Transcript Limbic System

PowerPoint® Lecture Slides
prepared by Vince Austin,
Bluegrass Technical
and Community College
CHAPTER
12
The Central
Nervous
System:
Part C
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Functional Brain Systems
• Networks of neurons that work together and
span wide areas of the brain
• Limbic system
• Reticular formation
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Septum pellucidum
Diencephalic structures
of the limbic system
•Anterior thalamic
nuclei (flanking
3rd ventricle)
•Hypothalamus
•Mammillary
body
Olfactory bulb
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Corpus callosum
Fiber tracts
connecting limbic
system structures
•Fornix
•Anterior commissure
Cerebral structures of the
limbic system
•Cingulate gyrus
•Septal nuclei
•Amygdala
•Hippocampus
•Dentate gyrus
•Parahippocampal
gyrus
Figure 12.18
Limbic System
• Emotional or affective brain
• Amygdala—recognizes angry or fearful facial
expressions, assesses danger, and elicits the
fear response
• Cingulate gyrus—plays a role in expressing
emotions via gestures, and resolves mental
conflict
• Puts emotional responses to odors
• Example: skunks smell bad
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Limbic System: Emotion and Cognition
• The limbic system interacts with the prefrontal
lobes, therefore:
• We can react emotionally to things we
consciously understand to be happening
• We are consciously aware of emotional
richness in our lives
• Hippocampus and amygdala—play a role in
memory
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Reticular Formation: RAS and Motor Function
• RAS (reticular activating system)
• Sends impulses to the cerebral cortex to keep
it conscious and alert
• Filters out repetitive and weak stimuli (~99% of
all stimuli!)
• Severe injury results in permanent
unconsciousness (coma)
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Reticular Formation: RAS and Motor Function
• Motor function
• Helps control coarse limb movements
• Reticular autonomic centers regulate visceral
motor functions
• Vasomotor
• Cardiac
• Respiratory centers
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Language
• Language implementation system
• Basal nuclei
• Broca’s area and Wernicke’s area (in the
association cortex on the left side)
• Analyzes incoming word sounds
• Produces outgoing word sounds and grammatical
structures
• Corresponding areas on the right side are
involved with nonverbal language components
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Protection of the Brain
• Bone (skull)
• Membranes (meninges)
• Watery cushion (cerebrospinal fluid)
• Blood-brain barrier
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Meninges
• Cover and protect the CNS
• Protect blood vessels and enclose venous
sinuses
• Contain cerebrospinal fluid (CSF)
• Form partitions in the skull
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Meninges
• Three layers
• Dura mater
• Arachnoid mater
• Pia mater
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Superior
sagittal sinus
Subdural
space
Subarachnoid
space
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Skin of scalp
Periosteum
Bone of skull
Periosteal Dura
Meningeal mater
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Figure 12.24
Dura Mater
• Strongest meninx
• Two layers of fibrous connective tissue
(around the brain) separate to form dural
sinuses
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Arachnoid Mater
• Middle layer with weblike extensions
• Separated from the dura mater by the
subdural space
• Subarachnoid space contains CSF and blood
vessels
• Arachnoid villi protrude into the superior
sagittal sinus and permit CSF reabsorption
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Superior
sagittal sinus
Subdural
space
Subarachnoid
space
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Skin of scalp
Periosteum
Bone of skull
Periosteal Dura
Meningeal mater
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Figure 12.24
Pia Mater
• Layer of delicate vascularized connective
tissue that clings tightly to the brain
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Cerebrospinal Fluid (CSF)
• Composition
• Watery solution
• Less protein and different ion concentrations
than plasma
• Constant volume
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Cerebrospinal Fluid (CSF)
• Functions
• Gives buoyancy to the CNS organs
• Protects the CNS from blows and other trauma
• Nourishes the brain and carries chemical
signals
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Superior
sagittal sinus
4
Choroid
plexus
Arachnoid villus
Interventricular
foramen
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Right lateral ventricle
(deep to cut)
Choroid plexus
of fourth ventricle
3
Third ventricle
1 CSF is produced by the
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
(a) CSF circulation
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2
choroid plexus of each
ventricle.
2 CSF flows through the
ventricles and into the
subarachnoid space via the
median and lateral apertures.
Some CSF flows through the
central canal of the spinal cord.
3 CSF flows through the
subarachnoid space.
4 CSF is absorbed into the dural venous
sinuses via the arachnoid villi.
Figure 12.26a
Choroid Plexuses
• Produce CSF at a constant rate
• Hang from the roof of each ventricle
• Clusters of capillaries enclosed by pia mater
and a layer of ependymal cells
• Ependymal cells use ion pumps to control the
composition of the CSF and help cleanse CSF
by removing wastes
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Ependymal
cells
Capillary
Section
of choroid
plexus
Connective
tissue of
pia mater
Wastes and
unnecessary
solutes absorbed
CSF forms as a filtrate
containing glucose, oxygen,
vitamins, and ions
(Na+, Cl–, Mg2+, etc.)
(b) CSF formation by choroid plexuses
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Cavity of
ventricle
Figure 12.26b
Blood-Brain Barrier
• Helps maintain a stable environment for the
brain
• Separates neurons from some bloodborne
substances
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Blood-Brain Barrier
• Composition
• Continuous endothelium of capillary walls
• Basal lamina
• Feet of astrocytes
• Provide signal to endothelium for the
formation of tight junctions
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Capillary
Neuron
Astrocyte
(a) Astrocytes are the most abundant
CNS neuroglia.
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Figure 11.3a
Blood-Brain Barrier: Functions
• Selective barrier
• Allows nutrients to move by facilitated diffusion
• Allows any fat-soluble substances to pass,
including alcohol, nicotine, and anesthetics
• Absent in some areas, e.g., vomiting center
and the hypothalamus, where it is necessary
to monitor the chemical composition of the
blood
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