Download Brain Notes

Protection of CNS
1
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The Brain
 3 lbs
 About the size of two fists
 Wrinkled
 Not solid- kind of mushy to
the touch
 Highly vasculated
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Blood supply & Nutrition
• Brain is highly vascular
• blood delivers O2 and glucose supply and carries
away wastes
• Brain cells have no capacity for anaerobic
respiration. They cannot be O2 deprived
• Brain cells die w/in 5-6 minutes
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Protection
1. Bone
• Cranial bones & vertebral arches
2. Meninges
• Dura mater
• Arachnoid mater
• Pia mater
3. Cerebrospinal fluid (CSF)
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Meninges
3 Layers
• Dura mater (made of two membranes)
• Arachnoid mater
• Pia mater
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Dura Mater

“Tough Mother”

Thick, leathery outer covering

Support, and forms sinus system (where blood
drains and returns to the heart)

Pain sensitive

Has own blood supply –
Middle meningeal artery
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Dura Mater
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Arachnoid


Spongy/fibrous layer between the dura and pia

connective tissue

forms projections which give it a spider-web
appearance
Forms Subarachnoid space

Contains CSF
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Pia Mater

Innermost layer

Adheres almost indistinguishably to cortical surface,
including sulci and gyri

Difficult to see grossly or remove
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
3 Layers of Meninges
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrospinal Fluid
• Produced from blood
plasma in choroid
plexuses
• Located in the
subarachnoid space
• Cushions CNS - like
waterbed
• Nourishes brain tissue
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrospinal Fluid
• Returned to blood
at superior sagittal
sinus
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Blood-brain barrier
• Capillaries in the choroid plexus have
thicker walls (than capillaries found
elsewhere).
• This means less molecules can
passively diffuse into the CSF
• Most molecules must be actively
transported (therefore, they are
“selected” to enter)
• Protects brain from drugs, metabolites,
toxins
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Ventricles of the Brain
• 2 Lateral ventricles (1, 2) in cerebral hemispheres
• Third ventricle (3) between hemispheres (under the fornix)
•Cerebral aquaduct connects the 3rd and 4th
• Fourth ventricle (4) in midbrain and medulla
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Anatomy of the Brain
4 Major Regions of the Brain
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1. Cerebrum or Cerebral Hemisphere
1. Cerebral Hemispheres (Cerebrum)
 Paired superior parts of the brain
 Largest part: includes more than half of the
brain mass
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 The surface is made of ridges (gyri or 1 gyrus)
and grooves (sulci or 1 sulcus)
 Deeper grooves called fissures exist
 Longitudinal fissure: separates the
right and left hemisphere of the
cerebrum
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Cerebrum
Central sulcus
Lateral sulcus
4 Lobes of the cerebrum (on
each hemisphere)
 Lobes are named based
*Parietooccipital
on the cranial bones that
sulcus
lie over them
 Surface lobes of the
cerebrum
1. Frontal lobe
2. Parietal lobe
3. Occipital lobe
4. Temporal lobe
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Specialized areas of the Cerebrum
 Cerebral Cortex:
 outer layer of the cerebrum (grey matter/cell bodies)
 Processing of information occurs here
 Labeled A
 There are also “islands” of grey matter known as
basal nuclei
*label B shows
white matter/
neural axonsrelaying of
information
occurs here
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrum
Corpus callosum connects the two cerebral hemispheres
 It is a nerve tract (bundle of nerves having the same origin and
destination)
 Necessary for communication between the two hemisperes
 Corpus callosotomy- cuts the corpus callosum to interrupt the
spread of seizures, makes them less severe.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrum: Cerebral Cortex
Pre motor area
(right side controls left sidevice versa)
Postcentral gyrus
Primary somatic sensory
area:
receives impulses from the
body’s sensory
receptors (pain, cold, etc)
 Precentral gyrus
Primary motor area
 Sends impulses to
 Premotorconsciously
area
move
skeletal
muscles
 Stores
sequence
activities
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Cerebrum: Cerebral Cortex: Frontal Lobe
Association cortex:
involved in planning,
complex ideas,
behaviors, concentration,
ability to focus,
emotional traits,
judgment and inhibition
Broca’s area:
Involved in our ability to
speak
Asymmetric (only on left
hemisphere)
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Cerebrum: Cerebral Cortex: Parietal Lobe
Association
cortex:
receive and utilize
information from
the lower levels of
the brain:
temperature,taste,
touch, and
movement from
the rest of the
body – such as
distance and
position of objects
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrum: Cerebral Cortex: Temporal Lobe
Important for making new
memories, and for shortterm memory, including
memories of taste,
sound, sight, and touch
Wernicke’s Area
responsible for receiving
auditory information and
recognizing words; it is
thus central to the
process of learning and
understanding language.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebrum: Cerebral Cortex: Occipital Lobe
primary visual center of
the brain, processes
information from the
eyes, and links that
information with images
stored in memory.
In other words, this area
helps you determine
what you are looking at.
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Regions of the Brain: 2. Diencephalon

Sits on top of the brain stem

Enclosed by the cerebral hemispheres

Made of three parts
(shown in yellow on brain model)
1. Thalamus
2. Hypothalamus (posterior to optic chiasma)
3. Epithalamus
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Diencephalon
1. Thalamus
The relay station for sensory impulses

Transfers impulses to the
correct part of the cerebral
cortex for localization and
interpretation
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Regions of the Brain: Diencephalon
2. Hypothalamus (posterior to
optic chiasma)
 stimulates and controls
structures such as the heart,
most glands and smooth
muscles
 allows your systems to
excite and relax, as needed.
Examples:

Regulate body
temperature

Controls water balance

Regulates metabolism

Drive/emotion, sex,
appetite, thirst
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Regions of the Brain: Diencephalon
 Hypothalamus
The pituitary gland is attached to the
hypothalamus
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Diencephalon
3. Epithalamus
Location of pineal body
primarily responsible for melatonin cycles
Includes the choroid plexus
bundle of capillaries that form cerebrospinal
fluid
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3. Brain Stem
 Attaches to the spinal cord
Parts of the brain stem
A. Midbrain
B. Pons
C. Medulla oblongata
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Brain Stem
A. Midbrain
Tracts of nerve fibers
 Reflex centers for vision and hearing
 Send messages to and from cerebrum
 Connect the third and fourth ventricles- cerebral
aquaduct
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Brain Stem
B. Pons
 The bulging center part of the brain stem
 Mostly composed of fiber tracts
 Controls breathing
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Brain Stem
C. Medulla Oblongata
 The lowest part of the brain stem
 Merges into the spinal cord
 Involuntary control center
 Heart rate control
 Blood pressure regulation
 Breathing/Coughing
 Swallowing/Gagging
 Vomiting
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4. Cerebellum
 Two hemispheres with convoluted surfaces (like the
cerebrum)
 Provides involuntary coordination of body
movements (fine motor skills and smooth
movements)
 Balance/Coordination
 Monitors body position
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings