3.1 Intrinsic Regulation of Heart Pumping

• What is the Frank-Starling mechanism related to?

  Intrinsic regulation of heart pumping
• What primarily determines the amount of blood pumped by the heart each minute?

  The rate of venous return
• How does peripheral tissue control blood flow?

  By regulating local blood flow
• Where does blood return from the peripheral tissues?

  To the right atrium
• What happens to the blood that returns to the heart?

  The heart pumps it into the arteries
• Who are the Frank-Starling mechanism named after?

  Otto Frank and Ernest Starling
• What does the Frank-Starling mechanism state about heart muscle stretching?

  Greater stretching leads to greater contraction force
• What is the physiological limit of the heart related to the Frank-Starling mechanism?

  The heart pumps all returning blood
• What happens when extra blood flows into the ventricles?

  The cardiac muscle stretches to a greater length
• How does stretching the cardiac muscle affect actin and myosin filaments?

  They achieve a more optimal overlap for force generation
• What is characteristic of all striated muscle regarding stretching?

  They contract with increased work output when stretched
• What effect does stretching the right atrial wall have on heart rate?

  It increases heart rate by 10 to 20 percent
• How does the contribution of right atrial wall stretch compare to the Frank-Starling mechanism?

  It is much less than the Frank-Starling mechanism
• What are the types of ventricular function curves?

  • Stroke work output curve
  • Ventricular volume output curve
• What happens to stroke work output as atrial pressure increases?

  It increases until the ventricle's limit
• What is the limit of the ventricle's pumping ability related to?

  Atrial pressure for each side of the heart
• What does the ventricular volume output curve represent?

  The functional ability of the ventricles to pump blood
• What ions have a marked effect on membrane potentials?

  Potassium and calcium ions
• What role do calcium ions play in heart function?

  They activate the muscle contractile process
• What happens to the heart with excess potassium in extracellular fluids?

  The heart becomes dilated and flaccid
• What can large quantities of potassium block?

  Conduction of the cardiac impulse
• What potassium concentration can cause severe heart issues?

  8 to 12 mEq/L
• How does high potassium concentration affect resting membrane potential?

  It decreases the resting membrane potential
• What effect does decreased membrane potential have on heart contraction?

  It makes contraction progressively weaker
• What effect do excess calcium ions have on the heart?

  They cause spastic contraction of the heart
• What happens with a deficiency of calcium ions?

  It causes cardiac weakness
• How are calcium ion levels in the blood normally regulated?

  Within a very narrow range
• What happens to heart rate with increased body temperature?

  It greatly increases the heart rate
• What can happen to heart rate during hypothermia?

  It may fall to a few beats per minute
• What effect does heat have on cardiac muscle membrane permeability?

  It increases permeability to controlling ions
• How does moderate temperature increase affect contractile strength?

  It enhances contractile strength temporarily
• What happens with prolonged elevation of temperature in the heart?

  It exhausts metabolic systems and causes weakness
• What is the effect of increasing arterial pressure on cardiac output?

  It does not decrease cardiac output until 160 mm Hg
• What primarily determines cardiac output during normal heart function?

  The ease of blood flow through tissues
• What controls venous return of blood to the heart?

  The ease of blood flow through tissues
• What are the effects of potassium and calcium ions on heart function?

  • Excess potassium: dilated heart, flaccid, slow heart rate
  • Excess calcium: spastic contraction of the heart
  • Deficiency of calcium: cardiac weakness
• What are the effects of temperature on heart function?

  • Increased temperature: increases heart rate
  • Decreased temperature: decreases heart rate
  • Moderate increase: enhances contractile strength temporarily
  • Prolonged elevation: causes weakness
• What happens to cardiac output with increased arterial pressure?

  • Cardiac output remains stable until mean arterial pressure exceeds 160 mm Hg
  • Determined by ease of blood flow through tissues
  • Controlled by venous return of blood to the heart