EEG- How do neurons communicate?

What is an EEG?

electrocencephalogram

“Electric Brain Recording”

What are we recording?

eavesdropping on the “conversation” of cerebral cortex interneurons

• the summation of all the postsynaptic potentials (EPSP and IPSP) of the neurons in the cerebral cortex

What are graded potentials? Where do they occur?

Graded potentials occur on the dendrites and cell body of the neuron. They are local (communication) and small amplitude (a few millivolts) changes in membrane potential and are graded because their magnitude depends directly on the amount of neurotransmitter released, the number of receptors activated, and the duration of ion channel opening

• vary in strength, allowing for spatial and temporal summation to determine if the threshold is reached.

Graded potentials can be?

summated allows multiple smaller, local voltage changes to add together to create a larger change in membrane potential. If the combined sum reaches a specific threshold at the axon hillock, it triggers an action potential.

Graded potential: Temporal summation

Occurs when a single presynaptic neuron fires in rapid succession, allowing potentials to add up over time.

Graded potential: Spatial summation

Occurs when multiple different presynaptic neurons fire simultaneously, with their potentials adding together at different locations on the neuron

Graded potentials can be both?

Graded excitatory (EPSP): move towards positive charge, closer to the trigger zone of -55, depolarizing

Graded inhibitory (IPSP): move towards negative charge, away from the trigger zone of -55, hyperpolarizing

Different neurotransmitters act on different channels

response depends on the channels neurotransmitters open/close

NT can bind and open ligand Na+ ion channel→

NT can bind and close ligand Na+ ion channel→

generates an EPSP

generates an IPSP

• because Na+ is not entering anymore, moving the cell in a negative direction

NT can bind and open ligand K+ ion channel→

NT can bind and close ligand K+ ion channel→

generates IPSP

• electrochemical gradient, more (-) outside and low concentration of K+ as well

generates EPSP

• more (+) charges remain inside

NT can bind and open ligand Ca2+ ion channel→

NT can bind and close ligand Ca2+ ion channel→

generate EPSP

• electrochemical gradient

generate IPSP

NT can bind and open ligand Cl- ion channel→

NT can bind and close ligand Cl- ion channel→

generates IPSP

generates EPSP