sensory neuron
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What is a sensory neuron?
Sensory neurons are nerve cells within the peripheral nervous system that transmit data about the internal and external environment to the central nervous system (CNS). They have sensory receptors in the ears, eyes, mouth, nose, skin, and internal organs. Sensory neurons, also known as afferent neurons, send information to the CNS, while motor neurons, known as efferent neurons, carry information away from the CNS.
Like other neurons, each sensory neuron has projections (dendrites and axons) that gather and transmit information. The specific shapes and sizes of sensory neurons vary according to their function. Many sensory neurons are enclosed in myelin, which increases the speed of signaling along the axon.
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Where are sensory neurons found in the body?
Sensory neurons are found throughout the peripheral nervous system (PNS), outside the brain and spinal cord, carrying information about external and internal environmental changes to the central nervous system (CNS). They gather information from sensory receptors located in specialized tissues of the ears, eyes, mouth, nose, skin, and internal organs. Sensory neuron cell bodies often cluster into ganglia outside the CNS. These neurons can be categorized as peripheral, responding to external stimuli like light and sound, or visceral, responding to internal stimuli like pain and blood pressure. Like other neurons, sensory neurons have a cell body and projections (dendrites and axons) that gather and transmit information.
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What is the main function of a sensory neuron?
Sensory neurons gather data from sensory receptors located in the ears, eyes, mouth, nose, skin, and internal organs about the internal and external environments and then transmit this data to the central nervous system (CNS).
Sensory neurons, also known as afferent neurons, transmit information to the CNS in the form of an action potential, which is a brief reversal of electric polarization of the membrane of a neuron or a muscle cell. The information then travels through a synapse, or junction between neurons. In response, the body maintains homeostasis, which is essential for survival, through self-regulation of physical systems.
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What are the main parts of a sensory neuron?
A sensory neuron transmits information about external and internal environmental changes to the central nervous system (CNS). Like other neurons, it consists of a cell body and projections (dendrites and axons) that transmit information.
Sensory neurons take information from sensory receptors and send it to the CNS in the form of an action potential. This information flows across a synapse, a junction between neurons.
The cell bodies of sensory neurons cluster into ganglia outside the CNS. Sensory neurons come in varied shapes and sizes based on their function. Many have myelin, a coating that increases the speed of signaling along the axon. An axon is the portion of the nerve cell that carries impulses away from the cell body.
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How do sensory neurons send information to the brain or spinal cord?
Sensory neurons carry information from the external and internal environments to the central nervous system (CNS). They are part of the peripheral nervous system, located outside the brain and spinal cord. Sensory neurons gather information from sensory receptors found in specialized tissues such as the ears, eyes, mouth, nose, skin, and internal organs.
Information transmits to the CNS as an action potential, which is a brief reversal of electric polarization on the neuron or muscle cell membrane. The information then flows across a synapse, a junction between neurons. In some instances, sensory neurons communicate directly with motor neurons through synapses for a fast reflex response. However, sensory neurons typically communicate with interneurons in the CNS before a response is sent back to the body.
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How do different types of sensory neurons help us sense things like touch, pain, or temperature?
Sensory neurons, located in the peripheral nervous system, gather information from sensory receptors in the ears, eyes, mouth, nose, skin, and internal organs and carry it to the central nervous system.
Different types of touch receptors in human skin, such as free nerve endings, hair follicle receptors, and Meissner corpuscles, respond to superficial light touch. Merkel and Ruffini endings detect touch pressure, while Pacinian corpuscles respond to vibration.
Pain receptors are nerve fibers excited by mechanical, thermal, or chemical stimuli. A delta fibers transmit sharp, localized pain, while C fibers are associated with lingering, poorly localized pain. Thermoreceptors detect hot and cold stimuli.
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sensory neuron, nerve cell that carries information about changes in external and internal environments to the central nervous system (CNS). Such neurons are part of the peripheral nervous system, which lies outside the brain and spinal cord. They collect information from so-called sensory receptors, which are located in specialized tissues of the ears, eyes, mouth, nose, skin, and internal organs. In general, sensory neurons are described as afferent (carrying information to the CNS), whereas motor neurons are described as efferent (carrying information away from the CNS).
Information from a sensory neuron is transmitted to the CNS in the form of an action potential, a brief reversal of electric polarization of the membrane of a neuron or a muscle cell. The information flows across a synapse, or junction between neurons. In a few cases, sensory neurons communicate directly with motor neurons via synapses, allowing for a very fast reflex response. In most cases, however, sensory neurons communicate with interneurons in the CNS before a response is sent back to the body.
Sensory neurons may be categorized as peripheral or visceral. Peripheral sensory neurons are activated by stimuli external to the body, such as light, touch, sound, scent, or taste. Visceral sensory neurons respond to stimuli that originate within the body, such as pain, blood pressure, hunger, or inflammation. The body’s response to visceral sensory information allows it to maintain homeostasis (the self-regulation of physical systems that are necessary for survival).
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Like other types of neurons, each sensory neuron has a cell body and projections (dendrites and axons) that gather and transmit information. The cell bodies of sensory neurons are often clustered into ganglia, which are located outside the CNS. The specific shapes and sizes of sensory neurons vary according to their function. Many sensory neurons are pseudounipolar; that is, each has one projection from the cell body that branches into two axons—one axon projecting to the periphery of the body and the other toward the CNS. Other sensory neurons are bipolar, each having two projections departing the cell body—one gathering information and the other passing information to other cells. In addition, many sensory neurons are enclosed in myelin, a coating consisting primarily of fatty materials that increases the speed of signaling along the axon. The layer of myelin varies in thickness, and it may be absent altogether.
Sensory neurons can be affected by diseases and disorders, such that affected individuals lose access to information about their external or internal environment. For example, humans rely on three types of cones (the light-sensitive cells in the retina of the eye that function in the perception of colour) to sense the full range of colours. In certain forms of colour blindness, however, only one or two types of cones are functional, resulting in a reduction of sensory information about colour in affected individuals’ environment. Another example of sensory impairment is hearing loss caused by repeated exposure to extremely loud noise that damages sensory receptors in the inner ear. Damage to auditory sensory neurons or to the temporal lobes of the brain, which normally process auditory information, can also result in hearing loss.
When sensory neurons become nonfunctional, the brain may adapt through a process known as neuroplasticity. For example, individuals who are blind from an early age can learn to use biosonar, or echolocation, to sense objects (similarly to bats). In this case, echoes are detected by auditory receptors and sensory neurons, but they are processed in the occipital lobe of the brain, which normally integrates visual, rather than auditory, information. Thus, individuals who are blind but who learn to employ biosonar can use auditory information to create mental images of their surroundings.