The Central Nervous System The Brain and Spinal Cord The Spinal Cord Main pathway for information connecting brain and PNS Exits the skull through an opening called the foramen magnum Protected by the bony vertebral column (the spine) Two nerve tissue types: white matter and grey matter Grey matter = unmyelinated axons of motor neurons White matter = unmyelinated axons of interneurons Dorsal (“back”) nerve tract relays sensory information into the spinal cord Ventral (“front”) nerve tract relays motor information from the spinal cord to the effectors (muscles and glands) The Brain The human brain has 3 main regions, the forebrain, midbrain and hindbrain. It contains approximately 100 billion neurons, making it the most complex organ in the human body. The cerebrum makes up a large part of the forebrain, and is responsible for determining intelligence and personality, interpreting sensory impulses, and motor functioning. The cerebrum is divided into two hemispheres (the left and the right), which are connected by a thick band of fibers called the corpus callosum. The folded surface of the cerebrum is known as the cerebral cortex. The cerebellum is the largest section of the hindbrain and functions to coordinate movements of muscles and joints, as well as to control balance. The pons (a bundle of fibers that acts as a bridge) connects the cerebellum to the medulla. The medulla, or medulla oblongata, acts as the connection between the central and peripheral nervous systems, as nerve tracts from the spinal cord and higher brain centers run through it. Video: The Brain While watching the video, “The New Living Body: The Brain”, please answer as many of the following questions as possible. 1. What is the name for the wrinkly surface of the brain, which contains 2/3 of the brain’s nerve cells? Answer: The Cortex. 2. Explain what a Magnetic Resonance Imager (MRI) does. Answer: It allows you to look at sections or slices of the brain. 3. Which brain hemisphere controls movement on the left side of the body? Answer: The right hemisphere. 4. Describe the function of the cerebellum. Answer: Involved in controlling limb movement, balance and muscle tone. 5. What is the name for the area of the brain responsible for sight? Answer: The Visual Cortex. 6. How does a young child’s brain develop? Answer: Neural connections are formed in response to stimuli. 7. What does the brain use for energy? Answer: Glucose. 8. Which neurotransmitter is missing in the brain of people who suffer from Parkinson’s Disease? Answer: Dopamine.