Muscle Energetics Flashcards
ATP sources
- creatine phosphate CP:
during high demand of ATP, used immediately
dephosphorylation of CP for ADP + Pi –> ATP; reverse vice versa - oxidative phosphorylation : when oxygen is present
- glycolysis : anaerobic
creatine phosphate
rapid, high response
–> large amount of ATP
creatine phosphate + ADP –> creatine + ATP
Reversible
At rest = equilibrium
When a cell’s rate of ATP utilization increase:
- reduction in [ATP]inside the cell falls and
increase in [ADP] = shifts right
Creatine phosphate can provide 4 – 5 times the amount of ATP that would be in the cell at rest
anaerobic glycolysis
run out of CP
–> engage anaerobic glycolysis
Energy sources shift with
- Available substrates
- Available oxygen
Glucose –> glycolysis –> ATP
Requires expression of GLUT 4 for transport into the cell
~ 30 mins = liver source will also run out
“Stitch”
- Pyruvate accumulation –> lactate
oxidative phosphorylation
Fatty Acid–> KREBS–> ATP
requires O2
pyruvate accumulation
–> CoA for Krebs
O2 –> OP = ATP production and replenish of CP within muscle cells
ATP sources:shift based on intensity of exercise
a) light exercise:
CP used immediately, then anarobic and then OP
b) intense exercise
CP used immediately, but anarobic dominates for longer period of time
CP not affected
–> aren’t able to get O2 for OP
Types of Contraction: Isotonic
Concentric
Muscle shortens (e.g. lifting something)
Force generated by muscle is greater than load
Eccentric
Exerting a force while the muscle is lengthening (e.g. placing load back down)
Force is smaller than load
Types of Contraction: Isometric
Muscle stays the same length
e.g. too heavy to live/pushing against a wall
force exerted but no change in length
Types of skeletal muscle
slow twitch oxidative muscle fibres
* smaller diameter
* darker colour due to myoglobulin (carry O2 after AG depletes in muscle cells)
* fatigue resistant
* many mitochondria
fast twitch glycolytic muscle fibres
* larger diameter : more myofibrils present for rapid contraction
* pale colour
* easily fatigued
* few mitochondria
Factors influencing force
Crosssectional area of muscle
Number of sarcomeres in parallel (but NOT in series)
–> more myofibrils in parallel = powerful, greater force, increase diameter
–> larger myofibrils in series = silmutaneous contraction = quick but not strong
Number of active motor units = more MUs can increase force (summation of MUs can create greater force too)
Intracellular Ca2+, oxygen and ATP
Initial muscle length : optimal length more force
Fatigue : lactic acid and decrease force
causes of fatigue
Causes
- Extracellular K+ accumulation
- Muscle acidosis
- Pi accumulation
- Reactive O2 and N species
- Depletion of glycogen during glycolytic
respiration
summation leading to complete tetanus:
summed action potentials to produce greater force than single twitch
==> reaches maximum tension easily
fatigue causes muscle to lose tension despite continuing stimuli
tetanus :
When peak force is generated through summation
reaches maximum binding capacity = start to fatigue and lose muscle tension
how does the body control amount of force with active motor units
different size of cell somas
–> larger cell somas = greater force
passive force components
There are two major components:
- The parallel elastic component (PEC) : stretchy connective tissues that run alongside and wrap around individual muscle fibers within a muscle.
* provided by the muscle membranes, supplies resistance when a muscle is passively stretched.
–> It helps to keep the muscle from stretching too much or too quickly, sort of like a protective layer.
2.The series elastic component (SEC) : to the tendons at the ends of the muscle, which attach the muscle to bones.
* residing in the tendons, acts as a spring to store elastic energy when a tensed muscle is stretched.
–> When the muscle relaxes or is stretched, this stored energy from the SEC helps the muscle to bounce back or return to its original length, kind of like the spring in the toy car propelling it forward.
