Nervous System

-Central Nervous System

-Peripheral Nervous System

Brain

Spinal Cord

Cranial Nerves

Spinal Nerves

Peripheral Ganglia

Division of the nervous system

-Central Nervous System

-Peripheral Nervous System

Brain

Spinal Cord

Cranial Nerves

Spinal Nerves

Peripheral Ganglia

Division of the nervous system

Central Nervous System (CNS)

7 Main Parts of the CNS

• Spinal Cord• Medulla oblongata• Pons• Cerebellum• Midbrain• Diencephalon• Cerebrum

Directions in the nervous system - Axes

Orientation Axes in the brain

Rostral-Caudal (front-back) anterior-posterior

Dorsal-Ventral (up – down)

Lateral-Medial (sideways – mid)

Directions in the nervous system - Planes

Maturation of the CNS

Brain weight at birth: 400 gAt 2 years ~ 1000 gAdult ~1500 g

Maturation is mostly based on differentiation of nerve-cell connectivty

Nerve cells (neurons)

Sketch of a neuronNucleus

DendritesDendrites

Myelin

Axons

• Dendrites -- Input• Cell body (soma) -- Integration• Axon -- Output

Structure of neurons - Dendrites

At dendrites, the neurons recieve input via axons of other neurons at synapses

dendritic spine

Structure of neurons - Soma

In the soma of the cells, the cell nucleus is located (containing the DNA, i.e. genetic code); the synthesis of the proteins (within ribosomes and endoplasmatic reticulum) as well as energy production (mitochondria) are performed.

Structure of neurons - Axon

The axon transmits the information electrically from the soma to the synapses –it is surrounded by myelin that insulate the axon, provided by oligodendrocytes (glial cells)

Sketch of a neuronNucleus

DendritesDendrites

Myelin

Axons

• Dendrites -- Input• Cell body (soma) – Integration; protein production, genes, energy production• Axon -- Output

Electrical properties of neurons

The cell membrane isolates the intracellular from extracellular space

extracellular

intracellular

Electrical properties of neurons

The membrane potential

In the resting state, the intracellular space contains more negative ions than the extracellular space

extracellular

intracellular

difference of -70 mV

Ion channels connect the intra- and extracellular space

Opening of ion channels lead to a flux of ions through the membrane and to a change of the membrane potential

Different types of ion channels

The action potentialThe action potential is generated by ion flux through voltage gated channels

All or nothing principle!!

Propagation of the action potential

Synapse – Communication between neurons

Synapse – Communication between neurons

Presynaptic vesicles with neurotransmitter

Released transmitter

Transmitter binds to receptor

Na+Transmitter-

Resorption from synaptic cleft

Synapse – Communication between neurons

• Animasi

Excitatory and Inhibitory Synapses

Depending on the neurotransmitter and the receptor, the postsynaptic potential can be excitatory or inhibitory

Excitatory postsynaptic potential (EPSP) Inhibitory postsynaptic potential (EPSP)

Important Neurotransmitters

•Dopamine

•Epinephrine

•Norepinephrine

•Acetylcholine

•Serotonine

•Glycine

•GABA

•Glutamate

Two forms of integration of information

EPSC at dendrite can lead to action potential

Effect of inhibition on excitation

Glial cells

astrocytes oligodendrocytes

Astrocytes

Astrocytes connect the extraneuronal space with the blood vessels

Oligodendrocytes

Oligodendrocytes sheat the axons of the neurons to increase conductance of action potential

Summary neuronal communication

• intracellular electrical transmission of information (action

potential)

• neurons communicate via biochemical transmission

(neurotransmitters and receptors)

• integration of information in neurons by means of spatial and

temporal summation