- group of axons in the central nervous system (CNS)

Tract

- group of axons found in the peripheral nervous system (PNS)

Nerve

- "ganglion" in the CNS

- group of cell bodies

Nucleus

- an area of the brain with a high concentration of somas

Gray matter

- an area of the brain with a high concentration of myelinated axons

White matter

- typically long projection neurons

(sensory, somas in dorsal root ganglion, from toe to base of brain)

- single, long process (neurite)

- cell body often found off to side or adjacent to axon

Unipolar (pseudounipolar) Neuron

- has two neurite processes that extend from the soma

- processes may be dendrites or axons

- middle retina cells, olfactory bulb, ganglia of CNVIII

Bipolar neurons

- most numerous in the brain

- several dendrites and one axon

- upper motor neurons of the precentral gyrus

Multipolar neurons

- size of neurons that has large cell bodies and is typically found in projection neurons

Golgi type I

- size of neurons that are small and typically found in local interneurons

Golgi type II

- produces myelin (white matter) in the CNS

- contributes myelin to several axons

oligodendrocytes (glial) cells

- produces myelin in the PNS

- only covers one segment of the axon with myelin (between two nodes of Ranvier)

- allow regrowth of of axons

Schwann cells

- cells that process neural information locally within a given nucleus

- information processing occurs with these

Interneurons

- found typically only on axons (or very large dendrites)

- produced by voltage-gated channels

- self-propagating and does not decrease with distance or time

Action Potential

- associated with non-voltage gated channels

- found on dendrites, axon terminals, and somas

- decrease with distance and time

- can add together

Graded potential

- special graded potential associated with the release of neurotransmitters

Secretory potential

- type of transport used to move proteins and membrane components from the soma to the axon terminal

- Ex: neurotransmitters and cytoskeleton components

- utilizes kinesin

- occurs at fast or slow rate

Anterograde

- transport used to re-cycle transmitters or membrane structural components

- can also transmit diseases (rabies virus, herpes, AIDS)

- utilizes dynein with fast transport

Retrograde

- associated components being moved at slow and fast rate (anterograde) respectively

skeletal structure components/transmitters and proteins

- a class of cells that support neurons that are not derived from neuroblasts

- astrocytes, oligodendrocytes, microglia, ependyma

Neuroglia

- largest class of glial cells

- support neurons, re-uptake ions, produce scar tissue, serve in blood-brain barrier

Astrocytes

- Respective location of Protoplasmic and fibrous astrocytes

Gray/White Matter

(GP + FW)

- in the fetus these cells form a railroad track map that neurons can follow

- when damaged, can create dense scarring

Radial glia

- most common type of brain tumor

Astrocytic

- these cells are rarely encountered in normal brain tissue

- when brain damage or infection occurs, these cells invade and proliferate to form macrophage-like cells that consume pathogens and neuronal debris

Microglia

- specialized glia that line the ventricles of the brain

- serve as a barrier between the CSF and the brain

- may also have a role in hormone or transmitter effects and cellular communication

Ependyma

- reinforcing sheath of delicate tissue that surrounds peripheral nerve fibers

- made up of collagen fibers and a few fibroblasts

- directly contacts the myelin of axons or axonal membrane and the perineurium

Endoneurium

- composed of concentric layers of mostly longitudinal arranged strands of collagen

- can contain microphages and fibroblasts

Perineurium

- dense external CT layer for all peripheral nerve

- mostly collagen and contacts dura of cranial and spinal nerves

- can contain elastic fibers

- arteries penetrate this layer and become arterioles before entering perineurium, capillaries in endoneurium

Epineurium

- silver based stains identify myelin left behind as the distal portion of an axon degenerates

Wallerian degeneration

- this repair mechanism is created after one or two nodes of the proximal axon degenerates and the other portion seals itself off

- an attempt by a recovering nerve to re-establish connection

Growth cone

- following nerve injury, this structure becomes pale (due to increased RNA/DNA activity) and displaces to one side of the soma (usually opposite the axon)

- also gets larger

Nucleus (Ganglion in PNS)

- infection, scar barriers, apposition of the severed ends of the nerve/tracts

Factors affecting nerve re-growth

- principal that says that if a neuron dies, all neurons that send information to that neuron will over time degenerate as well

Trans-neuronal degeneration

- results from the loss of neural input to muscle fibers

muscle atrophy

- nervous structure that senses pressure

- only fires a membrane potential when there is a change in pressure

- rapidly adapting

Pacinian Corpuscle