Muscles and Movement
Living things move. Physiology is a moving subject. Even when we are at rest, there are a variety of dynamic movements in our body. Blood is flowing, air is inspired and expired, peristalsis of chewed food and chyme during a meal and in the nephrons, tubu
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Muscles and Movement
Living things move. Physiology is a moving subject. Even when we are at rest, there are a variety of dynamic movements in our body. Blood is flowing, air is inspired and expired, peristalsis of chewed food and chyme during a meal and in the nephrons, tubular/urine flow. These internal flows are achieved mostly by smooth muscle and cardiac muscle function that are regulated by the autonomic nervous system (ANS). Secretory movement of exocrine digestive juices and endocrine secretions are also the result of ANS actions. The somatic nervous system co-ordinates all voluntary, intentional movements. The brain plans, initiates the motor activity and the corresponding muscle groups are stimulated to contract, with concurrent relaxation of the antagonistic muscles. The final activated neurons to the respective muscles are either brain stem or spinal alpha motor neurons that govern skeletal muscles in the head/neck region and the rest of the body respectively. Skeletal muscle movement is uniquely fine tuned by sensory feedback proprioceptive signals from the muscle spindles, tendon and joint receptors. The cardiac and smooth muscles basically just respond to the effector ANS. These skeletal muscle proprioception are transmitted to the cerebellum and other higher, cortical motor centers that are involved in effecting a focused, directed movement that matches the original thought. Writing or typing these words requires the co-ordinated fine motor movements of my digits (digital control by electrical action potentials along specific alpha motor neurons!). The ability to enjoy conversations with friends is possible by the orchestrated movement of our tongue and speech muscles, which in turn are intimately associated with listening and understanding the language of communication.
© Springer Science+Business Media Singapore 2016 H.M. Cheng (ed.), Physiology Question-Based Learning, DOI 10.1007/978-981-10-0877-1_5
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5 Muscles and Movement
How Is the Primary Motor Cortex Involved When You Take a Step over a Drain?
Answer The primary motor cortex is not the initiation site of motor muscle movements. Three major higher motor functional areas of the cortex provide the command instructions to the primary motor cortex namely, the pre-motor cortex, the supplementary motor area and the posterior parietal cortex. Concept Electrical activity have been observed in areas around the primary motor cortex, about 750 ms before activation of the primary motor cortex that controls muscle movements. This electrical discharge has been called readiness potential and is generated at the highest level of a functional hierarchy of neurons that control body movements. The middle hierarchical structures would include the collective area termed sensorimotor cortex, sub-cortical nuclei that includes the basal ganglia and thalamus, the cerebellum and brainstem nuclei. Much of the middle level regulatory neurons in motor control ensure the appropriate postures during movements and achieve focused accurate movements as intend
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