136 Physiology QA

[Oak]

Physiology

You have 136 questions in this exam.


1. Our own "internal fluid environment" is considered to be constituted of:
A. interstitial fluid, blood plasma, cytoplasm and cerebrospinal fluid
B. Ocular fluid, interstitial fluid, blood plasma, cytoplasm
C. cerebrospinal fluid, ocular fluid, interstitial fluid and blood plasma
D. cytoplasm, cerebrospinal fluid, ocular fluid and interstitial fluid
E. none of the above


Show answer

Correct Answer: C


2. Which of the following is a homeostatic response to a low blood glucose concentration.
A. decreased food intake
B. decreased secretion of glucagon
C. increased secretion of epinephrine
D. increased secretion of insulin
E. none of the above


Show answer

Correct Answer: C


3. An equilibrium condition exists when:
A. a system is in a homeostatic state
B. a system is in a steady-state
C. a system has opposing forces that counteract one another
D. a system that involves feedback
E. all of the above


Show answer

Correct Answer: C


4. One cell is 50 æm in diameter whereas another is 100 æm in diameter. It would take an uncharged molecule how long to cross the latter compared to the former.
A. same time
B. twice as long
C. four times as long
D. eight times as long
E. none of the above


Show answer

Correct Answer: C


5. What is the osmotic pressure (ã-in atmospheres) at 37øC of a 100 mM glucose solution if the product of the gas constant and temperature is equal to 25.
A. 0.25
B. 2.50
C. 25.0
D. 250
E. 2500


Show answer

Correct Answer: B


6. Mammalian extracellular fluid (ECF) develops an osmotic pressure (ã) of about 7.6 atmospheres. If RT = 25, what is the osmolarity of the ECF?
A. 0.19 M
B. 3.3 M
C. 0.3 M
D. 30 M
E. 300 M


Show answer

Correct Answer: C


7. The combined volume (in liters) of red blood cells and plasma in the average 70 Kg man is approximately:
A. 1 L
B. 2 L
C. 3 L
D. 4 L
E. 5 L


Show answer

Correct Answer: E


8. The physical properties of water include the following:
A. it forms solvent shells around ions
B. it reduces electrostatic attraction between ions
C. it is a dipole
D. it is cohesive
E. all of the above


Show answer

Correct Answer: E


9. The regulatory volume decrease (RVD) of a cell can be due to.
A. activation of the Na/K pump
B. export of K+
C. export of Na+
D. import of taurine
E. import of sorbitol


Show answer

Correct Answer: B


10. Which of the following features describe properties of the voltage-gated Na+ channel.
A. channel is activated by depolarization of the membrane
B. it has a molecular region that confers ion selectivity
C. tetrodotoxin binds to the channel
D. it consists of four domains with membrane spanning segments in each domain
E. all of the above


Show answer

Correct Answer: E


11. An analysis of the physical structure of the nicotinic acetylcholine receptor indicates that:
A. most of the amino acid residues lie within the lipid bilayer including the M1-M4 regions
B. The M1-M4 regions are hydrophilic and the majority of the other residues lie outside the bilayer
C. the majority of amino acid residues lie outside the bilayer and that the M1-M4 regions are hydrophobic
D. the M1-M4 regions are hydrophilic units that lie outside the bilayer and the remainder of the residues lie within the bilayer.
E. none of the above


Show answer

Correct Answer: C


12. In general lipid bilayers are.
A. permeable to ions and gases but impermeable to steroid hormones
B. permeable to ions, gases and steroid hormones
C. impermeable to ions, gases and steroid hormones
D. permeable to steroid hormones and gases but impermeable to ions
E. none of the above


Show answer

Correct Answer: D


13. Which of the following statements could be considered accurate regarding these transporters.
A. the Na/K, Na/HCO3 and Na/Ca2+ transporters are all electrogenic
B. the Na/K transporter is electrogenic but the Na/HCO3 and Na/Ca transporters are not
C. the Na/K, Na/HCO3 transporters are electrogenic but the Na/Ca transporter is not
D. the Na/K, Na/HCO3 and Na/Ca transporters are not electrogenic


Show answer

Correct Answer: A


14. Which of the following groups of pumps utilize an ion gradient as their energy source for moving solutes.
A. Na/K, Na/H, Na/HCO3
B. Na/H, Na/HCO3, Na/Ca
C. Ca-ATPase, Na/K, Na/H
D. Na/K, Na/Ca, Ca-ATPase
E. none of the above


Show answer

Correct Answer: B


15. Reabsorption of glucose in the kidney proximal tubule.
A. involves an Na-glucose transporter and an Na/K exchanger located in the BL membrane
B. involves an Na-glucose transporter and an Na/K exchanger located in the apical membrane
C. involves an Na-glucose transporter in the BL membrane and an Na/K exchanger in the apical membrane
D. involves an Na-glucose transporter in the apical membrane and an Na/K exchanger in the BL membrane
E. none of the above


Show answer

Correct Answer: E


16. Steroid hormones produce their effects by.
A. binding to receptors on the nuclear membrane
B. binding to receptors on the cell membrane
C. stimulating hydrolysis of cell membrane lipids
D. stimulating production of cAMP
E. none of the above


Show answer

Correct Answer: E


17. A curvilinear scatchard plot could suggest the interpretation that:
A. data is not interpretable
B. there is a single association constant
C. the ligand binds to a uniform pool of receptors
D. there are likely two or more pools of receptors with different properties
E. none of the above


Show answer

Correct Answer: D


18. Ca2+ ion.
A. is a co-activator of protein-kinase C
B. has a large electrochemical gradient across the cell membrane
C. is maintained at about 10-4 mM in the cell cytoplasm
D. can be released from the endoplasmic reticulum
E. all of the above


Show answer

Correct Answer: E


19. A cell has an internal K+ concentration of 100 mM and outside the cell the K+ concentration is 10 mM. Assuming the membrane is exclusively permeable to K+ ions, we can calculate from the Nernst equation that the membrane potential is -60 mV (use RT/Fz = 60 mV). If the outside concentration is suddenly increased ten-fold, what would the membrane potential become.
A. no change
B. more negative, but not -120 mV
C. -120 mV
D. more positive, but not zero
E. zero


