Physiology 14Mar2009 DO NOT DISTRIBUTE - 1 - 1 – Cellular Membranes and Transmembrane Transport of Solutes and Water 1.1) Which of the following is NOT a function of cellular membranes? a) Divide the cell into discrete compartments b) Membrane proteins are involved in transducing signals from the cell to its surroundings c) Allow for the intra- and extra-cellular fluid compositions to remain constant and equal d) Contains enzymes, receptors, and antigens that play central roles in the interaction of regulatory agents in the extracellular fluid e) Allow the localization of particular biochemical processes in specific organelles 1.2) A patient is undergoing a gastrointestinal x-ray with barium contrast. Barium ions in the drink ingested by the patient are highly toxic, but these ions are not absorbed because: a) Barium is insoluble in the hydrophobic exterior of the cell b) Barium is insoluble in the hydrophobic membrane interior c) Barium is insoluble in the hydrophobic interior of the cell d) Barium is soluble in the hydrophilic exterior of the cell e) Barium is soluble in the hydrophilic membrane interior 2) Which of the following is NOT true regarding the fluid-mosaic model? a) Phospholipid or protein "flip-flop" occurs infrequently b) Many of the constituent molecules are free to diffuse in the plane of the membrane c) Most lipids and proteins can move freely in the bilayer plane d) The model is consistent with many of the properties of biological membranes but is not an absolute fact e) A large hydrophilic moiety is the most likely to flip-flop 3) Integral membrane proteins are embedded in the phospholipid bilayer and peripheral proteins are associated with the surface of the membrane. Which of the following best describes how peripheral proteins interact with the membrane? a) By charge interactions with integral membrane proteins b) By charge interactions with integral membrane lipids c) By binding with integral membrane proteins d) By binding with integral membrane lipids e) By binding throughout the phospholipid bilayer 4) What are the two most prevalent phospholipid classes in membranes? a) Lecithins (phosphatidylcholines) and the sphingomyelins b) Phosphatidylserine and phosphatidylethanolamine c) Glycerol and amino d) Choline and amino e) Alcohol and carbohydrate 5.1) Which membrane component buffers the fluidity of the membrane in the presence of agents that tend to fluidize biological membranes, such as general anesthetics? a) Glycoproteins b) Glycolipids c) Cholesterol d) Carbohydrates
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Physiology 14Mar2009
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1 – Cellular Membranes and Transmembrane Transport of Solutes and Water
1.1) Which of the following is NOT a function of cellular membranes?
a) Divide the cell into discrete compartments
b) Membrane proteins are involved in transducing signals from the cell to its
surroundings
c) Allow for the intra- and extra-cellular fluid compositions to remain constant
and equal
d) Contains enzymes, receptors, and antigens that play central roles in the
interaction of regulatory agents in the extracellular fluid
e) Allow the localization of particular biochemical processes in specific
organelles
1.2) A patient is undergoing a gastrointestinal x-ray with barium contrast. Barium ions in
the drink ingested by the patient are highly toxic, but these ions are not absorbed because:
a) Barium is insoluble in the hydrophobic exterior of the cell
b) Barium is insoluble in the hydrophobic membrane interior
c) Barium is insoluble in the hydrophobic interior of the cell
d) Barium is soluble in the hydrophilic exterior of the cell
e) Barium is soluble in the hydrophilic membrane interior
2) Which of the following is NOT true regarding the fluid-mosaic model?
a) Phospholipid or protein "flip-flop" occurs infrequently
b) Many of the constituent molecules are free to diffuse in the plane of the
membrane
c) Most lipids and proteins can move freely in the bilayer plane
d) The model is consistent with many of the properties of biological membranes
but is not an absolute fact
e) A large hydrophilic moiety is the most likely to flip-flop
3) Integral membrane proteins are embedded in the phospholipid bilayer and peripheral
proteins are associated with the surface of the membrane. Which of the following best
describes how peripheral proteins interact with the membrane?
a) By charge interactions with integral membrane proteins
b) By charge interactions with integral membrane lipids
c) By binding with integral membrane proteins
d) By binding with integral membrane lipids
e) By binding throughout the phospholipid bilayer
4) What are the two most prevalent phospholipid classes in membranes?
a) Lecithins (phosphatidylcholines) and the sphingomyelins
b) Phosphatidylserine and phosphatidylethanolamine
c) Glycerol and amino
d) Choline and amino
e) Alcohol and carbohydrate
5.1) Which membrane component buffers the fluidity of the membrane in the presence of
agents that tend to fluidize biological membranes, such as general anesthetics?
