I) THE BRAIN

A. The brain is composed of four basic parts
     1. cerebrum (cerebral hemispheres)
     2. diencephalon
          a. thalamus
          b. hypothalamus
          c. epithalamus
     3. brain stem
          a. midbrain
          b. pons
          c. medulla
     4. cerebellum

B. Ventricle
     1. A ventricle is a cavity in the brain.
     2. They are lined with ependymal cells.
     3. They are filled with cerebrospinal fluid.
     4. There are several ventricles.
          a. lateral (1st & 2nd) ventricle - C-shaped chambers, one in each cerebral hemisphere
          b. third ventricle - is a thin chamber in the center of the brain (in the diencephalon)
          c. fourth ventricle - extends down into the brain stem to the spinal cord

C. The brain has distinct features, specifically lobes, fissures, and functional areas.
     1. Lobes
          a. frontal
          b. parietal
          c. occipital
          d. temporal
     2. Fissures
          a. longitudinal - separates the cerebrum into right and left cerebral hemispheres
          b. transverse - separates the cerebral hemispheres from the cerebellum below
     3. Functional areas
          a. Motor areas
               i. primary motor cortex
                    1. in the frontal lobe
                    2. controls voluntary movement of muscles
               ii. premotor cortex
                    1. in the frontal lobe
                    2. controls repetitive or patterned movements
               iii. Broca's area
                    1. in the frontal lobe of one hemisphere, usually the left
                    2. directs muscles of speech
                    3. may be involved in thinking before we speak or move
               iv. frontal eye field
                    1. in front of the premotor cortex and above Broca's area
                    2. controls voluntary movement of the eye
          b. Sensory areas
               i. primary somatosensory cortex
                    1. in the parietal lobe
                    2. receives sensory information from the body
               ii. somatosensory association area
                    1. behind the somatosensory cortex
                    2. integrates and analyzes sensory inputs into an evaluation of what is being felt relative to its size,
                         texture, and the relationship of its parts
               iii. visual areas
                    1. in the occipital lobe
                    2. interpretes visual input (sight)
               iv. auditory area
                    1. in the temporal lobe
                    2. interpretes auditory input (hearing)
               v. olfactory cortex
                    1. in the temporal lobe
                    2. interpretes smells
               vi. gustatory (taste) cortex
                    1. located in the parietal lobe, deep to the temporal lobe
                    2. interpretes tastes
          c. Association areas
               i. prefrontal cortex
                    1. in the frontal lobe
                    2. involved with intellect, complex learning abilities, and personality
               ii. general interpretation area
                    1. a vague region in the temporal, parietal, and occipital lobes
                    2. appears to be a storage site for complex memory patterns associated with sensations
                    3. allows you to interprete an entire situation
               iii. language areas
                    1. Wernicke's area
                    2. affective language areas
               iv. visceral association area
                    1. conscious interpretation of internal sensations
                    2. examples include an upset stomach, a full bladder, etc.

D. Diencephalon
     1. The diencephalon is the central core of the brain.
     2. It consists of three parts, which surround the 3rd ventricle.
          a. thalamus
               i. makes up 80% of the diencephalon
               ii. it is a major relay station
                    1. sensory impulses ascending to the sensory cortex
                    2. inputs of subcortical motor nuclei and the cerebellum to the cerebral motor cortex
          b. hypothalamus
               i. an autonomic nervous system control center
               ii. an important part of the limbic system; it is the center for emotional response and behavior
               iii. it regulates water balance and thirst
               iv. it regulates body tempurature
               v. it regulates food intake
               vi. it regulates the sleep-wake cycles
               vii. it controls the functioning of the endocrine system
          c. epithalamus
               i. consists of the pineal gland and the choroid plexus of the 3rd ventricle
                    1. pineal gland - which secretes melatonin, helps regulated the sleep-wake cycle, and relates to some
                              aspects of mood
                    2 . choroid plexus - a cerebrospinal fluid-forming structure

