(a) gK, Vm = EK

(b) gNa >> gK, sodium influx

(c) gK >> gNa, pottassium efflux

(d) gK, Vm = EK

A Mechanism for the Action Potential

Action Potential Conduction (part I)

• Entry of positive charge during the action potential causes the membrane just ahead to depolarize to threshold. Because the axonal membrane is excitable the action potential travels without decrement.

• Typical conduction velocity:10 m/sec

• Conduction velocity increases with axonal diameter

• Stellate cell-constant firing rate

• Pyramidal cell-Adaptation, decreased firing rate over time OR,

•Bursting, rapid cluster of action potentials followed by a pause.

Neurons Exhibit Different Patterns of Action Potential Generation

Action potentials invading the axon terminals cause the release of chemical neurotransmitters

Neurons can:

• transmit a chemical signal (known as neurotransmitters)

• receive signals through receptors that bind neurotransmitters

• Can study receptor subtypes using different drugs

• One neurotransmitter can bind to multiple receptor types

• No two transmitters bind to the same receptor

There can be multiple receptor subtypes

Cholinergic synaptic transmissionHeterogeneous localization of receptors

(e.g. - heart versus skeletal muscle)

Agonists versus antagonists

Glutamatergic synaptic transmission

Dendrites integrate information from multiple inputs

The Action potential

Integrated synaptic inputs determines whether a neuronreaches threshold to fire an action potential

Experience can modify the contribution of inputs

Drugs can alter synaptic communication between neurons

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This is your brain. This is your brain ...