Cardiac Physiology Flashcards
1
Q
About _________ of the adult human body is fluid, mainly a water solution of ions and other substances.
A
50- 70%
2
Q
What ions make up extracellular fluid?
A
Na, Cl, HCO3, & nutrients: oxygen, glucose, fatty acids, amino acids
3
Q
What ions make up intracellular fluid?
A
K, Mg, Phosphate ions
4
Q
Although most of this fluid is inside the cells (intracellular), about _________ is in the spaces outside of the cells (extracellular)
A
one-third
5
Q
__________ potassium in the extracellular fluids causes the heart to become dilated and flaccid and slows the heart rate
A
Excess
6
Q
High potassium concentration in the extracellular fluids __________ the resting membrane potential in the cardiac muscle fibers.
A
decreases
7
Q
Large quantities of potassium also can ___________ of the cardiac impulse from the atria to the ventricles through the A-V bundle.
A
block conduction
8
Q
Potassium concentration to only 8 to 12 mEq/L - two to three times the normal value can cause
A
severe weakness of the heart, abnormal rhythm, and death.
9
Q
__________ calcium ions cause the heart to move toward spastic contraction.
A
Excess
10
Q
True or False: Deficiency of calcium ions causes cardiac weakness
A
True
11
Q
What are the three types of cardiac muscles?
A
Atrial, ventricular, and specialized excitatory and conductive muscle fibers
12
Q
Cell membrane that separates individual cardiac muscle cells
A
Intercalated discs
13
Q
Cell membranes fuses with one another to form permeable communication junctions that allow rapid diffusion of ions
A
Gap junctions
14
Q
Factors that HR is effected by: cardiac rhythm, autonomic efferent innovation, neural reflex mechanisms, hormonal influences (Extrinsic or Intrinsic)
A
Intrinsic
15
Q
Factors that HR is effected by: pharmaceuticals, recreational drugs, fear, hypo/hyperthermia (Extrinsic or Intrinsic)
A
Extrinsic
16
Q
True or false: When one cell undergoes an action potential (AP),
the AP spreads to all connecting cells
A
True
17
Q
What node is along the epicardial surface at the junction of the superior vena cava and right atrium that receives blood supply from the prominent central artery branch of the RCA
A
SA Node
18
Q
What type of cells make up the SA node?
A
P cells (pacemaker cells) and transitional cells
19
Q
What is the intrinsic rate of the SA node?
A
60-100 beats/min
20
Q
What is the speed of conduction for the SA node?
A
0.5 m/sec
21
Q
Lies in the atria and cells are composed of large nuclei and sparse myofibrils
A
Internodal tracts
22
Q
Anterior Internodal Tract is known as _________ and extends into the LA then travels through atrial septum to AV node
A
Bachman bundle
23
Q
Middle Internodal Tract is known as __________ and curves behind the SVC before descending to AV node
A
Wenckebach track
24
Q
Posterior Internodal Tract is known as ________ and continues along terminal crest to atrial septum to AV node
A
Thorel pathway
25
What node is located on the posterior aspect of the right atrium behind the tricuspid valve, near the opening of the coronary sinus?
AV node
26
True or False: Conduction delay does NOT allow time for the atria to empty blood into the ventricle
False: Conduction delay allows time for the atria to empty blood into the ventricle
27
What is the intrinsic rate of the AV node?
40- 60 beats/min
28
What is the conduction velocity for the AV node?
2 m/sec
29
There is a total conduction delay of ________ before excitatory signal reaches contracting muscle of the ventricles
0.16
30
Consists of the bundle branch and terminal branches that extends out towards the endocardium
Purkinje System
31
What is the intrinsic rate of the Purkinje system?
20- 40 beats/min
32
What is the conduction velocity for the Purkinje system?