Show answer

Correct Answer: E


20. By passing current (I) of different amplitudes across a cell membrane, we can obtain a current-voltage relation for the membrane. If the slope of that relation increases but ion concentrations do not, we might conclude that:
A. the equilibrium potential for K+ has changed
B. the potential at which current reverses its sign has changed
C. the resistance of the membrane has increased
D. the number of open pores in the membrane has increased
E. none of the above


Show answer

Correct Answer: D


21. If the sum of the chemical gradient and the electrical gradient across a membrane is zero, it implies that:
A. the system is in a steady-state
B. solutes can be driven "uphill"
C. Solutes can be driven "downhill"
D. that the system is in equilibrium
E. none of the above


Show answer

Correct Answer: D


22. The Gibbs-Donnan equilibrium.
A. is a formal presentation of the way in which the resting potential is maintained
B. presents a formal rationale for colloidal osmotic pressure
C. usually produces about an -80 mV potential difference between two compartments
D. usually produces about an +80 mV potential difference between two compartments
E. none of the above


Show answer

Correct Answer: B


23. The resting membrane potential of a cell is defined as:
A. the Na+ equilibrium potential
B. the K+ equilibrium potential
C. the potential difference (Ein-Eout) across the cell membrane
D. the potential difference (Eout-Ein) across the cell membrane
E. none of the above


Show answer

Correct Answer: C


24. If the measured resting membrane potential (Er) of a cell is found to be the same as the K+ equilibrium potential (EK), it implies that:
A. Cl- ions have the same equilibrium potential at the resting potential
B. Na ions have a more positive equilibrium potential than the resting potential
C. that no other ion species other than K+ has a significant permeability in the resting state
D. that the distribution of all ion species contribute to the resting potential
E. none of the above


Show answer

Correct Answer: C


25. Nitric oxide could be best described as:
A. a membrane receptor
B. a G-coupled protein
C. an intracellular second messenger activated by a G-coupled protein
D. a paracrine signaling agent that is released locally and effects nearby cells
E. being activated by cyclic AMP


Show answer

Correct Answer: D


26. Which of the following are true statements concerning body water.
A. total body water in males is about 40 L and about 30 L in females
B. intracellular water volume is greater than extracellular volume
C. the volume of red blood cells is included in intracellular volume
D. blood plasma is an extracellular fluid with a volume of about 3 L in a 70 Kg man and about 2 L in a 50 Kg woman
E. all of the above


Show answer

Correct Answer: E


27. The time required for a molecule to diffuse across an interstitial fluid layer 1 mm in thickness as opposed to a cell 10 mm in diameter is:
A. 10 times as long
B. 0.01 times as long
C. 0.1 times as long
D. half as long
E. 100 times as long


Show answer

Correct Answer: B


28. Substances with high oil:water partition coefficients readily permeate cell membranes. Which group has high coefficients.
A. peptides, steroid hormones, oxygen
B. steroid hormones, oxygen, ions
C. oxygen, ions, carbon dioxide
D. ions, carbon dioxide, steroid hormones
E. carbon dioxide, steroid hormones, oxygen


Show answer

Correct Answer: E


29. There is an 0.1 M concentration difference of NaCl across an ideal semi-permeable membrane. Given that RT=25 (gas constant x absolute temperature) what is the osmotic pressure difference (Dp) in atmospheres?
A. 0.1
B. 2.0
C. 2.5
D. 5.0
E. 10


Show answer

Correct Answer: D


30. The diffusion coefficient (D) in Fick's diffusion equation takes which set of the following variables into consideration.
A. the area, concentration difference, distance and temperature
B. the concentration difference, distance, temperature and viscosity of solvent
C. the distance, temperature, viscosity of solvent and mass of solute
D. the temperature, viscosity of solvent, mass of solute and area
E. none of the above


Show answer

Correct Answer: E


31. Cooling a cell produces the following effect.
A. nothing
B. swelling since the extracellular solution is hypertonic
C. shrinking since extracellular solution is hypertonic
D. swelling since Na+ enters the cell and water follows it
E. shrinking since Na+ leaves the cell and water follows it


Show answer

Correct Answer: D


32. Integral membrane proteins have polypeptide segments that span the lipid bilayer. They frequently:
A. adopt an alpha-helical configuration
B. contain many hydrophilic amino acids
C. form covalent bonds with cholesterol
D. contain unusually strong peptide bonds
E. none of the above


Show answer

Correct Answer: A


33. A sodium channel that opens in response to an increase in intracellular cGMP is an example of:
A. a second messenger gated ion channel
B. an ion pump
C. a "leak" channel
D. a peripheral membrane protein
E. a voltage-gated channel


Show answer

Correct Answer: A


34. If you wanted to study the effects of intracellular second messengers on the kinetics of ion channels, you would probably select which of the following "patch clamp" methods.
A. inside-out patch
B. outside-out patch
C. the whole cell method
D. the two-electrode whole cell method
E. none of the above


Show answer

Correct Answer: A


35. Which of the following best describes the physico-chemical properties of the nicotinic acetylcholine channel.
A. it can be isolated with saxotoxin, has two binding sites for ACh and forms a tetramere
B. it can be isolated with saxotoxin, has one ACh binding site and forms a pentamere
C. it can be isolated with bungarotoxin, has one ACh binding site and forms a tetramere
D. it can be isolated with bungarotoxin, has two ACh binding sites and forms a pentamere
E. none of the above


Show answer

Correct Answer: D


36. Which of the following channels (receptors) have a similar structural and functional theme.
A. nicotinic, ACh, Na+, b adrenergic
B. nicotinic ACh, Na+, rhodopsin
C. nicotinic ACh, glutamate, rhodopsin
D. nicotinic ACh, glutamate, GABA
E. none of the above


Show answer

Correct Answer: D


37. An index of the affinity of a ligand for its receptor can be obtained by examining:
A. the y-intercept of a Scatchard plot
B. the slope of a Scatchard plot
C. the slope of a biologic dose-response curve
D. the x-intercept of a Scatchard plot
E. none of the above


