Month: September 2022

STRUCTURAL UNDERPINNINGS. “Sherwood et al. (2005) found relatively greater volume of facial nerve nuclei in the great apes and humans than in all other Old World primates, suggesting increased differentiation of the facial muscles and greater utilization of the visual channel in social communication.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

NEOCORTICAL IMPACT. “Dobson (2012) showed that neocortex size (the area of the brain that includes regions devoted to social interactions) is a significant predictor of facial nerve nuclei volumes in catarrhines (Old World monkeys and apes).” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

GROUP SIZE. “These studies demonstrate that there is a strong co-evolution between social group size and neurobiological components of facial musculature, at least in the catarrhines. Overall, it appears that as group size increases, primate species have more brain area dedicated to the production of facial displays/expressions.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

MUSCLES CONTRACT. “All skeletal muscle, including mimetic musculature, works by getting shorter, or contracting. Each muscle is made up of smaller units that work together to contract. Muscles consist of packaged units called ‘fascicles’, collections of muscle fibers enveloped by connective tissue. Each muscle fiber (or myofiber) in turn consists of bundles of myofibrils, which are made up of many filaments of contractile proteins. One of those contractile proteins is myosin.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

The first atom of the universe. View in LinkedIn

SLOW-TWITCH MYOSIN. “There are several types of myosin proteins but the most abundant and best understood for mammalian skeletal muscle physiology are type I (slow-twitch) and type II (fast-twitch) myosin. Type I fibers take more time and more energy to contract. As a trade-off, they are slow to fatigue and hold the contraction longer. In humans, these types of fibers tend to dominate in muscles of the limbs (except for the hand) and spine.“ http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

FAST-TWITCH MYOSIN. “Type II fibers consist of a number of isoforms (different sub-types) but overall they are able to contract more quickly than type I fibers and use less energy. As a trade-off, they are quick to become fatigued and cannot hold the contraction as long as type I fibers.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

TYPE II FIBERS. “In humans, these types of fibers tend to dominate in muscles of the face and in the human hand. Furthermore, the potential instantaneous force that each fiber type can generate differs, with slow-twitch myosin fibers generating a lower instantaneous force compared with fast-twitch.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

THE EPHEMERAL SMILE. “The mimetic muscles that control smiling, dominated by quick-to-fatigue type II myosin fibers, typically fire that smile quickly but we tire after just a minute or so of holding that smile for family photos.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn

FATIGUE FACTOR. “It is well established that human mimetic musculature is dominated by fast-twitch myosin fibers. Our facial muscles are able to contract quickly and spontaneously (think of how quickly and automatically we smile at the sight of a familiar friend or a funny joke) but it is difficult to hold that contraction longer than a few seconds before fatigue sets in.” http://onlinelibrary.wiley.com/doi/10.1111/joa.12440/full View in LinkedIn