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The Nervous System

The Nervous System. Chapter 35. Levels of Organization. In order to get trillions of cells to work together, the body is organized into levels: Cells – smallest unit of structure and function Tissues – groups of cells working together for the same purpose. Types of Tissues:

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The Nervous System

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  1. The Nervous System Chapter 35

  2. Levels of Organization • In order to get trillions of cells to work together, the body is organized into levels: • Cells – smallest unit of structure and function • Tissues – groups of cells working together for the same purpose

  3. Types of Tissues: • Epithelial – covers, lines and protects • Muscle – causes movement by contraction • Connective – binds, supports, pads, insulates • Nervous – sends electrochemical impulses

  4. Organs – groups of tissues working together for the same purpose • Organ Systems – groups of organs working together for the same purpose • Organism

  5. Nervous Integumentary Respiratory Digestive Excretory Skeletal Muscular Circulatory Endocrine Reproductive Lymphatic/Im-mune Organ Systems

  6. Organ systems work together to maintain homeostasis in the body.

  7. NERVOUS SYSTEM • A body system that controls and coordinates functions throughout the body and responds to internal and external stimuli • Composed of the CNS (central nervous system) and PNS (peripheral nervous system)

  8. CNS (Central Nervous System) – relays, processes and analyzes information • Composed of the brain and spinal cord • Protected by the skull, cerebrospinal fluid, and 3 meninges

  9. Brain • 2 hemispheres • Wrinkled • Cortex (outer edge) with “gray matter” made of neurons (thinking cells); • “white matter” – support cells; cells that reproduce

  10. Wrinkled

  11. Hemispheres

  12. Gray and White Matter

  13. Regions: • Cerebrum • Voluntary, conscious thought • Intelligence, learning, judgement • 2 halves connected by the corpus callosum • Divided into 4 lobes

  14. Frontal – critical thinking, judgment, personality

  15. Parietal – sensation, learned skills

  16. Temporal – smell, taste, hearing, speech, verbal and written comprehension

  17. Occipital - sight

  18. Cerebellum – coordination of skeletal muscles • Brain stem (pons and medulla oblongata) – respiratory and cardiac centers • Other – hypothalamus, thalamus, corpus callosum, hippocampus, pituitary

  19. Spinal Cord • Reflex center • Major nerve cord • No regeneration

  20. PNS – conducts impulses from CNS to effectors (muscles and glands) • Functional divisions • Somatic nervous system • Voluntary • Contracts skeletal muscles

  21. Autonomic • Involuntary, automatic • System of checks and balances (opposites) • Sympathetic system – “fight or flight” • Parasympathetic – “resting and digesting”

  22. Nervous Response • Found only in animals • Composed of 3 parts • Receptors • Effectors • neurons

  23. Receptors – receive stimuli and send impulses to the CNS • Skin – touch, pressure, temperature, pain • Taste – stimulation in chemical form

  24. Smell – stimulation in chemical form • Hearing – stimulation by sound waves (vibrations) • Vision – receptors in eyes stimulated by light waves

  25. Effectors – responding structures • Muscles • glands

  26. Neurons – nerve cell • Cells that carry messages (“impulses”) throughout the nervous system • Differ in structure and direction in which they carry impulses

  27. 3 types based on structure Multipolar Unipolar Bipolar

  28. Neuron Structure • Bundle of neurons = nerve

  29. Cell Body AXON Terminals Myelin sheath Node } Axon

  30. 3 types:(based on function) • Sensory – send impulses from receptors to CNS • Motor – send impulses from CNS to effectors • Interneurons – join sensory to motor (found in brain and spinal cord)

  31. Sensory Interneuron Motor

  32. Impulses flow from dendrite to cell body to axon to dendrite of next neuron

  33. Action Potential - Nerve impulse traveling down a neuron • Neuron at rest has (+) ions outside the membrane and (-) inside + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + +

  34. When stimulated “gates” open, (+) ions flow in , neuron is “depolarized” - - - + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + +

  35. More “gates” open, (+) ions are pumped back out, neuron is “repolarized + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + +

  36. Myelin Sheath – insulation • Composed of 80% lipid, 20% protein • Allows impulse to jump from node to node

  37. Synapse • Gap between the axon terminals of one neuron and the dendrites of the next • secrete neurotransmitters to ferry impulse across gap

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