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MEDSCI 205 > Energetics > Flashcards

Energetics Flashcards

1
Q

Homeotherm

A

Regulation of their own temperature

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2
Q

WHY do we maintain body temperature?

A

Keep kinetic energy high and optimum temperature of enzymes

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3
Q

Heat gain mechanisms

A

Conduction
Convection
Metabolism
Radiation

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4
Q

Types Of Heat Loss

A

Conduction
Convection
Evaporation
Radiation

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5
Q

What happens when heat gain exceeds heat loss?

A

Body temperature rises

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6
Q

Rate of heat production is…

A

Proportional to metabolic rate

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7
Q

Heat energy definition

A

Heat is a spontaneous flow of energy from one object to another caused by a difference in temperature between the two objects.

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8
Q

Heat balance equation

A

(metabolism - work) - (heat loss) = storage of heat (Hs)

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9
Q

Storage heat equation

A

Calculating the amount of heat energy which is transferred
H = mc delta T

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10
Q

Specific heat capacity

A

The amount of heat required to raise the temperature of 1kg mass by 1 Kelvin - depends on the composition of the object.

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11
Q

Conduction

A

Heat energy is transferred through a solid, liquid or gas by direct contact

Heat gain or loss is usually by conduction is minimal

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12
Q

Heat transfer is dependent on…

A

Thermal conductivity and the temp difference between the two objects

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13
Q

Convection

A

Transfers heat by fluid movement driven by a temperature gradient

Transfer of heat from skin to fluid warms the fluid, thereby reducing its density, it rises and is replacement by cooler fluid

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14
Q

Evaporation

A

Heat loss through the change of state of a liquid into gas.
Hevap = Kevap A.(P2-P1)

Evaporative heat transfer is dependent on the water vapor pressure gradient between the solution and the environment.

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15
Q

Radiation

A

Transfer of thermal energy by means of electromagnetic waves. It does not require a material medium

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16
Q

Modes of thermoregulation

A

Metabolism
Vasomotor regulation (blood flow)
Sweating
Shivering

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17
Q

Thermal regions (core + shell)

A

Core temp - tightly maintained
Shell or skin -highly variable
Mean body temperature = 0.64Tcore + 0.36shell

Core expands in a hot environment and contracts in a cold environment

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18
Q

Tcore females

A

Fluctuates with the menstrual cycle
Hormone levels, endometrial thickness and ovulation

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19
Q

Where is heat produced (organs)

A

At rest: Primarily at brain, heart, liver and kidneys

During exercise: primarily skeletal muscles

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20
Q

How is heat lost?

A

Overwhelmingly through the skin, via radiation, conduction, convection & evaporation

At normal temp 50-65% of heat is lost by radiation with most of it lost by evaporation

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21
Q

Insulation of the shell methods

A

Qualitative variation (vary the medium)
Fat
Feathers
Fur/Hair

Quantitative variation
(Vary the thickness)
Winter fat
Piloerection (air-trapping)
Variable blood-flow to the skin (vasodilation & vasoconstriction)

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22
Q

Thermoregulatory control feedback system

A

Receptors from the skin and the hypothalamus effects metabolism, vasomotor, sweating and shivering that increases body temperature

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23
Q

Temperature sensors - receptors

A

Warm receptors and cold receptors from these receptors project to the pre-optic hypothalamus

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24
Q

Regulation of heat transfers

A

Peripheral thermoreceptors and core thermoreceptors input signal compared with set point.
Effectors: shivering, vasomotor, sweat which activate/deactivate heat transfer

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25
Q

Effector locations for heat gain/loss

A

Metabolism - brown adipose tissue - mainly in newborns

Vasomotor - blood vessels - vasoconstriction at skin, vasodilation at core = heat retention

Sweat - sweat glands - increased sweat leads to evaporative heat loss in dry environments

Shivering - muscles - increases metabolic heat production

Piloerection - hair follicles - traps a layer of air between skin and hair = insulation

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26
Q

Brown adipose tissue

A

High density of mitochondria for high level of metabolic activity. Situated close to blood vessels so that heat produced by metabolism of fatty acids can be quickly distributed to the rest of the body.