Show answer

Correct Answer: B


38. G proteins are involved in the coupling of receptors to effector systems such as:
A. ion channels
B. adenylate cyclase
C. IP3
D. Ca2+
E. all of the above


Show answer

Correct Answer: E


39. IP3 is thought to produce its biologic effects by:
A. directly activating calmodulin
B. directly activating protein kinase C
C. promoting release of calcium from intracellular stores in the nucleus
D. activating the a subunit of G proteins
E. none of the above


Show answer

Correct Answer: E


40. Cholera toxin
A. is a potent activator of adenylate cyclase
B. is a potent inhibitor of adenylate cyclase
C. stimulates phosphodiesterase
D. is a potent activator of phospholipase C
E. none of the above


Show answer

Correct Answer: A


41. The electrochemical potential difference can be expressed as:
A. the Goldman equation
B. the Nernst equation
C. the Fick equation for a charged ion
D. the net driving force of the electrical and chemical potential gradients across a membrane
E. none of the above


Show answer

Correct Answer: D


42. An increase in cytosolic calcium:
A. participates in protein kinase C activation
B. results in skeletal muscle contraction
C. decreases the permeability of gap junctions
D. all of the above
E. none of the above


Show answer

Correct Answer: D


43. What do the transporters Na/Ca exchange, Na/H exchange and Na-HCO3 co-transport have in common.
A. they do not utilize ATP as their primary energy source
B. they are good examples of "secondary" transport systems
C. they utilize an ion gradient as their primary energy source
D. all of the above
E. none of the above


Show answer

Correct Answer: D


44. Reabsorption of glucose in the kidney proximal tubule involves:
A. an Na-glucose transporter in the apical membrane and an Na/K exchanger located in the BL membrane
B. an Na-glucose transporter in the BL membrane and an Na/K exchanger located in the apical membrane
C. an Na-glucose transporter in the BL membrane and facilitated transport of glucose in the apical membrane
D. an Na-glucose transporter in the apical membrane and facilitated transport of glucose in the BL membrane
E. none of the above


Show answer

Correct Answer: D


45. Which of the following statements could be considered accurate regarding these transporters.
A. the Na/K, Na/HCO3 and Na/Ca2+ transporters are not electrogenic
B. the Na/K transporter is electrogenic but the Na/HCO3 and Na/Ca transporters are not
C. the Na/K, Na/HCO3 transporters are electrogenic but the Na/Ca transporter is not
D. the Na/K and Na/Ca transporters are electrogenic but the Na/HCO3 transporter is not
E. none of the above


Show answer

Correct Answer: E


46. The membrane potential (Ei-Eo) of a nerve cell would do which of the following if the outside K+ concentration were suddenly doubled (gK remains constant).
A. EM would double
B. EM would become one-half
C. EM would not change
D. EM would become more negative
E. EM would become less negative


Show answer

Correct Answer: E


47. If the potassium conductance (gK) of a resting nerve cell membrane were suddenly doubled with no measurable change in concentration inside or outside the cell, the membrane potential (Ei-Eo) will
A. become more negative
B. remain the same
C. become less negative but not get to zero
D. go to zero
E. go positive


Show answer

Correct Answer: A


48. If the sodium-potassium active transport system (Na/K-ATPase) in the membrane of a nerve cell were turned off completely, which of the following changes would be expected to occur.
A. immediate non-zero net flux of sodium ions across the membrane
B. gradual increase in the internal sodium concentration
C. gradual decrease in the internal potassium concentration
D. gradual increase in internal chloride concentration
E. all of the above


Show answer

Correct Answer: E


49. A cell has 150 mM K+ inside it and the outside K+ concentration is also 150 mM. What is the K+ equilibrium potential for this cell? Use 60 mV for the value of RT/Fz.
A. -60 mV
B. -30 mV
C. +30 mV
D. +60 mV
E. 0 mV


Show answer

Correct Answer: E


50. The electrical potential difference necessary for a single ion to be at equilibrium across a membrane is best described by the
A. Goldman equation
B. van't Hoff law
C. Fick's law
D. Nernst equation
E. reflection coefficient


Show answer

Correct Answer: D


51. A nerve cell has 100 mM K+ and 10 mM Na+ inside and 10 mM K+ and 100 mM Na+ outside. From the Nernst equation you can calculate that EK = -60 mV and ENa = +60 mV. What would the membrane potential be if the K+ channels were closed and the Na+ channels were open.
A. -60 mV
B. -30 mV
C. 0 mV
D. +30 mV
E. +60 mV


Show answer

Correct Answer: E


52. The main property of nerve and skeletal muscle cells that confers excitability and sets them apart from cells that are electrically inexcitable (e.g., blood cells) is that:
A. gNa (Na+ conductance) increases with depolarization
B. gK (K+ conductance) increases with depolarization
C. GCl (chloride conductance) increases with depolarization
D. all of the above
E. none of the above


Show answer

Correct Answer: A


53. Propogation of action potentials in axons and skeletal muscle fibers have which of the following properties.
A. relies on flow of local circuit currents
B. if stimulation occurs at the center, the action potential can spread in both directions
C. occurs when the local circuit currents bring an adjacent region to threshold
D. all of the above
E. none of the above


Show answer

Correct Answer: D


54. The length constant (lambda) of fiber A is found to be 2 mm whereas fiber B is found to have a lambda of 1 mm. One implication of this is:
A. the time constant (tau) of fiber A is greater than fiber B
B. an electrotonic potential change will decrement faster in A than B
C. the conduction velocity of A will be greater than B
D. the conduction velocity of B will be greater than A
E. none of the above


Show answer

Correct Answer: C


55. All of the following describes features of the action potential in a single nerve fiber except:
A. it has a threshold
B. it is graded with stimulation
C. it "overshoots" (i.e., becomes more positive than) zero membrane potential
D. it has a constant conduction velocity
E. its amplitude is dependent on the Na+ concentration gradient across the membrane


