One of the major communication systems in the body

Uses neurotransmitters to rapidly and directly conduct messages

One of the major communication systems within the body

Uses hormone to conduct messages

Hormones are slower than neuro-messages, but they last longer

Conduct electrical impulses to relay info

Cannot reproduce

Extremely high metabolic rate

Do not conduct impulses to relay info

More numerous than neurons

Capable of mitosis

Many types

Protect and support neurons

The cytoplasm around the nucleus

Contains mitochondriam ER, and other cell machinery

Lack centrioles

Clusters of free ribosomes which stain a dark gray (gray matter)

Synthesize neurotransmitter

Part of the cytoskeleton

Gives the axon its shape and allows transport of substances to the rest of the neuron

Enlarged region of axon near cell body

Where most action potentials begin

Branches near the end of the axon

Synaptic Knobs are at the ends of each Telodendria

Within each SK are synaptic vesicles that contain neurotransmitters

Can't distinguish dendrites from axon

Poorly understood

Two process

One forms the dendrite, the other the axon

Rare, involved in special senses

EX) vision, hearing

One process extending from the cell body

Splits into a dendrite and an axon

Most sensory receptors

Many dendrites and one axon extend from the cell body

Most common

EX) sensory, motor, interneuron

Receive input from surrounding as well as internal conditions

Relay information to the CNS

Unipolar

Collection of cell bodies in the PNS

Cell bodies are located outside the CNS in sensory ganglia

Collection of cell bodies in the CNS

Cell bodies are located outside the CNS in sensory ganglia

Most numerous

Between sensory and motor neurons

Responsible for learning and memory

Make up the ependyma

Lines ventricles and the central canal of the spinal cord where the cerebral spinal fluid ciculates

Specialized ependymal cells in the chroid plexus produce CSF

Ependymal cells in the ventricles have cilia to help circulate CSF

It is thought that stem cells exist in the ependyma that could possibly produce neurons

Largest and the most numerous

Star shaped structure due to cytoskeletal components

Gives structure for neurons in CNS

Create blood brain barrier

Extensions of astrocytes wrap around capillaries to allow only choice substances to enter the interstitial fluid of the brain

Isolates CNS from systematic circulation

Controls the composition of the ISF by regulating the concetration of ions

Allows for fast transport of nutrients (ions & gasses from the blood to neurons and vice versa)

Cytoplasmic extensions wrap around axon to form the myelin sheath

One oligodendrocyte can myelinate several axons

High in lipid content, they look glossy white => mylinated axons are called white matter; unmylinated => gray matter

Least numerous

Small

Phagocytes that can wander throughout the NS to ungulf debris and/or microbes

Myelinate axons in PNS

Not branching

1 schwann cell = 1 node of myelin

May enclose groups of axons

Collection of cell bodies of neurons in the PNS are localized in ganglia

The cell bodies are insulated and protected from surroundings by satellite and schwann cells

Regulate the environment

Similar to astrocytes in CNS

• Sodium Leak Channels- very slow leak channels
• Potassium Leak Channels- Much more permiable
• Leak channels are always open

Sodium/potassium Pump-

• 3 sodium out for every 2 potassium in; USES ATP
• Keeps transmembrane potential stable

Cell may deviate from RMP if certain gated channels open

Gated channel only open in response to a stimulous

A stimulous can be a chemical, as well as change in temperature, pH, pressure, or charge

Very common for synaptic transmission

Channel opens/closes when a specific neurotransmitter binds

Located on soma and dendrites of neurons

Open/close when the transmembrane potential changes

EX) voltage gated sodium, potassium, and calcium channels

Found along axolemma, sarcolemma, and synaptic knobs

2 components:

activation gate

inactivation gate

 Open when pressure is applied causing the membrane surface to change shape

Important to sense of touch

Located on dendrites