Answer
Dendrites and axons are protoplasmic processes that grow out of the cell body of a neuron. Both dendrites and axons have branches , and both have cell membranes and some cellular organelles. Both types of projections communicate with the soma and keep it in touch with
neighboring neurons. These superficial similarities notwithstanding, dendrites and axons are fundamentally different in structure and function.
Structure
Dendrites display as many projections with numerous spikes and small knobs.
A neuron usually has a single axon. It displays as a threadlike projection that grows from the axon hillock of the soma .
Dendrites have norml cell membranes and the normal organelles of the soma.
Axons lack a golgi body and rough endosplasmic reticulum (RER). An axons may be myelinated, or unmyelinated. In myelinated axons the plasma membrane and nucleus of the Schwann cell or oligodendrocyte seem to be part of the axon. Also the fatty internodes radically alter the appearance of myelinated fibers.
Axons end in thousands of small branches near their targets. These aborizations have buttons with vesicles that contain neurotransmitters.
Functions
Both dendrites and axons communicate with the soma electrically chemically.
Dendrites constitute the input end of the neuron. They receive and transmit impulses to the soma in the form of graded electrical potentials.
The axon is the output end of the neuron. It initiates an
action potential (AP) at its junction with the axon hillock of the soma and transmit it as an electrical message to the terminal aborization; then the it transforms the impulse into a chemical message through the agency of a neurotransmitter
Work Step by Step
r. Dendrites and axons are protoplasmic projections from the soma or cell body of a neuron. Both dendrites and axons have a plasma membrane and cellular organelles. They are also in constant communication with the cell body, electrically and metabolically. Nevertheless, there are fundamental differences between dendrites and axons, structurally and functionally.
Dendrites display as many short projections from the input end of a neuron.These projections branch many times and end in small spikes and buttons; this repeated branching results in a great increase of surface area of the initial branches. Dendrites have normal plasma membranes and the same organelles as the cell body.
Generally, axons do not branch until they get near their targets. However, some axons do sprout quasi-right-angled branches, or collaterals,from some of their nodes ( Nodes of Ranvier). Generally, axons which grow from the output end of a neuron, taper from the axon hillock of the soma into a single somewhat cylindrical thread-like fiber that maybe short or as long as a meter. Axons are also different from dendrites in that some axons are covered with internodes of myelin over certain areas. This speeds up AP conduction by saltatory (jumping) transmission from node to node.
Dendrites have all the normal organelles of the perikaryon, but axons lack a golgi apparatus ,and rough endoplasmic reticulum (RER). Consequently, axons cannot synthesize proteins, and other cell membrane components; they therefore have to depend on the cell bodies to supply these vital cell components.
The function of dendrites is to receive messages from other neurons or sense organs and to transmit them in the form of graded potentials to the cell body of the neuron :the function of the dendrites is therefore an input function.
The axon is the conduction region of the neuron. It generates an action potential at the "trigger zone" and conducts it away from the cell body.This is the output function of the neuron.. When the AP reaches the terminal buttons ( terminal boutons) of the terminal aborization, it causes a release of neurotransmitters stored in vesicles at the end of the presynaptic neuron. The neurotransmitter is released into the fluid of the synaptic cleft and excites or inhibits the post-synaptic neuron or target cell ( gland or muscle).
