Transcript Forebrain

Forebrain
• Review
Overview
– CNS
• Components
• Function
• PNS
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Components
Function
Sensory portion
Motor arm
• Somatic Nervous System
– Function
• Autonomic Nervous System (ANS)
– Function
– Sympathetic and Parasympathetic branches
» Function
» Antagonists
The Human Brain
• Development
– Embryonic
• Neural tube
– Structure
• Week four
– Structure
» Prosencephalon
» Mesencephalon
» Rhombencephalon
– Spinal cord
The Human Brain
• Development
– Fetal
– Telencephalon
• Location
– Cerebellum formation
– Ventricles
The Human Brain
• Cerebrum
– Location
– Lobes
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Frontal
Parietal
Temporal
Occipital
– Landmarks
• Gyri
• Sulci
• Fissures
Cerebrum
• Longitudinal Fissure
– Division
• Central Sulcus
– Division
• Lateral Sulcus
– Division
• Parieto-occipital Sulcus
– Division
• Functional areas
Cerebrum
– Primary Somatosensory Cortex
• Location
• Function
– Somatosensory Association Area
• Location
• Function
– Visual areas
• Location
– Auditory area
• Location
– Olfactory area
• Uncus
Cerebrum
• Functional areas
– Primary Motor area
• Location
• Function
– Broca’s area
• Location
• Function
• Damage
– Pre-Frontal Cortex
• Location
• Function
– Wernicke’s area
• Location
• Function
Cerebrum
• Specialization
– Left hemisphere
– Right hemisphere
• Cerebral Cortex
• White matter
Cerebrum
• Internal Structures
– Grey matter
– White matter
• Tracts
– Association tracts
– Projection tracts
– Commissures
– Corpus callosum
– Fornix
– Septum pellucidum
The Diencephalon
• Location
• Embryologic derivation
• Ventral surface
– Olfactory bulbs and tracts
– Optic nerves
– Optic chiasm
– Optic tracts
– Pituitary gland
– Mammillary bodies
The Diencephalon
• Internal Structures
– Thalamus
• Location
• Function
– Intermediate mass
• Interthalamic adhesion
• Location
– Interventricular foramen
• Location
– Hypothalamus
• Location
• Function
– Infundibulum
• Location
– Epithalamus
• Location
– Pineal body
• Endocrine structure
– Choroid plexus
• Location
• Function
The Brain Stem
• Pons
– Components
• Cerebral peduncles
– location
• Medulla oblongata
– Location
– Function
• Internal Structures
– Cerebral aquaduct
• Location
– Corpora quadrigemina
• Location
• Superior colliculi
• Inferior colliculi
Cerebellum
• Function
• Location
• Hemispheres
– Lobes
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Cortex
White matter
Vermis
Arbor Vitae
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Meninges
Covering
– Brain and spinal cord
– Three layers
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Dura mater
– Leathery, outermost meninx
– Double layered
– Layers
• Periosteal
– Attached to the inner surface of the skull
• Meningeal
– Attached to the outer surface of the brain, continuous with dura mater
of spinal cord
– Extensions
• Dural layers are fused with three exceptions. The inner
membrane extends inward to form a septum to secure the brain in
the cranial cavity
• Falx cerebri
– In longitudinal fissure, attaches to the crista galli of the ethmoid bone
– Creates the Superior sagittal sinus which drains blood from the brain
• Falx cerebelli
– Separates the cerebellar hemispheres
• Tentorium cerebelli
– Separates the cerebrum from the cerebellum
Meninges
• Arachnoid mater
– Middle meninx, web-like, underlies dura
– Subdural space separates dura and arachnoid
– Subarachnoid space
• Contains projections that bridge space between arachnoid and pia
mater
• Filled with cerebrospinal fluid
– Arachnoid villi
• Projections of arachnoid villi that protrude through the dura mater
to allow CSF to drain back into the venous circulation
• Pia mater
– Inner layer
– Highly vascular
– Clings to the surface of the brain, follows convolutions
• Abnormalities
– Meningitis
• Inflammation of the meninges. If infection spreads to the brain,
encephalitis may result
– Encephalitis
• Infection of the brain
Cerebrospinal Fluid
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Function
– Cushion and protect brain
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Composition
– Much like plasma
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Path of CSF
Choroid plexuses
• Small capillary knots hanging from roof of ventricles in the brain. CSF made
here
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Lateral ventricles
Interventricular foramina
Third ventricle
Cerebral aqueduct
Fourth ventricle
From the fourth ventricle, some CSF goes down the central canal of
spinal cord
Most of the CSF goes into the subarachnoid space exiting the
Foramina of fourth ventricle
Arachnoid villi
Dural sinuses
Returned to venous blood
Cerebrospinal Fluid
• Abnormalities
– Normally, CSF forms and drains at a constant rate.
– Drainage failure, due to obstruction (i.e. tumors,
deviations), accumulation of CSF exerts pressure on
brain.
• Adults
– Neurological damage
• Infants
– Hydrocephalus
» “water on the brain”
» Soft spots on infants skull allows expansion and
accomodation
Cranial Nerves
• Part of the PNS, not the brain.
