A&P Exam 2 Physiology Flashcards
What is phonation?
Any type of laryngeal sound production in speech. Involves the conversion of potential energy of compressed air into kinetic energy of acoustic vibration.
Source theories: Galen
200 AD. Thought trachea was the central origin of voice and acted like a flute or vibrating column or air.
Source theories: Dodart
- Thought larynx was the origin of voice, and vocal folds changed cavity size like tongue and lips change pitch in whistling.
Source theories: Ferrein
- Vocal folds work like a stringed instrument, with the movement of the string vibrating the air.
Source theories: Helmholtz
- Laryngeal sound source related to puffs of air escaping through glottis. Valving (turning on/off) of airstream produces sound.
What is the neurochronaxic theory?
Says that action potentials from the brain cause the vocalis muscle to twitch on a cycle-by-cycle basis, making the frequency of vocal fold vibration dependent on the rate of neural impulses delivered to the laryngeal musculature.
Why is the neurochronaxic theory wrong?
- Brain can’t send signals fast enough to account for speed of vocal fold vibration
- Muscle fiber orientation doesn’t explain adduction
- Signal to each vocal fold would be mismatched because right and left nerves are different lengths
- Thumping someone’s chest causes phonation without neural imput
- Phonation can be produced by airflow without neural imput (cadaver larynx will phonate)
What is the aerodynamic-myoelastic theory?
Elastic vocal folds are moved back to adducted position by:
- myoelasticity: elastic recoil similar to recoil of lung-thorax unit
- aerodynamic forces: Bernoulli effect
Bernoulli effect
Given a constant volume of flow of air, at a point of constriction there will be a decrease in pressure perpendicular to the flow and an increase in velocity of the flow. The greater the flow, the greater the suction.
How does the Bernoulli effect apply to phonation?
How do the vocal folds blow apart/come together (vertical dimension)?
Both blow apart and come together from inferior to superior (below to above)
3 states of phonation
- Ready: adduct vocal folds in the stream of airflow (vocal attack)
- Go: hold folds in fixed position in airstream and actual vibration results in sustained phonation
- Stop: abduct vocal folds to terminate phonation
Simultaneous vocal attack
Adduction of vocal folds and onset of respiration occur simultaneously (happens when you say “zany”)
Breathy vocal attack
Airflow starts prior to adduction of vocal folds (happens when you say “Harry”).
Glottal attack
Adduction of the vocal folds occurs prior to airflow (happens when you anticipate a cough, but talk instead).
What portion of time is spent in each of the vibratory stages?
- Opening: 50%
- Closing: 37%
- Closed: 13%
What is pitch?
The psychological correlate (what we percieve) of frequency of vocal fold vibration. As frequency increases, pitch increases.
Fundamental Frequency
Frequency of vibration of sustained phonation.
Optimal pitch
Frequency of vocal fold vibration that is most appropriate for an individual, integrating mass, elasticity, and length of vocal folds
- about 1/4 octave above the lowest frequency of vibration
- ~212 Hz in females
- ~132 Hz in males
Habitual pitch
The frequency of vocal fold vibration used during speech (ideally the same as optimal pitch).
Pitch range
From highest to lowest possible frequencies.
How do the vocal folds blow apart/come together (from a superior view)?
- Open: posterior to anterior
- Close: anterior to posterior
Pitch-changing Mechanism: Tension
Involves tightening/relaxation of muscles
- Major adjustments: cricothyroid tilts thyroid down in front and lengthens VFs
- Minor tweaks: thyrovocalis stretches for increased tension
- Increased tension = Increased pitch
Pitch-changing Mechanism: Mass
Spread out mass by stretching/lengthening the vocal folds (using cricothyroid and vocalis)
- Increased mass = decreased pitch
Pitch-changing Mechanism: Subglottal Pressure
Increasing glottal resistance to airflow due to increased tension requires increased airflow
- Higher air pressure = higher pitch
Intensity
The physical measure of pressure ratios
Loudness
The psychological correlate of intensity (how we percieve intensity)
How does sublgottal air pressure influence intensity?
Higher subglottal air pressure = higher intensity
How does medial compression influence intensity?
When VFs are tightly compressed, more energy is required to blow them apart, and when they do, it produces an explosive compression of the air. This leads to a greater amplitude of a cycle of vibration, which we hear as increased intensity.
- Higher medial compression = higher intensity
How are intensity and frequency related physiologically?
They are controlled independently and one can be manipulated without changing the other. However, both depend on the same mechanisms, so it’s difficult to increase intensity without increasing pitch.
Order from lowest to highest (average) fundamental frequency: adult female, adult male, child.
Lowest to highest: adult male, adult female, child
Why does frequency vary with age and gender?
Adults have a larger larynx than children, and vocal folds that are longer or have more mass will vibrate more slowly. Males also tend to have a larger larynx than do females.
Suprasegmental
Above the segmental (phonetic) level. Includes elements of prosody.
Prosody
Varied stress, pitch, intonation, loudness, duration, or rhythm used to indicate meaning.
Cover-Body Theory
Tthe cover of the vocal folds (the mucosal lining) is considered separately from the body (the muscle). Fundamental frequency is determined by the cover independently of the body. For example:
- when the cricothyroid muscle contracts, it stretches both the cover and the body, increasing fundamental frequency
- when the thyrovocalis alone contracts, it tightens the body but releases the cover, increasing effective mass and decreasing fundamental frequency