Show answer

Correct Answer: B


56. The action of acetylcholine on the postsynaptic membrane of the neuromuscular junction is to:
A. open chemically gated channels to chloride ions
B. open chemically-gated channels to Na+ and K+ ions
C. cause the opening of voltage-gated Na+ channels
D. cause the opening of voltage-gated K+ channels
E. all of the above


Show answer

Correct Answer: B


57. Botulinum toxin blocks neuromuscular transmission by:
A. binding to presynaptic Ca2+ channels, preventing Ca2+ entry
B. binding to postsynaptic receptors interfering with ACh binding
C. inhibiting the action of acetylcholine esterase
D. preventing uptake of choline in the synaptic cleft
E. none of the above


Show answer

Correct Answer: E


58. The following are characteristic properties of the end plate potential (EPP) except:
A. the transmitter is acetylcholine
B. the channel involved is in the "ligand-gated" family
C. it is blocked by curare
D. it is a voltage gated channel
E. all of the above


Show answer

Correct Answer: D


59. The "quantal" nature of synaptic transmission is a tenet that suggests:
A. MEPPs have nothing to do with physiological synaptic transmission except to introduce "noise" into the system
B. MEPPs of different sizes represent the release of transmitter from different vesicles containing various amounts of ACh
C. MEPPs of different sizes are due to summation of unitary events or quanta of ACh release
D. MEPPs are all the same size due to summation of the quantal release of transmitter
E. none of the above


Show answer

Correct Answer: C


60. It is observed that a person diagnosed with myasthenia gravis has symptoms that are exacerbated if he drinks several gin and tonics. A reasonable hypothesis could be:
A. he is drunk and drinking is bad for you
B. quinine may decrease ACh release
C. quinine may bind to the ACh receptor
D. quinine decreases neuromuscular synaptic efficiency that could be due to B or C or both effects combined
E. it is not possible to make an hypothesis


Show answer

Correct Answer: D


61. Drugs such as eserine or prostigmine reduce the symptoms of myasthenia gravis since they:
A. increase the size of the action potential
B. reduce the amplitude of EPPs
C. increase quantal release
D. inhibit the breakdown of acetylcholine
E. decrease quantal release


Show answer

Correct Answer: D


62. According to the relationships expressed by the force-velocity curve for skeletal muscle:
A. the maximal rate of shortening can occur over a wide range of forces
B. the highest rates of shortening occur at the highest forces
C. isometric contraction is not possible
D. there are at least two different forces at which the velocity of shortening will be the same
E. none of the above


Show answer

Correct Answer: E


63. The smallest unit of a normal, physiologic innervated, skeletal muscle that can be activated by a single nerve stimulus is:
A. a single sarcomere
B. a small group of sarcomeres close to the neuromuscular junction
C. a single cell, along its entire length
D. all of the cells comprising a single motor unit
E. none of the above


Show answer

Correct Answer: D


64. A single stimulus applied to a skeletal muscle while it is relaxing from a twitch:
A. will produce an action potential that will have no effect on the muscle force
B. will produce a second twitch whose force adds to the first
C. will cause a more rapid relaxation
D. will slow the relaxation, although no additional force will be produced
E. none of the above


Show answer

Correct Answer: B


65. A skeletal muscle fiber that contains a large number of mitochondria and has a high myoglobin content is likely to
A. fatigue rapidly
B. have a high velocity of shortening
C. be capable of sustained activity
D. have a predominantly anaerobic metabolism
E. all of the above


Show answer

Correct Answer: C


66. The earliest event responsible for mammalian skeletal muscle contracture is:
A. an electrical signal in the T-tubules
B. binding of Ca2+ by troponin
C. exposure of cross-bridge binding sites of actin
D. entry of Ca2+ into the muscle fiber due to the action potential
E. release of Ca2+ from the sarcoplasmic reticulum


Show answer

Correct Answer: A


67. According to the sliding filament hypothesis, which of the following occurs during muscular contraction.
A. the I band and A band shorten and adjacent Z lines move toward one another
B. the I band and A band remain the same and adjacent Z lines move toward one another
C. the I band shortens, the A band remains the same and adjacent Z lines move toward one another
D. the A band shortens, the I band remains the same and adjacent Z lines move toward one another
E. none of the above


Show answer

Correct Answer: C


68. An important early step in the regulation of a smooth muscle contraction is:
A. binding of calcium ions to calmodulin
B. dephosphorylation of myosin light chains by phosphatase
C. crossbridge interaction with myosin
D. calcium uptake by the sarcoplasmic reticulum
E. all of the above


Show answer

Correct Answer: A


69. Smooth muscle is similar to skeletal muscle in the sense that:
A. intracellular calcium (Ca2+) increases due to entry from the extracellular space
B. the critical step in contraction is Ca2+ binding to calmodulin
C. relaxation occurs due to a decrease in intracellular Ca2+
D. intracellular Ca2+ is decreased entirely by pumping activity of the sarcoplasmic reticulum
E. none of the above


Show answer

Correct Answer: C


70. Which of the following best describes activation of smooth muscle.
A. it can be under nervous control
B. it can be under hormonal control
C. some smooth muscle is inherently active, but the activity can be modified by hormones and nervous input
D. histamine and bradykinin can both effect smooth muscle
E. all of the above


Show answer

Correct Answer: E


71. All of the following statements concerning smooth muscle cells (SMC) properties are correct except:
A. SMC have a well-developed sarcoplasmic reticulum
B. SMC are coupled electrically which contributes to "contraction waves"
C. connexins in SMC of the uterus are fewer in number during pregnancy than during parturition
D. the length-tension relation of smooth muscle has a flatter slope than skeletal muscle
E. unlike skeletal muscle, Ca2+ entry through channels contributes to the increase in intracellular Ca2+ observed during contraction in SMC


