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Unit 1 > Metabolic Pathways for Aerobic Exercise (9/25c) [Biomedical Sciences 1] > Flashcards

Metabolic Pathways for Aerobic Exercise (9/25c) [Biomedical Sciences 1] Flashcards

1
Q

Muscles as Metabolic Machines

A

Turns chemical energy → mechanical work

Catabolism of fuel → ATP breakdown → force production → movement

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2
Q

Muscle Fibers - Type I (slow oxidative)

A

Capillary density = high

Glycolytic enzymes = low concentration

Oxidative enzymes = high concentration

Mitochondrial content = high

Myoglobin content = high concentration

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3
Q

Muscle Fibers - Type IIa (fast oxidative, intermediate fast twitch)

A

Capillary density = low

Glycolytic enzymes = high concentration

Oxidative enzymes = low concentration

Mitochondrial content = low

Myoglobin content = lower concentration

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4
Q

Muscle Fibers - Type IIx or IIb (fast glycolytic, fast twitch)

A

Capillary density = lowest

Glycolytic enzymes = high concentration

Oxidative enzymes = lowest concentration

Mitochondrial content = lowest

Myoglobin content = lowest concentration

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5
Q

ATP overview

A

ATP = energy currency of the cell

ATP is broken by hydrolysis → converts to ADP, free phosphate combines with energy

ATP + H20 → ADP + Pi + Energy

[ATP] stays at about 8 mM

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6
Q

ATP Sinks in Resting Muscle

A

ATP consumption due to

  • Ion pumps (Na+/K+, Ca2+, SERCA)
  • RNA and protein synthesis
  • fuel storage
  • transport of substances
  • signaling to regulate cell processes

1 mM/kh/min

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7
Q

ATP Sinks in Contracting Muscle

A

ATP consumption due to

  • same ones as resting muscle
  • Myosin ATPase (contraction)

240 mM/kg/min (240 fold increase compared to resting)

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8
Q

Chemical Pathways to Regenerate ATP

A

Phosphocreatine

Anaerobic Glycolysis

Oxidative Phosphorylation

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9
Q

Phosphocreatine

A

ADP + PCr + H+ ← creatine/kinase→ ATP + Cr

Spatial and temporal buffer for ATP

Critical for short term, high power activities and the transition from rest to exercise

Creatine shuttle - creatine kinase located near sites of ATP utilization and regeneration, in various points of the cell (cytoplasm)

Creatine synthesized in the liver and absorbed in the diet

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10
Q

Anaerobic Glycolysis

A

Important in transition from rest to exercise and during heavy exercise (>60% VO2max)

When oxygen is insufficient to support oxidative phosphorylation

Associated with acidosis (accumulated protons→ decline in pH)

Glucose transporter recruited by exercise and insulin

Glycolysis Pathway (in blood vessel → muscle) (cytoplasm)

  • Input: glucose (5 mM), glycogen
  • Output: 2-3 ATP, 2 e-/H+, pyruvate → lactate
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11
Q

Oxidative Phosphorylation (aerobic metabolism)

A

Substrate + O2 → CO2 + H2O + 5 ATP
- Substrate can be lipid, carbohydrate, or protein

Primary means of energy production

Rate is measured by oxygen consumption (VO2)

Occurs in mitochondria

  • Tricarboxylic acid (TCA) cycle
  • Electron transport chain
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12
Q

Oxygen consumption (VO2)

A

Proportional to workload

VO2 max represents maximal aerobic capacity

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13
Q

Electron transport chain (ETC)

A

ETC transfers electrons to O2 from H2O

Energy released used to generate ATP

Oxygen is terminal electron acceptor

Proton gradient

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14
Q

Tricarboxylic acid (TCA) cycle

A

aka Krebs or Citric Acid Cycle

strips electrons from substrate

starts with acetyl-coA and ends with 2 CO2, 1 ATP, and 4 e-

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15
Q

Comparison of Energy Pathways - Phosphocreatine

A

Time to Max Rate = immediate

Max Power = high

Max Capacity = low

O2 Required = no

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16
Q

Comparison of Energy Pathways - Anaerobic Glycolysis

A

Time to Max Rate = 5-10 sec

Max Power = moderate

Max Capacity = moderate

O2 Required = no

17
Q

Comparison of Energy Pathways - Oxidative Phosphorylation

A

Time to Max Rate = 2-3 min

Max Power = low

Max Capacity = high

O2 Required = yes

18
Q

Fuel Sources Available to Power Oxidative Phosphorylation

A

Lipids - huge capacity, high energy source, important at rest

Carbs/Glucose - limited capacity, moderate energy source, important during heavy exercise

