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 O 2 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 p/Brain/csf.htmhttp:// p/Brain/csf.htm ogs17f2/csf.movhttp:// ogs17f2/csf.mov

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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 natomy.swf

Divisions of Brain 3.Cerebellum- “little brain”, 2 nd 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 natomy.swf

Divisions of Brain 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.Transverse- separates cerebrum from cerebellum

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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 p “On old Olympic towering top a Fin and German viewed some hops”