11-2. Classification of Neurons and Myelination Flashcards
What are the ways to classify neurons?
structural (# of processes from cell body) or functional (what they do)
multipolar neuron
many processes extend from the cell body; all are dendrites except for a single axon.
What is the most common structural neuron?
multipolar
What type of neuron is found in the brain and spinal cord?
multipolar
bipolar neuron
two processes, one dendrite and one axon.
Where are bipolar neurons found?
retina, inner ear and lining of nose
unipolar neuron
one process extends from the cell body, then splits into a centraol process (axon) and a peripheral process (dendrite)
What are sensory neurons classified as structurally?
unipolar
sensory neuron
transmits impulses from receptors (in the periphery) into the CNS
motor
carries impulses away from the CNS, out to effectors
Motor neurons are usually ____.
multipolar neurons
association neuron
lies between sensory and motor neurons - 90% of all neurons
Association neurons are usually ____, and are found entirely in the ____.
multipolar; CNS
myelin sheath
white, phospholipid covering around many axons; insulates the neurons electrically (prevents “cross-talk”) and increases the speed of nerve impulse conduction
white matter
myeline is responsible for the white color in the brain and spinal cord
What are elements of myelination in the PNS?
schwann cells, neurilemma, nodes of ranvier
What are elements of myelination in the CNS?
oligodendorcytes
schwann cells
flat neuroglial cells that wrap around the axon many times in a jelly-roll fashion. Inner layers compose the myelin sheath
neurilemma
the outer, thick layer that contains the nucleus and most of the cytoplasm. It helps injured neurons repair themselves
nodes of ranvier
gaps that occur at regular intervals along the myelin sheath; spaces between adjacent Schwann cells (which do not touch). The gaps force the nerve impulse to jump from node to node, increasing the speed of conduction
oligodendrocytes
form the myelin sheath around axons in the CNS. Have nodes of Ranvier but lack a neurilemma
Injured PNS neurons [can / cannot] repair themselves.
can - have a neurilemma
Injured CNS neurons [can / cannot] repair themselves.
cannot - lack a neurilemma
A nerve impulse revolves around the ____ and ____ of 2 ions across the plasma membrane: ___ and ____.
diffusion; active transport; Na+; K+