Week 1 - General Principles of the Cardiovascular System Flashcards
1
Q
What defines the superior boundary of the thoracic cavity?
A
The thoracic inlet is defined by the first thoracic vertebra, the first ribs, and the upper margin of the manubrium.
2
Q
What forms the inferior boundary of the thoracic cavity?
A
The diaphragm forms a dome-shaped muscular partition between the thoracic and abdominal cavities.
3
Q
What is the composition of the anterior chest wall?
A
The anterior chest wall comprises the sternum and costal cartilages.
4
Q
What forms the lateral walls of the thoracic cavity?
A
The lateral walls are formed by the ribs and intercostal muscles.
5
Q
What primarily constitutes the posterior wall of the thoracic cavity?
A
The posterior wall is primarily the vertebral column and associated musculature.
6
Q
How many lobes does the right lung have?
A
The right lung is divided into three lobes: superior, middle, and inferior.
7
Q
How many lobes does the left lung have?
A
The left lung is divided into two lobes: superior and inferior.
8
Q
What is the function of alveolar sacs in the lungs?
A
Alveolar sacs are where gas exchange occurs.
9
Q
What are the visceral and parietal pleura?
A
The visceral pleura closely adheres to the lung surface; the parietal pleura lines the inner chest wall, diaphragm, and mediastinum.
10
Q
What is the role of pleural fluid?
A
Pleural fluid minimizes friction during respiratory movements.
11
Q
Where is the heart located in the thoracic cavity?
A
The heart is centrally located in the mediastinum.
12
Q
What encloses the heart?
A
The heart is enclosed by a double-layered pericardial sac.
13
Q
What are the major components of the great vessels?
A
The great vessels include the aorta, pulmonary trunk and its branches, the superior and inferior vena cava, and the pulmonary veins.
14
Q
What is the function of the esophagus?
A
The esophagus is a muscular tube for food passage.
15
Q
What is the function of the trachea?
A
The trachea is a rigid cartilaginous tube for air conduction.
16
Q
What is the role of the thymus in the thoracic cavity?
A
The thymus is involved in T-cell maturation and immune regulation.
17
Q
What functions do the phrenic and vagus nerves serve?
A
The phrenic and vagus nerves provide motor, sensory, and autonomic input.
18
Q
What is the thoracic duct’s role?
A
The thoracic duct plays key roles in immune surveillance and fluid balance.
19
Q
What is the extent of the Superior Mediastinum?
A
From the thoracic inlet to the sternal angle (Angle of Louis).
20
Q
What are the contents of the Superior Mediastinum?
A
- Thymus
- Trachea
- Esophagus
- Portions of the aortic arch
- Major branches (brachiocephalic vessels, left common carotid, left subclavian arteries)
- Important neural elements (vagus, phrenic, sympathetic chains)
21
Q
What are the three regions of the Inferior Mediastinum?
A
- Anterior Mediastinum
- Middle Mediastinum
- Posterior Mediastinum
22
Q
Where is the Anterior Mediastinum located and what does it contain?
A
Lies between the sternum and the pericardium; contains loose connective tissue, small lymph nodes, and residual thymic tissue.
23
Q
What dominates the Middle Mediastinum?
A
The heart within its pericardial sac.
24
Q
What does the Middle Mediastinum include aside from the heart?
A
Origins of the great vessels and proximal portions of the tracheobronchial tree.
25
What is located in the Posterior Mediastinum?
* Descending aorta
* Esophagus
* Thoracic duct
* Azygos system of veins
* Sympathetic chain
26
True or False: Detailed knowledge of mediastinal compartments is important for interpreting imaging studies.
True
27
Fill in the blank: The _______ Mediastinum lies between the sternum and the pericardium.
[Anterior Mediastinum]
28
What is the significance of understanding the mediastinal anatomy?
Vital for planning surgical interventions for mediastinal masses or infections.
29
What is the Fibrous Pericardium?
A dense, inelastic outer layer that anchors the heart to surrounding mediastinal structures and protects the heart from over-distension.
## Footnote
It connects to the diaphragm and sternum.
