Chapter 20 - Cardiovascular System: The Heart Flashcards
(167 cards)
1
Q
Where is the heart located?
A
It rests on the diaphragm, near the midline of the thoracic cavity
2
Q
What is the mediastinum?
A
An anatomical region that extend from the sternum to the vertebral column
- from the first rib to the diaphragm and between the lungs
3
Q
What is the apex of the heart?
A
The pointed tip of the left ventricle
4
Q
What is the base of the heart?
A
Its posterior surface
- formed by the atria (upper chambers)
- mostly the left atrium
5
Q
Where is the anterior surface of the heart?
A
Deep to the sternum and ribs
6
Q
Where is the inferior surface of the heart?
A
Between the apex and right border
- rests mostly on the diaphragm
7
Q
What does the right border of the heart face?
A
Faces the right lung
- extends from the inferior surface to the base
8
Q
What does the left border of the heart face?
A
Faces the left lung
- extends from the base to the apex
- *also called the pulmonary border
9
Q
What is the pericardium?
A
Membrane that surrounds and protects the heart
10
Q
What are the two main parts of the pericardium?
A
- Fibrous pericardium (superficial layer)
2. Serous pericardium (deep layer)
11
Q
What is the function of the fibrous pericardium?
A
- prevents overstretching of the heart
- provides protection
- anchors heart to the mediastinum
12
Q
What is the fibrous pericardium partly fused to?
What does this do?
A
Central tendon of the diaphragm
- facilitates movement of blood by the diaphragm (when deep breathing occurs)
13
Q
What are the two layers of the serous pericardium?
A
- Parietal layer
2. Visceral layer (also called epicardium)
14
Q
What is the parietal layer of the serous pericardium fused to?
A
Fibrous pericardium
15
Q
What is the visceral layer of the serous pericardium tightly adhered to?
A
Surface of the heart
16
Q
What is between the parietal and visceral layers of the serous pericardium?
What is it’s function?
A
Pericardial fluid
- reduces friction between the layers as the heart moves
17
Q
What is the name of the space that contain pericardial fluid?
A
Pericardial cavity
18
Q
What are the three layers of the heart wall?
A
- Epicardium (outer layer)
- Myocardium (middle layer)
- Endocardium (inner layer)
19
Q
What give the heart a smooth, slippery texture at the outermost surface of the heart?
A
The epicardium
20
Q
What does the epicardium layer contain?
A
- adipose tissue
- blood vessels
- lymphatics
- vessels that supply myocardium
21
Q
What is the myocardium layer of the heart responsible for?
A
The pumping action of the heart
22
Q
What is the myocardium layer composed of?
A
Cardiac muscle tissue
- makes up 95% of the heart wall
23
Q
What is the function of the endocardium?
A
- provides a smooth lining for the chambers of the heart
- covers the values of the heart
- minimizes surface friction as blood passes through the heart
24
Q
What are the 4 chambers of the heart?
A
- Right atria
- Left atria
- Right ventricle
- Left ventricle
25
What is the function of the atria?
Receive blood from veins
26
What is the function of the ventricles?
Pump blood into arteries
27
What are the auricles?
Wrinkled pouch-like structure on the anterior surface of each atrium
28
What is the function of the auricles?
Slightly increases the capacity of an atrium (more blood)
29
What is the coronary sulcus?
Deep groove on the surface of the heart
| - encircles most of the heart
30
What does the coronary sulcus mark?
Marks the external boundaries between the superior atria and inferior ventricles
31
What does a sulcus contain?
Contains coronary blood vessels and a variable amount of fat
32
What three veins supply the right atrium?
1. Superior vena cava
2. Inferior vena cava
3. Coronary sinus
33
What is the interatrial septum?
A thin partition between the right and left atria
34
What is the prominent feature of the interatrial septum?
An oval depression - Fossa Ovalis
| - in the right atrium
35
What is the fossa ovalis?
