Brain
Chapter 14
General Information
• Wt= 2% of body weight
• 25 billion neurons (45,000/min made before
birth!)
• 20% of bl. circ thru brain/min
• Consumes 20% of O2 at rest
• Bl. delivered by 4 arteries
• Some molecules diffuse easily into brain;ex. O2,
glucose, aa
• Some molecules are blocked by bl. brain barrier
Protection of Brain
• Meninges (meninx= sing.)
1. Dura mater – contains dura folds, tough
-subdural space
2. Arachnoid membrane- spider web like
-subarachnoid space
2. Pia mater – highly vascular
Cerebrospinal Fluid- plate 120
• Shock absorber
• In subarchnoid space, ventricles in brain,
and central canal of spinal cord
• Originates in ependymal cells of choroid
plexus
• http://www.sickkids.ca/childphysiology/cpw
p/Brain/csf.htm
• http://www.cnl.salk.edu/~fellous/courses/c
ogs17f2/csf.mov
http://www.stanford.edu/group/hop
es/basics/braintut/brain.swf
Hydrocephalus- caused when
CSF formation increases, or
reabsorption decreases
Divisions of Brain
1. Brain Stem
a. Midbrain/Mesencephalon
-processes basic visual
and audio data
-reflexive responses
-maintenance of
consciousness
b. Pons
-relays sensory info
-Subconscious center
c. Medulla
-relays sensory info
-autonomic center for
regulation basic life functions
Divisions of Brain
2. Dicephalon- sits on top of brain stem
a. Thalamus-final relay point for ascending
sensory info
b. Hypothalamus-controls emotions
c. Epiphalamus (pineal body)- secretes
melatonin
http://outreach.mcb.harvard.edu/animations/braina
natomy.swf
Divisions of Brain
3. Cerebellum- “little brain”, 2nd largest part
• Outer crust= cortex= made of gray
matter, contains large neurons called
Purkinje cells
• Inside= white matter= braches like tree,
called arbor vitae
• Peduncles- 3 large nerves masses that
connect cerebellum to other parts of
brain
Functions of Cerebellum
1. Promotes smooth muscle movement
2. Maintains muscle tone and posture
3. Receives impulses from middle ear to maintain
equilibrium
-affected by alcohol- produces ataxia=
uncoordinated motions
-damage to Purkinje cells can result in permanent
loss of coordination
http://outreach.mcb.harvard.edu/animations/braina
natomy.swf
Divisions of Brain
4. Cerebrum
4. Cerebrum
• Largest and most prominent brain part
-Contains 12 billion neurons
-And 50 billion glial cells
• Covered by 2-5 mm of gray matter
• Features; gyri, sulci, fissures
Fissures of Cerebrum
1. Longitudinal
- divides left
& right
hemisphere
s
2. Transverseseparates
cerebrum
from
cerebellum
• http://outreach.mcb.harvard.edu/animation
s/brainanatomy.swf
Cerebrum “Connections”
•
Areas of the brain lead to other parts of the
brain via tracts/fibers made of white matter
• 3 types
1. Association- transmit impulses b/t/w neurons in
same hemisphere
2. Commisural- connect cooresponding areas of
left and right hemispheres
3. Projection- extend from cortex to descending
pathways out of cerebrum
Areas of Cerebrum
1. Cerebral Cortex- outermost portion,
white matter
2. Cerebral Nuclei- inner portion, gray
matter
- function in
subconscious control of skeletal muscle,
and learned muscle patterns
Areas of Cerebral Cortex
1. Motor/sensory
a. Frontal lobe/primary motor cortex
voluntary control of skeletal muscle
b. Parietal Lobe/primary sensory cortex
conscious perception through skin+ taste
c. Occipital-/visual cortex
conscious perception of visual stimuli
d. Temporal/ auditory and olfactory cortex
conscious perception of sound and smells
Areas of Cerebrum
2. Association Areas- interpret info and
coordinate a response
a. Somatic sensory- touch
b. Somatic motor- learned movements
b. Visual- C+A+R
c. Auditory- word recognition
Areas of Cerebrum
3. Integrative Centers-complex motor
functions, and analysis
a. Wernicke’s area-receives info from all
sensory association areas, plays role in
personality
b. Broca’s/Speech area- regulates
breathing for speech
c. Prefrontal cortex-time sequencing
Cranial Nerves
• PNS components that connect directly to
brain rather than spinal cord
• 12 cranial nerves- I-XII
• # by position (beginning at cerebrum)
• Classified as sensory, special sensory,
motor, or mixed
• See p466-474
• “On old Olympic towering top a Fin and
German viewed some hops”