Do now activity #4 Why is calcium important to muscle contraction? Why are neurotransmitters important to muscle contractions? What is the difference between aerobic & resistance exercise? Give an example of each type. Explain what oxygen debt is. When do our bodies go through oxygen debt? How do we get out of this debt?

chapter 9-4: smooth muscle Essential Question: How is smooth muscle unique in comparison to the other types of muscles? chapter 9-4: smooth muscle Learning Targets Identify common joint injuries. Identify the inflammatory and degenerative diseases (including arthritis).

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Smooth Muscle Smooth muscle has similar contractile mechanisms Smooth muscle differs in many ways: Fibers are spindle shaped It lacks connective tissue sheaths Most smooth muscle is organized into sheets It is innervated and lacks neuromuscular junctions

Smooth Muscle Figure 9.24

Innervation of Smooth Muscle Figure 9.25

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Smooth Muscle Differences It has fewer thick filaments It contracts in a twisting way to look like corkscrews The whole sheet contracts in a slow, synchronized way It requires low energy It responds to stretching

Proportion and Organization of Myofilaments in Smooth Muscle Figure 9.26

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Response to Stretch Smooth muscle exhibits a phenomenon called stress-relaxation response in which: Smooth muscle responds to stretch only briefly, and then adapts to its new length The new length, however, retains its ability to contract This enables organs such as the stomach and bladder to temporarily store contents

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Hyperplasia Certain smooth muscles can divide and increase their numbers by undergoing hyperplasia This is shown by estrogen’s effect on the uterus

Hyperplasia At puberty, estrogen stimulates the synthesis of more smooth muscle, causing the uterus to grow to adult size During pregnancy, estrogen stimulates uterine growth to accommodate the increasing size of the growing fetus Do not copy

Developmental Aspects: Male and Female There is a biological basis for greater strength in men than in women Women’s skeletal muscle makes up 36% of their body mass Men’s skeletal muscle makes up 42% of their body mass These differences are due primarily to the male sex hormone testosterone With more muscle mass, men are generally stronger than women Body strength per unit muscle mass, however, is the same in both sexes Do not copy

Developmental Aspects: Age Related With age, connective tissue increases and muscle fibers decrease Muscles become stringier and more sinewy By age 80, 50% of muscle mass is lost (sarcopenia) Regular exercise reverses sarcopenia Aging of the cardiovascular system affects every organ in the body Do not copy