Chapter 14: The Cardiovascular System - The Heart Flashcards
(106 cards)
1
Q
What are the two closed circuits the heart pumps blood into?
A
Pulmonary circulation and systemic circulation
2
Q
What does the pulmonary circulation consist of?
A
Blood vessels that carry blood from the right side of the heart to the alveoli of the lungs and back to the left side of the heart
3
Q
What is the function of systemic circulation?
A
Carries blood from the left side of the heart to all organs and tissues of the body except the alveoli and back to the right side of the heart
4
Q
What type of blood vessels carry blood away from the heart?
A
Arteries
5
Q
What are arterioles?
A
Smaller vessels that branch from arteries
6
Q
What are capillaries?
A
The smallest blood vessels that serve as sites of gas, nutrient, and waste exchange between blood and surrounding tissues
7
Q
What happens to blood in pulmonary capillaries?
A
Blood becomes oxygenated as it picks up oxygen and drops off carbon dioxide
8
Q
What color is oxygenated blood?
A
Bright red
9
Q
What color is deoxygenated blood?
A
Dark red
10
Q
True or False: Blood vessels containing oxygenated blood are colored blue.
A
False
11
Q
What is a portal system?
A
A system where blood flows from one capillary network into a portal vein and then into a second capillary network before returning to the heart
12
Q
What is the hepatic portal circulation?
A
Carries absorbed nutrients in blood from capillaries in gastrointestinal organs to capillaries in the liver
13
Q
What separates the right and left sides of the heart?
A
A muscular partition called the septum
14
Q
What is the epicardium?
A
The outer layer of the heart wall, also known as the visceral layer of the pericardium
15
Q
What is the myocardium?
A
The middle layer of the heart wall that consists of cardiac muscle
16
Q
What is the endocardium?
A
The thin inner layer of the heart that lines the chambers and covers heart valves
17
Q
What are endothelial cells?
A
Epithelial cells that line the heart, blood vessels, and lymphatic vessels
18
Q
How many chambers does the heart have?
A
Four chambers: two atria and two ventricles
19
Q
What function does the right side of the heart serve?
A
Pumps blood for pulmonary circulation
20
Q
What function does the left side of the heart serve?
A
Pumps blood for systemic circulation
21
Q
What is the function of the atrioventricular (AV) valves?
A
Prevent backflow of blood between the atria and ventricles
22
Q
What are the two types of AV valves?
A
- Tricuspid valve (right AV valve)
- Bicuspid valve (left AV valve or mitral valve)
23
Q
What prevents the AV valve cusps from everting?
A
Chordae tendineae connected to papillary muscles
24
Q
What are semilunar (SL) valves?
A
Valves that allow ejection of blood from the heart into arteries but prevent backflow into the ventricles
25
What are the two semilunar valves of the heart?
* Pulmonary valve
* Aortic valve
26
What is the fibrous skeleton of the heart?
A structure of dense connective tissue that surrounds the valves and prevents overstretching
27
What is the coronary circulation?
The network of blood vessels that supplies blood to the heart wall
28
Where do coronary arteries branch from?
The aorta
29
What is the size of a typical cardiac muscle fiber?
50–100 μm long and about 14 μm in diameter
30
What are intercalated discs?
Irregular transverse thickenings of the sarcolemma that connect cardiac muscle fibers
31
What types of junctions are found in intercalated discs?
* Desmosomes
* Gap junctions
32
What is the function of desmosomes in cardiac muscle?
Mechanically bind cardiac muscle fibers together and resist mechanical stress
33
What is the role of gap junctions in cardiac muscle?
Allow action potentials to conduct between cardiac muscle fibers
34
What are intercalated discs in cardiac muscle fibers?
Intercalated discs contain desmosomes and gap junctions.
35
What is the function of desmosomes in cardiac muscle?
Desmosomes mechanically bind cardiac muscle fibers together and resist mechanical stress.
36
What is the role of gap junctions in cardiac muscle?
Gap junctions electrically couple cardiac muscle fibers, allowing action potentials to spread.
37
What is a functional syncytium in the context of cardiac muscle?
A mass of interconnected muscle fibers that contract together as a single unit.
38
How do the atria and ventricles contract in the heart?
The atria contract before the ventricles, allowing blood to fill the ventricles.
39
What percentage of sarcoplasm volume do mitochondria occupy in cardiac muscle fibers?
Mitochondria take up 25% of the volume of the sarcoplasm in cardiac muscle fibers.
40
What is the term for the built-in rhythm of cardiac muscle contractions?
Autorhythmicity.
41
What are the two types of muscle fibers in cardiac muscle?
Autorhythmic fibers and contractile fibers.
42
What is the primary function of autorhythmic fibers?
They spontaneously generate action potentials.
