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prepared by
Betsy C. Brantley
Valencia College
CHAPTER
7
The Central
Nervous
System
© 2013 Pearson Education, Inc.
Chapter 7 Learning Outcomes
• Section 1: Neurons and Neuroglia
• 7.1
• Sketch, label, and describe the structures of a typical neuron,
and classify and describe neurons on the basis of their structure
and function.
• 7.2
• Identify the types of neuroglia in the CNS and describe their
locations and functions.
• 7.3
• Describe the locations and functions of Schwann cells and
satellite cells of the PNS and classify and describe the three
functional classes of neurons.
© 2013 Pearson Education, Inc.
Chapter 7 Learning Outcomes
• 7.4
• Describe the membrane potential and summarize its role in
neural activity.
• 7.5
• Compare continuous propagation and saltatory propagation,
and discuss the factors that affect the speed of action potential
propagation.
• 7.6
• Describe the general structure of a synapse and summarize the
events that occur when an action potential arrives at an axon
terminal.
© 2013 Pearson Education, Inc.
Chapter 7 Learning Outcomes
• Section 2: The Functional Anatomy of the Central Nervous System
• 7.7
• Name and locate the major regions of the brain, and describe
their functions.
• 7.8
• Describe the cranial meninges and explain how cerebrospinal
fluid forms and circulates.
• 7.9
• Name and locate the major superficial landmarks of the
cerebrum.
• 7.10
• Locate the motor, sensory, and association areas of the
cerebral cortex, and discuss the functions of each.
© 2013 Pearson Education, Inc.
Chapter 7 Learning Outcomes
• 7.11
• Explain the structure and functions of the diencephalon, brain
stem, and cerebellum.
• 7.12
• Describe the reticular formation and explain the functions of the
reticular activating system.
• 7.13
• CLINICAL MODULE Describe how brain waves are monitored,
and explain the normal and clinical significance of various brain
waves seen on an electroencephalogram.
• 7.14
• Discuss the anatomical features of the spinal cord.
© 2013 Pearson Education, Inc.
Chapter 7 Learning Outcomes
• 7.15
• Explain the roles of gray matter and white matter in processing
and relaying sensory information and motor commands.
• 7.16
• Describe the spinal meninges.
© 2013 Pearson Education, Inc.
Nervous System Organization (Section 1)
• Central Nervous System (CNS)
• Brain and spinal cord
• Integrates, processes, and coordinates sensory data
and motor commands
• Peripheral Nervous System (PNS)
• All neural tissue outside CNS
• Sensory (afferent) division
• Motor (efferent) division
© 2013 Pearson Education, Inc.
Sensory Division of the PNS (Section 1)
• Brings information to CNS from receptors
• Somatic sensory receptors
• Provide sensation of touch, position, pressure, pain,
temperature
• Visceral sensory receptors
• Monitor internal organs
• Special sensory receptors
• Provide sensations of smell, taste, vision, balance,
hearing
© 2013 Pearson Education, Inc.
Motor Division of the PNS (Section 1)
• Carries motor commands from CNS to target organs called
effectors
• Somatic nervous system (SNS)
• Carries messages to skeletal muscle
• Autonomic nervous system (ANS)
• Carries messages to:
• Smooth muscle
• Cardiac muscle
• Glands
• Adipose tissue
© 2013 Pearson Education, Inc.
Major components and functions of the nervous system
Central Nervous System
3
Information
processing
Peripheral Nervous
System
4
Motor (efferent) division
includes
2
Sensory (afferent) division
Somatic
sensory
receptors
Special
sensory
receptors
Somatic
nervous
system
Autonomic
nervous
system
Skeletal
muscle
Visceral sensory
receptors
Start 1 Receptors
© 2013 Pearson Education, Inc.
5 Effectors
• Smooth
muscle
• Cardiac
muscle
• Glands
• Adipose
tissue
Figure 7 Section 1 1
Structural Features of Neurons (7.1)
• Dendrites
• Receive stimuli from environment or other neurons
• Short and highly branched
• Cell body
• Contains nucleus and other organelles
• Cytoskeleton contains filaments that extend into
dendrites and axon
• Axon
• Carries information away from cell body toward other
cells
© 2013 Pearson Education, Inc.
Axon Details (7.1)
• Axon hillock
• Expanded section adjacent to cell body where axon
begins
• Axon collaterals or branches
• Axon terminal
• End of axon adjacent to synapse
• Synapse where neuron communicates with another cell
• Presynaptic cell and postsynaptic cell on either side
• Transport of materials through neurotubules
© 2013 Pearson Education, Inc.
Structural features of neurons
Axon
Dendrites
Axon hillock
Axon collaterals
Axon terminal
Nissl bodies
Mitochondrion
Nucleus
Axon terminal
Presynaptic cell
Nucleolus
Synapse
Postsynaptic
cell
Cell Body
Cytoplasm
(contains organelles)
© 2013 Pearson Education, Inc.
Cytoskeleton
(contains filaments)
Figure 7.1 11
Structural Variations among Neurons (7.1)
• Bipolar neurons
• Have two processes (dendritic process and axon)
• Found in special sense organs between receptors and other
neurons
• Unipolar neurons
• Fused dendrite and axon
• Most sensory neurons are unipolar
• Multipolar neurons
• Two or more dendrites and single axon
• Most common neurons in CNS and all motor neurons
controlling skeletal muscles
© 2013 Pearson Education, Inc.
Structural variations among neurons
Dendrites
Dendritic
process
Bipolar neuron
Dendrites
Initial
segment
Axon
Cell body
Axon
Axon
Axon
terminals
Dendrites
Multipolar
neuron
Axon
terminals
Axon
Axon
terminals
© 2013 Pearson Education, Inc.
