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A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
' pain receptor ') is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals [1] [2] [3] to the spinal cord and the brain. The brain creates the sensation of pain to direct attention to the body part, so the threat can be mitigated; this process is called nociception .
Each neurotransmitter has very specific degradation pathways at regulatory points, which may be targeted by the body's regulatory system or medication. Cocaine blocks a dopamine transporter responsible for the reuptake of dopamine. Without the transporter, dopamine diffuses much more slowly from the synaptic cleft and continues to activate the ...
Type Aα fibers include the type Ia and type Ib sensory fibers of the alternative classification system, and are the fibers from muscle spindle endings and the Golgi tendon, respectively. [1] Type Aβ fibres, and type Aγ, are the type II afferent fibers from stretch receptors. [1] Type Aβ fibres from the skin are mostly dedicated to touch.
A muscle spindle, with γ motor and Ia sensory fibers. A type Ia sensory fiber, or a primary afferent fiber, is a type of afferent nerve fiber. [1] 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.
There are four main types of sensory fibres responsible for somatosensation: Aα, Aβ, Aδ and C fibres (more details can be found at the axon page). The Aβ fibres are from cutaneous mechanoreceptors and respond to touch stimuli; the Aδ and C fibres are nociceptor afferents which respond to painful stimuli.
The periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. [1] [2] PAG is also the primary control center for descending pain modulation. It has enkephalin-producing cells that suppress pain.
C fibers respond to all kinds of physiological changes in the body. [8] For example, they can respond to hypoxia, hypoglycemia, hypo-osmolarity, the presence of muscle metabolic products, and even light or sensitive touch. [8] C fiber receptors include: C fiber nociceptors responsible for the second, burning pain; C fiber warming specific receptors