====== Physiologic tremor ======

Physiologic tremor is a [[tremor]] or trembling of a limb or other body part. The usual frequency is about 10 times per second. It occurs in normal individuals, especially when they are stressed by [[anxiety]] or [[fatigue]].

All individuals have a normal physiologic tremor that may become more pronounced in periods of [[stress]] or [[caffeine]] use. Furthermore, agents that affect sympathetic tone may affect tremor adversely by activating beta-adrenergic receptors in skeletal muscle and synchronizing motor unit discharges.

Although the relationship among tremor, [[stress]], and adrenergic modulating agents has been well described, there are few reports of the effect of such factors on procedural tremor or [[dexterity]]. This fact is disconcerting, given that caffeinated beverages are consumed ubiquitously by both physicians and surgeons, and resident physicians in particular, even though these beverages are known to increase physiologic tremor and cause hand “shakiness.” 
((Quintana LM. How to Be a Neurosurgeon with Good Hands. World Neurosurg. 2016
May;89:686-8. doi: 10.1016/j.wneu.2015.11.005. Epub 2015 Dec 1. PubMed PMID:
26608385.
)).