43
Where is the sinoatrial (SA) node located?
In the wall of the right atrium near the opening of the superior vena cava.
44
What is the function of the atrioventricular (AV) node?
It conducts action potentials from the atria to the ventricles.
45
What is the conduction system of the heart?
The pathway that delivers action potentials throughout the heart muscle.
46
What is a pacemaker potential?
The spontaneous depolarization to threshold in autorhythmic fibers.
47
What can modify the timing and strength of each heartbeat?
Action potentials from the autonomic nervous system and blood-borne hormones.
48
What happens if the SA node is damaged?
The AV node can take over the pacemaking task, but at a slower rate.
49
What is the stable resting membrane potential of contractile cardiac muscle fibers?
About -90 mV.
50
What are the four phases of action potentials in contractile cardiac muscle fibers?
Depolarizing phase, initial repolarizing phase, plateau phase, final repolarizing phase.
51
What occurs during the depolarizing phase?
Fast voltage-gated Na+ channels open, allowing Na+ to flow into the cell.
52
What causes the plateau phase of the action potential?
The opening of L-type voltage-gated Ca2+ channels.
53
What is Ca2+-induced Ca2+ release (CICR)?
The process where extracellular Ca2+ triggers the release of additional Ca2+ from the sarcoplasmic reticulum.
54
How do cardiac muscle fibers produce graded contractions?
By increasing the strength of contraction of existing muscle fibers through more Ca2+.
55
What is the role of Ca2+ in cardiac muscle contraction?
Ca2+ binds to troponin, allowing crossbridge formation between actin and myosin.
56
What is the function of Ca2+–ATPase pumps in cardiac muscle fibers?
They actively transport Ca2+ from the sarcoplasm into the sarcoplasmic reticulum.
57
What characterizes the refractory period in cardiac muscle fibers?
It lasts about 250 msec, preventing summation of contractions.
58
Why is the refractory period important in cardiac muscle?
It allows for alternating contraction and relaxation, essential for heart function.
59
What fuels does cardiac muscle primarily use for ATP production?
Fatty acids (60%) and glucose (35%).
60
What type of respiration does cardiac muscle primarily rely on?
Aerobic respiration
## Footnote
Cardiac muscle has numerous mitochondria for ATP production and relies on oxygen from blood and myoglobin.
61
What are the main fuels used by cardiac muscle at rest for ATP production?
* Fatty acids (60%)
* Glucose (35%)
* Lactic acid
* Amino acids
* Ketone bodies
## Footnote
Cardiac muscle's ATP production varies with activity level.
62
What enzyme is a marker for myocardial infarction?
Creatine kinase (CK)
## Footnote
CK is released into the blood from injured cardiac or skeletal muscle fibers.
63
What does an electrocardiogram (ECG) record?
Electrical signals generated by the heart
## Footnote
The ECG is a composite record of action potentials from all heart muscle fibers.
64
What does the P wave in an ECG represent?
Atrial depolarization
## Footnote
The P wave appears as a small upward deflection on the ECG.
65
What does the QRS complex represent in an ECG?
Ventricular depolarization
## Footnote
The QRS complex begins with a downward deflection and ends with a downward wave.
66
What does the T wave indicate in an ECG?
Ventricular repolarization
## Footnote
The T wave is dome-shaped and occurs as the ventricles start to relax.
67
True or False: The T wave is smaller and wider than the QRS complex.
True
## Footnote
Repolarization occurs more slowly than depolarization.
68
What does a larger P wave in an ECG indicate?
Enlargement of an atrium
## Footnote
ECG wave sizes can provide diagnostic clues.
69
What does an enlarged Q wave in an ECG suggest?
Myocardial infarction
## Footnote
Changes in wave size can indicate various heart conditions.
70
What is the P–Q interval?
The time from the beginning of the P wave to the beginning of the QRS complex
## Footnote
It represents conduction time from atrial to ventricular excitation.
71
What happens to the P–Q interval when there is scar tissue in the heart?
It lengthens
## Footnote
Conditions like coronary artery disease can affect conduction time.
72
What does the S–T segment represent in an ECG?
The time when ventricular contractile fibers are depolarized
## Footnote
It occurs during the plateau phase of the action potential.
73
What does an elevated S–T segment indicate?
Acute myocardial infarction
## Footnote
Depression of the S–T segment suggests insufficient oxygen.
74
What is the cardiac cycle?
All events associated with one heartbeat
## Footnote
It includes diastole and systole of both the atria and ventricles.
75
List the five phases of the cardiac cycle.
* Passive ventricular filling
* Atrial contraction
* Isovolumetric ventricular contraction
* Ventricular ejection
* Isovolumetric ventricular relaxation
## Footnote
Understanding these phases is crucial for cardiac function analysis.
76
What occurs during passive ventricular filling?
