Loss of motor function is called

Muscle function loss: MedlinePlus Medical Encyclopedi

  1. Muscle function loss is when a muscle does not work or move normally. The medical term for complete loss of muscle function is paralysis
  2. Loss or impairment of motor function in a part due to a lesion of the neural or muscular mechanism; also, by analogy, impairment of sensory function (sensory paralysis). Paralysis is a symptom of a wide variety of physical and emotional disorders rather than a disease in itself
  3. MSA is a progressive, neurodegenerative disease affecting movement, blood pressure and other body functions. Because symptoms, onset and severity of MSA vary from person to person, differing ranges of symptoms were designated initially as three different diseases: Shy-Drager syndrome, striatonigral degeneration and olivopontocerebellar atrophy. All of these now are classified under MSA
  4. Total muscle function loss, or paralysis, affects your entire body. It's often seen in people with severe spinal cord injuries. If a loss of muscle function affects both the top half and bottom..
  5. decreased or loss of motor function due to problem with motor nerve or muscle fibers. paraplegia. impalement or loss of motor , impairment/loss of movement in the lower part of the body. paresthesia. abnormal sensation of numbness and tingling without objective cause. point localization
  6. utes to up to a few months. Beside the motor symptoms of paralysis, It is also called global paralysis. Paralysis that follows a particular pattern
  7. Uncoordinated movement is also known as lack of coordination, coordination impairment, or loss of coordination. The medical term for this problem is ataxia. For most people, body movements are..

Transient paralysis definition of transient paralysis by

Hemiparesis with origin in the lower section of the brain creates a condition known as ataxia, a loss of both gross and fine motor skills, often manifesting as staggering and stumbling. Pure Motor Hemiparesis, a form of hemiparesis characterized by sided weakness in the leg, arm, and face, is the most commonly diagnosed form of hemiparesis These non-motor symptoms can include constipation, difficulty with urination, sexual dysfunction, loss of smell and/or taste, fatigue, depression, low blood pressure on standing (orthostasis), and REM sleep behavior disorder (RBD). Some of these non-motor symptoms are however very common in the general population and other disorders as. Amyotrophic Lateral Sclerosis (ALS) ALS affects both your upper and lower motor neurons. With ALS, you gradually lose control over the muscles that help you walk, talk, chew, swallow, and breathe... Brain hypoxia is a medical emergency because the brain needs a constant supply of oxygen and nutrients to function properly. There are several causes of brain hypoxia. They include drowning,..

One major symptom of MS in the hands is a loss of dexterity. Fine-motor skills may regress or disappear. You might have difficulty with activities such picking things up, maintaining a hold on items, have difficulty writing or buttoning clothing, or have trouble controlling eating utensils. It may be even be painful to do so Paralysis, loss of voluntary movement, or weakness that usually affects one side of the body, usually the side opposite to the side damaged by the stroke (such as the face, an arm, a leg, or the entire side of the body). Paralysis on one side of the body is called hemiplegia; weakness on one side is called hemiparesis A loss of fine motor skills is a common symptom of neurologic conditions. Try these creative ways to improve dexterity or adapt to changes. As a child growing up in Baltimore, Carl Schuetz was always creative, spending hours in his room drawing and writing (PD) belongs to a group of conditions called motor system disorders, which are the result of the loss of dopamine-producing brain cells. The four primary symptoms of PD are tremor, or trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability, or. The study of motor behavior in terms of relatively permanent gains in motor skill capability as a result of practice or experience is called _____. aging The change process occurring with the passage of time and leading to loss of adaptability or full function is called ____________

Muscle atrophy can occur due to poor nutrition, age, and genetics. Symptoms vary, and treatment may include physical therapy, functional electric stimulation, or surgery. Learn more about muscle. Essential tremor (previously also called benign essential tremor or familial tremor) is one of the most common movement disorders. The exact cause of essential tremor is unknown. For some people this tremor is mild and remains stable for many years Tetraplegia, also known as quadriplegia, is paralysis caused by illness or injury that results in the partial or total loss of use of all four limbs and torso; paraplegia is similar but does not affect the arms. The loss is usually sensory and motor, which means that both sensation and control are lost. The paralysis may be flaccid or spastic