Remnant of the foramen ovale
| - an opening in the interatrial septum of the fetal heart that normally closes soon after birth
36
How does blood pass through the tricuspid valve?
| Right atrioventricular valve
Passes from the RIGHT ATRIUM into the RIGHT VENTRICLE
37
What forms most of the anterior surface of the heart?
The right ventricle
38
What are the chordae tendineae connected to?
Tendonlike cords
| - tricuspid valve connects to chordae tendineae, which connects to papillary muscles
39
What are papillary muscles?
Cone-shaped trabeculae carneae (raised bundles of cardiac muscle fibres)
40
What is the interventricular septum?
How the RIGHT VENTRICLE is separated from the LEFT VENTRICLE
41
How does blood pass through the pulmonary valve?
Blood passes from RIGHT VENTRICLE through the pulmonary valve into the pulmonary trunk (large artery)
42
What does the pulmonary trunk divide into?
| What does it service?
Divides into right and left pulmonary arteries
| - carries blood to the lungs
43
What is the mnemonic to aid in remembering the function of arteries and veins?
Arteries carry blood AWAY from the heart
| Artery = Away
44
What forms most of the base of the heart?
Left atrium
45
What is the bicuspid valve?
(Mitral valve)
(Left atrioventricular valve)
Blood passes from the LEFT ATRIUM into the LEFT VENTRICLE
46
Which chamber is the thickest in the heart?
The left VENTRICLE
| - forms the apex of the heart
47
How does blood pass through the aortic valve?
Blood passes from the LEFT VENTRICLE through the aortic valve into the ascending aorta
48
What happens to some of the blood in the aorta?
Flows into coronary arteries
| - carry blood to the heart wall
49
Which ventricle has a thicker muscular wall?
| Why?
LEFT ventricle
| - pumps blood a greater distance in the body and under greater resistance
50
What does the fibrous skeleton of the heart consist of?
Consists of 4 dense connective tissue rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum
51
What is the function of the fibrous skeleton of the heart?
- forms structural foundation
- prevents overstretching
- serves as a point of insertion for bundles of cardiac muscle fibres
- acts as an electrical insulator between the atria & ventricles
52
What are the atrioventricular (AV) valves?
1. Tricuspid valve
| 2. Bicuspid valve
53
What happens with regards to blood flow when the ventricles are relaxed?
- ventricles relaxes, papillary muscles are relaxed
| - blood moves from a higher pressure in the atria to a lower pressure in the ventricles through the open AV valves
54
What happens with regards to blood flow when the ventricles contract?
- pressure of the blood drives the cusps upwards, closes their openings
- papillary muscles contract which tighten chordae tendineae
55
What are the semilunar (SL) valves?
1. Aortic valve
| 2. Pulmonary valve
56
What do the SL valves allow?
| What do the SL valves prevent?
Allow - Ejection of blood from the heart into arteries
| Prevent - backflow of blood into ventricles
57
When do the semilunar valves open?
When pressure in the ventricles exceeds the pressure in the arteries
58
Which heart valve is most commonly replaced?
Aortic valve
59
What kind of circulation does the left side of the heart pump?
Systemic circulation
60
What is systemic circulation?
Circulation of bright red OXYGENATED (oxygen-rich) blood from the lungs
61
Describe the flow of blood in systemic circulation.
LEFT side of heart receives oxygenated blood from the lungs
- ejects blood into aorta
- from aorta, divides into separates streams; smaller systemic arteries
- into arterioles, into systemic capillaries
- unloads oxygen into cells
- enters systemic venule, into systemic veins
- flows into RIGHT atrium
62
What kind of circulation does the right side of the heart pump?
Pulmonary circulation
63
What is pulmonary circulation?
Circulation of dark-red DE-OXYGENATED blood returning from systemic circulation
64
Describe the flow of blood in pulmonary circulation.
- blood ejected from the RIGHT ventricle flows into pulmonary trunk
- branches into pulmonary arteries (carry blood to lungs)
- dump CO2, pick up oxygen
- flows from capillaries, into veins
- returns to LEFT atrium
65
What is coronary (cardiac) circulation?
