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Tonic (physiology)
Tonic in physiology refers to a physiological response which is slow and may be graded. This term is typically used in opposition to a fast response. For instance, tonic muscles are contrasted by the more typical and much faster twitch muscles, while tonic sensory nerve endings are contrasted to the much faster phasic sensory nerve endings. Tonic muscles Tonic muscles are much slower than twitch fibers in terms of time from stimulus to full activation, time to full relaxation upon cessation of stimuli, and maximal shortening velocity.Kardong, K. 2008. Vertebrates: Comparative Anatomy, Function, Evolution. 5th edition. McGraw-Hill Science/Engineering/Math. These muscles are rarely found in mammals (only in the muscles moving the eye and in the middle ear), but are common in reptiles and amphibians. Tonic sensory receptors Tonic sensory input adapts slowly to a stimulushttp://caspar.bgsu.edu/~courses/Glossary.htm and continues to produce action potentials over the duration of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensory Neuron
Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord. The sensory information travels on the afferent nerve fibers in a sensory nerve, to the brain via the spinal cord. The stimulus can come from ''exteroreceptors'' outside the body, for example those that detect light and sound, or from ''interoreceptors'' inside the body, for example those that are responsive to blood pressure or the sense of body position. Types and function Different types of sensory neurons have different sensory receptors that respond to different kinds of stimuli. There are at least six external and two internal sensory receptors: External receptors External receptors that respond to stimuli from outside the body are called ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action Potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells. In neurons, action potentials play a central role in cell-cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pain Receptors
Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a painful stimulus, convert it to a molecular signal, and recognize and characterize the signal in order to trigger an appropriate defense response. In nociception, intense chemical (e.g., capsaicin present in Chili pepper or Cayenne pepper), mechanical (e.g., cutting, crushing), or thermal (heat and cold) stimulation of sensory neurons called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses to protect the organism against an aggression and usually results in a subjective experience, or perception, of pain in sentient beings. Detection of noxious stimuli Potentially damaging mechanical, thermal, and chemical stimuli are detected ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joint Capsule
In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint. Each joint capsule has two parts: an outer fibrous layer or membrane, and an inner synovial layer or membrane. Membranes Each capsule consists of two layers or membranes: * an outer (fibrous membrane, ''fibrous stratum'') composed of avascular white fibrous tissue * an inner ('' synovial membrane'', ''synovial stratum'') which is a secreting layer On the inside of the capsule, articular cartilage covers the end surfaces of the bones that articulate within that joint. The outer layer is hi ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscle Spindle
Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be processed by the brain as proprioception. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, for example, by activating motor neurons via the stretch reflex to resist muscle stretch. The muscle spindle has both sensory and motor components. * Sensory information conveyed by primary type Ia sensory fibers which spiral around muscle fibres within the spindle, and secondary type II sensory fibers * Activation of muscle fibres within the spindle by up to a dozen gamma motor neurons and to a lesser extent by one or two beta motor neurons Structure Muscle spindles are found within the belly of a skeletal muscle. Muscle spindles are fusiform (spindle-shaped), and the spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ruffini Corpuscle
The Bulbous corpuscle or Ruffini ending or Ruffini corpuscle is a slowly adapting mechanoreceptor located in the skin, cutaneous tissue between the dermal papillae and the hypodermis. It is named after Angelo Ruffini. Structure Ruffini corpuscles are enlarged dendritic endings with elongated capsules. Function This spindle-shaped receptor is sensitive to skin stretch, and contributes to the kinesthetic sense of and control of finger position and movement. They are at the highest density around the fingernails where they act in monitoring slippage of objects along the surface of the skin, allowing modulation of grip on an object. Ruffini corpuscles respond to sustained pressure and show very little adaptation. Ruffinian endings are located in the deep layers of the skin, and register mechanical deformation within joints, more specifically angle change, with a specificity of up to 2.75 degrees, as well as continuous pressure states. They also act as thermoreceptors that respond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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