a) Glycoproteins
b) Glycolipids
c) Cholesterol
d) Carbohydrates
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e) Phospholipids
5.2) The receptor for cholera toxin and the receptor for A and B blood group antigens are
carbohydrate moieties. These moieties protrude from the external surface of the
membrane and are part of what non-abundant membrane component?
a) Alcohol
b) Glycolipids
c) Glycopeptides
d) Glycoproteins
e) Glycosamines
6) Phospholipids are distributed asymmetrically (and variably) between the inner and
outer lipid monolayer of the membrane. Which of the following groups is found almost
exclusively in the outer monolayer?
a) Proteins
b) Glycolipids
c) Glycopeptides
d) Glycoproteins
e) Glycosamines
7) Which of the following best describes why membranes "pose a formidable barrier" to
most biologically active compounds?
a) Membranes are highly permeable to water-soluble substances
b) Steroids bound to lipids and other nonpolar compounds are blocked from
entering the cell by glycoproteins
c) Biologically active compounds are soluble in the interior of the lipid bilayer
d) Most molecules present in living systems are soluble in nonpolar solvents
e) Most molecules present in living systems are soluble in water
8.1) Clathrin coated pits are involved in which of the following processes?
a) Receptor-mediated endocytosis
b) Non-metabolic endocytosis
c) Phagocytosis
d) Pinocytosis
e) Exocytosis
8.2) Which of the following would be a way for water-soluble (polar) molecules to enter
the cell?
a) Receptor-mediated endocytosis
b) Non-metabolic endocytosis
c) Phagocytosis
d) Pinocytosis
e) Exocytosis
8.3) Influenza viruses have membrane proteins that undergo a dramatic conformational
change to insert a "fusion peptide" into the host cell. The fusion peptide promotes the
fusion of the viral membrane with the plasma membrane of the host cell. What is the
most likely result of this process?
a) The virus and host cell will form a new, larger host cell
b) The host cell will lyse upon fusion
c) The viral genome will enter the host cell
d) The host cell contents will transfer to the virus
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e) The virus and host cell will form a barrier against each other
9.1) Which of the following best describes Brownian motion (diffusion)?
a) The process whereby atoms or molecules move because of their constant
thermal motion
b) The process whereby atoms or molecules move because of their random
thermal motion
c) The process whereby atoms or molecules move because of their constant
kinetic motion
d) The process whereby atoms or molecules move because of their random kinetic
motion
e) The process whereby atoms or molecules move because of their potential
motion
9.2) Imagine a container divided into two compartments by a removable barrier. A much
larger number of molecules of a compound are placed on side A than on side B, and then
the partition is removed. Which of the following statements about diffusion is true?
a) Movement will occur only from side A to side B
b) The rate of diffusion will initially be faster from side B
c) The rate of diffusion will initially be slower from side A
d) When the number of molecules on side A and side B are the same, no more
movement (diffusion) will occur
e) When the number of molecules on side A and side B are the same, the rate of
diffusion will be the same on both sides
10) A typical molecule takes 1-msec to diffuse 1-µm. If diffusion distance is increased by
10-fold, how much longer will the diffusion process need to achieve a given level of
completion?
a) 5 times longer
b) 10 times longer
c) 20 times longer
d) 100 times longer
e) 1000 times longer
11) Which of the following would give the smallest diffusion coefficient of a molecule in
fluid?
a) Large molecule and viscous medium
b) Small molecule and viscous medium
c) Large molecule and non-viscous (thin) medium
d) Small molecule and non-viscous (thin) medium
12) Which of the following is true regarding Fick's first law of diffusion?
a) Membrane area and membrane thickness are directly proportional to flux (J),
while membrane concentration difference is inversely proportional
b) Membrane area and membrane concentration difference are directly
proportional to flux (J), while membrane thickness is inversely proportional
c) Membrane area is directly proportional to flux (J), while membrane
concentration difference and membrane thickness are inversely proportional
d) Membrane area, membrane concentration difference, and membrane thickness
are directly proportional to flux (J)
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e) Membrane area, membrane concentration difference, and membrane thickness
are inversely proportional to flux (J)
13.1) The permeability of membranes to a particular molecule is:
a) Inversely proportional to its solubility on the exterior of the lipid bilayer
b) Inversely proportional to its solubility in the interior of the lipid bilayer
c) Proportional to its solubility on the exterior of the lipid bilayer
d) Proportional to its solubility in the interior of the lipid bilayer
e) Is not related to solubility of the lipid bilayer
13.2) Plasma membranes of many cells contain membrane proteins called aquaporins that
form channels permitting a high rate of water flow across the membrane; higher than
their predicted lipid solubility. If the water channels that pull in water from the kidney
nephrons were defective, what would be the most likely result?
