Lecture 5- Membrane Potential

Question 1

Central nervous system (integration)

Answer 1

brain and spinal cord

Question 2

Peripheral nervous systems

Answer 2

sensory input and motor output

Question 3

sensory receptor send the _____ to the brain for integration

Answer 3

Sensory input

Question 4

motor output send the signal to the ____ from the brain and spinal cord after integration

Answer 4

effector

Question 5

_____ receive, process and transmit information to other cells

-Functional Units of Nervous System

Answer 5

neurons

Question 6

• the cell body
  -contains genetic information, maintains the neuron’s structure, and provides energy to drive activities

Answer 6

soma

Question 7

-receive input from many other neurons and carry those signals to the cell body.

-

Answer 7

dendrites

Question 8

_____ (nerve fibers) – conduct signals away from the cell

• carry information for long distances with high fidelity and without loss

Answer 8

Axon

Question 9

classification of neurons

Answer 9

1. sensory or afferent neurons
2. motor or efferent neurons
3. interneuron

Question 10

Action potential

Answer 10

Nerve impulses

Question 11

AP is carried from the ______ (near axon hillock) to the axon terminal – skeletal muscle cell or gland

Answer 11

spike-initiating zone

Question 12

Electrical potential difference across the cell membrane caused by different concentrations of ___, ____, and ___on each side of the membrane.

Answer 12

K+, Nat, and Cl ions

Question 13

• 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

Answer 13

Membrane Potential (Vm )

Question 14

• source of potential energy to move molecules across membranes
  -excitable cells use changes in _____ as
  communication signals
  -critical for allowing the coordinated movements of
  cells and organisms

Answer 14

membrane potential

Question 15

a ______ is a localized electrical gradient across membrane

Answer 15

membrane potential

Question 16

________ are more concentrated within a cell

Answer 16

anions (negative)

Question 17

_____ are more concentrated in the extracellular
fluid

Answer 17

cations (positive)

Question 18

an unstimulated cell usually has a resting potential of _________

Answer 18

-70mV

Question 19

As the K+ ions diffuse out of the cell, the impermeable anions are left behind, creating a ________

Answer 19

membrane potential

Question 20

*Excess negative charge inside – draw _______ into the cell

Answer 20

positive charges

Question 21

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

Answer 21

equilibrium potential (Eion )

Question 22

__________ Is the principal intracellular cation

Answer 22

K+

Question 23

____ is the principal extracellular cation

Answer 23

Na+

Question 24

____, ____, ____, ___ are the principal intracellular anions

Answer 24

proteins, amino acids, sulfate, and phosphate

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

at resting potential the concentration of K+ is greater inside
the cell, while the concentration of Na+ is greater outside the
cell - ________

Answer 26

chemical potential energy

Question 27

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

Answer 27

Sodium-potassium pumps

Question 28

Sodium-potassium pumps use the energy of ATP to maintain
these __ and ___ across the plasma membrane

Answer 28

K+ and Na+ gradients

Question 29

Opening of ______ in the plasma membrane converts chemical potential to electrical potential

Answer 29

ion channels

Question 30

Opening of ion channels in the plasma membrane converts
chemical potential to _____

Answer 30

electrical potential

Question 31

A neuron at resting potential contains many open ___ and ___; K+ diffuses out of the
cell

Answer 31

K+ channels and fewer open Na+ channels

Question 32

_____ trapped inside the cell contribute to the negative
charge within the neuron

Answer 32

Anions

Question 33

• allow ions to
  diffuse across the plasma membrane
  – these channels are always open

Answer 33

Non-gated ion channels

Question 34

____ can generate large changes in their
membrane potential

Answer 34

excitable cells

Question 35

• open or close in response to stimuli

Answer 35

gated ion channels

Question 36

• opening or closing of ion channels alters the membrane‘s
  permeability to particular ions, which in turn alters the _____

Answer 36

membrane potential

Question 37

types of gated-ions

Answer 37

1. chemically-gated ion channels (ligand-gated ion channels)
2. voltage-gated ion channels

