Transcript Key Questions about the Physiology of the Heart

Key Questions about the
Physiology of the Heart
1. How often does the heart recirculate the body’s blood?
 The heart re-circulates the body’s
supply of blood over 1000 times per
day
2. Describe the intrinsic conduction
system:
 This tissue is like a cross between
muscle and nervous tissue. It causes
heart muscle depolarization in one
direction—from the atria to the
ventricles.
 It enforces a steady contraction rate
of approximately 75 beats per minute
on cardiac muscle
3. What is the sinoatrial (SA) node?
 The SA node is a crescent-shaped
node of tissue located in the right
atrium. It’s function is to start each
heart beat and set the pace for the
heart
4. Trace the path of a
depolarization impulse:
 From the SA node, it spreads through
the atria to the AV node, causing the
atria to contract
 At the AV node, the impulse pauses
to allow the atria to contract, then it
passes rapidly through the AV bundle,
resulting in a “wringing” motion of
the ventricles
5. What is fibrillation, and what
causes it?
 Fibrillation is a rapid, uncoordinated
shuddering of heart muscle caused by
ischemia, which is a lack of adequate
blood supply to the heart muscle
6. Contrast tachycardia and
bradycardia:
 Tachycardia is a rapid heart beat
(over 100 beats per minute)
 Bradycardia is a slow heart beat (less
than 60 beats per minute)
7. What are systole and diastole?
 Systole is contraction of atria or
ventricles
 Diastole is relaxation of the ventricles
8. What causes the “lub” and “dup”
sounds of the heart beat?
 The “lub” is caused by the closing of
the AV valves
 The “dup” is the closing of the
semilunar valves at the end of systole
9. What are murmurs? What do
they indicate?
 Abnormal or unusual heart sounds
are murmurs, caused when blood
strikes obstructions in its flow.
 Murmurs indicate problems with the
valves of the heart
10. What is cardiac output, and
what is the average for an adult?
 Cardiac output is the amount of blood
pumped out by each ventricle in 1
minute. It is the product of heart rate
and stroke volume.
 The average adult cardiac output is
5250 ml per minute
11. What is Starling’s Law of the
Heart?
 The critical factor controlling stroke
volume is how much the cardiac
muscle cells are stretched just before
they contract
12. When does the sympathetic
division stimulate the heart to beat
faster?
 During times of physical or emotional
stress, such as being frightened or
running to catch a bus, the
sympathetic division stimulates the
heart to beat faster
13. How does heart rate change?
 Resting heart rate is fastest in the
fetus, then gradually decreases
throughout life
 The average heart rate is about 8
beats per minute higher in women
than men
14. What is congestive heart
failure?
 Congestive heart failure occurs when
the pumping efficiency of the heart is
depressed so that circulation is
inadequate to meet tissue needs.
 It reflects weakening of the heart by
coronary artherosclerosis
15. Describe the effects of
pulmonary congestion and
peripheral congestion:
 Pulmonary: if the left side of the heart
fails, the right side continues to pump
blood to the lungs. Blood vessels in the
lungs back up and become swollen with
blood, causing suffocation
 Peripheral: blood backs up in the
systemic circulation, specifically the
distal parts of the body (feet, ankles, or
fingers)