Electrical Properties of Nerve Cells Part 1

Question 1

What causes receptor potential?

Answer 1

Due to the activation of
sensory neurons by external stimuli

Question 2

How do neurons respond to external stimuli (receptor potential)?

Answer 2

These neurons respond to the external stimuli (ex: touch) with a receptor
potential that changes the resting potential for a fraction of a second

Question 3

What is synpatic potenital reocrded throuhg?

Answer 3

Synpatic contacts

Question 4

When does an action potential occur?

Answer 4

Occurs when a neuron sends information down an axon, away from the cell body

Question 5

Action Potential Function

Answer 5

Responsible for long range transmission of information within the nervous system and allow the nervous system to transmit information
to its target organs, such as muscle

Question 6

Effects of current on membrane potential?

Answer 6

injection of small amounts of current result in small shifts of membrane potential

Question 7

Effects of stopping current injection on membrane potential

Answer 7

When current injection stops, the membrane potential recovers to the resting potential

Question 8

Hyperpolarized

Answer 8

A change in a cell’s membrane potential that makes it more negative

Question 9

Depolarization

Answer 9

Change in cell’s membrane potential that makes it more positive

Question 10

Graded Potential

Answer 10

A change in the electrical potential on the membrane of an nerve cell in response to a stimulus, and where the magnitude of change is proportional to the strength of the stimulus

Question 11

Electrochemical Equilbrium

Answer 11

when the movement of ions down their electrical gradient is equal and opposite in direction to the movement of ions down their concentration (chemical) gradient.

Question 12

Equilibrium Potential

Answer 12

Refers to the membrane potential at which there is no net movement of an ion across the plasma membrane into or out of the cell

Question 13

Three types of neuronal signals

Answer 13

1)Receptor potential
2) synaptic potential
3) Action potential

Question 14

Steps of Action Potential

Answer 14

1) Rest: Leaky K+ channel and Na+/K+ pump are in action.
2) Rising Phase: Initial depolarization brings to threshold. Once reached, voltage gated Na+ channels open.
3) Falling Phase: K+ voltage gated channels open and Na+ channels inactivate.
4) Undershoot (Refractory): K+ voltage channels remain open, Na+ still inactivated.
5) “Return to rest”: Both voltage gated channels begin to close.

Question 15

Synaptic Potential

Answer 15

The electrical signal associated with communication between neurons at synaptic contacts.

Question 16

Action Potential

Answer 16

Responsible for long-range transmission of information within the nervous system or to target organs

Question 17

Passive electrical responses:

Answer 17

Does not require a unique property of the neuron

Question 18

Active electrical response:

Answer 18

Action potentials and requiring a fundamental change in how proteins will respond

Question 19

What is the difference in electric potential between the interior and the exterior of a biological cell?

Answer 19

Membrane potential, measured in mv

Question 20

The amplitude of the action potential is INDEPENDENT of the magnitude of the current used to evoke it. What is this principle?

Answer 20

all-or-none response,

Question 21

What property is DEPENDENT on the magnitude of the current?

Answer 21

frequency of action potentials

Question 22

If a current-passing electrode produces a current that yields a(n) ______ change in membrane potential as shown in Fig. C, then the magnitude of the resulting potential change will ______ with increasing distance from the site of current injection (B). This is known as ______ conduction.

Answer 22

subthreshold, decay, passive

Question 23

If a current-passing electrode produces a current that yields a(n) ______ change in membrane potential as shown in Fig. C, then the magnitude of the resulting potential change will remain ______ with increasing distance from the site of current injection (B). This is known as ______ conduction.

Answer 23

suprathreshold, constant, active

Question 24

Why does passive conduction decay over time? How can this be prevented?

Answer 24

ion dissipation, myelin which helps to speed up action potential conduction by acting as an electrical insulator

Question 25

Active Transporters

Answer 25

Membrane proteins are responsible for actively moving selected ions against their concentration gradient and creating ion concentration gradients?

Question 26

Ion channels

Answer 26

Membrane proteins are selectively permeable to certain ions and allow these ions to move passively down their concentration gradients

Question 27

Both hyperpolarizing and depolarizing electrical stimulation result

Answer 27

Graded Potential

Question 28

Some _______ channels types (non-gated) in the plasma membrane are "leaky" allowing a _______ diffusion of K+ out of the cell

Answer 28

potassium, slow facilitated

Question 29

Why do all cells in the body have a negative-inside resting potential compared to the outside?