Show answer

Correct Answer: A


72. The difference between presynaptic (collateral) and postsynaptic inhibition is:
A. presynaptic inhibition shunts the effect of an EPSP whereas postsynaptic inhibition inhibits the IPSP
B. presynaptic inhibition inhibits the IPSP whereas postsynaptic inhibition shunts the effect of an EPSP
C. postsynaptic inhibition involves the effects of an axon collateral whereas presynaptic inhibition does not
D. presynaptic inhibition shunts the effect of an EPSP whereas postsynaptic inhibition involves membrane conductance changes that hyperpolarize the membrane
E. presynaptic inhibition shunts the effect of an EPSP whereas postsynaptic inhibition involves membrane conductance changes that depolarize the membrane


Show answer

Correct Answer: D


73. An electrical synapse is characterized by:
A. fusion of pre- and postsynaptic connexins and a synaptic delay of about 1 msec
B. two-way conduction and in some cases electrical rectification
C. two-way conduction and a 1 msec synaptic delay
D. one-way conduction and a 1 msec synaptic delay
E. none of the above


Show answer

Correct Answer: B


74. The statements below pertain to excitatory synaptic potentials. Pick the most accurate statement.
A. an excitatory postsynaptic potential (EPSP) located on the soma of a cell is more effective at triggering an action potential at the axon hillock than an EPSP of the same size on the cell dendrite
B. all EPSPs are equally effective at triggering an action potential at the axon hillock no matter where they occur on the cell
C. a single EPSP occurring on a dendrite would be as effective as a single EPSP on the cell soma in triggering a postsynaptic action potential
D. spatial summation is more important than temporal summation in triggering an action potential at the axon hillock
E. none of the above are accurate


Show answer

Correct Answer: A


75. While studying a certain CNS synapse you find that GABA (gamma-amino-butyric acid) hyperpolarizes the postsynaptic membrane. You might hypothesize that:
A. the postsynaptic potential could be blocked by strychnine
B. curare could block the postsynaptic potential
C. nicotine could block the postsynaptic potential
D. botulinum toxin could block the postsynaptic potential
E. none of the above


Show answer

Correct Answer: A


76. Lipid solubility of a compound can be measured as a partition coefficient, or log P. A log P of 3 implies:
A. Compound is 3-times more soluble in octanol than in water
B. Compound is 1000-times more soluble in octanol than water
C. Compound is 30-times more soluble in water than in octanol
D. Compound is 1000-times more soluble in water than in octanol
E. Compound is more soluble in water than in lipid


Show answer

Correct Answer: B


77. Fick's law of diffusion describes the relationship between many parameters that affect the number of solute molecules that move across a semipermeable membrane per unit time. These factors include all the following, EXCEPT:
A. The diffusion coefficient
B. Area of the membrane
C. The universal gas constant, R
D. The concentration gradient of solute across the membrane


Show answer

Correct Answer: C


78. For simple diffusion across a cell membrane:
A. Rate is unaffected by chemical or electrical gradient
B. Can occur through aquaporins for amino acids
C. Requires a permease
D. Rate saturates at high solute concentrations
E. Rate is determined in part by lipid solubility


Show answer

Correct Answer: E


79. Osmotic pressure is the hydrostatic pressure necessary to stop osmotic flow across a membrane barrier that is impermeable to some, but not all solutes. Osmotic pressure is dependent on the following, EXCEPT:
A. Area of the membrane
B. B. Van't hoff's law
C. The osmotic coefficient of each solute
D. The concentration of solutes
E. The universal gas constant, R


Show answer

Correct Answer: A


80. Aquaporins have an important role in water reabsorption in the:
A. Skin
B. Lung before birth
C. Collecting ducts of the kidneys
D. Sweat glands
E. Tear ducts


Show answer

Correct Answer: C


81. Diversity in channel structure and function can be due to any of the following reasons EXCEPT:
A. Alternative messenger RNA splicing
B. Heteromultimeric assembly of different alpha subunits
C. Gene duplication and divergence
D. Change in voltage sensor properties
E. Heteromultimeric assembly of alpha and beta subunits


Show answer

Correct Answer: D


82. Voltage-gated sodium channels:
A. Are formed by co-assembly of five identical or similar alpha subunits
B. Have specialized transmembrane domains (S4) that sense transmembrane voltage
C. Are equally permeable to K+ and Na+
D. Are activated by binding of glycine
E. Are activated by a decrease in intracellular ATP concentration


Show answer

Correct Answer: B


83. A dominant-negative effect that results from mutation of an ion channel gene:
A. Occurs when normal and mutant subunits co-assemble to form a nonfunctional channel
B. Is associated with a gain-of-function phenotype
C. Is always associated with a shift in the voltage dependence of channel activation
D. Results in a loss of ion selectivity of the encoded channel
E. Occurs when mutant alpha subunits co-assemble to form a nonconducting channel


Show answer

Correct Answer: A


84. All of the following structural features of potassium channels permit high ion selectivity and high ion throughput rates EXCEPT:
A. A narrow selectivity filter that coordinates 2 potassium ions
B. A selectivity filter determined by three residues (GYG) on each subunit
C. Binding of a K+ to one binding site repulses K+ from a nearby binding site
D. A voltage sensor in the S3 domain
E. A selectivity filter located near the extracellular side of the channel that can easily coordinate K, but not Na ions


Show answer

Correct Answer: D


85. AMPA and Kainate receptors:
A. When activated mediate the fast component of excitatory postsynaptic potentials
B. Are highly permeable to calcium ions
C. Activate a 2nd messenger cascade, but have no ion channel activity
D. When overstimulated cause excitotoxicity
E. Are channels activated by glycine


Show answer

Correct Answer: A


86. Which of the following is correct for ligand-gated ion channels:
A. GABA and glycine activate a Na conductance
B. Activation of GABA or glycine receptors cause excitatory responses at central neurons
C. GABAA and glycine receptors are C1 channels
D. Are formed by co-assembly of six identical subunits
E. Strychnine is a competitive agonist of acetylcholine receptors


Show answer

Correct Answer: C


87. Cyclic nucleotide gated ion channels have an important physiological role in:
A. Propagation of action potentials in nerve axons
B. Photoreceptors of the eye
C. Release of calcium from the sarcoplasmic reticulum of muscle
D. Regulation of insulin secretion from the pancreas
E. Control of action potential duration in the heart


