Chapter 9: Nervous System -allows feeling, thinking, moving, and awareness -coordinates all body functions to maintain homeostasis and enables the body to respond to changing conditions 1. Nerve cells are also known as _neurons, which are the structural and functional units of the nervous system. 2. Neurons transmit information by electrochemical changes_ called nerve impulses to other neurons and cells. 3. Bundles of axons are known as nerves__. 4. Nervous system support cells are _neuroglial cells____________, which function to support, insulate, and provide nutrients__. 5. Organs of the central nervous system are brain and spinal cord. 6. Peripheral nervous system is composed of nerves that connect CNS to body parts. 7. Function of two nervous systemssensory, integrative, and motor 8. Function of sensory receptors— gather info by detecting changes inside and outside the body, monitor external environ. factors (such as light and sound), and conditions of the body’s internal environ. (such as temp and O2 level) 9. Describe motor functions use peripheral neurons to carry impulses to effectors (muscles or glands=Action) 10. Responsive structures—what are they and what do they do— Effectors—muscles and glands— respond to signal from sensory receptors 11. Describe the two categories of motor functions—Somatic— consciously controlled (muscles), Autonomic –involuntary (heart, smooth muscle, glands) 12. Neuroglial cells produce the fatty lipoprotein __myelin______. 13. List the four types of neuroglial cells (of CNS) and their functions. a. Microglial- support neurons and phagocytize bacteria and debris b. Oligodendrocytes-provide myelin around axons c. Astrocytes-structure, joint parts, help regulate chem. concentrations, form scar tissue d. Ependymal- form membranes of specialized brain parts, inner linings of spaces of brain and spinal cord 14. What are Schwann cells? Cells of PNS that form myelin sheath around axons 15. Section 9.4: Sketch a neuron, describing the dendrites, axon, myelin. Myelinated- found in CNS—white matter Unmyelinatedfound in CNS are gray matter 16. Draw each type of neuron and describe their locations. a. Multipolar-many processes from body (one axon) in brain and spinal cord b. Bipolar-two processes (one axon, one dendrite) in specialized parts of eye, nose, ears c. Unipolar-single process that divides into two (one is dendrite, other enters brain or spinal cord) 17. List the three ways neurons are grouped and describe. a. Sensory-Carry impulses from body parts to brain or spinal cord— receive signal from receptor b. Interneurons -In brain or spinal cord-transmit impulses from one part to another—direct impulses from sensory to motor c. Motor-Carry impulses from brain or s.c. to effectors, causing muscle contraction or gland secretion 18. Read 9.5 –What forms a nerve impulse? A change in neuron membrane polarization and return to resting state (action potential) 19. Describe the resting potential. The undisturbed potential difference in electrical charge between the inside and the outside of the membrane—Higher Potassium inside, Sodium outside 20. What conditions can affect the resting potential? Stimuli such as changes in temperature, light, or pressure occurring outside the body 21. The change in the potential is directly proportional to – the intensity of the stimulation 22. 9.6 Describe how a nerve impulse occurs.—Action potential (permeability changes cause sodium to rush into the cell, causing a depolarization until Potassium diffuses out) causes a bioelectric current to flow to the adjacent nerve cell membrane, which triggers another action Events leading to conduction of nerve impulse (brown box P. 213) 1. Neuron membrane maintains resting potential 2. Threshold stimulus is received 3. Sodium channels open 4. Sodium ions diffuse inward, causing depolarization 5. Potassium opens, diffusing outward 6. Action potential that results causes a bioelectric current that stimulates adjacent portions of membrane 7. Wave of action potentials travels axon as nerve impulse ACTION POTENTIALS OCCUR AT NODES OF RANVIER 23. What is a synapse? Junction between two communicating neurons (no direct contact) 24. When a nerve impulse reaches a synaptic knob, some of the synaptic vesicles release a neurotransmitter, which reacts with receptors on the next neuron 25. 2 excitatory neurotransmitters are (increase sodium ion permeability which may trigger nerve impulses) Acetylcholine, Norepinephrine 9.8 26. Facilitation-neuron is more excitable to incoming stimulation because it received excitatory input. Convergence-Axons originating from different parts of NS but leading to the same neuron Divergence-impulses leaving a neuron and passing into several other neurons 9.9 27. Sensory fibers-bring sensory info to CNS Motor fibers-carry info from CNS to effectors Nerves do the same 9.10 Nerve Pathways 28. What are they? The paths a nerve impulse follows as it travels through the nervous system 29. A reflex arc makes up the simplest nerve pathway (only a few neurons). 30. What are reflexes? Involuntary, automatic subconscious responses to change (stimuli) within or outside the body—maintain homeostasis by controlling involuntary processes (hr, br, bp, digestion) and carry out auto. Actions such as swallowing, sneezing, coughing and vomiting 31. How does the knee jerk reflex occur? Patellar ligament is struck, causing a pull on the quad. femoris muscle, stimulating stretch receptors in this muscle, receptors trigger impulses that move along sensory neurons to the spinal cord, then impulse travels back to the quad. femoris, which contracts in response and the leg kicks 32. How many neurons are involved? Only two—a sensory communicating with a motor 33. How does the withdrawal reflex occur? Skin receptors send the message (you’re hurting yourself stupid) through sensory receptors to the spinal cord, impulses travel through interneurons to motor neurons, which signal the flexor muscles to contract and move, extensor muscles are inhibited--- Other Interneurons send sensory impulses to brain to feel pain (don’t hurt yourself more, stupid) 34. How is the withdrawal reflex protective? Protects the body from further tissue damage