Movement Disorders - Classifications, Symptoms and Treatment

  1. Common peroneal nerve dysfunction is a type of peripheral neuropathy (damage to nerves outside the brain or spinal cord). This condition can affect people of any age. Dysfunction of a single nerve, such as the common peroneal nerve, is called a mononeuropathy. Mononeuropathy means the nerve damage occurred in one area
  2. Cerebellar degeneration. This is the loss of nerve cells in the area of the brain that controls muscle functions and balance (cerebellum)
  3. Besides a loss of sensation or motor function, individuals with spinal cord injury also experience other changes. For example, they may experience dysfunction of the bowel and bladder. Very high injuries (C-1, C-2) can result in a loss of many involuntary functions, including the ability to breathe, necessitating breathing aids such as.
  4. Parkinsonism, named after English surgeon James Parkinson, who described the condition in 1817 as the shaking palsy, is a chronic neurological disorder involving progressive loss of motor function. Although no treatment is known to halt the advance of the disease, levodopa and certain other drug
  5. Spinal cord injury (SCI) is an injury to the spinal cord that results in temporary or permanent changes in the spinal cord's normal motor, sensory, or autonomic function. People who sustain a spinal cord injury often have permanent and profound neurologic deficits and accompanying disability
  6. spinal nerves is called a dermatome. Regional loss of sensory or motor function (due to trauma or compression) is called peripheral neuropathy. Key • Each peripheral nerve provides sensory and/or motor innervation to specific structures. Nerve Plexuses, p. 431 Figure 13-9 • Skeletal muscles of the neck and limbs are controlled by nerves.
  7. Amnesia is memory loss that may be caused by a head injury, a stroke, substance abuse, or a severe emotional event, such as from combat or a motor vehicle accident. Depending upon the cause, amnesia may be either temporary or permanent. Confusion or decreased alertness may be the first symptom of a serious illness, particularly in older adults

As it turns out, very few patients who have loss of S4/5 function recovered such function spontaneously. As shown in figure 3 below, while this simplifies the criterion for assessing whether an injury is complete, the ASIA classification committee decided that both motor and sensory levels should be expressed on each side separately, as. 0 3. Minutes. 5 4. Seconds. Head injuries from trauma may result in a loss of motor skills. Parkinson's disease and other conditions that affect nerve cells in the brain can cause people to lose motor skills. Alcohol impairment may lead to a temporary loss of motor skills. Disorders that affect nerve cells of the brain, such as Parkinson's.

Muscle Function Loss: Causes, Types, and Treatment

Primary motor cortex damage causes problems with muscle movement and coordination in many brain injury patients. Fortunately, because of the brain's neuroplasticity, it is possible to reverse some of the effects of primary motor cortex damage. To help you overcome this type of brain damage, today you will learn what the primary motor cortex is, Primary Motor Cortex Damage: Definition. After 2 years, irreversible muscle fibrosis has occurred along with muscle degeneration, leading to a permanent loss of functional muscle tissue. Sensory end-organs such as Paccinian corpuscles, Meissner corpuscles and Merkel cells can last up to 2-3 years, so sensory function can still be recovered even after muscle function is permanently. This is an inherited condition that affects lower motor neurons. A defect in a gene called SMN1 causes spinal muscular atrophy. This gene makes a protein that protects your motor neurons. Without.

Selective loss of sensation in these modalities can aid in localization of the lesion and in understanding its mechanism. Sensory function can be divided clinically into primary and secondary (aka cortical) modalities. Primary modalities include light touch, pressure, pain, temperature, proprioception, and vibration sense Cerebellar ataxia is reflected in uncoordinated motor activity of the limbs, head and neck, taking large steps, stepping oddly, head tremors, body tremors and swaying of the torso. There is an inadequacy in the performance of motor activity and in strength preservation. Symptoms and Types. Weakness of the limbs May affect one, two, or all of. Motor neurone disease is a rare condition that progressively damages parts of the nervous system. This leads to muscle weakness, often with visible wasting. Motor neurone disease, also known as amyotrophic lateral sclerosis (ALS), occurs when specialist nerve cells in the brain and spinal cord called motor neurones stop working properly

When the neurons in the substantia nigra are damaged in large numbers, the loss of dopamine causes impaired movement and the motor symptoms of PD: tremor, rigidity, impaired balance, and loss of spontaneous movement. Research has shown that people with PD have lost 60-80% or more of the neurons that produce dopamine by the time symptoms appear. The frontal lobes are also involved in language, particularly linking words to form sentences, and in motor functions, such as moving the arms, legs, and mouth. The temporal lobes, located below and to the side of each frontal lobe on the right and left sides of the brain, contain essential areas for memory but also play a major role in.

