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Nervous Systems

Dendrites. Presynaptic terminals. Cell body or Soma. Nucleus. Axon hillock. Myelin sheath. Axon terminals. Axon. Vertebrate Spinal Motor Neuron. ???. The Resting Potential. Neurons have an electric charge difference across their plasma membranes. This resting potential is the result of ion concentration differences created by ion pumps and ion channels in the membrane. .

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Nervous Systems

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    1. Nervous Systems Resting membrane potential and its basis Action potential and its ionic basis Nerve impulse conduction Synaptic Transmission Integration of information by summation

    3. The Resting Potential Neurons have an electric charge difference across their plasma membranes. This resting potential is the result of ion concentration differences created by ion pumps and ion channels in the membrane.

    4. Measuring Membrane Potentials

    5. Basis of the Resting Membrane Potential

    6. Membrane Potential is a Dynamic Equilibrium

    7. Overview of the Resting Potential

    8. Graded Membrane Potentials

    9. The Action Potential

    15. Nerve Impulse Conduction Conduction of action potentials is not like conduction of charge along a wire conductor. The axon is a poor conductor of electrical charge and is leaky to charge in the form of ions.

    16. Propagation of the Action Potential

    20. Unidirectional Propagation

    21. Myelinated Neurons

    22. Saltatory Conduction in Myelinated Axons

    23. Myelinated Neurons Conduct Faster Than Non-myelinated Myelin sheathing and saltatory conduction improves the speed of nerve impulse conduction. This allows small diameter neurons to conduct impulses rapidly. Invertebrates, which dont have myelinated neurons, have to increase axon diameter to speed up conduction. The larger the cross-sectional area of a neuron, the further it can conduct electrical charge along the axon. Giant axons are found in some invertebrates like earthworms and squid that need to rapidly conduct nerve impulses to distant muscles for escape responses.

    25. Neurons, Synapses, and Communication Neurons communicate with each other and other cells through specialized junctions called synapses, where plasma membranes of two cells come close together. Two types of synapses occur, electrical and chemical. Electrical synapses allow ionic currents to pass directly from one cell to the other through gap junctions so the action potential in the presynaptic neuron can directly trigger an action potential in the postsynaptic cell. Electrical synapses have a very short delay and are common in many invertebrates.

    26. Chemical Synapse

    27. Chemical Synapse

    28. Chemical Synapse

    29. Chemically Gated Ion Channels

    30. Chemically Gated Ion Channels

    31. Integration of Multiple Synaptic Inputs

    32. Excitatory and Inhibitory Synapses Synapses between neurons are either excitatory or inhibitory depending upon the type of neurotransmitter released by the presynaptic cell and the types of chemically gated ion channels that are opened on the postsynaptic cell.

    33. Excitatory Synapse An excitatory synapses releases a neurotransmitter that depolarizes the postsynaptic cell and causes an excitatory postsynaptic potential (EPSP). The postsynaptic cell is brought closer to its firing threshold by an EPSP. In this case the neurotransmitter opens chemically gated Na+ channels which allow positive charge (Na+ ions) to flow into the postsynaptic cell.

    34. Inhibitory Synapse An inhibitory synapse releases a neurotransmitter that hyperpolarizes the postsynaptic cell, causing an inhibitory postsynaptic potential (IPSP). The postsynaptic cell is brought further from the firing threshold. In this case the chemically gated channels that open are either K+ channels which allow efflux of K+ or Cl- channels which allow influx of Cl--.

    35. Integration of Information by Postsynaptic Cells

    36. Temporal Summation of Postsynaptic Potentials

    38. Role of Inhibitory Neurons Inhibitory neurons can help coordinate response of effectors like muscles. Often contraction of an opposing muscle is prevented by an inhibitory neuron in the spinal cord. In the knee-jerk reflex, the flexor muscle is prevented from contracting by an inhibitory neuron.

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