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Hilton's law, espoused by John Hilton in a series of medical lectures given in 1860–1862, [1] is the observation that in the study of anatomy, the nerve supplying the muscles extending directly across and acting at a given joint not only supplies the muscle, but also innervates the joint and the skin overlying the muscle.
This magnified image of type 2 muscle fibers shows denervation atrophy occurring at the white spaces at the top left and bottom center of the image. The white space represents a disruption of the nerve fibers, resulting in a loss of nerve supply to the muscle fibers. Denervation is any loss of nerve supply regardless of the cause.
Muscles which possess more motor units (and thus have greater individual motor neuron innervation) are able to control force output more finely. Motor units are organized slightly differently in invertebrates : each muscle has few motor units (typically less than 10), and each muscle fiber is innervated by multiple neurons, including excitatory ...
Such near-continuous innervation can be thought of as a "default" or "steady state" condition for muscles. Both the extensor and flexor muscles are involved in the maintenance of a constant tone while at rest. In skeletal muscles, this helps maintain a normal posture. Resting muscle tone varies along a bell-shaped curve. Low tone is perceived ...
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. In the neuromuscular system, nerves from the central nervous system and the peripheral nervous system are linked and work together with muscles. [3]
Motor neural degeneration is the progressive weakening of neural tissues and connections in the nervous system. Muscles begin to weaken as there are no longer any motor nerves or pathways that allows for muscle innervation. Motor neuron diseases can be viral, genetic or be a result of environmental factors.
The levator palpebrae superioris receives motor innervation from the superior division of the oculomotor nerve. [1] [2] [3] The smooth muscle that originates from its undersurface, called the superior tarsal muscle is innervated by postganglionic sympathetic axons from the superior cervical ganglion.
The brachialis muscle is innervated by the musculocutaneous nerve, which runs on its superficial surface, between it and the biceps brachii. [2] However, in 70-80% of people, the muscle has double innervation with the radial nerve (C5-T1). The divide between the two innervations is at the insertion of the deltoid. [3]