week 4: skeletal muscle function Flashcards
how is energy derived in the from of ATP, and used to power muscular skeletal contraction
- ATP-PC system
- glycolosis
- oxidative phospholisation
- are used to create ATP - myosin ATPase odizes ATP in the presence of myosin into ADP + Pi (orthophosphate)
- the breakdown of ATP releases free energy to energise myosin-actin cross bridges. thus pulling the actin over the myosin and shortening the muscle
define EC (excitation-contraction) coupling
” the sequence of events in which a nerve impulse (action potential) reaches the mucle membrane and leads to the shortening of a muscle”
what is the NMJ and its role in EC coupling?
- NMJ= where motor nueron and muscle fibre meet
- they do not join, there is a subneueral cleft
- acetyklcholine recpetors are inside the cleft
- activated sodium channels are deeper in cleft
- the motor end plate is a specialesed region of the sacrolemma at which the synapse can occur
- nuerotransmitter is acetylcholine, which exictes contraction
- 2nd is acetylcholase which breack down AcH to stop contraction
describe the sliding filament theory
- fibre is resting because cross bridge is not attacthed to actin
- cross bridge binds to actin (ADP + Pi)
- Pi is released from myosin head casuing a conformational change in myosin
- power stroke causes filaments to slide and ADP is released
- new ATP head binds to myosin head, allowing is to release from actin hydrolised and cross bridge is back to orginal state
- process repeats
how does the sliding filament theory explain the length: tension relationship of skeletal muscle
- length tension relationship: optimal length of a muscle is mid-length
- due to outer ranger/ inner range being harder to produce force
- the SFT helps to explain this because at mid range, the largest amount of cross bridges are able to be formed, thefore allowing more muscle contraction (tension)
what is missing from the SFT?
- what model corrects this
- acccording to the SFT, mucles only contract
- however Energy is stored, transferred and released in oder to move
the Hill 3 component model:
- tries to explain this
- 3 components are:
- PE= parralell elastic fibres
- SE=series elastic fibres (tendons)
- CE= contactile fibres (SFL)
- CE and SE occur in series, and PE is parralell from these in the model
- all generate force
describe how the Stretch shortening cycle also adresses this?
- its process
- preactivation:
- central pattern generators in the primary motor cortex and spinal cord activate tissues in preparation for dynamic loading - eccentric phase (shortening)
- muscle (CE, contractile) continues to develop Force activley
- kinetic energy converts to potential energy (Elastic) within a tendon
- spinal stretch reflexes are initiated - Concentric phase: (stretch)
- high force contaction
- uses stored elastic energy in a tendon
- tendon recoils
relate to 3 component:
it adresses that mucles dont only contract (CE), they stretch after contraction due to the built up elastic energy in tendons (PE) causing a stretch (SE). both stretch and shortening of muscle produce force
describe the force:velocity relationship of skeletal muscle
- how does this link to excerise/prescription
higher velocity = less force
lower velocity of a contraction = more force
- this helps to outline the focus/outcome of an excercise
- if velocity is required in an excercise the force requirement needs to be low
define muscle fibre type?
are the characteristics of different skeletl muscles
- slow oxidative ( type 1)
- fast oxidative (type 2 a)
- fast glycotic (type 2b)
characteristics of type 1
number of mitochondria = high
resistance to fatigue = high
dominaant energy system = aerobic
ATPase activity = low
speed of shortentin (Vmax)= slow
efficiency= high
characteristic of type 2a
number of mitochondria =moderate
resistance to fatigue = moderate
dominaant energy system = combination
ATPase activity = high
speed of shortentin (Vmax)= high
efficiency= moderate
characteristics of 2b
number of mitochondria = low
resistance to fatigue = low
dominaant energy system = anerobic
ATPase activity = highest
speed of shortentin (Vmax)= highest
efficiency= low
