Lecture 7 - Part III
Brain and Spinal Cord

Images:
1. Brain - lateral view: Lobes
2. Brain - Sagital view: Structures, Ventral view: Hemispheres
3. Brain - Sagital view: Meninges

I. Brain : Note – Cross Reference your text book with this lecture.
1. Brain and spinal cord are protected by bone: cranium and vertebrae of spinal column. Intervertebral disks absorb shock.
2. Brain is protected by  3 membranes called meninges. Outermost membrane is the dura matter composed of dense fibrous connective tissue. Middle membrane, is the arachnoid - a thin transparent sheath. Innermost membrane is pia matter. Continuous with spinal cord. 3. Brain - Sagital view: Meninges
3. Between arachnoid and pia mater is a space called subarachnoid space.
4. In between inner two membranes is cerebrospinal fluid. Fluid cushions brain from shock and pass materials from brain and blood. Fluid is continuous with spinal cord. In  brain fluid fills 4 ventricles.
5. Concussion is a brain bruise.
6. Brain receives 20% of blood pumped from heart. Replaces most of its protein every 3 weeks. Has most abundance of mitochondria.
3. Weighs about 1.4 Kg (3 pounds), and contains bout 100 billion neurons, each of which is functionally connected with 100,000 other neurons.
4. Averages 1200 - 1400 cm3; but 750 cm3 is still normal.
5 . 3 parts of brain: These are developmental or ancestral.

2. Brain - Sagital view: Structures, Ventral view: Hemispheres

a. Forebrain - composed of cerebrum, thalamus, and hypothalamus
b. Midbrain - relay center. In lower animals is more dominant and important.
c. Hindbrain - composed of cerebellum, medulla oblongata, and pons
-Note the Brain stem is composed of the Midbrain and the Hindbrain.

II. The Cerebrum
1. The cerebrum is the largest part of the brain. Makes up 2/3 of entire organ. 2. Brain - Sagital view: Structures, Ventral view: Hemispheres
2. The left and right cerebral hemispheres are separated by the longitudinal fissure
3. The corpus callosum is a bridge like connection between hemispheres and other parts of the nervous system.(white matter - myelinated).
4. The outermost covering is called the cerebral cortex - gray matter: cell bodies and dendrites of neurons which are interconnect by unmyelinated fibers.
5. The outer surface has many folds or convolutions which increases surface area of gray matter.
6. The deeper furrows between them are called sulci.
7.. The deepest furrows are called fissures.
8. Cerebral cortex (outer portion) has four lobes with the following functions: 1. Brain - lateral view: Lobes

1. Frontal - Primary motor cortex - Voluntary control of skeletal muscles; controls personality, intelligence, and speech.
2. Temporal - Auditory cortex and olfactory cortex; Conscious perception of auditory, olfactory stimuli.
3. Parietal - Primary sensory cortex; Conscious perception of touch, pressure, vibration, pain, temperature, and taste - controls sensory input
4. Occipital - Visual cortex: Conscious control of visual stimuli.

9.There are 3 major functions and areas of cerebral cortex:1. Sensory, 2. motor, and 3.associative.
10. Sensory areas receive and interpret impulse for sense receptors: eyes, ears, taste buds, nose, touch, pain, pressure, heat, and cold receptors.
11. Motor areas of cortex start impulse responsible for all voluntary movement.
12. Associative areas are responsible for memory, learning, and thought.
13. the 2 cerebral hemispheres do not function in exactly same way. Left is center for mathematical thinking.  Right is center for artistic and musical ability, and creativity.
14.Beneath the gray matter is white matter - myelinated nerve fibers (corpus collosum).
15. Since fibers cross over, left hemisphere controls right half of body. Right hemisphere controls left half of body.
III. Cerebellum
1. Also has 2 hemispheres, with gray matter on outside, white matter on inside and many convolutions.
2. Controls voluntary and some involuntary movements. Works with cerebral cortex to produce smooth coordinated muscle movement. Works with inner ear to maintain balance or equilibrium. Maintains muscle tone and posture.
3. Damage results in jerky movements and staggering. Alcohol affects cerebellum to produce staggering and loss of coordination.
IV. Thalamus 2. Brain - Sagital view: Structures, Ventral view: Hemispheres
1. At top of brain stem.
2. Main sensory relay center between various parts of brain and spinal cord. Interprets all incoming sensory information (except olfactory).
V. Hypothalamus
1. Helps control body temperature, , sleep, appetite, emotions, metabolism. Plays a role in endocrine system.
2. Connected with pituitary gland and regulates it. Is the link between the mind (cerebrum) and body (physiological mechanisms).
VI. Medulla Oblongata
1. Lowest portion of brain.
2. Controls internal organs: heart rate, peristalsis, respiration, secretions from glands, blood pressure, swallowing, coughing, and vomiting.
3. Connects spinal cord with other parts of brain.
VII. Pons
1. Is a bulge on anterior portion of brain stem.
2. Serves as a relay system, linking spinal cord, medulla oblongata, cerebellum, and cerebrum.
VIII. Midbrain
1. Just above pons.
2. Largest part of brain in lower vertebrates.
3. Center for visual and auditory reflexes: pupil reflex, blinking, adjusting ear volume to sound.

IX. Spinal Cord
Figures:
1. Spinal cord cs.
2. Another reflex arc.

1. About 45 centimeters long. Goes from base of brain through vertebral canal in spinal column.
2. It is covered by spinal meninges which are continuous with meninges of brain.
3. Dura matter (though mother) is outer.  The middle is the arachnoid (spider like).
4. The inner is pia matter (delicate mother). Between arachnoid and pia is subarachnoid space which is filled with cerbrospinal fluid.
5. There are 31 paris of spinal nerves extending from the spinal cord as the PNS and 12 pairs of cranial nerves.
6. Composed of H-shaped region of gray matter surrounded by an outer layer of white matter (opposite of brain).
7. The gray matter contains many interneurons and the cell bodies of motor neurons.
8. The cross bar of the H is the gray comissure.
9. In center of H is central canal which is filled with cerebrospinal fluid and connected with 4th ventricle of medulla.
10. Anterior white commissure connects white matter of right and left sides.
11. Anterior gray horns are closer to front of cord. Posterior to rear.
12. Lateral gray horns are on sides of gray matter.
13. White matter is deviled into Posterior, Lateral, and anterior white columns which are composed of myelinated fibers.
14. These white columns are called tracts or fasciculi which run to brain.
15. Ascending tracts are are sensory tracts. Descending tracts are motor tracts.
16. Posterior root (Dorsal) contains Posterior (dorsal) root ganglion of afferent sensory neuron. Dendrite connects with receptors. Axon enters posterior gray horn of spinal cord.
17. Anterior root (ventral) contains efferent motor neuron. Cell body and dendrites are in anterior gray horn.
18. Functions of spinal cord.

a. Connects peripheral NS with brain. Impulses reach spinal cord from sensory neurons and travel up through interneurons to brain. Impulses from brain sent down by interneurons to motor neurons then to muscles and glands.
b. Spinal cord controls certain automatic reflexes.

16. Reflex arc: Another reflex arc.

No conscious control by brain. Occurs is fraction of a second. Association neurons send message to brain telling what happened - "ouch". See figure of spinal cord.