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Exercise 15Exercise 15
Histology of Histology of Nervous TissueNervous Tissue
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(a) cell body (soma); (b) Nissl bodies; (c) dendrites; (d) axon; (e) axon hillock; (f) synaptic terminals (a.k.a., axon terminals).
(a) Schwann cells; (b) neurilemma of a Schwann cell; (c) myelin sheath of a Schwann cell; (d) nucleus of a Schwann cell; (e) axon of a neuron; (f) node of Ranvier.
(a) axon terminal; (b) synaptic cleft; (c) postsynaptic membrane; (d) synaptic vesicles (if shown)
Two Cell Types in Neural TissueTwo Cell Types in Neural Tissue
1.1. NeuronNeuron
2.2. Neuroglia (glial) cellNeuroglia (glial) cell
Fig. 12-1
Neuroglia (glial) cellNeuroglia (glial) cell• Several typesSeveral types
Old Edition: 12-6
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Figure 15.1 Neuroglia.
Capillary
Neuron
Astrocyte
Neuron
Microglialcell
Cilia
Myelin sheath
Process ofoligodendrocyte
Nervefibers
Satellitecells
Cell body of neuron
Schwann cells(forming myelin sheath)
Ependymalcells
Brain orspinal cordtissue
Nerve fiber
Astrocytes are the most abundant CNS neuroglia
Microglial cells are defensive cells in the CNS.
Ependymal cells line cerebrospinalfluid-filled cavities.
Oligodendrocytes have processes that formmyelin sheaths around CNS nerve fibers.
Satellite cells and Schwann cells (which formmyelin) surround neurons in the PNS.
Fluid-filled cavity
• Central Nervous SystemCentral Nervous System– Brain & spinal cordBrain & spinal cord
• Peripheral Nervous SystemPeripheral Nervous System– Cranial nerves, spinal nerves, ganglia, Cranial nerves, spinal nerves, ganglia,
and nerve plexusesand nerve plexuses
CNS vs. PNSCNS vs. PNS
• Sensory (afferent)Sensory (afferent)
• Motor (efferent)Motor (efferent)
Neurons classified by FunctionNeurons classified by Function
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Figure 15.7 Classification of neurons on the basis of function.
GanglionCell body
Central process(axon)
Whitematter
Graymatter
Spinal cord(central nervous system)
To effectors(muscles)
Spinal nerve
Peripheralprocess (axon)
Receptiveendings
Afferent transmission
Efferent transmission
Interneuron
Motor neuron
Sensory neuron
• Mixed Mixed – Carries sensory & motor Carries sensory & motor
– All spinal nerves, most cranial nervesAll spinal nerves, most cranial nerves
• PurePure– Carry only sensory or only motorCarry only sensory or only motor
Neurons classified by Impulse Neurons classified by Impulse DirectionDirection
Impulse toward CNS only
(some cranial nerves)
Impulse to an organ, muscle, etc.
(some parts of spinal cord…)
• GanglionGanglion– Cluster of cell bodies in the PNSCluster of cell bodies in the PNS– ““gray matter”gray matter”
• NucleiNuclei– Clusters of cell bodies in the CNSClusters of cell bodies in the CNS
• TractTract– Neuron processes in the CNSNeuron processes in the CNS– ““white matter”white matter”
• NerveNerve– Neuron processes in the PNSNeuron processes in the PNS
Neuron TerminologyNeuron Terminology
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Figure 15.2a Structure of a typical motor neuron.
Dendrites Cell body
Nucleus
roughendoplasmicreticulum
Axon hillock
AxonImpulsedirection Myelin sheath gap
(node of Ranvier)
Axon terminalsSchwann cell
Terminal branches
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Figure 15.2b Structure of a typical motor neuron.
Nucleus ofneuroglial cell
Neurofibril
Nucleus
Nucleolus
Dendrites
Chromatophilicsubstance
Myelinated Nerve Fibers of PNSMyelinated Nerve Fibers of PNS
• Schwann Cells: Schwann Cells: – NeurilemmaNeurilemma: :
peripheral part of cellperipheral part of cell– NucleusNucleus: within the : within the
neurilemma neurilemma (superficial)(superficial)
Fig. 12-5
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Figure 15.3a Myelination of a nerve fiber (axon) by Schwann cells. (1 of 4)
Schwanncell plasmamembrane
Schwann cellcytoplasm
Schwann cellnucleus
Axon
Myelinsheath
Schwann cellcytoplasm
A Schwann cellenvelops an axon.
The Schwann cell thenrotates around the axon,wrapping its plasmamembrane loosely aroundit in successive layers.
The Schwann cellcytoplasm is forced frombetween the membranes.The tight membranewrappings surroundingthe axon form the myelinsheath.
1
2
3
Myelinated Nerve Fibers of PNSMyelinated Nerve Fibers of PNS
• Myelin sheathMyelin sheath• AxonAxon• Node of RanvierNode of Ranvier
Fig. 12-5
SynapseSynapse
• Connection between the Connection between the
axon terminalterminal & the next cell & the next cell((presynaptic neuronpresynaptic neuron) () (postsynapticpostsynaptic
neuronneuron or other cell) or other cell)
Fig. 12-5
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Figure 15.2c Structure of a typical motor neuron.
Presynapticneuron
Direction ofaction potential
Mitochondrion
Synapticvesicles
Postsynapticneuron
Synaptic cleft
Axonterminal
SynapseSynapse
• Synaptic vesiclesSynaptic vesicles– In axon terminalIn axon terminal– Contain Contain
neurotransmittersneurotransmitters• Acetylcholine most Acetylcholine most
commoncommon
Fig. 12-5
12-2
Nerve impulse travelsNerve impulse travels
Fig. 12-5
12-2
Structure of a Nerve
13-6
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Figure 15.8a Structure of a nerve showing connective tissue wrappings.Axon
Myelin sheath
Endoneurium
Perineurium
Epineurium
Fascicle
Bloodvessels
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Figure 15.6 Photomicrographs of neurons.
Dendrites
Cellbody
Dendrites
Cellbody
Nervefibers
Satellitecells
Cellbodies
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Review Figure 15.1
© 2014 Pearson Education, Inc.
Review Figure 15.2
