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Types of Nervous Systems

Types of Nervous Systems. Cephalization. The concentration of neurons in a brain located in the head. Bilateral symmetry Allows for a concentration of sensory organs in the head. Flatworms—simple brain and 2 nerve cords. Vertebrate Nervous System. Central nervous system (CNS) Brain

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Types of Nervous Systems

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  1. Types of Nervous Systems

  2. Cephalization • The concentration of neurons in a brain located in the head. • Bilateral symmetry • Allows for a concentration of sensory organs in the head. • Flatworms—simple brain and 2 nerve cords

  3. Vertebrate Nervous System • Central nervous system (CNS) • Brain • Dorsal nerve cord • Peripheral nervous system (PNS) • Nerves- • Ganglia-clusters of nerve cells

  4. Information pathway

  5. Vertebrate Nerve cells • Neuron-Functional cell • Glia-Supporting cell • Astrocytes-CNS, maintain blood/brain barrier • Oligodendrocytes-insulation in CNS • Schwann cells-insulation in PNS

  6. Anatomy of a Neuron • Cell body~ nucleus and organelles • Dendrites~ impulses from tips to neuron • Axons~ impulses toward tips • Myelin sheath~ supporting, insulating layer made of schwann cells • Synaptic terminals~ neurotransmitter releaser • Synapse~ neuron junction

  7. Reflex Arc

  8. Membrane Potentials • Membrane potential (voltage differences across the plasma membrane) • Intracellular/extracellular ionic concentration difference • K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma membrane • Net negative charge of about -70mV

  9. Resting Potential • Nontransmitting neuron • -60 to -80 mV • Na+ and K+diffuse down concentration gradient • Neurons at rest are more permeable to K+ and less permeable to Na+-more ungated ion channels open

  10. Action potentials • Signals conducted by neurons • Gated channels-open and close in response to stimuli • Na+ and K+ voltage gated channels control action potential • Depolarization (inside of the cell becomes less negative) opens Na+ gated channels • Opening of K+ gates causes hyperpolarization (inside of cell becomes more negative)

  11. Conduction of Action Potentials • Na+ influx in rising spase depolarizes adjacent section of the membrane, bringing them to threshold.

  12. Speed of Action Potentials • Axon diameter (larger = faster; 100m/sec) • Nodes of Ranvier (concentration of ion channels); saltatory conduction; 150m/sec

  13. Synaptic communication • Presynaptic cell: transmitting cell • Postsynaptic cell: receiving cell • Synaptic cleft: separation gap • Synaptic vesicles: neurotransmitter releasers • Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release…. • Neurotransmitter

  14. Vertebrate PNS

  15. The Vertebrate Brain • Forebrain • cerebrum~memory, learning, emotion • cerebral cortex~sensory and motor nerve cell bodies • corpus callosum~connects left and right hemispheres • thalamus; hypothalamus • Midbrain • inferior (auditory) and superior (visual) colliculi • Hindbrain • cerebellum~coordination of movement • medulla oblongata/ pons~autonomic, homeostatic functions

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