Answer 29

1)The membrane of the resting neuron is more permeable to K+ than any other ion so the resting potential is closer to the equilibrium potential 2)more K+ inside than outside due to transporter activity so more cations are leaving than entering the cell

Question 30

Why are squid axons larger than the standard mamallian axon?

Answer 30

Giant neurons evidently evolved in squid because they enhanced the animal’s survival. These neurons helped produce a jet propulsion effect that allows the squid to move away from predators at a remarkably fast speed.

Question 31

Increasing the external K⁺ concentration makes the resting membrane potential more (POSITIVE / NEGATIVE).

Answer 31

POSITIVE since increasing the external K+ concentration causes depolarization

Question 32

What did Hodkin and Katz find about Na+ concentration and rate or rise of action potential?

Answer 32

External Na+ concentration reduces both the rate of rise of the action potential and its peak amplitude

Question 33

Hodgkin and Katz found that lowering the Na⁺ concentration had very little effect on what variable

Answer 33

Resting membrane potential

Question 34

Capacitive Current

Answer 34

The redistribution of charge that occurs across the membrane when the membrane potential is set to a given command voltage

Question 35

The action potential arises from the coordinated activation of two conductance

Answer 35

1) A sodium conductance (transient inward current) that activates rapidly and drives the rising phase of the action potential 2) A a potassium conductance (delayed outward current) that activates more slowly and contributes to the falling phase of the action potential and the undershoot.

Question 36

What happens as the membrane becomes more depolarized?

Answer 36

The inward current decreases and outward current increases

Question 37

Relationship between current and sodium

Answer 37

Removal of external Na⁺ causes this initial inward current to become outward, an effect that is reversed by restoration of external Na⁺. (sodium moved out of the cell)

Question 38

What is the relationship between both peak Na+and K+ conductance and membrane potential?

Answer 38

Both peak Na⁺ conductance and steady-state K⁺ conductance increase as the membrane potential becomes more positive.

Question 39

Refractory Period

Answer 39

Refers to the period of time immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation

Question 40

Feedback cycles

Answer 40

responsible for membrane potential changes during an action potential.

Question 41

Membrane depolarization activates a (POSITIVE / NEGATIVE) feedback cycle fueled by the voltage-dependent activation of Na+ conductance. This phenomenon is followed by the slower activation of a (POSITIVE / NEGATIVE) feedback loop as depolarization activates a K+ conductance, which helps to (DEPOLARIZE / REPOLARIZE) the membrane potential and terminate the action potential.

Answer 41

positive, negative, repolarize

Question 42

Action potential propagation requires the coordinated action of two forms of current flow:

Answer 42

Passive and active currents flowing through voltage dependent ion channels

Question 43

Where are voltage gated sodium and potassium channels located?

Answer 43

Nodes of Ranvier

Question 44

Function of Myelin

Answer 44

Acts as an insulator to close leaky membranes and speed up propagation of relatively slow action potentials.

Question 45

saltatory conduction

Answer 45

Describes the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials

Question 46

Myelin

Answer 46

Insulating layer, or sheath that forms around nerve

Question 47

myelin sheath

Answer 47

allows electrical impulses to transmit quickly and efficiently along the nerve cells

Question 48

What type of cells form myelin sheth and where is myelin formed?

Answer 48

PNS, Schwan cells

Question 49

In the CNS what is myelin formed by?

Answer 49

myelin is formed by oligodendrocytes

Question 50

Difference between schwan and oliogendrocytes

Answer 50

1) Location 2) scwhann cells in the PNS form a 1:1 relationship with an axon and oligodenfrocytes in the CNS can wrap around myelin, making contact with many axons

Question 51

What happens if you lose the ability to form compact myelin?

Answer 51

The nerve/neuron doesn’t send the signal and action potential to the muscle at the right speed, causing muscle degeneration

Question 52

Voltage Clamp

Answer 52

Allows for the macroscopic current of the cell, meaning it measures the current flowing through thousands of voltage gated channels

Question 53

Patch Clamp

Answer 53

Specialized type of voltage clamp method and allows for the microscopic current of the cell, meaning it measures the current flowing through an individual channel.

