Lecture 3: Action Potential

Question 1

Common structures of neutrons:
1. Input zone: _____
2. Integration zone: _____
3. Point of action potential initiation: ____
4. Conducting zone: ____
5. Out put zone: _____

Answer 1

Dendrite
Cell body
Axon hillock
Axon
Axon terminal

Question 2

An electrical signal that travels from one end of a cell to the other very rapidly

Answer 2

Action potential

Question 3

___ allow fast information transfer within the body
________ mediate the rapid spread of information

Answer 3

Neurons
Action potential

Question 4

Voltage different across plasma membrane =

Answer 4

Membrane potential

Question 5

-50 to -70mV =

Answer 5

Resting membrane potential

Question 6

The magnitude of the potential depends on the degree of separation of _____ ____

Answer 6

Opposite charges

Question 7

Less potential = ___
More potential = ___

Answer 7

Depolarized
Hyperpolarized

Question 8

Lipid bilayer is a good ___

Answer 8

Insulator

Question 9

Electrical signals in neurons depend on rapid changes in ____

Answer 9

Membrane potentials

Question 10

____ mediate the flow of ions (currents) that underlie electrical signals in excitable cells

Answer 10

Ion channels

Question 11

Structure of ion channels:
___ span the membrane
Form ___ -filled pore

Answer 11

Proteins
Water

Question 12

Properties of ion Chanels:
-act as filters allowing specific ___ through the cell membrane
- have ___ states and _____ states
- transition between states = gating
- > channels gate in response to:
-changes in _______ (____ - gated channels)
- ______ binding (____-gated or ___ operated channels)
- ____ forces (______ channels)

Answer 12

Ions
Conducting and non conducting
Gating
Membrane potential (voltage gated)
Ligand (ligand or receptor )
Mechanical (mechanosensitive )

Question 13

Structure: Functional role:
___ and ___ Synaptic potential intrinsic excitability
—— Action potential generation
___ action potential conductance
________ Transmitter release

Answer 13

Dendrites and cell body
Axon hillock
Axon
Axon terminal

Question 14

Rapid opening of voltage gated channel triggered at ___

Answer 14

Threshold

Question 15

Na+ channels:
___ activating and inactivating
Inactivated channels cannot ____

K+ channels:
___ activating
Persistent ___

At rest Na+ and K+ channels are ___

Answer 15

Fast
Reopen
Slow
Activation
Closed

Question 16

A triggered event induces membrane ___
Depolarization may activate some___ channels allowing __ influx
Causing more _____

Answer 16

Depolarization
Na+
Depolarization

Question 17

___ = start of action potential (point of no return)

Answer 17

Threshold

Question 18

Once the threshold is reached, _____ feedback cycle of ___ channel
activation begins.
• This cannot be stopped (thus
point of no return)
• This underlies _____
nature of action potentials

Answer 18

Positive
Na+
All-or-none

Question 19

Around the peak of action potential, two things happen that stop further____ and start____

Answer 19

depolarization
repolarization

Question 20

___ channels cannot open while in an inactive state. Therefore action potential cannot be elicited during this time

Answer 20

Na+

Question 21

• Membrane
____ causes
both Na+ and K+
channels to return to
closed state
• Na+ and K+ channels
are available to___ at
next stimulation

Answer 21

Repolarization

Open

Question 22

During afterhyperpolarization (AHP), it is harder to elicit an action potential because the membrane is more ____

Answer 22

hyperpolarized

Question 23

Strong triggering stimulus
results in ___ frequency firing

Answer 23

High

Question 24

How do neurons fire action potentials in different patterns?

Answer 24

Neurons have various ion channels that can induce various firing patterns

Question 25

Action potential starts at the ____ and then propagate down the ___ • While propagating, action potentials do no wane in _____ • This is because action potential is ____

Answer 25

Axon hillock Axon Size Regenerative

Question 26

What are the Two functional roles of refractory period

Answer 26

1. Prevent backward propagation of action potentials 2. Limit firing frequency

Question 27

What ion channels underlie action potentials?

Answer 27

Na+ and K+ channels

Question 28

Where is action potential generated?

Answer 28

Axon hillock

Question 29

Why can an action potential travel long distance without fail?

Answer 29

Because action potentials are regenerative

Question 30

Why does an action potential propagate in one direction along the axon?

Answer 30

Refractory period prevents backpropagation of action potential

Question 31

Since action potentials are all-or-none, how are differences in the signal intensity conveyed?

Answer 31

Firing frequency and pattern of action potentials

Question 32

Conduction velocity is defined by: - ____diameter - density of ___ channels - myelin ____ -distance between _____

Answer 32

Axon Na+ Insulation Nodes of ranvier

Question 33

__________ means that action potentials jump from one node of ranvier to the next thus propagating much faster

Answer 33

Saltatory conduction

Question 34

Action potentials jumping from one node of ranvier to the next is due to ________

Answer 34

Myelination of the axon

Question 35

Nodes of ranvier are bare part of the ____ that support action potential conduction

Answer 35

Axon

Question 36

Glial cells provide ___

Answer 36

Myelin

Question 37

___ is cellular process of glial cells

Answer 37

Myelin

Question 38

Myelin is consisted of tightly wrapped cell __

Answer 38

Membrane

Question 39

Lipid bilayer does not pass ___

Answer 39

Ions

Question 40

___ is mostly cell membrane = good insulation

Answer 40

Myelin

Question 41

Electrical current propagates faster and farther along the _____ axon

Answer 41

Myelinated

Question 42

Myelin does/does not conduct current ?

Answer 42

Not

Question 43

Myelin is/is not part of the axon ?

Answer 43

Not

Question 44

__ axons conduct faster

Answer 44

Thicker

Question 45

__ nerve fibers: - Proprioception - contraction of skeletal muscle

Answer 45

Aα

Question 46

___ nerve fibers -touch

Answer 46

A(beta)

Question 47

___nerve fibers -acute pain

Answer 47

Aδ

Question 48

____ nerve fibers - chronic or dull pain - temperature -itch

Answer 48

C

Question 49

Heavily _____ axons conduct faster

Answer 49

Myelinated

Question 50

What factors determine the action potential velocity?

Answer 50

– Axon diameter, myelination, Na+ channel density

Question 51

What is the role of nodes of Ranvier?

Answer 51

– Regeneration and propagation of action potential

Question 52

What type of cells provide myelin?

Answer 52

– CNS: oligodendrocytes, PNS: Schwann cells

Question 53

Action potential: Intensity of signal is conveyed by ___

Answer 53

Frequency

Question 54

Action potential: ______ in one direction – Initiated at ____ (highest density of Na channels) – _____ channel distributed along the axon supports action potential propagation (action potential is regenerated by Na channels) – _______ prevents action potential from going backwards

Answer 54

Propagates Axon hillock Na+ Refractory period

Question 55

Conduction velocity (speed of propagation ) depends on: – ____ –_____

Answer 55

Axon diameter Myelination