Effector neurons, also called efferent nerves, carry motor impulses away from the central nervous system, generally toward muscles or glands.

An effector acts in special ways in response to a nerve impulse. In humans, the end of the path for effector neurons may either be muscles, which contract in response to neural stimuli, or glands, which produce secretions. The job of the effector neuron is to move an electrical impulse from the central nervous system to an effector in order to respond to an experienced stimulus. In contrast, affector neurons carry nerve impulses to the sensory system.

There are two types of effector-related muscles: somatic effectors, which are the body's skeletal muscles (such as those found in the arm, leg, and back) and autonomic effectors, which are smooth muscles, the heart, and glands.

Both types of effectors are linked to the gray matter of the spinal cord, but each system originates in a different portion of it. The somatic effectors, which are responsible for powerful motor movements, are linked to the ventral horn cell, a large neuron in the ventral portion of the gray matter. The autonomic effectors receive impulses from the lateral part of the gray matter. The smooth muscles that are supplied by these effectors maintain the tone of blood vessels walls, which facilitates the regulation of blood pressure. Glandular secretions controlled by autonomic effectors include external secretions, such as sweat, and internal ones, such as the hormone epinephrine secreted by the adrenal medulla of the brain. Some nerve fibers that connect with autonomic effectors also pass through the ventral roots of the spinal nerves by way of a ganglion located outside the spinal cord and are then distributed to smooth muscles and glands.

See also Autonomic nervous system ; Central nervous system ; Neural transmission: excitatory and inhibitory synapses; Neuron .



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