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Things to know about plasma membranes.
Barrier made of lipids (hydrophobic and hydrophilic regions). Fluidic. Selective in letting things through. Lipids and proteins. Ion gradient maintained across membrane na+/k+. Myelin acts as an insulator. Phospholipids are amphilic.
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Neurons communicate using electricity carried by?
Ions moving across plasma membranes
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Salts dissociate into ions in water which is essential for?
Electrophysiology
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This acts as a barrier to ions.
Lipid bilayer
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Are transmembrane proteins that selectively allow ions to diffuse across membranes.
Ion channels
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Ionic flows is the same as?
Electrical current
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Current depends on ionic flow, which depends on
Conductance
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The relationship between ion flow (current an conductance is described by Ohm?s law
I=g.V
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G=
Conductance Siemens or mho
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V=
Voltage electrophysiology driving force
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V=IR
The more physics version of Ohms law
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Electrical signals in biological systems use ions instead of electrons to?
Carry current
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Ions can pass across membranes only through specialized?
Transmembrane proteins
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Electrical signals in biological systems still follow ohms law-conductance is equivilant to the amount of open?
Ion channels present
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The na/k ATPase uses the energy of ATP hydrolysis to?
Set up NA and K gradients across the membrane.
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All cells have a membrane potential of?
-65mV
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This allows theK+ to equilibrate across the plasma membrane in all cells
K+ leak channel
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This equation calculates the equilibrium potential for a single ion species.
The Nernst equation
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What is the Nernst equation?
Ex = RT/zF ln (X)out / (X)in
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In gK = 0 and gCl = 0, what are the equilibrium potentials EK and ECl?
Use the Nernst equation to find. -80 and 80
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If gK =0 and gCl =0, what is the membrane potential for the cell?
0 No conductance = No movement
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If gK > 0 and gCl = 0 , what is the membrane potential for the cell?
-80mV
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If gK > 0 and gCl >0, what is the membrane potential for the cell?
0
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Equilibrium potential =
Membrane potential
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Increasing extra cellular K+ but not Na+ can ________ the membrane potential.
Depolarize
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These cells carry out spatial buffering of K+
Glial Cells called astrocytes
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The occurs when thee is conductance for one ion but not its counter-ion.
Nernst equilibrium
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A tiny amount of ionic movement is sufficient to establish a
Nernst equilibrium
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A typical resting potential is mostly established by K+ leak channel conductance, but some _____ conductance also contribute.
Na+
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Which Ion has the most important role in deciding the resting potential of a neuron?
K+
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Action [potentials occur only on?
Axons
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Specialized extensions of neurons. (Stick out)
Neuritis
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Receive information from other neurons. Contains only some organelles(mitochondria, cytoskeleton)
Dendrites
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Sends information to the other neurons.
Axons
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The cell body of a neuron
Some
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This is where the axon joins soma
Axon Hillock
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Injecting current into the cell needs to be greater than what in order to stimulate a action potential?
-40mV
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Action potentials are
All-or-none
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Describes the potential for and direction of ionic movement
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If Vx is + then?
Movement is out
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If Vx is ? then?
Movement is inward
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Inward Na+ current during the rising phase of an action potential is carried by?
Voltage-gated Na+ channels
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Voltage-gated channels are only express on?
Axon membranes
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Ion channels activity can be monitored using?
Single channel patch clamp recording
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Membrane repolarization during the falling phase of an action potential uses?
Delayed-rectifying K+ channels
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Action potentials are propagating wave of membrane depolarization from the soma t the?
Axon terminal
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Is a measure that allows one to tell weather an ion will move at any given time, and in which direction
Driving force
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Most properties of the action potential can be explained by
Voltage-gated Na+channels and delayed rectifying K+ channels
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Channel properties can be measured using
- Single channel patch clamp recordings
- Which ion is more important for membrane depolarization during action potential?
- Na+
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Which ion is more important for membrane repolarization during action potential
K+
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A smaller T will
Increase membrane potential and will depolarize faster
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A larger lambda will?
Give you a longer decay
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If the goal was to have membranes tat could passively depolarize faster and father how would you change the parametersT and Lambda?
Make T smaller and Lambda larger
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Resistance is inversely proportional to?
Area
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Capacitance is proportional to?
Area
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Capacitance in inversely proportional to?
Thickness
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Oligodendrocytes and other glial cells form _______ that insulate axons
Myelin Sheathes
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Facilitate salutary conductance
Slatatory jumping
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Membranes have passive electrical behaviors called
Cable properties
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The time constant t=RmxCm. T doesn?t not change significantly with
Axon size
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The length constant l =(Rm/Ri)1/2. I increases with
Axon diameter
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Myelinating increases I without substantially changing
t.
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