Neuroeffector junction
Encyclopedia
A neuroeffector junction is the site where a motor neuron
releases a neurotransmitter
to affect a target (non-neuron) cell
. This junction functions like a synapse
. Somatic efferent motor neurons
innervate skeletal muscle
, and are always excitatory
. Visceral efferent neurons
innervate smooth muscle
, cardiac muscle
, and gland
s, and may be either excitatory or inhibitory
. Neuroeffector junctions are known as neuromuscular junctions
when the target cell is a muscle fiber.
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
releases a neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
to affect a target (non-neuron) cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
. This junction functions like a synapse
Chemical synapse
Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie...
. Somatic efferent motor neurons
General somatic efferent fibers
The *spinal* somatic efferent neurons , arise from motor neuron cell bodies in the ventral horns of the gray matter within the spinal cord...
innervate skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
, and are always excitatory
Excitatory postsynaptic potential
In neuroscience, an excitatory postsynaptic potential is a temporary depolarization of postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels...
. Visceral efferent neurons
General visceral efferent fibers
The general visceral efferent fibers , probably arise from cells in the lateral column or the base of the anterior column and emerge through the anterior roots and white rami communicantes....
innervate smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
, cardiac muscle
Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...
, and gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
s, and may be either excitatory or inhibitory
Inhibitory postsynaptic potential
An inhibitory postsynaptic potential is a synaptic potential that decreases the chance that a future action potential will occur in a postsynaptic neuron or α-motoneuron...
. Neuroeffector junctions are known as neuromuscular junctions
Neuromuscular junction
A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract...
when the target cell is a muscle fiber.