Ch 4 4.4 Muscle Tissue and Motion

The cells of muscles, myocytes, develop from ________. A. myoblasts B. endoderm C. fibrocytes D. chondrocytes

A. myoblasts

Striations, cylindrical cells, and multiple nuclei are observed in ________. A. skeletal muscle only B. cardiac muscle only C. smooth muscle only D. skeletal and cardiac muscles

A. skeletal muscle only

myocyte

muscle cells

skeletal muscle

usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated

Skeletal muscle is composed of very hard working cells. Which organelles do you expect to find in abundance in skeletal muscle cell? A. nuclei B. striations C. golgi bodies D. mitochondria

D mitochondria

You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at.

The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract. When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony.

Why does skeletal muscle look striated?

Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin.

striation

alignment of parallel actin and myosin filaments which form a banded pattern

cardiac muscle

heart muscle, under involuntary control, composed of striated cells that attach to form fibers, each cell contains a single nucleus, contracts autonomously

smooth muscle

under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber