membrane potential

Question 1

receive, process and transmit
information to other cells

Answer 1

Neurons

Question 2

metabolic maintenance

Answer 2

Soma

Question 3

receptive surface
that brings signals from other
neurons toward the cell body

Answer 3

Dendrites

Question 4

• Nerve Fibers
• conduct
  signals away from the cell
• carry information for long
  distances with high fidelity
  and without loss

Answer 4

Axons

Question 5

Afferent neuron

Answer 5

sensory

Question 6

efferent nueron

Answer 6

motor

Question 7

surface membrane of motor-neuron
dendrites & soma

Answer 7

innervated

Question 8

Soma integrates input to initiate…

Answer 8

Action potential (AP)

Question 9

Action Potential

Answer 9

nerve impulse

Question 10

AP is carried from the…

Answer 10

spike-initiating zone

Question 11

• fundamental property of cells resulting from an
  excess of negative charges on side of the plasma
  membrane and an excess of positive charges on the
  other side
• source of potential energy to move molecules across
  membranes
• excitable cells use changes in membrane potential as communication signals
• critical for allowing the coordinated movements of cells and organisms

Answer 11

Membrane potential

Question 12

every cell has a ______ or ________ across
its plasma membranes

Answer 12

Voltage, membrane potential

Question 13

localized electrical gradient
across membrane

Answer 13

Membrane potential

Question 14

• negative
• are more concentrated within a cell

Answer 14

Anions

Question 15

• positive
• are more concentrated in the extracellular
  fluid

Answer 15

Cations

Question 16

microelectrode connected to a reference electrode via a
voltmeter (voltage drop across the circuit)

Answer 16

Measures membrane potential

Question 17

an unstimulated cell usually has a resting potential of ….

Answer 17

-70mV

Question 18

equal numbers of anion and cations

Answer 18

Electroneutral

Question 19

Excess negative charge inside

Answer 19

draw positive charges into the
cell

Question 20

more potassium leaves the cell

Answer 20

the electrical force
increases to a level that balances the driving force from the
potassium concentration gradient

Question 21

potassium ions continue to
move, inward and outward fluxes exactly balance each other

Answer 21

equilibrium potential

Question 22

represents the sum of the equilibrium potentials of all
the relevant ions

Answer 22

Goldman-Hodgkin-Katz equation

Question 23

• K+ the principal intracellular cation
• Na+ is the principal extracellular cation

Answer 23

Cations

Question 24

• proteins, amino acids, sulfate, and phosphate are the
principal intracellular anions
• Cl– is principal extracellular anion

Answer 24

Anions

Question 25

the concentration of K+ is greater inside the cell, while the concentration of Na+ is greater outside the cell

Answer 25

at resting potential

Question 26

use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane

Answer 26

Sodium-potassium pumps

Question 27

opening of ion channels in the plasma membrane

Answer 27

converts chemical potential to electrical potential

Question 28

contains many open K+ channels and fewer open Na+ channels; K+ diffuses out of the cell

Answer 28

neuron at resting potential

Question 29

Anions trapped inside the cell

Answer 29

ell contribute to the negative charge within the neuron

Question 30

- always open - allow ions to diffuse across the plasma membrane

Answer 30

Non-gated ion channels

Question 31

- can generate large changes in their membrane potential - gated ion channels - alters the membrane‘s permeability to particular ions, which in turn alters the membrane potential

Answer 31

Excitable cells

Question 32

open or close in response to a chemical stimulus

Answer 32

chemically-gated ion channels (ligand-gated ion channels)

Question 33

open or close in response to a change in membrane potential

Answer 33

voltage-gated ion channels

Question 34

changes in membrane potential of neuron give rise to

Answer 34

nerve impulse

Question 35

- are changes in membrane potential - magnitude of the change in membrane potential varies with the strength of the stimulus

Answer 35

graded potentials

Question 36

Gated K+ channels open --> K+ diffuses out of the cell ---> the membrane potential becomes more negative

Answer 36

Hyperpolarization

Question 37

Gated Na+ channels open --> Na+ diffuses into the cell --> the membrane potential becomes less negative

Answer 37

Depolarization

Question 38

All or Nothing Depolarization

Answer 38

Action Potential

Question 39

if graded potentials sum to »-55mV a ______ is achieved

Answer 39

Threshold potential

Question 40

triggers an action potential

Answer 40

Threshold potential

Question 41

@ gates of Votage-gated Na+

Answer 41

closed activation open inactivation

Question 42

open rapidly in response to depolarization

Answer 42

closed activation

Question 43

gates close slowly in response to depolarization

Answer 43

open inactivation

Question 44

During the _______, the threshold is crossed, and the membrane potential increases

Answer 44

rising phase

Question 45

During the _______, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell

Answer 45

Falling phase

Question 46

During the _________, membrane permeability to K+ is at first higher than at rest, then voltagegated K+ channels close; resting potential is restored

Answer 46

undershoot

Question 47

During the ___________ after an action potential, a second action potential cannot be initiated.

Answer 47

refractory period

Question 48

a result of a temporary inactivation of the Na+ channels.

Answer 48

refractory period

Question 49

– in myelinated neurons only unmyelinated regions of the axon depolarize • thus, the impulse moves faster than in unmyelinated neurons

Answer 49

Saltatory conduction

Question 50

action potential travels directly from the presynaptic to the postsynaptic cells via gap junctions

Answer 50

Electrical Synapses

Question 51

- more common than electrical synapses - postsynaptic chemically-gated channels exist for ions such as Na+, K+, and Cl- - depending on which gates open the postsynaptic neuron can depolarize or hyperpolarize

Answer 51

Chemical Synapses

Question 52

a region where neurons nearly touch and where nerve impulse is transferred

Answer 52

Synapse

Question 53

Small gap between neurons

Answer 53

Synaptic cleft

Question 54

Transmission across a synapse is carried out by

Answer 54

Neurotransmitters

Question 55

Primary Factors Influencing Impulse Transmission

Answer 55

Axon diameter Myelination Temperature

Question 56

typically around 1 micrometer

Answer 56

Axon diameter

Question 57

formation of the myelin sheath around a nerve

Answer 57

Myelination

Question 58

the lower the temperature, the slower the impulses move.

Answer 58

Temperature

Question 59

velocity of impulse propagation varies as a function of

Answer 59

axon diameter and myelination

Question 60

increase the transmembrane resistance and decrease the effective neuronal membrane capacitance

Answer 60

Myelination

Question 61

the number of membrane layers wrapped around the axon

Answer 61

Resistance increases (cytoplasm and extracellular fluid)

Question 62

myelin layer in very thich

Answer 62

Capacitance decreases

Question 63

- in myelinated neurons only – unmyelinated regions of the axon depolarize - thus, the impulse moves faster than in unmyelinated neurons

Answer 63

Saltatory conduction