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The Nervous System

The Nervous System. Chapter 9. General Functions of Nervous System. Maintain HOMEOSTASIS by: Receiving, interpreting and integrating sensory information from the environment Sending signals to muscles and glands so they can respond. Divisions of Nervous System.

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The Nervous System

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  1. The Nervous System Chapter 9

  2. General Functions of Nervous System Maintain HOMEOSTASIS by: • Receiving, interpreting and integrating sensory information from the environment • Sending signals to muscles and glands so they can respond

  3. Divisions of Nervous System • Central Nervous System (CNS) • Brain • Spinal cord • Controls all conscious and unconscious activity • Peripheral Nervous System (PNS) • Cranial nerves • Spinal nerves • Connects CNS to the rest of the body

  4. Cranial Nerves

  5. Spinal Nerves

  6. Divisions of PNS • Somatic NS • Nerves that connect to skeletal muscles and skin • Controls voluntary/consciousresponses • Autonomic NS • Nerves that connect to viscera, heart, smooth muscle, glands • Controls involuntary/subconscious responses

  7. Divisions of Autonomic NS • Sympathetic NS • Regulates body’s responses to stress, anger, fear, anxiety… • Controls “fight or flight” mechanisms • Parasympathetic NS • Restores homeostatic conditions after stress, anger, fear… • Controls “rest and digest” mechanisms

  8. Cells of the Nervous System • Neurons -found in CNS and PNS -have unique cells and structure -transmit signals to other neurons • Neuroglial Cells -neuron “helper” cells; not neurons themselves -Found only in CNS

  9. Neurons • Include • Dendrites, cell body, and axon • Dendrites receiveimpulses and send them to cell body • Axons transmitimpulses away from cell body

  10. Neurons in PNS • axons are surrounded by SCHWANN CELLS • Schwann cell membranes have MYELIN in them • NEURILEMMA- extra protection around axon • NODES OF RANVIER: narrow gaps in the myelin sheath between Schwann cells

  11. Neurons in CNS • Some axons have myelin (MYLELINATED) others don’t (UNMYELINATED) • Myelin in CNS comes from Oligodendrocytes • Myelinated axons appear as white matter • Unmyelinated axons are gray matter

  12. Can we fix it? • Peripheral neurons are able to regenerate if damaged • Myelin sheath is surrounded by a tube of neurilemma • CNS neurons are not able to regenerate if damaged • Not surrounded by neurilemma

  13. More on Neurons • Neurons can be classified based on structure • Multipolar-brain and SC • Bipolar-eyes, nose, ears • Unipolar-ganglia outside CNS

  14. More on Neurons • Neurons can be classified based on function: • Sensory Neurons- (afferent) carry impulses from body parts to brain or spinal cord (unipolar, some bipolar) • Interneurons- lie entirely within the brain or spinal cord (CNS); transmit impulses from one part of the brain or spinal cord to another. (Multipolar) • Motor Neurons- (efferent) carry impulses out of the brain or spinal cord to effectors (multipolar)

  15. Neuroglial Cells • Fill spaces, support neurons, provide structural frameworks, produce myelin, and carry on phagocytosis. • Types: microglial, oligodendrocytes, astrocytes, ependymal cells, schwann cells

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