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Nervous System

Nervous System. Transmission of Nerve Signals for Communication Coordination and Regulation of Body Systems. Structure of a Neuron. Dendrites (receive signals). Cell Body (maintains cell metabolism). Myelin Sheath (insulator). Axon bulb. Axon (conducts signals).

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Nervous System

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  1. Nervous System Transmission of Nerve Signals for Communication Coordination and Regulation of Body Systems

  2. Structure of a Neuron Dendrites(receive signals) Cell Body(maintains cell metabolism) Myelin Sheath(insulator) Axon bulb Axon(conducts signals) Dendrite of anotherneuron Axon of anotherneuron

  3. Receives information from environment Carries signal between sensory and motor neurons Generates a response Types of Neurons

  4. gaps in myelin sheath formed by Schwann cells bundle of nerve fibers axon

  5. Transmission of Nerve Impulse Along a Neuron • Involves a change in charge across the neuron’s membrane, caused by the movement of ions • Action Potential = rapid depolarization and repolarizationof membrane

  6. 80 40 Recorded Potential(millivolts) 0 -40 -80 Time (milliseconds) Electrical Events During AnAction Potential Action Potential Extracellular Fluid(uncharged) 2 depolarization Threshold RestingPotential 3 repolarization 1 EPSP polarized IPSP

  7. 2 Resting Potential Depends on Ionic Gradients Net negative charge insideneuron Inside: • Potassium ionsare pumped intocell Na+ Na+ Cl- • Large organic moleculescannot pass through membrane Cl- Na+ Org- K+ Org- K+ Org- K+ Org- Org- Org- Na+ K+ K+ Cl- Cl- Outside: K+ Org- Org- • Sodium ions arepumped out Na+ Na+ Cl- Org- • Chloride ionsfound in extra-cellular fluid Cl- K+

  8. PotassiumChannel(closed) SodiumChannel(closed) Resting Potential

  9. Action Potential 2. Potassium flows out of neuron through open channel, causing repolarization 1. Sodium flows into neuron through open channel, causing depolarization inside inside outside outside

  10. 15 Propagation of an Action Potential Along an Axon

  11. synapse 14 Transmission of Nerve Impulses Between Neurons • Signal is carried by neurotransmitters that diffuse across the space between neurons • Synapse: junction between neurons • Synaptic cleft: space between neurons • Neurotransmitters bind to receptors on next neuron, opening ion channels

  12. 1 Actionpotential isinitiated Structure and Operationof the Synapse 2 Action potentialreaches axon bulb Pre-synaptic cell 3 Synaptic vesiclesreleaseneurotransmitter 5 Action Potential can be triggered in post-synaptic cell 4 Neurotransmitter binds to receptor and opens ion channel Post-synaptic cell

  13. Transmission Between Neurons • Neurotransmitters can be • Stimulatory: initiate action potential • Acetylcholine • Inhibitory: prevent action potential • Dopamine • After acting on the post-synaptic neuron, neurotransmitters are removed from the synaptic cleft • Acetylcholinesterase breaks down acetylcholine

  14. 19 Neurotransmitters carry signals to muscle cells to stimulate contraction.

  15. Applying Your Knowledge • Potassium Ions (K+) • Neurotransmitters • Sodium Ions (Na+) • Which one is responsible for • Transmission of a nerve impulse across a synapse? • Depolarization of a neuron’s membrane? • Transmission of a nerve impulse along an axon? • Repolarization of a neuron’s membrane?

  16. Spinal Cord Brain Autonomic Nervous System(involuntary) Somatic Nervous System(voluntary) Parasympathetic Division(maintenance or relaxation) Sympathetic Division(stress or activity) Nervous System Organization Central Nervous System Peripheral Nervous System

  17. sends sensory input to cerebrum homeostasis breathing, heart rate, blood pressure Cortex: thinking, learning, memory, speech movement, senses Parts of the Brain musclecoordination

  18. Involve the Somatic Nervous System Spinal Cord and Reflex Arcs

  19. dilates pupils constricts pupils constricts bronchioles dilates air passages speeds heart slows heart decreases stomach and intestinal activity increases stomach and intestinal activity Autonomic Nervous System

  20. Applying Your Knowledge • Central Nervous System • Somatic Nervous System • Autonomic Nervous System • Which one • Is responsible for increasing breathing rate when you start running? • Includes the spinal cord? • Controls skeletal muscle movement?

  21. Nervous System Disorders • Alzheimer Disease: gradual loss of neural function due to tangles and plaques associated with axons • Parkinson Disease: deficiency of dopamine causes tremors, rigidity, shuffling gait • Huntington Disease: uncoordinated movements and degenerative neurological symptoms beginning at middle age, due to autosomal dominant inheritance

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