Movement

Bodily movements include skeletal movements and movements of soft tissues and body organs. All movement is brought about by the actions of muscles and may be voluntary, involuntary, or a reflex action. All voluntary skeletal movements are initiated in the part of the cerebrum (main mass of the brain) called the motor cortex. Signals are sent down the spinal cord along nerve fibres, and from there along separate nerve fibres to the appropriate muscles. Control relies on information supplied by sensory nerve receptors, in the muscles and elsewhere, that record the position of the different parts of the body and the amount of contraction in each muscle. This information is integrated in specific regions of the brain (including the cerebellum and basal ganglia) that control the coordination, initiation, and cessation of movement. Skeletal movements can also occur as simple reflexes in response to certain sensory warning signals; the movement is automatic and less controlled, involving far fewer nerve connections. Some body movements do not involve the skeleton. For example, eye and tongue movements are brought about by contractions of muscles that are attached to soft tissues. These movements may be voluntary or reflex. Movements of the internal organs are involuntary; they include the heartbeat and peristalsis.