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The Brain

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The Nervous System
The Brain
Chapter 16
The Brain - Overview
 Brain stem
 medulla oblongata (M.O.)
Cerebrum
 pons
 midbrain (mesencephalon)
 Diencephalon
T
 thalamus
PP
H
 hypothalamus
midbrain
Cerebellum
 epithalamus (pineal gland)
Cerebrum
pons
m.o.
 Cerebellum
Cranial Meninges
Three layers: Dura mater, Arachnoid mater, Pia
mater
 Dura mater – tough, fibrous outer layer; 2
layers thick around brain (superficial
“periosteal layer”/deeper “meningeal layer”)
with creation of dural (venous) sinuses
between layers, and dural folds into cranial
cavity
Dural folds
Folds that create septa to subdivide
cranial cavity and stabilize the brain.
Includes:
 falx cerebri – between cerebral
hemispheres in longitudinal fissure
 tentorium cerebelli – between
cerebrum & cerebellum in transverse
fissure
 falx cerebelli – between cerebellar
hemispheres
 diaphragma sellae – lines sella
turcica
Falx cerebri
Tentorium cerebelli
Dural sinuses
Spaces between dural layers and dural folds
functioning as veins for drainage of blood from
cerebral veins, and CSF from subarachnoid
space (superor sagittal sinus)
Falx cerebri
Superior sagittal sinus
Inferior sagittal sinus
Tentorium cerebelli
Straight
sinus
Confluence
of sinuses
Transverse
sinus
Sigmoid sinus
 Arachnoid mater – “spidery” web-like middle
layer with fine collagen & elastic connections to
underlying Pia Mater
 Pia mater – delicate, thin inner layer
Subarachnoid space –
between arachnoid & pia mater;
contains cerebrospinal fluid
(CSF)
Arachnoid granulations
(villi) – projections of arachnoid
into dural sinuses for drainage
of CSF
Cerebrospinal Fluid (CSF)
 clear, colorless fluid formed by filtration of blood
plasma by choroid plexuses within ventricles of the
brain.
 functions in protection of CNS, support, nutrient
supply, waste removal
CSF Circulation
Lateral ventricles (in cerebral
hemispheres) пѓ interventricular foramen пѓ third ventricle (in diencephalon
around and between R/L
thalamus) пѓ cerebral
(mesencephalic) aqueduct of
midbrain пѓ fourth ventricle
(between pons/cerebellum) пѓ subarachnoid space & central
canal of SC
Reabsorption of CSF through
arachnoid granulations (arachnoid
villi) of dural sinuses (superior
sagittal sinus) пѓ into cerebral veins
Blood supply to Brain
 Brain requires large amounts of O2 and nutrients (glucose)
 Internal carotid arteries + basilar artery (from vertebral
arteries) пѓ вЂњcerebral arterial circle (of Willis)”
 Venous drainage from dural venous sinuses & cerebral
veins into vertebral and internal jugular veins
The Brainstem
 Medulla oblongata
 continuation of the SC above the foramen
magnum
 contains the pyramidal decussation within
the pyramids
 cranial nerve nuclei (XII-VIII (cochlear)
 cardiac, vasomotor, & respiratory reflex
centers
 Pons
 “bridge” linking cerebellum to SC & other
parts of brain via middle cerebellar peduncle
 cranial nerve nuclei (VIII (vestibular) – V)
 respiratory center
The Brainstem
 Midbrain (mesencephalon)
 cerebral peduncles –
location of ascending
(sensory) & descending
(motor) tracts
 tectum – posterior aspect
of brainstem; contains
 corpora quadrigemina
 superior colliculi –
visual reflex centers
 inferior colliculi –
auditory reflex centers
 cranial nerve nuclei (IV-III)
The Brainstem
 Midbrain (mesencephalon)
 substantia nigra –
nucleus with dark
pigmented neurons that
regulate motor output of
basal nuclei (basal ganglia)
of cerebrum
 reticular formation –
network of interconnected
nuclei throughout
brainstem responsible for
maintaining states of
consciousness
The Diencephalon
Thalamus
 surrounds 3rd
ventricle
 2 sides (left & right
thalamus) usually
connected by
intermediate mass
(interthalamic
adhesion)
 comprised of nuclei
that function
primarily as sensory
relay stations
The Diencephalon
Hypothalamus
 connects to pituitary gland via the
infundibulum
 has many important functions
relating to maintaining homeostasis
including (but not limited to):
-integrating nervous & endocrine
systems through control over
pituitary gland
-integration of ANS from
visceral stimuli
-hunger/satiety, thirst, body temp.