The network of blood vessels that supply the heart
66
What is the function of the coronary arteries?
| Where do they branch from?
Supply oxygenated blood to the myocardium
| - right and left coronary arteries branch from ascending aorta
67
What is the function of the coronary veins?
The de-oxygenated blood from the myocardium drains into a large vascular sinus (coronary sinus)
- empties into the right atrium
68
What are the principal tributaries that carry blood into the coronary sinus?
1. Great cardiac vein
2. Middle cardiac vein
3. Small cardiac vein
4. Anterior cardiac veins
69
What is the coronary sinus?
| Where is it located?
A wide venous channel, that receives blood from the coronary veins and empties into the right atrium of the heart
- the posterior surface of the heart
70
What are the 10 steps of systemic and pulmonary circulaton?
1. Right atrium (de-oxygenated blood)
- tricuspid valve
2. Right ventricle
- Pulmonary valve
3. Pulmonary trunk and pulmonary arteries
4. Pulmonary capillaries (exchange 02 & CO2)
5. Pulmonary veins (oxygenated blood)
6. Left atrium
- bicuspid valve
7. Left ventricle
- aortic valve
8. Aorta and systemic arteries
9. Systemic capillaries (exchange 02 & CO2)
10. Superior and inferior vena cava and coronary sinus
* repeats from 1.
71
Describe the histology of cardiac muscle.
- 50-100 micrometers long
- 14 mincrometers wide
- 1 centrally located nucleus (some have 2)
- exhibit branching
72
What are intercalated discs?
Irregular transverse thickenings of the sarcolemma
| - separate opposing ends of cardiac muscle cells
73
What is the function of desmosomes?
Holds cardiac muscle fibres together
74
What is the function of gap junctions in cardiac muscle cells?
Allows muscle action potentials to conduct from one muscle fibre to its neighbours
- allows entire myocardium of the atria/ventricles to contract as a single, coordinated unit
75
What are autorhythmic fibers?
The source of the rhythmical electrical activity of the heart
76
What do autorhythmic fibers generate?
Repeatedly generate action potentials that trigger heart contractions
77
What are the two important functions of autorhythmic fibers?
1. Act as a pacemaker
| 2. Form the cardiac conduction system
78
What is the cardiac conduction system?
A network of specialized cardiac muscle fibres that provide a path for each cycle of cardiac excitation to progress through the heart
79
What does a pacemaker do?
Sets the rhythm of electrical excitation that causes contraction of the heart
80
What is the pacemaker potential?
Spontaneous depolarization
81
What is the sinoatrial node?
| Where is it located?
Small body of specialized muscle tissue that acts as a pacemaker by producing a contractile signal at regular intervals
- in the wall of the right atrium
82
What are the steps involved in the propagation of cardiac action potentials through the conduction system?
1. Sinoatrial (SA) node
2. Atrioventricular (AV) node
3. Atrioventricular (AV) bundle
4. Right and left bundle branches
5. Purkinje fibers
83
How do action potentials propagate through the sinoatrial (SA) node?
- when the pacemaker potential reaches threshold, it triggers an action potential
- action potential at SA node propagates throughout both atria via gap junctions
- following the action potential, the two atria contract at the same time
84
How do action potentials propagate through the atrioventricular (AV) node?
- at the AV node, the action potential slows considerably
| - this delay provides time for the atria to empty their blood into the ventricles
85
What is special about the action potential propagation at the atrioventricular (AV) bundle?
Only site where action potentials can conduct from the atria to the ventricles
86
What happens to the action potential at the right and left bundles?
The bundle branches extend through the interventricular septum toward the apex of the heart
87
What happens to the action potential when it reaches the Purkinje fibers?
Purkinje fibers rapidly conduct the action potential from the apex to the remainder of the ventricular myocardium
- the ventricles contract, pushing blood upwards
88
What acts as the natural pacemaker of the heart?
SA node
- do not have a stable resting potential
* - nerve impulses and hormones modify the timing and strength of each heartbeat, BUT they do not establish the fundamental rhythm
89
What is an artificial pacemaker?