a) No urine output
b) Concentrated urine
c) Non-concentrated urine
d) Inability of lipid-soluble vitamins to cross the membrane
e) Inability of lipid-soluble hormones to cross the membrane
13.3) The permeability of membranes to uncharged, water-soluble molecules ____ as the
size of the molecules ____.
a) Does not change; Changes
b) Increases; Increases
c) Decreases; Decreases
d) Increases; Decreases
e) Decreases; Increase
14.1) Two chambers are separated by a semi-permeable membrane. Chamber A contains
a solute (NaCl) and chamber B contains only water. Pressure is measured in chamber A
as a hydrostatic force is applied to chamber A in the direction of chamber B. Which of
the following could find the osmotic pressure of this system?
a) At 100mMol NaCl, all water moves into chamber A
b) At 127mMol NaCl, water slowly moves into chamber A
c) At 154mMol NaCl, there is no net movement
d) At 181mMol NaCl, water slowly moves into chamber B
e) At 200mMol NaCl, all water moves into chamber B
14.2) The osmotic coefficient (!) accounts for the deviation of the solution from the
ideal. The value of ! is less than 1 for electrolytes of physiological importance and for all
solutes ! approaches 1 as the solution becomes more:
a) Concentrated
b) Dilute
c) Polarized
d) Unpolarized
e) Depolarized
14.3) Osmotic pressure depends primarily on the chemical properties of the solute
present, rather than the colligative properties.
a) True
b) False
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14.4) the osmotic pressure of a solution can be estimated from its freezing point.
a) True
b) False
15.1) At 154 mM NaCl (isotonic), the red cell has a normal volume. If a red blood cell is
put into a 170 mM NaCl solution, the cell will:
a) Remain the same
b) Burst
c) Swell
d) Shrink
e) Dissolve
15.2) A trauma patient presents to the Emergency Department. You setup an intravenous
(IV) line and begin infusing isotonic 0.9% normal saline (0.9NS). As the saline combines
with the blood cells closest to the IV site, the cells will:
a) Dissolve
b) Shrink
c) Swell
d) Burst
e) Remain the same
15.3) Physiologic osmotic pressure is about:
a) 124 milliosmolar
b) 212 milliosmolar
c) 286 milliosmolar
d) 368 milliosmolar
e) 488 milliosmolar
16) Which of the following describes what makes active transport different from
facilitated transport?
a) Moves a substance down its chemical gradient
b) Moves a substance down an electrochemical gradient
c) Pumps a substance with a chemical gradient
d) Pumps a substance with an electrochemical gradient
e) Requires energy
17.1) Movement via a transport protein showing saturation kinetics will reach Km of the
transported substance at what rate of transport?
a) Maximal rate of transport
b) Half maximal rate of transport
c) Quarter maximal rate of transport
d) Initial rate of transport
e) No transport rate change occurs at this point
17.2) Which of the following states that only molecules with the requisite chemical
structure are transported?
a) Chemical formula
b) Saturation kinetics
c) Chemical specificity
d) Competitive inhibition
e) Noncompetitive inhibition
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17.3) If one transport substrate decreases the transport rate of a second substrate by
fighting for binding to the transporter, this is called:
a) Chemical formula
b) Saturation kinetics
c) Chemical specificity
d) Competitive inhibition
e) Noncompetitive inhibition
18.1) The Na+/K+ ATPase pump, which works against a gradient and uses ATP as
energy, is an example of:
a) Competitive inhibition
b) Noncompetitive inhibition
c) Facilitated transport
d) Primary active transport
e) Secondary active transport
18.2) Amino acids getting their energy indirectly from the gradient of Na+ that is itself
undergoing transport (against a gradient), is an example of:
a) Competitive inhibition
b) Noncompetitive inhibition
c) Facilitated transport
d) Primary active transport
e) Secondary active transport
19.1) What class of membrane transport proteins includes Glucose, usually has multiple
!-helices, and involves binding of the substrate from one side, a conformational change
of the protein, then release of the substrate to other side of membrane?
a) Pores
b) Channels
c) Transporters (carriers)
19.2) What class of membrane transport proteins has a very low rate of diffusion through
a closed channel and where accessibility depends on the location of the gated structure?
a) Pores
b) Channels
c) Transporters (carriers)
19.3) What class of membrane transport proteins has a permeation pathway that is
accessible from both sides of the membrane at all times?
