1. Histology of Nervous Tissue
Ch. 12-2

2. Neurons vs. Neuroglia Neurons Neuroglia Provide unique functions
Sensing, thinking, remembering, controlling muscle activity, regulating glandular secretions
Support, nourish, and protect the neurons
Maintain homeostasis in the interstitial fluid that bathes them

3. 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

4. Parts of a Neuron Three parts Cell body Dendrites Axon
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

5. Parts of a Neuron

6. 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

7. Neural Diversity Multipolar neurons Bipolar neurons Unipolar 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

8. Neural Diversity

9. Others Purkinje cells – cerebellum
Pyramidal cells – cerebral cortex of brain

10. Neuroglia Actively participate in nervous tissue functioning
Do not generate action potentials
Can multiply and divide – neurons cannot

11. Types of Neuroglia CNS PNS
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

12. Types of Neuroglia

13. Types of Neuroglia

14. 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