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/

cpwp/Brain/csf.htm• http://www.cnl.salk.edu/~fellous/courses/

cogs17f2/csf.mov

http://www.stanford.edu/group/hopes/basics/braintut/brain.swf

Hydrocephalus- caused when CSF formation increases, or reabsorption decreases

Divisions of Brain1. Brain Stema. Midbrain/Mesencephalon-processes basic visual and audio data-reflexive responses-maintenance of consciousnessb. Pons-relays sensory info -Subconscious centerc. 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/brainanatomy.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 movement2. Maintains muscle tone and posture3. 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 coordinationhttp://outreach.mcb.harvard.edu/animations/

brainanatomy.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 hemispheres

2. Transverse- separates cerebrum from cerebellum

• http://outreach.mcb.harvard.edu/animations/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”