Muscle Flashcards
What are the 3 types of muscle?
Skeletal, cardiac and smooth muscles
What is skeletal muscle?
Muscles used for posture and voluntary movements
What is cardiac muscle?
Muscles responsible for rhythmic contractions of the heart
What is smooth muscle?
Muscles that cause involuntary contractions
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 many nuclei
Describe how muscle fibers are generated during development?
They result from the fusion of many small precursors called myoblasts. Each myoblast contributes a nuclei explaining why the fibers are multinucleated
Name 2 advantages of having more than one nucleus in a muscle fiber.
- Since the muscle fibre 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 fibre section.
- Muscle fibres 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 gene, whereas many nuclei will allow for way more protein synthesis.
Within each muscle fibres are many […]
Myofirbils
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 centre of each I-band is a dark line called the Z-line. At the centre 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.
In the I-band, are there thick filaments or thin filaments or both?
Thin filament
In the H-zone, are there thick filaments or thin filaments or both?
Thick filaments
In the A-band, are there thick filaments or thin filaments or both?
Both
What are thin filaments made of?
Actin
Describe the structure of each actin filament.
Each actin filament is formed from two chains of globular actin subunits, twisted into a helix
What are thick filaments made of?
Myosin
Describe the structure of each myosin fiber and filament.
A myosin protein has a long fibre with an double-head end that form the crossbrideges. The filament is made from many myosin proteins together.
In a given sarcomere, how many thick and thin filaments are there?
There are about 6 thin filaments for each think filament or 3 thick filaments for each thin filament
Explain the sliding filament model.
it is the process by which muscles contract. The Z-lines are pulled closer together when the head groups of the thick filaments attach to the thin filaments and pull them OVER themselves.