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A motor neuron (or motoneuron or efferent neuron[1]) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. [2] There are two types of motor neuron ...
A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. [1] In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). [2] A skeletal muscle cell is long and threadlike with many nuclei and is called a muscle fiber. [3] Muscle cells develop from embryonic ...
A single motor neuron and the muscle fibers it innervates are called a motor unit. For example, the rectus femoris contains approximately 1 million muscle fibers, which are controlled by around 1000 motor neurons. Activity in the motor neuron causes contraction in all of the innervated muscle fibers so that they function as a unit.
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
v. t. e. In physiology, a stimulus[1] is a detectable change in the physical or chemical structure of an organism's internal or external environment. The ability of an organism or organ to detect external stimuli, so that an appropriate reaction can be made, is called sensitivity (excitability). [2] Sensory receptors can receive information ...
The somatic nervous system (SNS), also known as voluntary nervous system, is a part of the peripheral nervous system (PNS) that links brain and spinal cord to skeletal muscles under conscious control, as well as to sensory receptors in the skin. [ 1 ][ 2 ] The other part complementary to the somatic nervous system is the autonomic nervous ...
Alpha motor neurons are derived from the basal plate (basal lamina) of the developing embryo. Alpha (α) motor neurons (also called alpha motoneurons), are large, multipolar lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction.
The efferent fiber is a long process projecting far from the neuron's body that carries nerve impulses away from the central nervous system toward the peripheral effector organs (muscles and glands). A bundle of these fibers constitute an efferent nerve. [1] The opposite direction of neural activity is afferent conduction, [2][3][4] which ...