A device that sends out small electrical currents to stimulate the heart to contract
- consists of a battery and an impulse generator
90
What are the three steps involved in how an action potential occurs in cardiac contraction fibres?
1. Depolarization
2. Plateau
3. Re-polarization
91
Which muscle fibres are the "working" contractile fibres?
Atrial and ventricular muscle fibres
92
Describe what is occurring during the depolarization stage in a ventricular contractile fibre action potential.
Rapid depolarization due to Na+ inflow when voltage-gated "fast" Na+ channels open
- resting membrane potential of -90mV
93
Describe what is occurring during the plateau stage in a ventricular contractile fibre action potential.
Plateau (maintained depolarization) is due to Ca+2 inflow when voltage-gated "slow" Ca+2 channels open and K+ outflow when some K+ channels open
- lasts about 0.25 secs
- membrane potential just above 0mV
94
Describe what is occurring during the re-polarization stage in a ventricular contractile fibre action potential.
Repolarization due to closure of Ca+2 channels and K+ outflow when additional voltage-gated K+ channels open
- outflow of K+ restores the negative resting membrane potential (-90mV)
95
What is the refractory period?
Time interval during which a second contraction cannot be triggered
- lasts longer in cardiac muscle than the contraction itself
96
Why can tetanus never occur in cardiac muscle?
Tetanus (maintained contraction) would cause blood flow to cease
- atria and ventricles depend on alternation contraction
- it is prevented by the long refractory period of cardiac muscle
97
What is an electrocardiogram?
| ECG or EKG
A composite record of action potentials produced by all the heart muscle fibres during each heartbeat
98
What is an electrocardiograph?
The instrument used record the changes in a ECG
99
What are the 4 things that can be determined by an ECG or EKG?
1. If the conducting pathway is abnormal
2. If the heart is enlarged
3. If certain regions of the heart are damaged
4. Cause of chest pain
100
What are the three waves that appear with each heartbeat?
1. P wave
2. QRS complex
3. T wave
101
What is the P wave?
First wave
| - small upward deflection on the ECG
102
What does the P wave represent?
Represents atrial depolatization
| - spreads from the SA node through contractile fibres in both atria
103
What is the QRS complex?
Second wave
| - begins as a downward deflection, continues as a large, upright, triangular wave and ends as a downward wave
104
What does the QRS complex represent?
Represents the rapid ventricular depolarization
| - as the action potential spreads through ventricular contractile fibres
105
What is the T wave?
Third wave
| - dome-shaped upward deflection
106
What does the T wave represent?
Represents ventricular re-polarization
| - occurs just as the ventricles are starting to relax
107
What are the 6 steps in a ECG wave?
1. Depolarization of atrial contractile fibers produces P wave
2. Atrial systole (contraction)
3. Depolarization of ventricular contractile fibres produces QRS complex
4. Ventricular systole (contraction)
5. Repolarization of ventricular contractile fibres producdes T wave
6. Ventricular diastole (relaxation)
* page 778
108
What does systole refer to?
Refers to the phase of contraction
109
What does diastole refer to?
Refers to the phase of relaxation
110
What does a cardiac cycle include?
All the events associated with one heartbeat
- systole and diastole of the atria
- systole and diastole of the ventricles
111
What occurs during atrial systole?
Atria are contracting (atrial systole)
| Ventricles are relaxed (ventricular diastole)
112
What are the 4 steps involved in atrial systole?
1. Depolarization of the SA node causes atrial depolarization (P wave)
2. Atrial systole - atria contract, force blood through the open AV valves into the ventricles
3. Atrial systole contributes final 25mL of blood to each ventricle
- end of atrial systole is also the end of ventricular diastole
4. QRS complex marks the onset of ventricular depolarization
113
What is the end-diastolic volume (EDV)?
The blood volume at the end of diastole (relaxation period)
| - about 130mL
114
What occurs during ventricular systole?
Ventricles are contracting (ventricular systole)
| Atria are relaxed (atrial diastole)
115
What are the 4 steps involved in ventricular systole?