30
What are the two layers of the Serous Pericardium?
* Parietal Layer
* Visceral Layer (Epicardium)
## Footnote
The parietal layer lines the inner surface of the fibrous pericardium, while the visceral layer adheres directly to the heart surface.
31
What is the pericardial cavity?
The space between the parietal and visceral layers of the serous pericardium that contains a thin film of serous fluid.
## Footnote
This fluid facilitates frictionless movement during the cardiac cycle.
32
What primarily supplies blood to the pericardium?
Primarily from the pericardiacophrenic arteries and supplemented by small branches from the bronchial arteries.
## Footnote
The pericardiacophrenic arteries are branches of the internal thoracic arteries.
33
Which nerves provide sensory innervation to the pericardium?
The phrenic nerves, originating from C3–C5.
## Footnote
Irritation of these nerves may refer pain to the shoulder region.
34
What is one of the functions of the pericardium related to mechanical protection?
Minimizes friction and provides a stable mechanical environment for cardiac motion.
## Footnote
This function is crucial for the heart's proper functioning during the cardiac cycle.
35
How does the pericardium provide structural support?
Limits excessive dilation of the heart, preserving optimal geometry for efficient contraction.
## Footnote
This helps maintain the heart's shape during varying pressures.
36
What barrier role does the pericardium play?
Helps contain infections and inflammation within the pericardial space.
## Footnote
This is vital for protecting the heart from surrounding infections.
37
What are the functions of the atria?
Thin-walled chambers responsible for receiving blood
## Footnote
The right atrium collects systemic venous return; the left atrium receives oxygenated blood from the pulmonary veins.
38
What is the role of the ventricles?
Thick-walled chambers that generate the force required to propel blood
## Footnote
The right ventricle pumps blood into the low-pressure pulmonary circuit; the left ventricle ejects blood into the high-pressure systemic circulation.
39
What do the interatrial and interventricular septa do?
Maintain separation between oxygenated and deoxygenated blood
40
What is the function of the valvular apparatus?
Ensures unidirectional blood flow
## Footnote
Includes the atrioventricular (mitral and tricuspid) and semilunar (aortic and pulmonary) valves.
41
What is the function of the aorta?
Distributes oxygenated blood throughout the body
## Footnote
Emerges from the left ventricle.
42
What does the pulmonary trunk do?
Originates from the right ventricle and bifurcates into the pulmonary arteries
## Footnote
Delivers blood to the lungs.
43
What do the superior and inferior vena cavae do?
Return deoxygenated blood to the right atrium
44
What do the pulmonary veins do?
Return oxygenated blood to the left atrium
45
What does the Left Coronary Artery (LCA) typically divide into?
Left anterior descending (LAD) and circumflex (LCx) arteries
46
What areas does the Right Coronary Artery (RCA) supply?
Supplies the right atrium, right ventricle, and portions of the conduction system
## Footnote
Includes the SA and AV nodes in most individuals.
47
Describe the sequence of unidirectional blood flow.
Blood moves from systemic veins to the right atrium, to the right ventricle, through the pulmonary circulation, to the left atrium, to the left ventricle, and back into systemic circulation.
48
True or False: The right heart operates under higher pressure than the left heart.
False
## Footnote
The right heart operates under lower pressure with thinner walls.
49
What characterizes the myocardium of the left heart?
Thick myocardium to generate high pressures needed for systemic circulation
50
Where does the heart lie anatomically?
The heart lies within the middle mediastinum
51
What forms the right border of the heart?
The right atrium
52
What forms the left border of the heart?
The left ventricle
53
In which intercostal space is the apex of the heart typically found?
The left fifth intercostal space
54
What line is used to locate the apex of the heart?
The midclavicular line
55
Why is knowledge of the spatial arrangement of the heart's chambers important?
It is crucial for interpreting imaging studies and physical examination findings
56
Fill in the blank: The heart is oriented _______.
obliquely
57
What is the origin of the Aorta?
Arises from the left ventricle
## Footnote
The aorta's arch gives off branches that supply the head, neck, and upper limbs.