a) Pores
b) Channels
c) Transporters (carriers)
20) Epithelial cells are considered polarized due to different ____ sitting on opposite
sides of the membrane (apical versus basolateral plasma membrane).
a) Phospholipids
b) Peripheral proteins
c) Integral proteins
d) Transport proteins
e) Membrane proteins
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2 – Ionic Equilibria and Resting Membrane Potentials
1.1) The force of diffusion (Fd) acts on all particles. In the equation to calculate Fd, the
concentration of a particular species (C) is ____ related and the changing variable (d/dx),
with respect to distance, is ____.
a) Directly; Concentration gradient
b) Reciprocally; Concentration gradient
c) Directly; Voltage across the membrane
d) Reciprocally; Voltage across the membrane
1.2) The force due to the electrical gradient (Fe) applies to ions. In the equation to
calculate Fe, the valence (z) of the ion is ____ related and the changing variable, (d/dx)
with respect to distance, is ____.
a) Directly; Concentration gradient
b) Reciprocally; Concentration gradient
c) Directly; Voltage across the membrane
d) Reciprocally; Voltage across the membrane
1.3) Net force is defined as Fe + Fd, where Fe is “electro-“ and Fd is “-chemical”. For an
ion to passively cross a membrane, Fnet must be at equilibrium and the membrane must
be permeable to the particle. At equilibrium, the net force acting on an ion is:
a) Increasing
b) Constant
c) Decreasing
d) Zero
e) Infinite
2.1) Which of the following must be true for a membrane to be permeable?
a) Permeability coefficient < 0
b) Permeability coefficient = 0
c) Permeability coefficient > 0
2.2) Conductivity is ____ related to resistance and ____ proportional to permeability as
permeability also includes uncharged particles.
a) Directly; Directly
b) Reciprocally; Directly
c) Directly; Inversely
d) Reciprocally; Inversely
3.1) In a normal semi-permeable lipid membrane, Na+ (outside) is ____ and K+ (inside)
is ____ to the membrane.
a) Impermeable; Permeable
b) Permeable; Impermeable
c) Impermeable; Impermeable
d) Permeable; Permeable
3.2) To have a positive current (by the current equation), we would need the flux of K+ to
be ____ and the flux of Na+ to be ____.
a) Positive; Positive
b) Negative; Negative
c) Zero; Zero
d) Negative; Positive
e) Positive; Zero
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3.3) As a negative membrane voltage (Vm) is established, an Fe will be generated for
each ion in solution. For K+, the direction of Fe will be ____ Fd. As K+ fluxes outward,
Vm increases and Fe will be equal to Fd in magnitude. At this point, Fnet will be ____.
a) Opposite that of; Double
b) Opposite that of; Zero
c) The same as; Double
d) The same as; Zero
3.4) A stable Vm will develop (steady resting membrane potential, Vr) when Fnet is ____
for all permeable ions and "net, or flux, is ____. At this point, we have a Donnan-
equilibrium.
a) Negative; Zero
b) Positive; Zero
c) Zero; Zero
d) Negative; Positive
e) Positive; Negative
4.1) If the Nernst equation calculated Vr to be -95mV for a living neuron or muscle cell,
the force due to the electrical gradient (Fe) is ____ the force due to diffusion (Fd), in
magnitude.
a) Greater than
b) Less than
c) Equal to
4.2) For all permeable ions, the Nernst equilibrium potential for an ion (Ei) is equal to:
a) Net force acting upon an ion (Fnet)
b) Net force due to friction (Ffr)
c) Force for diffusion (Fd)
d) Force due to the electrical gradient (Fe)
e) Fd and Fe
5.1) To determine if an ion is in equilibrium at a measured membrane potential, the
Nernst equation must be calculated. This requires measuring:
a) Ion concentrations inside and outside of the cell
b) Ion concentration inside of the cell
c) Ion concentration outside of the cell
d) Flux moving from inside of the cell
e) Flux moving from outside of the cell
Match the following ions their Nernst potentials (Ei):
5.2) Magnesium a) -109mV
5.3) Calcium b) -36mV
5.4) Chloride c) -92mV
5.5) Sodium d) +68mV
5.6) Potassium e) +120mV
6) Which two variables must be equivalent for an ion to be at equilibrium?
a) Ion concentrations inside and outside of the cell
b) Flux and Nernst potential
c) Flux and Membrane potential
d) Membrane potential and Nernst potential
e) Membrane potential and Ion valence
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7) Which of the following is NOT needed for a system to be at a Donnan-equilibrium?