Blood flows from the atria into the ventricles without muscle contraction
## Footnote
This phase accounts for about 80% of ventricular filling.
77
What is end-diastolic volume (EDV)?
The volume of blood in each ventricle at the end of relaxation
## Footnote
Typically about 130 mL at the end of ventricular diastole.
78
What happens during isovolumetric ventricular contraction?
Both the AV and SL valves are closed, and ventricular volume remains the same
## Footnote
This phase involves pressure increase without volume change.
79
What is stroke volume (SV)?
The volume ejected from each ventricle per beat
## Footnote
Calculated as SV = EDV - ESV.
80
What is ejection fraction (EF)?
The percentage of end-diastolic volume ejected with each stroke
## Footnote
EF is calculated as EF = SV/EDV × 100.
81
What causes the first heart sound (S1)?
Closure of the AV valves
## Footnote
S1 is described as a 'lubb' sound.
82
What causes the second heart sound (S2)?
Closure of the SL valves
## Footnote
S2 is described as a 'dupp' sound.
83
How is cardiac output (CO) calculated?
CO = Stroke Volume (SV) × Heart Rate (HR)
## Footnote
In a typical adult male at rest, CO is about 5.25 L/min.
84
What is cardiac reserve?
The difference between maximum cardiac output and cardiac output at rest
## Footnote
It indicates the heart's capacity to increase output during activity.
85
What is cardiac output (CO)?
The amount of blood the heart pumps in one minute.
## Footnote
Cardiac output is calculated as heart rate multiplied by stroke volume.
86
What is stroke volume during mild exercise?
100 mL/beat.
## Footnote
During mild exercise, heart rate can increase to 100 beats/min.
87
What is the cardiac output during intense exercise?
19.5 L/min.
## Footnote
At this level, heart rate may reach 150 beats/min and stroke volume may rise to 130 mL/beat.
88
Define cardiac reserve.
The difference between a person’s maximum cardiac output and cardiac output at rest.
## Footnote
Average cardiac reserve is four or five times the resting value.
89
What is preload?
The degree of stretch on the heart before it contracts.
## Footnote
It is proportional to the end-diastolic volume (EDV).
90
What is the Frank–Starling law of the heart?
The relationship where a greater preload increases the force of contraction.
## Footnote
Describes how the heart pumps more effectively with increased filling.
91
What are the three major factors that regulate stroke volume?
* Preload
* Contractility
* Afterload
92
What is contractility?
The strength of contraction at any given preload.
## Footnote
It can be influenced by positive or negative inotropic agents.
93
What is afterload?
The pressure that must be exceeded before ejection of blood from the ventricles can occur.
## Footnote
Increased afterload decreases stroke volume.
94
What happens to stroke volume when heart rate exceeds 160 beats/min?
Stroke volume usually declines due to short filling time.
## Footnote
This results in a lower end-diastolic volume (EDV).
95
What is the effect of sympathetic nervous system stimulation on heart rate?
It increases heart rate.
## Footnote
This occurs by increasing spontaneous depolarization in SA node cells.
96
What is the effect of parasympathetic nervous system stimulation on heart rate?
It decreases heart rate.
## Footnote
This is achieved by decreasing spontaneous depolarization in SA node cells.
97
What are positive inotropic agents?
Agents that increase contractility.
## Footnote
Examples include norepinephrine and epinephrine.
98
What are negative inotropic agents?
Agents that decrease contractility.
## Footnote
Examples include calcium channel blockers and excess H+ ions.
99
What is the role of calcium in contractility?
Calcium levels influence the strength of contraction in cardiac muscle.
## Footnote
Increased Ca2+ levels enhance contractility.
100
How do hormones like epinephrine affect heart function?
They enhance heart rate, action potential conduction, and contractility.
## Footnote
They bind to β1 receptors in cardiac cells.
101
How does age affect resting heart rate?
Resting heart rate decreases as a person ages.
## Footnote
Newborns have a higher resting heart rate than adults.
102
What is the impact of body temperature on heart rate?
Increased body temperature raises heart rate; decreased body temperature lowers it.
## Footnote
Fever or strenuous exercise can speed up heart rate.
103
What is the typical resting heart rate for an adult?
About 75 beats/min.
## Footnote
This rate is lower than the SA node's autorhythmic rate of roughly 100 beats/min.
104
What does a positive chronotropic effect do?
Increases heart rate.
## Footnote
This can be caused by sympathetic stimulation.
105
What does a negative chronotropic effect do?
Decreases heart rate.
## Footnote
This can be caused by parasympathetic stimulation.
106
What is the primary role of the sinoatrial (SA) node?
To initiate contraction and set heart rate.
## Footnote
It would set a constant heart rate of about 100 beats/min if not influenced by external factors.
