Practice Questions - Week 3

Question 1

Which of the following is primarily responsible for the repolarising phase of the action potential?

Group of answer choices

flow of potassium ions into the cell

flow of sodium ions into the cell

flow of potassium ions out of the cell

the sodium/potassium exchange pump

flow of sodium ions out of the cell

Answer 1

the sodium/potassium exchange pump

Question 2

The membrane potential of a typical excitable tissue cell at rest is usually around?

Answer 2

-80mV

Question 3

Which of the following is/are features of excitable tissue cells at rest?

1. a concentration gradient that favours the movement of Na+ into the cell
2. an electrical gradient that attracts Na+ into the cell
3. voltage-gated Na+ channels that are programmed to close when the membrane potential reaches threshold

Answer 3

1 & 2 only

Question 4

Which of the following are classified as monovalent anions?

calcium ions

sodium ions

potassium ions

chloride ions

none of these are monovalent anions

Answer 4

chloride ions

Question 5

When the membrane potential of an excitable cell decreases in magnitude from the resting membrane potential (i.e. the inside of the cell becomes less negative) we refer to this type of movement as?

Answer 5

depolarisation

Question 6

Excitable tissues relay information about the size of a stimulus using which of the following variables:

1. the amplitude of action potentials
2. the number of action potentials per unit time
3. the duration of action potentials

Answer 6

2 only

Question 7

Which of the following is/are features of voltage-gated ion channels?

    1. a gate whose opening is regulated by the membrane potential

    2. a molecular sensor that measures the membrane potential

    3. membrane spanning proteins that act as conduits for ions

Answer 7

1, 2, & 3

Question 8

The hyperpolarising phase of the action potential is caused by?

Answer 8

an excess of open potassium channels and potassium efflux from the cell

Question 9

Which one of the following statements about action potentials is TRUE?

Group of answer choices

action potentials can arise from hyperpolarising graded potentials

action potentials can travel along axons at speeds of up to 130 Km.sec-1

action potential amplitude is directly proportional to excitatory stimulus strength

in most cells action potentials are over in a few milliseconds

action potentials only affect parts of cells adjacent to the excitatory stimulus

Answer 9

in most cells action potentials are over in a few milliseconds

Question 10

Which of the following statements about ion concentrations and excitable tissues is FALSE?

the concentration of Na+ is higher in the extracellular fluid than the intracellular fluid

the concentration of Cl- is higher in the extracellular fluid than the intracellular fluid

the concentration of Ca2+ is lower in the intracellular fluid than the extracellular fluid

the concentration of K+ is higher in the extracellular fluid than the intracellular fluid

the concentration of Na+ is lower in the intracellular fluid than the extracellular fluid

Answer 10

the concentration of K+ is higher in the extracellular fluid than the intracellular fluid

Question 11

The ion channels that are fundamentally responsible for the magnitude of the resting membrane potential are known as?

Answer 11

Transmembrane ion channels regulate when ions can move in or out of the cell, so that a precise signal is generated. This signal is the action potential which has a very characteristic shape based on voltage changes across the membrane in a given time period.