a) "net = 0 and Fnet = 0 for all permeable ions
b) Vr exists (Inet = 0)
c) Ei = Vr for all permeable ionic species
d) All ions are in steady-state at Vr
e) Vr maintenance requires energy
8) Which of the following helps explain why cells do NOT obey a Donnan-equilibrium?
a) The measured Nernst Vr for a muscle cell versus the calculated value
b) The permeable behavior of K+
c) The permeable behavior of Na+
d) The permeable behavior of Cl-
e) The lack of energy expenditure to maintain Vr
9) Which of the following is in agreement between the Donnan-equilibrium concept and
the non-equilibrium steady-state (NESS) concept?
a) Fnet of all permeable ions is zero
b) "net = 0 for all permeable ions
c) Vr=Ei for all permeable ions
d) Expenditure of energy is required to maintain Vr
10.1) The Na/K ATPase pump is essential in maintaining ionic concentrations and moves
Na+ and K+ unequally across the membrane. It actively transports ____ Na+ out of the
cell for every ____ K+ transported into the cell.
a) 1; 2
b) 2; 1
c) 2; 2
d) 2; 3
e) 3; 2
10.2) Some pharmacological agents, such as cardiac glycosides (digitalis, ouabain), work
by inhibiting the Na/K ATPase. This would ____ its rate of activity and ____ Vr.
a) Decrease; Decrease
b) Increase; Increase
c) Decrease; Increase
d) Increase; Decrease
11) Which of the following best describes the chord conduction equation?
a) Membrane potential is the sum of the equilibrium potentials of the membrane-
permeable ions
b) Membrane potential is the sum of the equilibrium potentials of all ions
c) Membrane potential is the weighted average of the equilibrium potentials of the
membrane-permeable ions
d) Membrane potential is the weighted average of the equilibrium potentials all
ions
e) Membrane potential is the reciprocal of the equilibrium potentials of the
membrane-permeable ions
12) Referring to the chord conductance equation. If gCl- = gNa+ = gMg++ = gCa++ = 0,
but gK+ is significant, then what is Em?
a) -109mV
b) -36mV
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c) -92mV
d) +68mV
e) +120mV
3 – Generation and Conduction of Action Potentials
1) For a non-gated (leakage) and regulated (gated) channels, what depends on the size of
the channel and the characteristics of the channel protein?
a) Fd (force of diffusion)
b) Fe (force due to electrical gradient)
c) Vr (Nernst potential)
d) Vm (Membrane potential)
e) g (conductance)
2) For non-gated (leakage) channels, Na+, Cl-, and K+ channels are responsible for
determining:
a) Conductance
b) Resistance
c) The resting cell potential
d) The maximal cell potential
e) Net force
3.1) Blood vessels have channels that open in response to physical stress, like stretching.
What type of channels are these?
a) Chemical/Receptor-gated
b) Mechanical-gated
c) Light-gated
d) Voltage-gated
3.2) Some hormones contain a region near the channel protein with a ligand-bindable
receptor. These gates will only open after a certain number of bindings have taken place
and the probability of opening is high. What type of channels are these?
a) Chemical/Receptor-gated
b) Mechanical-gated
c) Light-gated
d) Voltage-gated
3.3) At rest, a gate is open. As the membrane potential changes enough to reach a specific
point, these gates close. This is a specific type of what kind of channel?
a) Chemical/Receptor-gated
b) Mechanical-gated
c) Light-gated
d) Voltage-gated
4) A single channel can change its state more than once in response to a single stimuli.
The mean time that the channel remains open (or closed), topen, is a characteristic
property of:
a) Chemical/Receptor-gated channels
b) Mechanical-gated channels
c) Light-gated channels
d) Voltage-gated channels
e) Each channel type
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5.1) In the voltage-clamping technique, ____ is injected into a cell and the membrane
potential is clamped at ____ voltage.
a) Current; Zero
b) Voltage; Zero
c) Current; A specific
d) Voltage; A specific
e) Current; Original membrane
5.2) The patch-clamp technique improved on the voltage-clamping technique by allowing
for measurements across ____ ion channels. This is done by plucking a small piece of
membrane with the tip of a micropipette, where the inside of the pipette contains the ____
fluid.
a) Single; Intracellular
b) Multiple; Intracellular
c) Single; Extracellular
d) Multiple; Extracellular
6.1) In a typical voltage-gated sodium channel, there are ____ m-gates and ____ h-gates
from extracellular moving to intracellular.
a) 3; 1
b) 1; 3
c) 2; 1
d) 1; 2
e) 3; 3
6.2) In a typical voltage-gated potassium channel, there are ____ n-gates and ____ h-
gates from extracellular moving to intracellular.