Unipolar neuron
Figure 7.1 22- 4– 4
Neural Stem Cells (7.1)
• Exist in adult nervous system, but inactive except
in:
• Olfactory epithelium (sensory neurons for smell)
• Retina of eye
• Hippocampus (part of brain involved in short-term
memory storage)
• Most CNS neurons cannot divide or be replaced
after injury or disease
© 2013 Pearson Education, Inc.
Module 7.1 Review
a. Name the structural components of a typical
neuron.
b. Classify neurons according to their structure.
c. Why is a CNS neuron not usually replaced after it
is injured?
© 2013 Pearson Education, Inc.
Neuroglia of the CNS (7.2)
•
Cells that support and protect neurons are called
neuroglia or glial cells
•
Account for half the volume of the nervous
system
•
Four types in CNS
1. Astrocytes
2. Ependymal cells
3. Microglia
4. Oligodendrocytes
© 2013 Pearson Education, Inc.
Neuroglia of the CNS Details (7.2)
• Ependymal cells
• Form ependyma, epithelium lining fluid-filled
passageways in spinal cord and brain
• Produce, monitor, and circulate cerebrospinal fluid
(CSF)
• Microglia
• Related to monocytes and macrophages
• Mobile cells roaming through neural tissue
• Remove cellular debris, waste products, and pathogens
© 2013 Pearson Education, Inc.
Neuroglia of the CNS Details (7.2)
• Astrocytes
• Maintain blood–brain barrier
• Provide structural support and regulate ion, nutrient,
and dissolved gas concentrations in interstitial fluid
• Absorb and recycle neurotransmitters
• Form scar tissue
• Oligodendrocytes
• Produce myelin
© 2013 Pearson Education, Inc.
Myelination in CNS (7.2)
• Oligodendrocyte process winds around axon forming
concentric layers of lipid-rich material called myelin
sheath
• Myelinated axons have myelin sheath
• Sections of axon wrapped called internodes
• Gaps between internodes called nodes
• Regions in CNS with myelinated axons are white matter
• Unmyelinated axons not completely covered by myelin
• Regions of CNS with cell bodies and unmyelinated axons are
gray matter
© 2013 Pearson Education, Inc.
Neuroglia of the central nervous system
Astrocytes
Oligodendrocytes
Internode of
myelinated
axon
Capillary
Section of
spinal cord
Ependymal cells
Nodes
between
internodes
Unmyelinated
axon
Microglia
Neurons
Gray
matter
© 2013 Pearson Education, Inc.
Myelinated
axons
Myelin
(cut) Nodes
White matter
Figure 7.2
Module 7.2 Review
a. Identify the neuroglia of the central nervous
system.
b. Which glial cell protects the CNS from chemicals
and hormones circulating in the blood?
c. Which type of neuroglia would occur in increased
numbers in the brain tissue of a person with a
CNS infection?
© 2013 Pearson Education, Inc.
Schwann Cells and Satellite Cells (7.3)
• In the PNS, the myelin sheath is formed by
Schwann cells
• Outer surface of Schwann cell is neurilemma
• Single Schwann cell forms myelin sheath around one
internode of one myelinated axon
• Schwann cell can enclose parts of unmyelinated axons
stabilizing axon position and isolating axon from
interstitial fluid
• Satellite cells surround cell bodies in PNS
• Clusters of cell bodies called ganglia
© 2013 Pearson Education, Inc.
Schwann cells and peripheral axons
Nucleus
Axon hillock
Internode
(myelinated)
Satellite cells
Cell body
Dendrite
Node
Schwann
cell nucleus
Schwann
Axon
cell
Neurilemma
Neurilemma
Schwann cell
Schwann
cell nucleus
Neurilemma
Axons
Schwann
cell #1
Schwann
cell #2
Myelin
covering
internode
Axon
Schwann
cell #3 nucleus
Axons
© 2013 Pearson Education, Inc.
Figure 7.3 11- 3– 3
Three Functional Classes of Neurons (7.3)
1. Sensory neurons
•
About 10 million
2. Interneurons
•
About 20 billion
3. Motor neurons
•
About half a million
© 2013 Pearson Education, Inc.
Sensory Neurons (7.3)
• Unipolar neurons
• Cell bodies in sensory ganglia
• Deliver information from receptors to CNS along
afferent fibers
• Somatic sensory neurons
• External receptors detect changes in external
environment
• Proprioceptors monitor body position and movement
• Visceral sensory neurons
• Internal receptors monitor internal conditions
© 2013 Pearson Education, Inc.
Interneurons (7.3)
• Receive sensory information from PNS and from
other interneurons in CNS
• Responsible for memory, planning, and learning
© 2013 Pearson Education, Inc.
Motor Neurons (7.3)
• Carry information from CNS to effectors along efferent
fibers
• Somatic motor neurons
• Innervate skeletal muscle under voluntary control
• Cell bodies in CNS
• Axon within peripheral nerve to somatic effectors
• Visceral motor neurons
• Innervate smooth muscle, glands, cardiac muscle, adipose
tissue
• Communicate with second visceral motor neuron in
peripheral autonomic ganglia
© 2013 Pearson Education, Inc.
Functional classes of neurons
Central Nervous System (CNS)
Interneurons
Visceral motor
neurons
Somatic motor neurons
cell bodies
Peripheral Nervous System
(PNS)
Autonomic ganglia
Sensory ganglia
Afferent fibers
Efferent fibers
Somatic effectors
Skeletal
muscle
fibers
Internal
receptors
Proprioceptors
Start Sensory receptors
© 2013 Pearson Education, Inc.
