Nerve Impulse

    Cards (42)

    • Nerve Impulse - electrical message that is transmitted down the axon of a neuron.
    • Nerve Impulse - does not travel directly down the axon but is regenerated at points along the axon so that is is not weakened.
    • Speed - of nerve impulse ranges from less than 1 meter/second to 100 meter/second.
    • Messages in a neuron develop from disturbances of the: resting potential.
    • RESTING POTENTIAL - the membrane maintains an Electrical Gradient, also known as polarization
    • polarization - a difference in electrical charge between the inside and outside of the cell.
    • polarization - a difference in the electrical charge of two locations.
    • Resting Potential - refers to the state of the neuron prior to the sending of a nerve impulse.
    • The membrane is "selectively permeable" allowing some chemicals to pass more freely than others.
    • When membranes are at REST:
      • Sodium Channels are: Closed
      • Potassium Channels are: Partially Closed
    • Sodium-potassium pump - a protein complex, repeatedly transports three sodium ions out of the cell while drawing two potassium ions into it.
    • Three - number of sodium ions out of the cell during sodium-potassium pump
    • Two - number of potassium ions in during sodium potassium pump
    • Sodium-potassium pump - Helps to maintain the electrical gradient
    • resting potential - invests much energy to prepare the neuron to respond rapidly
    • action potentials - messages sent by axon
    • Hyperpolarization - which means increased polarization.
    • Depolarization - refers to decreasing the polarization towards zero
    • threshold of excitement - refers to a level above which any stimulation produces a massive depolarization.
    • Action potential - rapid depolarization of the neuron
    • Depolarized - state of polarization during action potential
    • Action Potential - triggered during stimulation of neuron past the threshold of excitation
    • Outside - where sodium ions are at the start of the action potential
    • Inside - mostly where potassium ions are during action potential
    • At the peak of action potential Sodium Channels are: closed
    • propagation - describes the transmission of an action potential down an axon.
    • action potential "don't" directly travel down the axon
    • Axon Hillock - Where the action potential begins
    • Axon Hillock - swelling where axon exits the soma
    • Myelin Sheath - increase the speed still more, vertebrate axons evolved a special mechanism
    • Myelin Sheath - an insulating material composed of fats and proteins.
    • nodes of Ranvier - interrupt the myelin sheath of axons
    • Saltatory conduction - The jumping of action potentials from node to node.
    • Saltatory conduction - Provides rapid conduction of impulses
    • Saltatory conduction - Conserves energy for the cell
    • Multiple sclerosis - disease in which the myelin sheath is destroyed and
      associated with poor muscle coordination and sometimes visual impairments
    • Refractory Period - Happens after action potential where the neuron resists the production of another action potential
    • Absolute - the first part of refractory period in which the membrane cannot produce an action potential
    • Relative - the secondary part of the refractory period where it takes a stronger than usual stimulus to trigger an action potential
    • Local Neurons - Small neurons that have no axon