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The Nervous System: Communication of the Human Body Sarah White Per. 7 State Standards As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (homeostatic) despite changes in the outside environment. As a basis for understanding this concept: b. Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment. c. Students know how feedback loops in the nervous and endocrine systems regulate conditions in the body. d. Students know the functions of the nervous system and the role of neurons in transmitting electrochemical impulses. e. Students know the roles of sensory neurons, interneurons, and motor neurons in sensation, thought, and response. Purpose - Control Body Functions Central Hypothalamus regulates body temperature Brain sends impulses to body to maintain homeostasis Parts of brain control actions Peripheral Senses send messages along neurons Go to brain and spinal Click picture for Homeostasis Animation cord Messages travel along neurons to destination organs Purpose - Responds to Stimuli Central Recognizes stimuli Decides what to do Sends/Receives messages Peripheral Carries messages to tell brain Carries messages to tell organ systems Purpose - Nerve Impulse Impulse - electrical signals carried by nervous system An impulse begins when a neuron is stimulated by another neuron or by the environment. The Nerve Impulse is like a chain of dominoes Ions pass through the cell membrane, passing the message along Changes the charge with sodium and potassium ions Synapse At the end of a neuron, impulse jumps a gap (synaptic cleft) Neurotransmitter chemicals travel across the gap and attach to the next cell Click on picture and scroll to watch “Neural Transmission” Animation. *All underlined text from textbook Resting Potential - negative charge inside Action Potential - impulse makes it positive Central Nervous System Relays messages, processes information + analyzes information Composed of Brain and Spinal Cord Protected by skull and vertebrae Wrapped in three layers of connective tissue - meninges Cerebrospinal fluid coats the brain and spinal cord to prevent shock and damage Allows nutrients and waste products to move between blood and nervous tissue Brain Cerebrum - largest part Responsible for voluntary activities such as thought and decisions Divided into right and left halves connected by corpus callosum (band of tissue) Each half receives and sends messages to the other side of the body Right is said to be more creative and artistic Left may be more controlling of math and analysis Divided into lobes named for the parts of the skull Contains approximately 100 billion neurons! Brain Cerebrum made of two surfaces Outer surface called cerebral cortex Gray matter - densely packed nerve cell bodies Interprets messages from senses and controls body movements Inner surface White matter - made up of bundles of axons with myelin sheaths Brain Cerebellum - second largest Located at back Coordinates and balances actions of muscles Brain Stem - connects brain and spinal cord Pons Pons & Medulla oblongata Regulate flow of information between brain and body Control blood pressure, heart rate, breathing Thalamus - receives Medulla Oblongata messages from sense organs and sends to proper area of brain Hypothalamus - recognition and analysis of hunger, thirst, fatigue, anger, temperature Spinal Cord Thirty-one pairs of QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. nerves branch out Reflexes - quick, automatic response to stimulus are taken care of by the spinal cord The messages for reflexes don’t go to the brain…Why? It takes too long Peripheral Nervous System Nerves and cells not part of the brain or spinal cord Cranial nerves - stimulate head and neck Spinal nerves Ganglia - nerve cell bodies Sensory - takes messages from sense organs to brain/spinal cord Motor - takes messages from brain/spinal cord to muscles and glands Two divisions of peripheral nervous system Somatic Autonomic Somatic Nervous System Controls activities you are aware of Movement of muscles connected to bones Uses motor neurons Also involves reflexes Reflex arc - the path an impulse takes from the sensory receptor -> body part that responds Autonomic Nervous System Controls involuntary movements Regulates heartbeat and digestion Sympathetic and Parasympathetic Branches Both control opposite actions on the same organ systems Similar to Gas/Brake Pedals in a car Neurons Cell Body - consists of nucleus and most of the cytoplasm Dendrites - spread from the cell body Most of the activity takes place here Carry impulses from the environment or other neurons toward the cell body Axon - long fiber Carries impulses away from cell body Ends in axon terminals Myelin Sheath - insulating membrane Surrounds an axon Nodes - gaps where the axon membrane is exposed Impulses jump from one node to the next Increases the rate at which the impulse can go Neurons Sensory - carry impulses to the brain and spinal cord from the sense organs Ex: recognize a sound, movement, taste, texture, smell Motor - carry impulses away from the brain to cause a reaction in another organ Ex: move a muscle, produce enzymes in glands Interneurons - connect Interneuron Sensory Motor sensory and motor neurons, pass impulses in between the two types Sensory Receptors NOT the typical 5 Senses All send messages to the brain Pain receptors Located throughout the body except the brain Respond to chemicals released by damaged cells Pain usually indicates danger, injury or disease Thermoreceptors Located in skin, body core, and hypothalamus Respond to changes in temperature Sensory Receptors Mechanoreceptors Located in skin, skeletal muscles, and inner ears Respond to touch, pressure, stretching of muscles, sound, and motion Chemoreceptors Located in nose and taste buds Respond to chemicals in external environment Photoreceptors Located in eyes Respond to light Malfunction Alzheimer’s Disease Mental function deteriorates, but motor skills are kept intact Results in restricted memory, thoughts, and behavior, confusion, impaired judgment, communication, and visuospatial skills, decrease in speaking skills, etc Production of some brain chemicals is reduced Cause unknown, but Age and family history Certain genes Abnormal protein deposits in brain are suspected causes Malfunction Charcot-Marie-Tooth Disease (CMT) Patients gradually lose feeling in their legs, arms, and extremities (hands, feet) Disorder in the peripheral nerves that control sensory info in the muscles Is hereditary Normally not life-threatening until it affects breathing Symptoms include extreme foot deformities such as a very high arch, clawed toes, or very flat feet, problems with balance, walking, or running, and very thin lower legs Promotion Eat healthy foods with lots good fat, Vitamin D, and Vitamin B12 Wear a helmet and seat belt to prevent paralysis or brain damage Avoid drugs, alcohol, and tobacco Take time to relax Use your brain! Write (pencil and paper) or draw with precision to ensure best condition