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The somatic nervous system (SNS), also known as voluntary nervous system, is a part of the peripheral nervous system (PNS) that links brain and spinal cord to skeletal muscles under conscious control, as well as to sensory receptors in the skin. [1] [2] The other part complementary to the somatic nervous system is the autonomic nervous system ...
Motor control includes conscious voluntary movements, subconscious muscle memory and involuntary reflexes, [1] as well as instinctual taxes. To control movement, the nervous system must integrate multimodal sensory information (both from the external world as well as proprioception ) and elicit the necessary signals to recruit muscles to carry ...
The motor neuron sends an electrical impulse to a muscle. When the neuron in the cortex becomes active, it causes a muscle contraction. The greater the activity in the motor cortex, the stronger the muscle force. Each point in the motor cortex controls a muscle or a small group of related muscles. This description is only partly correct.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
A tetanic contraction is caused by constant, very high frequency stimulation - the action potentials come at such a rapid rate that individual twitches are indistinguishable, and tension rises smoothly eventually reaching a plateau. [5] The interface between a motor neuron and muscle fiber is a specialized synapse called the neuromuscular junction.
Because of this, Hesterlee says the disorder "can affect voluntary muscles − particularly those that control eye and eyelid movement, facial expressions, swallowing and breathing."
The motor unit consists of a voluntary alpha motoneuron and all of the collective muscle fibers that it controls, known as the effector muscle. The alpha motoneuron communicates with acetylcholine receptors on the motor end plate of the effector muscle. Reception of acetylcholine neurotransmitters on the motor end plate causes contraction of ...
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 ...