Other animals
Pioneering work on the structure and evolution of the larynx was carried out in the 1920s by the British comparative anatomist Victor Negus, culminating in his monumental work The Mechanism of the Larynx (1929). Negus, however, pointed out that the descent of the larynx reflected the reshaping and descent of the human tongue into the pharynx. This process is not complete until age six to eight years. Some researchers, such as Philip Lieberman, Dennis Klatt, Bart de Boer and Kenneth Stevens using computer-modeling techniques have suggested that the species-specific human tongue allows the vocal tract (the airway above the larynx) to assume the shapes necessary to produce speech sounds that enhance the robustness of human speech. Sounds such as the vowels of the words ⟨see⟩ and ⟨do⟩, [i] and [u] (in phonetic notation), have been shown to be less subject to confusion in classic studies such as the 1950 Peterson and Barney investigation of the possibilities for computerized speech recognition.In contrast, though other species have low larynges, their tongues remain anchored in their mouths and their vocal tracts cannot produce the range of speech sounds of humans. The ability to lower the larynx transiently in some species extends the length of their vocal tract, which as Fitch showed creates the acoustic illusion that they are larger. Research at Haskins Laboratories in the 1960s showed that speech allows humans to achieve a vocal communication rate that exceeds the fusion frequency of the auditory system by fusing sounds together into syllables and words.
Metabolic myopathies are myopathies that result from defects in biochemical metabolism that primarily affect muscle. They are generally genetic defects that interfere with muscles ability to create energy. At the cellular level, metabolic myopathies lack some kind of enzyme that prevent the chemical reactions necessary to create adenosine triphosphate (ATP). This prevents the muscle cells from being able to function properly and disrupts communication between joints and bones. Some people with a metabolic myopathy never develop symptoms due to the bodys ability to produce enough ATP through alternative pathways. In the event more ATP is needed from the affected pathway, the lack of it becomes an issue and symptoms develop. People with a metabolic myopathy often experience symptoms such as progressive muscle weakness, fatigue, pain and cramping after exercise, and considerable breakdown of muscle tissue. The degree of symptoms varies greatly from person to person and is dependent on the severity of enzymatic defect. In extreme cases it can lead to Rhabdomyolysis. Types
Metabolic myopathies are generally caused by an inherited genetic mutation. This mutation has an autosomal recessive inheritance pattern making it fairly rare to inherit, but it can also be caused by a random genetic mutation. Metabolic myopathies are named after the pathway in which the defective enzyme or a lack of enzymes is present. This causes the underproduction of adenosine triphosphate (ATP) and affects the muscles in different parts of the body.