Unit 4: Electrical phenomena in the biological system - Practice Quiz

1 The electrical potential difference that exists across the membrane of a resting cell is called the:

2 The inside of a resting excitable cell is electrically ___ relative to the outside.

3 The typical resting membrane potential of a neuron is approximately:

4 Which of the following is an example of an electrically excitable cell?

5 Excitable cells are defined by their ability to:

6 Besides neurons, which cell type is classically considered electrically excitable?

7 A rapid, transient reversal of membrane potential in a neuron is called a(n):

8 The rising phase of a neuronal action potential is mainly due to the influx of which ion?

9 The process in which the membrane potential becomes less negative is called:

10 The return of the membrane potential toward its resting value after depolarization is called:

11 According to the all-or-none principle, an action potential fires only when the stimulus reaches the:

12 The brief period after an action potential during which a new one cannot be initiated is the:

13 The ionic hypothesis proposes that membrane potentials arise from the movement of:

14 The equilibrium potential for a single ion can be calculated using the:

15 In a resting neuron, the concentration of is higher:

16 The pump that maintains ionic gradients by moving out and into the cell is the:

17 The equilibrium potential of an ion depends primarily on its:

18 Proteins that allow ions to pass through the cell membrane are called:

19 Membrane proteins that open or close in response to changes in voltage are called:

20 Which type of membrane protein uses energy to move ions against their concentration gradient?

21 A neuron has an intracellular concentration of and an extracellular concentration of at . Using the Nernst equation , what is the approximate equilibrium potential for ?

22 During the rising phase (depolarization) of an action potential in a nerve cell, the membrane potential moves toward which value?

23 Which statement best explains why action potentials are described as 'all-or-none' events?

24 The -ATPase pump maintains ionic gradients across the neuronal membrane. For each ATP hydrolyzed, it transports:

25 According to the ionic hypothesis of Hodgkin and Huxley, the resting membrane potential is closest to rather than mainly because:

26 Which of the following cell types is NOT classified as electrically excitable?

27 Which factor most increases the conduction velocity of an action potential along an axon?

28 During the absolute refractory period of a neuron, a second action potential cannot be generated because:

29 A voltage-gated channel differs from a ligand-gated channel primarily in that it opens in response to:

30 The Goldman-Hodgkin-Katz (GHK) equation improves on the Nernst equation for calculating membrane potential because it:

31 A graded potential differs from an action potential in that a graded potential:

32 If the extracellular concentration is experimentally raised, the resting membrane potential of a neuron will:

33 Aquaporins are membrane proteins that primarily facilitate the transport of:

34 In cardiac pacemaker cells, the slow spontaneous depolarization toward threshold (the 'funny current') is carried mainly by:

35 If a nerve cell's membrane became equally permeable to and , its membrane potential would settle:

36 The after-hyperpolarization (undershoot) that follows an action potential is caused by:

37 Coding of a very strong sensory stimulus in a single sensory neuron is achieved mainly by:

38 The selectivity filter of a voltage-gated channel allows to pass while excluding the smaller ion because:

39 In skeletal muscle fibers, the action potential triggers contraction by causing release primarily from the:

40 According to the ionic rules governing membrane potential, an ion is in electrochemical equilibrium when:

41 A neuron has intracellular mM and extracellular mM at . Using the Nernst equation, the equilibrium potential for is approximately closest to which value?

42 Applying the Goldman-Hodgkin-Katz equation, if the membrane permeability to suddenly increases to greatly exceed that of and , the resting membrane potential will:

43 During the falling (repolarization) phase of an action potential, the membrane briefly hyperpolarizes below the resting potential. This afterhyperpolarization is BEST explained by:

44 Two axons differ only in diameter, axon B being 4 times the diameter of axon A. Assuming conduction velocity in unmyelinated fibers scales with , the velocity of axon B relative to A is approximately:

45 The absolute refractory period of an excitable membrane is primarily attributable to which molecular state?

46 The ATPase is electrogenic because it:

47 A cell is permeable to both ( mV) and ( mV). If , the resting potential predicted by the chord conductance equation is approximately:

48 Tetraethylammonium (TEA) applied intracellularly to a squid axon during voltage clamp would primarily:

49 In saltatory conduction, the action potential 'jumps' between nodes of Ranvier. The primary biophysical advantage provided by the myelin sheath is:

50 A subthreshold depolarizing current pulse produces a passive membrane response that decays exponentially. The membrane time constant is defined as:

51 Voltage-gated channels contain a positively charged S4 transmembrane segment. Its principal functional role is to:

52 Hodgkin and Huxley's voltage-clamp experiments distinguished and currents mainly by:

53 Cardiac ventricular myocytes exhibit a prolonged plateau phase absent in neuronal action potentials. This plateau results primarily from:

54 Spatial summation at a neuron's axon hillock depends on the length (space) constant . A dendrite with higher internal (axial) resistance will show:

55 The 'all-or-none' law of action potentials implies that once threshold is reached, increasing stimulus strength further will:

56 Ligand-gated ion channels (ionotropic receptors) differ from voltage-gated channels chiefly in that they:

57 The Donnan equilibrium arises when impermeant intracellular anions (e.g., proteins) are present. A key consequence for a cell that cannot pump is:

58 In a voltage-clamp step depolarization, the current is transient (rises then falls) while the current is sustained. The transient nature of is due to:

59 A demyelinating disease reduces internodal membrane resistance and increases capacitance. The most likely functional consequence is:

60 The relative refractory period differs from the absolute refractory period because during it: