Lect 18 - neurophysiology 1; action potentials

Flashcards on the topic of action potentials and neurophysiology

How does a chemical signal transform into an electrical signal in neurons?

Chemical signal (neurotransmitter) binds to and opens chemically-gated ion channels, ions flow in/out changing voltage; if membrane reaches -60mV at axon hillock, an action potential begins.

How do chemically-gated ion channels operate, and where are they located?

Chemical neurotransmitter binds to ion channel, channel shape changes, ions cross membrane driven by electrochemical gradient; neurotransmitter unbinds, channel closes.

• located in dendrites & cell body

How do voltage-gated ion channels operate, and where are they located?

Membrane depolarized to threshold voltage, channel shape changes, ions cross membrane driven by electrochemical gradient; membrane potential changes causing channel to inactivate or close.

• located in axon hillock, axon, & axon terminals

How do mechanically-gated ion channels operate, and where are they located?

Deformation of the membrane, channel shape changes, ions cross membrane driven by electrochemical gradient; when membrane returns to original shape the channel closes.

• located in dendrites

What are local potentials (PSP)?

Excitatory or inhibitory voltage change in a small location of the dendrite/cell body of a POSTsynaptic cell

What happens during Excitatory local potentials (EPSPs)?

A presynaptic neuron releases excitatory neurotransmitter. When neurotransmitter binds, it opens chemical gated Na+ channels; Na+ enters postsynaptic cell causing depolarization

What happens during Inhibitory local potentials (IPSPs)?

A presynaptic neuron releases inhibitory neurotransmitter. When neurotransmitter binds, it opens chemically gated K+ or Cl- channels; K+ exits or Cl- enters postsynaptic cell, causing hyperpolarization.

What is spatial summation?

Summed input from multiple PREsynaptic neurons

What is temporal summation?

Summed input from repeated firing of one PREsynaptic neuron.

What are the 6 steps of action potentials

1. voltage gated Na⁺ channel opens when the membrane depolarises to -60mV

2. influx of Na⁺ causes ‘rapid depolarisation phae’ of the action potential

3. at +30mV, the voltage gated Na⁺ channels get inactivated and Na⁺ entry stops

4. voltage gated K⁺ channels open and K⁺ exits causing ‘repolarisation phase’ of the action potential

5. voltage gated K⁺ channels begin to close slowly and K⁺ still exits causing the ‘hyperpolarisation phase’ of the action potential. membrane potential reaches -90mV

6. all voltage gated K⁺ channels close and the membrane returs to -70mV through the help of sodium-potassium pump