Page 383 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

Voice and Speech here are as follows: [a:] as in glass; [i:] as in beat; [u:] as
in food; [œ:] as in French peur; [ɔ:] as in bought; [ø:]
The human voice primarily functions as a as in French peu or in German hören; [y:] as in French
means of communication, the performance of menu or in German trüb; [æ:] as in bad; [!:] as in head.
Consonants are described according to their site
which is based on the human capacity of hear- of articulation as labial (lips, teeth), e.g. P/B/W/F/M;
ing (! p. 363 B). As in wind instruments, the dental (teeth, tongue), e.g. D/T/S/M; lingual (tongue,
body contains a wind space (trachea, bronchi, front of soft palate), e.g. L; guttural (back of tongue
etc.). Air is driven through the space between
Central Nervous System and Senses consists of the throat and oronasal cavities The frequency range of the voice, including
and soft palate), e.g. G/K. Consonants can be also de-
fined according to their manner of articulation, e.g.,
the vocal cords (rima glottidis) into the air
plosives or stop consonants (P/B/T/D/K/G), fricatives
space (passages above the glottis), which sets
(F/V/W/S/Ch) and vibratives (R).
the vocal cords into vibration. The air space
formants, is roughly 40–2000 Hz. Sibilants like
(! A). The range of the human voice is so im-
/s/ and /z/ have higher-frequency fractions. In-
mense because of the large variety of muscles
dividuals suffering from presbyacusis or other
that function to modulate the intensity of the
forms of sensorineural hearing loss are often
airstream (loudness), tension of the vocal
unable to hear sibilants, making it impossible
cords, shape/width of the vocal cords (fun-
for them to distinguish between words like
damental tone) and size/shape of the air space
tal tone, ! C) of the spoken voice is roughly one
Joints and muscles of the larynx function to
octave; that of the singing voice is roughly two
adjust the vocal cords and rima glottidis. A
octaves in untrained singers, and over three
stream of air opens and closes the rima glot-
12 (timbre, formants) of each individual. “bad” and “bass.” The tonal range (fundamen-
octaves in trained singers.
tidis and sets off the rolling movement of the
vocal cords (! B). When a deep tone is pro- Language (see also p. 336). The main com-
duced, the fissure of the glottis remains closed ponents of verbal communication are (a) audi-
longer than it opens (ratio of 5 : 1 at 100 Hz). tory signal processing (! p. 368), (b) central
This ratio drops to 1.4 : 1 in higher tones speech production and (c) execution of motor
(400 Hz). The rima glottis remains open when speech function. The centers for speech com-
whispering or singing falsetto (! C, blue). prehension are mainly located in the posterior
Motor signals originate in the motosensory part of area 22, i.e., Wernicke’s area
cortex (! p. 325 C/B, tongue/throat) and are (! p. 311 E). Lesions of it result in a loss of lan-
conducted via the vagus nerve to the larynx. guage comprehension capacity (sensory
Sensory impulses responsible for voice pro- aphasia). The patient will speak fluently yet
duction and the cough reflex are also con- often incomprehensibly, but does not notice it
ducted by the vagus nerve. Sensory fibers from because of his/her disturbed comprehension
the mucosa and muscle spindles of the larynx capacity. The patient is also unable to under-
(! p. 316) continuously transmit information stand complicated sentences or written words.
on the position and tension of the vocal cords The centers for speech production are mainly
to the CNS. These reflexes and the close con- located in areas 44 and 45, i.e., Broca’s area
nection of the auditory pathway with bulbar (! p. 311 E). It controlls the primary speech
and cortical motor speech centers are impor- centers of the sensorimotor cortex.
tant for fine adjustment of the voice. Lesions of this and other cortical centers (e.g., gyrus
angularis) result in disorders of speech production
Vowels (! D). Although their fundamental frequen- (motor aphasia). The typical patient is either
cies are similar (100–130 Hz), spoken vowels can be completely unable to speak or can only express him-
distinguished by their characteristic overtones (for- self in telegraphic style. Another form of aphasia is
mants). Different formants are produced by modify- characterized by the forgetfulness of words (anomic
ing the shape of oral tract, i.e., mouth and lips (! D). or amnestic aphasia). Lesions of executive motor cen-
The three primary vowels [a:], [i:], [u:] make up the ters (corticobulbar tracts, cerebellum) cause various
vowel triangle; [œ:], [ɔ:], [ø:], [y:], [æ:], and [!] are speech disorders. Auditory feedback is extremely im-
intermediates (! D). portant for speech. When a person goes deaf, speech
370 The phonetic notation used here is that of the In- deteriorates to an appreciable extent. Children born
ternational Phonetic Society. The symbols mentioned deaf do not learn to speak.
Despopoulos, Color Atlas of Physiology © 2003 Thieme
All rights reserved. Usage subject to terms and conditions of license.