Physiology Exam 3 - Cardiovascular System Flashcards
1
Q
What makes up the cardiovascular system?
A
heart and blood vessels
2
Q
What makes up the circulatory system?
A
heart, blood vessels, and blood
3
Q
What systems affect cardiovascular function?
A
endocrine, nervous, and urinary
4
Q
Pulmonary circulation
A
carries deoxygenated blood from the right ventricle to the lung for gas exchange and back (right side of heart)
5
Q
Systemic circulation
A
supplies oxygenated blood from the left ventricle to all tissues of the body and returns it to the heart (left side of heart)
6
Q
Right and left ventricles
A
- two inferior chambers
- pump blood into the arteries
7
Q
Right and left atria
A
- two superior chambers
- receive blood returning to the heart
8
Q
Arteries
A
carry blood away from the heart
9
Q
Veins
A
carry blood back to the heart
10
Q
Capillaries
A
connect smallest arteries to smallest veins to create a circuit
11
Q
What type of blood do arteries carry?
A
oxygenated blood
12
Q
What type of blood do veins carry?
A
deoxygenated blood
13
Q
What type of blood does the pulmonary artery carry?
A
deoxygenated blood
14
Q
What type of blood does the pulmonary vein carry?
A
oxygenated blood
15
Q
Where is the majority of the blood distributed in the body?
A
abdominal organs - small intestine and liver
16
Q
Pressure
A
the force exerted by the blood, measured in mmHg
17
Q
How does blood flow according to pressure?
A
from higher pressure to lower pressure
18
Q
Flow
A
the volume of blood moved per unit time, measured in mL/min
19
Q
Resistance
A
how difficult it is for blood to flow between two points at any given pressure difference; the measure of friction that impedes flow
20
Q
F = change in P/R
A
flow rate is directly proportional to the pressure difference and inversely proportional to the resistance
21
Q
What are factors that determine resistance?
A
blood viscosity, total blood vessel length, and blood vessel radius
22
Q
Blood viscosity
A
friction between molecules of a flowing fluid; affected by water volume and total number of erythrocytes
23
Q
Blood vessel length
A
remains constant
24
Q
Blood vessel radius
A
not constant, inversely proportional to resistance; dilated vessels decrease resistance, while constricted vessels increase resistance
25
What are the layers of the heart wall (outer to inner)?
epicardium, myocardium (contains cardiomyocytes), endocardium
26
Cardiomyocytes
cardiac muscle cells arranged in layers
27
What happens to cardiomyocytes with every heart beat?
they contract in unison (no resting - 3 billion during lifespan)
28
Can the human body replace cardiomyocytes?
limited ability by specialized stem cells - only about 1% ability
29
Specialized cardiomyocytes
1% of cells, excitable but do not contract
30
Pacemaker cells
constitute a network, conducting system, electrical contact through all cardiomyocytes via gap junctions; initiate the heartbeat and spread an action potential rapidly throughout the entire heart
31
Sympathetic fibers
innervate the entire heart, release norepinephrine
32
Parasympathetic fibers
innervate special cells in the atria, release primarily acetylcholine
33
What is the order of cardiac rhythmic electrical signals?
1. Sinoatrial (SA) node
2. Atrioventricular (AV) node
3. Atrioventricular (AV) bundle (bundle of His)
4. Subendothelial conducting networks
34
What is another name for the SA node?
the pacemaker
35
What does the SA node do?
stimulates the two atria to contract almost simultaneously (reaches AV node in 50 ms)
36
What is the AV node structure?
thin cardiomyocytes with few gap junctions
37
What happens as the signal travels through the AV node?
it slows down (delayed 100 ms) to allow ventricles to fill
38
What happens as the signal reaches the AV bundle (bundle of His)?
- the bundle splits into right and left branches that pass through the interventricular septum toward the apex
- signals quickly travel through right and left AV bundle and reach the subendothelial conducting network
39
What is another name for the subendothelial conducting network?