E. Brain Stem: 3 major regions
     1. midbrain
          a. corpora quadrigemina
               i. superior colliculi - visual reflex centers
               ii. inferior colliculi - auditory relay and reflex centers
          b. red nucleus - relay nuclei iii. nuclei of cranial nerves III and IV
     2. pons
          a. mainly a conduction area
          b. its nuclei help regulate the respiration and cranial nerves V-VII
     3. medulla
          a. nuclei regulate respiratory rhythm, heart rate and blood pressure
          b. serves cranial nerves VIII-XII
          c. controls coughing, sneezing, swallowing, and vomiting

F. Cerebellum
     1. Structure
          a. the cerebellum consists of 2 hemispheres
          b. it is marked by convolutions and separated by the vermix
     2. Function
          a. it processes and interpretes impulses from the motor cortex and sensory pathways
          b. it coordinates motor activity so that smooth, well-timed movements occur

G. Limbic system
     1. consists of numerous structures that encircle the diencephalon
     2. it is the "emotional-visceral brain"

H. Reticular formation
     1. includes the nuclei spanning the length of the brain stem
     2. it maintains the alert state of the cerebral cortex
     3. its motor nuclei serve both somatic and visceral motor activities

I. Protection of the CNS
     1. Bone
     2. Meninges - three membrane layers that surround the brain and spinal cord
          a. dura mater - the outermost layer
          b. arachnoid mater
          c. pia mater - the innermost layer
     3. Cerebrospinal fluid (CSF)
          a. formed by the choroid plexuses from blood plasma
          b. circulates through the ventricles and into the subarachnoid space
          c. it supports and cushions the brain & spinal cord and helps to nourish them
     4. Blood-brain barrier - the epithelium of the capillaries of the brain is relatively impermeable

J. Injuries to the brain
     1. concussion
          a. reversible damage
          b. the injury is slight
          c. it may be characterized by dizziness, "seeing stars", or brief loss of consciousness
     2. contusion
          a. nonreversible damage
          b. tissue is destroyed

K. Cerebrovascular accidents (strokes)
     1. Result when blood circulation to the brain neurons is blocked and brain tissue dies
     2. Can result in hemiplegia, sensory deficits, or speech impairment

L. Alzheimer's disease
     1. a degenerative brain disease
     2. causes slow, progressive loss of memory and motor control and increasing dementia

II. THE SPINAL CORD

A. Gross anatomy
     1. the spinal cord, wrapped in meninges and cerebrospinal fluid, resides within the vertebral column
     2. the cord goes from the foramen magnum down to the end of the first lumbar vertebrae
     3. an average person's cord is 42 cm (17") long and 1.8 cm (3/4") thick
     4. 31 pairs of spinal nerve roots extend from the cord

B. Microscopic anatomy
     1. the central gray matter of the cord is H shaped
          a. anterior horns (extensions) contain somatic motor neurons
          b. lateral horns contain visceral (autonomic) motor neurons
          c. posterior horns contain associative neurons (interneurons)
     2. the outside layer of the cord is white matter
          a. it contains myelinated and unmyelinated nerve fibers
          b. these fibers run in 3 directions
               i. ascending - sensory inputs moving up
               ii. descending - motor outputs moving down
               iii. commissural - from one side of the cord to the other
          c. each side of the white matter has 3 columns (funiculi)
               i. posterior funiculi
               ii. lateral funiculi
               iii. anterior funicui
          d. each funiculi contains paired tracts of ascending and descending nerve tracts
               i. ascending (sensory) tracts
                    1. fasciculi gracilis and cuneatus - touch & joint proprioception
                    2. spinothalamic tracts - pain, touch, temperature
                    3. spinocerebellar tracts - muscle/tendon proprioception
               ii. descending (motor) tracts
                    1. pyramidal tracts
                    2. motor tracts

III. DIAGNOSTIC PROCEDURES FOR THE CNS

A. Several techniques are used to diagnose brain disorders
     1. routine reflex testing (ie. hitting the knee with a mallet to check a reflex)
     2. pneumoencephalography - cerebrospinal fluid is withdrawn and the ventricles filled with air, allowing them to
               be visualized easier
     3. cerebral angiography - a dye is injected into the blood vessels so that they can be seen in an X- ray
     4. CT, MRI, PET scans - imaging techniques that allow us to see internal structures