HRR: Foundations of Physiology

Question 1

importance of water in the body: how much of the body is water? how much of it is intracellular vs extracellular?

Answer 1

• 50-70% water
• 1/3 extracellular, 2/3 intracellular

Question 2

how much of the extracellular fluid is plasma? how much is interstitial fluid?

Answer 2

1/4 plasma, 3/4 interstitial fluid

Question 3

importance of water in the body: what properties make it unique for our physiology?

Answer 3

• hydrogen bonds give it cohesive strength
• the heat it takes to break the H-bonds in water helps buffer us from temp changes
• water has a high heat of vaporization, letting the evaporation of sweat cool our bodies

Question 4

name common unit of concentration used in medicine

Answer 4

units: mg/dL

Question 5

define “equivalency” and provide examples for KCl and CaCl2

Answer 5

equivalency: amount of charged solute in solution; 1 mol KCL makes 1 K and 1 Cl; 1 mol of CaCl2 makes 2 Eq Ca 2+ and 2 Eq Cl-

Question 6

Differentiate between the terms osmole, osmolarity, osmolality, and tonicity

Answer 6

osmole: number of particles a solute dissociates into
osmolarity: osmoles in 1 L of solvent
osmolality: osmoles in 1 kg of solvent
tonicity: difference of osmolality across a membrane

Question 7

Give the equation to compute the anion gap

Answer 7

anion gap = ([Na]) - ([Cl] + [HCO3])

Question 8

Understand homeostasis in terms of negative and positive feedback in physiological systems (give examples)

Answer 8

negative feedback: blood pressure increases, stimulating baroreceptors. these impulses stimulate the cardioinhibitory center in the brain which causes a decrease in sympathetic tone. blood vessels dilate and resistance is lowered. this helps blood pressure lower.

positive feedback: a break in the blood vessel wall causes platelets to adhere and release chemicals. these chemicals attract more platelets, and the cycle continues.

Question 9

define mass balance

Answer 9

the quantity of stuff in any system is determined by the input and output ratio; if the rate of input and output is the same, quantity is maintained. if more is put in than put out, quantity increases.

Question 10

what happens to red blood cells in a hypertonic solution? hypotonic?

Answer 10

hypertonic: water rushes out and they shrink
hypotonic: water rushes in and the cells lyse

Question 11

give the equation for flow across membranes

Answer 11

deltaP = flow (Q) x resistance