Sleep inertia is a physiological state of impaired cognitive and sensory-motor performance that is present immediately after awakening. It persists during the transition of sleep to wakefulness, where an individual will experience feelings of drowsiness, disorientation and a decline in motor dexterity. Impairment from sleep inertia may take several hours to dissipate. In the majority of cases, morning sleep inertia is experienced for 15 to 30 minutes after waking.Sleep inertia is of concern with decision-making abilities, safety-critical tasks and the ability to operate efficiently soon after awakening. In these situations, it poses an occupational hazard due to the cognitive and motor deficits that may be present. Symptoms
"Grogginess", as defined by a drowsy or disoriented state in which there is a dampening of sensory acuity and mental processing. Impaired motor dexterity and decrease in cognitive ability. These gross impairments may be responsible for the associated increase in reaction time and drop in attentiveness. Deficits in spatial memory
Reports of heightened subjective fatigueThese symptoms are expressed with the greatest intensity immediately after waking, and dissipate following a period of extended wakefulness. The duration of symptoms varies on a conditional basis, with primary expression during the first 15–60 minutes after waking and potentially extending for several hours. Tasks that require more complex cognitive operations will feature greater deficits as compared to a simple motor task; the accuracy of sensory and motor functioning is more impaired by sleep inertia as compared to sheer speed.
The additional speech sounds that the human tongue enables us to produce, particularly [i], allow humans to unconsciously infer the length of the vocal tract of the person who is talking, a critical element in recovering the phonemes that make up a word. Non-mammals
Most tetrapod species possess a larynx, but its structure is typically simpler than that found in mammals. The cartilages surrounding the larynx are apparently a remnant of the original gill arches in fish, and are a common feature, but not all are always present. For example, the thyroid cartilage is found only in mammals. Similarly, only mammals possess a true epiglottis, although a flap of non-cartilagenous mucosa is found in a similar position in many other groups. In modern amphibians, the laryngeal skeleton is considerably reduced; frogs have only the cricoid and arytenoid cartilages, while salamanders possess only the arytenoids.Vocal folds are found only in mammals, and a few lizards. As a result, many reptiles and amphibians are essentially voiceless; frogs use ridges in the trachea to modulate sound, while birds have a separate sound-producing organ, the syrinx. History
The ancient Greek physician Galen first described the larynx, describing it as the "first and supremely most important instrument of the voice". Additional images
See also
Articulatory phonetics
Electrolarynx
Histology of the vocal cords
Origin of speech

References
Notes


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