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MEDICAL PHYSIOLOGY RHOADES TANNER - PART 3

Tham khảo tài liệu 'medical physiology rhoades tanner - part 3', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 8 Contractile Properties of Muscle Cells 139 Levels of complexity in the organization of skeletal muscle. The approximate amount of magnification required to visualize each level is shown above each view. ically. The muscle of the uterus on the other hand contracts and relaxes rapidly and powerfully during birth but is normally not very active during most of the rest of a woman s life. The economical use of energy is one of the most important general features of the physiology of smooth muscle. The contraction of smooth muscle is involuntary. Although contraction may occur in response to a nerve stimulus many smooth muscles are also controlled by circulating hormones or contracted under the influence of local hormonal or metabolic influences quite independent of the nervous system. Some indirect voluntary control of smooth muscle may be possible through mental processes such as biofeedback but this ability is rare and is not an important aspect of smooth muscle function. While one of the terms describing smooth muscle visceral implies its location in internal organs much smooth muscle is located elsewhere. The muscles that control the diameter of the pupil of the eye and accommodate the eye for near vision cause body hair to become erect pilomotor muscles and control the diameter of blood vessels are all examples of smooth muscles that are not visceral. Cardiac Muscle Motive Power for Blood Circulation. Cardiac muscle provides the force that moves blood throughout the body and is found only in the heart. It shares with skeletal muscle a striated cell structure but its contractions are involuntary the heartbeat arises from within the cardiac muscle and is not initiated by the nervous system. The nervous system however does participate in regulating the rate and strength of heart muscle contractions. Chapter 10 considers the special properties of cardiac muscle. Muscles Have Specialized Adaptations of Structure and Function All of the above should emphasize .