Muscles: fibres, training, fatigue Flashcards
List the 3 methods of ATP production
Direct phosphorylation
Glycolysis
Oxidative phosphorylation
Which methods of ATP synthesis provides energy the fastest ?
Direct phosphorylation
Which methods of energy production has the shortest and longest supply of energy
Shortest supply: direct phosphorylation
Longest supply: oxidative phosphorylation (good for endurance activities)
Describe direct phosphorylation, where it occurs and how long it provides energy for?
Involves creatine phosphate + ADP to form creatinine and ATP. Creatine is delivered to muscles via the bloodstream.
CreaTININE is a waste product which is carried way by blood tot the kidneys.
It occurs in the cytoplasm and provides energy for 10 seconds.
What factors limit creatine phosphate production?
If creatine is digested and not absorbed into the bloodstream
If creatine is absorbed but does not enter the correct cell
Creatine may not be properly modified to produce creatine phosphate.
Describe glycolysis, where it occurs, conditions it occurs in and how long it provides energy for?
Glycolysis is an anaerobic process whereby glucose is converted into 2 molecules of pyruvate. 2 ATP are used up and 2NADH and 4 ATP are produced. Net gain = 2ATP + 2NADH.
It occurs in the cytoplasm and can provide energy from 30 seconds up to 2 minutes.
Describe oxidative phosphorylation, including rate of energy production, where it occurs, conditions and how long it provides energy for
The most efficient energy production method but requires oxygen. It produces energy slowly but energy can last up to 3 hours.
Involves the:
Kreb’s cycle which occurs in the matrix of mitochondria
Electron Transport Chain: occurs in the inner membrane of the mitochondria.
Describe the process of oxidative phosphorylation, involving the prep step, kerb’s cycle and ETC
Prep step: Each Pyruvate is converted into acetyl co-enzyme A, which produces 2NADH and 2CO2.
Kreb’s cycle: acetyl co-enzyme A combines with oxaloacetate to form citric acid. This produces 1 FADH, 3NADH, 2CO2 and 1 GTP molecule.
ETC: Electron carriers migrate to inner mitochondrial membrane. High energy electrons are released from NADH and FADH and they move along the electron transport chain. Their energy is captured and used pump H+ ions across the inner membrane and into the intermembrane space.
The pumping of ions creates a build up of H+ ions in the intermembrane space. They diffuse back across the membrane through ATP synthase, generating ATP.
The electrons combine with oxygen to produce water.
What are the 3 main types of motor units?
Type 1 (slow) Type 2a (fast fatigue resistant) Type 2b/x (fast fatigue)
What are the types of motor units classified according to?
Speed of contraction and fatigue rate
How do the uses of the type 1 and 2 motor units differ?
Type 1: helps with endurance activities
Type 2: used for quick, short bursts of movement
Describe type 1 (slow) motor units according to: resistance to fatigue, oxidative capacity, contraction speed, colour, cell contents, motor neuron size motor neuron conduction velocity
Highest resistance to fatigue High oxidative capacity Fastest contraction speed Red Many mitochondria = more aerobic capacity Smaller motor neurone Slow motor neuron conduction velocity
Describe type 2a (fast fatigue resistant) motor units according to: oxidative capacity, contraction speed, colour, cell contents, motor neuron size motor neuron conduction velocity
Higher oxidative capacity than 2b Slower contraction speed than type 1 Red in colour More developed sarcoplasmic reticulum so is better at delivering calcium to muscle cells when stimulated. larger motor neurone faster motor neuron conduction velocity
Describe type 2b (fast fatigue) motor units according to: oxidative capacity, contraction speed, colour, cell contents, motor neuron size motor neuron conduction velocity
Low oxidative capacity as they rely on aerobic glycolysis
Slower contraction speed
White - use anaerobic respiration so have low oxygen supply
More developed sarcoplasmic reticulum than type 1
Larger motor neurone size
faster motor neuron conduction velocity
Out of the 3 motor unit types, which one has the highest number of fibres per motor neuron?
Type 2a
What do resistance and endurance training involve?
Resistance: trains the body to exert maximal force for short periods of time
Endurance: training the body to to perform repetitive motions for long periods of time
What effects do resistance and endurance training have on muscle mass and motor units?
Resistance: increases muscle mass, hypertrophy of type 2a ALWAYS but 2b SOMETIMES
Endurance: muscle mass can reduce, hypertrophy of type 1 motor units
define fatigue
Inability to maintain power output and is reversible by rest
Explain the causes of high intensity fatigue
Accumulation K+ ions inside T-tubules: This is caused by the high firing frequency of muscle action potentials. The accumulation leads to T-tubule failure, making them inexcitable and calcium is not released. As a result, there is a failure to generate force at cross bridges and excitation contraction coupling is impaired.
Accumulation of intracellular metabolites (ADP, Pi, H+) inhibits Ca release and re-uptake in SR. This inhibits cross-bridge formation. H+ also competes with calcium for troponin binding. Out of all the metabolites, the inhibition is mainly due to accumulation of Pi.
Explain the causes of endurance fatigue
Central fatigue: there are inputs to the motor cortex from metabolically sensitive nerve endings which detect oxygen and hydrogen concentrations. When the muscle begins to fatigue, the drive to the muscle must also slow down. Therefore, the muscle signals to the brain to reduce the excitability of the motor cortex.
Glycogen depletion: glycogen supplies most of the energy for contraction during endurance training. As glycogen stores decrease, there is the onset of fatigue.
Pi and ADP release: these metabolites inhibit cross bridge formation and calcium release and reuptake into the SR
After glycogens stores are depleted what is used as energy source and how is this made possible?
After glycogen stores are depleted, lipid stores are used as an energy source. Hormone sensitive lipase is needed to break down triglycerides into fatty acids and glycerol.
what are the 2 phases of resistance training and what order do they occur in?
First: Neural
Second: Hypertrophic
Describe the neural phase of resistance training
Increased recruitment of largest motor units and higher maximal firing rates
Describe the hypertrophic phase of resistance training
Increase in muscle size. Starts with development of new contractile filaments added laterally to existing myofibrils. Later there is fibril splitting, where the most enlarged fibrils divide longitudinally and the fibrils become numerous
Better motor unit activation
Less antagonist activation
Improved glycolytic metabolism
