Storyboard

The autonomic nervous system (ANS) regulates the body's involuntary functions through two antagonistic branches: sympathetic (adrenergic, activation, 'fight-or-flight') and parasympathetic (cholinergic, rest, 'rest-and-digest'). The balance between the two can be quantified non-invasively through heart rate variability (HRV).

HRV reflects the modulations of the sinoatrial node by the vagus (high frequency, HF, 0.150.4 Hz, linked to breathing: respiratory sinus arrhythmia) and the sympathetic (low frequency, LF, 0.040.15 Hz, linked to the regulation of blood pressure and thermostasis). The RMSSD is the most reproducible index of vagal activity; The LF/HF ratio approximates the sympatho-vagal balance.

The baroreflex is the rapid feedback mechanism of blood pressure: aortic and carotid baroreceptors detect pressure changes modulate vagal and sympathetic tone adjust HR and vascular resistance. Baroreflex sensitivity (BRS) is reduced in hypertension, heart failure, and diabetic autonomic neuropathy.

Galvanic skin response (SCR) reflects cholinergic sympathetic activity on sweat glands: it provides a peripheral measure of emotional and cognitive activation. The exponential model describes the stereotyped shape of each individual response (SCR): the amplitude A_SCR reflects the intensity of the autonomic stimulus.

Clinically, HRV analysis distinguishes states of autonomic dysfunction: in chronic heart failure, sepsis and advanced diabetes, HRV decreases (pathological sympathetic dominance) and predicts mortality. Pupilometry (Longtin-Milton model with delay) evaluates the integrity of the ocular autonomic nervous system and detects lesions of the III cranial nerve, intoxications and states of consciousness.

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ID:(0, 34)