Show answer

Correct Answer: B


88. Which of the following channel types is important for intercellular communication and exchange of small molecules?
A. Ryanodine receptor/ Ca release channel
B. Glutamate receptor channel
C. ATP-sensitive K channel
D. Connexins/gap junction channel
E. Acetylcholine receptor channel


Show answer

Correct Answer: D


89. The Na+/K+ ATPase:
A. Maintains a high intracellular concentration of Na+ in the cell
B. Is a symporter (cotransporter)
C. Is an example of a facilitated transporter
D. Pumps Na+ out of the cell and K+ into the cell
E. Is blocked by glutamate


Show answer

Correct Answer: D


90. All of the following statements describe properties of epithelia EXCEPT:
A. The apical surface faces toward the lumen of the organ
B. The basolateral surface faces toward the blood vessel
C. Tight junctions are located between adjacent cells and limit permeability of solutes and water
D. The transepithelial potential difference of leaky epithelia is less than tight epithelia
E. Secretory epithelia are found in the saliva glands and sweat glands


Show answer

Correct Answer: D


91. Which of the following describes an important difference between passive and active transporters?
A. Only passive transporters move Na across the cell
B. Only active transporters require hydrolysis of ATP
C. Passive transporters are always cotransporters, whereas active transporters are uniporters
D. Only passive transporters move substances against a concentration gradient


Show answer

Correct Answer: B


92. A function of leaky absorptive epithelia include one of the following:
A. Transport water and ions from the intracellular fluid to the lumen of the kidney
B. Move glucose from intestinal lumen into the blood
C. Transport water and ions from the lumen to the intracellular fluid of the kidney
D. Secretion of water and salts from sweat glands
E. Secretion of mucus in the small intestine


Show answer

Correct Answer: C


93. Choose one correct answer.
A. Membrane potential (Vm) becomes more negative during the upstroke of an action potential
B. Hyperpolarization of membrane potential means that resting Vm becomes more negative
C. Depolarization of Vm means it becomes more negative
D. The upstroke of an action potential occurs during the repolarization phase of the action potential


Show answer

Correct Answer: B


94. Choose one correct answer.
A. Most of the body's water is in the interstitial fluid
B. In a resting axon or ventricular cell the driving forces acting on sodium ions (Na+) include: an inwardly directed concentration gradient and an outwardly directed electrical gradient
C. If influx of a substance into a cell is 5 mM/min and efflux of the same substance is 4mM/min, then net flux is 1mM/min out of the cell
D. The number of potassium ions required to establish a transmembrane potential is very small compared to the total number of potassium ions inside the cell


Show answer

Correct Answer: D


95. Assume you are studying a skeletal muscle cell with a resting Vm of -100mV and a sodium equilibrium potential of +50 mV. Under these conditions what is the value of the electrochemical gradient (ie, the driving force ) acting on Na+ ions. Choose one correct answer.
A. +100mV
B. -50mV
C. -150mV
D. +150mV


Show answer

Correct Answer: C


96. Choose one correct answer.
A. Membrane channels are analogous to capacitors
B. The lipid bilayer portion of the cell membrane acts like a resistor
C. The efflux of K+ ions through channels during an action potential is defined as an inward ionic current
D. The equilibrium potential of an ion (Vion) is the electrical gradient across the membrane that exactly balances the concentration gradient of the ion across the membrane


Show answer

Correct Answer: D


97. Assume you are studying a nerve cell with an intracellular K+ concentration of 100 mM and an interstitial K+ concentration of 10 mM . Also assume the cell membrane is only permeable to potassium ions. Choose one correct answer.
A. The resting membrane potential will be -20 mV
B. Both the resting membrane potential and VK will be -60 mV
C. The resting Vm will be -60 mV but VK will be -100mV
D. If interstitial K+ concentration is increased to 100 mM , resting Vm will be +10 mV


Show answer

Correct Answer: B


98. Choose one correct answer.
A. A decrease in gap junctional resistance between cardiac cells will decrease action potential conduction velocity
B. An increase in membrane resistance will increase the distance over which local circuit currents can spread
C. The presence of myelin on axons acts to increase the membrane capacitance of these cells
D. All other factors remaining equal, an increase in cell diameter will decrease action potential conduction velocity


Show answer

Correct Answer: B


99. Choose one correct answer.
A. Vm will depolarize if, during an action potential, the outward ionic currents are less than the inward ionic currents
B. The refractory period of nerve, skeletal and cardiac muscle results from the inactivation of potassium channels
C. Na channels are distributed uniformly along the entire length of a myelinated axon, including the myelinated regions
D. The presence of myelin on axons acts to decrease action potential conduction velocity


Show answer

Correct Answer: A


100. Choose one correct answer.
A. The z-line or z-disk of skeletal and cardiac muscle serves as the anchoring spot for myosin filaments
B. The distance between the z-lines of a sarcomere increases during muscle contraction
C. The large diameter of cardiac transverse tubules facilitates the diffusion of calcium into the interior of the cell
D. Transverse tubules directly connect the interstitial fluid to the intracellular fluid


Show answer

Correct Answer: C


101. Choose one correct answer.
A. The calcium release channels of the sarcoplasmic reticulum (SR) are called dihydropyridine receptors
B. The SR of cardiac muscle is more extensive than that of skeletal muscle
C. If you give a drug to a patient which partially inhibits the SR calcium pump of skeletal muscle, then the rate of muscle relaxation will increase
D. The SR contains the protein calsequestrin that binds calcium and helps increase the Ca2+ storage ability of the SR


Show answer

Correct Answer: D


102. Choose one correct answer.
A. Blockade of the calcium current in cardiac muscle will stimulate calcium-induced-calcium release (CICR)
B. If you give a patient a drug which inhibits Na-Ca exchange, then the rate of relaxation of skeletal muscle will increase
C. Epinephrine and norepinephrine are positive inotropic agents and increase the calcium current of cardiac muscle
D. Cardiac muscle uses recruitment to provide greater force in response to a larger load


