1. THE PHYSIOLOGICAL APPROACH
Lecture 3

2. Early history & Parallels with technology
Aristotle

3. Early history & Parallels with technology
Aristotle
Galen

4. Early history & Parallels with technology
Aristotle
Galen
Descartes

5. Early history & Parallels with technology
Aristotle
Galen
Descartes
Mueller

6. Early history & Parallels with technology
Aristotle
Galen
Descartes
Mueller

7. 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

8. The neuron

9. The neuron
Flow of information

10. Recording electrical signals in neurons

11. Recording electrical signals in neurons

12. Recording electrical signals in neurons

13. Recording electrical signals in neurons

14. Recording electrical signals in neurons

15. 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+

16. 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+

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

18. Electrostatic force & Chemical diffusion

19. Selectively permeable membranes

20. 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

21. 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)

22. 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

23. 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

24. 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)

25. 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)

27. The synapse

28. Chemical & electrical events at the synapse
Presynaptic terminal
Postsynaptic spine

29. Excitatory & inhibitory input affect firing rate
excitatory input
inhibitory input

30. Excitatory & inhibitory input affect firing rate
excitatory input
inhibitory input

31. Excitatory & inhibitory input affect firing rate
excitatory input
inhibitory input

32. Excitatory & inhibitory input affect firing rate
excitatory input
inhibitory input

34. Basic Structure of the Brain

35. Localization of function in the brain

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