• 12 Pair
– Primarily serve the head and neck
• Vagus Nerve
– Extends into the thoracic cavity and abdominal cavities
• Olfactory and Optic nerves
– Only nerves not arising from the brain stem and pass through
foramina in the skull.
• Names and numbering
– Reflect major structures that they control
• Table 19.1
Cranial Nerves
• Mneumonics
On Old Olympus’ Towering Tops, A Finn And German Viewed Some
Hops":
· In order from 1 to 12:
Olfactory (Cranial Nerve I)
Optic (Cranial Nerve II)
Occulomotor (Cranial Nerve III)
Trochlear (Cranial Nerve IV)
Trigeminal (Cranial Nerve V)
Abducens (Cranial Nerve VI)
Facial (Cranial Nerve VII)
Auditory [or Vestibulocochlear] (Cranial Nerve VIII)
Glossopharyngeal (Cranial Nerve IX)
Vagus (Cranial Nerve X)
Accessory [or Spinal root of the accessory] (Cranial Nerve XI)
Hypoglossal (Cranial Nerve XII)
Cranial Nerves
• Most are mixed nerves and contain motor
and sensory fibers
– Cell bodies located in the brain and peripheral
ganglia
• Optic, olfactory, and vestibulocochlear are
sensory only
– Cell bodies are located in the ganglia
Basal Ganglia
Basal Ganglia
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Caudate
Putamen
Globus Pallidus
Nucleus Accumbens
Ventral Pallidum
Subthalamic Nucleus
Substantia Nigra
Basal Ganglia: Inputs
• Cerebral cortex: all lobes
have projections to
striatum; most are (+)
and use glutamate.
• Substantia nigra pars
compacta: to striatum;
(+) and (–) connections,
uses dopamine.
• Thalamus (intralaminar
nuclei): to striatum; (+)
and use glutamate.
• Raphe nuclei: to BG use
serotonin.
Basal Ganglia: Outputs
• Substantia nigra pars
reticulata: to VL and
VA thalamus; (-) using
GABA.
• Globus pallidus
internal segment: to
VL and VA thalamus;
(-) using GABA.
Limbic System
• Olfactory System
– Olfaction
• Hippocampal
formation
– Memory
• Amygdala
– Emotions and drives
• Hypothalamus
– Homeostasis
Olfactory System
• Olfactory system of lower mammals is typically
large.
• In primates and humans, the olfactory system is
relatively small resulting in a poorer sense of
smell.
• Even so, olfaction can have significant impact on
behavior in humans.
• Primary olfactory cortex is unique among
sensory systems in that it receives direct input
from secondary sensory neurons without an
intervening thalamic relay.
Hippocampus
• 3 main components
– Dentate Gyrus
– Hippocampus
– Subiculum
• 3-layered archicortex
• Circuitry has been
extensively studied
because of its importance
in memory
• Storage itself is thought
to be back in the
association cortex not
medial temporal lobe
Amygdala
Amygdala II
• Amygdala is especially important in emotions
and drives.
• Amygdala has extensive connections with other
limbic areas and is also involved in memory,
olfaction, and homeostasis.
• Amygdala is especially important for attaching
emotional significance to various stimuli
perceived by the association cortex. In animals
where both amygdalas have been ablated,
behavior is very placid, tame, and nonaggressive.
Hypothalamus
• Preoptic area
– medial preoptic nucleus
– lateral preoptic nucleus
• Anterior region
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anterior hypothalamic nucleus
Supraopticnucleus
paraventricular nucleus
suprachiasmatic nucleus
• Middle region
– arcuate nucleus
– ventromedial nucleus
– dorsomedial nucleus
• Posterior region
– mammillary nuclei
– posterior hypothalamic
nucleus
Cerebral Cortex
• Brain’s most complex
area with billions of
neurons and trillions of
synapses
– Consciousness
– Perceives sensations
– Commands skilled
movements
– Emotional awareness
– Memory, thinking, language
ability
– Motivation
– All “higher” mental
functions
Cerebral Cortex II
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Highly developed in primates and cetaceans
50% of total brain weight in humans
Surface area of 2.5 square feet in humans
4.5 mm thick in precentral gyrus; 1.5 mm thick
in visual cortex
• Only 1/3 of surface area visible, 2/3 in banks of
sulci
• Surface of gyri and sulci
• Estimated to contain about 15 billion neurons in
humans
Cortical Anatomy
• 6 lobes: frontal, parietal,
temporal, occipital, limbic
and insular
• Each lobe has several
gyri
• Functionally the cortex is
divided into numbered
areas first proposed by
Brodmann in 1909
• Brodmann’s areas were
described based on
cytoarchitecture; later
they were found to be
functionally significant
Brain Atrophy in MS
MRI
• Brain Parenchymal Fraction (BPF)
decreased in MS
– Rudick 1999
• Grey Matter Fraction (GMF) and White
Matter Fraction (WMF) decreased in MS
– Chard 2002
• Cortical Thinning in MS
– Sailer 2003