Sensory vs Motor Neurons
Neurons are the functional and structural units of vertebrate nervous system. They make the communication network of the nervous system and transfer impulses between sensory organs, and central and peripheral nervous systems. There are about 200 billion neurons are integrated in the nerve network of an average person. Neuron is made up of a cell body containing a nucleus and other cell organelles. Other than the body, there are special branching from the cell body, which makes dendrites and axons. Usually axon is a long fiber; which carries messages away from the neuron, and dendrites are small branching responsible for receiving messages from the outer environment. Neurons can be classified based on their function as sensory neurons, motor neurons, and interneurons.
Sensory neurons convey sensory impulses from sensory organs toward the central nervous system, which includes the spinal cord and brain. They follow ascending, or afferent pathways, so called ‘afferent neurons’. The cell body of the sensory neurons is located in the peripheral sensory ganglia, in the peripheral nervous system. Sensory neurons are unipolar neurons with afferent fibers, which extend between sensory receptors and central nervous system. Sensory neurons gather information from external and internal environments through sensory receptors. Accordingly, sensory neurons can be divided into two types; (1) Somatic sensory neurons; which monitor outside environment and our position, (2) Visceral sensory neurons; which monitor internal body conditions and the status of organ systems. There are about 10 million sensory neurons in an adult human.
Motor neurons are responsible for carrying information from central nervous system to peripheral effectors in a peripheral tissue or organ. Human body has about half a million of motor neurons. Motor neuron is composed of a cell body, several dendrites and single axon. Its axon that travels away from central nervous system is called efferent fiber. The two major types of motor neurons are; (1) somatic motor neurons, which innervate skeletal muscles, and (2) visceral motor neurons, which innervate all peripheral effectors, except skeletal muscles.
What is the difference between Sensory and Motor Neurons?
• Sensory neurons bring sensory impulse from sensory organs to the central nervous system, whereas motor neurons carry motor impulses from the central nervous system to specific effectors.
• Sensory neurons are situated in the dorsal root ganglion of the spinal nerve, whereas motor neurons are situated in the ventral root ganglion of the spinal cord.
• Sensory neurons follow afferent pathways while motor neurons follow efferent pathways.
• An average adult has about 10 million sensory neurons and half a million of motor neurons.
• Motor neurons are multipolar, and sensory neurons are unipolar.
• Sensory neuron has afferent fiber, whereas motor neuron has efferent fiber.
• Motor neurons do not generate commands to communicate with muscles, but receive from sensory neurons.
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