5. Ventricular depolarization causes ventricular systole
- pressure rises in the ventricles, AV valves are forced shut
6. Continued contraction of the ventricles causes pressure to increase sharply
- SL valves open - ventricular ejection occurs
7. Left ventricles ejects 70 mL into aorta, Right ventricles ejects about 70 mL into pulmonary trunk
8. T wave marks the onset of ventricular repolarization
116
What happens during isovolumetric contraction?
For about 0.05 seconds, both the SL and AV valves are closed
| - all four valves are closed, so ventricular volume remains the same
117
When does isovolumetric contraction occur?
During ventricular systole
| - as ventricular systole begins, pressure rises inside the ventricles and pushes the AV valves shut
118
What is ventricular ejection?
The period when the SL valves are open
| - blood is ejected from the heart
119
What is the end-systolic volume (ESV)?
The volume of blood in a ventricle at the end of contraction (systole) and the beginning of filling (diastole)
- the lowest volume of blood in the ventricle at any point in the cardiac cycle.
- about 60 mL
120
What is the stroke volume?
Volume ejected per beat from each ventricle
| - approx. 70mL
121
What is the formula for calculating stroke volume?
SV = EDV - ESV
| Stroke Volume = End-diastolic volume - End-systolic volume
122
What happens during the relaxation period?
Both the atria and ventricles are relaxed
| - as the heart beats faster and faster, relaxation period becomes shorter and shorter
123
What happens during ventricular diastole?
Ventricles relax
- pressure within the chambers fall
- blood in the aorta and pulmonary trunk begins to flow backwards toward the regions of lower pressure in the ventricles
124
What happens during isovolumetric relaxation?
During ventricular diastole, after the SL valves close there is a brief interval when ventricular blood volume does not change
- all 4 valves are closed
125
When does ventricular filling occur?
As the ventricles continue to relax, the pressure falls quickly
- ventricular pressure drops below atrial pressure
- AV valves open
- ventricular filling begins
126
How many heart sounds are there?
| How many can be heard with a stethoscope?
During each cardiac cycle there are 4 heart sounds
| - only S1 and S2 can be heard
127
Describe S1.
| When does it occur?
Lubb sound
- louder and longer than S2
- caused by blood turbulence associated with the closure of the AV valves soon after ventricular systole begins
128
Describe S2.
| When does it occur?
Dupp sound
| - caused by blood turbulence associated with closure of the SL valves at the beginning of ventricular diastole
129
What are S3 and S4 due to?
S3 - blood turbulence during rapid ventricular filling
| S4 - blood turbulence during atrial systole
130
What is a heart murmur?
Abnormal sound
- consists of clicking, rushing or gurgling
- heard before, between or after normal heart sounds
131
Cardiac cycle relating to pressure changes.
| See page 780
Review diagram on page 780.
132
What is cardiac output (CO)?
The volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute
133
What is the formula for calculating cardiac output (C0)?
Cardiac output = stroke volume x heart rate
| CO (mL/min) = SV (mL/beat) x HR (beats/min)
134
What is the cardiac reserve?
The difference between a person's maximum cardiac output and cardiac output at rest
- typically 4-5x the resting value
135
What 3 factors regulate stroke volume and ensure that the L and R ventricles pump equal volumes of blood?
1. Pre-load - degree of stretch on the heart before it contracts
2. Contractility - forcefulness of contraction of individual ventricular muscle fibres
3. After-load - pressure that must be exceeded before ejection of blood from the ventricles can occur
136
A greater pre-load (stretch) on cardiac muscle increases what?
The force of contraction
137
What is the Frank-Starling law of the heart?
Equalizes the output of the R and L ventricles
| - keeps the same volume of blood flowing to both systemic and pulmonary circulations
138
What 2 factors determine EDV (end-diastolic volume)?
1. Duration of ventricular diastole
| 2. Venous return
139
What is venous return?
The volume of blood returning to the right ventricle
140
What is contractility?