58
Where does the Pulmonary Trunk emanate from?
Right ventricle
## Footnote
The pulmonary trunk bifurcates into left and right pulmonary arteries that serve the lungs.
59
What does the superior vena cava (SVC) collect blood from?
Upper body
## Footnote
The inferior vena cava (IVC) traverses the diaphragm to empty into the right atrium.
60
How many pulmonary veins are typically present?
Four
## Footnote
Pulmonary veins return oxygenated blood from the lungs to the left atrium via a posterior approach.
61
Why is a detailed understanding of vascular landmarks essential?
During invasive procedures and in the interpretation of radiologic studies
## Footnote
Examples include catheterization and bypass surgery.
62
Fill in the blank: The _______ collects blood from the upper body.
superior vena cava
63
True or False: The pulmonary trunk bifurcates into three arteries.
False
## Footnote
The pulmonary trunk bifurcates into left and right pulmonary arteries.
64
What is the function of the aorta?
Supplies the head, neck, and upper limbs
## Footnote
It does this through branches that arise from its arch.
65
Fill in the blank: The inferior vena cava empties into the _______.
right atrium
66
Where is the apex beat typically palpated?
At the left fifth intercostal space
## Footnote
The location and strength of the apex beat can indicate left ventricular hypertrophy or dilation.
67
What areas are included in the precordial region?
Areas corresponding to the right ventricle and the left ventricle at the apex
## Footnote
The right ventricle is adjacent to the left lower sternal border.
68
Which peripheral pulses are assessed during examination?
Carotid, radial, and femoral pulses
## Footnote
Assessment provides information on systemic circulation and arterial compliance.
69
Why is careful palpation important in clinical integration?
It is essential for detecting abnormalities and assessing overall circulatory status
## Footnote
Abnormalities may include displaced or hyperdynamic apex beats.
70
Fill in the blank: The apex beat can indicate _______.
left ventricular hypertrophy or dilation
71
What is the location of the Aortic Area for auscultation?
The right second intercostal space at the sternal border
72
What does the Aortic Area evaluate?
Aortic valve function
73
Where is the Pulmonic Area located?
The left second intercostal space at the sternal border
74
What is assessed at the Pulmonic Area?
The pulmonary valve
75
Where can the Tricuspid Area be found?
The left lower sternal border (around the fourth intercostal space)
76
What is the purpose of auscultating the Tricuspid Area?
Listening to the tricuspid valve
77
What is the location of the Mitral Area (Apex)?
The left fifth intercostal space at the midclavicular line
78
What is the significance of the Mitral Area?
Key for mitral valve evaluation
79
What is the clinical significance of accurate auscultation?
Aids in diagnosing murmurs, extra heart sounds, and other pathologic findings
80
What is the first phase of the cardiac cycle?
Diastole
## Footnote
Diastole includes early diastole, mid-diastole, and late diastole (atrial systole).
81
What occurs during early diastole?
Rapid ventricular relaxation and steep decline in intraventricular pressure, allowing AV valves to open
## Footnote
This phase is crucial for initiating the filling of the ventricles.
82
What happens during mid-diastole?
Passive filling of the ventricles as blood flows from the atria
## Footnote
This phase continues to contribute to ventricular filling.
83
What is the role of atrial contraction in late diastole?
Tops off ventricular filling, contributing to end-diastolic volume
## Footnote
This phase ensures that the ventricles are adequately filled before systole.
84
What is isovolumetric contraction?
Ventricles contract with no change in volume until intraventricular pressure exceeds that in the aorta or pulmonary artery
## Footnote
This occurs after AV valve closure.
85
What occurs during the ejection phase of ventricular systole?
Blood is forcefully ejected into the arterial system
## Footnote
This phase begins once the semilunar valves open.
86
What is isovolumetric relaxation?
Ventricular relaxation begins with all valves closed, leading to a rapid fall in pressure
## Footnote
This sets the stage for the next cardiac cycle.
87
Why is understanding the phases of the cardiac cycle important in clinical practice?
