Module 4: Muscle Physiology Flashcards
Identify the different levels of organization of skeletal muscle
Muscle
Muscle fibre
Myofibrils
T/F
Skeletal muscle fibres run the entire length of the muscle
True. woohoo
Muscle fibres run surrounded by what?
Connective tissue
T/F
Muscle fibres (muscle cells) have many nuclei and mitochondria
True! They have lots of both
Muscle fibres are divided into contractile elements called what?
Myofibrils
Describe what a myofibril looks like on the side
Have a pattern of light and dark bands creating its striated pattern
Thick filaments are also known as what?
Myosin
Thin filaments are also known as what?
Actin
List the components of myofibrils
A band
I band
H zone
M line
Z line
The A band is also known as what?
Dark band
What is the A band made up of?
Stacked thick and thin filaments
The border of the A band is defined by what?
The length of the thick filament
T/F
The middle of the A band is darker than the rest. Justify your answer
False! It is lighter.
The thin filaments don’t reach this far from the ends. So there is no overlap of thick/thin to make it look dark
The I band is also known as what?
Light band
What is the I band made up of?
The portion of thin filaments that do not extend into the A band
Describe the H zone
The slightly lighter portion of the A band
What is the H zone composed of?
Only the proteins that hold the thick filaments together in a stack. Contains only the heavy chains of myosin
What is myosin composed of?
2 heavy and 2 light chains
Describe the M line
Proteins that hold the thick filaments together in a stack
The M line runs down what portion of a myofibril?
Down the centre of the H zone
Describe the Z line
The vertical line located in the middle of the I band
The distance from one Z line to the next represents what?
One sarcomere
What is a sarcomere?
The functional unit of skeletal muscle
When the muscles are growing, how do they extend in length?
New sarcomeres are added onto the ends