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The Nervous System Nervous System Function Receives & relays information about activities within the body Monitors & responds to internal and external changes Nerve/Brain Facts The brain is made up of approx. 100 billion neurons WE DO NOT USE ONLY 10% OF OUR BRAINS we use 100% of our brain Nerve/Brain Facts (cont.) Your brain weighs approx. 3 lbs Your spinal cord is approx. 43-45 cm long Nerve Impulses travel 395 feet Bundles of nerve fibers What are neurons? Nerve cells that carry messages throughout the nervous system Anatomy of a Neuron Dendrites: receive messages & brings them to cell body Anatomy of a Neuron (cont.) Axon: transmits messages, AKA nerve impulses, away from cell body Anatomy of a Neuron (cont.) Myelin Sheath: membrane surrounding axon • faster nerve conduction Anatomy of a Neuron (cont.) Cell Body: contains organelles •mitochondria, nucleus, etc. Types of Neurons 1. Sensory neurons 2. Motor neurons 3. Interneurons 1. Sensory Neurons Carry impulses to the central nervous system (CNS) EX. From sense organ to brain and spinal cord 2. Motor Neurons Carry impulses from the brain and spinal cord to muscles or glands 3. Interneurons Receives impulse from sensory neurons & carries impulse to motor neurons Interneuron How Neurons Work Neurotransmitters: chemicals that carry nerve impulses / messages between gaps or synapse between neurons Action Potentials Sodium ions rush into cell & Potassium ions rush out Sodium-potassium pump restores balance Transmission of Nerve Impulses Nerve impulses begin when ion concentrations change • Sodium & Potassium Caused by a series of action potentials http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html Nervous System Organization Peripheral Nervous System (PNS) • Autonomic & Somatic Nervous Systems Autonomic Nervous System Controls smooth muscle, organs & glands • Further broken down into parasympathetic & sympathetic Somatic Nervous System Controls voluntary muscle contractions •Under conscious control The Central Nervous System Basic Info 2 Parts: Brain & Spinal Cord • Covered by meniges Processes & sorts info. Controls behavior Sends messages throughout body CNS continued: Brain has 4 main parts: •Cerebrum •Cerebellum •Brain stem •Hypothalmus Brain Anatomy 2 Hemispheres Surface covered with: •gyri (bumps) & sulci (creases) Increase surface area Cerebrum AKA Cerebral Cortex •Control center •Controls: • Memory • Awareness • Thought • Language • Reasoning • Perception • Voluntary movement Cerebrum: Cerebrum named by region: •Frontal Lobe – judgment, impulses •Parietal Lobe – understand & process information Cerebrum continued: •Occipatal Lobe – visually process •Temporal Lobe – controls hearing & recognition Named by bones that cover them! Cerebellum Important for coordination of movement Responsible for body movements, posture, muscle tone, equilibrium Brain Stem Connects the brain to the spinal cord Controls vital life processes •breathing, swallowing, digestion, heart rate & blood pressure Diencephalon Region “interbrain” Consists of the thalamus, subthalamus, hypothalamus, epithalamus Body’s center for emotions & instincts • Body Temp Controls • Thirst • Hunger • Hostility • Pain • Sexual Desire Hypothalmus: Emotions & instincts Controls body temperature, thirst, hunger, hostility, & pain Problems due to Neurotransmitters •Parkinson's Disease: dopamine producing neurons destroyed (lack of movement) •Depression: deficit in serotonin &/or dopamine •Schizophrenia: high level of dopamine Epilepsy •Seizures due to large numbers of impulses sent simultaneously •Affects 1 out of every 200 people in U.S. & 50 million people worldwide Multiple Sclerosis Body attacks myelin sheath Causes nerve impulses to short circuit Studying The Brain CAT Scan: used to locate tumors, damaged regions & blood clots AKA CT Scan – computed axial tomography Studying The Brain (cont.) PET Scan: used to look at brain activity Positron emissions tomography Studying The Brain (cont.) MRI: used to look at brain tissue MRI of an individual with MS Magnetic resonance imaging