What is the Fick equation? correct answers VO2 = Q x a-vO2 difference
Describe each component of the Fick equation in lay language. correct answers VO2 = maximal oxygen uptake
Q = cardiac output
a-vO2diff = arterial-mixed venous oxygen difference
Cardiac Output (Q) correct answers Q = HR x ...
KIN 310 - Exam 3 || A+ Verified Solutions.
What is the Fick equation? correct answers VO2 = Q x a-vO2 difference
Describe each component of the Fick equation in lay language. correct answers VO2 = maximal
oxygen uptake
Q = cardiac output
a-vO2diff = arterial-mixed venous oxygen difference
Cardiac Output (Q) correct answers Q = HR x SV
- volume of blood ejected by the heart each minute (L/min)
- Heart rate (HR): number of times the heart beat per minute (beats/min)
- Stroke volume (SV): volume of blood ejected by the heart each heart beat (L/beat)
Arterial-mixed venous oxygen difference (a-v Ox diff) correct answers Difference in O2 content
of arterial and venous blood (amount of O2 (ml) taken up by tissues from 100ml of blood)
What is cardiac output? correct answers Q = heart rate x stroke volume
How is cardiac output calculated? correct answers Stroke volume (SV) = EDV - ESV
- EDV: volume ventricle at end of diastole (filling)
- ESV: volume in ventricle at end of systole (contraction)
How does cardiac output differ between males & females and untrained & trained at rest? correct
answers - smaller in females vs. males due to smaller size of heart (smaller SV)
- at rest, similar in trained vs. untrained (trained have lower HR, higher SV)
How does cardiac output differ between untrained & trained athletes at max exercise? correct
answers At max exercise, higher in trained vs. untrained (trained reach similar maximal HR but
have higher SVs)
What is heart rate? correct answers Heart rate is the speed of the heartbeat measured by the
number of contractions (beats) of the heart per minute (bpm).
Explain how heart rate is regulated #1 correct answers Input to cardiovascular center:
- from higher brain centers: cerebral cortex, limbic system, and hypothalamus
- from sensory receptors: proprioreceptors (monitor movements), chemoreceptors (monitor blood
chemistry), baroreceptors (monitor blood pressure)
Output to heart:
- increased rate of spontaneous depolarization in SA node (and AV node) increases heart rate
- increased contractility of atria and ventricles increases stroke volume
- decreased rate of spontaneous depolarization in SA node (and AV node) decreases heart rate
Explain how heart rate is regulated #2 correct answers Parasympathetic nervous system (PNS)
- vagus nerve to SA & AV nodes (preganglionic cell bodies in brain stem)
, - Postganglionic neurons release ACh -> hyper polarizes SA & AV nodes (binds to cholinergic
receptors; decreases rate of spontaneous depolarization (causes a decrease in HR)]
- withdrawal of PNS will increase HR up to ~ 100bpm
Sympathetic nervous system (SNS):
- cardiac accelerator nerves to SA & AV nodes & myocardium [preganglonic cell bodies in
thoracic spinal cord (T1-T5)]
- postganglionic neurons release NE [binds to beta-receptors (causes an increase in HR and force
of myocardial contraction (i.e., contractility)]
What is stroke volume? correct answers SV: the volume of blood ejected by the heart each heart
beat (L/beat)
What three factors regulate stroke volume? correct answers 1. preload
2. afterload
3. contractility
Explain how Preload influences stroke volume. correct answers Preload = end-diastolic volume
(EDV)
- volume of blood in ventricle prior to contraction (i.e., ventricular ejection)
- larger EDV stretches the ventricles [create optimal length of cardiac muscle fibers (i.e.,
sarcomeres) prior to contraction]
- Known as the Frank-Starling law of the heart
- EDV is influenced by how much blood returns to the heart (i.e., venous return)
- venous return influenced by (venoconstriction, muscle pump, respiratory pump)
Explain how Afterload influences stroke volume. correct answers -Afterload = pressure (in aorta)
that must be overcome before ventricular ejection
- hypertension is example of increased afterload
Explain how Contractility influences stroke volume. correct answers - Strength of contraction at
given preload
- NE from cardiac accelerator nerves & NE/E from adrenal medulla (increases force of
myocardial contraction by increasing intracellular calcium)
What are the three factors that affect venous return? correct answers 1. Venoconstriction
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