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Functions of the Nervous System

Delve into the workings of the nervous system, from sensory input to motor output, and understand its components like neurons and neuroglial cells. Learn about the initiation of action potentials, synaptic transmission, and the roles of neurotransmitters in signal transmission. Explore the organization and divisions of the nervous system, including the central and peripheral nervous systems. Gain insights into reflex arcs, the autonomic nervous system, and the brain's major divisions and functions.

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Functions of the Nervous System

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  1. Functions of the Nervous System 1. Sensory input – gathering information • monitor changes both inside and outside the body • Changes = stimuli 2. Integration -- process and interpret sensory input 3. Motor output • A response to integrated stimuli • The response activates muscles or glands

  2. Components of the Nervous System • Central Nervous System • brain, spinal cord • Peripheral NS • Sensory - input • afferent (approach) • Motor - output • efferent (exit) Figure 11.1

  3. Organization of the Nervous System • Motor (efferent) division • Somatic nervous system = voluntary • Autonomic nervous system = involuntary Figure 7.2

  4. Communication Cells of System • Neurons: specialized cells for communication • Types: • sensory • interneurons • motor neurons

  5. Neuron Anatomy • Cell body • Dendrites • Axon • Neuroglial cells: support and protect neurons • Schwann cells • Wrap around axon Figure 7.4a–b

  6. Myelin Sheath on Neuron • Myelin sheath: Schwann cells in PNS • Functions: • Saves the neuron energy • Speeds up the transmission of impulses • Helps damaged or severed axons regenerate

  7. Nervous Tissue: Support Cells • Oligodendrocytes - protection in CNS • Produce myelin sheath around nerve fibers in the central nervous system Figure 7.3d

  8. Maintenance of the Resting Membrane Potential PLAY Press to playActive Transportvideo Figure 11.4

  9. Neurons Initiate Action Potentials • Na-K pump: maintains resting potential • Graded potential: alters resting potential, either to depolarize or hyperpolarize

  10. Resting Membrane Potential, Graded Potentials, and an Action Potential Graded potentials can reach threshold and trigger an action potential Figure 11.5

  11. Action Potential • Depolarization: sodium moves into the axon • Repolarization: potassium moves out of the axon • Re-establishment of the resting potential: the normal activity of the sodium-potassium pump

  12. Action Potentials • All or none: • individual neuron thresholds; when this threshold is reached, it fires • Self-propagating: • electrical current reaches threshold throughout axon during spread of the action potential

  13. Summary of Synaptic Transmission How does ON/OFF signal create a graded potential? AP moves Ca ++ into bulb Ca++ causes vesicles to release neurotransmitter 3. Neurotransmitter binds to receptor, causing Na+ channel to open. 4. Na+ flows into cell, creating graded potential Figure 11.7

  14. Neurotransmitters • Excitatory - depolarize postsynaptic cell. • Acetylcholine - muscle cells • Norepinephrine - areas of brain and spinal cord ANS • Glutamate - major excitatory transmitter in brain • Inhibitory - hyperpolarize postsynaptic cell. • Serotonin - areas of brain, spinal cord. involved in sleep, appetite, moods • Dopamine - brain, parts of PNS. Involved in emotions. • Endorphins - brain, spinal cord. Natural opiates that inhibit pain • Somatostatin - brain, pancreas. Inhibits pancreatic release of growth hormone.

  15. Peripheral Nervous System • Nerves and ganglia outside the central nervous system • Nerve = bundle of neuron fibers • Nerves: carry signals to and from CNS • Cranial nerves: connect directly to brain • Spinal nerves: connect to spinal cord

  16. The Reflex Arc Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector • Crossed extensor reflex, stretch reflex, flexor

  17. Organization of the Nervous System • Motor (efferent) division • Somatic nervous system = voluntary • Autonomic nervous system = involuntary Figure 7.2

  18. Differences between Somatic and Autonomic NS

  19. Sympathetic – “fight-or-flight” • “E” division = exercise, excitement, emergency, and embarrassment Autonomic Nervous System • Parasympathetic – housekeeping activites • Conserves energy • necessary body functions • “D” division - digestion, defecation, and diuresis Figure 7.25

  20. Central Nervous System • CNS protection • Bone: skull and vertebrae • Meninges: dura mater, arachnoid, and pia mater • Cerebrospinal fluid: carries nutrients and waste for CNS Blood-brain barrier: • Spinal cord: relays information through nerve tracts in white matter

  21. Spinal Cord • Connects PNS to brain; reflex center • Extends from the brain to lumbar region • 31 pairs of nerves Figure 7.18

  22. Spinal Cord Anatomy • Exterior white mater – conduction tracts • Internal gray matter - mostly cell bodies Figure 7.19

  23. Brain: Major Divisions • Hindbrain: coordinates basic, automatic, vital functions • Medulla oblongata: controls automatic functions of internal organs • Cerebellum: coordinates basic movements • Pons: aids flow of information

  24. Hindbrain, Midbrain • Midbrain: coordinates muscles related to vision & hearing

  25. Brain: Processes and Acts on Information • Forebrain: receives and integrates information concerning emotions and conscious thought • Hypothalamus: helps regulate homeostasis • Thalamus: receiving, processing, and transfer center • Limbic system: neuronal pathways involved in emotions and memory • Cerebrum/cerebral cortex: higher functions

  26. Specialized Areas of the Cerebrum Figure 7.13c

  27. Sensory and Motor Areas of the Cerebral Cortex Figure 7.14

  28. Sleep • Sleep center: reticular activating system (RAS) • Stages: based on electroencephalograms (EEGs) • Stage 1-4

  29. Limbic System: Emotions of Fear, Anger, Sorrow, Love Figure 11.18

  30. Psychoactive drugs • Affect consciousness, emotions, behavior • Cross blood-brain barrier • Affect action of neurotransmitters • Ex. Cocaine blocks reuptake of dopamine Psychological dependence Tolerance

  31. Disorders of the Nervous System • Trauma: concussion, stroke, spinal cord injuries • Infections: encephalitis, meningitis, rabies • Neural and synaptic transmission: epilepsy Parkinson’s disease Alzheimer’s disease • Brain tumors - growth of glial cells

  32. Alzheimer’s Disease • Progressive, degenerative brain disease • Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons Parkinson’s - lack of dopamine, such that certain neurons are overactive, cause jerky muscle contractions

  33. Development Aspects of the Nervous System • The nervous system is formed during the first month of embryonic development • Any maternal infection can have extremely harmful effects • The hypothalamus is one of the last areas of the brain to develop

  34. Where Do You Stand Among Your Peers? Table 11.3

  35. Cerebrum

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