External
receptors
KEY
= Somatic
(sensory & motor)
= Visceral
(sensory & motor)
Visceral effectors
Smooth
muscles
Glands
Cardiac
muscle
Adipose
tissue
Figure 7.3 44
Module 7.3 Review
a. Compare Schwann cells and satellite cells.
b. Describe the neurilemma.
c. Classify neurons into three categories according
to their function.
© 2013 Pearson Education, Inc.
Membrane Potential (7.4)
• Cytosol and extracellular fluid different
composition
• Slightly more positive ions outside cell
• Slightly more negative ions inside cell
• Unequal distribution of charge called membrane
potential
• Results from:
• Different permeability of membrane to various ions
• Active transport processes
© 2013 Pearson Education, Inc.
Membrane potential of a cell
–
+
+
–
+
–
+
+
+
Extracellular fluid –
–
+
+
–
–
+
+
–
+ + + + + + + + + + + + + + + + + + + + +
Plasma membrane
– – – – – – – – – – – – – – – – – – – – –
–
+
+
Cytosol
–
–
– –
–
–
Protein
–
–
Protein
–
–
+
+
Protein
–
+
–
–
–
–
–
+
–
+
–
© 2013 Pearson Education, Inc.
Figure 7.4 11
Ion Concentrations (7.4)
• Extracellular fluid (ECF) has high concentrations
of:
• Sodium (Na+)
• Chloride (Cl–)
• Cytosol has high concentrations of:
• Potassium (K+)
• Negatively charged proteins (Pr –)
© 2013 Pearson Education, Inc.
Ion Movements (7.4)
• Ions can enter or leave cell only through:
• Membrane channels
• Some sodium and potassium channels always open
• Some channels open in response to specific neurotransmitters
• Some channels open or close in response to membrane
potential changes
• Active transport
• Sodium–potassium exchange pump
• Ejects 3 Na+ ions from cell; reclaims 2 K+ ions
© 2013 Pearson Education, Inc.
Ion channels and the membrane potential
Potassium
channel
Sodium
channel
ECF
Plasma
membrane
Sodium–
potassium
exchange
pump
Cytosol
© 2013 Pearson Education, Inc.
Figure 7.4 22
Neural Activity (7.4)
• Changes in membrane potential may:
• Trigger muscle contraction
• Trigger gland secretion
• Transfer information in nervous system
© 2013 Pearson Education, Inc.
Changes in Potential (7.4)
• Resting cell membrane potential is resting
potential
• Stimulus produces localized change called graded
potential
• If graded potential large enough, triggers action
potential
• Action potential propagates (spreads) along axon
toward terminal
© 2013 Pearson Education, Inc.
At the Synapse (7.4)
• Synapse activity involves:
• Presynaptic cell releasing neurotransmitters
• Neurotransmitters binding to receptors on postsynaptic
cell, changing membrane permeability
• Thousands of axon terminals communicate with
neuron cell body
• Some neurotransmitters stimulate neuron
• Some neurotransmitters inhibit neuron
• Net effect determines if new action potential develops
© 2013 Pearson Education, Inc.
Role of the membrane potential in neural activity
1
2
4
3
3
Graded
potential
Resting stimulus
potential produces
may
produce
5
Action potential
triggers
Information
processing
Presynaptic neuron
© 2013 Pearson Education, Inc.
Postsynaptic cell
Figure 7.4 33
Module 7.4 Review
a. Define membrane potential.
b. What happens at the sodium–potassium
exchange pump?
c. List three body functions that result from changes
in the membrane potential of a cell.
© 2013 Pearson Education, Inc.
Phases of an Action Potential (7.5)
• Unequal distribution of charge across membrane called
polarization
• Depolarization
• Neurotransmitter, like ACh, opens sodium channels
• Positive sodium ion rushes into cell, making membrane potential
less negative or less polarized
• Repolarization
• Sodium channels closed; potassium channels open
• Positive potassium leaves the cell, making membrane potential
more negative or more polarized
© 2013 Pearson Education, Inc.
Changes in membrane potential with stimuli
Less polarized
Repolarization
Resting
membrane
potential (mV)
Resting potential
Depolarization
More polarized
Time
© 2013 Pearson Education, Inc.
Figure 7.5 11
Development of an Action Potential (7.5)
•
Graded potential depolarizes membrane
•
If depolarization reaches threshold potential, then action
potential is triggered
•
Three steps involved
1. Neurotransmitter release on cell body opens sodium
channels, causing large depolarization
2. Sodium channels then close and potassium channels open,
causing repolarization
3. Sodium–potassium exchange pump resets original ion
distribution
© 2013 Pearson Education, Inc.
Development of an action potential
2
1
Sodium channels
open.
© 2013 Pearson Education, Inc.
3
Sodium channels
close. Potassium
channels open.
Sodium-potassium
exchange pump
ejects sodium ions
and recaptures
potassium ions.
Figure 7.5 22
Propagation of an Action Potential (7.5)
• Continuous propagation
• Action potential at one location on axon triggers action
potential at adjacent portion of membrane
• Like closely spaced dominos falling
• Saltatory propagation
• Occurs in myelinated axons where membranes exposed only
at nodes
• Action potentials develop only at nodes
• Much faster process, like dominos spaced farther apart
© 2013 Pearson Education, Inc.
Continuous and saltatory propagation of an action potential
An action potential here at time 0
triggers an action potential here at time 1
which triggers an action potential here at time 2
which triggers an action potential here at time 3
and so on along the axon, in a series of tiny steps.
Continuous propagation
An action potential here at time 0
triggers an action potential here at time 1
which triggers an action potential here at time 2
which triggers an action potential here at time 3
and so on along the axon, skipping the
segments in between.
Saltatory propagation
© 2013 Pearson Education, Inc.
