Muscles 1 Flashcards
3 types of muscle?
- Skeletal
- Cardiac
- Smooth
2 examples of skeletal muscle?
- Voluntary muscles
- Diaphragm
2 examples of places in the body you would find smooth muscle?
- Blood vessels
- Sphincters
- Airways
Another name for a skeletal muscle cell?
Muscle fibre
What are skeletal muscle cells formed from in utero?
Myoblasts
How do you identify skeletal muscle in histology?
- Striated
- Multinucleate
- Nuclei pushed to edges of the cell
Are skeletal muscles able to repair?
Not well at all
Myoblasts do not replace damaged muscle
What 2 ways can skeletal muscle try to repair itself?
- Satellite cells replace damaged ones to form new muscle fibres
- Surrounding muscle fibres undergo hypertrophy
How does smooth muscle repair?
Can divide very easily
What encircles muscle fibres?
Areolar connective tissue
How are muscles attached to bone?
Tendons
How does blood reach the muscle in the centre of the muscle?
Deep penetrating vessels
What is the Z line
Border between one repeating unit (sarcomere) and another
What does titin ensure?
Myosin is always surrounded by actin on six sides
How is myosin energised to allow quick on demand contraction?
ATP constantly hydrolysed to ADP and Pi on the myosin head
What proteins are attached to actin?
Troponin
Tropomyosin
What does tropomyosin do?
Blocks myosin binding sites
What does troponin do?
Holds tropomyosin in place
How does calcium reveal myosin binding sites?
- Binds to troponin
- Troponin twists and moves the tropomyosin
Where is calcium stored in the muscle fibre
Sarcoplasmic reticulum
Role of transverse tubes in muscle?
Propegating electrical signals into muscle core
What do transverse tubes allow the muscle to do?
Uniform contraction
What is the combination of a nerve and a muscle called?
Motor unit
If a motor unit is damaged why don’t you lose the function of the muscle?
There are multiple motor units for a single muscle
What is tension?
Force exerted by a muscle
What is load
Force exerted on the muscle
What is harder as the load increases?
- Fast contraction
- Generation of the required tension
What is isometric contraction
Contraction without shortening of the fibre
What is isotonic contraction?
Contraction with shortening of the fibre
What is lengthening contraction?
Contraction with lengthening of the fibre
What is a twitch response?
A contraction produced by a single action potential
How much longer is twitch than an AP?
About 100 times longer
What does the fact that twitch is so much longer allow?
Contraction to be sustained for longer
If the time between AP’s is short what happens with the contractions?
They summate
What is tetanus with regards to muscle?
A sustained level of tension in any muscle fibre
What is unfused tetanus?
Contraction fluctuates over a period of time
What is fused tetanus?
Contraction is sustained over a long period of time
Why do we fatigue?
Stops fused tetanus from happening constantly and means that calcium levels aren’t constantly high in the cell
What is the length tension relationship
The optimum length of a muscle fibre that produces the strongest contraction
What does the agonist/antagonist relationship of skeletal muscles allow?
Increased manoeuvrability
