Muscles Flashcards
What is tension
The force that a muscle exerts on the joint when it is contracting is called the tension of the muscle
What is load
The force that is exerted on a muscle by an object is called the load of the muscle
What happens if tension does not exceed load
The muscle will either remain at the same length or it will lengthen
What are the types of muscular contraction
Shortening (concentric) contraction
Isometric contraction
Lengthening (eccentric) contraction
What is the mechanical response of a muscle fibre to a single action potential
A twitch
What is the latent period
Comes after the action potential before the tension in the muscle fibre begins to increase
What is the contraction time
The time interval from the beginning of tension development (at the end of the latent period) to the peak tension
A shortening (concentric) contraction, an increasing load causes…
- the latent period to increase
- the velocity of shortening to slow down
- the total duration of the twitch to become shorter
- the distance shortened to become less
What happens when load increases to the point where the muscle is not abele to move it
The contraction becomes isometric
What happens when load increases beyond the peak tension that a muscle can produce
The contraction becomes lengthening (eccentric)
What is summation
The increase of muscle tension from successive action potentials
What is temporal summation
When twitch doesn’t have the time to go back to normal state
What is tetanus
When successive stimulations result in a sustained contraction
What is unfused tetanus
When the muscle fibre has time to partially relax before the next stimulation
The development of tension oscillates
What is fused tetanus
When the muscle fibre has no time to relax between stimulations
The development of tension is continuous and smooth
Muscle fibre types
IIx - fast-twitch, fast-glycolytic fibres
IIa - intermediate fibres, fast-oxidative glycolytic fibres
I - slow-twitch, slow-oxidative fibres
What does muscle contraction speed depend on
The rate of cross bridge cycling, which depends on the myosin heavy chain isoform
Mechanisms involved in muscle fatigue
- Conduction failure
- Lactic acid build up
- Inhibition of cross-bridge cycling
- Fuel substrates
- Central command fatigue
What does a motor unit do
Provides interaction between nervous system and muscles
What does an action potential do
Propagates over muscle fibres to case contraction
What is excitation-contraction coupling
The sequence of events by which an action potential in the plasma membrane activate the force-generating mechanisms
How long does an action potential last in a skeletal muscle fibre
1 to 2 ms
What is going on in a relaxed muscle
Low ca2+
Cross bridge cannot bind with actin as tropomyosin is covering the binding site
What is happening in an active muscle
High ca2+
Ca2+ binds to troponin -> tropomyosin moves away from cross-bridge binding site -> actin binds to cross bridge
What proteins are responsible for linking the membrane action potential with calcium release in the cell
Dihyropyridine (DHP) receptor
Ryanodine receptor
What is ATPase
An enzyme which determines the speed of ATP hydrolysis and resulting sarcomere shortening velocity
What are the molecular changes for endurance phenotype characterised by
- increased mitochondrial mass
- increased oxidative enzymes
- decreased glycolytic enzymes
- increased slow contractile and regulatory proteins
- decrease in fast-fibre area
Molecular changes to high resistance training
- increases in wet mass
- increase in fibre cross-sectional area
- increase in protein content
- increase in RNA content
What is hypertrophy
Increase in muscle fibre size due to the addition of contractile proteins in the muscle cell
What does muscular hypertrophy depend on
Initial strength
Duration of the training programme
Training technique
What are the components of resistance training
- time under tension
- volume
- velocity
- exercise order
- recovery between sets
- frequency
- exercise type
What is hyperplasia
Increase in the number of muscle fibres
Role of creating phosphate
Provides energy very fast to form ATP from ADP but only lasts 1-2 sec
What is glycolysis
Energy from glucose in the absence of oxygen
What is oxidative phosphorylation
Energy from glucose or fat in the presence of oxygen