4 m/sec
33
Innervates anterolateral wall of LV & anterior papillary muscle
Anterior Fascicles
34
Innervates lateral and posterior ventricular wall & posterior papillary muscle
Posterior Fascicles
35
Innervates lower ventricular septum & apical wall of LV
Septal Fascicles
36
What occurs in Phase 0 (Depolarization)
Fast sodium channels open
37
What occurs in Phase 1 (Initial Repolarization)
Fast sodium channels close
38
What occurs in Phase 2 (Plateau)
Calcium channels open and fast potassium channels close
39
What occurs in Phase 3 (Rapid Repolarization)
Calcium channels close and slow potassium channels open
40
What occurs in Phase 4 (Resting Membrane Potential)
RMP averages -80 to -90 millivolts
41
True or False: Cardiac muscle is a syncytium of many heart cells interconnected that when one cell becomes excited, the action potential spreads rapidly to all cardiac cells.
True
42
True or False: Efferent autonomic tone to the heart is initiated in the anterior (PNS) and posterior (SNS) hypothalamus and is modulated by the cardiac acceleration and cardiac slowing centers in the medulla prior to distribution.
True
43
What is chronotrophy?
Increased activity, increased HR
44
What is inotropy?
Increased myocardial contraction
45
What is dromotrophy?
Increased rate of AV node discharge
46
Greater distribution of the sympathetic nerves innervate the __________.
Ventricles
47
Where do cardioaccelerator fiber originate from and synapse at?
Fibers originate from cells in the intermediolateral columns of higher thoracic segment of the spinal cord (T1-T4) and synapse at 1st – 5th thoracic vertebral ganglia
47
Positive chronotropic, dromotropic, and inotropic
Beta 1 adrenergic receptors (Epinephrine)
48
True or False: Activation of parasympathetic nervous system results in mobilization of myocardial fat-free acids & glycogen for energy use by myocardial cells
False: activation of the SNS
49
Positive chronotropic effect
Beta 2 adrenergic receptors
50
Positive inotropic effect
Alpha 1 adrenergic receptors (Phenylephrine)
51
Where does the PNS originate?
Dorsal motor nucleus of the medulla
52
Maximum vagal nerve stimulation decreases contractility by ______%
30%
52
True or False: Increased parasympathetic tone increases HR
False: decreases HR
53
The release of acetylcholine decreases the rate of the sinus node. Weak to moderate can slow the rate to ________.
one half
54
Intense stimulation of the vagus nerve can fully inhibit the rhythmic excitatory signal transmission from the SA and AV nodes resulting in the ventricles ceasing to beat for 5 to 20 seconds. What is this called?
Ventricular escape
55
Stimulation of the vagus nerve increases the permeability of cardiac cell membranes resulting in _____________. The RMP becomes more negative _________mV.
hyperpolarization, -65 to -75
56
Where are baroreflexes located? They are not stimulated between ___ - ___mmHg and maximum response is _______mmHg
Carotid sinus and aortic arch; 0 to 50 and 180
57
Reflex initiated by stretch receptors located at specific points in the walls of several large systemic arteries (spray-type nerve endings)
Baroreceptor Reflex
58
True or False: Signals from the carotid baroreceptors are transmitted through small Hering’s nerves to the
glossopharyngeal nerves in the high neck and then to the nucleus tractus solitarius in the medullary area of the brain stem
True
59
What reflex have cells that are sensitive to low oxygen or elevated carbon dioxide & hydrogen ion levels? They stimulate nerve fibers that pass through Hering’s nerves & vagus nerve into the vasomotor center of the brain stem.
Chemoreceptor Reflex
60
Where are chemoreceptors located?
Carotid bodies (2) - bifurcation of each common carotid artery
Aortic bodies (3) – adjacent to the aorta
61
Humoral factors are also known as _____ and they influence HR independent of the SNS and PNS.
