Energy for Muscle Energy for Muscle ContractionContraction• Must have constant supply of ATP for Must have constant supply of ATP for

contraction to be maintained. contraction to be maintained. • Creatine phosphate (CP) can also be used Creatine phosphate (CP) can also be used

b/c of its high energy bond. b/c of its high energy bond. • Cellular respiration or catabolism of food Cellular respiration or catabolism of food

generates more ATP or CP.generates more ATP or CP. • Some muscle fibers ensure an Some muscle fibers ensure an

uninterrupted supply of glucose by storing uninterrupted supply of glucose by storing it as glycogen.it as glycogen.

Providing Energy for Muscle Providing Energy for Muscle ContractionContraction

•Direct phosphorylation of ADP by Direct phosphorylation of ADP by reaction with creatine phosphatereaction with creatine phosphate

•Energy Source:Energy Source:•Oxygen Use: NoneOxygen Use: None•1 ATP per CP 1 ATP per CP Creatine and Creatine and

ATP are the productsATP are the products•NRG supply lasts 15 secNRG supply lasts 15 sec

CP

Providing Energy for Muscle Providing Energy for Muscle ContractionContraction

• Anaerobic glycolysis and lactic acid formationAnaerobic glycolysis and lactic acid formation– Anaerobic- without oxygenAnaerobic- without oxygen

• 2 ATP2 ATP• Lactic acid accumulation (eventually reconverted to glucose in Lactic acid accumulation (eventually reconverted to glucose in

the liver)the liver)• Heavy breathing helps to restore oxygen debt.Heavy breathing helps to restore oxygen debt.

• Energy source is glucoseEnergy source is glucose• No oxygen is usedNo oxygen is used• 2 ATP per glucose, lactic acid2 ATP per glucose, lactic acid• 30-60 sec. worth of energy30-60 sec. worth of energy

Providing Energy for Providing Energy for Muscle ContractionMuscle Contraction

•Aerobic Respiration/Oxidative Aerobic Respiration/Oxidative PhosphorylationPhosphorylation– Aerobic- with oxygenAerobic- with oxygen

•36-38 ATP36-38 ATP•Myoglobin pigment in muscles holds oxygen Myoglobin pigment in muscles holds oxygen when muscles are at rest (muscles with when muscles are at rest (muscles with much myoglobin are called red fibers; white much myoglobin are called red fibers; white fibers do not have much myoglobin). fibers do not have much myoglobin).

Energy Systems used Energy Systems used during contractionduring contraction

VI. All-or-none PricipleVI. All-or-none Priciple1.1. Muscle cells do not partially contract. Muscle cells do not partially contract.

They either do or they do not. They either do or they do not. 2.2. The minimum level of stimulation The minimum level of stimulation

required to cause a fiber to contract is required to cause a fiber to contract is the the threshold stimulus.threshold stimulus.

Muscle TwitchMuscle TwitchResponse of a muscle to a Response of a muscle to a

single brief thresholdsingle brief threshold1.1. Latent Period: few ms Latent Period: few ms

between stim. & between stim. & contrac. couplingcontrac. coupling

2.2. Contraction: cross-Contraction: cross-bridges active bridges active

3.3. Relaxation: begins Relaxation: begins with Ca2+ moving with Ca2+ moving into SRinto SR

Wave summationWave summation• Muscle responds to the frequency and Muscle responds to the frequency and

strength of simulationstrength of simulation

Muscle ContractionsMuscle Contractions• Isotonic: Moving montractionIsotonic: Moving montraction

Muscle ContractionMuscle Contraction• Isometric: Myofilaments are skidding Isometric: Myofilaments are skidding

instead of sliding and the tension in the instead of sliding and the tension in the muscle keeps muscle keeps increasingincreasing

ExerciseExercise• Endurance: AerobicEndurance: Aerobic

– Stronger, flexible musclesStronger, flexible muscles– Greater resistance to fatigueGreater resistance to fatigue– Increase in blood supply Increase in blood supply – Fibers form more mitochondriaFibers form more mitochondria– Store more oxygenStore more oxygen

ExerciseExercise

• Resistance or Isometric Resistance or Isometric ExerciseExercise– Increased muscle sizeIncreased muscle size– Increase strengthIncrease strength– Enlargement of individual Enlargement of individual

fibersfibers– More mitochondria More mitochondria

Muscle Fatigue and Muscle Fatigue and Oxygen DebtOxygen Debt

• Muscle fatigue: unable to contract Muscle fatigue: unable to contract • May result from oxygen debtMay result from oxygen debt• Oxygen Debt must be paid backOxygen Debt must be paid back• Rapid breathing: continues until the Rapid breathing: continues until the

amount of oxygen needed to get rid of amount of oxygen needed to get rid of the accumulated lactic acid by the accumulated lactic acid by making ATP and creatine reservesmaking ATP and creatine reserves

• Before a skeletal muscle fiber can Before a skeletal muscle fiber can contract, it has to receive an contract, it has to receive an impulse from a nerve cell. impulse from a nerve cell.

• Generally, an artery and at least Generally, an artery and at least one vein accompany each nerve one vein accompany each nerve that penetrates the epimysium of a that penetrates the epimysium of a skeletal muscle. skeletal muscle.

• Branches of the nerve and blood Branches of the nerve and blood vessels follow the connective tissue vessels follow the connective tissue components of the muscle of a components of the muscle of a nerve cell and with one or more nerve cell and with one or more minute blood vessels called minute blood vessels called capillaries.capillaries.