Exam 1

Question 1

What is a “membrane potential”?

Answer 1

a membrane potential is the voltage difference between the inside and outside of a cell.

Question 2

The membrane potential has two basic functions:

Answer 2

1. Allows a cell function a a battery, providing power to operate a variety of “molecular devices” embedded in the membrane
2. In electrically excitable cells such as neurons, it is used for transmitting signals between different parts of a cell.

Question 3

Three types of membrane potentials:

Answer 3

1. Resting membrane potential
2. Action potentials
3. Synaptic potentials

Question 4

Resting potential

Answer 4

this is used to refer to the membrane potential of nerve and muscle cells not actively signaling.

Question 5

Why does the resting potential exist?

Answer 5

Membrane potential result from a separation of positive and negative charges (ions) across the membrane.

Question 6

Nernst Equation

Answer 6

The equilibrium potential for an ion can be calculated using this

Question 7

The Goldman Equation

Answer 7

infers that the membrane potential of an excitable cell is most strongly influenced by the concentration difference of the ion to which the membrane is most permeable since each permeant ion attempts to drive the membrane potential towards it own equilibrium potential.

Question 8

Action potentials play an important role in:

Answer 8

1. Information coding

2. Information transfer

Question 9

What information is encoded by action potentials?

Answer 9

Intensity (strength)
Timing
Quality

Question 10

Where are action potentials generated?

Answer 10

Action potentials are generated at the axon hillock. Once generated, they propagate down the axon away from the cell body and towards the axon terminals.

Question 11

How are action potentials generated?

Answer 11

By the movement of Na+ and K+ ions through voltage-gated ion channels.

Question 12

R(o)

Answer 12

Represents the resistance of the extracellular fluid to ion flow down the length of the axon.

Question 13

R(l)

Answer 13

represents the resistance of the cytoplasm to ion flow down the length of the axon

Question 14

R(m)

Answer 14

represents the resistance to ion flow across the membrane (membrane resistance)

Question 15

C(m)

Answer 15

represents the capacity of the membrane to store charge (membrane capacitance).

Question 16

Increasing axon diameter…

Answer 16

decreases R(l)
Increasing axon diameter increases the conduction velocity of action potentials
Decreasing axon diameter decreases the conduction velocity of action potentials

Question 17

Myelin is formed by…

Answer 17

Schwann cells (peripheral nervous system)
oligodendrocytes (central nervous system)

Question 18

Myelination…

Answer 18

increases Rm and decreases Cm

Question 19

Rm is determined by..

Answer 19

the number of open ion channels in the axonal membrane through which ions can pass
the larger the number of open ion channels the small the Rm

Question 20

A capacitor is…

Answer 20

an electrical component comprised of two conductive plates separated by an insulating material (dielectric).
Capacitors store “charge” via electrostatic interactions.

Question 21

The amount of charge stored in a capacitor depends upon:

Answer 21

1. Surface area of plates (larger area, greater capacitance).
2. Thickness of the dielectric (thicker the dielectric, smaller capacitance.

Question 22

What does the thickness of the lipid bilayer as a result of the myelin sheath do?

Answer 22

This decreases the membrance capacitance Cm, reducing the amount of charge that can be stored across the membrane
More ions are available to move down the length of the axon contributing to rapid depolarization of membrane at the nodes of Ranvier and subsequent action potential formation

Question 23

Synaptic transmission

Answer 23

synaptic potentials represent the transfer of info from one neuron to another at a specialized region called a synapse

Question 24

synaptic potentials are..

Answer 24

changes in the membrane potential of the postsynaptic terminal of a synapse due to activity in a presynaptic neuron
they function to initiate or inhibit action potential formation in the postsynaptic neuron

Question 25

Synaptic transmission can be (1) or (2)

Answer 25

electrical - direct transfer of ionic current via a gap junction
(2) chemical synaptic transmission is mediated by neurotransmitters, substances that are released by the presynaptic cell, diffuse across a gap called the synaptic cleft, and bind to postsynaptic receptors effect a postsynaptic electrical response

Question 26

Synaptic transmission can be (1) or (2)

Answer 26

(1) Excitatory synaptic transmission (excitation) causes depolarization of the postsynaptic neuron
- produces excitatory synaptic potentials (EPSPs)
(2) Inhibitory synaptic transmission (inhibition) causes hyperpolarization of the postsynaptic neuron
- produces inhibitory synaptic potentials (IPSPs)

Question 27

Synaptic transmissions can be (1) or (2)

Answer 27

(1) Ionictropic
a. ) Rapid onset, short term effects
(2) Metabotropic:
a. ) slow onset, long term effects

Question 28

The model for the chemical synpatic transmission is the…

Answer 28

Neuronmuscular junction (NMJ)