regulation, circadian rhythms
-hormone production
(ADH,
oxytocin)
 mamillary bodies – reflex centers
associated with eating, & processing
of olfactory sensations
The Diencephalon
Epithalamus Pineal gland
 secretes
Melatonin which
helps regulate
day-night cycles
(circadian
rhythm)
The Cerebellum
 Separated from cerebrum by transverse fissure
 “Tentorium cerebelli” encloses straight sinus & transverse sinus
 Two hemisphereres joined by vermis
 Hemispheres have 3 lobes – anterior, posterior & flocculonodular
 outer cortex of gray matter folded into “folia”
 inner white matter “arbor vitae”
Transverse fissure
The Cerebellum
Links to brainstem by cerebellar peduncles
 inferior cerebellar peduncle пѓ M.O. (and S.C.)
 middle cerebellar peduncle пѓ pons
 superior cerebellar peduncle пѓ midbrain (and
diencephalon/cerebrum)
Functions include:
 control of skeletal muscles (unconscious) for balance, coordination
& posture
 stores patterns of movement
convolutions
Cerebrum
gyrus
sulcus
Transverse
fissure
Lobes of Cerebral Hemispheres
Central sulcus
Parietal lobe
Parieto-occipital
sulcus (seen
along medial
surface)
Frontal lobe
Occipital
lobe
Lateral sulcus
(Insula is deep to
lateral sulcus)
Temporal lobe
Parieto-occipital sulcus
insula
Gray & White matter of cerebrum
Gray matter :
 superficial cortex
–functional areas
includes sensory,
motor , & higher
order functions
 deep cerebral
nuclei (aka basal
nuclei/basal
ganglia)
White matter:
 fibers –
association
commissural
projection
White matter of cerebrum
Association
fibers
Commissural
fibers
Projection
fibers
 association fibers –
connect gyri in same
hemisphere
 commissural fibers –
connect gyri in opposite
hemispheres (e.g.
corpus callosum, anterior
commissure)
 projection fibers –
connect cerebrum with
other parts of brain &
spinal cord (e.g. internal
capsule)
Gray matter of cerebrum
Basal (cerebral) Nuclei
 Paired clusters of gray matter
deep within cerebral
hemispheres
 Include: caudate nucleus,
putamen, globus pallidus
 Involved primarily in
subconscious control of skeletal
muscle tone, and coordination of
movement patterns once
movement is initiated
Gray matter of cerebrum
Cerebral Cortex - Functional areas
 Motor and Sensory areas – receive sensory info & generate
motor (skeletal muscle) responses
 Association areas – interpretation of sensory info & planning
and coordination of motor responses
 Cerebral processing centers - higher order integrative &
analytical functions
Motor & Sensory
primary motor cortex
(precentral gyrus)
Motor &
Sensory
primary sensory cortex
(postcentral gyrus)
Motor & Sensory
primary motor cortex
(precentral gyrus)
primary sensory cortex
(postcentral gyrus)
gustatory
cortex
visual
cortex
auditory cortex
olfactory cortex
Association areas
• interpret incoming
somatic motor association
area (premotor cortex)
sensations; coordinate motor
responses
visual
association
area
Cerebral Processing Centers
• higher-order integrative
centers
• may be unilateral
general interpretive
area (Wernike’s) –Lt
hemisphere usually
motor speech
center (Broca’s) Lt hemisphere
usually
Prefrontal
cortex (bilat.)
Hemispheric Specialization
Higher order centers in
brain not bilaterally
symmetrical in regards to
function:
Left hemisphere more
involved in linear,
mathematical, verbal,
analytical functions
Right hemisphere more
involved in abstract
analysis, spatial perception,
sensory relationship, music,
emotional context of
language
Limbic System
Functionally related areas in cerebrum, thalamus & hypothalamus involved in
 emotional states, drives & behaviors
 linking conscious areas of cerebrum with unconscious areas of
brainstem
 long term memory
Major areas include:
Amygdaloid body
(amygdala)
Cingulate gyrus
Dentate gyrus
Parahippocampal
gyrus
Hippocampus
Fornix
Mamillary bodies
Cranial Nerves
 12 pairs of nerves that connect to the brain;
provide motor, sensory &/or autonomic
(parasympathetic) function
Cranial Nerves (know #, name & basic function)
I Olfactory – smell
II Optic – sight
III Oculomotor – motor to eye muscles; ANS for accommodation of lens &
pupil constriction
IV Trochlear – motor to one eye muscle
V Trigeminal – motor to muscles of mastication, sensation to face & mouth
VI Abducens – motor to one eye muscle
VII Facial – motor to muscles of facial expression; taste; ANS to lacrimal &
salivary glands
VIII Vestibulocochlear – equilibrium & hearing
IX Glossopharyngeal – swallowing, taste, ANS to salivary glands, sensory
reception from monitoring of blood pressure in large arteries
X Vagus – sensation from viscera; ANS visceral muscle movement
(respiratory, digestive, cardiovascular systems)
XI Accessory – motor to muscle of pharynx, SCM & Trapezius
XII Hypoglossal – motor to tongue muscles
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