Figure 7.5 33- 4– 4
Speed of Action Potential Propagation (7.5)
• Propagation speed fastest along:
• Large-diameter axons
• Myelinated axons
• Urgent information carried along large-diameter,
myelinated axons
• Threats to survival or motor commands to prevent injury
• Less urgent information carried on unmyelinated
fibers
© 2013 Pearson Education, Inc.
Module 7.5 Review
a. Describe depolarization and repolarization.
b. Compare continuous and saltatory propagation.
c. What is the relationship between myelin and the
propagation speed of action potentials?
© 2013 Pearson Education, Inc.
Synapse (7.6)
• Action potentials (nerve impulses) propagate along axon
• Transfer of action potential from one neuron to another
neuron or effector occurs at synapse
• Presynaptic cell axon forms axon terminal
• Contains neurotransmitters packaged in synaptic vesicles
• Narrow space between presynaptic membrane and
postsynaptic membrane is synaptic cleft
PLAY
Neurophysiology: Synapse
© 2013 Pearson Education, Inc.
Structures at a synapse
Axon of presynaptic cell
REPRESENTATIVE SYNAPSE
Mitochondrion
Axon terminal
Presynaptic
membrane
Synaptic vesicles
containing
neurotransmitters
Synaptic cleft
Cytoplasm of
postsynaptic cell
© 2013 Pearson Education, Inc.
Postsynaptic
membrane
Figure 7.6 11
Events at an ACh-releasing synapse
Step 1
An action potential
arrives and depolarizes
the synaptic terminal.
Presynaptic
neuron
Synaptic
vesicles
Action
potential
EXTRACELLULAR
FLUID
Axon
terminal
AChE
POSTSYNAPTIC
NEURON
Step 2
Extracellular Ca2+
enters the synaptic
terminal, triggering the
exocytosis of ACh.
ACh
Synaptic
cleft
Chemically regulated
sodium ion channels
Step 3
ACh binds to receptors
and depolarizes the
postsynaptic
membrane.
Step 4
ACh is removed by
AChE.
© 2013 Pearson Education, Inc.
Initiation of
action potential
if threshold is
reached
Propagation of
action potential
(if generated)
Figure 7.6 33
Neurotransmitters (7.6)
• Over 100 different neurotransmitters exist
• All work in different ways
• Acetylcholine (ACh) found at neuromuscular
junctions
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Figure 7.6 22
Module 7.6 Review
a. Describe the structure of a synapse.
b. Describe the events that occur at a synapse
when an action potential arrives at the axon
terminal.
c. Why is the depolarization on the postsynaptic cell
temporary?
© 2013 Pearson Education, Inc.
Functional Anatomy of the CNS (Section 2)
• Central nervous system consists of:
• Spinal cord
• Brain
• Contains 97 percent of body's neural tissue
• Weighs about 1.4 kg (3 lb) with 1200 mL volume
• Male brain about 10 percent larger than female (due to
differences in average body size)
• No correlation between brain size and intelligence
© 2013 Pearson Education, Inc.
Development of Nervous System (Section 2)
• Starts as neural tube
• At 4 weeks development, consists of:
• Hindbrain
• Continuous with spinal cord
• Midbrain
• Expanded area next to forebrain
• Forebrain
• Tip of neural tube
© 2013 Pearson Education, Inc.
Lateral view of embryonic neural tube at four weeks
The hindbrain is continuous with the spinal
cord.
The midbrain is an expansion next to the forebrain.
The forebrain is at the tip
of the neural tube.
© 2013 Pearson Education, Inc.
Spinal
cord
Figure 7 Section 2 1 1
Development of the Brain at Five Weeks
(Section 2)
• Forebrain divided into:
• Diencephalon, major relay and processing center
• Cerebrum
• Midbrain
• Hindbrain
• Region close to midbrain will become cerebellum and
pons
• Region close to spinal cord will become medulla
oblongata
© 2013 Pearson Education, Inc.
Brain development at five weeks
Hindbrain
Forebrain
Cerebellum and
pons
Medulla
oblongata
Diencephalon
Cerebrum
Spinal
cord
© 2013 Pearson Education, Inc.
Figure 7 Section 2 2 2
Regions of the Brain – Cerebrum (7.7)
• Divided into two cerebral hemispheres
• Superficial layer of gray matter called cerebral cortex
• Functions
• Conscious thought
• Memory storage and processing
• Sensory processing
• Regulation of skeletal muscle contractions
• Surface features
• Fissures (deep grooves)
• Gyri (folds)
• Sulci (shallow depressions)
© 2013 Pearson Education, Inc.
Regions of the Brain (7.7)
• Cerebellum
• Second-largest structure in brain
• Coordinates and modulates motor commands from
cerebral cortex
• Diencephalon
• Thalamus
• Relay and processing center for sensory information
• Hypothalamus
• Centers for emotions, autonomic functions, hormone
production
© 2013 Pearson Education, Inc.
Regions of the Brain – Brain Stem (7.7)
•
Consists of three parts
1. Midbrain
•
Processes visual and auditory information
•
Helps maintain consciousness
2. Pons
•
Connects cerebellum to brain stem
•
Functions in somatic and visceral motor control
3. Medulla oblongata
•
Relays sensory information to brain stem and thalamus
•
Autonomic regulation centers for heart rate and blood
pressure
© 2013 Pearson Education, Inc.
Major regions of the brain
Cerebrum
Fissures
Gyri
Diencephalon
Thalamus
Hypothalamus
Brain stem
Midbrain
© 2013 Pearson Education, Inc.
Sulci
Spinal
cord
Cerebellum
Pons
Medulla oblongata
Figure 7.7 11
Ventricles of the Brain (7.7)
• Passageways within neural tube expand to form chambers
called ventricles
• Filled with cerebrospinal fluid
• Lined with ependymal cells
• Two large lateral ventricles in cerebrum
• Interventricular foramen connects lateral ventricles to
third ventricle in diencephalon
• Cerebral aqueduct connects third ventricle to fourth
ventricle in pons
• Fourth ventricle continuous with central canal of spinal cord
© 2013 Pearson Education, Inc.