Motor nerve damage, or neuropathy, is a disorder where the nervous system fails to function correctly. Put simply, your nerves act as the internal wiring system in your body. They are responsible for transporting information about your physical environment to the brain, like pain and temperature sensations Induction Motor Parameter Measurement 2 Note that the core loss resistor element is added to account for hysteresis and eddy currents. Since these losses are a function of frequency, this term is only approximate and is sometimes not included in the model. The circuit electrical quantities are Disturbances of motor (movement or muscle) function include three disorders that are a part of the frontotemporal degeneration spectrum that produce changes in muscle or motor functions with or without behavior (bvFTD) or language (PPA) problems: Amyotrophic lateral sclerosis (ALS), which causes muscle weakness or wasting Motor function assessment is checking a person's gait, muscle strength and coordination. The test where a person is asked to touch their nose then the finger of the examiner, with eyes open then with eyes closed is an example of how coordination may be evaluated

ALS causes the motor neurons to gradually deteriorate, and then die. Motor neurons extend from the brain to the spinal cord to muscles throughout the body. When motor neurons are damaged, they stop sending messages to the muscles, so the muscles can't function. ALS is inherited in 5% to 10% of people. For the rest, the cause isn't known In ALS, motor nerve cells (neurons) waste away or die, and can no longer send messages to muscles. This eventually leads to muscle weakening, twitching, and an inability to move the arms, legs, and body. The condition slowly gets worse. When the muscles in the chest area stop working, it becomes hard or impossible to breathe A complete SCI produces total loss of all motor and sensory function below the level of injury. Nearly 50% of all SCIs are complete. Both sides of the body are equally affected. Even with a complete SCI, the spinal cord is rarely cut or transected. More commonly, loss of function is caused by a contusion or bruise to the spinal cord or by.

Neuro Jarvis (Quiz 6) Flashcards Quizle

  1. al: Divided into opthlamic, maxillary, and mandibular branches. Mediates general sensation of the face, eyes, nose, and mouth. Innervates the muscles of mastication: Sensory afferent and motor efferent: Loss of general sensation in the face, loss of corneal reflex, deviation of the jaw to.
  2. Aphasia is a disorder that results from damage to portions of the brain that are responsible for language. For most people, these areas are on the left side of the brain. Aphasia usually occurs suddenly, often following a stroke or head injury, but it may also develop slowly, as the result of a brain tumor or a progressive neurological disease
  3. Atrophy is the medical term for getting smaller, which is what generally happens to muscles when they're not stimulated by nerve cells. SMA involves the loss of nerve cells called motor neurons in the spinal cord and is classified as a motor neuron disease. In the most common form of SMA (chromosome 5 SMA, or SMN-related SMA), there is wide.
  4. The 3 phase motors must be connected to rated voltage and load for proper working. If due to some reasons, one phase of the motor gets disconnected, the motor will continue to run from the active 2 phase supply. This is called Single phasing. If t..
  5. Loss of Neuronal Connections and Cell Death. In Alzheimer's disease, as neurons are injured and die throughout the brain, connections between networks of neurons may break down, and many brain regions begin to shrink. By the final stages of Alzheimer's, this process—called brain atrophy—is widespread, causing significant loss of brain.
  6. That meant that any damage that occurred to the brain in adulthood, such as loss of motor function because of a stroke, was permanent. However, as our scientific knowledge advanced over the course of the 20th century, research on brain development and injury recovery suggested the opposite

If motor impairments are the only secondary effect, then this type of stroke is also known as a pure motor stroke. Learn more about internal capsule stroke » Left Hemisphere vs Right Hemisphere Stroke. Along with different lobes and structures, the brain is also divided into two halves, called hemispheres The motor system can indicate the loss of input to the ventral horn in the lumbar enlargement where motor neurons to the leg are found, but motor function in the trunk is less clear. The left and right anterior corticospinal tracts are directly adjacent to each other Depending on how severe the hit to your head was, the memory issues might go away or be permanent. A stroke happens when a blockage or weak area in a blood vessel cuts off blood flow to part of. Muscles in elderly adults have fewer, but on average larger and slower, motor units, with important implications for both motor control and function. There is a critical decline in age-related motor performance, which has been attributed to loss of motor neurons (45)

