1. 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?

2. 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).

3. Don’t forget to chunk your notes!

4. 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

5. Smooth Muscle
Figure 9.24

6. Innervation of Smooth Muscle
Figure 9.25

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8. 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

9. Proportion and Organization of Myofilaments in Smooth Muscle
Figure 9.26

10. Don’t forget to chunk your notes!

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

14. 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
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15. 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
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16. 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
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