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HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 1
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Central Nervous System
• Central nervous system – the brain and spinal cord
• Directional terms unique to the CNS• Rostral – toward the nose
• Caudal – toward the tail
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
• Brain arises from the rostral part of the neural tube
• Three primary brain vesicles in 4-week embryo• Prosencephalon – the forebrain
• Mesencephalon – the midbrain
• Rhombencephalon – the hindbrain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
• Secondary brain vesicles• Prosencephalon
• Divides into telencephalon and diencephalon
• Mesencephalon – remains undivided
• Rhombencephalon • Divides into metencephalon and myelencephalon
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
• Structures of the adult brain• Develop from secondary brain vesicles
• Telencephalon the cerebral hemispheres
• Diencephalon thalamus, hypothalamus, and epithalamus
• Metencephalon pons and cerebellum
• Myelencephalon medulla oblongata
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
• Brain stem includes:• The midbrain, pons, and medulla oblongata
• Ventricles • Central cavity of the neural tube enlarges
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
Figure 13.2a-e
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Embryonic Development of the Brain
• Brain grows rapidly, and changes occur in the relative position of its parts• Cerebral hemispheres envelop the diencephalon
and midbrain
• Wrinkling of the cerebral hemispheres • More neurons fit within limited space
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Brain Development from Week 5 to Birth
Figure 13.3a-d
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Parts and Organization of the Brain
• Divided into four regions• Cerebral hemispheres
• Diencephalon
• Brain stem: midbrain, pons, and medulla
• Cerebellum
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Parts and Organization of the Brain
Figure 13.4
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Parts and Organization of the Brain
• Organization • Centrally located gray matter• Externally located white matter• Additional layer of gray matter external to white
matter• Due to groups of neurons migrating externally
• Cortex – outer layer of gray matter• Formed from neuronal cell bodies• Located in cerebrum and cerebellum
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Parts and Organization of the Brain
Figure 13.5
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ventricles of the Brain
• Expansions of the brain’s central cavity
• Filled with cerebrospinal fluid
• Lined with ependymal cells
• Continuous with each other
• Continuous with the central canal of the spinal cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ventricles of the Brain
• Lateral ventricles – located in cerebral hemispheres• Horseshoe-shaped from bending of the cerebral
hemispheres
• Third ventricle – lies in diencephalon • Connected with lateral ventricles by
interventricular foramen
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ventricles of the Brain
• Cerebral aqueduct – connects 3rd and 4th ventricles
• Fourth ventricle – lies in hindbrain• Connects to the central canal of the spinal cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ventricles of the Brain
Figure 13.6a, b
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 2
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
• Account for 83% of brain mass• Fissures – deep grooves – separate major regions
of the brain• Transverse fissure – separates cerebrum and
cerebellum
• Longitudinal fissure – separates cerebral hemispheres
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
• Sulci – grooves on the surface of the cerebral hemispheres
• Gyri – twisted ridges between sulci
• Prominent gyri and sulci are similar in all people
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
• Deeper sulci divide cerebrum into lobes
• Lobes are named for the skull bones overlying them
• Central sulcus separates frontal and parietal lobes• Bordered by two gyri
• Precentral gyrus
• Postcentral gyrus
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
Figure 13.7a
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The Cerebral Hemispheres
• Parieto-occipital sulcus • Separates the occipital from the parietal lobe
• Lateral sulcus • Separates temporal lobe from parietal and frontal
lobes
• Insula – deep within the lateral sulcus
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The Cerebral Hemispheres
Figure 13.7b, c
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The Cerebral Hemispheres
• Frontal section through forebrain• Cerebral cortex
• Cerebral white matter
• Deep gray matter of the cerebrum (basal ganglia)
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
Figure 13.8
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Cortex
• Home of our conscious mind
• Enables us to: • Be aware of ourselves and our sensations
• Initiate and control voluntary movements
• Communicate, remember, and understand
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Cortex
• Composed of gray matter• Neuronal cell bodies, dendrites, and short axons
• Folds in cortex – triples its size
• Approximately 40% of brain’s mass
• Brodmann areas – 52 structurally distinct areas
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional and Structural Areas of the Cerebral Cortex
Figure 13.11a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional and Structural Areas of the Cerebral Cortex
Figure 13.11b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Cortex
• Functional regions• Traditionally – studied brain-injured people and
animals• New discoveries – PET and fMRI
• Regions of the cerebral cortex • Perform distinct motor and sensory functions
• Memory and language spread over wide area
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Cortex
• Three kinds of functional areas• Motor areas
• Sensory areas
• Association areas
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Areas – Primary Motor Cortex
• Controls motor functions• Primary motor cortex (somatic motor area)
