Nervous System RQ

1. Nervous System RQ • 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?

2. 1. What is the basic unit of the nervous system? List and describe the three main categories. • 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 

3. 2. How many categories of neurons are there, and what are their jobs?

4. 3. How does your nervous system relay an impulse? • Impulses (messages) travel electrically within a neuron, and chemically between neurons • Sensoryinformation  sensory neurons spinal cord  brain  motor neurons  movement/reaction

5. 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 

6. 5. How is an impulse transmitted? • 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 

8. 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 

9. 7. Describe the connections between neurons. • 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 • Enzymesbreak downthe neurotransmitters after the impulse is relayed 

11. 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 

13. 9. Overview the anatomy of the brain. • Cerebrum • Two connected hemispheres • Controls conscious activities, language, skeletal muscles & senses • It is folded and groovy to increase surface area • Cerebellum • Back of your brain, all foldy looking • Controls balance, posture, coordination • Brain stem • 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 

16. 10. What does your peripheral nervous system do? • PNS carries impulses to the CNS and performs the reaction necessary (sensory  interneuron  motor) • Two divisions: • Somatic NS • Autonomic NS 

18. 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) 

19. 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? 

21. 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 

24. 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! 

27. 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 

29. 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 • Sound causes vibrations (sound waves) which strike the tympanic membrane • These vibrations cause the middle ear to vibrate, and this vibration travels along, deeper into the ear • Vibration reaches the fluid in the cochlea which causes the hair cells (sensory receptors) to produce electric impulses • These travel along the auditory nerve to the brain where the sound is interpreted Balance • Fluid-filled semicircular canals in the inner ear are lined with hair cells also • When you tilt your head it bends the hairs sending the impulse to your brain 

32. 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 • Heat receptors are deep in the dermis • Cold receptors are close to the surface • Pressure • 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 

34. 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 

36. 19. How do pain relievers work on your body? What is an example? • Two ways pain relievers (analgesics) work: • Inhibit the receptors that initiate the pain impulse (ex: aspirin) • Narcotics manipulate the CNS that receives the impulses (ex: opiates) 

37. 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 

38. 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 

39. 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 

40. 22. Briefly describe stimulants, depressants, narcotics and hallucinogens. How do these different classes of drugs affect the body? • Stimulants: increase CNS activity • Caffeine, nicotine, cocaine • Can cause alertness, nervousness, anxiety and possible convulsions • 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) • 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 

42. 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 