Physiology Lab

• What is the source of calcium in skeletal muscle?

  the sarcoplasmic reticulum
• What is the source of calcium in cardiac muscle?

  the sarcoplasmic reticulum and extracellular sources
• What is the means of excitation for cardiac muscle?

  inherent contractions initiated by pacemaker cells
• What is the innervation of skeletal muscle through?

  the somatic nervous system
• What is the innervation of cardiac muscle through?

  the autonomic nervous system
• What is the approximate length of the refractory period in skeletal muscle?

  2-3 msec
• What is the approximate length of the refractory period in the cardiac muscle?

  200 msec or more
• Which ion is responsible for the ling plateau phase of the ventricular muscle action potential?

  Ca++
• What is the long plateau phase of the fast response action potential of cardiac muscle responsible for?

  long refractory period seen in cardiac muscle, prevents cardiac muscle from tetanizing, allows the heart to serve as a pump because the ventricles have time to fill with blood before another contraction can be induced, keeps cardiac muscle in the depolarized state so another contraction cannot be initiated until the heart has had time to contract and refill
• Starling law is demonstrated by what?

  the larger contraction due to increased filling time of the compensatory pause and the smaller contraction due to decreased filling time associated with the extra systole
• During the cardiac cycle, an extra systole can be induced by electrical stimulation during

  the relative refractory period
• T/F the two systems of control over cardiac function are Autoregulation via Einthoven's Law and the nervous system control via somatic nerves

  false
• Starling's law of the heart is the result of what?

  the length-force relationship also observed in skeletal muscle
• Starling's law of the heart holds that the _________, the greater the force of contraction

  greater the venous return, greater the end-diastolic volume, greater the length of myocardial fibers
• The SA-node is innervated by

  both the parasympathetic and sympathetic nervous systems
• The AV-node is innervated by

  both the parasympathetic and sympathetic nervous systems
• The atria are innervated by

  both the parasympathetic and sympathetic nervous systems
• The ventricles are innervated by

  the sympathetic nervous system only
• What neurotransmitter does the parasympathetic nervous system use?

  acetylcholine
• Parasympathetic nervous system can be altered by what?

  cholinergic agonists and antagonists
• How does the parasympathetic nervous system affect heart rate?

  reduces heart rate via stimulation of the SA-node
• How does the parasympathetic nervous system affect K+ permeability?

  increases K+ permeability of cells in the SA-node
• How does the parasympathetic nervous system affect the membrane potential?

  makes the membrane potential in the SA-node more negative, hyperpolarizes the membrane potential in the SA-node, causes the membrane potential to take longer to reach threshold
• How does the parasympathetic nervous system affect prepotential slope?

  decreases prepotential slope of slow response cardiac action potentials
• Starling's law of the heart says that within physiological limits

  the heart pumps out of the blood that returns to it within each cycle
• T/F starling's law of the heart is observed in the absence of any nervous or hormonal control

  true
• T/F starling's law of the heart is controlled by the autonomic nervous system

  false
• T/F starling's law is the result of plasticity similar to that observed in visceral smooth muscle

  false
• T/F starling's law of the heart can also be described as autoregulation

  true
• T/F starling's law of the heart is the result of cardiac fiber length being proportional to end-diastolic volume

  true
• T/F starling's law of the heart is demonstrated by an increased force of contraction with increased stretch of cardiac muscle

  true
• T/F starling's law of the heart is demonstrated by a decreased force of contraction with increased stretch of cardiac muscle

  false
• T/F starling's law of the heart is demonstrated by a decreased force of contraction with decreased stretch of cardiac muscle

  true
• T/F starling's law of the heart is demonstrated when an increased venous return results in a decreased cardiac output

  false
• T/F starling's law of the heart is demonstrated when an increased venous return results in an increased cardiac output

  true
• What neurotransmitter does the sympathetic nervous system use?

  norepinephrine
• How can the sympathetic nervous system function be altered?

  by adrenergic agonists and antagonists
• How does the sympathetic nervous system affect heart rate?

  increases heart rate via stimulation of the SA-node
• How does the sympathetic nervous system affect Ca++ permeability?

  increases Ca++ permeability of cells in the SA-node
• How does the sympathetic nervous system affect membrane potential?

  makes the membrane potential in the SA-node less negative, causes the membrane potential to reach threshold faster