Action Potentials- Under Construction Flashcards
Synapse
The site of transmission from the pre-synaptic neuron to post-synaptic neuron. Can be electrical or chemical.
Presynaptic Neurons
The neuron before the synapse/synaptic cleft
Dendrites
Small projects from the cell body of a neuron that receive incoming signals from other neurons and relay them to the cell body.
Postsynaptic Neurons
The neuron after the snapse/synaptic cleft
Soma (Cell Body)
The part of the neuron that contains the nucleus and is the site of metabolic activity. Most NTs are synthesized here.
NT = neurotransmitter
Axon Hillock
Part of the cell body of a neuron that connects to the axon.
Muscurinic receptors
ACh G protien coupled receptprs broadly expressed in the CNS
Nicotinic receptors
ACh receptor found in the CNS and at neuromuscular junctions (open channels allowing flux of Na+, CA2+, and K+)
Temporal summation
a single presynaptic neuron rapid-fires singals to a postsynaptic neuron
Spatial summation
Signals come from multiple presynaptic neurons
Resting membrane potential of large neruon
-90
Voltage at which action potential occurs
-55
Potassiums “buddy” in the cell
phosphate
During depolarization in what configuration are the Na+ channel gates
Activation gate - open
Inactivation gate - open
During repolarization in what configuration are the Na+ channel gates
Activation gate - open
Inactivation gate - closed
During rest in what configuration are the
Na+ channel gates
Activation gate - closed
Inactivation gate - open
during rest and depolarization in what configuration is the
K+ channel gate
closed
during repolarization in what configuration is the
K+ channel gate
open
What causes Vescicles to attach and exocitose neurotransmitters
Calcium
Nernst potential for Cl-
-90mV
Nernst potential for K+
-94mV
Nernst potential for Na+
+61mV
K+ efflux is how many times greater than Na+ influx
20 to 100 x
Goldman Hodgkin Katz
concentration gratient and membrane permeability of Na+, K+, and Cl-
Nernst Potential
the potential level across a membrane that will exactly prevent net diffusion of an ion in either direction
According to the Goldman Hodgkin Katz equation sodium brings the membran potential value to what value
-86mV (leak channels)
Na+K+ATPase pump creates additional electonegativity of how much
-4mV
Membrane potential can change based on what
the size, location, and type of nerve fiber
the Na+K+ATPase pump pushes Na+ against
its concentration gradient and electrical gradient
the Na+K+ATPase pump pushes K+ against
its concentration gradient
the Na+K+ATPase pump exchanges:
3 Na+ out and 2 K+in
Potential energy
can change the state of other objects around it
Intracellular Cations
K+ and Mg++
Intracellular Anions
Phosphate, Protein
Extracellular Cations
Na+ and Ca++
Extracellular Anions
Cl- and HCO3-
Diffusion potential
The difference between the concnetration inside (Ci) and the concentration outside (Co)
What is a volt?
determines how fast the electrons will travel through a circuit
Cell membrane as a capacitor
charges are equal within membrane everywhere except lined up along the inside (-) and outside (+) of cell membrane (this can be switched through the movement of + and - ions)
Period during which another action potential cannot happen
absolute refractory period
Period during which antoher action potentil would be difficult but not impossible to stimulate
relative refractory period
Triad of resons for ionic movment once an AP has been initiated
1: Voltage gated channels
2: leak channels
3: Na+K+ATPase pump
At threshold, the activation gate opens: Na+ rushes in, as permeability is increased:
500 to 5000 times
When does the Na+ inactivation gate reopen after an action potential
once the resting membrane potential has been reached again
Why does decreased Ca++ lead to ectopy
Ca+ is thought to bind to Na+ channel proteins increasing the voltage required to open the channels and invoke APs. Without Ca+ binding exitability happens easily
2 tests to diagnose hypocalcemia
Chvostek’s sign
Trousseau’s Sign
EMF
Electromotive force
Propagation of AP? what direction?
Bi-directional
Each nerve can send how many inpuses before loosing enough ions to cease to function
100,000 to 50,000,000
