Lecture 2 - Mechanisms of muscle contraction Flashcards
What are the three different types of muscle? [3]
- Smooth muscle
- Cardiac muscle
- Skeletal muscle
List the key features of Smooth muscle.
- Mono-nucleated
- Non-striated
- Involuntary control
List the key features of Cardiac muscle.
- Mono-nucleated
- Striated and branched
- Involuntary control
List the key features of Skeletal muscle.
- Multi-nucleated
- Striated and elongated
- Voluntary control
What is a prime mover?
Main muscle producing most of the force during movement
What is an antagonist?
Muscles that oppose the prime mover
What is an synergist?
Muscles that work with the prime mover
What is a fixator?
Muscles that prevent a bone from moving
What is a flexor?
Muscles that work to close a joint
What is an extensor?
Muscles that work to open a joint
What is abduction?
Motion that pulls a structure away from the midline
What is adduction?
Motion that pulls a structure towrds the midline
What does a muscle contain?
A number of fascicles
What do fascicles contain?
A number of muscle fibres
What are the two bands within myofibrils?
- Dark band: remains constant length
- Light band: change length when muscle lengthens or shortens
What is a sacromere?
Smallest contractile unit in a muscle fibre
How many sacromeres are in a muscle fibre?
~20,000
What are sarcomeres made from? [3]
- Actin filaments
- Myosin filaments
- Stabilisation and regulation proteins
What is the thin filament made form?
- Actin
- Tropomyosin
- Troponin
What is the thick filament made from?
Myosin
True or False? A sarcomere contract they get larger.
- False
- They get shorter
What does the contraction of the sacromeres cause to happen?
The powerstroke
What is the state of the sacromere during rest (step1)?
- Ca2+ conc is low
- Myosin heads are ADP-bound
- Actin binding sites are blocked by troponin
What is the state of the sacromere during activation (step2)?
- Ca2+ release from cisternae
- Ca2+ binds to troponin
- Exposes actin binding sites
- Cross-bridge is formed
What is the state of the sacromere during sliding of filaments (step3)?
- Energy stored in myosin heads is released
- Power stroke
What is the state of the sacromere during nyosin detachment (step4)?
- ATP binds to myosin heads making them detach from binding site
- Actin binding sites are empty and can form another cross bridge
What is the state of the sacromere during reactivation of myosin (step5)?
- Energy release from ATP > ADP reaction is stored in myosin heads
- High Ca2+ = muscle continues to contract
- Low Ca2+ = myosin heads are unable to form cross-bridge
What happens during a low frequency of unintended APs?
Twitching
What happens during a high frequency of unintended APs?
Tetani
What is concentric contraction?
- Force > Load
- Muscle shortens
What is eccentric contraction?
- Force < Load
- Muscle lengthens
