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Nuclear Chain Fiber
A nuclear chain fiber is a specialized sensory organ contained within a muscle. Nuclear chain fibers are intrafusal fibers that, along with nuclear bag fibers, make up the muscle spindle responsible for the detection of changes in muscle length. There are 3–9 nuclear chain fibers per muscle spindle that are half the size of the nuclear bag fibers. Their nuclei are aligned in a chain and they excite the secondary nerve. They are static, whereas the nuclear bag fibers are dynamic in comparison. The name "nuclear chain" refers to the structure of the central region of the fiber, where the sensory axons wrap around the intrafusal fibers. The secondary nerve association involves an efferent and afferent pathway that measure the stress and strain placed on the muscle (usually the extrafusal fibers connected from the muscle portion to a bone). The afferent pathway resembles a spring wrapping around the nuclear chain fiber and connecting to one of its ends away from the bone. ... [...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), a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Series And Parallel Circuits
Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is an electrical component (e.g. a resistor) or an electrical network (e.g. resistors in series) is a matter of perspective. This article will use "component" to refer to a two-terminal "object" that participates in the series/parallel networks. Components connected in series are connected along a single "electrical path", and each component has the same electric current through it, equal to the current through the network. The voltage across the network is equal to the sum of the voltages across each component. Components connected in parallel are connected along multiple paths, and each component has the same voltage across it, equal to the voltage across the network. The current through the network is equal to the sum of the currents thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Distinct Cell Types In The Adult Human Body
The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cells may be classified by their physiological function, histology (microscopic anatomy), lineage, or gene expression. Total number of cells The adult human body is estimated to contain about 30 trillion (3×1013) human cells, with the number varying between 20 and 100 trillion depending on factors such as sex, age, and weight. Additionally, there are approximately an equal number of bacterial cells. The exact count of human cells has not yet been empirically measured in its entirety and is estimated using different approaches based on smaller samples of empirical observation. It is generally assumed that these cells share features with each other and thus may be organized as belonging to a smaller number of types. Classification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Motor Neurons
A gamma motor neuron (γ motor neuron), also called gamma motoneuron, or fusimotor neuron, is a type of lower motor neuron that takes part in the process of muscle contraction, and represents about 30% of ( Aγ) fibers going to the muscle. Like alpha motor neurons, their cell bodies are located in the anterior grey column of the spinal cord. They receive input from the reticular formation of the pons in the brainstem. Their axons are smaller than those of the alpha motor neurons, with a diameter of only 5 μm. Unlike the alpha motor neurons, gamma motor neurons do not directly adjust the lengthening or shortening of muscles. However, their role is important in keeping muscle spindles taut, thereby allowing the continued firing of alpha neurons, leading to muscle contraction. These neurons also play a role in adjusting the sensitivity of muscle spindles. The presence of myelination in gamma motor neurons allows a conduction velocity of 4 to 24 meters per second, signifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinal Cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called the central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system. In humans, the spinal cord is a continuation of the brainstem and anatomically begins at the occipital bone, passing out of the foramen magnum and then enters the spinal canal at the beginning of the cervical vertebrae. The spinal cord extends down to between the first and second lumbar vertebrae, where it tapers to become the cauda equina. The enclosing bony vertebral column protects the relatively shorter spinal cord. It is around long in adult men and around long in adult women. The diam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Posterior Horn Of Spinal Cord
The grey columns are three regions of the somewhat ridge-shaped mass of grey matter in the spinal cord. These regions present as three columns: the anterior grey column, the posterior grey column, and the lateral grey column, all of which are visible in cross-section of the spinal cord. The anterior grey column is made up of alpha motor neurons, gamma motor neurons, and small neurons thought to be interneurons. It affects the skeletal muscles. The posterior grey column receives several types of sensory information regarding touch and sensation from receptors in the skin, bones, and joints, including fine touch, proprioception, and vibration. It contains the cell bodies of second-order sensory neurons and their synapses with the pseudounipolar first-order sensory neurons (whose cell bodies are located within the sensory ganglia (a.k.a. dorsal root ganglia)). The lateral grey column is only present in the thoracic region and upper lumbar segments (T1-L2). It contains ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleus Proprius