• Located in precentral gyrus (Brodmann area 4)
• Pyramidal cells – large neurons of primary motor cortex
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Areas – Primary Motor Cortex
• Corticospinal tracts descend through brainstem and spinal cord• Axons signal motor neurons to control skilled
movements
• Contralateral – pyramidal axons cross over to opposite side of the brain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Areas
• Specific pyramidal cells control specific areas of the body
• Face and hand muscles – controlled by many pyramidal cells
• Motor homunculus – body map of the motor cortex
• Somatotopy – body is represented spatially in many parts of the CNS
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Areas
Figure 13.10
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Motor Areas – Premotor Cortex
• Located anterior to the precentral gyrus
• Controls more complex movements
• Receives processed sensory information• Visual, auditory, and general somatic sensory
• Controls voluntary actions dependent on sensory feedback
• Involved in the planning of movements
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 3
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory Areas
• Cortical areas involved in conscious awareness of sensation
• Located in parietal, temporal, and occipital lobes
• Distinct area for each of the major senses
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory Areas – Primary Somatosensory Cortex
• Located along the postcentral gyrus• Corresponds to Brodmann areas 1-3
• Involved with conscious awareness of general somatic senses
• Spatial discrimination – precisely locates a stimulus
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory Areas – Primary Somatosensory Cortex
• Projection is contralateral • Cerebral hemispheres
• Receive sensory input from the opposite side of the body
• Sensory homunculus – a body map of the sensory cortex
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory Areas – Primary Somatosensory Cortex
Figure 13.10
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Association Areas
• Make associations between different types of sensory information
• Associate new sensory input with memories of past experiences
• New name for association areas – higher order processing areas
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Association Areas – Prefrontal Cortex
• Large region of the frontal lobe anterior to motor areas
• Performs cognitive functions• All aspects of thinking and perceiving
• Remembering and recalling information
• Also related to mood
• Has close links to the limbic part of the forebrain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Association Areas – Prefrontal Cortex
• Anterior pole of frontal cortex • Active in solving the most complex problems
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Lateralization of Cortical Functioning
• The two hemispheres control opposite sides of the body
• Hemispheres are specialized for different cognitive functions
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Lateralization of Cortical Functioning
• Left cerebral hemisphere – more control over:• Language abilities, math, and logic
• Right cerebral hemisphere – more involved with:• Visual-spatial skills
• Reading facial expressions
• Intuition, emotion, artistic and musical skills
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral White Matter
• Different areas of the cerebral cortex communicate:• With each other
• With the brainstem and spinal cord
• Fibers are usually myelinated and bundled into tracts
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral White Matter
• Types of tracts• Commissures – composed of commissural fibers
• Allows communication between cerebral hemispheres
• Corpus callosum – the largest commissure
• Association fibers • Connect different parts of the same hemisphere
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Cerebral White Matter
Figure 13.13a
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Cerebral White Matter
• Types of tracts (continued) • Projection fibers – run vertically
• Descend from the cerebral cortex
• Ascend to the cortex from lower regions
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Cerebral White Matter
Figure 13.13b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Projection Tracts
Figure 13.14a
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 4
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon
• Forms the center core of the forebrain
• Surrounded by the cerebral hemispheres
• Composed of three paired structures:• Thalamus, hypothalamus, and epithalamus
• Border the third ventricle
• Primarily composed of gray matter
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon and Brainstem
Figure 13.15
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon
Figure 13.16a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon
Figure 13.16b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon – The Thalamus
• Makes up 80% of the diencephalon
• Contains approximately a dozen major nuclei
• Send axons to regions of the cerebral cortex
• Nuclei act as relay stations for incoming sensory messages
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon – The Thalamus
• Afferent impulses converge on the thalamus• Synapse in at least one of its nuclei
• Is the “gateway” to the cerebral cortex
• Nuclei organize and amplify or tone down signals
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Thalamus
Figure 13.17b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon – The Hypothalamus
• Lies between the optic chiasm and the mammillary bodies
• Pituitary gland projects inferiorly
• Contains approximately a dozen nuclei
• Main visceral control center of the body
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Diencephalon – The Hypothalamus
• Functions include the following: • Control of the autonomic nervous system• Control of emotional responses• Regulation of body temperature• Regulation of hunger and thirst sensations• Control of behavior• Regulation of sleep-wake cycles• Control of the endocrine system• Formation of memory
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Nuclei of the Hypothalamus
Figure 13.18
