Ch. 35.3

 Neurons join together to form a complex network; NERVOUS SYSTEM  2 major sections Central nervous system (CNS) Peripheral nervous system (PNS)

 CNS is the CONTROL CENTER of the body (think of a MOTHERBOARD of a computer)  CNS relays messages, processes information, and analyzes information  PNS relays information from environment to the CNS

 Consists of the brain and spinal cord  Skull and vertebrae protect brain and spinal cord Wrapped in MENINGES  connective tissue CEREBROSPINAL FLUID is in between the layers  Acts as a shock absorber and protects the CNS

 Contains ~ 1 billion neurons  Main ‘switch’ in the CNS  CEREBRUM: largest part of the brain Controls voluntary activities of the body Intelligence, learning, and judgment  Broken into 2 hemispheres (connected by the corpus callosum)

 Each half of the brain controls the opposite half  Some studies state that the right side is creativity, left side is more analytic  Outer surface is cerebral cortex (gray matter)  White matter is the inner surface

 Located in the back of the skull  Coordinates and balances the actions of the muscles

 Connects the brain and the spinal cord Pons and medulla oblongata  Acts as a switchboard of information for the brain and rest of the body Blood pressure Heart rate Breathing swallowing

 Found between the brain stem and cerebrum  Thalamus receives messages from the sense organs  Hypothalamus controls recognition of hunger, thirst, fatigue, anger, and body temp

 Main communications link between brain and the body

 Reflexes are processed by spinal cord Quick, automatic response to a stimulus Allows body to respond to danger immediately

 SOMATIC NERVOUS SYSTEM: regulates activities that are CONSCIOUS CONTROL MOVEMENT (motor neurons)

 Regulates involuntary body functions Not under conscious control  Heartbeat  Contraction of smooth muscle  Broken into SYMPATHETIC and PARASYMPATHIC nervous systems Work as opposites of each other (one makes something ‘go,’ the other makes it ‘stop’)