Lecture 18: Action Potentials Flashcards
(22 cards)
How does a chemical signal get converted into an electrical signal?
A neurotransmitter binds to and opens chemically-gated ion channels
Ions flow in or out, changing the voltage at a localized area of membrane
If the membrane voltage reaches -60mV at the axon hillock an electrical signal (action potential) begins)
What is the minimum membrane voltage required at the axon hillock for an action potential to begin
-60mV
What are the 3 types of gated ion channels
Chemically-gated ion channel
Voltage-gated ion channel
Mechanically-gated ion channel
What is the stimulus for chemically gated ion channels
Chemical neurotransmitter
What causes chemically gated ion channels to close
The neurotransmitter unbinding
What is the stimulus for voltage-gated ion channels
membrane depolarizes to threshold voltage (-60mV)
What is the stimulus for Mechanically-gated ion channels
deformation of the membrane
What causes mechanically gated ion channels to close
Returning to their original shape
Where are chemically gated ion channels found on the neuron
Dendrites and the cell bodies
Where are voltage gated channels found on the neuron
Axon hillock, axon and axon terminals
What is Resting Membrane potential and what is its value
At rest the intercellular space is more negative than the extracellular space
70mV
What is a local potential
An excitatory or inhibitory change in voltage in a small location (localized area) somewhere on the dendritic/cell body
membrane
What are two other names for local potentials
Post-synaptic potentials (PSP)
Graded potentials
*Because they vary in size depending on how many ions enter/exit
What is an EPSP
Excitatory Post-Synaptic Potential
How do EPSPs form
A presynaptic neuron releases excitatory neurotransmitter.
This opens Na+ channels causing depolarization
What are IPSPs
Inhibitory Post-Synaptic Potential
How do IPSPs form
A presynaptic neuron releases inhibitory neurotransmitter
(eg. GABA)
This opens chemically gated K+ or Cl- channels, causing hyperpolarization
What is an example of an inhibitory neurotransmitter
GABA
(gamma-aminobutyric acid)
What are the two ways in which local potentials are summed
Spatial summation
Temporal summation
What is Spatial summation
summed input from multiple pre-synaptic neurons
What is Temporal summation
summed input from repeated firing of one pre-synaptic neuron
At what voltage do voltage gate channels inactivate
+30mV
