Autonomic Nervous System—part of the nervous system that coordinates control of organs throughout the body according to the safety or danger an animal is experiencing. Consists of the sympathetic and parasympathetic branches. Sometimes abbreviated ANS.
Calming Response—behavioral and physiological responses associated with an evolutionarily newer branch of the parasympathetic nervous system in mammals, termed the “Social Engagement System” by Porges (see Porges, The Polyvagal Theory). Coordinates heart, breath, and social communication circuits with the perception of safety. It arises in the Nucleus Ambiguus, and sends and receives signals through the ventral, myelinated branch of the Vagus nerve.
Fight-or-Flight Response—a term commonly used to refer to the behavioral and physiological responses of the sympathetic branch of the autonomic nervous system. Termed the “Mobilization Response” by Porges (see Porges, The Polyvagal Theory).
Heart Rate Variability—fluctuations in heart rate associated with activity of the parasympathetic system; Often abbreviated HRV. Some but not all heart rate variability is caused by respiratory sinus arrhythmia (Lewis et al., “Statistical Strategies”).
Noradrenaline—the chemical signal (neurotransmitter) used by nerves that transmit signals directly to organs and tissues as part of the response to challenge or threat. Works in conjunction with adrenaline. The nerves that communicate with noradrenaline are part of the sympathetic branch of the autonomic nervous system.
Nucleus Ambiguus (NA)—an evolutionarily recent brainstem nucleus found in mammals that is central to the Calming Response component of the parasympathetic nervous system. Named thus because its anatomical borders are not easy to see. Sends and receives signals through the mammalian (ventral, myelinated) branch of the vagus nerve.
Parasympathetic nervous system—branch of the autonomic nervous system classically associated with baseline health functions such as nutrition and reproduction; often called the “Rest-and-Digest” or “Feed-and-Breed” system. Sends and receives signals through the vagus nerve.
Polyvagal theory—the theory that the parasympathetic system in mammals is divided into two fundamentally different branches: an evolutionarily older branch (dorsal, unmyelinated) involved in freeze/immobilization behavior (not discussed in this article), and a distinctly mammalian branch (ventral, myelinated) involved in social communication and calm behavioral states (see Calming Response). This theory is supported by evidence in anatomy, phylogeny, embryology, physiology, and behavior (Porges, The Polyvagal Theory).
Prosody—a quality of speech intonation exhibited by healthy people in safe environments. Characterized by varying pitch, varying loudness, flowing timing, and resonant vocal tone; important for communicating emotional information. Highly prosodic speech described as lilting or song-like. Un-prosodic speech sounds flat, monotone, and emotionless.
Respiratory Sinus Arrhythmia—the regulation of the heart rate by the breath; heart rate increases during inhalation and decreases during exhalation, due to the respiratory rhythm of the neurons in the Nucleus Ambiguus, the brainstem center that controls the Calming Response.
Rest-and-Digest Response—a term commonly used to refer to the behavioral and physiological responses of the Parasympathetic nervous system. Also called “Feed-and-Breed” response.
Sympathetic nervous system—the branch of the autonomic nervous system associated with Fight-or-Flight responses. Uses the hormone Adrenaline and the neurotransmitter Noradrenaline.
Vagal—pertaining to the Vagus nerve.
Vagal Tone—overall activity of the Vagus nerve. Typically estimated from observed Heart Rate Variability.
Vagus nerve—the nerve responsible for carrying the majority of parasympathetic signals to and from tissues and organs. According to Polyvagal Theory there are two branches with distinct functions (See Polyvagal Theory).