physics chapter 3 section 2

Question 1

Question

Answer 1

Answer

Question 2

What is a cation?

Answer 2

A cation is a positively charged ion (an atom or group of atoms with more protons than electrons due to losing one or more electrons).

Question 3

What is an anion?

Answer 3

An anion is a negatively charged ion (an atom or group of atoms with more electrons than protons due to gaining one or more electrons).

Question 4

What happens if there is no potential difference?

Answer 4

There is no potential difference if there is no difference in the number of charges on either side.

Question 5

How is potential difference created?

Answer 5

Potential difference (voltage) is created when there is a difference in the number of charges across a boundary.

Question 6

What is the equilibrium potential of an ion?

Answer 6

The equilibrium potential is the transmembrane voltage at which the electric force generated by the ion’s diffusion down its concentration gradient equals the molecular force of that diffusion.

Question 7

Can two ions with the same charge have different equilibrium potentials?

Answer 7

Yes, ions with the same charge can have different equilibrium potentials if their concentrations inside and outside the cell are different.

Question 8

What is the equilibrium potential for potassium (K+) in neurons?

Answer 8

The equilibrium potential for potassium (EK) in neurons is approximately –89 mV (with 5 mmol/L K+ outside and 140 mmol/L inside).

Question 9

What is the equilibrium potential for sodium (Na+) in neurons?

Answer 9

The equilibrium potential for sodium (ENa) in neurons is approximately +46 mV (with 2 mmol/L Na+ inside and 12 mmol/L outside).

Question 10

What equation is used to find the equilibrium potential?

Answer 10

The Nernst equation is used to calculate the equilibrium potential of an ion.

Question 11

Is the membrane potential governed by only one ion?

Answer 11

No, the membrane potential is generally established by the relative contributions of several ions, including K+, Na+, and Cl-.

Question 12

What ions primarily contribute to the membrane potential in cells?

Answer 12

Potassium (K+), sodium (Na+), and chloride (Cl-) ions primarily contribute to the membrane potential in many cells.

Question 13

How is the membrane potential calculated when multiple ion channels are present?

Answer 13

The membrane potential is calculated using the Goldman-Hodgkin-Katz equation when more than one ion channel is present and open.

Question 14

What factors determine the contribution of an ion to the membrane potential?

Answer 14

The contribution of an ion to the membrane potential is determined by its concentration gradient and its relative membrane permeability.

Question 15

What is membrane permeability?

Answer 15

Membrane permeability refers to the ease with which ions cross the membrane and is directly proportional to the number of open channels for a specific ion.

Question 16

What happens when ion channels on the cell membrane open or close?

Answer 16

The opening or closing of ion channels can change the resting membrane potential, causing depolarization (interior becomes more positive) or hyperpolarization (interior becomes more negative).

Question 17

What is depolarization?

Answer 17

Depolarization occurs when the interior voltage of the cell becomes more positive, such as when sodium (Na+) ions flow inside the membrane.

Question 18

What is hyperpolarization?

Answer 18

Hyperpolarization occurs when the interior voltage becomes more negative, such as when the membrane potential changes from –70 mV to –80 mV.

Question 19

What is the resting state of a neuron’s membrane?

Answer 19

The resting state of a neuron’s membrane is polarized, with fewer positive ions inside the cell than outside.

Question 20

What happens during depolarization of a neuron?

Answer 20

During depolarization, a stimulus causes the neuron’s membrane to allow sodium ions to flow inside, making the interior more positively charged.

Question 21

What initiates an action potential in a neuron?

Answer 21

The exchange of ions (particularly sodium influx) initiates an action potential in the neuron.

Question 22

How does an action potential propagate?

Answer 22

An action potential, once started, propagates over the entire axon, with impulses traveling faster along axons with a myelin sheath.

Question 23

What is repolarization in neurons?

Answer 23

Repolarization occurs when potassium (K+) ions rush out of the neuron after sodium (Na+) ions rush in, restoring the membrane to its resting state.