Ch 8: Muscles Flashcards
3 types of muscle
cardiac, skeletal, and smooth
a single skeletal muscle cell is known as a ____
muscle fiber
a skeletal muscle consists of:
a number of muscle fibers lying parallel to each other and bundled together by connective tissue
during embryonic development of vertebrates, the huge skeletal-muscle fibers are formed by the fusion of many smaller cells called _______
myoblasts
is skeletal muscle multinucleate?
yes
what are myofibrils?
- part of skeletal muscle fibers
- specialized contractile elements
- cylindrical intracellular organelle
- extend the full length of the muscle fiber
Can muscle fibers with a low percentage of myofibrils generate a high degree of tension? what do they have a high ability to do?
No. But they are generally associated with the ability to turn muscles on and off quickly or to generate prolonged activity.
How are male cicadas able to produce their loud mating song and tail-shaking rattlesnakes move their muscles so fast?
because they have a lower percentage of myofibrils in their muscle fibers.
2 cytoskeletal elements of myofibrils
thick and thin filaments
Thick filaments are special assemblies of the protein ____, while thin filaments are made up primarily of the protein ____.
Thick filaments are special assemblies of the protein MYOSIN, while thin filaments are made up primarily of the protein ACTIN.
dark bands are also known as ______ and light bands are known as _____
dark bands are known as A BANDS and light bands are known as I BANDS
What leads to the striated appearance of a skeletal muscle fiber?
the bands of all the myofibrils lined up parallel to each other
What does an A band consist of?
a stacked set of thick filaments along with the portion of thin filaments that overlap on both ends of the thick filaments.
What defines the outer limits of a given A band?
where thick filaments end
What is the H zone?
The lighter area within the middle of the A band , where the thin filaments do not reach.
What does the I band consist of?
the remaining portion of thin filaments that do not project into the A band.
The visible line in the middle of each I band is called the _________
Z line
The area between two Z lines is known as a _____
sarcomere, which is the functional unit of skeletal muscle (i.e., the smallest component of muscle that is capable of contraction).
What is a functional unit?
the functional unit of any organ is the smallest component that can perform all the functions of that organ.
What is the Z line?
a flat cytoskeletal disc made from a cytoskeletal protein complex that CONNECTS THE THIN FILAMENTS OF TWO ADJOINING SARCOMERES.
T/F. during growth of a vertebrate, the size of the sarcomere increases.
false. A muscle increases in length by adding new sarcomeres.
The system of supporting proteins which hold thick filaments together vertically within each stack is found in the ______
M line
a myosin molecule is a protein consisting of ___ identical subunits, each shaped like a _____
a myosin molecule is a protein consisting of TWO identical subunits, each shaped like a GOLD CLUB WITH TWO HEADS.
Two important myosin sites crucial to the contractile process:
- an actin-binding site
2. an ATPase site