Chapter 2. Prehension

COMPLl A
DEFORM
Chapter 6 - During Contact 221
Somatic Motor System Autonomic Motor Systen
I muscles )/sweat>
(mechanoreceptors J
to/ lg\
I CONTACT
I
slip slip
too much lubrication dry and smooth
good grip
boundary lubrication
Figure 6.5. The eccrine sweat glands are innervated bv the
autonomic nervous system (sympathetic, but cholinergic fibers).
In the cerebral cortex, lesions in the parietal or premotor areas
lead to excessive sweating or lack of sweating respectively, both
of which cause objects to slip from the hand. Denervation also
leads to lack of sweating in those palmar areas. Healthy sweating
provides boundary lubrication of the palmar surface of the hand,
adhesion, and good grip. With contact, the skin is deformed,
activating mechanoreceptors, and creating heat through friction.
Both of these may lead to secretions by the sweat glands, though
the exact mechanisms and pathways are not well defined.