Muscular System Flashcards
Describe the morphology of skeletal muscle cell
- extremely long and cylindrical shape
- Nuclei are peripherally located
- Cells are multinucleate
- Striated
Why skeletal muscle fiber is multinucleated?
B/c there’s embryonic mesoderm cells that divide and increase
What is the functional organelle of skeletal muscle fiber?
Myofibrils
What is the smallest functional unit of muscle fiber?
Sarcomeres
Do muscle cells divide? Describe cellular differences that are associated w/ muscular “hypertrophy” vs “atrophy”.
Muscle cells don’t divide
Increase in cell size (hypertrophy) vs decrease in cell size (atrophy)
Describe in detail the 5 major structural components of a sarcomere
- Z disk(c): Boundaries of each sarcomere
- Actin (thin) myofilament: Extend from Z disc towards center of sarcomere
- Myosin (thick) Myofilament: Located in center of sarcomere
- M-Line: Bisects the myosin myofilaments
- Titin: Springlike molecule that resists overstretching
ALL ARE PROTEINS
What is the source of skeletal muscle fibers being striated?
Source of striation is myosin and actin myofilament
What are the three regions of the myofibril?
- I Band
- H Zone
- A Band
What happens in the A band?
More and thicker structures that allows for less light to pass through (More myosin)
What happens in the I band?
Less structure and allows more light to pass through (no myosin)
What happens in the H zone?
Occurs in less structured middle of the A band (no actin)
What structures can be found in the I band?
Z-Disc, Titin, and Actin
What structures can be found in the A band?
Myosin, actin, m line, and titin
What structures can be found in the H zone?
Myosin, M line, and titin.
What happens to the 3 regions during full contraction?
A band doesn’t change in size
H zone disappears
I band gets smaller
Describe conducting system of skeletal muscle to trigger muscle contraction
- Neurotransmitters are released from the ends of somatic motor neurons that stimulate sarcolemma
- Action potential spreads throughout the sarcolemma of muscle cells
- Action potential hits deeper and hits sarcoplasmic reticulum, which triggers it to release calcium inside the cell
- Once calcium is released; actin and myosin are triggered to slide and create contraction of sarcomere
What is rigor mortis?
Stiffness of skeletal muscle after death
What causes rigor mortis, and how muscle relaxes after RM?
Cause: Sarcoplasmic reticulum leaks calcium signaling myofibrils to contract (body stiffens)
Relaxation: As proteins denature, actin and myosin detach then the body relaxes
What is a bundle of muscle fibers called?
Fascicle or fasciculus
What are the 3 connective tissues of skeletal muscles?
- epimysium
- perimysium
- endomysium
What is epimysium?
Fibrous covering of whole muscle
What is perimysium?
Fibrous covering of fascicle