Membrane Potential + Neurophysiology

Magnitude, direction, net diffusion

In electrochemical equilibrium

When chemical and electrical driving forces are equal (in __) and opposite (in __): __ __ stops

Ligand, mechanical, leak, voltage

Various ion channel types include: __(signal), __ (pressure), __ (always open), __-gated (charge)

Equilibrium potential (Eion)

Electrical potential balancing/opposing the chemical driving force for ion diffusion

Nernst Equation, electrical driving

The __ __ mathematically used to calculate an equilibrium potential for given ion

• Does so by telling magnitude of __ __ force required to counteract concentration gradient

Inside, outside

Potentials are expressed as the charge __ (outside/inside) cell relative to the __

Net driving

__ __ force for ion movement describes the difference between membrane potential (Vm) and ion’s Eion

Membrane potential (Vm), votes

__ __ is the difference in electrical potential inside vs outside the cell

• Determined by relative “__” of all ions permeable thru cell membrane

K+, Na+

According to the Resting Membrane Potential from GHK equation:

At rest, permeability of _ (Na or K) is 30x higher than that of _ (Na or K)

K+, leak, gradient, Na+

Vm = -70 mV resting

due to

(1) permeability to _ (with a lot -- of __ channels)

(2) Na+/K+-ATPase __

(3) some permeability to _

-55

When Vm = __ mV, threshold for opening voltage-gated Na+ channels

+40

When Vm = __ mV, there is an increased permeability to Na+

→ Subsequent action potential

Depolarization

Vm decreases and becomes less negative from rest (closer to 0)

Repolarization

Vm returns to resting membrane potential ~ -65 mV

Hyperpolarization

Vm increases and becomes more negative from rest (further from 0)

Overshoot

Vm is above 0 and cell interior is positively charged

Graded, without

In __ potentials, Vm changes from resting membrane potential __ (with/without) initiating an action potential

• Ex: Hyperpolarization, sub-threshold reach

-70, -55, inactivate, -70

For voltage gated Na+ channels:

Vm = __ : Na channels are closed but available

Vm = __: Na channels activate and open

At the peak of an action potential, Na+ channels __ and remain closed until reaching Vm of __ mV

Absolute, -55 to -70

In the __ refractory period: Another AP cannot be initiated when Na+ channels are open or inactivated gates closed

at __ to __ mV

Relative, -70 to hyper

In the __ refractory period: Na+ channels can open (for AP) with sufficient stimulus, as extra K+ channels are still open

at __ mV to __polarization

Na+, one-way

Closing of __ (ion) channels with inactivation gates allows for __-__ propagation of action potentials

diameter, conduction

A larger nerve __ can lead to faster __ velocity in neurons

Myelination, saltatory

__ allows for lipid insulation and current flows along axon

__ conduction with nodes have abundant voltage-gated ion channels, insulated through myelin to next node

GB, MS, myelin, axons

__ and __ are autoimmune disease that result in the degradation of __ and exposure of underlying __

• Poor insulation of neural signals in these diseases and MSK symptomology

Lidocaine, Na+, pain

__ is a local anesthetic that blocks voltage-gated __ channels in rapid depolarization

• Decrease in action potentials means feeling less/slowed __ signals

Electrical synapses

Contain gap junctions and ions for fast neuronal communication; bidirectional

Chemical synapses

Release neurotransmitters at synaptic cleft for slower neuronal communication; unidirectional

Ca2+, reuptake, enzymatic

Action potentials to the chemical synapse open voltage-gated __ channels that aid in the release of neurotransmitters

Leftover neurotransmitters are then removed from the cleft either by __ or __ degradation

nerve, Ca2+, Acetylcholine, Na+, muscle, Acetylcholinesterase

In the neuromuscular junction

Action potential comes to a __ → __ channels open → __ release and bind to motor end plate receptors → __ entry leads to depolarization of motor end plate → Action potential in the __ → __ degrades acetylcholine into acetate and choline

Muscle fiber, -90, -50

End plate potentials traveling to voltage-gated Na+ channels can trigger action potentials in the __ __, depolarizing from RMP of __ to __

End plate potential (EPP), graded

__ __ __ describes the opening of nicotinic ACh receptors leads to local region of depolarization at motor end plate

• This is a __ potential that spreads and triggers action potentials in adjacent areas of skeletal muscle cell membrane

Botulinum, flaccid

__ toxin blocks release of acetylcholine from motor neuron → stops muscle contraction; leads to __ paralysis

Myasthenia Gravis, flaccid, AchE

__ __ is an autoimmune disease in which the immune system produces antibodies to attack nicotinic ACh receptors on post-synaptic muscle; leads to __ paralysis

• Can be counteracted with __ inhibitors

Excitatory, GABA and glycine

__ neurotransmitters - Acetylcholine, glutamate, norepinephrine, epinephrine, serotonin, dopamine

Inhibitory neurotransmitters __ and __

EPSPs, IPSPs

__ encourage depolarization, while __ encourage hyperpolarization

ESP vs ISP

Temporal Summation

Single presynaptic neuron rapid-firing signals to single postsynaptic neuron synapse (summation)

Spatial Summation

Groups of excitatory signals from multiple neurons to single postsynaptic neuron in rapid succession that sum up to net threshold to fire (summation)

Tetanus, spastic, neuromuscular junction

__ neurotoxin prevents exocytosis of GABA and glycine → __ muscle contractions

• This does NOT act directly on the __ __