Distinguished from the motor defect called dysarthria, which is imperfect articulation of speech due to disturbances of muscular control. apraxia (syn: dyspraxia )- Difficulty in performing a learned movement or coordinated motor activity even though understanding, motor function coordination, and sensation are intact Synchronous Motor MCQ Questions and Answers Page - 4. 1. The synchronous motor can be started by. A. Providing damper winding in its rotor circuit. B. Coupling it with a dc compound motor. C. Coupling it with a small ac induction motor called the pony motor

Complete sensory or motor function loss below the level of injury. Grade B Sensation is preserved below the level of injury, but motor function is lost. Grade C Motor function below the level of injury is preserved, with more than half of the main muscles receiving a less than 3 grade on the ASIA motor score Inside each canal is a gelatin-like structure called the cupula [KEW-pyew-lah], stretched like a thick sail that blocks off one end of each canal. The cupula sits on a cluster of sensory hair cells. Each hair cell has tiny, thin extensions called stereocilia that protrude into the cupula This portion is the most commonly injured area of the brain, so researchers have been able to determine what certain parts of it do. Damage of a section of the brain called Broca's area, for example, causes aphasia, or the inability to speak. Other injuries affect personality, cause depression, and result in the loss of problem solving skills What is Motor Starter. November 23, 2015. By Administrator. The primary function of a motor starter is to start and stop the motor to which it is connected. These are specially designed electromechanical switches similar to relays. The main difference between a relay and a starter is that a starter contains overload protection for the motor

Temporary Paralysis Nervous System Disorders and

Uncoordinated Movement: Causes, Diagnosis and Test

Alzheimer's is a progressive disease, where dementia symptoms gradually worsen over a number of years. In its early stages, memory loss is mild, but with late-stage Alzheimer's, individuals lose the ability to carry on a conversation and respond to their environment. Alzheimer's is the sixth-leading cause of death in the United States Therapies against motor loss and progression in Parkinson's' disease (PD) may need to tackle the imbalance between two neurotransmitters, dopamine and acetylcholine, instead of focusing on dopamine alone, an early study suggests.. The study, Dopamine Deficiency Reduces Striatal Cholinergic Interneuron Function in Models of Parkinson's Disease, was published in the journal Neuron Motor Function . By innervating the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius, the deep peroneal nerve is responsible for pulling the foot back—the opposite motion of pointing the toes. This motion, which is called dorsiflexion, is important for walking Cognitive impairment: A Call for Action, Now! the number of people living with cognitive impairment in the United States is equal to twice the population of new York City. More than 16 million people in the United States are living with cognitive impairment, 1 but the impact of cognitive impairment at the state level is not well understood

Hemiparesis - Wikipedi

  1. ated from your body
  2. Motor neurone disease (MND) affects the nerves (motor neurones) that communicate between the brain and the muscles that enable us to move, speak, swallow and breathe. In people with MND, the motor neurones gradually degenerate and die, causing the muscles to weaken and waste. MND is a life-limiting disease, and although MND progresses.
  3. The result of this is a reduction of the inhibitory influence that the globus pallidus has over the thalamus, so-called disinhibition of the thalamus, which is equivalent to the excitation of the motor cortex. So the final function of the direct pathway of the basal ganglia is to excite the motor cortex or to increase the motor activity
  4. Motor skills disorder can be extremely disabling both in academic settings (school) as well as in everyday life due to impairment of functioning. Children and adults with this disorder are at risk for obesity, due to the higher rates of physical inactivity, and often suffer from low self-esteem as well as academic underachievement
  5. Gross motor function As a child develops, signs of impaired or delayed gross motor function may be noticeable. The ability to make large, coordinating movements using multiple limbs and muscle groups is considered gross motor function. Gross motor function. Gross motor function may be impaired by abnormal muscle tone, especially hypertonia or.
  6. A motor neuron is a cell of the central nervous system. Motor neurons transmit signals to muscle cells or glands to control their functional output. When these cells are damaged in some way, motor neuron disease can arise. This is characterized by muscle wasting ( atrophy) and loss of motor function. Motor Neuron