Show answer

Correct Answer: C


103. Choose one correct answer.
A. Ca2+ ions bind to the myosin heads during crossbridge cycling in heart and skeletal muscle
B. Under resting conditions, when intracellular calcium concentration is low, tropomyosin acts to block crossbridge cycling in heart and skeletal muscle
C. Troponin C is located on the myosin heads
D. ATP binds to tropomyosin during crossbridge cycling


Show answer

Correct Answer: B


104. Choose one correct answer.
A. Rigor will occur if ATP does not bind to the myosin heads following the power stroke of crossbridge cycling
B. ADP and Pi are released from the myosin heads when the crossbridges are in a resting or relaxed state
C. During an isometric contraction tension increases and muscle length decreases
D. During an isotonic contraction tension increases but muscle length remains constant


Show answer

Correct Answer: A


105. Why does the isometric tension or force generated by a skeletal muscle cell decline when the cell is progressively stretched. Choose one correct answer.
A. The SR becomes damaged
B. The overlap of thick and thin filaments increases
C. The overlap of actin and myosin filaments decrease
D. The Ca2+ transient declines


Show answer

Correct Answer: C


106. Choose one correct answer.
A. Compared to skeletal and cardiac muscle contractions, contractions in smooth muscle are faster to develop and are shorter in duration
B. Rapid stimulation of cardiac muscle will cause it to develop a tetanic contraction
C. Smooth muscle has an extensive transverse tubular system
D. Cardiac muscle operates on the ascending limb of its isometric length-tension curve so that the more the ventricles are filled with blood the greater the pressure they develop during systole


Show answer

Correct Answer: D


107. Choose one correct answer.
A. An agent that increases IP3 production in smooth muscle will cause the muscle to relax
B. Crossbridge cycling in smooth muscle is initiated by calcium binding to troponin C
C. Crossbridge cycling in smooth muscle is initiated by activation of myosin light chain kinase (MLCK) which phosphorylates myosin
D. A drug which inhibits MLCK will cause smooth muscle to contract


Show answer

Correct Answer: C


108. Both ionotropic and metabotropic receptors are involved in synaptic transmission. Which of the following is a true statement concerning these receptors?
A. Metabotropic receptor activation directly gates an ion channel
B. Neurotransmitters activate either ionotropic or metabotropic receptors
C. g-protein-coupled receptors are metabotropic receptors
D. Ionotropic receptor activation regulates slow synaptic events
E. Ionotropic receptor activation initiates a second messenger cascade


Show answer

Correct Answer: C


109. Which of the following statements correctly describes an aspect of the g-protein activation cycle?
A. Heterotrimeric g-proteins bind to the amino terminus of an activated g-protein-coupled receptor
B. The inactive g-protein heterotrimer is associated with GTP
C. The GTPase activity of the alpha-subunit determines how long the g-protein remains active
D. Many active g-protein-coupled receptors are required to activate a single g-protein
E. The beta-gamma subunit composition of the g-protein determines its primary action


Show answer

Correct Answer: C


110. Which of the following is directly involved in maintaining low intracellular calcium levels?
A. Voltage- and ligand-gated calcium channels
B. Calmodulin
C. IP3 receptors
D. Plasma membrane and endoplasmic reticulum calcium pumps
E. Phospholipase C


Show answer

Correct Answer: D


111. The correct temporal sequence for events at the neuromuscular junction is:
A. Action potential in the motor nerve, depolarization of the muscle end plate, uptake of Ca2+ into the presynaptic terminal
B. Uptake of Ca2+ into the presynaptic terminal, release of acetylcholine (ACh); depolarization of the muscle end plate
C. Release of ACh, action potential in the motor nerve, action potential in the muscle
D. Uptake of Ca2+ into the motor end plate, action potential in the motor end plate, action potential in the muscle
E. Release of ACh, action potential in the muscle end plate, action potential in the muscle


Show answer

Correct Answer: B


112. An inhibitory postsynaptic potential:
A. Depolarizes the postsynaptic membrane by opening Na+ channels
B. Depolarizes the postsynaptic membrane by opening K+ channels
C. Hyperpolarizes the postsynaptic membrane by opening Ca2+ channels
D. Hyperpolarizes the postsynaptic membrane by opening Cl- channels


Show answer

Correct Answer: D


113. Chemical synapses:
A. Are activated by depolarization of the post-synaptic neuron
B. Require a presynaptic action potential and calcium influx for transmitter release
C. Require sodium-dependent transporters for transmitter release
D. Are always axoaxonal
E. Are never axoaxonal


Show answer

Correct Answer: B


114. Post-synaptic potentials:
A. Are either excitatory or inhibitory
B. May be either fast or slow
C. May result from either ionotropic or metabotropic receptor activation
D. Must propogate to the axon hillock before an action potential is initiated.
E. All of the above are correct statements


Show answer

Correct Answer: E


115. Metabotropic receptors may increase the magnitude of a post-synaptic potential by:
A. Reducing presynaptic calcium influx
B. Increasing presynaptic potassium influx
C. Modulating postsynaptic ionotropic receptor activity
D. Shifting the Na+ equilibrium potential


Show answer

Correct Answer: C


116. A neuron receives synaptic input at 2 locations, a dendritic knob located 100 micrometers and at the soma located 5 micrometers from the axon hillock. Which of the following statements best describes the postsynaptic potential (PSP) recorded near the axon hillock?
A. The sum of the 2 inputs will always be larger than either one alone
B. The sum of the 2 inputs will always be smaller than either one alone
C. If PSPs from both location initially have the same magnitude the one initiated at the dendritic knob will be larger when recorded near the axon hillock
D. An inhibitory PSP at the soma will attenuate an excitatory PSP initiated in the dendrite


Show answer

Correct Answer: D


117. Periodic hyperkalemic paralysis is characterized by high potassium concentration and muscle weakness. Which of the following is likely to cause muscle weakness as a result of increased extracellular potassium concentration?
A. Hyperpolarization of muscle cells
B. Inactivation of sodium channels in muscle cells
C. Increased release of neurotransmitters form motoneurons
D. Decreased potassium conductance in muscle cells
E. Increased duration of action potentials produced by motoneurons


Show answer

Correct Answer: B


118. Choose one correct answer.
A. The resting membrane potential of most body cells is positive inside and negative outside.
B. If the resting membrane potential is made mode negative it is called hyopolarizartion.
C. If membrane potential moves in the positive direction it is called depolarization.
D. If you put both the measuring electrode (eg, microelectrode) and reference inside of a cell, you will measure a negative voltage.