Ventricles of the brain
Ventricles of
the Brain
Cerebral
hemispheres
Cerebral
Longitudinal
hemispheres
fissure
Lateral ventricle
Interventricular
foramen
Third ventricle
Cerebral aqueduct
Fourth ventricle
Pons
Medulla oblongata
Spinal cord
Central canal
Ventricular system, lateral view
© 2013 Pearson Education, Inc.
Central canal
Cerebellum
Ventricular system, anterior view
Figure 7.7 22
Connections and Nuclei (7.7)
• Corpus callosum
• Thick tract of white matter connecting two cerebral
hemispheres
• Carries about 4 billion impulses per second
• Nuclei
• Groups of nerve cell bodies in CNS
• Basal nuclei in each cerebral hemisphere
• Subconscious control of muscle tone
• Help direct movements like walking and running
© 2013 Pearson Education, Inc.
Interconnections between ventricles
Corpus
callosum
Lateral ventricles
Interventricular
foramen
Third ventricle
Basal nuclei
Cerebral
aqueduct
Fourth ventricle
Cerebellum
Central canal
© 2013 Pearson Education, Inc.
Figure 7.7 33
Module 7.7 Review
a. Name the major regions of the brain and the
distinct structures of each.
b. Describe the role of the medulla oblongata.
c. Which ventricles would lose communication by a
blocked cerebral aqueduct?
© 2013 Pearson Education, Inc.
Cranial Meninges (7.8)
• Dura mater
• Outer and inner fibrous layers with small gap between
• Dural sinuses, collecting venous blood, found in gap
• Outer layer fused to periosteum (no epidural space)
• Arachnoid mater
• Outer epithelial layer supported by fibrous meshwork
• Subarachnoid space separates outer layer from pia mater
• Pia mater
• Thin, delicate membrane that follows contours of brain
© 2013 Pearson Education, Inc.
Cranial meninges
Subdural space
Cranium
(skull)
1
2
Arachnoid mater
Dura mater
Dura mater
(outer layer)
Dural sinus
Arachnoid mater
Subarachnoid space
Dura mater
(inner layer)
3
Pia mater
Cerebral
cortex
© 2013 Pearson Education, Inc.
Figure 7.8 11
Dural Folds (7.8)
• Inner layer of dura mater extends into cranial cavity at
points forming dural folds
• Dural sinuses are collecting veins within dural folds
• Falx cerebri
• Dural fold between cerebral hemispheres
• Contains inferior sagittal sinus and superior sagittal sinus
• Tentorium cerebelli
• Separates cerebral hemispheres from cerebellum
• Falx cerebelli
• Separates two cerebellar hemispheres
© 2013 Pearson Education, Inc.
Dural folds
Superior sagittal
sinus
Tentorium
cerebelli
Falx cerebri
Falx cerebelli
© 2013 Pearson Education, Inc.
Figure 7.8 22
Cerebrospinal Fluid (7.8)
• Surrounds and bathes exposed surfaces of CNS
• Produced by choroid plexus at rate of 500 mL/day
• Choroid plexus is combination of specialized ependymal cells
and capillaries
• Flows from choroid plexus through ventricles and from
fourth ventricle through lateral and median apertures into
subarachnoid space and central canal
• Absorbed into venous blood at arachnoid granulations
• Total CSF volume 150 mL
© 2013 Pearson Education, Inc.
Cerebrospinal fluid production and absorption
Nutrients,
O2
Interstitial fluid
in thalamus
Capillaries
Waste
products, CO2
Neuron
Astrocyte
Choroid plexus
Ependymal cells
cells
Remove
wastes
Produce
CSF
Superior sagittal sinus
Cerebrospinal
fluid in
third ventricle
Choroid plexus
Dura mater
Superior Cranium
sagittal sinus
Arachnoid
granulation
CSF
movement
Third ventricle
Cerebral aqueduct
Cerebral
cortex
Subdural
space
Arachnoid
membrane
Pia mater
Median and lateral
apertures
Central canal
of spinal cord
Cerebrospinal
fluid in central
canal and
subarachnoid
space
Dura mater
Arachnoid mater
Subarachnoid space
Pia mater
© 2013 Pearson Education, Inc.
Figure 7.8 33- 4– 4
Choroid plexus details
Interstitial fluid
in thalamus
Nutrients,
O2
Capillaries
Waste products,
CO2
Neuron
Astrocyte
Choroid plexus
Ependymal cells
cells
Remove
wastes
Produce
CSF
Choroid plexus
© 2013 Pearson Education, Inc.
Cerebrospinal
fluid in
third ventricle
Figure 7.8 33
Choroid plexus details
Dura mater Superior
Cranium
sagittal sinus
Arachnoid
granulation
CSF
movement
Subdural
space
Cerebral
cortex
© 2013 Pearson Education, Inc.
Arachnoid
membrane
Pia mater
Figure 7.8 44
Module 7.8 Review
a. From superficial to deep, name the three layers
that make up the cranial meninges.
b. Beginning at the choroid plexus, trace the flow of
CSF.
c. How would decreased diffusion across the
arachnoid granulations affect the volume of
cerebrospinal fluid in the ventricles?
