Unit 3.4: Mechanics of Muscle Contraction & Body Movement Flashcards
What is the tension exerted by a muscle during a single twitch influenced by?
The muscle type & sarcomere length at the start of contraction
Which muscle type generates more tension?
Fast twitch fibres
How does sarcomere length affect the amount of tension generated?
Too little overlap = few crossbridges, little force
Too much overlap = actin filaments start to intefere with each other, less force generated
Way too much overlap = thick filaments collide with z-disks, force rapidly decreases
How do we increase the force of a muscle fiber?
By increasing the rate of action potentials that stimulate the fiber
What is tetanus?
State of a muscle when it reaches the maximum force of contraction
What are the 2 types of tetanus?
- Incomplete (unfused) tetanus
- Complete (fused) tetanus
What is incomplete (unfused) tetanus?
Slow stimulation rate -> fibre relaxes slightly between stimuli
What is complete (fused) tetanus?
Fast stimulation rate -> fibre does not have time to relax
What is a motor unit composed of?
A group of muscle fibers and a somatic motor neuron that controls them
How is contraction varied ?
- Changing the type of motor unit that is activated
2. Changing the number of motor units that are active
Which fiber has a low threshold for stimulation?
Slow oxidative fibers
Which will have more muscle fibers per motor unit, those involved in fine movements or course movement?
Course movements
What are the 2 main types of muscle contraction?
Isotonic: creates force and moves a load
Isometric: creates force without movement
How can isometric contraction create force if there is no change in muscle length?
Even though sarcomeres shorten, muscle length stays constant because there are elastic elements stretch ti take up force until fully stretched
