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The Human Body in Health and Illness, 4th edition
Barbara Herlihy
Chapter 10: Nervous System: Nervous Tissue
and Brain
1
Lesson 10-1 Objectives
• Define the two divisions of the nervous system.
• List three functions of the nervous system.• Compare the neuroglia and neuron.• Explain the function of the myelin sheath.• Explain how a neuron transmits information.• Describe the structure and function of a
synapse.Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.2
Divisions of the Nervous System
• Central nervous system (CNS)
• Peripheral nervous system
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.3
Functions of the Nervous System
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reserved.4
Types of Nervous Tissue
• Neuroglia or glia– Most abundant type – Support, protect, insulate, nourish, and generally
care for neurons
• Neurons– Do the communicating for the nervous system – Long shape makes them delicate
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.5
Neuroglia
• Astrocytes• Ependymal cells• Microglia• Schwann cells • Oligodendrocytes
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.6
Parts of a Neuron
• Cell body• Dendrites• Axon– Myelin sheath– Nodes of Ranvier– Neurilemma– Axon terminal
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.7
Types of Neurons
• Sensory (afferent) neurons– Carry information from periphery toward the CNS
• Motor (efferent) neurons– Carry information from CNS toward periphery
• Interneurons– Found only in CNS; connect sensory and motor
nerves
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.8
Nerve Impulses or Signals
• Electrical signals convey information along a neuron
• Also called action potential• Move along sensory or motor neurons
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.9
The Action Potential
• Polarization: Resting state
• Depolarization: Stimulated state
• Repolarization: Return to resting
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.10
Ionic Basis of the Action Potential
• Polarization– K+ leaks from neuron.– Determines resting
membrane potential
• Depolarization– Na+ rushes in.
• Repolarization– K+ rushes out.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.11
Why Action Potential “Moves”
• Action potential– Forms at axon’s
beginning– Regenerates along
axon’s length– Enters axon terminal – Releases ACh from
vesicles
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.12
Increasing Action Potential’s Speed
• Myelin insulates axon.• Myelin exposes some
axonal membrane—nodes of Ranvier.
• Action potentials jump quickly from node to node, like a kangaroo.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.13
Communication across the Synapse
• ACh is – Secreted from neuron A – Diffused across synaptic cleft – Bound to receptors on neuron B
• Neuron B is activated.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.14
Lesson 10-2 Objectives
• Describe the four major areas of the brain.• Describe the functions of the four lobes of the
cerebrum.• Describe how the skull, meninges,
cerebrospinal fluid, and blood-brain barrier protect the central nervous system.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.15
Four Major Areas of the Brain
• Cerebrum• Diencephalon• Brain stem• Cerebellum
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reserved.16
Cerebrum: Four Lobes
• Frontal lobe• Parietal lobe• Temporal lobe• Occipital lobe
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reserved.17
Cerebrum: Markings
• Gyrus (convolution)• Fissures (sulci)– Central– Lateral– Longitudinal
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reserved.18
Frontal Lobe
• “ The executive” • Behavior• Personality• Motor control
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reserved.19
Frontal Lobe: Motor Activity
• Primary motor area– Precentral gyrus
• Frontal eye field • Motor speech area– Broca’s area
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reserved.20
Frontal Lobe: Motor Homunculus
• Shows percentages of frontal lobe devoted to body’s motor activities
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reserved.21
Other Cerebral Lobes• Parietal– Somatosensory area– Gustatory area
• Temporal– Auditory cortex – Gustatory area– Olfactory area
• Occipital– Visual cortex
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reserved.22
Functions Spanning Cerebral Lobes
• Speech areas– Span temporal, parietal and occipital lobes– Usually in left hemisphere– Wernicke’s area (helps translate thought into
speech)
• Association areas– Helps to interpret sensory information– Examples: Visual, auditory, somatosensory
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reserved.23
Diencephalon• Thalamus• Hypothalamus
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Brain Stem• Midbrain• Pons• Medulla oblongata• Vital center• Emetic center• Reflex center
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reserved.25
Cerebellum• Mediates
reflexes• Coordinates
motor activity• Evaluates
sensory input
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an imprint of Elsevier Inc. All rights reserved.
26
Structures Spanning Brain Divisions• Limbic system– Emotional brain
• Reticular formation: Reticular activating system; sleep-wake cycle, consciousness, gaze center
• Memory areas– Immediate memory– Short-term memory – Long-term memory
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reserved.27
Protecting the CNS: Four Layers
• Bone• Meninges• Cerebrospinal fluid• Blood-brain barrier
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reserved.28
Protecting the CNS: Meninges
• Dura mater• Arachnoid mater– Subarachnoid space
• Pia mater
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reserved.29
Protecting the CNS: Cerebrospinal Fluid (CSF)
• Formed in ventricles by choroid plexus
• Circulates through subarachnoid space– From central canal of
spinal cord – From foramina
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reserved.30
Drainage of CSF
• Drainage of CSF must equal its production.
• Arachnoid villi project into dural sinuses filled with blood.
• CSF drains into blood and leaves the brain.
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reserved.31
Protecting the CNS: The Blood-Brain Barrier
• Made of special cells (astrocytes) within cerebral capillaries.
• Prevents some toxins from entering CNS from blood
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.32