Muscle Physiology Flashcards
What are the three types of muscle?
- Skeletal
- Cardiac
- Smooth
Where is skeletal muscle found and what is it responsible for?
Found in the arms, legs and back
-Responsible for voluntary movement
Where is cardiac muscle found and what is it responsible for?
Found in the heart
- Responsible for involuntary movement the rhythmic contractions of the heart
Where is smooth muscle found and what is it responsible for?
Found in the blood vessels, uterus, gut and other internal organs
-Responsible for involuntary contractions
What is the basis of all voluntary movement/ how does the muscle work?
-The muscle is attached to a tendon
-When the muscle contracts it pulls on the tendon and the tendon pulls across the join which moves our limb
-Muscle is attached to tendons which in turn attach to bone on both sides of a joint. Contraction of skeletal muscle pulls on the tendons resulting in flexion of the joints
What is the skeletal muscle made up of?
It is made up of muscle fibers(cells) that are orientated in the same direc tion and that are packaged together into fascicles surrounded by CT
What is a fascicle?
A bundle of muscle fibers
What are the striations along the muscle fibers?
These are the underlying mechanism that allows the muscle fibers to contract
Why are the striations of the skeletal muscle highly ordered?
Being highly ordered allows the entire muscle to contract at the same time, this means the muscle fibers will have maximal efficiency and force
Do muscle fibers all contract at the same time?
Yes
T/F: The striations of each muscle fibre are aligned in the fascicles?
True
T/F: skeletal muscles are multinucleated?
True
How do muscle fibers become multinucleated?
During embryonic development, the cells that turn into muscle fibers are myoblasts. During development, individual myoblasts fuse together to form one long muscle fiber because each myoblast contains a nucleus the mature muscle fiber is multinucleated
What is the benefit of muscle fibers being multinucleated?
- Muscle fibers don’t need to export mRNA or proteins from the nucleus to rest of the fiber. Instead the nuclei offer multiple sites for transcription/translation and allows mRNA and proteins to be made down the entire length of the muscle fiber
- Muscles use a lot of protein to contract. The more nuclei, the more copies of the gene and the more mRNA and protein the cell has. This enables the muscle fibers to make lots of protein
What are muscle fibers made of?
Myofibrils
Characteristics of the myofibril
- Extend the entire length of the muscle fiber
-When the myofibril contracts it causes the muscle fiber to shorten
-The contractile element inside the muscle
-All myofbril contract at the same time
-Have the striated appearance
Why are muscle fibers striated?
Because the myofibrils are striated
What is the dark band of the myofibril called?
A-band
What is the light band of the myofibril called?
I-band
What is the dark line in the middle of the I band called?
Z-line
What is a sarcomere?
Distance from one Z-line to the next
Describe contraction from sarcomere to muscle fiber?
When sarcomeres get shorter(distance between two Z-lines decreases), this causes the myofibrils to get shorter which then causes the muscle fiber to contract
What is the I-band made up of?
Thin filaments (actin filaments)
What is the A-band made up of?
Thick filaments (myosin filaments)