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Transcript
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 1
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.2a-e
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.3a-d
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.4
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.5
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.6a, b
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 2
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.7a
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebral Hemispheres
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.7b, c
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.8
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.11a
Functional and Structural Areas of the Cerebral Cortex
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.11b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.10
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 3
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.10
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral White Matter
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.13a
Cerebral White Matter
•
Types of tracts (continued)
• Projection fibers – run vertically
• Descend from the cerebral cortex
• Ascend to the cortex from lower regions
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral White Matter
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.13b
Projection Tracts
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.14a
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 4
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.15
The Diencephalon
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.16a
The Diencephalon
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.16b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.17b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.18
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 5
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ventral View of the Brain – Diencephalon and Brain Stem
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.19
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Brain Stem and Diencephalon
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.20a, b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.21a
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Brain Stem – Dorsal View
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.20c
The Brain Stem – The Pons
•
•
Located between the midbrain and medulla
oblongata
Contains the nuclei of cranial nerves V, VI,
and VII
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Brain Stem – The Pons
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.21.b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebellum
•
Located dorsal to the pons and medulla
• Smoothes and coordinates body movements
• Helps maintain equilibrium
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Cerebellum
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.22a
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 6
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Brain Systems – The Limbic System
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.23
Functional Brain Systems – The Limbic System
•
The “emotional brain”
• Cingulate gyrus
• Allows us to shift between thoughts
• Interprets pain as unpleasant
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Brain Systems – The Reticular Formation
•
Runs through the central core of the medulla,
pons, and midbrain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Brain Systems – The Reticular Formation
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.21c
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Brain Systems – The Reticular Formation
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.24
Protection of the Brain
•
The brain is protected from injury by
•
•
•
•
The skull
Meninges
Cerebrospinal fluid
Blood-brain barrier
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Dura Mater
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.25a
The Dura Mater
•
•
Largest sinus – the
superior sagittal sinus
Dura mater extends
inward to subdivide the
cranial cavity
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.26
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 7
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Protection of the Brain – Cerebrospinal Fluid (CSF)
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.27a
Protection of the Brain – Cerebrospinal Fluid (CSF)
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.27b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
The Spinal Cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.29a
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Spinal Cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.30a
Anatomy of the Spinal Cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.30b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.32
13
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
The Central
Nervous System
PART 8
HUMAN ANATOMY
fourth edition
MARIEB | MALLATT | WILHELM
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
White Matter of the Spinal Cord
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.33
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Ascending Pathways
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.34a
Ascending Pathways
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.34b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Descending Motor Pathways
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.35a
Descending Motor Pathways
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Figure 13.35b
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings