PHYSICS

Chapter 5. MECHANOBIOLOGY
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Mechanobiology is a branch of biophysics that studies the
effects of external mechanical factors on living organisms and
their ability to respond to these factors (to provide mechanoreception).
5.1. MECHANORECEPTION
Mechanoreceptors are specialized sensory formations which
convert mechanical stimuli into the activity of neural cells. The
mechanoreceptors can respond to different mechanical stimuli
such as tactile sensitivity (response to touch, pressure, and vibration),
vestibuloreception (control of equilibrium), and proprioception
(coordination of the relative positions of various parts
of the body).
5.1.1. Tactile Sensitivity
Vision. The human eye has at most 200,000 cones per square millimeter.
Hawks, who must spot small prey from the sky, possess about five
times as many as humans; they can see details at distance two or three
times farther than humans
There are a number of mechanoreceptors in the skin: free
ending of afferent fibers, Meissner's corpuscles, Pacinian corpuscles,
Merkel's disks, Krause's end-bulbs, and Ruffini corpuscles. Many
vertebrates also use specialized hairs, vibrissae, such as those
around a seal's muzzle or car's whiskers, which heighten the
sense of touch. Vibrissae bend in contact with a solid object.
Usually mechanoreceptors induce a change in the ion permeability
of receptor cell membranes inducing an electrical signal, the
receptor potential, which is transmitted to the brain. An example
of mechanoreceptors is depicted in fig. 5.1.
5.1.2. The Vestibular System
Vestibuloreception is the response to a change in rotary acceleration
and deceleration and the direction of displacement in
space. Such a response is used by humans and other animals to
control their body posture and locomotion. The vestibular system
is located in the inner ear, or labyrinth, and consists of three
semicircular canals located at right angles to each other and
a pair of saclike structures called the utricle and saccule (fig. 5.2).
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