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Nervous System RQ 1. 2. 3. 4. What does white matter have that gray does not? Which two ions are necessary for nerve impulse transmission? Your senses of taste and ______ are received by chemical receptors. Which class of drugs slows the CNS? 1. What is the basic unit of the nervous system? List and describe the three main categories. 1. 2. 3. A “neuron”, or nerve cell is the basic unit Sensory neurons: carry impulses from the body to the brain & spinal cord Interneurons: found within the brain & spinal cord; process impulses & pass response impulses to motor neurons Motor neurons: carry response impulses away from the brain or spinal cord to a muscle or gland 2. How many categories of neurons are there, and what are their jobs? 3. How does your nervous system relay an impulse? Impulses (messages) travel electrically within a neuron, and chemically between neurons Sensory information sensory neurons spinal cord brain motor neurons movement/reaction 4. Describe a neuron at rest. Neurons have three parts: Dendrites – receive impulses from other neurons Cell body – process the impulses Axon – send impulses to other neurons, muscles or glands At rest: The neuron is “polarized” with higher [K+] inside the membrane and higher [Na+] outside of the membrane 5. How is an impulse transmitted? 1. 2. 3. A stimulus excites a neuron and Na+ channels in the cell membrane open & Na+ rushes in This depolarizes the cell (which was negatively charged compared to it’s surroundings) This depolarization travels down the axon to the next neuron 6. What is the difference between the white and gray matter? White matter (much of the brain & spinal cord) Axons that have “myelin” insulating the plasma membrane Myelin hinders the movement of ions, which move fast down the axon’s length (increasing the speed of reactions Gray matter (interior of brain) Neurons whose axons are not myelinated 7. Describe the connections between neurons. 1. 2. 3. The space between the axon of one neuron and the dendrite of the next neuron is called a synapse Neurotransmitters are the chemicals that diffuse across the synapse to link neurons Enzymes break down the neurotransmitters after the impulse is relayed 8. How do the central and peripheral nervous systems work together? Central (CNS) – the brain & spinal cord Coordinates all of your body’s activities Receives & processes info from the PNS Peripheral (PNS) – everything else Senses the environment and with direction from the CNS responds to that environment 9. Overview the anatomy of the brain. Cerebrum 1. Two connected hemispheres Controls conscious activities, language, skeletal muscles & senses It is folded and groovy to increase surface area Cerebellum 2. Back of your brain, all foldy looking Controls balance, posture, coordination Brain stem 3. Made up of medulla oblongata, pons, and midbrain MO controls involuntary stuff like breathing & heart rate Pons & midbrain connect the different parts of the brain 10. What does your peripheral nervous system do? PNS carries impulses to the CNS and performs the reaction necessary (sensory interneuron motor) Two divisions: 1. 2. Somatic NS Autonomic NS 11. Describe the somatic nervous system and what it does. Made up of 12 pairs of cranial nerves and 31 pairs of spinal nerves, all bundled together Usually in charge of voluntary reactions to stimuli, like skeletal muscle movement Exception: reflexes (next slide) 12. What are reflexes? Occur within the somatic NS It is an automatic, unconscious response to a stimulus The sensory information goes to the spinal cord or brain stem and is immediately dealt with; the cerebrum gets the information after the reflex has occurred Why would this happen? 13. Your autonomic nervous system is divided into two parts. Name them and describe what they do. In charge of the involuntary reactions (not under conscious control) Sympathetic NS Control during stress Causes the release of epinephrine & norepinephrine that causes “fight or flight” Parasympathetic NS Controls during rest Calms you down after stressful situations 14. Describe the chemical senses of smell and taste. Smell The chemical receptors in your nose are hairlike nerve endings that signal the brain about certain chemicals The brain processes this information as a particular smell Taste Chemicals dissolve in saliva and contact the taste buds (sensory receptors) You have about 10,000 taste buds Tastes are sour, sweet, bitter, salty, and most recently umami (MSG) and fat! 15. Describe the anatomy of an eye and how this allows you to see. Retina: thin layer of tissue at the back of the eye that has light receptors and sensory neurons Rods cells adapted to see in dim light Cones adapted for bright light & colors Light enters through the pupil It is focused by the lens The focused picture strikes the retina which comes together to form the optic nerve, which sends the information to the back of the brain 1. 2. 3. 16. How are your senses of hearing and balance related? What structures are associated? Both are examples of how we sense mechanical stimulation Both use structures of the ear Hearing 1. Sound causes vibrations (sound waves) which strike the tympanic membrane 2. These vibrations cause the middle ear to vibrate, and this vibration travels along, deeper into the ear 3. Vibration reaches the fluid in the cochlea which causes the hair cells (sensory receptors) to produce electric impulses 4. These travel along the auditory nerve to the brain where the sound is interpreted Balance 1. Fluid-filled semicircular canals in the inner ear are lined with hair cells also 2. When you tilt your head it bends the hairs sending the impulse to your brain 17. How does your sense of touch work? Describe what kinds of receptors your body has. Sensory receptors in the dermis respond to mechanical stimuli Temperature Pressure Heat receptors are deep in the dermis Cold receptors are close to the surface Light pressure sensors found especially in the fingertips, palms, eyelids, lips, and tip of the tongue Heavy/deep pressure sensors found in muscle, joints, some organs, palms and soles of feet Pain (nocireceptors) Found everywhere except brain 18. What is a drug? How does it interact in the brain or endocrine system? Drug – any chemical that affects the body’s functions Most interact with neurotransmitter or hormone receptors on cells 19. How do pain relievers work on your body? What is an example? Two ways pain relievers (analgesics) work: 1. 2. Inhibit the receptors that initiate the pain impulse (ex: aspirin) Narcotics manipulate the CNS that receives the impulses (ex: opiates) 20. Describe how drugs can also be used to treat circulatory and nervous disorders. Cardiovascular drugs… High blood pressure (norvasc, lopressor) Normalize heartbeat (Diltiazem) Increase pumping capacity Enlarge small blood vessels Prevent blood clots (heparin, coumadin, warfarin) Nervous disorders… Stimulants (amphetamines) Increase wakefulness and alertness Depressants (sedatives) Encourage calmness and sleep; reduce anxiety 21. What happens when people misuse drugs? How do addiction, tolerance, and withdrawal fit into this? Can cause death Misuse… Taking someone else’s prescription Not taking the drug as prescribed Mixing contraindicated medicines Abuse… The inappropriate use of a drug for non-medical purposes Can be illegal or excessive use of legal drugs Addiction – when a person psychologically needs a drug to function normally; or when a person’s body has developed a chemical need for a drug Tolerance – when a person needs more and more of a drug to get the same effect Withdrawal – when a person stops taking the drug and becomes ill 22. Briefly describe stimulants, depressants, narcotics and hallucinogens. How do these different classes of drugs affect the body? Stimulants: increase CNS activity Depressants: slows down the CNS activity Alcohol & barbiturates Relieve anxiety, produce sedation Can cause brain damage and liver cirrhosis; reduced circulatory and respiratory function Narcotics: opiates (most abused is heroin) Caffeine, nicotine, cocaine Can cause alertness, nervousness, anxiety and possible convulsions Acts directly on the CNS Slows breathing, lowers heart rate, tolerance develops quickly Hallucinogens: alter perceptions of the CNS Disorientation, high blood pressure, body temperature, even convulsions 23. Why is breaking a drug habit difficult? How do smokers try to avoid nicotine withdrawals? Addiction can be both physiological (body is dependent) and psychological (you feel like you need it) Replacement therapies can help addicts Nicotine patches and gum for smokers Methadone for morphine and heroin addicts