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  <head>
    <title>001-02 Control systems, energy failure, and hidden reserve</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Control systems, energy failure, and reserve">
      <outline text="Layered control">
        <outline text="Overlapping loops on different timescales">
          <outline text="Blood pressure: baroreceptors in seconds"/>
          <outline text="Sympathetic tone and hormones over minutes to hours"/>
          <outline text="Renal sodium and water over days"/>
        </outline>
        <outline text="Fast tachycardia, slower renal volume defence"/>
        <outline text="Layering buffers failure of one component"/>
      </outline>
      <outline text="Measured versus regulated quantity">
        <outline text="Baroreceptors sense stretch in selected arteries"/>
        <outline text="Beta cells respond to nutrient metabolism"/>
        <outline text="Brain integrates core and skin temperature"/>
        <outline text="Normal value may hide intense compensation"/>
        <outline text="Abnormal value may be adaptive"/>
        <outline text="Fever is a regulated upward shift">
          <outline text="Body conserves and generates heat, causing chills"/>
        </outline>
        <outline text="Hyperthermia: heat gain exceeds loss, no shift"/>
      </outline>
      <outline text="Gain, delay, and reset">
        <outline text="Low gain leaves residual error"/>
        <outline text="High gain plus delay causes oscillation">
          <outline text="Hormones, gene expression, kidneys are slow"/>
          <outline text="Correction can overshoot"/>
        </outline>
        <outline text="Glucose, carbon dioxide, sodium keep moving"/>
        <outline text="Persistent hypertension blunts baroreceptors"/>
        <outline text="Chronic hypercapnia shifts bicarbonate retention"/>
        <outline text="Adaptation conceals disease">
          <outline text="Abrupt reversal can be harmful"/>
        </outline>
      </outline>
      <outline text="Feed-forward control">
        <outline text="Anticipates demand before variable changes"/>
        <outline text="Exercise: central command and limb input"/>
        <outline text="Food cues start salivation and secretion"/>
        <outline text="Reduces disturbance feedback must correct"/>
        <outline text="Maladaptive when conditioned without need"/>
      </outline>
      <outline text="Energy supply and tissue tolerance">
        <outline text="ATP is not stored; continuously regenerated"/>
        <outline text="Brain: high demand, little fuel reserve"/>
        <outline text="Cardiac muscle depends on aerobic metabolism"/>
        <outline text="Skeletal muscle uses phosphocreatine and glycolysis">
          <outline text="Accepts lactate and lower efficiency"/>
        </outline>
      </outline>
      <outline text="Oxygen delivery and use">
        <outline text="Flow, haemoglobin, saturation, extraction"/>
        <outline text="Anaemia, shock, hypoxaemia, microvascular failure"/>
        <outline text="Mitochondrial toxins block use despite delivery"/>
        <outline text="Separate ventilation through cellular utilisation"/>
      </outline>
      <outline text="Ordered cell injury and reperfusion">
        <outline text="Specialised activity lost before integrity"/>
        <outline text="Ion transport fails, sodium and water enter">
          <outline text="Cells swell"/>
        </outline>
        <outline text="Calcium activates lipases, proteases, nucleases"/>
        <outline text="Reactive oxygen species damage membranes and DNA"/>
        <outline text="Early correction allows recovery"/>
        <outline text="Beyond a threshold, damage self-amplifies">
          <outline text="Injury becomes irreversible"/>
        </outline>
        <outline text="Reperfusion rescues but can add injury">
          <outline text="Speed, temperature, electrolytes shape recovery"/>
        </outline>
      </outline>
      <outline text="Compartments and effective osmoles">
        <outline text="Sodium salts outside, potassium and phosphates inside"/>
        <outline text="Water shifts until osmotic forces equalise"/>
        <outline text="Low plasma sodium usually means excess water"/>
        <outline text="Oedema with low effective arterial volume">
          <outline text="Kidneys sense underfilling and retain"/>
        </outline>
        <outline text="Urea crosses membranes, weak effective osmole"/>
        <outline text="High glucose draws water out, dilutes sodium"/>
        <outline text="Brain adapts to chronic tonicity change">
          <outline text="Rapid correction of hypotonicity damages myelin"/>
          <outline text="Rapid correction of hypertonicity causes oedema"/>
          <outline text="Chronic adaptation narrows safe correction rate"/>
        </outline>
      </outline>
      <outline text="Reserve, compensation, decompensation">
        <outline text="Resting values cannot reveal reserve">
          <outline text="Early cardiac dysfunction: breathless on exertion"/>
          <outline text="Creatinine normal despite lost filtration"/>
        </outline>
        <outline text="Compensation has costs">
          <outline text="Sympathetic drive raises myocardial oxygen demand"/>
          <outline text="Renin-angiotensin-aldosterone worsens congestion"/>
          <outline text="Hyperventilation increases respiratory work"/>
          <outline text="Bone buffering depletes mineral"/>
        </outline>
        <outline text="Decompensation: demand exceeds reserve">
          <outline text="Breathing work, mental state, urine, lactate"/>
          <outline text="Trends precede vital sign collapse"/>
        </outline>
        <outline text="Physiology is a trajectory, not a photograph"/>
      </outline>
      <outline text="Five clinical questions">
        <outline text="Which variable is defended"/>
        <outline text="Which sensors, integrators, effectors"/>
        <outline text="What compensation preserves the value"/>
        <outline text="What cost that compensation imposes"/>
        <outline text="How much reserve remains"/>
      </outline>
    </outline>
  </body>
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