The nucleus proprius of spinal cord is a layer of the spinal cord adjacent to the substantia gelatinosa. The nucleus proprius can be found in the gray matter in all levels of the spinal cord. It constitutes the first synapse of the posterior gray column carrying proprioception, two-point discrimination, and vibration sensations from peripheral nerves. Cells in this nucleus project to deeper laminae of the spinal cord, to the posterior column nuclei, and to other supraspinal relay centers including the midbrain, thalamus, and hypothalamus. Rexed laminae III and IV make up the nucleus proprius. The neurons of the substantia gelatinosa of Rolando The apex of the posterior grey column, one of the three grey columns of the spinal cord, is capped by a V-shaped or crescentic mass of translucent, gelatinous neuroglia, termed the substantia gelatinosa of Rolando (or SGR) (or gelatinous substan ... (Rexed lamina II) are involved in sensing pain and temperature. References External ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type II Sensory Fibers
Group Aβ of the type II sensory fiber is a type of sensory fiber, the second of the two main groups of touch receptors. The responses of different type Aβ fibers to these stimuli can be subdivided based on their adaptation properties, traditionally into rapidly adapting (RA) or slowly adapting (SA) neurons. Type II sensory fibers are slowly-adapting (SA), meaning that even when there is no change in touch, they keep respond to stimuli and fire action potentials. In the body, Type II sensory fibers belong to pseudounipolar neurons. The most notable example are neurons with Merkel cell-neurite complexes on their dendrites (sense static touch) and Ruffini endings (sense stretch on the skin and over-extension inside joints). Under pathological conditions they may become hyper-excitable leading to stimuli that would usually elicit sensations of tactile touch causing pain. These changes are in part induced by PGE2 which is produced by COX1, and type II fibers with free nerve end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Ia Sensory Fibers
A type Ia sensory fiber, or a primary afferent fiber, is a type of afferent nerve fiber. It is the sensory fiber of a stretch receptor called the muscle spindle found in muscles, which constantly monitors the rate at which a muscle stretch changes. The information carried by type Ia fibers contributes to the sense of proprioception. Function of muscle spindles For the body to keep moving properly and with finesse, the nervous system has to have a constant input of sensory data coming from areas such as the muscles and joints. In order to receive a continuous stream of sensory data, the body has developed special sensory receptors called proprioceptors. Muscle spindles are a type of proprioceptor, and they are found inside the muscle itself. They lie parallel with the contractile fibers. This gives them the ability to monitor muscle length with precision. Types of sensory fibers This change in length of the spindle is transduced (transformed into electric membrane potentials) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Efferent Nerve Fiber
Efferent nerve fibers are axons (nerve fibers) of efferent neurons that exit a particular region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS). The efferent fiber is a long process projecting far from the neuron's body that carries nerve impulses away from the central nervous system toward the peripheral effector organs (muscles and glands). A bundle of these fibers constitute an efferent nerve. The opposite direction of neural activity is afferent conduction, which carries impulses by way of the afferent nerve fibers of sensory neurons. In the nervous system, there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons, and motor neurons. In the CNS, afferent and efferent projections can be from the perspective of any given brain region. That is, each brain region has its own unique set of affe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Afferent Nerve Fiber
Afferent nerve fibers are axons (nerve fibers) of sensory neurons that carry sensory information from sensory receptors to the central nervous system. Many afferent projections ''arrive'' at a particular brain region. In the peripheral nervous system, afferent nerve fibers are part of the sensory nervous system and arise from outside of the central nervous system. Sensory and mixed nerves contain afferent fibers. Structure Afferent neurons are pseudounipolar neurons that have a single process leaving the cell body dividing into two branches: the long one towards the sensory organ, and the short one toward the central nervous system (e.g. spinal cord). These cells do have sensory afferent dendrites, similar to those typically inherent in neurons. They have a smooth and rounded cell body located in the ganglia of the peripheral nervous system. Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Bag Fibers
A nuclear bag fiber is a type of intrafusal muscle fiber that lies in the center of a muscle spindle. Each has many nuclei concentrated in bags and they cause excitation of the primary sensory fibers. There are two kinds of bag fibers based upon contraction speed and motor innervation. #BAG2 fibers are the largest. They have no striations in middle region and swell to enclose nuclei, hence their name. #BAG1 fibers, smaller than BAG2. Both bag types extend beyond the spindle capsule. These sense dynamic length of the muscle. They are sensitive to length and velocity. See also * Nuclear chain fiber * List of distinct cell types in the adult human body The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cell ... References External links * http://www.unmc.edu/Physiology/Mann/mann11.html ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