Protein - moderate capacity, low energy source, important during disease and starvation

19
Q

Fuel Source - Lipids

A

primary fuel source at rest

Slower than glucose/glycogen pathways, huge capacity (~100,000 total kcal)

130 ATP per molecule of palmitic acid

Triglyceride→ lipolysis → free fatty acids + glycerol → beta oxidation cycle and TCA cycle

Found in highest proportion in old/sedentary, or highly trained athletes

20
Q

Fuel Source - Carbohydrates/Glucose

A

More rapid than other pathways

36 ATP per molecule of glucose

Limited capacity (~500 total kcal from muscle glycogen)
- Because we store less glucose than fat
21
Q

Fuel Source - Protein

A

Moderate capacity (24,000 kcal total)

Minor source of energy during exercise

Can be used in gluconeogenesis

Where protein enters cycle depends on what protein it is

22
Q

As exercise duration increases, ___ exercise prevails over ___

A

aerobic over anaerobic

23
Q

As duration increases, we have a greater reliance on ____

A

lipids

24
Q

As intensity increases, we have a greater reliance on ___

A

carbohydrates (glycogen)

25
Q

Burn more fat at ___ intensity for ___ duration

A

lower intensity, longer duration

26
Q

How does the system adapt to training - Anaerobic

A

Increased aerobic substrates (ATP, PCr, creatine, glycogen)

Increased quantity and activity of key glycolytic enzymes

27
Q

How does the system adapt to training - Aerobic (Metabolic)

A

Increased number of mitochondria

Increased oxidation of fats at rest and submaximal exercise

  • Increased fat mobilizing and metabolizing enzyme
  • Decreased catecholamine release during exercise
  • Preserves glycogen stores to increase endurance

Increased ability to oxidize carbs at max exercise (increased glycogen content)

28
Q

How does the system adapt to training - Aerobic (Cardiovascular)

A

Increased left ventricular volume → increase SV

Decreased HR at rest and submax exercise

Increased peripheral vasodilation capacity

29
Q

How does the system adapt to training - Aerobic (Ventilatory)

A

Increased tidal volume and RR at submax exercise

  • Increased time for oxygen diffusion into blood
  • Decreased energy cost of breathing
30
Q

Aerobic vs Anaerobic

A

Aerobic - moderate intensity, long duration activities

Anaerobic - high intensity, short duration activities

31
Q

Determinants of VO2

A

VO2 = CO * a-VO2diff

CO = cardiac output

a-VO2 diff = (CaO2 - CvO2)

  • CaO2 = arterial blood oxygen content
  • CvO2 = venous blood oxygen content
  • Aka oxygen extraction
32
Q

Exercise - Increased cardiac output (CO)

A

INCREASE SV

  • Positive inotropy via sympathetic stimulation
  • Increased preload due to increased venous return

INCREASE HR

  • Parasympathetic withdrawal (up to ~100 bpm)→ decreased activity of vagus nerve
  • Sympathetic stimulation of SA node (over 100 bpm)→ direct stimulation, circulating catecholamines
33
Q

Exercise - Muscle pumps increase venous return

A

Two muscle pumps: lower extremity (peripheral) and respiratory pumps

Works in deep venous system

Pump augments flow into the thorax during inhalation

34
Q

Exercise - Redistribution of Cardiac Output

A

Decreased visceral blood flow
- Sympathetically mediated vasoconstriction

Increased muscle blood flow
- Locally mediated vasodilation from release of vasodilator metabolites from active muscle, vessel endothelium

35
Q

Exercise - Increased Oxygen Extraction

A

Increased a-VO2 difference due to

  • Increased oxygen consumption in active muscle
  • Shunting of more blood to active muscles
36
Q

Exercise - Blood Pressure

A

BP should increase when doing exercise

Q → increases
ΔP → increases
TPR → decreases

37
Q

Dropped BP during exercise indicates

A

something is wrong, such as ischemia or pump dysfunction

Unit 1 (24 decks)

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