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Lobes of the Cerebral Cortex (7.9)
• Each cerebral hemisphere divided into regions
called lobes
• Surface lobes named after overlying bones
• Frontal lobe
• Parietal lobe
• Temporal lobe
• Occipital lobe
• Fifth lobe, insula, medial to lateral sulcus
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Superficial Landmarks between Lobes (7.9)
• Lateral sulcus
• Separates frontal lobe from temporal lobe
• Central sulcus
• Separates frontal lobe from parietal lobe
• Precentral gyrus is anterior to central sulcus
• Contains primary motor cortex
• Postcentral gyrus is posterior to central sulcus
• Contains primary sensory cortex
• Parieto-occipital sulcus
• Separates parietal lobe from occipital lobe
© 2013 Pearson Education, Inc.
Superficial landmarks of the cerebral cortex
Central sulcus
Precentral gyrus
Frontal lobe
Postcentral gyrus
Parietal lobe
Lateral
sulcus
Occipital lobe
Temporal lobe
Cerebellum
Pons
Medulla oblongata
Insula
Lateral view of brain
© 2013 Pearson Education, Inc.
Figure 7.9 11- 2– 2
Midsagittal view of the cerebrum with photo
Precentral gyrus
Central sulcus
Postcentral gyrus
Limbic lobe
Parietal lobe
Frontal lobe
Corpus callosum
Parieto-occipital
sulcus
Occipital lobe
Pineal gland
Thalamus
Hypothalamus
Optic chiasm
Pituitary gland
Temporal lobe
Pons
Cerebral aqueduct
Fourth ventricle
Cerebellum
Medulla oblongata
Midsagittal section
© 2013 Pearson Education, Inc.
Figure 7.9 33
Cerebral Hemisphere Facts (7.9)
• Crossing over
• Sensory information from one side of body ends up on
opposite side of brain
• Motor commands from one side of brain go to opposite
side of body
• Occurs in brain stem and spinal cord
• Similar functions, but also important differences
between hemispheres
© 2013 Pearson Education, Inc.
Module 7.9 Review
a. Identify the lobes of the cerebrum and indicate
the basis for their names.
b. Describe the insula.
c. What effect would damage to the left postcentral
gyrus produce?
© 2013 Pearson Education, Inc.
Cerebral Regions with Specific Functions (7.10)
• Primary areas and association areas
• Association areas interpret incoming data or
coordinate motor response
• Primary motor cortex
• Sends voluntary commands to skeletal muscle
• Neurons here called pyramidal cells (look like
pyramids)
• Somatic motor association area
• Coordinates learned movements
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Sensory Cortex (7.10)
• Primary sensory cortex
• Receives general somatic sensory information
• Processes sense of touch, pressure, pain, vibration,
taste, and temperature
• Somatic sensory association area
• Monitors primary sensory cortex activity
• Allows recognition of light touch
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Special Senses Cortex (7.10)
• Primary visual cortex
• Receives visual information from thalamus
• Visual association area monitors visual cortex and interprets
data
• Gustatory cortex
• Receives information from taste receptors
• Olfactory cortex
• Receives information from smell receptors
• Primary auditory cortex
• Receives sound information
• Auditory association area monitors auditory cortex and
recognizes sounds
© 2013 Pearson Education, Inc.
Regions of the cerebral lobes with specific functions
Motor Cortex
Sensory Cortex
Primary motor
cortex
Primary sensory cortex
Central sulcus
Somatic motor
association area
PARIETAL LOBE
Gustatory cortex
OCCIPITAL
LOBE
FRONTAL
LOBE
Visual Cortex
Olfactory cortex
Auditory Cortex
Primary auditory cortex
Somatic sensory
association area
Primary visual cortex
Lateral sulcus
Visual association area
TEMPORAL LOBE
Auditory association area
© 2013 Pearson Education, Inc.
Figure 7.10 11
Integrative Centers (7.10)
• Perform complex processes and are restricted to either left or
right cerebral hemisphere
• Speech center or Broca area or motor speech area
• Regulates pattern of breathing and vocalization for speech
• Prefrontal cortex
• Used in abstract intellectual functions (predicting consequences of
an action)
• Frontal eye field
• Controls learned eye movements like scanning text
• General interpretive area
• Usually in left hemisphere
• Integrates sensory information and coordinates visual and auditory
memories
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Integrative centers of the cerebrum
Frontal eye field
Speech center (Broca
area or motor speech
area)
Prefrontal cortex
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General interpretive
area
Figure 7.10 22
Hemispheric Lateralization (7.10)
• Left cerebral hemisphere
• General interpretative and speech centers
• Responsible for language-based skills
• Important for analytical tasks like mathematics and logic
• Right cerebral hemisphere
• Analyzes and interprets sensory information
• Enables identification by touch, smell, sight, taste
• Allows recognition of faces and 3-D relationships
• Important for analyzing emotional content of
conversation
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Hemispheric lateralization of the cerebrum
Right Cerebral Hemisphere
Left Cerebral Hemisphere
RIGHT HAND
LEFT HAND
Prefrontal
cortex
Prefrontal
cortex
Speech center
Writing
Auditory cortex
(right ear)
General interpretive center
(language and mathematical
calculation)
Visual cortex
(right visual field)
© 2013 Pearson Education, Inc.
C
O
R
P
U
S
C
A
L
L
O
S
U
M
Anterior
commissure
Analysis by touch
Auditory cortex
(left ear)
Spatial visualization
and analysis
Visual cortex
(left visual field)
Figure 7.10 33
Handedness (7.10)
• Premotor cortex controls hand movements
• Larger in left hemisphere for right-handed people
• About 9 percent of human population left-handed
• High percentage artists and musicians left-handed
• Primary motor cortex and association areas on right
hemisphere near association areas for spatial
visualization and emotions
© 2013 Pearson Education, Inc.
Module 7.10 Review
a. Where is the primary motor cortex located?
b. Which senses are affected by damage to the
temporal lobes?
c. A stroke patient is unable to speak. Which part of
the brain has been affected?
© 2013 Pearson Education, Inc.