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27
Q

Heat transfer within the body

A

Conduction: Slow
Advection/convection: fast -> blood flow

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28
Q

Heat transfer through vasodilation

A

To remove heat produced by metabolism, convection is the primary node of heat loss

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29
Q

Hyperthermia of exercise

A

Heat gain > heat loss so Tcore increases
The hypothalamic integrator outputs neural output to activate heat loss via skin blood flow and sweating. When heat loss = heat gain storage of heat decreases to zero. But the elevated T core persists as long as exercise is maintained.

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30
Q

Heat stroke

A

Occurs when the thermoregulatory system fails and core temperature increases to 41C or above.

Excessive vasodilation at skin causes drop in blood pressure & decreased brain perfusion - confusion, loss of consciousness

Treatment is to sponge with tepid water.

Only place ice packs over skin where large vessels are near surface

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31
Q

Fever hyperthermia

A

Set point is raised

Caused by cytokines from the immune system crossing the blood-brain barrier which increases Tset

Brain sends neural output to increase heat gain/retention to increase Tcore to new higher Tset.

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32
Q

Mechanical work

A

Muscle contraction
Movement of cells, organelles, appendages

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32
Q

Therapeutic hypothermia

A

Lowering core temp. can protect the brain from reperfusion. Damage post-stroke or cardiac arrest.

Decreased metabolism, ROS, cell death and glutamate

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32
Q

List of energy output processes

A

Mechanical work
Synthetic reactions
Membrane transport
Signal generation and conduction
Heat product
Detoxification and degradation

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33
Q

What are synthetic reactions?

A

Creation of essential functional molecules

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34
Q

Membrane transport

A

Minerals
Organic anions/cations
Amino acids

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35
Q

How is heat produced?

A

Temperature regulation
Inefficient chemical reactions

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36
Q

Detoxification and degradation

A

Urea formation
Conjugation
Oxidation
Reduction

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37
Q

Energy released equation

A

energy released = mc(delta)T

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38
Q

Bomb calorimeters and energy

A

Overestimate energy available for cellulose

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39
Q

Oxidation of glucose

A

Produces 32ATP

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40
Q

Oxidation of Fat (palmitate)

A

Produces 129 ATP

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41
Q

Oxidising fuel

A

Oxidising different fuels yields similar amounts of energy per unit O2 consumed

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42
Q

Glucose metabolism

A

Glucose is split during glycolysis into 2 pyruvate. This enters TCA cycle, NADH produced, ETC produces ATP

43
Q

Fast-twitch muscle ATP production

A

30ATP per glucose

44
Q

Exact number of ATP produced by glucose

A

Initial estimates of 36 or 38 ATP were done at room temperature

45
Q

Metabolic wastes

A

Main waste products are CO2 and NH3. Both are water soluble & carried in the blood. CO2 excreted by diffusion and HCO3- by kidney. NH3 carried to liver as glutamine, converted to urea and excreted.

46
Q

Ammonia toxicity and glutamate dehydrogenase

A

NH3 + a ketoglutarate -> glutamate + H2O by glutamate dehydrogenase.

47
Q

a-ketoglutarate

A

Important for oxidative phosphorylation. Reaction with NH3 means that it is not available for oxidative phosphorylation and can be harmful for the brain.

48
Q

Fick principle

A

Used to measure VO2. Subject breathes using a respiratory valve, inspired gas content known. Expired air analysed for O2 & CO2 content and volume expired is measured.

49
Q

Energy efficiency

A

Efficiency = output / input
Output = demand for energy
Input = source/supply of energy
= power/ VO2

50
Q

Energy consumption in muscle involves: signalling and mechanical. How much ATP is used?

A

30-40% of ATP consumed during isometric contraction fuels Na+ and Ca2+ pumping

51
Q

Different types of work

A

Chemical work: moving a molecule against its concentration
Electrical work: moving a molecule against its electrical gradient
Mechanical work e.g muscle contraction

52
Q

Chemical work

A

Molecules can passively transport across a membrane down their concentration gradient (from high to low)

53
Q

Chemical work equation

A

work = RT lnC1/C2
R is the universal gas constant
T is absolute temperature
C is concentration

54
Q

Electrical work

A

Positively charged particles that are free to move will always tend to shift towards the direction of lower voltages

55
Q

Electrical work equatiion

A

Work elec = zFEm

56
Q

Sarcolemmal ATPase

A

A membrane bound electrogenic enzyme that moves Na+ out of the cell (efflux) and K+ into the cell (influx) against their concentration gradients and electrical gradient (Na+)

57
Q

W total equation

A

RT ln(ci/co) + zFEm

58
Q

Cost of a contraction trigger

A

Ca2+ ions are release from the sarcoplasmic reticulum and bind to the myofilaments to trigger contraction. Ca2+ is then taken back up into the SR by the SRCa2+- ATPase pump.

