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Nervous System Communication

Nervous System Communication. Kid Concussions In The News. Neurons. Nerve cells Parts of neurons Cell body Long extensions Message = nerve impulse. Animal Nervous Systems. Sponges – no nervous system Other animals all have neurons in systems. Nerve Net. In all cnidarians

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Nervous System Communication

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  1. Nervous System Communication

  2. Kid ConcussionsIn The News

  3. Neurons • Nerve cells • Parts of neurons • Cell body • Long extensions • Message = nerve impulse

  4. Animal Nervous Systems • Sponges – no nervous system • Other animals all have neurons in systems

  5. Nerve Net • In all cnidarians • Interconnected nerve cells • No brain

  6. Ringlike Nervous System • In echinoderms • Ring with 5 radiating nerves

  7. Ladderlike Nervous System • In many Platyhelminthes • Some have distinct brain

  8. Annelid Nervous System • Segmental ganglia • Ganglia = aggregations of nervous tissue • Ventral nerve cord & brain

  9. Vertebrate Nervous System • Central nervous system • Brain & spinal cord • Peripheral nervous system • Nerves to & from CNS

  10. Nerve Cells • Cell body • Contains nucleus • Organelles necessary for cell • Axon • Long cell extension • May have myelin covering • Dendrites • Cell extensions • No myelin covering

  11. Sensory Neurons • Receive information • Transmit to the central nervous system

  12. Motor Neurons • Transmit commands away from CNS • To muscles & glands

  13. Interneurons • Located within brain & spinal cord • Integrate information • Axons may not be myelinated

  14. Neuroglia • Nerve support cells • Provide support, protection, & nutritional stability • Schwann cells • Found around axons • Produce myelin sheath

  15. Myelin Sheath • Insulates axon • Nodes of Ranvier • Uncovered areas

  16. Nerve Impulses • Electrical signals transmitted along membranes of nerves

  17. Resting Potential • Neuron is electrically charged at rest • Outside is positively charged • Inside is negatively charged

  18. Sodium-Potassium Pump • Proteins embedded within cell membrane • Moves sodium to the outside • Moves potassium to the inside • Maintains resting potential • Requires energy

  19. Action Potential • Nerve impulse is started by a stimulus • Stimuli cause movements of ions through membrane • Threshold potential • Sufficient stimulation to depolarize membrane • Action potential • Rapid reversal of membrane electric potential

  20. Nerve Transmission • Action potential at one point depolarizes next area • Depolarization moves in self-propagating wave

  21. Saltatory Conduction • Nerve impulse jumps & moves faster along myelinated axon

  22. Synapse • Area where nerve communicates • Transfers message • Another neuron • An effector

  23. Synaptic Cleft • Neurons do not touch other neurons or effector cells • Nerve impulse must cross gap

  24. Neurotransmitters • Organic molecules (> 60 different chemicals) • Transfer message across synaptic cleft • Attach to receptors on target cell

  25. Neuromuscular Junctions • Synapse between neuron & skeletal muscle • Neurotransmitter is acytylcholine

  26. Neuron to Neuron Connections • Uses many different neurotransmitters • Some cause different effects • Excitatory synapse – continuation of impulse • Inhibitory synapse – reduce ability to depolarize

  27. Integration of Nerve Impulses • Summed impulses determine if postsynaptic neuron will depolarize

  28. Human Nervous System • Central nervous system • Brain • Spinal cord • Peripheral nervous system • Brings messages to & from CNS • Somatic nervous system – voluntary • Autonomic nervous system - involuntary

  29. Central Nervous System • Integrates sensory & motor impulses

  30. Spinal Cord • Connects peripheral nervous system with brain • Receives information via spinal nerves • Includes reflex arcs

  31. CNS Protection - Meninges • Layers of membranes • Dura mater • Arachnoid • Pia mater

  32. Peripheral Nervous System • Sensory & motor impulses • Cranial nerves communicate directly with brain

  33. Spinal Nerves • Sensory & motor nerve fibers • Travel directly to spinal cord • Nerves are bundled to form mixed nerves

  34. Motor Neuron Systems • Somatic • Voluntary • Movements of skeletal muscles • Autonomic • Involuntary • Reflex = automatic response to nerve stimulation • Involuntary motor pathways

  35. Divisions of the Autonomic Nervous System • Parasympathetic • Prevails during periods of inactivity • Housekeeping • Sympathetic • “fight or flight” • Responds to stress • Prepares body for action • Parasympathetic & sympathetic together help to maintain homeostasis

  36. Psychoactive Drugs • Affect action of nervous system • Neurotransmitters • Specific parts of the brain • Some are abused

  37. Drug Addiction • Chronic use (or abuse) of psychoactive drugs • Person becomes physically dependant • Drug use tends to increase due to drug tolerance

  38. End Chapter 32

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