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Questions and Answers
Which of the following is NOT one of the 4 ways to perform reference frame calibration according to the text?
What is the relationship between muscle size (mass) and muscle force?
What is the main role of muscle cells according to the text?
What is the transformation matrix notation described in the text?
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What is one of the general aspects of the muscle organ besides being a motor/actuator for mobility?
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What does the text state is the 'driving force' behind cell motility (spontaneous cell movement)?
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What is the hierarchy in form and function of muscles?
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What does the text state about the effect of training and increased usage on muscles?
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Which of the following is NOT listed as a general aspect of the muscle organ in the text?
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What is the relationship between body development, age, and muscle form and function?
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Study Notes
Muscle Models
- Muscle parameters include area, length, dynamic parameters, and pennation angle.
- Hill's equation: (Force+a)*(speed+b) = b(Isometric tetanic force+a) describes muscle dynamics.
Force-Velocity Relationship vs Force-Length Relationship
- Muscle models can be classified into two types: Hill type model and Huxley's Cross-Bridge Model.
- Hill type model:
- Sarcomere (CE) force is in series and in parallel with elastic structures (fascia's, PE and SE) depending on tendon length.
- Critical notes:
- Large number of unknown parameters for each muscle.
- Negative stiffness in F-L characteristic.
- Assumes F-L and F-v characteristics are independent.
- Parameters are assumed constant, no history dependence.
- Short Range Stiffness does not emerge!
- No link to microscopic mechanisms.
- Huxley's Cross-Bridge Model:
- Attachment and detachment rate functions f and g describe probabilities → fraction of attached cross-bridges n(x,t) per length x.
- Includes Short Range Stiffness and historical dependence.
- Explains F-V curve and predicts ATP consumption from CB detachment.
Optimization of Muscle Forces
- More muscles present than Degrees of Freedom (600 -200), resulting in many combinations of muscle force producing the same joint moment.
- Muscle fiber dynamics are modeled as their moment arms around the joints, cross-area, and pennation angles.
Muscle Morphology and Physiology
- Skeletal muscles:
- Each muscle is an organ.
- Each fiber has its own nuclei.
- Adaptation to load.
- Cell Regeneration.
- Striated Microscopic pattern.
- Voluntary / Involuntary controlled.
- Attaches to bone, fascia, and skin.
- ~40% of body mass.
- Force build-up:
- First type I, then type II.
- Force increases with number of motor units and frequency of stimulation.
- Force buildup evolves in three distinct phases:
- Excitation: Action potential from nerve system along muscle fiber.
- Activation: Fast release of Ca2+ (20ms) from voltage difference.
- Contraction: Action-Myosin interaction by means of the Cross-Bridge Cycle.
- Sarcomere Force-Length relationship:
- Constant length = isometric.
- Sarcomeres have a minimal length from which force increases quickly to the maximum, where there is a total overlap of actin and Myosin, after which the force will decrease until 0 where no overlap is anymore.
Muscle Form & Function
- Constraints on muscles:
- Mobility and size → muscle force (m2) vs mass (m3).
- Body development and age form a constraint.
- Training and more usage will give better blood circulation and muscle growth.
- General Aspects of the muscle organ:
- Motor/actuator for mobility.
- Circulation of the blood, lymph, or digestion.
- Heating of the body (mechanical).
- Protein buffer to protect vital organs.
- Blood sugar homeostasis.
- Cell motility (spontaneous movement of a cell from one location to another by consumption of energy) is the driving force.
- Same proteins are involved in non-muscles as in muscle cells.
- Hierarchy in form and function:
- Myosin: Molecular motor which is the ‘grabbing’ head in a Cross-Bridge with actin.
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Description
Test your knowledge on muscle models, including the Hill type model which describes sarcomere force in series and parallel. Topics covered include muscle dynamics, force-velocity relationship, force-length relationship, and Hills equation. Get ready to dive into the complexities of muscle parameters and models!
