motor system

(noun)

The part of the central nervous system that is involved with movement. It consists of the pyramidal and extrapyramidal systems.

Related Terms

Examples of motor system in the following topics:

  • Organization of Motor Neuron Pathways

    • The motor system is the part of the central nervous system that is involved with movement.
    • The motor system is the part of the central nervous system that is involved with movement.
    • It consists of the pyramidal and extrapyramidal system.
    • The motor pathway, also called the pyramidal tract or the corticospinal tract, serves as the motor pathway for upper motor neuronal signals coming from the cerebral cortex and from primitive brainstem motor nuclei.
    • The midbrain nuclei include four motor tracts that send upper motor neuronal axons down the spinal cord to lower motor neurons.

  • Functions of the Nervous System

    • The nervous system has three overlapping functions.
    • These functions are based on the sensory input,  integration and motor output.
    • The nervous system is a highly integrated system.
    • The nervous system activates effector organs such as muscles and glands to cause a response called the motor input.
    • Once the response is activated, the nervous system is able to send signals via motor output to muscles or glands to initiate the response.

  • Organization of the Nervous System

    • The nervous system is an organ system that coordinates our actions by transmitting signals between different parts of our bodies.
    • The peripheral nervous system (PNS) consists of sensory neurons, motor neurons, and neurons that communicate either between subdivisions of the PNS or connect the PNS to the CNS .
    • The nervous system has three broad functions: sensory input, information processing, and motor output .
    • After information is processed, signals return to the PNS by way of motor neurons to muscles and glands, which respond with a motor output.
    • Gross organization of the nervous system, with the peripheral nervous system, the spinal, and the cortical levels.

  • Functions of the Brain Stem

    • Though small, it is an extremely important part of the brain, as the nerve connections of the motor and sensory systems from the main part of the brain that communicate with the peripheral nervous system pass through the brainstem.
    • It regulates the central nervous system (CNS) and is pivotal in maintaining consciousness and regulating the sleep cycle.
    • The midbrain (mesencephalon) is associated with vision, hearing, motor control, sleep and wake cycles, alertness, and temperature regulation.
    • Descending tracts are upper motor neurons destined to synapse on lower motor neurons in the ventral horn and intermediate horn of the spinal cord.
    • The brainstem also has integrative functions, including cardiovascular system control, respiratory control, pain sensitivity control, alertness, awareness, and consciousness.

  • Comparing the Somatic and Autonomic Nervous Systems

    • The peripheral nervous system (PNS, see ) is divided into the somatic nervous system and the autonomic nervous system.
    • The somatic nervous system controls all voluntary muscular systems within the body, and also mediates involuntary reflex arcs.
    • Spinal nerves are peripheral nerves that carry sensory information into the spinal cord and motor commands.
    • Association nerves integrate sensory input and motor output, numbering in the thousands.
    • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

  • Motor Units

    • The motor unit is the functional unit of muscle contraction and includes the motor nerve fiber and the muscle fibers it innervates.
    • A motor unit consists of the motor neuron and the grouping of muscle fibers innervated by the neuron.
    • Thus, small motor units can exercise greater precision of movement compared to larger motor units.
    • Groups of motor units are innervated to coordinate contraction of a whole muscle and generate appropriate movement; all of the motor units within a muscle are considered a motor pool.
    • These multiple motor units of different sizes within a motor pool allow for very fine control of force either spatially or temporally.

  • Branches of Spinal Nerves

    • The dorsal ramus: Contains nerves that serve the dorsal portions of the trunk carrying visceral motor, somatic motor, and sensory information to and from the skin and muscles of the back.
    • The ventral ramus: Contains nerves that serve the remaining ventral parts of the trunk and the upper and lower limbs carrying visceral motor, somatic motor, and sensory information to and from the ventrolateral body surface, structures in the body wall, and the limbs.
    • The rami communicantes: Contain autonomic nerves that carry visceral motor and sensory information to and from the visceral organs.

  • Neural Mechanisms (Cortex)

    • The primary motor cortex is the neural center for voluntary respiratory control.
    • More broadly, the motor cortex is responsible for initiating any voluntary muscular movement.
    • It also provides parasympathetic stimulation for the heart and the digestive system.
    • Topography of the primary motor cortex, on an outline drawing of the human brain.
    • Each part of the primary motor cortex controls a different part of the body.

  • Motor Areas

    • The motor areas of the brain are located in both hemispheres of the cortex.
    • The right half of the motor area controls the left side of the body, and the left half of the motor area controls the right side of the body.
    • Premotor cortex: Located anterior to the primary motor cortex and responsible for some aspects of motor control.
    • Various experiments examining the motor cortex map showed that each point in motor cortex influences a range of muscles and joints, indicating significant overlapping in the map.
    • $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.

  • Hypotonia and Hypertonia

    • Hypertonia is a reduction in the ability of a muscle to stretch due to increased muscle tension; it is caused by lesions to upper motor neurons.
    • The loss of motor neuron control leads to increased excitability of muscle fibers.
    • Hypotonia can result from several diseases and disorders affecting motor control.
    • Hypotonia is thought to be associated with the disruption of afferent input from stretch receptors and/or lack of the cerebellum's facilitatory efferent influence on the fusimotor system (the system that innervates intrafusal muscle fibers thereby controlling muscle spindle sensitivity ).
    • A muscle spindle, with γ motor neurons, sensory fibers and proprioceptor that detect the amount and rate of change of length in a muscle.