Question 38

_____ open or close in response to a
chemical stimulus

Answer 38

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

Question 39

__________ open or close in
response to a change in membrane potential

Answer 39

voltage-gated ion channels

Question 40

changes in membrane potential of neuron give rise to ____

Answer 40

nerve impulses

Question 41

What are the two graded potential:

Answer 41

1. Hyperpolarization
2. Depolarization

Question 42

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

Answer 42

more negative

Question 43

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

Answer 43

Depolarization

Question 44

An _____ is a rapid sequence of changes in the voltage across a membrane

Answer 44

action potential

Question 45

In the resting state, closed voltage-gated K+ channels open slowly in response to depolarization

Question 46

Voltage-gated Na+ channels have two gates:

Answer 46

1. closed activation gates open rapidly in response to
   depolarization
2. open inactivation gates close slowly in response to depolarization

Question 47

Most voltage-gated Na+ and K+
channels are closed, but some K+
channels (not voltage-gated) are
open

Answer 47

Resting phase

Question 48

Voltage-gated Na+ channels open first
and Na+ flows into the cell

Answer 48

Depolarization

Question 49

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

Answer 49

Rising phase

Question 50

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

Answer 50

falling phase

Question 51

during falling phase, voltage-gated
Na+ channels become _____;
voltage-gated K+ channels open, and K+ flows out of the cell

Answer 51

inactivated

Question 52

During the ______, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close; resting potential is restored

Answer 52

undershoot

Question 53

The _______ is a result of a temporary inactivation of the Na+ channels.

Answer 53

refractory period

Question 54

nerve impulses
propagate themselves
along an ____

Answer 54

axon

Question 55

the _____ is
repeatedly regenerated
along the length of the
axon

Answer 55

action potential

Question 56

An action potential is generated as
sodium ions flow ____ across the
membrane at one location

Answer 56

inward

Question 57

An _____ is generated as
sodium ions flow inward across the
membrane at one location

Answer 57

action potential

Question 58

the membrane is
____ as K+ flows outward

Answer 58

repolarizing

Question 59

• in myelinated neurons only unmyelinated regions of the axon
  depolarize

Answer 59

Saltatory conduction

Question 60

Depolarized region

Answer 60

Node of Ranvier

Question 61

– in myelinated neurons only unmyelinated regions of the axon
depolarize

_ thus, the impulse moves faster than in unmyelinated neurons

Answer 61

Saltatory conduction

Question 62

in myelinated neurons only unmyelinated regions of the axon
____

Answer 62

depolarize

Question 63

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

Answer 63

electrical synapses

Question 64

In electrical synapses, action potential travels directly from the presynaptic
to the postsynaptic cells via _____

Answer 64

gap junctions

Question 65

A _____ transmits the signal toward a synapse

Answer 65

presynaptic neuron

Question 66

A _____ , transmits the signal away from the synapse

Answer 66

postsynaptic neuron

Question 67

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

Answer 67

synapse

Question 68

Synapse is a region where
neurons nearly touch and
where nerve impulse is
______

Answer 68

transferred

Question 69

a small gap between neurons is called?

Answer 69

synaptic cleft

Question 70

Transmission across a
synapse is carried out by
______

Answer 70

neurotransmitter

Question 71

Transmission oy synapse result in a ____

Answer 71

Sudden rise in calcium at end
of one neuron

Question 72

Stimulates synaptic vesicles to
merge with the presynaptic
membrane

Answer 72

Neurotransmitter

Question 73

_____ r molecules
are released into the synaptic
cleft

Answer 73

neurotransmitter

Question 74

Primary Factors Influencing Impulse Transmission

Answer 74

1. Axon diameter (typically around 1 micrometer)
2. Myelination - formation of the myelin sheath around a nerve
3. Temperature - the lower the temperature, the slower the impulses move.

Question 75

– increase the transmembrane resistance and
decrease the effective neuronal membrane capacitance

Answer 75

Myelination

Question 76

As the number of membrane layers wrapped around the axon

Answer 76

Resistance increase

Question 77

If the myelin layer is thick

Answer 77

Capacitance decrease

Question 78

Action potentials traveling down the axon “jump” from node to node.

Answer 78

Saltatory conduction