Diencephalon (7.11)
• Surrounds third ventricle
• Roof formed by portion of thalamus
• Choroid plexus in anterior portion
• Posterior portion contains pineal gland
• Produces melatonin, helps regulate day–night cycles
• Consists of:
• Thalamus
• Hypothalamus
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Thalamus (7.11)
• Composed of two halves separated by third
ventricle
• Relay point and filter for sensory information
• Sends some information to primary sensory cortex
and rest to subconscious centers in the brain
• Plays role in coordinating voluntary and
involuntary motor commands
© 2013 Pearson Education, Inc.
Hypothalamus (7.11)
•
Contains centers associated with:
1. Subconscious centers involved with rage, pleasure, pain,
sexual arousal as part of limbic system
2. Adjusting autonomic centers in pons and medulla oblongata
3. Coordinating nervous and endocrine system activities
4. Secretion of hormones (ADH, oxytocin)
5. Sensations of hunger and thirst
6. Coordinating voluntary and autonomic functions
7. Regulating normal body temperature
8. Coordinating daily activity cycles
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The diencephalon
Diencephalon
Thalamus
Pineal gland
Hypothalamus
Midbrain
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Figure 7.11
1
Midbrain (7.11)
•
•
Contains two pairs of sensory nuclei called colliculi
•
Superior colliculi control reflexes in response to visual stimuli
•
Inferior colliculi control reflexes in response to auditory stimuli
Also contains:
1. Motor nuclei for oculomotor and trochlear cranial nerves
2. Reticular formation headquarters
3. Nuclei involved in maintaining muscle tone and posture
4. Nucleus that regulates motor output of basal ganglia called
substantia nigra
•
Cerebral peduncles
•
Bundles of nerve fibers linking cerebrum to cerebellum and brain
stem
© 2013 Pearson Education, Inc.
The diencephalon and midbrain
Diencephalon
Thalamus
Pineal gland
Hypothalamus
Midbrain
Substantia nigra
Superior colliculi
Inferior colliculi
Cerebral
peducles
© 2013 Pearson Education, Inc.
Figure 7.11 11- 2– 2
Brain Stem (7.11)
1. Midbrain
•
Processes visual and auditory data
•
Generates automatic motor responses (reflexes)
2. Pons
•
Relays sensory information to cerebellum and thalamus with
cerebellar peduncles
•
Contains subconscious somatic and visceral motor centers
including involuntary control of breathing
•
Includes sensory and motor nuclei for cranial nerves V–VIII
3. Medulla oblongata
© 2013 Pearson Education, Inc.
Medulla Oblongata (7.11)
•
Connects brain with spinal cord, relaying sensory
information to thalamus and other parts of brain stem
•
Includes:
1. Sensory and motor nuclei associated with cranial nerves
VIII–XII
2. Cardiovascular centers adjusting heart rate and strength of
contraction
3. Respiratory rhythmicity centers, which set basic pace for
breathing
© 2013 Pearson Education, Inc.
The brain stem
Brain Stem:
Diencephalon
Thalamus
Midbrain
Pons
Cerebellar peduncles
Medulla oblongata
© 2013 Pearson Education, Inc.
Figure 7.11
3
Cerebellum (7.11)
•
Automatic processing center
•
Coordinates complex somatic motor patterns
1. Adjusts postural muscles to maintain balance
2. Programs and fine-tunes movements
•
Composed of white matter covered by neural
cortex called cerebellar cortex
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The cerebellum
Cerebellum
© 2013 Pearson Education, Inc.
Figure 7.11
5
Module 7.11 Review
a. Name two major regions of the diencephalon.
b. What are the three regions of the brain stem?
c. What are two functions of the cerebellum?
© 2013 Pearson Education, Inc.
Reticular Activating System (7.12)
• Reticular formation in brain stem regulates
involuntary functions
• Contains the reticular activating system (RAS)
• Input from various sensory pathways carried through
reticular formation to RAS
• RAS then stimulates large areas of cerebral cortex
• Stimulation of RAS increases alertness
• Damage to RAS produces unconsciousness
© 2013 Pearson Education, Inc.
Reticular activating system
Reticular
activating
system
Special
sensory
input
© 2013 Pearson Education, Inc.
General cranial or
spinal nerve input
Nuclei and
centers of
the reticular
formation
Figure 7.12
Module 7.12 Review
a. Describe the reticular formation.
b. Describe the reticular activating system (RAS).
c. You are sleeping and your RAS is suddenly
activated. What will happen?
© 2013 Pearson Education, Inc.
Electroencephalogram (7.13)
• Billions of neurons in brain producing electrical
impulses
• Can measure brain activity using electrodes on
scalp
• Printed report of this activity showing brain waves
called electroencephalogram (EEG)
• EEG shows abnormal brain activity such as
seizures (temporary cerebral disorder) or seizure
disorders like epilepsies
© 2013 Pearson Education, Inc.
Brain Waves (7.13)
• Alpha waves indicate:
• Healthy, awake adults, resting with eyes closed
• Beta waves indicate:
• Concentrating on task, under stress, psychological tension
• Theta waves are seen in:
• Mostly children, short time during sleep in normal adults,
intense frustration in adults
• If seen in other circumstances, may indicate brain disorder
• Delta waves seen in:
• Deep sleep at all ages
• Infant brains and awake adults with damage to brain
© 2013 Pearson Education, Inc.
Brain waves on an electroencephalogram (EEG)
Alpha waves
Beta waves
Theta waves
Delta waves
© 2013 Pearson Education, Inc.
Figure 7.13
1
Module 7.13 Review
a. Define electroencephalogram (EEG) and
describe the four wave types associated with it.
b. You are reading this textbook. If you had an EEG
right now, which brain wave(s) would you expect
to see?
c. Differentiate between a seizure and epilepsy.
