Animal Cell Chromatin

Axonal Membrane of a Neuron

Ion Channels Cell membrane proteins that pass ions in and out of the cell Voltage-Gated Ion Channels gates are regulated by membrane voltage Chemical-Gated Ion Channels (also called Receptors) gates are regulated by neurotransmitters Iontotropic fast Metabotropic (G-protein coupled) requires second messenger cascade slow

Chemical-Gated Ion Channels Iontotropic Metabotropic

Electrochemical Gradient Inside the Cell More K+ Less Na+ Outside the Cell More Na+ Less K+ Ion Flow Mantra: Na+ In, K+ out

Depolarization/Hyperpolarization

Action Potential Phases 2 Rapid 3 1 Threshold 4 Phase Ion responsible Ion Channel Responsible 1. Threshold Na+ Chemical-gated Na+ channel 2. Rapid Depolarization Na+ Voltage-gated Na+ channel 3. Repolarization K+ Voltage -gated K+ channel 4. After Hyperpolarization K+ Na+/K+ pumps

Na+/K+ Pumps After the Action Potential, Na+/K+ pumps move Na+ ions back out of the cell and move K+ ions back into the cell The movement is against the concentration gradient of each ion so it requires energy (ATP) The pumps move 3 Na+ ions for every 2 K+ ions

Unmyelinated Propagation

Myelinated Propagation

Synaptic Action Voltage-gated Ca2+ channels Synaptic Potentials: EPSP IPSP

Synaptic Potentials Excitatory Postsynaptic Potential (EPSP) triggered by excitatory neurotransmitters open ligand-gated Na+ channels allows Na+ to flow inside the cell causing a slight depolarization of the postsynaptic cell moves the postsynaptic cell closer to firing an action potential Inhibitory Postsynaptic Potential (IPSP) triggered by inhibitory neurotransmitters open ligand-gated K+ channels or Cl- channels allows K+ to flow out of the cell or Cl- to flow inside the cell causing a slight hyperpolarization of the postsynaptic cell moves the postsynaptic cell further from firing an action potential

The Battle to -55mV IPSP EPSP