a) 4; 1
b) 1; 4
c) 4; 0
d) 0; 4
e) 4; 4
7.1) For sodium channels, the m-gates are responsible for quickly ____ as the channel
membrane depolarizes and the h-gates are responsible for quickly ____ upon
depolarization.
a) Opening; Opening
b) Closing; Closing
c) Opening; Closing
d) Closing; Opening
7.2) For potassium channels, current is ____ lasting than sodium channels and terminates
after ____, when Vm is made more negative.
a) Shorter; Depolarization
b) Longer; Depolarization
c) Shorter; Repolarization
d) Longer; Repolarization
8.1) For sodium channels, if Vr = -90 and the cell is depolarized by 20mV (to -70mV),
the probability that each m-gate is open is Pm. The probability that each h-gate is open is
Ph. What is the probability that a channel will open, Po?
a) Po = Pm + Ph
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b) Po = Pm * Ph
c) Po = 3Pm + Ph
d) Po = 3Pm * Ph
e) Po = Pm^3 * Ph
8.2) For potassium channels, if Vr = -90 and the cell is depolarized by 20mV (to -70mV),
the probability that each n-gate is open is Pn. What is the probability that a channel will
open, Po?
a) Po = Pn
b) Po = 4Pn
c) Po = Pn + Pn + Pn + Pn
d) Po = Pn * Pn
e) Po = Pn^4
9) The voltage response of the membrane during a small, sustained current injection
(electrotonic response) is best described as:
a) Substantial
b) Transient
c) Stepwise
d) Constantly decreasing
e) Constantly increasing
10) What account for the additional depolarization during local response?
a) Electrical characteristics of the membrane
b) Potassium channels
c) Sodium channels
d) ATPase
e) Electrical transients
11) When current is injected into a membrane and the threshold potential is exceeded,
depolarization is:
a) Transient
b) 10-20mV
c) 10-20mV greater than Vr
d) Proportional to the injected current
e) Maximal/Complete
12) During an action potential, when threshold is reached many ____ gates open and
rapid depolarization occurs. At the peak of the action potential, many ____ gates open as
the original gates close and rapid repolarization occurs. In depolarization and
repolarizaton, the Nernst potentials (E) for both ions are ____.
a) Sodium; Potassium; Reached
b) Potassium; Sodium; Not reached
c) Sodium; Potassium; Not reached
d) Potassium; Sodium; Reached
13.1) Which of the following is the sequence of events in the positive feedback loop for
sodium channels?
a) Vm depolarizes to threshold, Na+ conductance increases, m-gates open,
sodium channels open, Vm depolarizes
b) Vm depolarizes to threshold, sodium channels open, m-gates open,, Na+
conductance increases, Vm depolarizes
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c) Vm depolarizes to threshold, m-gates open, sodium channels open, Na+
conductance increases, Vm depolarizes
d) Vm depolarizes to threshold, Na+ conductance increases, sodium channels
open, m-gates open, Vm depolarizes
e) Vm depolarizes to threshold, m-gates open, Na+ conductance increases,
sodium channels open, Vm depolarizes
13.2) When the cell is depolarized by 60mV, h = 0 (h-gate closed). The cell can
depolarize by more than 60mV because in sodium channels the ____ gate(s) is/are slower
than the ____ gate(s) to changes in Vm. The sodium channel is considered “re-set” when
the ____ gate(s) return to resting value.
a) M; H; H
b) H; M; M
c) M; H; M
d) H; M; H
13.3) For potassium channels, the peak of the action potential has Po = 50% and not the
expected 100% (approximately). This is because n-gates are ____ and ____ occurs before
the channels have time to reach the Po = 99% value.
a) Fast; Repolarization
b) Slow; Repolarization
c) Fast; Depolarization
d) Slow; Depolarization
13.4) As the cell depolarizes, the electrochemical gradient for sodium ____ at a rate that
is ____ than gNa+ increases.
a) Decreases; Faster
b) Increases; Faster
c) Decreases; Slower
d) Increases; Slower
13.5) As the cell repolarizes, the electrochemical gradient for sodium ____ at a rate that
is ____ than gNa+ decreases.
a) Decreases; Faster
b) Increases; Faster
c) Decreases; Slower
d) Increases; Slower
13.6) Chloride leakage channels ____ the process of depolarization (sodium influx) and
____ the process of repolarization (potassium efflux).
a) Speed up; Slow down
b) Slow down; Speed up
c) Speed up; Speed up
d) Slow down; Slow down
14) At the peak of the action potential, approximately ____ of all the voltage-sensitive
sodium channels are open; this being the maximum possible conductance for Na+.
