The Nervous System

1. The Nervous System The Senses and Drugs

2. Sensory Receptors • Are specialized neurons that react directly to stimuli from the environment, including light, sound, motion, chemicals, pressure, and changes in temperature • There are 5 general categories of sensory receptors

3. Pain receptors • Located throughout the body except in the brain • Respond to chemicals released by damaged cells

4. 2. Thermoreceptors • Located in the skin, body core, and hypothalamus • Detect variations in temperature

5. 3. Mechanoreceptors • Found in the skin, skeletal muscles, and inner ear • Are sensitive to pressure, touch, stretching of muscles, sound and motion

6. 4. Chemoreceptors Located in the nose and taste buds Are sensitive to chemicals in the external environment

7. 5. Photoreceptors • Found in the eye • Are sensitive to light

8. Vision • The iris controls the size of the pupil, which allows the correct amount of light to enter the eye • The lens adjusts shape to focus on near or far objects; it focuses light onto the retina • The retina contains the photoreceptors that convert light energy into nerve impulses

9. Vision • The retina has both rod and cone photoreceptors • Rods: are extremely sensitive to light, but don’t distinguish color • Cones: are less sensitive to light than rods, but responds to light of different colors

10. Duel roles of the human ear • The human ear is responsible for both hearing and balance

11. Hearing • Sound is simply vibration in the air, which the ear can interpret both pitch and loudness

12. Steps of Hearing 1. vibration enter the auditory canal 2. vibration cause the tympanum to vibrate 3. vibrations are passed along by the hammer, anvil and stirrup to the oval window 4. vibration on the oval window create pressure waves in the fluid filled cochlea 5. pressure waves only occur in certain regions in cochlea, which allow brain to interpret loudness and pitch

13. Balance • Semicircular canals: are located in the inner ear and are responsible for monitoring the position of your body • There are 3 half circular canals, arranged on different planes to sense all motion types

14. Smell and Taste The sense of smell and taste is actually the body detecting chemicals Chemoreceptors line the nasal passageway and also the tongue (taste buds) These senses are closely linked

15. Touch • The sense of touch is not located in a particular place • All regions in the skin are sensitive to touch, making it the largest sense organ • Skin contains sensory receptors that respond to temperature, touch and pain • Touch receptors density varies with regions of the body • Hands have many, back has fewer

16. Drugs By definition is any substance (besides food) that changes the structure and function of the body All drugs, including legal ones, have great potential to harm the body if used improperly

17. Stimulants • Are a class of drugs which increase the actions regulated by the nervous system • Increase heart rate, blood pressure, and breathing rate • Also increase the release of some neurotransmitters at some synapses in the brain • The release leads to a feeling of energy and well being • When effects wear off, user feels fatigue and depressed • Long term use problems include circulatory problems, hallucinations, and psychological depression

18. Depressants • Are a class of drugs that decrease the function regulated by the brain • Slow down heart rate and breathing rate, lower blood pressure, relax muscles and relieve tension • Prevents some neurons from transmitting impulses to the brain • Calms the part of the brain that senses fear and anxiety • If paired with alcohol, results are often fatal

19. Cocaine • Acts on the neuron in the brain responsible for pleasure • Causes a sudden release of the neurotransmitter DOPAMINE • Usually released in small amounts when a basic need it met, like hunger and thirst • Produces an intense sense of satisfaction, followed by depression • Is a stimulant and usually damages the heart

20. Opiates • Mimic natural chemicals in the brain known as endorphins, which normally help to overcome sensations of pain. • Provide a sense of pleasure and release from pain initially When a user stops, they feel intense pain and sickness because the body cannot produce enough endorphins naturally

21. Marijuana Most widely abused drug Active ingredient is THC Smoking is worse for the lungs than cigarettes Long term use leads to memory loss, inability to concentrate, and in males, reduced levels of testosterone

22. Alcohol Most widely abused legal drug Is a depressant Slow reflexes, disrupts coordination, and impairs judgment 40% of all fatal car accidents involve alcohol If consumed during pregnancy can cause birth defects called Fetal Alcohol Syndrome Long term lead to liver failure

23. Drug Abuse • Is defined as the intentional misuse of any drug for nonmedical purposes • Addiction: is an uncontrollable dependence on a drug • Both physical and psychological