Page |1
NBME Physiology Questions with Detailed
Verified Answers (100% Correct Answers)
/Already Graded A+
Gap Junctions
Ans: attachment between cells that permit intercellular communication (i.e. current flow and
electrical coupling between myocytes)
J= -PA (C1-C2)
J= (1x10^-5)(100)[(20/100)-(10/100)]
J= 1x10-4 mg/sec
Ans: The urea conc. of blood is 10 mg/ 100mL the urea conc of proximal tubular fluid is 20
mg/ 100 mL. if the permeability to urea is 1x10^-5 cm/sec and the surface area is 100 cm^2
what is the magnitude and direction of the urea flux (diffusion)?
2 K+ for 3 Na+
Digitalis
(cardiac glycoside drug)
Ans: Na/K ATPase exchanges ___ K for ___ Na.
Specific inhibitor of the Na/K ATPase?
SERCA
Ans: Ca++ ATPase in the sarcoplasmic and endoplasmic reticulum?
Omeprazole (proton pump inhibitor)
Ans: The H/K ATPase that pumps protons into the gastric lumen (against their conc. gradient)
is inhibited by what drug?
Osmosis
, Page |2
Ans: Flow of water across a semipermeable membrane from a solution with low solute conc.
to a solution with high solute conc. ?
Increases
Ans: Osmotic pressure ___________ when solute conc. increases.
1 M CaCl2 because the conc. of particles is higher.
Ans: Which has a higher osmotic pressure: 1 M CaCl2 or 1 M KCl?
Isotonic
Hypertonic
Hypotonic
**Water flows from the hypotonic to the hypertonic solution.
Ans: If two solutions have the same osmotic pressure, they are _________
If one solution has a higher osmotic pressure than the other, it is _____________
If one solution has a lower osmotic pressure than the other, it is __________
Reflection coefficient
Rf= 1 means the solute is IMPERMEABLE (100% reflection)
Rf= 0 means the solute is COMPLETELY PERMEABLE
Ans: A number between zero and 1 that describes the ease with which a solute permeates a
membrane?
Rf= 1
Rf=0
Ans: reflection coefficient of serum albumin? (a large solute)
Reflection coefficient of urea? (a small solute)
Small Cations
, Page |3
*will exclude large molecules and anions
Ans: A small ion channel lined with negatively charged groups will be selective for?
Equilibrium potential
**At electrochemical equilibrium, the chemical and electrical driving forces that act on an ion are
*equal and opposite*, and no more net diffusion of the ion occurs.
Ans: Refers to the potential difference that would exactly balance (oppose) the tendency for
diffusion down a concentration gradient?
E Na= +65 mV
E Ca= +120 mV
E K= -85 mV
E Cl= -85 mV
Ans: Approximate equilibrium potentials in nerve and muscle?
E Na= ?
E Ca= ?
E K= ?
E Cl= ?
Depolarization (cell interior becomes less negative)
Repolarization (cell interior becomes more negative
Ans: __________ makes the membrane potential less negative
_________ makes the membrane potential more negative
Inward current
**depolarizes the cell
, Page |4
Ans: Refers to the flow of positive charge into the cell?
(current)
outward current
**hyperpolarizes the cell
Ans: Refers to the flow of positive charge out of the cell?
(current)
NO: Action potentials are *all or nothing*
Ans: Are action potentials different sizes dependent on different magnitudes of stimuli?
Threshold
Ans: The membrane potential at which an action potential is inevitable?
-70 mV
**A result of the high resting conductance to K+ which drives the membrane potential toward the K+
equilibrium potential (-85 mV)
Ans: Normal resting membrane potential?
1. Inward current depolarizes the membrane potential to threshold
2. Depolarization causes opening of Na channels
3. Rapid depolarization occurs due to the increased conductance of Na (inward Na Current)
**brief period where membrane potential is positive
Ans: What causes the upstroke of the action potential?
Repolarization is caused by an *OUTWARD* K+ current
Ans: What causes repolarization of the action potential?