a) 100%
b) 80%
c) 60%
d) 40%
e) 20%
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15) As membrane conductance for a given ion ____, membrane potential will move
toward equilibrium for ____.
a) Increases; That ion
b) Decreases; All ions (equilibrium)
c) Increases; That ion
d) Decreases; All ions (equilibrium)
16) During depolarization, sodium within the cell and potassium outside of the cell is
____. Chlorine concentration is greatest during ____.
a) High; Depolarization
b) Low; Depolarization
c) High; Repolarization
d) Low; Repolarization
17.1) At what point could one determine that the gates and channels have completely
reset to “resting” conditions when comparing to an initial action potential?
a) A stimulus generates no second action potential
b) A small stimulus generates a stunned second action potential
c) A very large stimulus generates a stunned second action potential
d) A stimulus generates a second action potential equal to the first
17.2) Which of the following would occur during the absolute refractory period?
a) A stimulus generates no second action potential
b) A small stimulus generates a stunned second action potential
c) A very large stimulus generates a stunned second action potential
d) A stimulus generates a second action potential equal to the first
17.3) During the relative refractory period, a second action potential can be generated if:
a) The stimulus is much less than the original stimulus
b) The stimulus is equal to the original stimulus
c) The stimulus is much greater than the original stimulus
d) A very short period of time has elapsed
e) No time has elapsed
17.4) The absolute refractory period is a result of inadequate time for resetting of the
____ gates and the relative refractory period is a result of incomplete reactivation of the
____ gates.
a) H; N
b) N; H
c) H; H
d) N; N
e) H; H & N
4 – Synaptic Transmission and Maintenance of Nerve Function
1) Cajal’s “neuron doctrine” proposed that each nerve cell communicates through
“contiguity rather than continuity.” This implies that neurons are:
a) Touching
b) Overlapping
c) Crossed perpendicularly
d) Parallel
e) In close proximity
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2.1) Synthesizing enzymes for neurotransmitters that enter the synaptic cleft are
originally formed in the:
a) Axon terminal
b) Axon hillock
c) Soma
d) Myelinated axons
e) Dendrites
2.2) Which of the following areas of the neuron contains tubulin?
a) Soma
b) Axon
c) Dendrite
d) All of the above
2.3) Which of the following areas can contain myelin?
a) Axon
b) Axon terminal
c) Dendrites
d) Nodes of Ranvier
e) A, B, and C
2.4) Where does generation of action potentials begin?
a) Axon terminal
b) Axon hillock
c) Soma
d) Myelinated axons
e) Dendrites
2.5) Where are the active zones located?
a) Axon terminal
b) Axon hillock
c) Soma
d) Myelinated axons
e) Dendrites
3.1) Myelin is formed by ____ in the central nervous system and ____ in the peripheral
nervous system.
a) Schwann cells; Astrocytes
b) Oligodendrocytes; Satellite cells
c) Astrocytes; Schwann cells
d) Satellite cells; Astrocytes
e) Oligodendrocytes; Schwann cells
3.2) Where are voltage gated ion channels most abundant?
a) Myelenated axon
b) Axon terminal
c) Dendrites
d) Nodes of Ranvier
e) Synaptic cleft
3.3) Analogously, myelin sheaths act electrically as high ____ and low ____ insulators.
a) Resistance; Inductance
b) Inductance; Capacitance
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c) Capacitance; Resistance
d) Resistance; Capacitance
e) Inductance; Resistance
4) What protein is associated with electrical synapses?
a) Cadherin
b) Alpha-actinin
c) Connexin
d) Clathrin
e) Calcium
5.1) What part of the synaptic junction contains acetylcholine esterase?
a) Synaptic vesicles
b) Active zones
c) Alpha-motor-neurons
d) End-plate peaks
e) End-plate troughs
5.2) In the neuromuscular junction, depolarization of the axon terminus leads to:
a) ACh diffusion of 30nm
b) Binding of ACh
c) Opening of chemical-sensitive channels
d) Opening of Ca++ channels
e) Depolarization of the adjacent neuron
5.3) Postsynaptic receptor binding of ACh opens chemical-sensitive ____ channels,
which have an associated ____ in sodium and potassium conductance.
a) Cation; Increase
b) Anion; Increase
c) Cation; Decrease
d) Anion; Decrease
6.1) Which of the following is observed at rest at around 0.5mV?
a) EPSP
b) IPSP
c) MEPP
6.2) Which of the following does NOT happen at the neuromuscular junction?