Question 54

Cell-attached recording

Answer 54

Patch clamp configuration involves applying suction to a membrane, creating a seal between the fine-tipped glass electrode and a single membrane channel?

Question 55

Whole -Cell Recording

Answer 55

Patch clamp configuration involves applying strong suction such that the interior of the pipette becomes continuous with the cell cytoplasm?

Question 56

Outside-out recording?

Answer 56

Patch clamp configuration involves breaking the membrane such that the membrane will come back together with the extracellular domain exposed

Question 57

Inside-out Recording?

Answer 57

Patch clamp configuration involves breaking the membrane such that the cytoplasmic domain is accessible?

Question 58

At a positive membrane potential, the Na⁺ current is (POSITIVE / NEGATIVE) and (INWARD / OUTWARD).

Answer 58

positive, outward (neg potential current is negative nad inward)

Question 59

Does depolarization active/inactive Na and K+

Answer 59

While depolarization activates and then inactivates Na⁺, it does not inactivate K⁺, allowing it to flow outward for the entire depolarization phase.

Question 60

Describe the functional state of voltage-gated Na⁺ and K⁺ channels when the membrane potential is hyperpolarized.

Answer 60

The gates of both channels are closed when the membrane potential is hyperpolarized.

Question 61

Describe the functional state of voltage-gated Na⁺ and K⁺ channels when the membrane potential is depolarized.

Answer 61

When the potential is depolarized, voltage sensors (indicated by +) allow the channel gates to open—first the Na+ channels and then the K+ channels. Na+ channels also inactivate during prolonged depolarization, whereas many types of K+ channels do not

Question 62

Voltage Gated Channels

Answer 62

are selectively permeable to each of the major physiological ions: Na⁺, K⁺, Ca²⁺, and Cl⁻.

Question 63

Ligand gated channels

Answer 63

less selective and allow permeation of two or more types of ions through the channel pore

Question 64

Pore Loop -Voltage gated sodium channels

Answer 64

a filter for certain ions, providing ion selectivity for sodium ions

Question 65

Selectivity Filter

Answer 65

made of negatively charged amino acid residues, which attract the positive Na+ ion and keep out negatively charged ions such as chloride

Question 66

Voltage Sensors

Answer 66

enable movement within the membrane in response to changes in membrane potential.

Question 67

Structure mammalian voltage-gated K⁺ channel when it is hyperpolarized

Answer 67

Closed because the inside of the cell is more negatively charged. These negative charges attract the positively charged voltage sensors, such that the pore is closed

Question 68

Structure mammalian voltage-gated K⁺ channel when it is depolarized

Answer 68

Open (When the membrane is depolarized, the inside of the cell is more positively charged. These positive charges repel the positively charged voltage sensors, such that the pore is open.)

Question 69

Co-transpoters

Answer 69

Type of active transporters do not use ATP directly but instead carry multiple ions in the same direction?

Question 70

Three types of active transporters

Answer 70

1) ATPase pumps 2) Ion Exchangers 3)Co-transporters

Question 71

Ion exchangers

Answer 71

Do not use ATP directly but instead carry one or more ions up its electrochemical gradient while simultaneously taking another ion down its gradient?

Question 72

ATPase Pump

Answer 72

Acquired energy directly from the hydrolysis of ATP (examples depicted in figure)?

Question 73

What two factors does the efflux of radioactive Na⁺ from a squid giant axon depend on?

Answer 73

1) If extracellular K+ is removed, Na+ efflux is reduced 2) If ATP is blocked, the function of this channel is blocked

Question 74

Correctly order the sequence of events for the movement of ions by the Na⁺/K⁺ pump.

Answer 74

1) Na⁺ binding. 2) Phosphorylation. b.) Dephosphorylation-induced conformation changes leads to K⁺ release. d.) Phosphorylation-induced conformation changes leads to Na⁺ release and K⁺

Question 75

Correctly order the sequence of events for the movement of ions by the Ca²⁺ pump starting with Ca²⁺ binding.

Answer 75

1) ATP binding 2)Phosphorylation c.) Ca2+ binding d) Conformational change causes Ca²⁺ release