Tiêu đề 56. PHYSIOLOGICAL PROPERTIES OF SKELETAL MUSCLE AND THEIR DISORDERS.pdf ✅

PHARMD GURU Page 1 PHYSIOLOGICAL PROPERTIES OF SKELETAL MUSCLE: All muscle cells share several properties: contractility, excitability, extensibility, and elasticity: 1. Contractility is the ability of muscle cells to forcefully shorten. For instance, in order to flex (decrease the angle of a joint) your elbow you need to contract (shorten) the biceps brachii and other elbow flexor muscles in the anterior arm. Notice that in order to extend your elbow, the posterior arm extensor muscles need to contract. Thus, muscles can only pull, never push. 2. Excitability is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone. 3. Extensibility is the ability of a muscle to be stretched. For instance, let's reconsider our elbow flexing motion we discussed earlier. In order to be able to flex the elbow, the elbow extensor muscles must extend in order to allow flexion to occur. Lack of extensibility is known as spasticity. 4. Elasticity is the ability to recoil or bounce back to the muscle's original length after being stretched. DISORDERS: OSTEOPOROSIS: Disease of bones that leads to an increased risk of fracture. In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture deteriorates, and the amount and variety of proteins in bone is altered. The three main mechanisms by which osteoporosis develop are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodeling. PAGET’S DISEASE: Paget’s disease of bone is a chronic disorder that can result in enlarged and misshapen bones. The excessive breakdown and formation of bone tissue causes PHYSIOLOGICAL PROPERTIES OF SKELETAL MUSCLE AND THEIR DISORDERS