Show answer

Correct Answer: C


119. Choose one correct answer.
A. Phase 0 of a cardiac action potential is the rapid repolarization phase of the action potential.
B. Phase 1 of a cardiac action potential is the upstroke of a cardiac action potential.
C. During phase 4 of a cardiac action corresponds to the plateau phase of the action potential.
D. None are correct.


Show answer

Correct Answer: D


120. Choose one correct answer.
A. If efflux of an ion exceeds influx, the ion will accumulate in the cell.
B. The flux of an ion across a cell membrane is equal to the product of membrane conductance to the ion and the driving forces acting on the ion.
C. Normally, the only driving force acting on ions is the membrane potential.
D. None arte correct.


Show answer

Correct Answer: B


121. If the resting membrane potential is –100mV and the sodium equilibrium potential is +40mV then what is the value of the electrochemical gradient (ie, total driving force) acting on sodium ions? Choose one correct answer.
A. +60 mV
B. –60 mV
C. –140 mV
D. None are correct.


Show answer

Correct Answer: C


122. Choose one correct answer.
A. The lipid bilayer portion of the cell membrane acts like a resistor.
B. If the membrane conductance to an ion is very high and the total electrochemical gradient is zero there will be no net movement of the ion through the membrane.
C. If the concentration gradient of an ion across the membrane is inwardly directed and the electrical gradient is equal and opposite, there will be net movement of the ion into the cell.
D. None are correct.


Show answer

Correct Answer: B


123. Choose one correct answer.
A. An increase in plasma potassium concentration will cause resting membrane potential to become more negative.
B. Cardioplegia solutions contain a low concentration of potassium.
C. The upstroke of the nerve action potential is generated by Na influx via the Na-K pump.
D. Action potentials repolarize because the net ionic current is outward.


Show answer

Correct Answer: D


124. Choose one correct answer.
A. A reduction in sodium current will increase action potential conduction velocity in nerve.
B. An increase in cell diameter will increase action potential conduction velocity in nerve.
C. An increase in membrane capacitance will increase conduction velocity in heart cells.
D. None are correct.


Show answer

Correct Answer: B


125. Choose one correct answer.
A. Skeletal muscle cells are electrically connected via gap junctions.
B. Local circuit currents are not required for action potential propagation.
C. An increase in action potential amplitude will decrease conduction velocity.
D. None are correct.


Show answer

Correct Answer: D


126. Choose one correct answer.
A. The refractory period of nerve, heart and skeletal muscle is due to inactivation of sodium channels.
B. The space constant is an index of how far local circuit currents can spread in nerve, heart and skeletal muscle.
C. Closure of gap junctions will increase conduction velocity in heart.
D. None are correct.


Show answer

Correct Answer: A


127. Choose one correct answer.
A. Heart muscle cells receive motor neuron innervation.
B. Heart cells are held together at the intercalated disk.
C. Transverse tubules directly connect the interstitial fluid to the cytoplasm of the cell.
D. None are correct.


Show answer

Correct Answer: B


128. Choose one correct answer.
A. The A-band lengthens during relaxation.
B. The I-band shortens during contraction.
C. The A-band shortens during contraction
D. None are correct.


Show answer

Correct Answer: B


129. Choose one correct answer.
A. Gap junctions are part of the intercalated disk.
B. The A-band is composed of actin filaments.
C. Action potentials cannot propagate into the t-tubules of muscle.
D. None are correct.


Show answer

Correct Answer: A


130. Choose one correct answer.
A. Skeletal muscle contracts because the intracellular calcium goes up inside transverse tubules.
B. Blockade of SR Ca release channels will increase the magnitude of the calcium transient in heart muscle.
C. Epinephrine will decrease the strength of contraction in heart muscle.
D. None are correct.


Show answer

Correct Answer: D


131. Choose one correct answer.
A. Cardiac muscle requires beat-to-beat Ca influx to trigger contraction.
B. A DHP blocker will increase the strength of contraction in heart muscle.
C. SR Ca release channels are called DHP receptors.
D. None are correct.


Show answer

Correct Answer: A


132. Choose one correct answer.
A. Digitalis decreases the strength of contraction of heart muscle.
B. Na-Ca exchange requires ATP directly and normally acts to pump Ca into heart cells.
C. Blockade of SR Ca pumps will increase the rate of relaxation of heart and skeletal muscle.
D. None are correct.


Show answer

Correct Answer: D


133. Choose one correct answer.
A. Calcium binds directly to myosin to promote crossbridge formation.
B. In a resting heart muscle cell, tropomyosin acts to shield the myosin binding sites on actin.
C. Binding of ATP to actin acts to detach myosin from actin.
D. None are correct.


Show answer

Correct Answer: B


134. Choose one correct answer.
A. During an isometric contraction the tension goes up and the muscle shortens.
B. Heart muscle cells can normally develop tetanic contractions.
C. Skeletal muscle cells are normally held at a muscle length that maximizes their ability to generate force.
D. None are correct.


Show answer

Correct Answer: C


135. Choose one correct answer.
A. Skeletal muscle fibers that rely mainly on oxidative phosphorylation for ATP production have few capillaries.
B. Recruitment of muscle fibers is a major mechanism for varying the strength of cardiac muscle.
C. Creatine kinase catalyzes the phosphorylation of creatine phosphate.
D. None are correct.


Show answer

Correct Answer: C


136. Choose one correct answer.
A. Inositol triphosphate (IP3) inhibits SR Ca release in smooth muscle.
B. The calcium–calmodulin complex in smooth muscle inhibits myosin-light chain kinase.
C. Smooth muscle can develop both tonic and phasic contractions.
D. None are correct


Show answer

Correct Answer: C