Behavioral Neuroscience
Yawning Behavior
Evolution of Yawning
Sensory Afferents to Yawn
Gating the Yawn
Yawning Regulating Yawn Gating
Efferent Yawn Output
Neuromuscular Production of Yawns
Integration of Yawn Circuitry and Behavior
norepinephrine (NE)
Oxytocin (OT)
Yawning figures
Yawn Circuitry
end     Acronyms/Abbreviations

I. Yawning Behavior
A. a paroxysm of the respiratory cycle 1. sudden attack/expression of inhalation 2. lasts 5-10 s a. duration is not fixed i. appears to be fixed ii. can be modulated voluntarily
B. Standard cascade of movements: 3 distinct phases Cascade of Yawning Behaviors 1. Initiation: opening the mouth widely a. allows for slow, deep inspiration i. almost entirely through the mouth b. accompanied by expansion of the pharynx / larynx & thorax c. & vocal cord abduction 2. Acme Phase a. thorax reaches maximum capacity i. followed by a brief interruption of inspiration b. eyes close i. limb stretching a) yawning + stretching = Pandiculation c. generalized stretching of respiratory tract muscles i. diaphragm, intercostals, face and neck 3. Conclusion: short expiration and relaxation
II. Respiratory Cycle A. Regulated by brain stem chemosensitive area 1. Medulla oblongata and pons 2. Sensitive to D in blood PCO2 or [H+] B. Chemosensory neurons excite respiratory premotor centers 1. Inhalation: Nucleus of solitary tract (NST = Dorsal respiratory group) a. signal begins weakly, increases for 2-3 s b. NST stimulates motor neurons i. phrenic (C3-C5) & intercostal (T1-T11) nerves ii. diaphragm + intercostal muscles iii. Ramp signal steady thoracic volume a) sensory feedback inhibits diaphragm excitation c. elastic recoil expiration 2. Forced Exhalation a. Nucleus ambiguus (Ventral respiratory group) 3. Pontine pneumotaxic & apneustic centers a. rate + coordination of inhalation and exhalation i. stimulate NST C. Yawning caused by a transient sympathetic arousal 1. not deep inhalation

III. Evolution of/Purpose for Yawning
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