neurophysiology conduction, transmission and integration of neural signals chapter 3

38
Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Upload: gyles-watts

Post on 04-Jan-2016

226 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Neurophysiology

Conduction, transmission and integration of neural signals

Chapter 3

Page 2: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Summary of neural transmission

Resting potential and action potential signal propagation ionic bases of electrical potentials neural integration

Page 3: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Review of neuron Input zone (dendrites) Integration zone (axon

hillock) Conduction zone (axon) Output zone (axon terminals) Secretory event

Page 4: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Resting potential Definition of electrical potential

Potential energyElectrical potential

Page 5: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Resting potential

Recording and reference electrodes

amplifier oscilloscope

Experimental setup

Page 6: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Resting potential

Across the membrane

Page 7: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Changing membrane potential (creating unrest!)

Page 8: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Graded potentials (decremental conduction)

stimulator

Page 9: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The action potential-subthreshold-threshold of excitation-overshoot-afterpotential

Page 10: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Propagation of the action potential-non-decremental conduction

Page 11: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The ionic basis of membrane potentials

Diffusion gradients-substances move from areas of high concentration to areas of low concentration

Electrostatic gradients-substances can carry charge (ions)-substances move towards areas of unlike charge

Dynamic equilibrium-gradients can balance one another

Page 12: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The ionic basis of membrane potential

A- = proteinK+=potassiumNa+=sodiumCl-=chloride

+cations-anions

Page 13: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Dynamic equilibrium

Page 14: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Dynamic equilibria

For some species of ion (such as potassium), the relative concentrations on either side of the membrane are pretty much mathematically predictable (Nernst equation) just based on the balance of electrostatic and concentration gradients.

For others (such as sodium) this is not the case.

Page 15: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

This can only mean….

The membrane is not equally permeable to all ions.

At least….not all the time!

Page 16: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Nerve cell membranes are filled with interesting proteins

Page 17: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The disposition of ions in the resting nerve cell

Page 18: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3
Page 19: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Refractory periods

Note the difference between closed and inactivated sodium channels

-sodium channels only open briefly and then cannot open for some period of time

(absolute refractory period)

Page 20: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The pufferfish as a neuroscientific weapon

About three o’clock in the morning we found ourselves seized with an extraordinary weakness and numbness all over our limbs. I had almost lost the sense of feeling; nor could I distinguish between light and heavy bodies of such as I had strength to move, a quart pot full of water and a feather being the same in my hand…. --Captain James Cook--

Page 21: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Conduction of action potentials in unmyelinated axons

Page 22: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Conduction of action potentials in myelinated neurons-faster, cheaper

Page 23: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Consequences of demyelination -Multiple sclerosis

Page 24: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Synopsis of synaptic action

•Transmitter release•receptor action (metabotropic vs. ionotropic receptors)•postsynaptic potentials (EPSP’s and IPSP’s)

Page 25: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

The synapse

Page 26: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Electron micrograph of a synapse

Page 27: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Synaptic vesicles fuse with presynaptic membrane (movement of vesicles is caused by entry of calcium into presynaptic terminal

Page 28: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Freeze-fracture view of transmitter release

Page 29: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Receptors - a special kind of membrane channel

Page 30: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Ionotropic receptors

Page 31: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Metabotropic receptors-G-protein coupled

Page 32: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Varieties of postsynaptic potentials (PSP’s)

Excitatory (EPSP) usually when receptor channels

admit sodium Inhibitory (IPSP)

usually when receptor channels admit chloride

Page 33: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Termination of synaptic action

1. Deactivation

2. Re-uptake by transporters

Page 34: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Neural integration Spatial integration-ripples can collide and combine

Page 35: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Neural integrationSpatial integration-ripples can go up (excitatory) or down (inhibitory)

Page 36: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Neural integrationSpatial integration-ripples can combine

Page 37: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Another look at spatial summation

Page 38: Neurophysiology Conduction, transmission and integration of neural signals Chapter 3

Neural integrationTemporal integration-ripples can combine to make bigger ripples