Lecture 03 Membrane Potentials & Action Potentials Flashcards Preview

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Flashcards in Lecture 03 Membrane Potentials & Action Potentials Deck (43):

Which of the type of neuron would transmit an action potential the fastest?

Large Diameter and myelinated


Saltatory conduction is characteristic of which part of a typical neruon?



Selectivity Filter with carbonyl oxygen is associated with what ion channel



Restin potential for a typical neuron, like motor neuron is represented by how many mV?



Q image thumb

A image thumb

What is a cell body of a neuron?

Houses the nucleus and oter typical cell organelles. Has local potentials and voltage-gated ion channels are NOT characteristic of the cell body membrane


How does the cell body differ from the axon?

conducts a different type of potential


Define Dendrites

Cellular extensions of the neuron. Have ligand gated ion channels. Local potentials


Define axons

Extension of the cell body. Covered by the plasma membrane. Voltage - gated ion channels for action potentials. Membrane bound vesicles with neurotransmitters


What is an axolemma

Plasma membrane that coveres the axon


What causes a diffusion potential?

Caused by an ion concentration difference on either side of a membrane


Define Nerst potential

The Nernst potential is the diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through a membrane. How much energy is needed to keep an ion from diffusing across a membrane


How does one measure membrane potential?

Electrode outside the cell membrane in the extracellular fluid. Micropipette electrode is placed inside the cell. Inside the cell at rest is negative. Reference from inside the cell 


What represents an electrical dipole layer?

The distribution of ions immediately on either side of the membrane is mostly positive or mostly negative. A voltage change area


The ions immediately on either side of a membrane is mostly positive or mostly negative is what type of distribution?

Dichotomous distribution


Describe the graph


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A: Recording electrode is in the extracellular fluid

B: Recording electrode pierces cell membrane

C: recording electrde pierces other side of membrane and is in the extracellular fluid again


The Nernst equation can measure the potential for how many ions?

Only one ion at a time


What equation is used to measure the potential for more than one ion at a time?

Goldman's equation


What are the three assumptions that must be made when using the Nernst equation?

1. Only be used for one ion at at time

2. Membrane must be completely permeable to that ion

3. Ion must be at equilibrium



Define the following equation

E = 2.3 RT/F log Co/Ci


E = Nernst potential

R = Universal gas constant

T = Absolute temperature

F = Faraday's constant

Ci = Concentration of ions inside the membrane

C= Concentration of ions outside the membrane


What is the Nernst equation equal to EMF

EMF = Eion = z(61.5) x log ([ion]outside/[ion]inside


What are the characteristics of action potential

Its all-or-none.

Self-propagating = Each region of depolarization serves to generate action potentials on either side

 Non-decremental: does not decrease in strength


What is local potential

Conducted at the dentrites and the cell body. Potential that involves ligan gated channel. It can become less negative or more negative. Can be an inhibitory or excititory potential. Very quickly phases out. If you can keep it strong enough until it gets to axon hillock it can generate an axon potential


What do ligand gated channels require?

Attachment of a chemical messenger such as a neurotransmitter to a receptor


What is the molecular structure of a voltage - gated sodium channel

4 domains in a cylindrical configuration. Each domain has 6 hydrophobic transmembrane segments. S4 has a high positive charge. Inactivation gate associated with intracellular hydrophilic linkage between domains 3 and 4


Voltage-gated sodium channels have how many gates?

2 gates. Activation gate and inactivation gate


Describe the activation steps in voltage-gated sodium channels

1. Resting potential: Activation gate is closed and the inactivation gate is opened at -90mV 

2. Depolarization: Activation gate opens asa voltage reaches -7-mV to -50mV

3. Repolarization: Activation gate is opened and the inactivation gate is cosed at +35mV to -90mV


Describe the K+ gate

K+ has one gate

1. Gate is closed at resting potential of -90mV

2. Slow activation opens the gate from +35 to -90mV



What are the steps in the generation of an action potential on a neuron axon memebrane?

1. Resting Stage -90mV

2. Deplarization state-Membrane suddenly becomes permeale to sodium ions, membrane potentail may overshoot fr large axons

3. Replarization stage - Sodium channels close, K+ channels open more than normal.


What is hyperpoloraization

When repolarization exceeds -90


What propagates the increased speed at which the action potential travels?

Increase of diameter=larger cross-sectional area to internal flow of current

Wrapping axon with layers of insulation (myelin sheeths)



How does myelin sheath create a capacitor effect?

Capacitor consists of two conducting plates sparated by an insulating barrier.

Intracellular and extracellular fluids = plates

Lipid membrane layer = insulating barrier


What is capacitor's capacitance?

Directly proportional to the area of the plates - bigger plates can store more charge

Inversely proportional to the distance separating the plates


How do myelinatd axons increase the speed of conduction?

Current flows at points of least resistance, therefore potential flow jumps from one node to the next greatly increasing the speed.


What is the jumping from node to node referred to as?

saltatory conduction


What is the threshold point at which a local potential will elicit an action potential



What is the direction of propagation?

Action potential travels in all idrections from the point of stimulation


What are the two directions of propagation?

Orthodromic direction: Towards distal end of axon

Antidromic direction: Towards the axon hillock/neuron cell body


Why do action potential typically travel in the orthodromic direction?

We always start the action potential on the axon hillock in our nervous system. In a lab situation we could have it go either way


What is sphingomyelin

Principle lipid found in myelin sheath


What are schwann cells?

Cells that form the myelin sheaths in peripheral axons


What is absolute refractory period?

Period during which a second action potential cannot be elicitd even with a strong stimulus. And energy is derived directly from breakdown of ATP


What is relative refractory period

Stronger than normal stimulus can cause action potential