Neurophysiology Flashcards
Action Potential
conduction-electrochemical change caused by ions crossing cell membrane occurring along neuron
Resting Membrane Potential
- 70 mv
Negative anionic proteins inside cell contribute
Why is the cell membrane selectively permeable?
Voltage gated channels that open and close depending on the membrane potential
Is the cell membrane more permeable to potassium or sodium?
75x more permeable to K due to more nongated leakage channels
What leaks out, what leaks in?
Potassium leaks out because the concentration prevails, and Sodium leaks in
How does sodium leak in?
The cell membrane is almost impermeable to Sodium because of low leakage channels, but electrical and concentration gradients are out to in so sodium comes in
Na/K/ATPase pump
- active transport requires ATP and moves sodium and potassium against the gradient to return ions
3 Na in, 2 K in
Action Potential
nerve impulse is firing, takes potential from -70 to +35 mv
Small patches of membrane
Happens because of the redistribution of Na and K
Initiation
comes from a stimulus whether it’s another neuron, change in pH, or temperature
Depolarization
Membrane potential becomes less negative, toward 0 and increases change to fire fully to an action potential
What happens when stimulus reaches the threshold (50 mv)?
All channels open in the area and Na floods inside and this is the upswing of action potential.
Refractory period
Depolarization peaks at +35 mv, the Na channels close and are inactive until membrane reaches resting potential again
Recovery
Na/K/ATPase pumps restore original resting concentrations of Na and K inside cell
Synapse
area where neurons meet
Presynapse
presynaptic membrane
terminal branch of axon in neuron #1
Synaptic Cleft
fluid filled space of extracellular (PNS) or cerebrospinal (CNS) fluid
Postsynapse
postsynaptic membrane
receptive area of neuron #2 (postsynaptic neuron)
The Process of Chemical Communication Step 1
Action potential reaches the end of axon of presynaptic neuron
The Process of Chemical Communication Step 2
Stimulates voltage regulated Ca++ channels to open and calcium moves in
The Process of Chemical Communication Step 3
Ca stimulates exocytosis of synaptic vesicles containing neurotransmitters
The Process of Chemical Communication Step 4
Neurotransmitters cross synaptic cleft
The Process of Chemical Communication Step 5
Neurotransmitter binds receptors on postsynaptic membrane/neuron #2
The Process of Chemical Communication Step 6
Causes channels to to open. Depolarization in postsynaptic neuron due to Na entering
The Process of Chemical Communication Step 7
Once the action potential stops, there is no calcium diffusion, exocytosis stops and postsynaptic channels close
What happens to leftover neurotransmitters?
It is reuptaken and recycled by the presynapse and broken down by synaptic cleft enzymes
EPSP (excitatory postsynaptic potential)
graded potential = local stimulatory response to increase probability of postsynaptic action potential formation, depolarizes neuron
IPSP (inhibitory postsynaptic potential)
graded potential = local inhibitory response to decrease probability of AP formation, hyperpolarizes neuron
Spatial Summation
EPSP and IPSP add up by location
Temporal Summation
EPSP AND IPSP add up by time
Excitatory Neurotransmitters
glutamate and aspartate
- increase permeability to Na+ at postsynapse to generate EPSPs
Inhibibitory
glycine and GABA
- decrease permeability to Na+, increase Cl- to generate IPSPs
Both Neurotransmitters
acetylcholine, norepinephrine, dopamine (all from tyrosine)
