Summary

In this lesson, you explored the following essential questions:

• How are the roles of cardiac, smooth, and striated muscles different?

• How do specialized structures in muscles cause muscle contraction?

• What is the relationship between energy use by muscle cells and heat production?

There are three types of muscles (skeletal, smooth, cardiac) with specific characteristics. Smooth muscle functions in the digestive tract and blood vessels to push substances along a tract. Skeletal muscle functions to enable most voluntary movement. Cardiac muscle powers the beating heart. All muscles contract according to the sliding filament model of actin and myosin interaction.

With the muscular system playing such a broad role in relation to the other body systems, many sources for ATP are present in the event that aerobic cellular respiration can no longer proceed.  As the high energy phosphate bonds in ATP are broken to release energy for muscle contractions, heat is also released as a by-product.

Glossary

actin: a thin myofilament consisting of two strands of actin protein molecules wrapped around each other; works with myosin to produce muscle contractions

constrict: to make smaller or narrower, especially at one place, by squeezing; blood vessels will constrict to reduce blood flow

dilate: to make wider or larger; cause to expand or swell; stretch; blood vessels will dilate to increase blood flow

muscle fibre: a single muscle cell

myosin: a thick myofilament consisting of two strands of myosin molecules wound around each other; one end consists of a long rod, while the other end consists of a double-headed globular region; works with actin to produce muscle contractions.

non-striated muscle: contains contractile proteins arranged randomly and do not create bands or stripes; called smooth muscle

striated muscle: marked with stripes or bands that are the result of highly organized arrangements of contractile proteins within muscles