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The Diencephalon – The Epithalamus
• Forms part of the “roof” of the third ventricle
• Consists of a tiny group of nuclei
• Includes the pineal gland (pineal body)• Secretes the hormone melatonin
• Under influence of the hypothalamus
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 5
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Brain Stem
• Includes the midbrain, pons, and medulla oblongata
• Several general functions• Produces automatic behaviors necessary for
survival• Passageway for all fiber tracts running between the
cerebrum and spinal cord• Heavily involved with the innervation of the face
and head• 10 of the 12 pairs of cranial nerves attach to it
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Ventral View of the Brain – Diencephalon and Brain Stem
Figure 13.19
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The Brain Stem – The Midbrain
• Lies between the diencephalon and the pons
• Central cavity – the cerebral aqueduct
• Cerebral peduncles located on the ventral surface of the brain• Contain pyramidal (corticospinal) tracts
• Superior cerebellar peduncles• Connect midbrain to the cerebellum
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The Brain Stem and Diencephalon
Figure 13.20a, b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.21a
The Brain Stem – The Midbrain
• Periaqueductal gray matter surrounds the cerebral aqueduct• Involved in two
related functions • Fright-and-flight
reaction
• Mediates response to visceral pain
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The Brain Stem – The Midbrain
• Corpora quadrigemina – the largest nuclei• Divided into the superior and inferior colliculi
• Superior colliculi – nuclei that act in visual reflexes
• Inferior colliculi – nuclei that act in reflexive response to sound
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The Brain Stem – Dorsal View
Figure 13.20c
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The Brain Stem – The Pons
• Located between the midbrain and medulla oblongata
• Contains the nuclei of cranial nerves V, VI, and VII
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The Brain Stem – The Pons
Figure 13.21.b
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The Brain Stem – The Medulla Oblongata
• Most caudal level of the brain stem• Continuous with the spinal cord
• Choroid plexus lies in the roof of the fourth ventricle
• Pyramids of the medulla – lie on its ventral surface • Decussation of the pyramids – crossing over of
motor tracts
• Cranial nerves VIII–XII attach to the medulla
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Brain Stem – The Medulla Oblongata
• The core of the medulla contains:• Much of the reticular formation
• Nuclei influence autonomic functions
• Visceral centers of the reticular formation include:• Cardiac center
• Vasomotor center
• The medullary respiratory center
• Centers for hiccupping, sneezing, swallowing, and coughing
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The Cerebellum
• Located dorsal to the pons and medulla• Smoothes and coordinates body movements
• Helps maintain equilibrium
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The Cerebellum
• Consists of two cerebellar hemispheres
• Surface folded into ridges called folia• Separated by fissures
• Hemispheres each subdivided into:• Anterior lobe
• Posterior lobe
• Flocculonodular lobe
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The Cerebellum
Figure 13.22a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebellum
• Composed of three regions• Cortex – gray matter• Internal white matter• Deep cerebellar nuclei – deeply situated gray
matter
• Cerebellum must receive information • On equilibrium • On current movements of limbs, neck, and trunk• From the cerebral cortex
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebellum – Cerebellar Peduncles
• Thick tracts connecting the cerebellum to the brain stem• Superior cerebellar peduncles
• Middle cerebellar peduncles
• Inferior cerebellar peduncles
• Fibers to and from the cerebellum are ipsilateral• Run to and from the same side of the body
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 6
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Brain Systems
• Networks of neurons functioning together• The limbic system – spread widely in the forebrain
• The reticular formation – spans the brain stem
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Functional Brain Systems – The Limbic System
• Location • Medial aspect of cerebral hemispheres
• Also within the diencephalon
• The fornix and other tracts link the limbic system together
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Functional Brain Systems – The Limbic System
Figure 13.23
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Functional Brain Systems – The Limbic System
• The “emotional brain”• Cingulate gyrus
• Allows us to shift between thoughts
• Interprets pain as unpleasant
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Functional Brain Systems – The Reticular Formation
• Runs through the central core of the medulla, pons, and midbrain
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Functional Brain Systems – The Reticular Formation
Figure 13.21c
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Functional Brain Systems – The Reticular Formation
• Widespread connections • Ideal for arousal of the brain as a whole
• Reticular activating system (RAS) • Maintains consciousness and alertness
• Functions in sleep and arousal from sleep
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Functional Brain Systems – The Reticular Formation
Figure 13.24
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Protection of the Brain
• The brain is protected from injury by• The skull
• Meninges
• Cerebrospinal fluid
• Blood-brain barrier
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Protection of the Brain – Meninges
• Cover and protect the CNS
• Enclose and protect the vessels that supply the CNS
• Contain the cerebrospinal fluid
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Dura Mater
• Strongest of the meninges
• Composed of two layers• Periosteal layer
• Meningeal layer• Two layers are fused except to enclose the dural
sinuses
