Transcript the physiological approach

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
Flow of information
The neuron
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
OUTSIDE
INSIDE
Na+
Na+
K+
Na+
Na+
K+ K+
Na+
K+
K+
K+
Na+
Na+
OUTSIDE
K+
Na+
K+
Na+
Na+
Na+
The resting membrane potential
OUTSIDE
INSIDE
Na+
Na+
Na+
K+ K+
K+
K+
Na+
Na+
K+
Na+
Na+
OUTSIDE
K+
Na+
K+
K+
Na+
Na+
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
OUTSIDE
INSIDE
Na+
Na+
K+
Na+
K+
Na+
K+ K+
Na+
K+
K+
Na+
K+
Resting membrane potential at potassium
equilibrium (-70mV)
The action potential
OUTSIDE
K+
Na+
Na+
+
INSIDE
+ K+
+
Na
+
K
Na
Na
Na+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+
OUTSIDE
INSIDE
K+
Na+
Na+
K+
K+
K+ Na+
K+
Na+
Na+
Na+
K+
Na+ channels inactivate (absolute refractory
period) – completely unresponsive to a second
stimulus
Potassium flows out of the axon
The action potential
K+
OUTSIDE
INSIDE
K+
Na+
Na+
K+
+
+
K
K
K+
Na+
Na+
Na+
Na+
K+
Potassium continues to flows out of the
axon (relative refractory period)
The action potential
OUTSIDE
INSIDE
Na+
Na+
K+
Na+
K+
Na+
K+ K+
Na+
K+
K+
K+
Resting membrane potential: back at
potassium equilibrium (-70 mV)
Na+
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)