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Nervous System - Period 3 BY KATE, SIERRA, KATHRYN, AND CARSON WHAT IS THE NERVOUS SYSTEM AND WHAT ARE ITS FUNCTIONS? • Complex series of nerves and specialized cells (neurons or nerve cells) that transmit electrical signals between parts of the body • Similar to electrical wiring • Takes in and processes information through the senses and triggers reactions • Coordinates muscle activity, monitors organs, constructs and processes data received from senses and initiates actions • Metabolic processes also included ORGANS AND THEIR FUNCTIONS • Brain and spinal chord – analyze and respond to information accordingly; sends signals to rest of the body; controls simple musculoskeletal reflexes • Eyes – send information to the brain and convert into vision • Ears – send information to brain and convert it into sounds • Sensory organs of taste (taste buds, etc.) – send information to the brain and convert into taste • Sensory organs of smell - send information to the brain and convert into smell • Sensory receptors located in the skin, joints, muscles, and other parts of the body – send information to the brain and convert into feelings and response such as touch or heat HOW DOES THE NERVOUS SYSTEM WORK? THE NERVE AND ITS PARTS A. CELL BODY - contains the nucleus and much of the cytoplasm; most of the metabolic activity of the cell, including the generation of ATP and synthesis of protein. B. DENDRITES - Short branch extensions spreading out from the cell body. Dendrites receive STIMULUS and carry IMPULSES from the environment or from other neurons towards the cell body C. AXON - Long fiber that carries impulses away from cell body. Each neuron has only ONE axon. The axon ends with AXON TERMINALS TYPES OF NEURONS Sensory neuron Length of Fibers Long dendrites and short axon Location Cell body and dendrite are outside of the spinal cord; the cell body is located in a dorsal root ganglion Function Conduct impulse to the spinal cord Interneuron Motor Neuron Short dendrites and short or long axons Short dendrites and long axons Entirely within the spinal cord or CNS Dendrites and the cell body are located in the spinal cord; the axon is outside of the spinal cord Interconnect the Conduct impulse to an sensory neuron with effector (muscle or appropriate motor gland) neuron • Axon is covered by lipid layer called MYELIN SHEATH that speeds up transmission of messages • Axon terminals may come into contact with dendrites, effectors, or receptors to pass on messages • Receptors are in sense organs; effectors are muscles or glands that coordinate a response • Impulses are passes from one cell to another through SYNAPSES (gap between axon of one neuron and dendrite or cell body of another neuron) • Chemicals, or neurotransmitters, bridge this gap to transfer information to each other through electrical signals received from receptors or effectors; neurotransmitters are released when an electrical impulse reaches the end of a neuron QUICK SUMMARY • Nerve has a cell body with multiple extensions • The shorter extensions (dentrites) act like antennae and receive signals • The longer extension (axon) passes along signals to other cells which are relayed to the brain • Synapses and neurotransmitters bridge the gap between cells to relay messages to the brain TWO MAIN PARTS OF THE SYSTEM CENTRAL PERIPHERAL • Composed of the brain and spinal Composed of everything but the brain and spinal chord chord Purpose: to connect the limbs and • Purpose: to collect information organs to the central nervous and respond accordingly system • Living nervous tissue has • Consists of 12 pairs cranial nerves consistency of jelly and must and 31 pairs of spinal nerves, some are exclusively sensory have special protection from damage • Sensory cells carry messages to the • Interprets messages from the peripheral nervous system central nervous system and motor cells carry the signal from the CNS to the organs, muscles, etc. THE NERVOUS SYSTEM AND OTHER SYSTEMS BODY SYSTEM INTERACTION • Cardiovascular • The brain receives information about blood pressure • Endocrine • Lymphatic • Respiratory • Digestive through baroreceptors; regulates heart rate and blood pressure • Hormones provide information to affect neural processing; controls pituitary gland and other glands • Brain stimulates defense mechanisms against infection • Brain monitors respiratory volume, blood-gas levels, and respiratory rate • Digestive system provides building blocks for neurotransmitters; sends information relating to thirst or hunger; controls muscles for eating and waste removal THE NERVOUS SYSTEM AND OTHER SYSTEMS WHAT ARE RECEPTORS AND WHAT ARE THEIR FUNCTIONS? • Receptor: an organ or cell that responds to an external stimulus and transmits a signal to a sensory nerve • Interoceptors-transmits pulses to detect stimuli inside of the body • Exteroceptors- similar to interoceptors but detects stimuli outside of the body • Chemoreceptors-detects the concentration of oxygen in the blood stream • Photoreceptors-respond to the presence of light • Mechanoreceptors-responds to mechanical pressure or distortion, touch • Thermoreceptors- responds to absolute and relative changes in temperature DISEASES THAT AFFECT THE NERVOUS SYSTEM MULTIPLE SCLEROSIS • Affects brain and spinal cord • Myelin sheath is damaged (material that surrounds and protects nerve cells) • Slows or blocks messages between brain and body • Symptoms include: weak muscles, difficulty with coordination or balance, difficulty thinking or remembering, feelings of numbness or prickling • Cause is unknown; disease can be mild to severe depending on the affected person • Currently no cure but medicine and physical therapy can manage and lessen symptoms PARKINSON’S DISEASE • Malfunction of vital nerve cells, mostly in the substanita nigra portion of the brain • Malfunctioning neurons die and release dopamine (a chemical that messages the part of the brain that controls movement and coordination) • Progressive movement disorder, which means symptoms continue and worsen over time • As the disease worsens, dopamine levels decrease and the person loses control of their movements • Symptoms include: tremor, slowness of movement, rigidity, poor balance or posture • Cause is unknown; no cure currently but medication and surgery can manage symptoms HOW DOES THE NERVOUS SYSTEM HELP MAINTAIN HOMEOSTASIS? • The central nervous system is comprised of the brain and the spinal cord, whereas the peripheral nervous system is composed of the nerve extensions beyond those central pathways. Both, when combined, interconnect all of the parts of the body and allow for the processes creating homeostasis to occur. The autonomic nervous system regulates involuntary bodily functions. Without interpretation and responses to sensations such as becoming too warm, the body would become imbalanced. BIBLIOGRAPHY • http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024762/?figure=1 • https://faculty.washington.edu/chudler/nsdivide.html http://www.hopkinsmedicine.org/healthlibrary/conditions/nervous_syst em_disorders/overview_of_nervous_system_disorders_85,P00799/ http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024762/ http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0025454/ • http://www.livescience.com/22665-nervous-system.html • http://www.ninds.nih.gov/disorders/parkinsons_disease/parkinsons_dis ease.htm • https://faculty.washington.edu/chudler/organ.html • http://leavingbio.net/the%20nervous%20system_files/the%20nervous% 20system.htm