Essential for interpreting pressure-volume loops and diagnosing dysfunction such as diastolic heart failure
## Footnote
Knowledge of these phases aids in patient assessment.
88
What determines preload in the cardiac cycle?
End-diastolic volume (EDV)
## Footnote
Preload stretches myocardial fibers according to the Frank-Starling law.
89
What is the Frank-Starling law?
The relationship between preload and stroke volume, indicating that increased preload leads to increased stroke volume
## Footnote
This principle is fundamental to cardiac function.
90
What do the opening and closing of the AV and semilunar valves ensure?
Efficient conversion of volume changes into pressure generation and unidirectional blood flow
## Footnote
This coordination is crucial for effective heart function.
91
What factors affect stroke volume?
Variations in venous return and end-diastolic volume (EDV)
## Footnote
Stroke volume directly influences cardiac output and systemic perfusion.
92
What are key parameters routinely assessed in clinical practice?
Stroke Volume (SV), End-Diastolic Volume (EDV), Ejection Fraction (EF)
## Footnote
These parameters are critical for evaluating heart function.
93
What is the definition of stroke volume (SV)?
The volume of blood ejected per heartbeat
## Footnote
SV is an important measure of cardiac efficiency.
94
What does ejection fraction (EF) represent?
The percentage of EDV expelled during systole
## Footnote
EF is a crucial measure of ventricular performance.
95
What components are illustrated in Wigger’s diagram?
Pressure curves, volume curves, ECG tracing, heart sounds (phonocardiogram)
## Footnote
These components correlate electrical activity with mechanical function.
96
What do the pressure curves in Wigger’s diagram show?
Temporal relationship between left ventricular pressure, aortic pressure, and atrial pressures
## Footnote
This helps in understanding cardiac dynamics.
97
What do the volume curves in Wigger’s diagram illustrate?
Changes in ventricular volume corresponding to phases of filling and ejection
## Footnote
This provides insight into the heart's functional phases.
98
What is the significance of the ECG tracing in Wigger’s diagram?
Provides a temporal correlation of electrical activity with mechanical events
## Footnote
Correlates the heart's electrical and mechanical functions.
99
What do heart sounds (phonocardiogram) visualize?
Timing of S1 and S2 in relation to electrical and hemodynamic events
## Footnote
This aids in diagnosing various cardiac conditions.
100
True or False: Systole is the relaxation phase of the cardiac cycle.
False
## Footnote
Systole is the contraction phase, while diastole is the relaxation phase.
101
What is the outer layer of the heart called?
Epicardium
## Footnote
The epicardium is continuous with the visceral pericardium and plays a role in protecting the heart and forming coronary vessels.
102
What is the main component of the myocardium proper?
Densely packed cardiac muscle fibers
## Footnote
These fibers are arranged in a complex spiral pattern that facilitates effective blood ejection.
103
What is the function of the endocardium?
Minimizes friction and modulates electrical activity
## Footnote
The endocardium is the smooth inner lining of the heart.
104
How does fiber orientation in the myocardium affect heart function?
Supports efficient contraction and relaxation
## Footnote
Disruption can impair both mechanical and electrical function, as seen in hypertrophic cardiomyopathy.
105
What morphological features characterize cardiomyocytes?
Long, striated cells with a central nucleus and organized sarcomeres
## Footnote
Sarcomeres contain A-bands, I-bands, and Z-discs, which are essential for contraction.
106
What are intercalated discs?
Specialized junctions enabling electrical coupling and mechanical adhesion
## Footnote
They contain gap junctions, desmosomes, and adherens junctions.
107
What is the metabolic profile of cardiomyocytes?
Rich in mitochondria with high oxidative capacity
## Footnote
This supports their continuous energy demand.
108
What can alterations in calcium handling or sarcomeric protein function cause?
Contractile dysfunction
## Footnote
This is observed in various cardiomyopathies.
109
What is cardiac output (CO)?
The product of heart rate (HR) and stroke volume (SV)
## Footnote
CO is critical for maintaining tissue perfusion.
110
What determines stroke volume?
