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Axon – Structure and Functions

  • All neurons have a cytoplasmic process called an image descriptionaxon (nerve fiber), which conducts electrochemical impulses or action potentials
An image of neuron showing its structures (axon)
An image of neuron showing its structures (axon is labeled)
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  • Axons most commonly attach to one side a neuron cell body (soma, perikaryon), at a cone-shaped region called the image descriptionaxon hillock.
An image of neuron showing its structures (axon is labeled)
An image of neuron showing its structures (Axon hillock and axon are labeled)
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  • Electrochemical events in the cell body summate in the axon hillock, and the effect are directly passed to the attached axon.
  • If an action potential is generated, the axon conducts it away from the cell body.
  • The axon attaches directly to the dendrites in some neurons. In this arrangement, the axon conducts action potential toward the cell body.
  • Several types of image descriptionproteins in the plasma membrane of an axon (axolemma) allow it to produce and conduct action potentials.
An image of neuron showing its structures (Axon hillock and axon are labeled)
An image of neuron showing the proteins of the plasma membrane of the axon in addition to the Axon hillock and axon, proteins are not labeled
An image of neuron showing the proteins of the plasma membrane of the axon in addition to the Axon hillock and axon, all are labeled
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  • The initial segment of an axon has the highest concentration of these reactive proteins. this region is an axon’s trigger zone, where action potentials are first produced if electrochemical events in the dendrites and/or cell body reach a threshold level.
  • Axons vary in length from a few millimeters to just over a meter. They are less branched than most dendrites, but often give off one or more large image descriptioncollateral branches that lead to other cells.
An image of neuron showing the proteins of the plasma membrane of the axon in addition to the Axon hillock and axon, all are labeled
An image of neuron showing the Collateral branch of the axon in addition to the proteins of the axon membrane, Axon hillock and axon, all are labeled
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  • Before ending, an axon and its collaterals split into clusters of small, thin image descriptionterminate branches (telodendria).
An image of neuron showing the Collateral branch of the axon in addition to the proteins of the axon membrane, Axon hillock and axon, all are labeled
An image of neuron showing the Terminal branch of the axon in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all are labeled
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  • The rounded tips of the terminal branches are called image descriptionsynaptic knobs, (end bulbs, axon terminals, synaptic terminals, terminal boutons or buttons).
An image of neuron showing the Terminal branch of the axon in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all are labeled
An image of neuron showing the Synaptic knob of the Terminal branch in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all are labeled
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  • Inside the synaptic knobs are image descriptionvesicles (synaptic vesicles) that contain neurotransmitter molecules.
An image of neuron showing the Synaptic knob of the Terminal branch in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all are labeled
An image of neuron showing the Synaptic vesicle and Synaptic knob of the Terminal branch in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all are labeled
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  • A synaptic knob usually lies adjacent to another cell. the neighboring cells and the gab that separates them is called a synapse.
  • The plasma membrane of postsynaptic cell has receptors for the neurotransmitters in the vesicles of the synaptic knob.
  • When an action potential is generated, it travels (propagates) the length an axon to synaptic knobs, where it signals the synaptic vesicles to image descriptionrelease some of the stored neurotransmitters.
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image showing the action potential generation after neuron stimulation
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image of a neuron showing the action potential moving from the neuron body to the terminal branches passing through the axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon
An image showing the neurotransmitter secretion out of the Synaptic vesicles of the terminal branches of a neuron axon

Overview:

Test yourself image showing the Synaptic vesicle and Synaptic knob of the Terminal branch in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all numbered without answers
Test yourself image showing the Synaptic vesicle and Synaptic knob of the Terminal branch in addition to the Collateral branch, proteins of the axon membrane, Axon hillock and axon, all numbered with answers below
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