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Shared characteristics of simple and facilitated diffusion of glucose

Both types occur down an electrochemical gradient


During upstoke of the nerve action potential

There is net inward current and the cell interior becomes less negative

  • Te inward current is carried by sodium
  • movement of positive charge into the cell


Solution A and B are separated by a semipermeable membrane that is permeable to K but not to Cl. Solution A is 100 mM KCL and solution B is 1 mM KCL. what will happen?

K will diffuse from solution A to solution B until a membrane potential evelops with solution A negative with respect to solution B


The correct temporal sequence for events a the neuromuscular junction is

Uptake of ca into the presynaptic terminal; release of ACh; deoplarization of the muscle end plate


Characteristic component shared by skeletal and smooth muscle

Elevation of intracellular calcium for excitation-contraction coupling


Repeated stimulation of a skeletal muscle fiber fauses a sustained contraction. Accumulation of which solute in intracellular fluid is responsible for tetanus



Soluions A and B are separated by a membrane that is permeable to calcium and impermeable to Cl. Solution A contains 10 mM CaCl2 ans solution B contains 1 mM CaCl2. Assuming that 2.3 RT/F = 60mV, Ca will be at electrochemical equilibrium when

solution A is -30mV


A 42 y/o man with myasthenia gravis notes increased muscle strength when he is treated with AChE inhibitor. The basis for his improvement is increased

levels of ACh at the muscle end plate


In a hospital error, a 60 year old woman is infused with large volumes of a solution that causes lysis of her RBC. The solution was most likely

300mM urea

  • 150mM NaCL and 300mM mannitol are isotonic
  • 350mM mannitol and 150mM CaCl2 are hypertonic
  • 300 MM urea is hypotonicc


During a nerve action potential, a tmulus is deliered as indicated by the attow shown in the following figure. In response to the stimulus, a second action potential _____

will not occur

  • because the stimulus was delivered during the absolute refractory portion


Solution A and B are separated by a membrane that is permeable to urea. Solution A is 10MM urea, and soluton B is 5 mM urea. if the concentration of urea in solution A is doubled, the flux of urea across the membrane wall will


  • Flux is proportional to the concentration dfference across the membrane


A muscle cell has an intracellular [Na] od 14 mM and extracellular [Na] of 140 mM. Assuming that 2.3 RT/F = 60 mV, what would the membrane potential be if the muscle cell membrane were permeable to Na?


  • Nernst equation
  • ENa = 2.3RT/zF Log Ce/Ci = 60 mV log 140/14  =60


at which labeled poiny on the action potential is K+ closest to electochemical equilibrium?


  • the hyperpolarizing afterpotential represents the period durimg K permeability is the highest and the membrane potential is clsoest to the K equilibrium potential


What process is responsible for the change in membrane potential that occurs between poin1 and point 3

Movement of na into the cell


What process is responsible for the change in membrane potential that occurs between point 3 and point 4


Movement of K out of the cell


The velocity of conduction of action potential along a nere will be increased by

myelinating the nerve


Solutions A and B are separated by a semipermeable membrane. Solution A contains 1 mM sucrose and 1mM urea. Solution B contains 1 mM sucrose. the reflection coefficient for urea is zero. for sucrose is one. What will happen

Solution A is hyperosmotic with respect to solution B, and the solutions are isotonic



transport of D and L glucose proceeds at the same rate down the elctrochemical gradient by which of the following processes

facilitate diffusion


how can we double permeability of a solute in a lipid bilayer

doubling the oil/water partition coefficient of the solute


A newly developed local anesthetic blocks sodium channels in nerves. Which of the following effects on the action potential would it be expected to produce?

Decrease the rate of rise of the upstroke of the action potential


At the muscle end plate, ACh causes opening of the

Na and K channels and depolarization to a value halfway between sodium and K equilibrium potentials


An inhibitory postsynaptic potential

hyperpolarizes the postynaptic membrane by opening Cl channels


Which of the followinf would occur as a result of the inhibition of Na, K, ATPase?

increased intracellular calcium concentration



Temporal sequence for excitation-contraction coupling in skeletal muscle?

Action potential in the muscle membrane; depolarization of the T tubules; release of calcium  from the SR


Which of the following transport processes is involved if transport of glucose from the intestinal lumen into a small intestinal cell is inhibited by abolishing the usual Na gradient across the cell membrane?



In skeletal muscle, which of the following events occurs before depolarization of the T tubules in the mechanism of excitation contraction coupling?


Depolarization of the sarcolemma membrane


Which of the following is an inhibitory neurotransmitter in the CNS



ATP is used indirectly for which of the following processes

Absorption of glucose by intestinal epithelial cells


Causes rigor in the skeletal muscle?

A decrease in ATP level


Degeneration of dopaminergic neurons has been implicated in ____

Parkinson disease