5 Membrane Potential

Question 1

receive, process, and transmit information to other cells.

Answer 1

Neurons

Question 2

What are the three (3) main parts/functional units of a neuron?

Answer 2

• Soma (metabolic maintenance)
• dendrites (receive signals)
• axons or nerve fibers (transmit signals)

Question 3

A part/functional unit of a neuron that is responsible for the metabolic maintenance of the neuron.

Answer 3

Soma

Question 4

A part/functional unit of a neuron that acts as the receptive surface, bringing signals from other neurons toward the cell body.

Answer 4

Dendrites

Question 5

What are the three (3) types of neurons?

Answer 5

• Sensory (afferent)
• motor (efferent)
• interneurons.

Question 6

A type/functional unit of a neuron that conducts signals away from the cell body and carries information for long distances with high fidelity and without loss.

Answer 6

Axon

Question 7

Where are the motor-neuron dendrites and soma innervated?

Answer 7

On the surface membrane

Question 8

What initiates an action potential (nerve impulse) in a neuron?

Answer 8

Soma

Question 9

Where is the action potential carried from in a neuron?

Answer 9

from the spike-initiating zone near the axon hillock to the axon terminal.

Question 10

Where does the action potential travel to in motor neurons?

Answer 10

skeletal muscle cells or glands.

Question 11

• It is the electrical potential difference across the cell membrane.
• difference in electric potential between the interior and the exterior of a biological cell.
• the result of an excess of negative charges on one side of the plasma membrane and positive charges on the other side.
• a source of potential energy to move molecules across membranes.

Answer 11

Membrane potential (Vm)

Question 12

What causes the membrane potential in a neuron?

Answer 12

different concentrations of K+, Na+, and Cl- ions on each side of the cell membrane.

Question 13

What is the typical range of membrane potential in neurons?

Answer 13

between -60 mV and -80 mV

Question 14

It is a source of potential energy to move molecules across membranes.

Answer 14

membrane potential

Question 15

Does every cell have a membrane potential (or voltage)?

Answer 15

Yes

Question 16

It is a localized electrical gradient, with anions concentrated inside the cell and cations concentrated in the extracellular fluid.

Answer 16

membrane potential

Question 17

What are the two factors that influence potential difference? (2)

Answer 17

• concentration gradient for an ion
• membrane’s permeability to that ion.

Question 18

How is membrane potential measured?

Answer 18

microelectrode connected to a reference electrode via a voltmeter.

Question 19

What is the typical resting potential of an unstimulated cell?

Answer 19

Approximately -70mV.

Question 20

In which direction does K+ move?

Answer 20

K+ moves outward.

Question 21

In which direction does Na+ move?

Answer 21

Na+ moves inward.

Question 22

Does Cl- have a gradient for movement?

Answer 22

No, Cl- has no gradient for movement.

Question 23

It means there are equal numbers of anions and cations.

Answer 23

Electroneutral

Question 24

What balances the outward concentration gradient?

Answer 24

The inward electrical gradient.

Question 25

What happens when potassium ions move out of the cell?

Answer 25

- more negative inside the cell - more positive outside the cell

Question 26

What is the effect of excess negative charge inside the cell?

Answer 26

It draws positive charges into the cell.

Question 27

What happens as more potassium leaves the cell?

Answer 27

The electrical force increases until it balances the driving force from the potassium concentration gradient.

Question 28

The membrane potential at which the electrical force and concentration gradient for a specific ion balance each other.

Answer 28

Equilibrium potential (Eion)

Question 29

How many ions can move across the membrane to achieve equilibrium?

Answer 29

Eion (equilibrium potential) = Vm (membrane potential) - Only a single ion can move across the membrane.

Question 30

It calculates the potentials of two different elements and then calculate the difference between these elements to predict the potential across a cell.

Answer 30

Nernst equation

Question 31

It calculates the membrane potential considering the permeability and concentration of all relevant ions.

Answer 31

Goldman-Hodgkin-Katz equation

Question 32

What is the principal intracellular cation?

Answer 32

K+ (Potassium)

Question 33

What is the principal extracellular cation?

Answer 33

Na+ (Sodium)

Question 34

What are the principal intracellular anions? (4)

Answer 34

- Proteins - amino acids - sulfate - phosphate

Question 35

What is the principal extracellular anion?

Answer 35

Cl– (Chloride ion)

Question 36

At resting potential, where is the concentration of K+ greater? Where is the concentration of Na+ greater?

Answer 36

* Concentration of K+ is greater inside the cell * Concentration of Na+ is greater outside the cell

Question 37

What do sodium-potassium pumps use to maintain K+ and Na+ gradients?

Answer 37

energy of ATP

Question 38

What does the opening of ion channels in the plasma membrane convert?

Answer 38

Chemical potential to electrical potential

Question 39

What type of channels are more open at resting potential in a neuron?

Answer 39

K+ channels

Question 40

What happens to K+ at resting potential in a neuron?

Answer 40

K+ diffuses out of the cell

Question 41

What contributes to the negative charge within a neuron at resting potential?

Answer 41

Anions trapped inside the cell

Question 42

A gate that allows ions to diffuse across the plasma membrane; they are always open.

Answer 42

non-gated ion channels

Question 43

How do excitable cells generate large changes in their membrane potential?

Answer 43

By opening or closing gated ion channels in response to stimuli.

Question 44

What happens when ion channels open or close?

Answer 44

The membrane's permeability to particular ions changes, altering the membrane potential.

Question 45

What are the two (2) types of gated ions?

Answer 45

* Chemically-gated ion channel * Voltage-gated ion channel

Question 46

An ion channel that opens or closes in response to a chemical stimulus (ligand-gated).

Answer 46

chemically-gated ion channel

Question 47

An ion channel that opens or closes in response to a change in membrane potential.

Answer 47

voltage-gated ion channel

Question 48

What do changes in membrane potential of a neuron give rise to?

Answer 48

Nerve impulses.

Question 49

Changes in membrane potential where the magnitude of change varies with the strength of the stimulus.

Answer 49

Graded Potential

Question 50

What are the two (2) types of Graded Potential?

Answer 50

* Hyperpolarization * Depolarization

Question 51

What type of graded potential? Gated K+ channels open, K+ diffuses out of the cell, and the membrane potential becomes more negative.

Answer 51

hyperpolarization

Question 52

What type of graded potential? Gated Na+ channels open, Na+ diffuses into the cell, and the membrane potential becomes less negative.

Answer 52

Depolarization

Question 53

* It is an "all or nothing" response triggered when the threshold potential is reached. * Depolarization that results in graded potentials summing to approximately -55mV, achieving the threshold potential.

Answer 53

Action potential

Question 54

What are the two (2) voltage-gated Na+ channels? (What is their function)

Answer 54

* **closed activation gates** open rapidly in response to depolarization * **open inactivation gates** close slowly in response to depolarization

Question 55

What is this period? * A temporary inactivation of the Na+ channels. * After an action potential, a second action potential cannot be initiated.

Answer 55

Refractory period