Brain and Behavior Neurons

W HAT ARE NEURONS ? Cells transmitting info in the nervous system Neurons exist in circuits  Group of neurons connected in a precise, directionally oriented pathway 2

W HAT N EURONS H AVE IN C OMMON W ITH O THER C ELLS 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 3

W HAT N EURONS H AVE IN C OMMON W ITH O THER C ELLS Cytoplasm = material enclosed by plasma membrane Cytoplasmic Organelles (“little organs”)  Mitochondria Energy source for cell 4

 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 W HAT N EURONS H AVE IN C OMMON W ITH O THER C ELLS

Golgi Apparatus Type of Smooth ER Produces lysosomes Breaks down substances no longer needed in the neuron Package synaptic vesicles Released in terminal buttons W HAT N EURONS H AVE IN C OMMON W ITH O THER C ELLS

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 7

U NIQUE F EATURES OF N EURONS : T HE A XON 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 cells 8

S TRUCTURE OF N EURONS Collateral axons 9

T HE U NIQUE F EATURES OF N EURONS : T HE D ENDRITES Protrude from cell body (soma) Dendrites RECEIVE information from other neurons Dendrites + Soma = Receiving zone for incoming messages 10

S TRUCTURE OF N EURONS 11

S TRUCTURE OF N EURONS 12

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

H OW ARE N EURONS C LASSIFIED ? 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 14

H OW ARE N EURONS C LASSIFIED ? 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 15

H OW ARE N EURONS C LASSIFIED ? Interneurons Connect different neurons within the brain or spinal cord Bipolar neurons – two main extensions: axon and dendrite 16

O THER C ELLS & S TRUCTURES OF THE N ERVOUS S YSTEM : G LIAL C ELLS 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 17

O THER C ELLS AND S TRUCTURES OF THE N ERVOUS S YSTEM : G LIAL C ELLS 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 injury 18

O THER C ELLS AND S TRUCTURES OF THE N ERVOUS S YSTEM : G LIAL C ELLS Myelination  Provided by glial cells Wrap themselves around axons of neurons  Allows for rapid transmission of impulses 19

O THER C ELLS AND S TRUCTURES OF THE N ERVOUS S YSTEM : G LIAL C ELLS What glial cells provide the myelin?  In central nervous system  Oligodendrocytes  In peripheral nervous system  Schwann cells 20