Preload, afterload, and contractility
## Footnote
Preload is the initial stretch of myocardial fibers, afterload is the resistance against blood ejection, and contractility is the myocardium's intrinsic ability to contract.
111
What is preload?
End-diastolic volume (EDV)
## Footnote
It determines the initial stretch of the myocardial fibers.
112
What is afterload?
The resistance against which the ventricles must eject blood
## Footnote
It impacts stroke volume.
113
What is contractility?
The intrinsic ability of the myocardium to contract
## Footnote
It is modulated by sympathetic stimulation.
114
What factors regulate preload?
Blood volume, venous tone, respiratory and skeletal muscle pumps, postural effects
## Footnote
These factors affect venous return and preload.
115
What effect does blood volume have on venous return?
Higher circulating volume increases venous pressure
## Footnote
This enhances venous return.
116
How does sympathetic-mediated vasoconstriction affect venous return?
Decreases venous capacitance
## Footnote
This augments venous return.
117
What role do respiratory and skeletal muscle pumps play?
Aid in propelling blood towards the heart
## Footnote
Negative intrathoracic pressure during inspiration and rhythmic muscle contraction contribute to this.
118
How does posture affect venous return?
Standing may reduce venous return compared to a supine position
## Footnote
Gravity influences venous pooling.
119
What can impairments in preload factors lead to?
Inadequate preload
## Footnote
This is critical in conditions such as hypovolemia and congestive heart failure.
120
What are the components of the Mitral Valve?
Anterior and posterior leaflet, tethered by chordae tendineae to papillary muscles
## Footnote
Papillary muscles are vital for preventing prolapse during ventricular contraction.
121
What are the components of the Tricuspid Valve?
Three leaflets: anterior, posterior, and septal, supported by chordae tendineae and papillary muscles
## Footnote
Similar to the Mitral Valve in structure and function.
122
What is the histological composition of Atrioventricular Valves?
A robust core of collagen and elastin, covered by an endocardial lining
## Footnote
This structure provides strength and flexibility while reducing friction.
123
What is the structure of Semilunar Valves?
Typically have three cusps, with a fibrous framework interlaced with elastic fibers and covered by a thin endothelial layer
## Footnote
Designed to withstand high-pressure environments.
124
What can structural defects in heart valves lead to?
Regurgitation or stenosis, impacting cardiac output
## Footnote
Such defects can be degenerative or congenital.
125
How do Atrioventricular Valves operate during the cardiac cycle?
Open during ventricular diastole and close rapidly during systole
## Footnote
This prevents retrograde flow of blood.
126
What is the function of Semilunar Valves during systole?
Open when ventricular pressure exceeds arterial pressure
## Footnote
They close promptly during diastole to maintain forward flow.
127
What heart sounds are generated by valve motion?
First (S1) and second (S2) heart sounds
## Footnote
Precise timing of valve motion is essential for efficient hemodynamics.
128
What produces the S1 heart sound?
Closure of the AV valves at the onset of ventricular systole
## Footnote
Its intensity and splitting provide diagnostic clues.
129
What produces the S2 heart sound?
Closure of the semilunar valves at the beginning of diastole
## Footnote
Variations in S2 can indicate abnormalities in ventricular conduction or valve pathology.
130
What does the S3 heart sound indicate?
May be present in normal young individuals or signify volume overload in pathologic states
## Footnote
It is not always pathological.
131
What does the S4 heart sound typically indicate?
A stiff, non-compliant ventricle, as seen in left ventricular hypertrophy
## Footnote
It suggests underlying cardiac conditions.
132
What are the consequences of regurgitation?
Inadequate closure of a valve leading to retrograde blood flow, volume overload, chamber dilation, and chronic heart failure
## Footnote
This condition can severely affect cardiac function.
133
What are the effects of stenosis on the heart?
Narrowing of the valve orifice increases the workload on the ventricle, leading to hypertrophy and potentially ischemia
## Footnote
This condition can lead to significant hemodynamic compromise.
