1. Chapter 21 Control and Coordination

2. Section 1- The Nervous System Homeostasis –The regulation of steady, life-maintaining conditions inside an organism, despite changes in its environment. Neurons –Working unit of the nervous system; a nerve cell Neurons consist of a cell body, axons, and dendrites. Dendrite –Part of neuron; they receive messages and send them to cell body. Axon –Part of neuron; it carries messages away from cell body. Synapse –Small space between neurons

3. Motor Neurons –Conduct impulses from brain or spinal cord to body parts Sensory Neurons –Receive info. and send impulses Interneurons –Relay impulses to motor neurons Types of Nerve Cells

4. The Brain Coordinates all of your body activities. Cerebrum –Thinking takes place –Largest part of your brain –Interprets impulses from the senses Cerebellum –Part of the brain that coordinates your muscle movement. Helps maintain balance. Brain stem –Connects brain to the spinal cord –Includes the midbrain, pons, and the medulla –Medulla- involuntary actions (heartbeat, breathing and digestion) –Midbrain & pons- acts as pathways that connect various parts of the brain with each other

5. Spinal cord –Controls reflex responses –Ex. Withdrawing your hand from a hot stove, your foot from a sharp piece of glass, putting your hands out in front of you to stop a fall.

6. Central Nervous System (CNS) –Made up of the brain and spinal cord Peripheral Nervous System (PNS) –Made up of nerves outside the central nervous system. Connects the brain and spinal cord to other body parts. Sensory neurons send impulses to the brain or spinal cord. 2 Major Division of PNS –1) Somatic 2) Autonomic –Somatic- Voluntary Actions –Autonomic- Involuntary Actions Reflex –Involuntary, automatic response to a stimulus Stimulus –Change that causes a response in your body

7. What steps happen when you run an iron over your hand accidentally? 1. You aren’t paying attention when you run the iron over your hand. 2. Sensory neurons in your hand send messages to interneurons. 3. Interneurons relay impulses to motor neurons 4. Motor neurons relay impulses to muscles of your hand. 5. Muscles of your hand contract, responding to the impulses. 6. You pull your hand away from the iron and scream.

8. Caffeine is a stimulant –A drug that speeds up the activity of the central nervous system. –Increases heart rate –Causes restlessness and insomnia –Causes kidneys to produce more urine Alcohol is a depressant –A drug that slows the activities of the central nervous system. –Impairs judgment –Destroys brain and liver cells Drugs and the Nervous System

9. Section 2- The Senses Sense organs intercept different forms of energy, which are then converted into impulses by the nervous system. Your senses work together –Maintain homeostasis within your body. Senses 1) Vision 2) Hearing 3) Smell 4) Taste 5) Touch

10. Vision How do you see???? –Light enters the eye – cornea –Next passes through the lens –Lens directs light into the retina Tissue at back of eye that is sensitive to light energy –Rods (respond to dim light) and cones (respond to bright light and color) are found in the retina. –Light energy stimulates an impulse –Optic Nerve- Carries impulses from the retina to the brain. http://glencoe.mcgraw-hill.com/sites/dl/free/0078617022/161752/00053402.html

13. Cornea Lens Optic Nerve Retina Rods and Cones

14. Hearing Sound energy is to hearing as light energy is to vision. When an object vibrates, sound waves are produced. Outer Ear –Intercepts sound waves and funnels them into the ear canal

15. Middle Ear –Eardrum vibrates –Contains hammer, anvil, and stirrup Inner Ear –Cochlea- fluid-filled structure in the inner ear –Causes electrical impulses to be sent to the brain by a nerve

16. Smell Olfactory cells –Nerve cells in the nose stimulated by molecules –Kept moist by mucus

17. Taste Taste buds –Major sensory receptors on the tongue In order to taste something, it has to be dissolved in water. Saliva begins this process. Smell and taste are related! –Olfactory cells are stimulated through the back of your throat.

18. Other Sensory Receptors Skin – sensory receptors are located throughout your skin. (Fingertips) –You can tell whether an object is smooth or rough, hot or cold, hard or soft.