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Download I. The Nervous System
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Nervous System Integumentary System Skeletal System Muscular System Circulatory System Respiratory System Digestive System Endocrine System Reproductive System Excretory System Lymphatic/Immune Systems 1.What is this? 2. How many do you think you have? 3. What are the main parts? The Nervous System I. The Nervous System A.The Nervous System 1. Functions a. Controls and coordinates functions throughout the body and responds to internal and external stimuli B. Neurons 1. Cells that transmit electrical signals in the Nervous System, functional unit of nervous system Neuron Factoids • Your brain has as many cells as there are stars in the milky way • Electrical messages in neurons travel about 220 miles/hour • It is not true that you use only 10% of your brain • 100 billion neurons Neuron C. Types of neurons: 1. sensory- carry impulses from the sense organs to the spinal cord and brain. 2. motor- carry impulses from the brain and spinal cord to muscles and glands. 3. interneurons- connect sensory and motor neurons and carry impulses between them. Structure of Neuron D. Structure of neurons: 1. DENDRITES- carries impulses toward the cell body. 2. CELL BODY a. nucleus- control center c. mitochondria- energy (ATP synthesis) d. Nissi Bodies- contain rough ER , transport substances, contain ribosomes which make protein e. neurofibrils- protein filament structures that make-up cytoskeleton 3. AXON- carries impulses away from the cell body. a. Schwann cells- accessory cells that make myelin sheath b. myelin sheath- lipids that cover part of some axons, conducts signal faster c. nodes of Ranvier- breaks in myelin sheath, leave cell exposed to access ions needed for impulse 4. Terminal End Bulb– at the end of the axon, transmits signals OUT of axon SYNAPSE- the location at which a neuron can transfer an impulse to another cell. (The gap between neurons) II. Divisions of the Nervous SystemA. The central nervous system (CNS)- is made up of the brain and the spinal cord. 1. Functions: a. sends messages b. processes information c. analyzes information B. The peripheral nervous system (PNS)transmits impulses from sense organs to the central nervous system and back to muscles or glands. 1. Afferent/sensory division- sends impulses from the sensory neurons to the CNS. 2. Efferent/motor division- sends impulses from the CNS to muscles and glands. a. somatic- control voluntary actions. b. autonomic- regulates activities that are automatic. Cross Section of the Spinal Cord The Spinal Cord Section 35-3 Gray matter Spinal nerve Central canal White matter Meninges III. The Senses A. Sensory receptors- are neurons that react to stimuli in the environment. These receptors send impulses to the central nervous system. 1. 5 types of sensory receptors: a. pain receptors- respond to pain. b. thermoreceptors- respond to temperature. c. mechanoreceptors- respond to pressure. d. chemoreceptors- respond to chemicals. e. photoreceptors- respond to light. Figure 35-15 The Ear Section 35-4 Anvil Stirrup Hammer Oval window Semicircular canals Cochlear nerve Cochlea Bone Auditory canal Tympanum Round window Eustachian tube The Senses of Smell and Taste Section 35-4 Olfactory (smell) bulb Taste sensory area Olfactory nerve Thalamus Cerebral cortex Smell receptor Nasal cavity Smell sensory area Taste bud Taste pore Taste receptor Sensory nerve fibers IV. Vision A. The sensory organ responsible for vision is the eye. 1. Pupil- is a small opening at the front of the eye. 2. retina- contains photoreceptors a. rods- sensitive to light, but don’t distinguish different colors b. cones- less sensitive to light, but do respond to light of different colors. Figure 35-14 The Eye Section 35-4 Vitreous humor Muscle Lens Fovea Aqueous humor Cornea Pupil Optic nerve Iris Blood vessels Ligaments Retina Choroid Sclera V. Drugs and the Nervous System A. Drug- any substance, other than food, that changes the structure or function of the body. Several types of drugs affect the nervous system. 1. Stimulants- increase heart rate, blood pressure and breathing rate. 2. Depressants- decrease heart and breathing rates, lower blood pressure, relax muscles and relieve tension. 3. Opiates- act like natural brain chemicals (endorphins). Commonly Abused Drugs Section 35-5 Drug Type Medical Use Examples Effects on the body Stimulants Used to increase alertness, relieve fatigue Amphetamines Increase heart and respiratory rates; elevate blood pressure; dilate pupils; decrease appetite Depressants Used to relieve anxiety, irritability, tension Barbiturates Tranquilizers Slow down the actions of the central nervous system; small amounts cause calmness and relaxation; larger amounts cause slurred speech and impaired judgement Opiates Used to relieve pain Morphine Codeine Act as a depressant; cause drowsiness, restlessness, nausea 4. Marijuana- can cause memory and concentration problems. 5. Alcohol- is a depressant that slows down the rate at which the central nervous system functions. VI. Drug abuse- is the intentional misuse of any drug for non-medical purposes. A. Addition- is an uncontrollable dependence on a drug.