blood?
About 3 liters.
What is the average hematocrit range?
Between 40% and 45%.
How much dye is injected in the marker example with 20 mL of 1% solution?
200 mg of dye.
What plasma volume is calculated from 0.060 mg/mL dye concentration in the example?
3.33 liters of plasma volume.
What is an electrolyte in body fluids?
An electrically charged compound among solutes.
Name two examples of cations in body fluids.
Na+ and K+.
Name two examples of anions in body fluids.
Cl− and HCO3−.
What does mass concentration measure?
Mass per volume.
What does molar concentration measure?
Amount of substance per solution volume.
What does molal concentration measure?
Amount of substance per solvent mass.
What does osmolar concentration count?
Particles per solution volume.
How does plasma protein concentration compare to interstitial fluid?
Plasma has 72 g/L, much more than 2 g/L in interstitial fluid.
How does water move across a semipermeable membrane with different osmole concentrations?
Water moves passively from fewer to more osmoles.
What is osmosis?
Osmosis is passive water movement toward higher osmole concentration.
Why does water move toward the compartment with higher osmole concentration in osmosis?
To dilute it and equalize concentrations.
Through which structures does water cross cell membranes and capillary walls?
Through the lipid bilayer and mainly aquaporins.
What is an aquaporin?
A tetrameric membrane protein providing a water pathway.
What is the reference osmolarity used in medicine?
Plasma osmolarity.
What happens to a red blood cell in a hypotonic medium?
It takes up water, swells, and may burst.
Why does a red blood cell swell in a hypotonic medium?
Because the cell is more concentrated than its environment.
What occurs to water movement in a red blood cell in an isotonic medium?
Water movements into and out balance.
How does a red blood cell appear in an isotonic medium?
It remains normal.
What happens to water in a red blood cell in a hypertonic medium?
Water leaves the cell toward the external medium.
What effect does a hypertonic medium have on a red blood cell's shape?
The cell shrinks and becomes wrinkled.
What happens to extracellular volume after drinking pure water?
Extracellular volume increases.
What is the final state after water shifts into cells post pure water intake?
Global overhydration with increased body water and weight.
What symptoms can pure-water gain cause?
Nausea, aversion to water, hypertension, and increased diuresis.
What effect does urinary loss of hypertonic fluid have on plasma volume?
It decreases plasma and extracellular volume.
What is the result of urinary loss of hypertonic fluid on body hydration?
Extracellular dehydration with intracellular overhydration.
How does gain of isotonic fluid affect extracellular volume and osmolarity?
It increases extracellular volume without changing osmolarity or osmole quantity.
Why does isotonic fluid gain not change osmolarity?
Because the fluid remains in the plasma.
When can excessive isotonic-fluid gain cause edema?
When interstitial fluid volume increases by more than 30%.
How does the skin remove water from the body?
Through sweat, a hypotonic fluid.
What type of fluid is sweat compared to salt content?
Sweat is hypotonic, richer in water than salt.
How do the kidneys remove water and what is urine's tonicity?
Kidneys remove water through urine, which is hypertonic and richer in salt.
Test your knowledge with 23 questions on Physiology of Body Fluid Compartments.
1. Regarding physiology, which of the following statements are correct?
2. The levels of organization in the human body include:
Review the complete course in the study sheet for Physiology of Body Fluid Compartments.
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