Muscle I Flashcards
What are the 3 types of muscle?
Skeletal, cardiac, and smooth
What is skeletal muscle?
It is used for posture and locomotion. This is the muscle that enables our arms and legs to contract under our conscious control, for voluntary movements.
What is cardiac muscle?
It is responsible for the rhythmic contractions of the heart.
What is smooth muscle?
It causes involuntary contraction in blood vessels, gut, bronchi, and the uterus.
Muscles are connected to bones by […]
Tendons
A single muscle cell is called a […]
Muscle fiber
A bundle of muscle fibers is called a […]
Fascicle
Describe the appearance of muscle fibers.
They are long, thin cells with stripes that are aligned with the cells around it and with many nuclei.
Describe how muscle fibers are generated during development?
They start as small precursor cells called myoblasts that each have one nucleus. The myoblasts fuse together over time to form a multi-nuclear muscle fiber..
Name 2 advantages of having more than one nucleus in a muscle fiber.
- Since the muscle fiber is very long, If there was only one nucleus, the products would have to be exported all over the cell. It is more effective to have many nuclei that can serve their own section of the fiber.
- Muscle fibers are long and make lots of proteins, which are responsible for muscle contraction. The amount of protein a cell can make is limited by how much mRNA is made. One nucleus means two copies of every genes, whereas many nuclei will allow for way more protein synthesis.
Within each muscle fibers are many […]
Myofibrils
What are myofibrils?
They are long, thin fibers that comprise the inside of a muscle fiber. They are the contractile unit of the muscle.
Describe the striations in each myofibril, including the major components.
The light bands are called I-bands and the dark bands are called A-bands. In the center of each I-band is a dark line called the Z-line. At the center of each A-band is the M-line, which is within the H-zone.
What is a sarcomere?
It is a section on the myofibril that goes from one Z-line to the next Z-line. This is the area over which contraction occurs.
Describe the structure of the filaments in each sarcomere.
Each sarcomere contains thick filaments and thin filaments. The thick filaments extend from one end of the A band to the other and the thin filaments extend across the I band and part way into the A band. The areas where they overlap have crossbridges sticking out of the thick filaments.
