Chapter 4 - Excitable Cells

Question 1

Excitable Cells

Answer 1

cells that are able to send and receive electrical signals

Question 2

Electrophysiology

Answer 2

study of excitability

Question 3

Compartmentalization

Answer 3

having different homeostatic set points for a substance in two different regions of body or cell.

Question 4

Gradient =

Answer 4

Gradient = [ion]out - [ion]in

Question 5

Gating Mechanism

Answer 5

stimulus required to open or activate an ion channel

Question 6

Voltage-gated ion channels

Answer 6

gated by changes in the relative distribution of changes in their local environment (senses positive and negative charges)

Question 7

Ligand-gated ion channels

Answer 7

gated by a chemical messenger (a ligand) that binds to the channel on inside/outside of the cell

Question 8

What kind of transport to ions do ion channels allow?

Answer 8

Passive

Question 9

What is flux

Answer 9

flow of an ion between the 2 compartments

Question 10

Which ions are more present INSIDE the cell?

Answer 10

Potassium (K+)

Question 11

Which ions are more present OUTSIDE the cell?

Answer 11

Sodium (Na+), Chloride (Cl-), and Calcium (Ca+)

Question 12

Membrane Potential

Answer 12

difference in charge between the two environments creating a form of potential energy

Question 13

Nernst Equation

Answer 13

Eion = (61.5 mV/z)(log ([ion]out)/([ion]in))

Question 14

Nissl bodies

Answer 14

sites of extensive protein synthesis

Question 15

Anterograde transport

Answer 15

transportation of proteins and other materials from cell body to ends of both dendrites and axons

Question 16

Retrograde Transport

Answer 16

From periphery back to the cell

Question 17

Dendrites are filled with

Answer 17

cytoplasm and ribosomes

Question 18

Dendritic spines

Answer 18

On dendrites and have a wide variety of ligand-gated and voltage-gated ion channels

Question 19

Single axon arises from

Answer 19

axon hillock

Question 20

Beginning of axon is termed:

Answer 20

initial segment/trigger zone (high density of voltage gated Na+ channels)

Question 21

Axonal membrane is:

Answer 21

myelinated

Question 22

Synapses

Answer 22

connections between neurons and target cells and stabilize

Question 23

Three parts of synapse

Answer 23

presynaptic membrane (sends message), postsynaptic membrane (receives message), synaptic cleft (btwn the two; filled w/ interstitial fluid)

Question 24

synaptic potential

Answer 24

a change in membrane potential produced on the post-synaptic membrane. Has ligand-gated ion channels (passive)

Question 25

Graded potential

Answer 25

transient change from resting membrane potential that decreases in intensity over time and distance. Produced in dendrites and soma. Decremental

Question 26

Action potentials

Answer 26

change from resting membrane potential that propagates over the excitable membrane and is maintained at constant intensity over time and distance. Produced in axon.

Question 27

Most synapses are:

Answer 27

axodendritic synapses (formed btwn axon terminal of pre-synaptic cell and the dendrites of a post-synaptic cell)

Question 28

Depolarization

Answer 28

EPSP; membrane potential increases, (+) sodium ions entering cell

Question 29

Repolarization

Answer 29

membrane potential returning to normal level

Question 30

Hyperpolarization

Answer 30

IPSP; membrane potential decreasing, (+) potassium ions leave cell

Question 31

EPSP

Answer 31

excitatory post synaptic potential; a depolarizing synaptic potential

Question 32

IPSP

Answer 32

inhibitory post synaptic potential; repolarizing synaptic potential

Question 33

Temporal Summation

Answer 33

individual channel can be activated repeatedly over a short period of time, to cause greater change in postsynaptic potential.

Question 34

Spatial Summation

Answer 34

Channels that are physically close together can be opened at the same time, to cause greater change in postsynaptic potential.

Question 35

Subthreshold Potentials

Answer 35

synaptic potentials that do not depolarize membrane potential enough to reach threshold

Question 36

Suprathreshold potentials

Answer 36

those that are strong enough to reach threshold

Question 37

What kind of ion channels do axons have

Answer 37

Voltage-gated ions channels

Question 38

Repolarization period is also known as

Answer 38

Relative Refractory Period

Question 39

Inactivation period is also known as

Answer 39

Absolute Refractory Period. Action potential cannot be fired even w/ suprathreshold stimulus. Inactivation gate is open at resting potential.

Question 40

Two major factors influence the speed of action potential propagation:

Answer 40

1. axon diameter (wider = faster)
2. Myelination (increased conduction velocity, schwann cells, oligodendrites, electrical insulator, internodes, nodes of Ranvier)

Question 41

Internodes

Answer 41

myelinated axon segments

Question 42

Nodes of Ranvier

Answer 42

gaps between internodes (action potential is recharged here)

Question 43

Synapses can be either:

Answer 43

electrical or chemical

Question 44

Agonists

Answer 44

chemicals that act like neurotransmitters at postsynaptic cell membrane and stimulate receptor

Question 45

Antagonists

Answer 45

chemicals that block effects of neurotransmitters by inhibiting receptor

Question 46

Neuromodulators

Answer 46

can alter the STRENGTH of signaling between neurons and can also affect cells a long distance away from sites of release.

Question 47

Electrical synapses have:

Answer 47

Gap junctions that allow small molecules and ions to pass easily from cytosol of once cell directly into the cytosol of the next (both directions) cvbh