Purkinje fibers
40
What is another name for the AV bundle?
bundle of His
41
What is the subendothelial conducting network and what does it do?
- nerve-like processes spread throughout ventricular myocardium
- cardiomyocytes then pass the signal from cell to cell through gap junctions.
42
What happens after the cardiomyocytes pass the signal from cell to cell?
- ventricular systole occurs, progressing up from the apex of the heart (spiral arrangement of myocardium twists ventricles slightly)
43
Sinus rhythm
normal heartbeat triggered by the SA node (typically 70 - 80 bpm)
44
How often does the SA node fire?
every 0.8 sec (resting heartbeat = 75 bpm)
45
Ectopic focus
a region of spontaneous firing other than the SA node (can govern heart rhythm if SA node is damaged) (20 - 40 bpm - cannot sustain life)
46
Nodal rhythm
if the SA node is damaged, the heart rate is set by the AV node (set at 40 - 50 bpm)
47
What is the resting potential of cardiomyocytes?
-90 mV
48
What are the phases of cardiomyocyte potential?
depolarization, plateau, repolarization, and baseline
49
What happens during the depolarization phase of cardiomyocytes?
- voltage-gated Na+ channels open
- Na+ rushes into the sarcoplasm
- membrane rapidly depolarizes
- action potential peaks at +30 mV
- Na+ channels close quickly
50
What happens during the plateau phase of cardiomyocytes?
- voltage-gated Ca2+ channels open (slow); L-type channels (long lasting)
- Ca2+ enters, triggering opening of Ca2+ channels on sarcoplasmic reticulum
- Ca2+ (from SR) binds to troponin, triggering contraction
- sustains contraction from expulsion of blood from the heart
51
What happens during the repolarization phase of cardiomyocytes?
- Ca2+ channels close
- K+ channels open
- rapid exit of K+ out of cell returns membrane to resting potential
52
Why does the ventricular action potential have a long absolute refractory period?
to prevent wave summation and tetanus, which would stop the pumping of the heart
53
What are the phases of SA node action potential?
- pacemaker potential
- depolarization
- repolarization
54
What occurs during the pacemaker potential?
- starts at -60 mV
- potential drifts upward from slow Na+ inflow through non-specific cation F-type channels ("funny" current)
- pacemaker potential provides the SA node with automaticity (can induce themselves their own signal)
55
What occurs during the depolarization of the SA node?
- when the membrane reaches -40 mV, voltage-gated Ca2+ channels (T-type transient) and other types of Na+ channels open
56
What occurs during the repolarization of the SA node?
- voltage-gated K+ channels open
- K+ leaves the cell
- once K+ channels close, the pacemaker potential starts over
57
What are artificial/cardiac pacemakers?
electronic devices that are implanted in the body to monitor heart rate and rhythm; gives heart electrical stimulation when it does not beat normally
58
What is the most common sustained arrhythmia observed in the clinic?
A-fib
59
What are the phases of the cardiac cycle?
1. ventricular filling
2. isovolumetric contraction
3. ventricular ejection
4. isovolumetric relaxation
60
What is the cardiac cycle?
one complete contraction and relaxation of all four chambers of the heart
61
What happens when ventricles relax?
- they expand and the internal pressure falls
- AV values (tricuspid and mitral) open, and blood flows into the ventricles
62
What happens when ventricles contract?
- they constrict and the internal pressure rises
- AV valves close and the semilunar valves (aortic and pulmonary) open and blood flows into the aorta or pulmonary trunk
63
What determines the opening and closing of valves?
changes in pressure
64
What are the AV valves like when ventricles are relaxed?
limp
65
What are the semilunar valves like when the ventricles are relaxed?
under pressure from blood in vessels
66
Auscultation
listening to sounds made by the body
67
What is the first heart sound called?
S1
68
What is the second heart sound called?
S2
69
What are two other heart sounds besides S1 and S2?
S3 and S4
70
What describes the first heart sounds (S1)?
