Histology of Nervous Tissue
Ch. 12-2
Neurons vs. Neuroglia
Neurons
• Provide unique functions
• Sensing, thinking,
remembering, controlling
muscle activity, regulating
glandular secretions
Neuroglia
• Support, nourish, and
protect the neurons
• Maintain homeostasis in the
interstitial fluid that bathes
them
Neurons
• Vocabulary:
– Neuron – nerve cell
– Electrical excitability
• the ability to respond to a stimulus and convert it into an
action potential
– Stimulus
• any change in the environment that is strong enough to
initiate an action potential
– Action potential – nerve impulse
• An electrical signal that propogates (travels) along the
surface of the membrane of a neuron
• Can travel up to 280 mph
Parts of a Neuron
• Three parts
– Cell body
• Main part of the cell
• Includes organelles, nucleus, and cytoplasm
– Dendrites
• Receiving parts of the neuron
• Short, tapered, and highly branched
– Axon
• Transmitting parts of the neuron
• Long, thin, cylindrical
Parts of a Neuron
Parts of a Neuron
• Synapse – site of communication between 2
neurons or a neuron and an effector cell
• Synaptic end bulb – swollen end of an axon
where synaptic vesicles hold
neurotransmitters
Neural Diversity
• Multipolar neurons
– Several dendrites, one axon
– Found in brain and spinal cord
• Bipolar neurons
– One main dendrite, one axon
– Eye, ear, olfactory of brain
• Unipolar neurons
– Axon and dendrite fuse at beginning and then branch
– Occurs as an embryo
Neural Diversity
Others
• Purkinje cells –
cerebellum
• Pyramidal cells –
cerebral cortex of
brain
Neuroglia
• Actively participate in
nervous tissue functioning
• Do not generate action
potentials
• Can multiply and divide –
neurons cannot
Types of Neuroglia
• CNS
– Astrocytes – create blood-brain barrier, strength
– Oligodendrocytes – create myelin sheath around CNS
axons
– Microglia – remove cellular debris during neural
development
– Ependymal cells – assist with circulation of cerebrospinal
fluid
• PNS
– Schwann cells – create myelin sheath around PNS axons
– Satellite cells – support, regulate exchange of materials
Types of Neuroglia
Types of Neuroglia
Myelination
• Myelin sheath – multilayered lipid and protein
covering around some axons
• Provides insulation
• Increases speed of nerve impulse
• If a cell has myelin we say that it is myelinated
• Gaps in the myelin sheath are called nodes of
Ranvier