Motor control

Motor control is a person’s ability to carry out voluntary movements. Motor control can also be defined as the acquisition and development of distinct motor skills. It is important to note that motor control specifically refers to voluntary muscle movements and not to involuntary movements, such as shivering or flinching, which are controlled through different physiological systems. There are two types of motor control: gross motor control and fine motor control. Gross motor control refers to a person’s ability to move a large muscle group or specific body part. Waving one’s arm is an example of gross motor control. Fine motor control refers to a person’s ability to execute more precise movements. The abilities to write by hand and manipulate a pair of scissors are examples of fine motor control. Regardless of type, all motor control is made possible through integrated cooperation among the muscles, bones, and central nervous system.

Background

Motor control is primarily made possible by the nervous system. The nervous system is one of the body’s most important organ systems. It is divided into two separate components: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS consists of the nerves and ganglia that connect the CNS to the rest of the body. The PNS is further subdivided into the somatic motor system (SMS) and the autonomic motor system (AMS). The SMS branch of the PNS carries nerve impulses to the skeletal muscles that a person directly controls. The AMS branch, meanwhile, carries nerve impulses to muscles such as the heart that a person cannot directly control. The SMS is therefore the relevant branch of the PNS in terms of motor control.

The brain and spinal cord work together to coordinate all forms of voluntary movement. This includes the planning, preparation, and execution of motor movements. The brain and spinal cord also play a key role in the development of motor skills. One of the most important elements of the CNS’s ability to coordinate motor movements is the neuronal structure found within the spinal cord. This unique structure is composed of neurons. Neurons are unique cells that transmit nerve impulses through the nervous system. The neuronal structure in the spinal cord is made up of special neurons called motor neurons. Motor neurons are nerve cells that form part of the pathway along which nerve impulses travel from the CNS to other parts of the body. Motor neurons in the spinal cord synapse, or come together, with neurons connected to pathways in the brain and transmit information between the brain and various muscles throughout the body. By facilitating the exchange of information between the brain and muscles, motor neurons effectively make voluntary movements possible. This means that the SMS is the component of the nervous system that provides the underlying functionality essential to motor control. It also means that the SMS is a critical factor in the initial development of basic motor control during the early stages of life.

Overview

Motor control refers to a person’s ability to control the movements of his or her body. There are two types of motor control, including gross motor control and fine motor control. Gross motor control is defined as the ability to make large general movements like moving one’s arm or turning one’s head. Executing the kinds of movements associated with gross motor control requires coordination among muscles, bones, and nerves. The acquisition of gross motor control is a significant developmental milestone in infants that typically precedes the acquisition of fine motor control. Fine motor control is defined as the more precise coordination of muscles, bones, and nerves in order to carry out smaller, more exact movements. Writing by hand and picking up an object with the index finger and thumb are examples of fine motor control. The degree of fine motor control exhibited by a child is often used to estimate developmental age. Children develop fine motor control gradually over time as they learn and practice specific skills. To properly develop fine motor control, a child must have adequate awareness and planning, coordination, muscular strength, and normal sensation. Many simple motor control tasks can only be completed if the nervous system develops and functions correctly.

Two concepts that go hand-in-hand with motor control are motor planning and motor coordination. Motor planning refers to a person’s ability to organize his or her body’s action to be able to complete a given task. A motor plan for a particular task would include all the steps required to complete that task organized in the correct order. For example, the task of throwing a football to a friend would include steps for lifting the football, gripping it properly, aiming at the target, and propelling the football with the appropriate amount of force. People who experience difficulty with motor planning are said to have a medical condition known as dyspraxia. Children with dyspraxia typically have normal strength and muscle tone, but they lack the planning ability and coordination to use their muscles appropriately. Motor coordination refers to a person’s ability to use multiple body parts to complete a given task. To ride a bicycle, for example, one must use his or her arms and hands to steer while simultaneously using his or her legs and feet to pedal. Riding a bicycle also requires a person to have adequate bilateral coordination, which is the ability to use both sides of the body at the same time.

Acquiring gross and fine motor control is one of the most important aspects of childhood development. Learning basic motor control skills is a key part of childhood growth and a foundational element of early independence. Motor control develops over time through the course of three distinct stages of learning. The three phases of motor learning include the cognitive, associative, and autonomous stages. In the cognitive stage, movements are generally slow, inconsistent, and inefficient. Also during this stage, a great deal of attention to understand what body part or parts must move to complete a particular task is required. Often, most of the resulting movement is consciously controlled. In the associative stage, movements typically become more fluid, reliable, and efficient. This stage also sees changes in how movements are controlled. While some movements are still consciously controlled, others become automatic. By the autonomous stage, movements are accurate, consistent, and efficient. Movements are also predominantly automatic at the autonomous stage.

There are a variety of medical conditions that can impair motor control in one way or another. These conditions are generally grouped into one of three broad categories, including spinal cord disorders, cortical disorders, and subcortical disorders. Spinal cord disorders are conditions that specifically affect the spinal cord and disrupt the exchange of information between the brain and the rest of the body. The most common spinal cord disorders are those that are a direct result of physical injury. Nerve injuries can take a long period of time to heal. Some nerve injuries can even be permanent. When a nerve is injured and can no longer relay the messages that tell muscles to move, paralysis may result. This can be especially problematic in the case of spinal cord injuries. Severe spinal cord injuries can lead to complete paralysis of the limbs or trunk. In many instances, such injuries are irreversible, meaning that the resulting paralysis is permanent. As a result, spinal cord injuries can seriously or even completely disrupt motor control. There are also a number of spinal cord conditions not related to physical injury that can disrupt motor control. Some of these include myasthenia gravis, multiple sclerosis (MS), and motor neuron disease. Myasthenia gravis is a condition tied to a neurotransmitter called acetylcholine (ACh), which is released from motor neurons in the spinal cord. While ACh is released normally in people with myasthenia gravis, the number of ACh receptor cells on muscles is reduced. This can lead to muscle weakness or fatigue and a decline in motor control. MS is a condition in which a reduction in the fatty insulation found in neurons leads to a disruption in the flow of information within the brain and between the brain and the rest of the body. Motor neuron disease involves the death of motor neurons in the spinal cord. Cortical disorders are conditions that occur within the brain’s cerebral cortex. Some examples include hemiplegia, cerebral palsy, and apraxia. Hemiplegia is a form of brain damage caused by a loss of blood supply due to an aneurysm, a hemorrhage, or a blood clot. Cerebral palsy arises from fetal trauma or trauma suffered during birth. Apraxia is a form of brain damage that occurs when damage to a certain part of the brain leaves a person unable to perform a particular action. All these conditions can adversely affect motor control. Subcortical disorders are conditions that affect the brain’s basal ganglia, which are a group of structures located just below the cerebral cortex. Subcortical disorders progress slowly and lead to a gradual loss of motor control. These conditions arise as a result of damage, diseases, or disorders that affect either parts of the basal ganglia or the pathways between the basal ganglia and the cerebral cortex and thalamus. Some common subcortical disorders include Parkinson’s disease, Huntington’s disease, and Tourette syndrome.

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