anatomy and physiology i the nervous system basic structure and function instructor: mary holman
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Anatomy and Physiology I
The Nervous System
Basic Structure and Function
Instructor: Mary Holman
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Three Basic Functions of the Nervous System
Sensory Function
Sensory or afferent neurons
Integrative Function
Interneurons
Motor Function
Motor or efferent neurons
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Fig. 10.2a
Brain
Spinalcord Spinal nerves (31 pairs)
Cranial nerves (12 pairs)
CNS vs PNS Central Nervous System Peripheral Nervous System
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Divisions of the Nervous System
Central Nervous System CNS
Brain
Spinal Cord
Peripheral Nervous System PNS
Cranial Nerves
Spinal Nerves
Ganglia
Sensory Receptors
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Divisions of the PNS
Somatic Nervous SystemSensory neurons
Motor neurons to skeletal muscle only
Autonomic Nervous SystemAutonomic sensory neurons - visceral
Motor neuron impulses to smooth & cardiac muscle,
glands and adipose tissue
Sympathetic vs. Parasympathetic Motor Divisions
Enteric Nervous SystemEnteric complexes of the gut
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Fig. 10.7
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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Cells of Neural Tissue
• Neurons
The electrically excitable nerve cells
responsible for the functions of the nervous system
• Neuroglia (glia, neuroglia, glial)
Support, nourish, & protect neurons
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Fig. 10.1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Dendrites
Cell body
Axon
Nuclei ofneuroglia
© Ed Reschke
The Neuron
600x
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Fig. 10.3
Copyright © 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
Neuron withMyelinatedAxon
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Fig. 10.6
Dendrites
Axon Axon
AxonDirectionof impulse
(a) Multipolar
Centralprocess
Peripheralprocess
(c) Unipolar(b) Bipolar(eyes,nose,ears)
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Neuroglia of the PNS
• Schwann Cells
Produce myelin sheath
• Satellite Cells
Support neuronal clusters in ganglia
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Fig. 10.4a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Dendrite
Node of Ranvier
Myelinated region of axon
Axon
Unmyelinatedregion of axon
Neuroncell body
Neuronnucleus
Medullated or Myelinated Axon
Schwann cells
Neurolemma containing nucleus
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Fig. 10.4b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Neurilemma
Myelin sheath
Neurofibrils
Axon
Axon
Node of Ranvier
Myelin
Schwann cellnucleus
© Biophoto Associates/Photo Researchers, Inc.
650x
Schwann Cell
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Fig. 10.4c
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EnvelopingSchwann cell
Schwanncell nucleus
Unmyelinatedaxon
Longitudinalgroove
Schwann Cell with non-myelinated Axons
Axon
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Fig. 10.5
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Schwanncell cytoplasm
Myelinsheath
Myelinatedaxon
Unmyelinatedaxon
© Dennis Emery
30,000x
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Neuroglia of the CNS• Astrocytes
major support cells
provide nutrients, monitor metabolism etc
• Oligodendrocytes myelinate axons in CNS
• Microgliaphagocytic
• Ependymalline ventricles & central canal
produce cerebrospinal fluid (CSF)
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Fig. 10.8
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Microglial cell
Axon
Oligodendrocyte
Astrocyte
Capillary
Neuron
Myelinsheath (cut)
Node ofRanvier
Ependymalcell
Fluid-filled cavityof the brain orspinal cord
Neuroglia of CNS
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Fig. 10.9
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Neuroglia
Neuroncell body
Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, by R.G. Kessel and R.H. Kardon. ©1979 W.H. Freeman and Company
SEM 10,000x
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Fig. 10.10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
AxonSite of injury Schwann cells
(a)
(b)
(c)
(d)
(e)
Changes over time
Motor neuroncell body
Former connectionreestablished
Schwann cellsForm new myelin sheath
Schwann cell tubeextends distal to injury
Proximal end of injured axon regenerates into tube of Schwann cells
Distal portion ofaxon degenerates
Skeletalmuscle fiber
Axonal Repair