59
Q

Work total for SERCA

A

Wtotal = RT ln (Csr/ccytoplasm) + zFEsr

60
Q

ATP and cross-bridge relation

A

1 ATP is needed to detach a cross-bridge.

61
Q

First law of thermodynamics

A

Energy can be transferred and transformed, but it cannot be created or destroyed (energy of the universe is constant)

62
Q

Second law of thermodynamics

A

Every every transfer or transformation makes the universe more disordered (every process increases the entropy of the universe)

63
Q

Gibbs free energy equation

A

∆G = ∆H - T∆S

Favourable
∆H < 0
∆S > 0

64
Q

Entropy

A

Quantitative measure of disorder that is proportional to randomness

Energy is stored in molecules which are ordered such as glucose

Energy transfer from glucose breaks down the molecule into smaller parts and creates a more disordered state (increases entropy)

65
Q

Open systems

A

The entropy of a system may decrease, but the entropy of the system plus its surroundings must always increase

66
Q

Anaerobic reactions

A

Alactic (doesn’t produce lactate):
Creatine phosphokinase reaction
Adenylate kinase reaction

Lactic:
Glycolysis and glycogenolysis

67
Q

Aerobic pathway

A

Oxidative phosphorylation

68
Q

Sprinter uses…

A

Alactic anaerobic
Crp, AMP

69
Q

400m uses

A

Lactic anaerobic dominates (glycolysis)

70
Q

Marathon runner

A

Aerobic (oxidation)

71
Q

Creatine phosphokinase reaction

A

CrP + ADP -> Cr + ATP
Catalysed by creatine phosphokinase
CrP acts as a buffer to maintain ATP high

72
Q

Creatine phosphokinase reaction kinetics

A

Extremely rapid
Of small extent

73
Q

Creatine phosphate shuttle

A

Creatine phosphate shuttles chemical energy from mitochondria to various cellular locations of the ATPases to phosphorylate ADP

74
Q

Adenylate Kinase reaction

A

2ADP -> AMP + ATP
catalysed by adenylate kinase
last ditch process used only when ATP is v.low

75
Q

Adenylate kinase reaction degradation products

A

IN the absence of ATP, AMP is deaminated to inosine monophosphate:
AMP -> IMP + NH4+
catalysed by AMP deaminase and the products inhibit muscle contraction

76
Q

Glycolysis/Glycogenolysis yields from splitting

A

Glucose yields 2 ATP and glycogen yields 3 ATP

77
Q

Glycogen

A

Consists of long chains of glucose molecules joined end-to-end with many branches. Up to 6000 glucose residues

Converting G6P to glycogen is that it compacts all the molecules into single large polymers for storage by the cell as large granules of sugar.

78
Q

Glycogen energy

A

Provides fuel for muscle contraction and liver glycogen is converted to glucose that exits liver cells and enters the bloodstream by Cori cycle

79
Q

Consequences of anaerobic energy production (knock on effects)

A

Extensive glycolytic activity leads to decreased cellular pH.

Protons: inhibit Ca2+ release from the sarcoplasmic reticulum and compete with Ca2+ for binding sites on Troponin-C, thereby potentially diminishing contractile force.

80
Q

Lactate production as a function of exercise intensity

A

Lactate begins to accumulate and rise exponentially at 55% VO2 max for an untrained subject

81
Q

Process of oxidative phosphorylation

A

Glycogen, fats & proteins can be broken down & enter the CAC or Kreb’s cycle

slow kinetics
enormous extent

82
Q

Citric acid cycle process

A

Pyruvate enters the mitochondria and is a substrate for the CAC. CAC produces ATP and NADH & FADH2 for the ETC

83
Q

ETC - complexes

A

NADH & FADH2 produced by the CAC is used in the ETC chain at complex 1&2

Transmembrane charge is set up generated ATP at complex V

84
Q

Muscle fatigue definition

A

Defined as a reversible failure to maintain the required or expected power output, leading to reduced muscle performance

Protective strategy to prevent cellular damage

85
Q

Central fatigue

A

CNS command
- reduced excitatory input
- Motor neuron signal decreased by altered input from sensory fibres

86
Q

Peripheral fatigue is caused by

A

Neuro-muscular transmission
Muscle fibre action potential
Excitation-contraction coupling
Depletion of substrates for metabolism
Accumulation of waste-products

87
Q

How is fatigue studied?

