The mechanism of the reflex arc

Sensory neurons (or neurones) are nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses. For example, some sensory neurons respond to tactile stimuli and can activate motor neurons in order to achieve muscle contraction. Such connections between sensory and motor neurons underlie motor reflex loops and several forms of involuntary behavior, including pain avoidance. In humans, such reflex circuits are commonly located in the spinal cord. Image File history File links ReflexArc1. ... Image File history File links ReflexArc1. ... A reflex arc is the neural pathway mediating a reflex. ... Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... In biology and ecology, an organism (in Greek organon = instrument) is a living complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole. ... The article on electrical energy is located elsewhere. ... Tactition is the sense of pressure perception. ... In vertebrates, motoneurons (also called motor neurons) are efferent neurons that originate in the spinal cord and synapse with muscle fibers to facilitate muscle contraction and with muscle spindles to modify proprioceptive sensitivity. ... A top-down view of skeletal muscle Muscle is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... A reflex action or reflex is a biological control system linking stimulus to response and mediated by a reflex arc. ... A reflex action or reflex is a biological control system linking stimulus to response and mediated by a reflex arc. ... In cognitive neuroscience, a neural network (also known as a neuronal network or biological neural network to distinguish from artificial neural networks) is a population of interconnected neurons. ... Cross-section through cervical spinal cord. ...

In complex organisms, sensory neurons relay their information to the central nervous system or in less complex organisms, such as the hydra, directly to motor neurons. In complex organisms like humans most sensory neurons also transmit information to the brain, where it can be further processed and acted upon. For example, olfactory sensory neurons make synapses with neurons of the olfactory bulb, where the sense of olfaction (smell) is processed. This information can be used by organisms to make decisions on whether to eat a particular piece of food, or whether a potential partner is ready to mate. A diagram showing the CNS: 1. ... Species Hydra americana Hydra attenuata Hydra canadensis Hydra carnea Hydra cauliculata Hydra circumcincta Hydra hymanae Hydra littoralis Hydra magnipapillata Hydra minima Hydra oligactis Hydra oregona Hydra pseudoligactis Hydra rutgerensis Hydra utahensis Hydra viridis Hydra is a genus of simple, fresh-water animals possessing radial symmetry. ... In vertebrates, motoneurons (also called motor neurons) are efferent neurons that originate in the spinal cord and synapse with muscle fibers to facilitate muscle contraction and with muscle spindles to modify proprioceptive sensitivity. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... An olfactory receptor neuron, also called an olfactory sensory neuron, is the primary transduction cell for olfaction in the olfactory system. ... Illustration of the major elements in a prototypical synapse. ... Vesalius Fabrica, 1543. ... Senses are the physiological methods of perception. ... Olfaction, the sense of odor (smell), is the detection of chemicals dissolved in air (or in water, by animals that live under water). ... Coition of a Hemisected Man and Woman (c. ...

At the molecular level, sensory receptors located on the cell membrane of sensory neurons are responsible for the conversion of stimuli into electrical impulses. The type of receptor employed by a given sensory neuron determines the type of stimuli it will be sensitive to. For example, neurons containing mechanoreceptors are sensitive to tactile stimuli, while olfactory receptors make a cell sensitive to odors. Molecular biology is the study of biology at a molecular level. ... In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. ... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. ... Olfactory receptors are a type of G protein-coupled receptor in olfactory receptor neurons. ...

See also

• Type Ia sensory fiber
• Sensory nerves
• Afferent nerve