Lesson 2: The Neuronal Membrane Flashcards
What separates the inside and outside of the neuron?
Phospholipid Bilayer
The heads of the phospholipid bilayer are:
Hydrophilic phosphate heads
The tails of the phospholipid bilayer are:
Hydrophobic hydrocarbon tails
True or False:
The phospholipid bilayer is not permeable to ions and small molecules
False, the phospholipid bilayer is permeable to ions and small molecules
What spans the phospholipid bilayer to regulate the entrance/exit of molecules?
Proteins
What are some integral and peripheral membrane proteins associated with the cell membrane? (3)
Lipid-anchor protein
Peripheral membrane protein
Integral membrane protein
Cell membrane establishes _____________ _________ for different ____
Concentration gradients
Ions
What ion has high concentrations outside of the cell?
Sodium
What ion has high concentrations inside of the cell?
Potassium
What ion has small amounts altogether but higher amounts outside the cell?
Chloride
All ion channels are what?
Integral membrane proteins
Ion channels contains a ____ which allows ions to flow through the membrane
Pore
True or False:
A variety of stimuli activate specific types of ion channels
True
How are voltage gated ion channels activated?
Activated by changes in the electrical membrane potential near the channel
What ion channels are activated by changes in the electrical membrane potential near the channel?
Voltage Gated Ion Channels
_______ _____ _____ create “_______ ______” domain
Charged amino acids
Voltage sensor
The amino acids at the pore of ion channels act as what?
Selectivity filter
How do ions move? (3)
Diffusion
Electrical forces
Sodium potassium pump
How do ions move under diffusion?
Diffusion pushes ions down their chemical gradient
How do ions move under electrical forces?
Electrical forces cause like charges to repel and opposite charges to attract
How do ions move under the sodium potassium pump?
The sodium potassium pump establishes an ionic concentration gradient
Define:
Membrane potential
A quantification of the difference in net charge and ion concentrations across the cell membrane
Opening of voltage gated ion channels lead to an _____ or ______ of ions that is regulated by _______________ forces
Influx
Efflux
Electrochemical
What do we use to the calculate the equilibrium potential for a single ion?
Nernst Equation
State:
Nernst equation
E
(RT/zF)
ln(ion outside cell/ion inside cell)
What does the R stand for in the Nernst Equation?
The universal gas constant
What does the T stand for in the Nernst Equation?
Temperature of the environment in Kelvin
What does the Z stand for in the Nernst Equation?
The charge of the ion
What does the F stand for in the Nernst Equation?
Faraday’s constant
Define:
Conductance
The ease with which an ion flows across the membrane
What letter represents conductance?
P
What do we use to calculate the equilibrium potential when the membrane is permeable to multiple ions?
Goldman Equation
Describe:
Goldman Equation
Combines the Nernst potential for each ion, weighting by conductance
State:
Goldman Equation
58 log ( (p[K+]+p[Na+]+p[Cl-]) / (p[K+]+p[Na+]+p[Cl-]) )
Define:
Threshold
Voltage needed to generate action potential
Define:
Depolarization
Rapid shift in electric charge, resulting in less negative charge inside the cell
Define:
Overshoot
Membrane potential is positive
Define:
Repolarization
Restoration of charge following depolarization
Define:
Hyperpolarization
Membrane potential is more negative than rest
During Resting Phase:
Voltage gated ___ and __ channels are ______
Na+
K+
Closed
During Resting Phase:
_____ and ____ ________ maintain the larger concentration of __ in the neuron and greater concentration of ___ outside
Pumps
Leak channels
K+
Na+
Is there a higher of concentration of K+ inside or outside the neuron during resting phase?
Inside, there is a higher concentration of Na+ outside the neuron
What is the threshold?
-55 mV
During Initial Depolarization:
membrane potential arrives at _________ (____)
Threshold
-55 mV
During Initial Depolarization:
___ voltage-gated channels open causing an influx of ___
Na+
Na+
What type of channels open causing an influx of Na+ during initial depolarization?
Voltage-gated channels
What happens during initial depolarization?
Rapid depolarization
True or False:
During initial depolarization, potassium channels activate but take 1 s to open
False, potassium channels activate but take 1 ms to open
In initial depolarization, at what charge does potassium channels open?
-50 mV
During Depolarization:
Most gated ___ channels are open
Na+
True or False:
During depolarization, voltage continues to rise
True
During Depolarization:
Opening of sodium channels is a ________ ________ ____ (___ continues to open as voltage rises)
Positive Feedback Loop
More
During Repolarization:
At ____, ___ gated channel inactivates
+30 mV
Na+
During Repolarization:
_________ _____ ________ are open now, creates an outflow of __
Potassium gated channels are open now
K+
During Repolarization:
Membrane potential begins to _____, approaching _______ value
Lower
Resting
During Hyperpolarization:
Membrane potential goes _____ rest since ______ channels are still inactivated
Below
Sodium
During Hyperpolarization:
Approaches equilibrium potential for _________ and the channels for it __________
Potassium
Inactivate
True or False:
Voltage returns to rest in hyperpolarization
True
How long does sodium channel inactivation last for?
1 ms
What is the sodium channel inactivation known as?
Absolute refractory period
What does the absolute refractory period do? (2)
Prevents the generation of another action potential
Leads to unidirectional propagation down the axon
How do we speed up action potential propagation? (3)
Axon diameter and conduction speed
Myelination
Saltatory Conduction
Action potential propagation speed is increased by __________ the diameter of axons
Increasing
The glia insulate axons with a lipid-rich ______ ______
Myelin sheath
In the PNS, what insulates axons with myelin?
Schwann Cells
In the CNS, what insulates axons with myelin?
Oligodendrocytes
How does myelination increase conduction velocity?
Fewer ions diffuse out of axon, more ions diffuse through axon
What are breaks in the myelin sheath called?
Nodes of Ranvier
Where are voltage-gated ion channels limited to in myelinated axons?
Nodes of Ranvier
What is saltatory conduction?
The “boosting” of the action potential signal at the nodes
How does saltatory conduction help speed up action potential propagation?
Prevents dissipation of the signal, creates node-to-node jumping
Information flows down dendrites and axons, allows for ______________ information flow
Unidirectional
Dendrites are _________ and receive thousands of synaptic contacts, integrate ____ _______ ______
Distinct inputs
What in axons allows information to travel long distances through the nervous system?
Length of axon
Define:
Patch Clamp
Intracellular recording that relies on attaching a pipette to the outer membrane of a single cell through suction and recording the activity
Define:
Two Electrode Voltage Clamp (TEVC)
A patch-clamp electrophysiology method for injecting current into a cell with one electrode and recording the change in voltage with the other electrode
Define:
Single Electrode Patch Clamp
Record from an individual cell by using one electrode to record activity