a) EPSP
b) IPSP
c) MEPP
7) Which of the following can summate to depolarize the postsynaptic muscle cell and
create an action potential?
a) EPSP
b) IPSP
c) MEPP
8.1) Temporal summation involves firing of ____ presynaptic neuron(s), generating a
series of EPSP’s on the postsynaptic cell. Spatial summation involves firing of ____
presynaptic neuron(s), generating multiple EPSP’s on the postsynaptic cell.
a) One; Multiple
b) Two; Multiple
c) Three; One
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d) Multiple; One
e) Multiple; Two
8.2) EPSP’s decay ____, which is caused by the closure of chemically gated ____
channels.
a) Slowly; Potassium
b) Quickly; Potassium
c) Slowly; Sodium
d) Quickly; Sodium
9) An action potential generated at the axon hillock occurs as a proportional response,
rather than a binary response.
a) True
b) False
10) The length constant is defined as the point, between nodes of Ranvier, where what
percentage of the signal is remaining?
a) 100%
b) 63%
c) 50%
d) 37%
e) 0%
11) Regenerative conduction occurs ____ and passive (electronic) conduction occurs
____.
a) Between nodes of Ranvier; Along the entire axon
b) Along the entire axon; Between nodes of Ranvier
c) Between nodes of Ranvier; Between nodes of Ranvier
d) Along the entire axon; Along the entire axon
12.1) The calcium channel essential for neurotransmitter release is a ____ activating
channel responsible for the ____ calcium current.
a) Fast; Inward
b) Slow; Inward
c) Fast; Outward
d) Slow; Outward
12.2) The calcium channel has ____ activation (d-) gate(s) and ____ inactivation (f-)
gate(s).
a) 1; 1
b) 2; 2
c) 1; 2
d) 2; 1
e) 1; 3
13.1) Once calcium enters the cell, it appears to sever the ____ links, which are meant to
hold the vesicle stationary.
a) Tubulin
b) Myosin
c) Actin
d) Connexin
e) Adherin
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13.2) Neurotransmitters are released as ____, with each vesicle adding its contents ____
to the contents released from others.
a) A flowing stream; Exponentially
b) A flowing stream; Incrementally
c) Packets; Exponentially
d) Packets; Incrementally
13.3) The extent of temporal summation and depolarization of the end-plate-potential is
dependent upon:
a) The extend to which ACh is released
b) The strength of the presynaptic stimulus
c) The duration of the presynaptic stimulus
d) The extent to which the channels are activated
e) All of the above
14) A synaptic delay occurs between the arrival of an action potential at the nerve
terminal and the generation of an EPSP at the postsynaptic site. This delay has been
measured in animal models (squid, frog) to be about:
a) 0.2 – 0.5 ms
b) 0.5 – 40 ms
c) 40 – 50.5 ms
d) 55 – 100 ms
e) 112 – 286 ms
15.1) Which of the following would definitely NOT be let through the postsynaptic
membrane by acetylcholine?
a) K+
b) Ca++
c) Cl-
d) Na+
e) H+
15.2) By what process is ACh broken down by AChE into acetate and choline (which is
actively taken back in by the presynaptic axon terminal)?
a) Hydrolysis
b) Reduction
c) Oxidation
d) Hydrogination
e) Ozonolysis
15.3) Which of the following neurotransmitter inactivation mechanisms is associated
with transmitter-sensitive transport molecules and serotonin?
a) Diffusion
b) Reuptake
c) Metabolism
15.4) Which of the following neurotransmitter inactivation mechanisms is associated
with movement out of the narrow synaptic cleft and norepinepherine?
a) Diffusion
b) Reuptake
c) Metabolism
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15.5) Neurotransmitter inactivation by metabolism involves enzymes in the synaptic
cleft, which can include:
a) Norepinepherine
b) Serotonin
c) ACh
d) AChE
e) Choline
16.1) Neuron-to-neuron signaling that utilizes neurotransmitters involves one neuron
releasing and being sensitive to ____ neurotransmitter.
a) 1
b) 2
c) 4
d) 8
e) Many
16.2) Neuron-to-neuron signaling can involve second messengers. Which of the
following is the correct sequence for the cyclic adenosine monophosphate (cAMP)
system? (arrows denote activation)
a) Ion channels open => Receptor proteins => Linking proteins => Enzymes that
synthesize cAMP => Other enzymes
b) Enzymes that synthesize cAMP => Linking proteins => Receptor proteins =>
Other enzymes => Ion channels open
c) Enzymes that synthesize cAMP => Receptor proteins => Linking proteins =>