134
Fill in the blank: Aberrant valve function can lead to significant clinical _______.
sequelae
## Footnote
This can occur due to conditions like rheumatic heart disease or calcific degeneration.
135
What is the clinical utility of auscultation of heart sounds?
A key non-invasive diagnostic tool in the evaluation of cardiac function
## Footnote
It helps in assessing valve function and overall heart health.
136
What is the primary pacemaker of the heart?
Sinoatrial (SA) Node
## Footnote
Located in the right atrial wall near the SVC junction, it generates spontaneous action potentials.
137
Where is the Atrioventricular (AV) Node located?
In the interatrial septum
## Footnote
It delays conduction to allow for complete ventricular filling.
138
What structure emerges from the AV node and bifurcates into right and left bundle branches?
Bundle of His
## Footnote
It rapidly conducts impulses down the interventricular septum.
139
What are Purkinje Fibers responsible for?
Distributing the electrical impulse throughout the ventricular myocardium
## Footnote
This ensures synchronous contraction.
140
What can disruptions in the cardiac conduction pathway lead to?
Arrhythmias or conduction blocks
## Footnote
Often necessitating clinical intervention such as pacemaker implantation.
141
How does the electrical impulse spread across the atria?
Rapidly via gap junctions
## Footnote
The impulse originates in the SA node.
142
What is the purpose of the AV Nodal Delay?
To ensure complete atrial contraction and optimize ventricular filling
## Footnote
This is critical for effective hemodynamics.
143
What leads to near-simultaneous ventricular activation?
Rapid conduction through bundle branches and Purkinje fibers
## Footnote
This follows the passage through the Bundle of His.
144
What does the timing of electrical activity events ensure?
Coordination between electrical and mechanical cardiac activity
## Footnote
Essential for maintaining effective hemodynamics.
145
What is the function of the SA Node?
Sets the intrinsic rate of the heart
## Footnote
It generates spontaneous action potentials.
146
What role does the AV Node play in cardiac function?
Acts as a critical delay junction
## Footnote
Ensures that ventricular filling is complete before contraction begins.
147
What is the role of Purkinje Fibers in the heart?
Ensures efficient propagation of the contraction wave throughout the ventricles
## Footnote
Their rapid conduction is crucial for effective heart function.
148
What abnormalities can occur in the SA Node, AV Node, or Purkinje Fibers?
Bradyarrhythmias, tachyarrhythmias, or conduction blocks
## Footnote
These influence overall cardiac performance.
149
What is the resting membrane potential in ventricular cells?
Approximately –90 mV
## Footnote
Maintained predominantly by potassium permeability.
150
What initiates the rapid depolarization phase (Phase 0) in cardiac myocytes?
Opening of voltage-gated sodium channels
## Footnote
Resulting in a swift influx of Na⁺.
151
What characterizes Phase 1 of the action potential?
Transient outward potassium currents (Ito)
## Footnote
Causes a brief, partial repolarization.
152
What occurs during the plateau phase (Phase 2) of the action potential?
Influx of Ca²⁺ via L-type calcium channels balanced by K⁺ efflux
## Footnote
Sustains a plateau essential for contraction.
153
What is the main event in Phase 3 of the action potential?
Enhanced K⁺ efflux restores the membrane potential
## Footnote
Returning it to its resting state.
154
What is the purpose of refractory periods in cardiac myocytes?
Prevent premature re-excitation
## Footnote
Ensures the rhythmicity of the heartbeat.
155
How do alterations in action potential phases affect cardiac health?
Central to many cardiac pathologies, including arrhythmias
## Footnote
Particularly in calcium dynamics.
156
What is the role of calcium in electromechanical coupling?
Triggers a larger release of calcium from the sarcoplasmic reticulum
## Footnote
Initiates actin–myosin cross-bridge formation.
157
What happens during repolarization in cardiac muscle?
Calcium is resequestered and muscle relaxes
## Footnote
Allowing the cycle to repeat.
158
What can disruptions in calcium handling lead to?
Contractile dysfunctions such as heart failure or ischemia
## Footnote
Clinical importance in cardiac health.
159
What initiates the calcium-induced calcium release?
