1 10.1: introduction cell types in neural tissue: neurons neuroglial cells (also known as neuroglia,...
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10.1: Introduction
• Cell types in neural tissue:• Neurons• Neuroglial cells (also known as neuroglia, glia, and glial)
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Dendrites
Cell body
Axon
Nuclei ofneuroglia
© Ed Reschke
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Divisions of the Nervous System
• Central Nervous System (CNS)• Brain• Spinal cord
• Peripheral Nervous System (PNS)• Cranial nerves• Spinal nerves
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Brain
(a)
Spinalcord Spinal
nerves
Cranialnerves
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Divisions of Peripheral Nervous System
• Sensory Division• Picks up sensory information and delivers it to the CNS
• Motor Division• Carries information to muscles and glands
• Divisions of the Motor Division:• Somatic – carries information to skeletal muscle• Autonomic – carries information to smooth muscle, cardiac muscle, and glands
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Divisions Nervous SystemCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sensory division Sensory receptors
Motor division
Skeletal muscle
Brain
(a) (b)
Spinalcord Spinal
nerves
Cranialnerves
Central Nervous System(brain and spinal cord)
Peripheral Nervous System(cranial and spinal nerves)
Smooth muscleCardiac muscleGlands
AutonomicNervousSystem
SomaticNervousSystem
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Functions of Nervous System
• Sensory Function (receiving information)
• Sensory receptors gather information• Information is carried to the CNS
• Integrative Function (deciding what to do about information)
• Sensory information used to create:
• Sensations• Memory• Thoughts• Decisions• Motor Function (acting
on information)• Decisions are acted upon • Impulses are carried to effectors
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10.3: Description of Cells of the Nervous System
• Neurons vary in size and shape
• They may differ in length and size of their axons and dendrites
• Neurons share certain features:
• Dendrites
• A cell body
• An axon
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Neuron StructureCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cell body
Neurofibrils
Nucleus
Nucleolus
Dendrites
Impulse
Nodes of Ranvier
Myelin (cut)
Axon
Axon
Chromatophilicsubstance(Nissl bodies)
Axonalhillock
Portion of acollateral
Schwanncell
Nucleus ofSchwann cell
Synaptic knob ofaxon terminal
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10.4: Classification of Neurons and Neuroglia
• Neurons vary in function
• They can be sensory, motor, or integrative neurons
• Neurons vary in size and shape, and in the number of axons and dendrites that they may have
• Due to structural differences, neurons can be classified into three (3) major groups:
• Bipolar neurons
• Unipolar neurons
• Multipolar neurons
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Classification of Neurons: Structural Differences
• Bipolar neurons• Two processes• Eyes, ears, nose
• Unipolar neurons• One process• Ganglia of PNS• Sensory
• Multipolar neurons• 99% of neurons• Many processes• Most neurons of CNS
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Dendrites
Axon Axon
AxonDirectionof impulse
(a) Multipolar
Centralprocess
Peripheralprocess
(c) Unipolar(b) Bipolar
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Classification of Neurons: Functional Differences
• Sensory Neurons• Afferent (approach)• Carry impulse to CNS• Most are unipolar• Some are bipolar
• Interneurons• Link neurons in CNS• Aka association neurons• Multipolar
• Motor Neurons• Efferent (exit)• Carry impulses away from CNS to effectors• Multipolar
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Central nervous system Peripheral nervous system
Cell body
Interneurons
Dendrites
Axon
Axon
Sensory (afferent) neuron
Motor (efferent) neuron
Cell body
Axon(central process)
Axon(peripheral process)
Sensoryreceptor
Effector(muscle or gland)
Axonterminal
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Types of Neuroglial Cellsin the PNS
1) Schwann Cells• Produce myelin found on peripheral myelinated neurons• Speed up neurotransmission
2) Satellite Cells• Support clusters of neuron cell bodies (ganglia)
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Types of Neuroglial Cellsin the CNS
2) Astrocytes• CNS• Scar tissue• Mop up excess ions, etc.• Induce synapse formation• Connect neurons to blood vessels
3) Oligodendrocytes• CNS• Myelinating cell
4) Ependyma or ependymal• CNS• Ciliated• Line central canal of spinal cord• Line ventricles of brain• Keep CSF moving
1) Microglia• CNS• Phagocytic cell
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Types of Neuroglial CellsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Microglial cell
Axon
Oligodendrocyte
Astrocyte
Capillary
Neuron
Myelinsheath (cut)
Node ofRanvier
Ependymalcell
Fluid-filled cavityof the brain orspinal cord
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10.5: The Synapse
• Nerve impulses pass from neuron to neuron at synapses, moving from a pre-synaptic neuron to a post-synaptic neuron.
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Dendrites
Impulse
Impulse
Impulse
Synapticcleft
Axon ofpresynapticneuron
Cell body of postsynaptic neuron
Axon of postsynaptic neuron
Axon ofpresynapticneuron
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Synaptic Transmission
• Neurotransmitters are released when impulse reaches synaptic knob
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Mitochondrion
Synaptic knob
(a)
Synaptic cleft
Neurotransmitter
Axon
Ca+2
Presynaptic neuron
Direction ofnerve impulse
Synapticvesicles
Cell body or dendriteof postsynaptic neuron
Synapticvesicle
Vesicle releasingneurotransmitter
Axonmembrane
Polarizedmembrane
Depolarizedmembrane
Ca+2Ca+2