THE PHYSIOLOGICAL APPROACH

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Presentation transcript:

THE PHYSIOLOGICAL APPROACH Lecture 3

Early history & Parallels with technology Aristotle

Early history & Parallels with technology Aristotle Galen

Early history & Parallels with technology Aristotle Galen Descartes

Early history & Parallels with technology Aristotle Galen Descartes Mueller

Early history & Parallels with technology Aristotle Galen Descartes Mueller

Neurons & Electrical Signals Johannes Mueller (1842): Doctrine of specific nerve energies: perceptions depend on “nerve energies” reaching the brain and that the specific quality we experience depends on which nerves are stimulated

The neuron

The neuron Flow of information

Recording electrical signals in neurons

Recording electrical signals in neurons

Recording electrical signals in neurons

Recording electrical signals in neurons

Recording electrical signals in neurons

The resting membrane potential Na+ K+ Na+ Na+ OUTSIDE Na+ Na+ K+ K+ Na+ INSIDE K+ K+ K+ K+ Na+ Na+ OUTSIDE Na+ Na+ K+ Na+

The resting membrane potential Na+ K+ Na+ Na+ OUTSIDE Na+ Na+ K+ K+ INSIDE Na+ K+ K+ K+ K+ Na+ Na+ Na+ OUTSIDE Na+ K+ Na+

What accounts for activity states? Electrostatic force Chemical diffusion Selectively permeable membranes

Electrostatic force & Chemical diffusion

Selectively permeable membranes

The action potential: defined Action potential: brief propagated changes in neuronal polarization that travel rapidly along the axon Depolarization: decreased negativity inside the neuron Threshold: a stimulus intensity just adequate to trigger an action potential All-or-none property: changing stimulus intensity does not affect action potential size but does affect rate of firing

The action potential Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ OUTSIDE Na+ Na+ K+ K+ Na+ INSIDE K+ K+ K+ K+ Resting membrane potential at potassium equilibrium (-70mV)

The action potential Na+ Na+ Na+ K+ K+ Na+ Na+ Na+ K+ K+ Na+ K+ K+ OUTSIDE Na+ Na+ K+ K+ Na+ Na+ Na+ INSIDE Na+ K+ K+ Na+ K+ K+ +40 Sodium flows into the axon Depolarizes to -40 mV, or threshold Action potential results - 40

The action potential K+ K+ K+ K+ Na+ Na+ K+ Na+ Na+ K+ Na+ OUTSIDE K+ K+ Na+ Na+ K+ Na+ Na+ INSIDE Na+ K+ Na+ Na+ channels inactivate (absolute refractory period) – completely unresponsive to a second stimulus Potassium flows out of the axon

The action potential K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ K+ Na+ OUTSIDE K+ K+ Na+ Na+ Na+ Na+ INSIDE Na+ K+ Na+ Potassium continues to flows out of the axon (relative refractory period)

The action potential Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ OUTSIDE Na+ Na+ K+ K+ Na+ INSIDE K+ K+ K+ K+ Resting membrane potential: back at potassium equilibrium (-70 mV)

The synapse

Chemical & electrical events at the synapse Presynaptic terminal Postsynaptic spine

Excitatory & inhibitory input affect firing rate excitatory input inhibitory input

Excitatory & inhibitory input affect firing rate excitatory input inhibitory input

Excitatory & inhibitory input affect firing rate excitatory input inhibitory input

Excitatory & inhibitory input affect firing rate excitatory input inhibitory input

Basic Structure of the Brain

Localization of function in the brain

Localization of function in the brain Franz Joseph Gall (1796)