The phonatory muscles are divided into adductors (lateral cricoarytenoid muscles, arytenoid muscles) and tensors (cricothyroid muscles, thyroarytenoid muscles). Intrinsic
The intrinsic laryngeal muscles are responsible for controlling sound production. Cricothyroid muscle lengthen and tense the vocal cords. Posterior cricoarytenoid muscles abduct and externally rotate the arytenoid cartilages, resulting in abducted vocal cords. Lateral cricoarytenoid muscles adduct and internally rotate the arytenoid cartilages, increase medial compression. Transverse arytenoid muscle adduct the arytenoid cartilages, resulting in adducted vocal cords. Oblique arytenoid muscles narrow the laryngeal inlet by constricting the distance between the arytenoid cartilages. Thyroarytenoid muscles narrow the laryngeal inlet, shortening the vocal cords, and lowering voice pitch. The internal thyroarytenoid is the portion of the thyroarytenoid that vibrates to produce sound.Notably the only muscle capable of separating the vocal cords for normal breathing is the posterior cricoarytenoid. If this muscle is incapacitated on both sides, the inability to pull the vocal cords apart (abduct) will cause difficulty breathing. Bilateral injury to the recurrent laryngeal nerve would cause this condition. It is also worth noting that all muscles are innervated by the recurrent laryngeal branch of the vagus except the cricothyroid muscle, which is innervated by the external laryngeal branch of the superior laryngeal nerve (a branch of the vagus). Additionally, intrinsic laryngeal muscles present a constitutive Ca2+-buffering profile that predicts their better ability to handle calcium changes in comparison to other muscles. This profile is in agreement with their function as very fast muscles with a well-developed capacity for prolonged work.
Scoring systems have been derived to assess the likelihood of opiate addiction in chronic pain patients. Prescription opioids are the source of nearly half of misused opioids and the majority of these are initiated for trauma or surgery pain management. Further to this, healthcare practitioners have long been aware that despite the effective use of opioids for managing pain, the empirical evidence that supports the use of opioids long term is minimal. In addition to this, many studies that involved patients with chronic pain have failed to show any sustained improvement in their pain or ability to function with long term opioid use.According to position papers on the treatment of opioid dependence published by the United Nations Office on Drugs and Crime and the World Health Organization, care providers should not treat opioid use disorder as the result of a weak moral character or will but as a medical condition. Some evidence suggests the possibility that opioid use disorders occur due to genetic or other chemical mechanisms which may be difficult to identify or change, such as dysregulation of brain circuitry involving reward and volition. However, the exact mechanisms involved are unclear, leading to debate regarding the influence of biology and free will. Mechanism
Addiction
Addiction is a brain disorder characterized by compulsive drug use despite adverse consequences.