Glossary of Movement Disorder Terms Neurolog

Figure 2 Motor Power Factor (as a Function of % Full-Load Amperage) Overloaded motors can overheat and lose efficiency. Many motors are designed with a service factor that allows occasional overloading. Service factor is a multiplier that indicates how much a motor can be overloade Spinal cord injuries can paralyze the limbs. Paralysis of the legs is called paraplegia. Paralysis of the legs and arms is called quadriplegia. Average age at injury is 31.7 years. Males account for about 75% of those with spinal cord injuries. Leading causes of spinal cord injury: motor vehicle accidents: 44%. acts of violence: 24%

The spinal cord does not have to be severed in order for a loss of function to occur. It can be bruised, stretched, or crushed. Since the spinal cord coordinates body movement and sensation, an injured spinal cord loses the ability to send and receive messages from the brain to the body's system that controls sensory, motor, and autonomic. TRIAGE GRID Types of calls Refer to ER Refer to MD Refer to MD will Take message & Notify MD STAT Nurse call ASAP MD will call PATIENT SYMPTOMS: Temperature > 102.0 F X Severe Pain X Minor Trauma X Major Trauma X Reaction to Medication X Ingestion - Possible Poisoning X Vomiting X Chest Pain X Disoriented or Confused X Heavy Bleeding X Wound Separation X Loss of Motor Function Motor neurone disease (MND) causes a progressive weakness of many of the muscles in the body. There are various types of MND. This leaflet is mainly about amyotrophic lateral sclerosis (ALS), which is the most common type of MND Its loss leads to body weakness, fasciculation or twitching of muscle and loss of muscle mass called muscle atrophy. The diseases associated with upper motor neurons are a heterogenous group of disorders in which a degeneration of motor neurons of the cortex and tronco encefalico motor nucleus occurs

Werner Syndrome - Home

Motor Neuron Disease (MND): 7 Types, Causes, Symptoms

Hypothyroidism your body functions slow down, making you gain weight and feel tired all the time. Tetralogy of Fallot. Tetralogy of Fallot is a combination of heart defects causing bluish skin, trouble breathing, and more. Acoustic neuroma. Symptoms of an acoustic neuroma may include hearing loss in one ear, ringing in one ear, vertigo and more The loss of brain function may be reversible, static and stable, or progressive with increasing loss of brain activity over time. Normal brain function Brain cells are linked together with neurons, called axons and dendrites, covered in myelin sheaths Also called the soma, the part of a neuron that contains the nucleus (with DNA) and the organelles, but not the projections such as the axon or dendrites. The loss of muscle function in all or part of the body, usually due to nerve damage. Parasympathetic Branch. A motor action that is consciously planned and executed

CP is the most common motor disability in childhood. Cerebral means having to do with the brain. Palsy means weakness or problems with using the muscles. CP is caused by abnormal brain development or damage to the developing brain that affects a person's ability to control his or her muscles. The symptoms of CP vary from person to person However, motor and spatial functions can be recovered if undamaged neurons are stimulated to create new innervation. This type of innervation develops spontaneously after a brain injury in very. When one phase of a three-phase system is lost, a phase loss occurs. This is also called 'single phasing'. Typically, a phase loss is caused by a blown fuse, thermal overload, broken wire, worn contact or mechanical failure. A phase loss that goes undetected can rapidly result in unsafe conditions, equipment failures, and costly downtime

Brain hypoxia: Symptoms, causes, and recover

SCI is classified according to the person's type of loss of motor and sensory function. The following are the main types of classifications: quadriplegia (quad means four) - involves loss of movement and sensation in all four limbs (arms and legs). It usually occurs as a result of injury at T1 or above Link Between Motor Nerve Damage and Muscle Control. Most people associate neuropathy with symptoms like tingling, numbness, and pain, but that's not quite the whole story. Other symptoms can cause problems with balance, motor control, and other muscular functions. Your nervous system is made of up three types of nerves Commercial Auto - coverage for motor vehicles owned by a business engaged in commerce that protects the insured against financial loss because of legal liability for motor vehicle related injuries, or damage to the property of others caused by accidents arising out of the ownership, maintenance, use, or care-custody & control of a motor vehicle.

