Chapter 5: Communication, psychological wellbeing and safeguarding
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Anatomy and physiology
Verbal communication is a complex process that is dependent on intact language, speech and hearing function (González‐Fernández et al. [109]). The human voice is produced by exhaled air vibrating the vocal cords in the larynx to set up sound waves in the column of air in the pharynx, nose and mouth. Pitch is controlled by the tension on the vocal cords: the tighter they are, the more they vibrate and the higher the pitch.
Although sound originates from the vibration of the vocal cords, other structures (such as the mouth, pharynx, nasal cavity and paranasal sinuses) convert the sound into recognizable speech (Tortora and Derrickson [271]) (Figure 5.1).
Figure 5.1 Movement of the vocal cords.
Source: Reproduced from Tortora and Derrickson ([271]) with permission of John Wiley & Sons.
The ear contains receptors for sound waves and the external, or outer, ear is designed to collect sound waves and direct them inward. As the waves strike the tympanic membrane, it vibrates due to the alternate compression and decompression of the air. This vibration is passed on through the malleus, incus and stapes of the middle ear. As the stapes vibrates, it pushes the oval window. The movement of the oval window sets up waves in the perilymph of the cochlea that ultimately lead to the generation of nerve impulses that travel to the auditory area of the cerebral cortex (Tortora and Derrickson [271]) (Figure 5.2).
Figure 5.2 Events in the stimulation of auditory receptors in the right ear.
Source: Reproduced from Tortora and Derrickson ([271]) with permission of John Wiley & Sons.
The physiological process of communication is, however, more complex than speech and hearing. The central nervous system (CNS) controls relatively automatic behaviours present from birth and volitional control acquired with development. Voice production includes the volitional acts of speech and singing, but it can also be involuntary in response to pain or fright (Ludlow [156]). Lesions within the CNS can result in speech impairment as there may be paralysis of the muscles of articulation. CNS lesions can be congenital (e.g. in Down syndrome) or acquired following a stroke (Mathieson [167]).
The peripheral nervous system (PNS) controls the laryngeal and palatal muscles; therefore, if the PNS is affected, this can also result in voice and speech impairments. The cerebellum plays an important role in processing motor activity; it regulates the speech, force and timings of movements and if it is damaged bilaterally speech can be affected. Speech may then be described as slurred and unco‐ordinated.
