Brain and BehaviorNeurons

01.21.2016

WHAT ARE NEURONS?

• Cells transmitting info in the nervous system

• Neurons exist in circuits Group of neurons connected in a precise,

directionally oriented pathway

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WHAT NEURONS HAVE IN COMMON WITH OTHER CELLS

• Plasma membrane External wall of the cell Forms a boundary between internal and external

environment Double layer of lipids Gates

Defines boundary of the cell Detects substances Selectively permeable

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WHAT NEURONS HAVE IN COMMON WITH OTHER CELLS

• Cytoplasm = material enclosed by plasma membrane

• Cytoplasmic Organelles (“little organs”) Mitochondria

• Energy source for cell

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Ribosomes Place where proteins are

produced Endoplasmic

Reticulum (ER)• Synthesis, storage,

transport, evacuation of molecules

• E.g. Golgi Apparatus• Rough ER – produces protein• Smooth ER – produces lipids

and steroids

WHAT NEURONS HAVE IN COMMON WITH OTHER CELLS

• Golgi Apparatus• Type of Smooth ER• Produces lysosomes• Breaks down substances no longer needed in the

neuron• Package synaptic vesicles • Released in terminal buttons

WHAT NEURONS HAVE IN COMMON WITH OTHER CELLS

WHAT NEURONS HAVE IN COMMON WITH OTHER CELLS

• Nucleus Located at center of main body of cell Location of genetic information DNA=contains genetic instructions in development and

functioning of the organism RNA=transmit genetic information from DNA outside

nucleus for protein production

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UNIQUE FEATURES OF NEURONS:THE AXON

• Means of transmitting information (nerve impulses)• The brain has ~100billion neurons

• The axon SENDS information from the cell body to other neurons

• Axon terminal End of axon

• One axon per cell But, may have collateral axons

• Branches of the axon

• Allow communication with multiple cells8

STRUCTURE OF NEURONS

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THE UNIQUE FEATURES OF NEURONS:THE DENDRITES

• Protrude from cell body (soma)• Dendrites RECEIVE information from other

neurons• Dendrites + Soma

= Receiving zone for incoming messages

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STRUCTURE OF NEURONS

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STRUCTURE OF NEURONS

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Synapse• Synapse - Small gap between axon

terminal of Neuron A and dendrites/cell body of Neuron B

• Terminal buttons – at the end of axon branches• Secrete chemicals (NT’s) when action potential reaches

them

HOW ARE NEURONS CLASSIFIED?

• Sensory neurons AFFERENT neurons Receive sensory signals from sensory organs Send signals via short axons to CNS Unipolar/pseudo-unipolar neurons – one branch

is the axon, the other is the dendrite

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HOW ARE NEURONS CLASSIFIED?

• Motor neurons EFFERENT neurons Conduct motor commands from the cerebral

cortex to the spinal cord, or from the spinal cord to the muscles

Multipolar neurons – several short dendrites and one long axon

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HOW ARE NEURONS CLASSIFIED?

• Interneurons• Connect different neurons within the brain or spinal

cord• Bipolar neurons – two main extensions: axon and

dendrite

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OTHER CELLS & STRUCTURES OF THE NERVOUS SYSTEM: GLIAL CELLS

• There are two types of cells in the nervous system: • Neurons• Glial Cells

• Specialized support cells• Found in space between the nerve cells• General function: “housekeeping”• Produce myelin, covers axons

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OTHER CELLS AND STRUCTURES OF THE NERVOUS SYSTEM: GLIAL CELLS• Astrocytes

Most common type of glial cell

Primary function• “Clean up” excess neurotransmitters and ions from

extracellular space

Other functions• Support active areas with extra energy

• Clean up dead neurons after injury18

OTHER CELLS AND STRUCTURES OF THE NERVOUS SYSTEM: GLIAL CELLS• Myelination

Provided by glial cells• Wrap themselves around axons of neurons

Allows for rapid transmission of impulses

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OTHER CELLS AND STRUCTURES OF THE NERVOUS SYSTEM: GLIAL CELLS• What glial cells provide the myelin?

In central nervous system Oligodendrocytes

In peripheral nervous system Schwann cells

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