Musculoskeletal - StudyBlue

Loss of Hand Dexterity and Coordination - HealthCare Journe

In order to perform fine motor skills, it is important that there is coordination and balance of the skeletal, neurological and muscular function. If there is any disturbance in any of these, then it causes difficulty in performing fine motor skills. Know what can cause difficulty of fine motor skills and how to improve it as well as exercises to improve fine motor skills Hearing Loss. Hearing loss (deafness) may be present at birth or it may manifest later in life. Deafness may be genetic or due to damage from noise. Treatment of deafness depends upon its cause. Sensorineural hearing loss can be caused by conditions affecting the: cochlea, eighth cranial nerve, spinal cord, or brain The loss is usually sensory and motor, which means that both sensation and control are lost. Tetraparesis or quadriparesis, on the other hand, means muscle weakness affecting all four limbs. An impairment in motor or sensory function of the lower extremities is known as Paraplegia. Quadriplegia, or tetraplegia, are defined as paralysis of four. Amyotrophic lateral sclerosis, also called ALS or Lou Gehrig's disease, is a neurodegenerative disorder characterized by a loss of muscle function as a result of nerve deterioration. ALS affects a subset of cells known as motor neurons. These cells connect the muscles to the central nervous system and allow for muscle movement and locomotion A tremor or loss of strength in the hand may be a single event brought on by something as simple as aging or numbness from a temporary lack of blood supply. People who commonly experience hand tremors or who have an inability to grip objects should undergo an evaluation from a physician to make rule out a more serious underlying condition

Post-Stroke Rehabilitation Fact Sheet National Institute

Auto insurance is a contract between you and the insurance company that protects you against financial loss in the event of an accident or theft. In exchange for your paying a premium, the insurance company agrees to pay your losses as outlined in your policy. Auto insurance provides coverage for: Property - such as damage to or theft of your. The slip of the induction motor is at maximum i.e. 1 at standstill (rest position), thus the impedance is at its minimum & it draws a huge amount of current called inrush current. The high inrush current magnetizes the air gap between the rotor & stator that induces an EMF in the rotor winding

How to Improve Fine Motor Skills Affected by Neurologic

The bridge action is very important during two-sided motor skills and certain cognitive functions. However, during one-sided motor skills requiring strong focus from only one side, the corpus. The nerves that extend away from the spine and into your limbs are part of the peripheral nervous system. They send signals to and from the central nervous system, which is made up of your brain and the nerves of the spinal cord . The femoral nerve is a peripheral nerve. It is one of the largest nerves in the human body The grey matter of the cerebellum is involved in balance, motor control, coordination, proprioception, and precision. The grey matter of the spinal cord is involved in muscle movement, sensory functions, and sympathetic activity. The cell bodies of alpha motor neurons present in the anterior grey column control the activity of skeletal muscles


Facial Nerve Damage. The facial nerve is perhaps the most important nerve system when it comes to function. The facial nerve is responsible for all movements of the face. A damaged nerve at the origin in the brainstem leads to paralysis of the entire left or right side of the face. Facial nerve damage from dental malpractice or any other types. Because malfunction in the same part of the signal pathway causes similar symptoms regardless of cause, the many causes of muscle weakness are usually grouped by the location of the cause (see table Some Causes and Features of Muscle Weakness).That is, causes are grouped as those that affect the brain, spinal cord, peripheral nerves, muscles, or connections between nerves and muscles The primary motor cortex is a strip of cortical tissue in the frontal lobe immediately anterior to the central sulcus. It is called the primary motor cortex because it is required for the initiation of purposeful movements, and stimulation of areas of this cortex has the lowest threshold for eliciting a motor response Try to move your forefinger only; you should be able to. Newborns, however, lack fine motor control because their axons are largely unmyelinated at birth. Some degenerative diseases, like multiple sclerosis, cause destruction of myelin. The result is loss of control over movements, or ataxia. Myelin's second function is to speed nerve conduction These findings have important therapeutic implications, suggesting that complex rehabilitative motor training can improve motor performance of children, or even adults, with FAS. Scientists also are looking at the possibility of developing medications that can help alleviate or prevent brain damage, such as that associated with FAS