A
  1. Trained athlete
  2. Exercising volunteer subject (sedentary vs active)
  3. Experimental animals
  4. Isolated whole muscle
  5. Isolated single fibre (myocyte)
  6. Contractile proteins in a test-tube
88
Q

Tetanus

A

Prolonged contraction of a muscle caused by rapidly repeated stimuli

89
Q

Force time fatigue graph

A

Fatigue occurs at the intersection of maximum force and required output

90
Q

Time taken to fatigue factors

A

Required force
Maximum force
Intrinsic fatigability

91
Q

Fast-twitch fiber

A

Easily fatigued
Decreased Ca2+ and force over time

92
Q

Soleus fibre

A

Fatigue resistant
Ca2+ and force relatively stable, even after 1000 pulses

93
Q

Fatigue in fast twitch fiber

A

Type II easily fatigued
Predominantly anaerobic metabolism
Short bursts of fast contractions (e.g sprinters)

94
Q

Slow-twitch fibre

A

Type I, fatigue-resistant e.g Soleus
Predominantly aerobic metabolism
Rich in capillaries and mitochondria (dark)
Continuous extended contractions over time (e.g marathon runners)

95
Q

Fatigue at cellular level

A

Changes in pH (due to accumulation of waste products)
Accumulation of phosphate
Decrease Gibbs free energy of ATP
Excitation-contraction coupling impairment

96
Q

Effects of decreased pH

A

Decrease in relative force
Competition of H+ with Ca2+ for binding sites on Troponin-C right-shift of the Force-Ca2+ relation = Ca2+ sensitivity of myofilaments
Inhibition of Na-K-ATPase, myosin ATPase, cross-bridge interaction

97
Q

How do you measure the amount of inorganic phosphate?

A

Nuclear magnetic resonance (NMR) imaging used to quantify Pi and PCr. Decreased PCr with and increased Pi with exercise. Coincident with decreased force production

98
Q

Possible actions Pi

A

Direction inhibition of rotation of the actomyosin cross-bridge

Reduce Ca2+ release and increase Ca2+ force activation threshold from SR.

Reduction of Free energy of ATP hydrolysis

99
Q

Gibbs Free energy of ATP

A

∆G = Go + RTln [ADP][Pi]/[ATP]
Energy released by ATP hydrolysis
Depends on concentrations
Usually negative because release of energy

100
Q

∆G required by ATPases

A

∆G required by ATPases is positive b/c they gain energy from ATP

101
Q

Changes in ∆GATP for [CrP]

A

As [CrP] falls, [Pi] rises but [ATP] and [ADP] stay constant

102
Q

What happens at exhaustive exercise?

A

ATP preserved at expense of CrP& Pi
Increased Pi will cause a decrease in ∆GATP
If ∆GATP falls sufficiently then work of ATPases will be compromised
Metabolic end-products may inhibit muscle activation & force development

103
Q

Fatigue effect on excitation-contraction coupling

A

Na+ and K+ ionic gradients not fully restored = impaired membrane excitability

Signal to open Ca2+ channels is impaired

Inhibition of SERCA pump = decreased SR Ca stores

Decreased transient Ca and decrease force

104
Q

Effects of aerobic training: Heart

A

Increased cardiac output, increases O2 delivery to the muscles

105
Q

Effects of aerobic training: Circulation

A

Increased plasma volume, increases stroke volume and thus cardiac output. Increases skin blood flow to optimise thermoregulation

106
Q

Effects of aerobic training: Blood vessels

A

Increased capillary proliferation, increases O2 delivery and diffusion into muscles

107
Q

Effects of aerobic training: Myocytes

A

Increased mitochondria, increases O2 extraction. Enzyme adaptation, optimizes metabolism, increases reliance on fat thus reduced lactate production

MEDSCI 205 (7 decks)

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