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The Nervous System The Nervous System • Gathers information both externally and internally • Transmits this information for processing • Processes the information to determine the best response • Sends information to the muscles, glands and organs so they can respond appropriately The Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) • • • • • Nerves that extend throughout the body • Gathers and delivers information • Works with the Central Nervous System Brain and Spinal Cord Main Control Center Processes information Sends instructions to other parts of the body The Nervous System Structure of the Neuron • Cell body • Dendrites receive and carry information toward the cell body • Axon carries nerve impulses away from the cell body • Glial cells protect, support and assist neurons • In the PNS, the glial cells are Schwann cells – Schwann cells are wrapped by a myelin sheath Neuron The Central Nervous System • Brain Brain Stem: Joins brain to spinal cord Cerebellum: Center of coordination Cerebrum: Largest part of brain, conscious thought Cerebral Cortex: Sensory, motor and association areas • Spinal Cord Relays nerve impulses to and from the brain Controls spinal reflexes Parts of the Brain • 2 cerebral hemispheres – Further divided into lobes • Parietal Lobe – somatic sensory area, impulses traveling from the body’s sensory receptors are localized & interpreted here – Ex. pain, cold, touch • Occipital Lobe – visual area • Temporal Lobe – auditory area and olfactory area • Frontal Lobe – primary motor area – skeletal muscles, also specialized area for fine motor control such as speech Cerebral Cortex – sensory and motor areas Cerebellum • 2 hemispheres – Under occipital lobe of cerebrum • Balance • Coordinates body movements (makes movements smooth) Cerebellum (colored purple) Brain Stem • 3 inches long, diameter of thumb, base of brain • 3 parts: – Midbrain – reflex centers for hearing and vision – Pons – (means bridge), center for breathing – Medulla oblongata – merges into spinal cord • Automatic, homeostatic functions • Such as: heart rate, blood pressure, breathing, swallowing, vomiting and digestion Spinal Cord • Continuation of brain stem • 2-way conduction pathway to and from the brain and a major reflex center • Cushioned and protected by meninges – Meninges = connective tissue membranes • 31 pairs of spinal nerves arise from the spinal cord The Peripheral Nervous System Somatic Nervous System Autonomic Nervous System • Controls voluntary responses of skeletal muscles • May involve some reflex reactions • Controls the activities of smooth muscles, organs, and glands • Divided into: Sympathetic Nervous System which controls the response of the body to stress Parasympathetic Nervous System which controls the functions of the body related to rest and digestion