© 2013 Pearson Education, Inc.
Spinal Cord Structure (7.14)
• Measures about 45 cm long in adults
• Outer layer of white matter (myelinated axons); inner layer of
gray matter (cell bodies, unmyelinated axons) around central
canal
• Cervical enlargement supplies nerves to shoulder and upper
limb
• Lumbar enlargement supplies nerves to pelvis and lower limbs
• Conus medullaris is tapered, pointed part inferior to lumbar
enlargement
• Spinal cord ends at L1–L2 but spinal roots continue in flared
formation called cauda equina (horse's tail)
© 2013 Pearson Education, Inc.
Superficial anatomy of the adult spinal cord
Cervical
spinal
nerves
Thoracic
spinal
nerves
C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
Cervical
enlargement
Posterior median
sulcus
T9
T10
T11
T12
L1
Lumbar
enlargement
Conus medullaris
L2
Lumbar
spinal
nerves
L3
L4
Inferior tip of
spinal cord
Cauda equina
L5
Sacral
spinal
nerves
S1
S2
S3
S4
S5
Coccygeal
nerve (Co1)
© 2013 Pearson Education, Inc.
Figure 7.14
1
Spinal Cord Segments (7.14)
• Spinal cord divided into 31 segments named according to
associated vertebra
• Posterior median sulcus is shallow, longitudinal groove
on dorsal surface
• Anterior median fissure is deep groove on ventral
surface
• Spinal nerve contains axons of sensory and motor
neurons
• Dorsal root contains axons of sensory neurons
• Dorsal root ganglion contains cell bodies of sensory neurons
• Ventral root contains axons of motor neurons
© 2013 Pearson Education, Inc.
Cross sections through segments of the spinal cord
Posterior median sulcus Dorsal root
Dorsal root ganglion
White matter
Gray
matter
Segment C3
Anterior median
fissure
Spinal nerve
Ventral root
White matter
Gray matter
Segment T3
Central
canal
Segment L1
© 2013 Pearson Education, Inc.
Segment S2
Figure 7.14
2
Module 7.14 Review
a. A typical spinal cord has how many pairs of
spinal nerves, and where does the spinal cord
end?
b. Describe the composition of the gray matter of
the spinal cord.
c. Describe the gross anatomical features of a
cross section of spinal cord.
© 2013 Pearson Education, Inc.
Gray Matter Organization in the Spinal Cord
(7.15)
• Gray matter in spinal cord forms letter H or butterfly shape
• Projections toward outer surface are called horns
• Posterior gray horn contains somatic and visceral sensory
nuclei
• Lateral gray horn found only in thoracic and lumbar
segments contains visceral motor nuclei
• Anterior gray horn contains somatic motor nuclei
• Cell bodies of neurons in groups called nuclei
• Sensory nuclei receive and relay sensory information from
PNS
• Motor nuclei issue motor commands to PNS
© 2013 Pearson Education, Inc.
Cross section of spinal cord
Anterior view of
spinal cord
Posterior median sulcus
Structural Organization
of Gray Matter
Dorsal root
Central canal
Dura mater
Posterior gray horn
Arachnoid mater
(broken)
Pia mater
Dorsal root ganglion
Lateral gray horn
Anterior gray horn
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Anterior median fissure
Ventral root
Figure 7.15
1
White Matter Organization in the Spinal Cord
(7.15)
• Divided into regions called columns
• Posterior white column
• Lateral white column
• Anterior white column
• Columns contain tracts or bundles of axons in
CNS
• Ascending tracts carry sensory information
• Descending tracts carry motor commands
© 2013 Pearson Education, Inc.
Diagrammatic view of the spinal cord
Structural and
Functional
Organization of
White Matter
Posterior white
column
Functional
Organization
of Gray Matter
Dorsal root
Lateral white
column
Somatic
Visceral
Visceral
Somatic
Dorsal root
ganglion Anterior white
column
Sensory nuclei
Ventral root
Motor nuclei
© 2013 Pearson Education, Inc.
Figure 7.15
2
Module 7.15 Review
a. Name the three horns of the spinal cord gray
matter.
b. Differentiate between sensory and motor nuclei.
c. What are the three columns in the white matter?
© 2013 Pearson Education, Inc.
Spinal Meninges (7.16)
•
Protect neural tissue from shocks
•
Continuous with cranial meninges
•
Three layers
1. Dura mater is tough, fibrous covering
•
Epidural space between dura mater and vertebral canal
contains blood vessels and adipose tissue
2. Arachnoid mater includes epithelial layer and
subarachnoid space
3. Pia mater is meshwork of elastic and collagen fibers
attached to surface of spinal cord
© 2013 Pearson Education, Inc.
Spinal meninges
Gray matter
White matter
Ventral root
Spinal meninges
Pia mater
Spinal nerve
Dorsal root
Arachnoid mater
Dura mater
Epidural space
© 2013 Pearson Education, Inc.
Figure 7.16
1
Spinal Tap (7.16)
• Sample of cerebrospinal fluid (CSF) collected by
process called spinal tap or lumbar puncture
• Spinal cord extends to L1 or L2
• Needle inserted between L2 and sacrum where
spinal meninges enclose cauda equina and CSF
• Performed to administer spinal anesthesia or to
sample CSF to test for infection
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Location for a spinal tap or lumbar puncture
Epidural
space
Lumbar puncture
needle
Cauda equina in
subarachnoid space
© 2013 Pearson Education, Inc.
Figure 7.16
2
Module 7.16 Review
a. What are the three layers of the spinal
meninges?
b. Where is the epidural space located and what
does it contain?
c. Why is a spinal tap done below the level of the L2
vertebra?
© 2013 Pearson Education, Inc.