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The Dura Mater
Figure 13.25a
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The Dura Mater
• Largest sinus – the superior sagittal sinus
• Dura mater extends inward to subdivide the cranial cavity
Figure 13.26
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The Arachnoid Mater
• Located beneath the dura mater
• Subdural space • Potential space between dura and arachnoid mater
• Subarachnoid space• Filled with CSF
• Contains the blood vessels that supply the brain
• Arachnoid villi • Allow CSF to pass into the dural blood sinuses
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Pia Mater
• Delicate connective tissue
• Clings tightly to the surface of the brain• Follows all convolutions of the cortex
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 7
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Protection of the Brain – Cerebrospinal Fluid (CSF)
• Provides a liquid cushion for the brain and spinal cord
• The brain “floats” in CSF
• Formed in choroid plexuses in the brain ventricles
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Protection of the Brain – Cerebrospinal Fluid (CSF)
Figure 13.27a
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Protection of the Brain – Cerebrospinal Fluid (CSF)
Figure 13.27b
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Protection of the Brain – Blood-Brain Barrier
• Prevents most blood-borne toxins from entering the brain• Impermeable capillaries
• Not an absolute barrier• Nutrients such as oxygen pass through
• Allows alcohol, nicotine, and anesthetics through
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The Spinal Cord
• Runs through the vertebral canal
• Extends from the foramen magnum to the level of the vertebra L1 or L2
• Protected by bone, meninges, and CSF
• Dura mater of the spinal cord
• The spinal dural sheath – only one layer
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The Spinal Cord
• Conus medullaris – the inferior end of the spinal cord
• Filum terminale – long filament of connective tissue• Attaches to the coccyx inferiorly
• Cervical and lumbar enlargements • Where nerves for upper and lower limbs arise
• Cauda equina – collection of nerve roots
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The Spinal Cord
Figure 13.29a
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The Spinal Cord
• Denticulate ligaments – anchor spinal cord to vertebrae
• Two deep grooves run the length of the cord• Posterior median sulcus
• Anterior median fissure
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Anatomy of the Spinal Cord
Figure 13.30a
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Anatomy of the Spinal Cord
Figure 13.30b
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Gray Matter of the Spinal Cord and Spinal Roots
• Shaped like the letter H
• Gray commissure – contains the central canal
• Anterior horns – contain cell bodies of motor neurons
• Posterior horns – consist of interneurons
• Gray matter – divided according to somatic and visceral regions
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Gray Matter of the Spinal Cord and Spinal Roots
Figure 13.32
HUMAN ANATOMYfourth edition
MARIEB | MALLATT | WILHELM
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
13
The CentralNervous System
PART 8
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
White Matter of the Spinal Cord
• Composed of myelinated and unmyelinated axons
• Three types of fibers• Ascending
• Descending
• Commissural
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White Matter of the Spinal Cord
Figure 13.33
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory and Motor Pathways
• Most motor pathways:• Decussate at some point along their course
• Consist of a chain of two or three neurons
• Exhibit somatotopy• Tracts arranged according to the body region they
supply
• All pathways are paired• One of each on each side of the body
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Ascending (Sensory) Pathways
• Conduct general somatic sensory impulses
• Chains of neurons composed of:• First-, second-, and third-order neurons
• Four main ascending pathways• Dorsal column pathway
• Spinothalamic pathway
• Posterior spinocerebellar pathway
• Anterior spinocerebellar pathway
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Ascending Pathways
Figure 13.34a
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Ascending Pathways
Figure 13.34b
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Descending (Motor) Pathways
• Deliver motor instructions from the brain to the spinal cord
• Divided into two groups• Pyramidal, or corticospinal, tracts• Other motor pathways
• Tectospinal tracts• Vestibulospinal tract• Rubrospinal tract• Reticulospinal tract
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Descending Motor Pathways
Figure 13.35a
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Descending Motor Pathways
Figure 13.35b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Disorders of the Central Nervous System
• Brain dysfunction• Traumatic brain injuries
• Concussion – brain injury is slight
• Contusion – marked destruction of brain tissue
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Disorders of the Central Nervous System
• Brain dysfunction (continued)• Degenerative brain diseases
• Cerebrovascular accident (stroke)• Blockage or interruption of blood flow to a brain region
• Alzheimer’s disease • Progressive degenerative disease leading to dementias
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Disorders of the Central Nervous System
• Spinal cord damage• Paralysis – loss of motor function
• Parasthesia – loss of sensation
• Paraplegia – injury to the spinal cord is between T1 and L2
• Paralysis of the lower limbs
• Quadriplegia – injury to the spinal cord in the cervical region• Paralysis of all four limbs
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The Central Nervous System Throughout Life
• Congenital malformations • Hydrocephalus
• Neural tube defects• Anencephaly – cerebrum and cerebellum are absent
• Spina bifida – absence of vertebral lamina
• Cerebral palsy – voluntary muscles are poorly controlled • Results from damage to the motor cortex