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Unformatted text preview: MUSCLES I. GENERAL FUNCTIONS OF MUSCLES The major function of muscle tissue is contraction(the ability to shorten and thus cause movement in the body), and relaxation(the ability to lengthen again and thus be ready to contract again. II. FUNCTIONAL CHARACTERISTICS OF MUSCLE TISSUE A. IRRITABILITY = ability of the muscle cell to respond to a stimulus B. CONTRACTILITY = ability of the muscle or muscle cell to contract or shorten C. EXTENSIBILITY = ability of the muscle to be stretched beyond its normal length D. ELASTICITY = ability of the muscle to resume a normal length after first being stretched out NOTE: Conductivity occurs in heart muscle only; it is the ability to transmit a nerve impulse through the Purkinje fibers from the right atrium to the left atrium and the right and left ventricles. III. SPECIFIC FUNCTIONS OF MUSCLES A. Aids in locomotion = movement of the whole body from one place to another B. Movement of substances within the body 1. Digestive tract a. peristalsis b. churning c. defecation 2. Respiratory tract a. coughing b. sneezing 3. Urinary tract a. peristalsis 4. Reproductive tract a. peristalsis in male and female tracts b. labor in female's uterus at birth 5. Heart and Blood vessels a. systole of heart b. contraction in arterioles increases resistance to blood flow C. Maintenance of erect body posture 1.Action of extensor groups of muscles a. always oppose flexors on front b. keeps body pulled backwards to an upright position D. Body heat production 1.Heat produced through cellular respiration in muscle cells NOTE: Heat is a form of energy but it is not used for energy purposes by cells 2. Location of most of heat production: contracting skeletal muscles IV. TYPES OF MUSCLE TISSUE There are three kinds of muscle tissue. Each is different from the others in its function, location and cell structure among other things. Study the summary table below: MEMBRANE EVENTS OF CONTRACTION I. FACTORS NECESSARY TO HAVE MUSCLE EXCITABILITY A. Cell membrane must be semipermeable B. High extracellular concentration of sodium ions(Na + ) 1. extracellular sodium ions are 10 times greater than intracellular sodium ions. C. High intracellular concentration of potassium ions(K + ) 1. intracellular potassium is 30 times higher than extracellular potassium D. Negative intracellular voltage 1.negatively charged protein ions are prevented from exiting muscle cell; combined with the positively charged potassium ions that slowly leak out of the cell, they provide an overall negative charge to the inside of the cell. MUSCLE CONTRACTION I. MUSCLES CONTRACT ONLY IF STIMULATED A. stimulus provided by nerve impulse received from motor unit Note : Makeup of motor unit = the motor neuron, all of its branches and all the muscle cells that it supplies or innervates NOTE: All components of the motor unit must be intact in order for the muscle to contract....
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- Spring '11