- louder and longer "Lub"
- occurs with the closure of AV valves
71
What describes the second heart sounds (S2)?
- softer and sharper "Dub"
- occurs with the closure of semilunar valves
72
What describes the S3 heart sound?
- occurs after the S2 sound
- called "ventricular gallop"
- rarely heard in people over 30
73
What describes the S4 heart sound?
- occurs just before the S1 sound
- called "atrial gallop"
- results from the contraction of the atria pushing blood into a stiff or hypertrophic ventricle
- indicates failure of the left ventricle
74
When does ventricular filling occur?
during diastole
75
When does isovolumetric contraction occur?
during systole
76
When does ventricular ejection occur?
during systole
77
When does isovolumetric relaxation occur?
during diastole
78
How long does it take for the cardiac cycle to complete?
less than 1 second
79
What happens during the ventricular filling phase of the cardiac cycle?
- the ventricles expand and the pressure drops below that of the atria
- the AV valves open and blood flows into the ventricles
80
What are the phases of ventricular filling?
1a. Rapid ventricular filling - first one-third; S3 sound
1b. Diastasis - second one-third; slower filling; P wave starts
1c. Atrial systole - final one-third; atria contract
81
What happens during the isovolumetric contraction phase of the cardiac cycle?
- atria repolarize, relax and remain in diastole for the rest of the cardiac cycle
- ventricles finish depolarizing, causing QRS complex, and begin to contract
- AV valves close
- S1 occurs at the beginning
82
What does the term "isovolumetric" indicate in isovolumetric contraction?
- pressures in the aorta and pulmonary trunk are still greater than in ventricles
- all four valves are closed and the blood cannot go anywhere
83
What happens during the ventricular ejection phase of the cardiac cycle?
- begins when ventricular pressure exceeds arterial pressure and the semilunar valves open
- pressure peaks in the left ventricle at 120 mmHg and 25 mmHg in the right
- first: rapid ejection - blood spurts out quickly
- then: reduced ejection - slower flow with lower pressure
- ejection corresponds to the plateau phase of the cardiac action potential (200 to 250 ms)
- T wave of EKG occurs late in this phase
84
What happens during the isovolumetric relaxation phase of the cardiac cycle?
- T wave ends and ventricles begin to expand
- backward flow of blood from the aorta and pulmonary trunk closes the semilunar valves
- S2 heart sound occurs
85
What is the End-systolic volume?
60 mL
86
What is the End-diastolic volume?
130 mL
87
What is congestive heart failure?
- failure of either ventricle to eject blood effectively
- common cause: heart wall weakened by ischemia
- symptoms depend on which ventricle is failing
88
What occurs because of left ventricular failure?
- the volume of blood from the right ventricle exceeds the left ventricular output
- pressure backs up and blood backs up into the lungs causing pulmonary edema
- shortness of breath or a sense of suffocation
89
What occurs because of right ventricular failure?
- volume of blood from the left ventricle exceeds the right ventricular output
- pressure backs up and blood backs up in the vena cava causing systemic edema
- liver enlargement, ascites (fluid in abdomen), jugular veins distension, swelling of fingers, ankles and feet
- eventually leads to total heart failure
90
What is the only treatment for total heart failure?
heart transplant
91
What are heart rhythm and contraction controlled by?
cardiac centers located in the medulla oblongata
92
Cardioacceleratory center
- sends sympathetic innervation via that cardiac nerves
- increases heart rate and contraction strength
93
Cardioinhibitory center
- sends parasympathetic innervation via the vagus nerve
- slows heart rate
94
Cardiac output
the amount of blood ejected by each ventricle in 1 minute
95
What is the equation for cardiac output?
CO = heart rate x stroke volume
96
What is the cardiac output at rest?
4 to 6 L/min
97
What is the cardiac output with vigorous exercise?
21 L/min (fit person) or 40 L/min (world-class athlete)
98
Cardiac reserve
the difference between a person's maximum and resting cardiac output (increases with fitness, decreases with disease)