Tetrodotoxin (TTX)
NBME Physiology Questions with Detailed
Verified Answers (100% Correct Answers)
/Already Graded A+
Gap Junctions
Ans: attachment between cells that permit intercellular communication (i.e. current flow and
electrical coupling between myocytes)
J= -PA (C1-C2)
J= (1x10^-5)(100)[(20/100)-(10/100)]
J= 1x10-4 mg/sec
Ans: The urea conc. of blood is 10 mg/ 100mL the urea conc of proximal tubular fluid is 20
mg/ 100 mL. if the permeability to urea is 1x10^-5 cm/sec and the surface area is 100 cm^2
what is the magnitude and direction of the urea flux (diffusion)?
2 K+ for 3 Na+
Digitalis
(cardiac glycoside drug)
Ans: Na/K ATPase exchanges ___ K for ___ Na.
Specific inhibitor of the Na/K ATPase?
SERCA
Ans: Ca++ ATPase in the sarcoplasmic and endoplasmic reticulum?
Omeprazole (proton pump inhibitor)
Ans: The H/K ATPase that pumps protons into the gastric lumen (against their conc. gradient)
is inhibited by what drug?
Osmosis
, Page |2
Ans: Flow of water across a semipermeable membrane from a solution with low solute conc.
to a solution with high solute conc. ?
Increases
Ans: Osmotic pressure ___________ when solute conc. increases.
1 M CaCl2 because the conc. of particles is higher.
Ans: Which has a higher osmotic pressure: 1 M CaCl2 or 1 M KCl?
Isotonic
Hypertonic
Hypotonic
**Water flows from the hypotonic to the hypertonic solution.
Ans: If two solutions have the same osmotic pressure, they are _________
If one solution has a higher osmotic pressure than the other, it is _____________
If one solution has a lower osmotic pressure than the other, it is __________
Reflection coefficient
Rf= 1 means the solute is IMPERMEABLE (100% reflection)
Rf= 0 means the solute is COMPLETELY PERMEABLE
Ans: A number between zero and 1 that describes the ease with which a solute permeates a
membrane?
Rf= 1
Rf=0
Ans: reflection coefficient of serum albumin? (a large solute)
Reflection coefficient of urea? (a small solute)
Small Cations
, Page |3
*will exclude large molecules and anions
Ans: A small ion channel lined with negatively charged groups will be selective for?
Equilibrium potential
**At electrochemical equilibrium, the chemical and electrical driving forces that act on an ion are
*equal and opposite*, and no more net diffusion of the ion occurs.
Ans: Refers to the potential difference that would exactly balance (oppose) the tendency for
diffusion down a concentration gradient?
E Na= +65 mV
E Ca= +120 mV
E K= -85 mV
E Cl= -85 mV
Ans: Approximate equilibrium potentials in nerve and muscle?
E Na= ?
E Ca= ?
E K= ?
E Cl= ?
Depolarization (cell interior becomes less negative)
Repolarization (cell interior becomes more negative
Ans: __________ makes the membrane potential less negative
_________ makes the membrane potential more negative
Inward current
**depolarizes the cell
, Page |4
Ans: Refers to the flow of positive charge into the cell?
(current)
outward current
**hyperpolarizes the cell
Ans: Refers to the flow of positive charge out of the cell?
(current)
NO: Action potentials are *all or nothing*
Ans: Are action potentials different sizes dependent on different magnitudes of stimuli?
Threshold
Ans: The membrane potential at which an action potential is inevitable?
-70 mV
**A result of the high resting conductance to K+ which drives the membrane potential toward the K+
equilibrium potential (-85 mV)
Ans: Normal resting membrane potential?
1. Inward current depolarizes the membrane potential to threshold
2. Depolarization causes opening of Na channels
3. Rapid depolarization occurs due to the increased conductance of Na (inward Na Current)
**brief period where membrane potential is positive
Ans: What causes the upstroke of the action potential?
Repolarization is caused by an *OUTWARD* K+ current
Ans: What causes repolarization of the action potential?
Tetrodotoxin (TTX)
