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The ulnar nerve is exclusively responsible for the innervations of the hypothenar eminence. Both nerves contribute to the innervations of the midpalmar group. [8] The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve.
The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar nerve innervates the remaining intrinsic muscles of the hand. [3] [4] All muscles of the hand are innervated by the brachial plexus (C5–T1) and can be classified by innervation: [1] [4] [5]
The action potential in a normal skeletal muscle cell is similar to the action potential in neurons. [61] Action potentials result from the depolarization of the cell membrane (the sarcolemma ), which opens voltage-sensitive sodium channels; these become inactivated and the membrane is repolarized through the outward current of potassium ions.
Any physical deformation of the corpuscle will cause sodium ions to enter it, creating an action potential in the corpuscle's nerve fiber. Since they are rapidly adapting or phasic , the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes).
They are responsible for the feeling of object slippage and play a major role in the kinesthetic sense and control of finger position and movement. Merkel and bulbous cells - slow-response - are myelinated; the rest - fast-response - are not. All of these receptors are activated upon pressures that distort their shape causing an action potential.
Spinal nerves transmit external sensations via sensory nerves to the brain through the spinal cord. [3] 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 .
The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. All receptors receive distinct physical stimuli and transduce the signal into an electrical action potential.
This includes sensations on various muscles, joints, and tendons. Each of these three categories have their own types of pathways and receptors. These pathways target the cerebellum in the brain. This section of the brain tracks what the muscles are doing at all times so any potential damage to this area can greatly affect one's senses. [8]