Initial Ca²⁺ influx triggers ryanodine receptors
## Footnote
On the sarcoplasmic reticulum, releasing more calcium.
160
What is the sliding filament mechanism?
Interaction of elevated intracellular calcium with contractile proteins
## Footnote
Produces contraction.
161
What terminates muscle contraction?
Calcium removal via reuptake and extrusion
## Footnote
Leading to muscle relaxation.
162
What is a distinctive feature of the ventricular action potential?
Prolonged plateau phase
## Footnote
Ensures sufficient time for calcium influx.
163
How does ventricular contraction relate to calcium levels?
Highly sensitive to calcium levels
## Footnote
Making cells vulnerable to ion balance disturbances.
164
What prevents premature re-excitation in the heart?
The long action potential of the ventricular cells
## Footnote
Preserves coordinated contraction.
165
What characterizes the pacemaker action potential?
Spontaneous diastolic depolarization
## Footnote
Due to funny currents (If) and T-type calcium channels.
166
What is the state of the resting potential in pacemaker cells?
Absence of a stable resting potential
## Footnote
Continuously drifting towards threshold.
167
What underlies the heart's inherent rhythmicity?
Unique combination of ionic currents in pacemaker cells
## Footnote
Setting the pace for the conduction system.
168
What is a clinical consequence of dysfunction in ionic channels of pacemaker cells?
Can lead to bradyarrhythmias or tachyarrhythmias
## Footnote
Targeted for pharmacologic intervention.
169
What is the source of sympathetic innervation in the heart?
Thoracic spinal segments
## Footnote
Sympathetic fibers release noradrenaline to impact cardiac function.
170
What neurotransmitter is released by the vagus nerve?
Acetylcholine
## Footnote
This neurotransmitter slows heart rate and prolongs AV nodal conduction.
171
What is the effect of sympathetic innervation on pacemaker cells?
Increases the rate of depolarization
## Footnote
This results in shorter conduction times and enhanced myocardial contractility.
172
What does the dynamic balance between sympathetic and parasympathetic innervation allow?
Rapid adaptation to changing physiological demands
## Footnote
Examples include adjustments during exercise versus rest.
173
What can alterations in autonomic tone lead to?
Arrhythmias
## Footnote
This is a key focus in pharmacologic and device-based therapy.
174
What receptor does noradrenaline bind to in order to enhance pacemaker activity?
β₁-adrenergic receptors
## Footnote
This increases the slope of the pacemaker potential.
175
What are the effects of sympathetic activation on conduction velocity?
Increased conduction velocity and contractility
## Footnote
Enhances calcium influx in both pacemaker and contractile cells.
176
What can excessive sympathetic stimulation lead to?
Tachyarrhythmias
## Footnote
It can also exacerbate myocardial ischemia.
177
What is the effect of acetylcholine on heart rate?
Decreases heart rate
## Footnote
This is due to negative chronotropic effects via M2 receptors.
178
What is the dromotropic effect of acetylcholine?
Slows conduction through the AV node
## Footnote
This results in a prolonged AV delay.
179
What factors influence the cardiac conduction pathway?
Autonomic tone, electrolyte balance, ischemia/infarction, pharmacologic agents
## Footnote
These factors can alter action potential duration and conduction velocity.
180
What electrolytes are critical in modulating cardiac conduction?
K⁺, Ca²⁺, Mg²⁺
## Footnote
Abnormalities in these ions can predispose to arrhythmias.
181
What can damage to the conduction system from ischemic events result in?
Blocks or ectopic pacemaker activity
## Footnote
This affects the normal rhythm of the heart.
182
What types of drugs modify conduction properties in the heart?
Beta-blockers, calcium channel blockers, antiarrhythmic medications
## Footnote
These are essential tools in managing arrhythmias.
183
Fill in the blank: The net effect on the conduction system is determined by the balance between _______ and _______.
sympathetic; parasympathetic activity
184
True or False: Acetylcholine has a positive chronotropic effect on the heart.
False
## Footnote
Acetylcholine decreases heart rate.
