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Neuroscience course VT 2016

Membrane and action potentials 1

Peter Århem

Institutionen för neurovetenskap

Cells of the nervous system

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Types of nerve cells in human CNS

Types of nerve cells in human CNS

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Number of neurons in different species

Human 86 000 000 000 Octopus 300 000 000 Rat (Rattus norvegicus) 200 000 000 Mouse (Mus musculus) 71 000 000 Frog (Rana esculenta) 16 000 000 Bee (Apis mellifera) 960 000 Ant (?) 250 000 Fruit fly (Drosophila sp) 100 000 Aplysia sp 18 000 Caenorhabditis elegans 302

Multipolar nerve cell

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Myelinated axon

Glial cells in CNS

CNS: Astrocytes, oligodendrocytes, microglial cells PNS: Satellite-cells, Schwann-cells

Myelin

Microglial cell

Oligodendrocyte

Astrocyte

Interneuron

Projection neuron

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Glial cells in CNS

Organization of cell membrane

Ion channel

Cholesterol

Outside

Hydrophilc

Inside

Proteins

Phospholipid

Hydrophobic

Hydrophilc

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Electrical signals of nerve cells Purves et al. Chapter 2

The nerve impulse

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Types of impulses

The resting potential

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The resting potential electrochemical equilibrium

Distribution of ions

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The resting potential – dependence on K+

Ionic basis of resting potential

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Ionic basis of resting potential

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The conductance and permeability concept

Different conductances and equilibrium potentaials

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Electric circuit equivalent

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Membrane proteins necessary for resting potential

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The action potential

Intracellular recording – active and passive signals

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Action potentials

Compound action potential (extracellularly recorded)

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Axon types and conduction velocity

Type diameter (m) velocity (m/s)

A 13-20 80 -120

A 8-12 35 - 75

A 5-8 25-45

A 1-5 5 - 35

C 0.2-1.5 0.5 – 2

Ionic basis of action potentials

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Ionic basis of action potentials

Permeabilities during action potential

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Basics

1. How many neurons in a human brain? 2. Types of glial cells? 3. Which ion plays the main role for the resting

potential? 4. Equation(s) for the resting potential? 5. Describe an action potential. 6. What is meant by the all-or-nothing principle? 7. Which ion plays the main role for an axonal

action potential? 8. How fast does an action potential propagate? 9. Relation between axon diameter and impulse

velocity?