Neurotransmitters

Levels of Organization of Nervous System

• Cell: individual neurons

• Tissue: nerves, ganglia

• Organ: brain and spinal cord

• System: nervous system

Soma or cell body

The cell body of a neuron, which contains the nucleus

Dendrite

The branched, treelike extensions attached to the soma of a neuron;

receives information from neurotransmitters released from terminal button

of other neurons

Axon

The extension of a neuron, ending in branching terminal fibers, through

which messages are sent to other neurons or to muscles or glands

Terminal Button

The bud at the end of a branch of an axon; forms synapses with other

neurons; sends information to those neurons via neurotransmitters

Neurotransmitter

A chemical that is released by a terminal button; has an excitatory or

inhibitory effect on other neurons

Myelin Sheath

A layer of fatty cells segmentally encasing the fibers of many neurons; prevents messages from sending to adjacent neurons

Resting membrane potential

occurs because various ions are located in different concentrations in fluid inside and

outside the cell(-70mV)

Action Potential

the brief electrical impulse that provides the basis for conduction of information along an axon

• Sodium Channels open, Na+ rushes in

• Because of balance change, sodium chanells close

• Potassium Gates opes, K+ moves outside

Synapse

Junction between terminal button of one neuron and membrane – usually the somatic or dendritic membrane – of another

Communication across synaptic gap

When an action potential reaches a terminal button, the vesicles fuse with the presynaptic membrane of the terminal button, break open, and release their neurotransmitter into the synaptic cleft

Neurotransmitter communication

• Travel across the synaptic gap, bind to receptor sites to influence the impulse that will be generated

• Either excitatory or inhibitory effect

Ligands that bind to the postsynaptic membrane at binding sites can be

• A chemical naturally produced by the body like a neurotransmitter or

• A chemical from the outside like a medication or a poison

Reuptake

transporters located in the pre-synaptic membrane transport the molecules of neurotransmitter back into the cytoplasm – most common method

Enzymatic deactivation

destruction of a neurotransmitter by an enzyme after its release

Neurogenesis

Production of new neurons

• Adult brain has stem cells that can divide and produce new neurons