DIVISIONS OF THE NERVOUS SYSTEM  Central Nervous System: Control center of the body  Consists of the brain and spinal cord  Function: To relay messages, process, compare, & analyze information.  Peripheral Nervous System  Consists of all the nerves and associated cells not part of the brain & spinal cord.  Including cranial and spinals nerves & ganglia (collection of nerve cell bodies)

CENTRAL NERVOUS SYSTEM  Consists of the brain & spinal cord.  Brain is the main switching unit of the CNS; impulses originate here  Spinal cord links brain & rest of the body  The brain consists of:  35 billion neurons w/ a mass of 1.4 kilograms  meninges- 3 layers of connective tissue connecting one tissue to another  pia mater- innermost layer, covering and binding to the surface of the brain  fibrous w/ many blood vessels carrying food and OXYGEN to spinal cord  dura mater- outer most layer; thick connective tissue  arachnoid- thin, cobweblike layer between the two maters  cerebrospinal- between the pia mater & arachnoid, fluid-shock absorber  Spinal cord: cm in length, protected by bone (vertebral column), menings, and cerebrospinal fluid.

THE CEREBRUM  The largest and most prominent part of the brain.  Controls all voluntary activities of the body.  Site of intelligence, learning, and judgment.  Corpus callosum- connects the right and left hemispheres together.  The many folds of the brain increase the S/A.  Lobes- Divisions of the hemispheres named for the bones they cover.  Each hemisphere controls the other side of the body.  Right shows creativity & artistic; Left shows analytical & mathematical  THE CEREBRAL CORTEX:  Outer surface of gray matter composed of densely packed nerve cells  Cerebral Medulla- Inner surface of white matter made of bundles of myelinated axons.

CEREBELLUM & BRAINSTEM  CEREBELLUM  2 nd largest part of the brain, located at the back of the skull.  Coordinates & balances the actions of the muscles  Damages causes muscles weakness & lack of coordination.  THE BRAINSTEM  Connects the brain to the spinal cord.  Medulla oblongata- controls involuntary actions; breathing, swallowing, etc  Contains cells of the reticular activating system; alerts & awakens brain  Pons- The link between the cerebral cortex & the cerebellum.  Midbrain- smallest division of the brainstem; controls hearing and vision.

THALAMUS & HYPOTHALAMUS  Found between the brainstem and cerebrum.  Thalamus: Gray matter; switching station for sensory input.  Each sense, except smell, channels its nerves through the thalamus.  Hypothalamus: Below thalamus, controls hunger, thirst, fatigue, anger, & body temperature.  FUNCTIONS OF THE BRAIN  See fig  Performed in the gray matter of the cerebral cortex.  Penfield’s experiments: brain senses no pain, so he could stimulate the brain w/ weak electrical signals while the patient was awake.  Not the whole story but; Sensory neurons synapse in spinal cord, neurons in spinal cord relay to thalamus, then relays to sensory cortex.

BRAIN WAVES  Brain Waves  If voltage electrodes are placed on the scalp there is a weak electrical signal  Electroencephalogram (EEG) gives general idea of the brain’s activity  Sleep: Cerebral cortex is at the lowest possible level in which a person is in a state of unconsciousness & can be awakened by normal sensory stimulation.  MEMORY  Short term: Generally vanishes in a few days depending on its importance  Thought to be stored in the cerebral cortex  Long term: Permanent memories, may fade with time.  Could be stored in the total of the brain instead of just one region.  THE SPINAL CORD: Communication link between the brain and PNS  Regulates reflexes: the simplest response to a stimuli  Two types of tissues: central is gray matter & outer is white matter