The strength of contraction at any given preload
141
What are positive inotropic agents?
Substances that increase contractility
| - promote inflow of Ca+2, strengthens the force of the next contraction
142
What are negative inotropic agents?
Substances the decrease contractility
| - increased K+ levels
143
What happens to the duration of diastole as the heart rate increases?
Diastole is shorter; smaller EDV
| - ventricles may contract before adequately filled
144
When does ejection of blood from the heart begin?
When pressure in the R ventricle exceeds the pressure in the pulmonary trunk and when the pressure in the L ventricle exceeds the pressure of the aorta
145
What is the after-load?
The pressure that must be overcome before a semilunar valve can open
146
What happens to stroke volume if there is an increase in after-load?
Stroke volume decreases
| - more blood remains in the ventricles at the end of systole
147
What condition can increase after-load?
Hypertension (elevated blood pressure)
148
Where is the cardiovascular center?
| What does it do?
In the medulla oblongata
| - nervous system regulation of the heart
149
What are the main receptors that send information to the cardiovascular center?
1. Proprioceptors
2. Chemoreceptors
3. Baroreceptors
150
What do proprioceptors monitor?
Monitor the position of the limbs and muscles
| - send nerve impulses at an increased frequency during activity
151
What do chemoreceptors monitor?
Changes in the blood
152
What do baroreceptors montior?
The stretching of major arteries and veins caused by the pressure of blood flowing through them
153
What do sympathetic cardiac accelerator nerves trigger?
The release of norepinephrine
| - binds to beta 1 receptors on cardiac muscle fibres
154
Where do the neurons for the sympathetic cardiac accelerator nerves extend from and to?
Sympathetic neurons extend from the medulla oblongata into the spinal cord
- from thoracic region of spinal cord into the SA node, AV node and most portions of the myocardium
155
What happens after the sympathetic cardiac accelerator nerves release norepinephrine?
1. SA and AV nodes, norepinephrine speeds the rate of spontaneous depolarization (heart rate increases)
2. Artria and ventricles, norepinephrine enchances Ca+2 entry (increases contractility, increased stroke volume)
156
How do parasympathetic nerve impulses reach the heart?
Right and left vagus (X) nerves
157
What do vagus (X) nerves release?
| What happens after that release?
Acetylcholine
| - decreases the heart rate by slowing the rate of spontaneous depolarization in autorhythmic fibres
158
What are the major hormones that affect the heart?
1. Epinephrine and norepinephrine - increase heart rate and contractility
2. Thyroid hormones - enhance cardiac contractility and increase heart rate
159
What is tachycardia?
An elevated resting heart rate
| - caused by excessive thyroid hormone release (hyperthyroidism)
160
What are the three major ions that affect the ability of the heart to contract?
1. K+
2. Ca+2
3. Na+
- high levels of K+ or Na+ decrease heart rate and contractility
- Na+ blocks Ca+2, decreasing the force of contraction
- Ca+2 speeds the heart rate and strengthens the heartbeat
161
What are the other major factors that influence the resting heart rate?
Age, gender, physical fitness, body temperature
162
What is bradycardia?
A resting heart rate under 50 beats/minute
- beneficial effect of endurance type training, b/c a slowly beating heart is more energy efficient than one that beats more rapidly
163
What is arteriosclerosis?
A thickening of the walls of arteries and loss of elasticity
164
What is atherosclerosis?
A form of arteriosclerosis
| - progressive disease characterized by the formation of lesions in the walls of large and medium-sized arteries
165
What is ventricular fibrillation (VF or V-fib)?
Most deadly arrhythmia
- contractions of the ventricular fibres are completely asynchronous so that the ventricles quiver instead of contract
- ventricular pumping stops
- blood ejection ceases and circulatory failure and death occur unless there is medical interventrion
166
What is cardiac arrest?
Cessation of an effective heartbeat
| - heart may be completely stopped or in V-fib
167
What is a heart palpitation?
A fluttering of the heart or an abnormal rate or rhythm of the heart
- individual is aware