circulating catecholamines
62
Myocardial β1-adrenergic receptors can also be activated, and heart rate is increased by direct pharmacologic agonists such as:
1. Isoproterenol
2. Epinephrine
3. Agents that indirectly cause release of endogenous catecholamines (ephedrine)
4. Drugs that impair catecholamine metabolism or reuptake (cocaine)
63
Type of anesthesia that causes bradycardia and hypotension- inhibition of sympathetic ganglia, resulting in parasympathetic predominance
Suppression or Blockade (Regional Anesthesia)
63
Type of anesthesia that
1. Depresses SA node automaticity
2. Moderate effect on AV node (Junctional tachycardia under GA with anticholinergics)
3. Blocks influx of Calcium
Volatile anesthetics (Inhaled/Halogenated)
64
1. High concentrations depress conduction by binding to fast sodium channels
2. Depress the SA node
3. Bupivicaine is the most cardiotoxic (binds to fast sodium channels)
Local Anesthetics
65
1. Depress cardiac conduction
2. Increase AV conduction
3. Increase refractory period
4. Prolong duration of Purkinje fiber action potential
Opioids (Fentanyl and sufentanil)
66
What valves open during systole?
Semilunar (Pulmonic and aortic)
67
What valves close during systole?
AV valves (Tricuspid and mitral)
68
What valves open during diastole?
AV valves (Tricuspid and mitral)
69
What valves close during diastole?
Semilunar (Pulmonic and aortic)
70
What is the normal end-systolic volume?
50 mL
71
What percent of systole is rapid ejection and slow ejection?
70% rapid ejection (during the first third) and 30% slow ejection (during the remaining two thirds)
71
What is the normal end-diastolic volume?
120 mL
72
What are the four phases of ventricular function?
1. Ventricular filling
2. Isovolumic contraction
3. Ventricular ejection
4. Isovolumic relaxation
72
In what phase does the mitral valve open?
Ventricular filling
73
The amount of stretch in the ventricles of the heart at the end of diastole, before the next contraction. It represents the volume of blood in the ventricles at the end of diastole and is influenced by factors such as venous return and ventricular compliance.
Preload
73
The time between the closing of the mitral valve and the opening of the aortic valve is the ____________. This is where pressure builds, yet the blood does not leave the ventricle.
Isovolumic contraction
73
Is affected by PPV, posture, tachycardia above 120 beats/mon ineffective atrial contraction (supraventricular arrhythmias) and pericardial pressures.
Venous return
74
What is the period immediately after ventricular contraction?
(Lasts 0.03 to 0.06 seconds)
Isovolumic Relaxation
75
What law/mechanism describes the relationship between stroke volume and end-diastolic volume? (The intrinsic ability of the heart to adapt to increasing volumes of inflowing blood).
Frank-Starling Mechanism or Starling's Law
75
The force of resistance against which the heart must pump to eject blood. It is primarily determined by the systemic vascular resistance and the resistance in the aorta that the left ventricle must overcome to eject blood into systemic circulation.
Afterload (LV afterload usually equals systemic vascular resistance, which is dependent on arteriolar tone)
76
The volume of blood in the ventricles just before contraction. It represents the preload- the more blood in the ventricles, the greater the stretch on the cardiac muscle fibers.
End-Diastolic Volume (EDV)
76
Amount of blood pumped by the heart with each contraction. Depends on factors like preload, afterload, and contractility.
Stroke Volume
77
What effects Left Ventricular Afterload?
1. Size and mechanical behavior of large arterial conduits (atherosclerosis)
2. Aortic Valve (stenosis)
3. Terminal arteriolar impedance (hypoxic induced vasodilation)
4. Left ventricular wall stress
78
What effects Right Ventricular Afterload?
1. Size and mechanical behavior of large pulmonary arteries (PE)
2. Pulmonic valve (stenosis)
3. Pulmonary arteriolar impedance (hypoxia and hypercarbia induced vasoconstriction)
4. Right ventricle wall stress
79
Myocardial contractility is depressed by:
1. Anoxia
2. Acidosis
3. Depletion of catecholamine stores within the heart
4. Loss of functioning muscle mass as a result of ischemia or infarction
80
Amount of blood ejected from the left ventricle, normally is equals the venous return
Cardiac Output
81
Calculation for CO=
CO= SV x HR
82
Where does the RCA supply blood to?
Supplies the right atrium, most of the right ventricle, and variable portions of the left ventricle (85% of the population the RCA gives rise to the PDA- supplying superior-posterior intraventricular septum and most left ventricle).
83
Where does the LCA supply blood to?
Supplies left atrium, most of intraventricular septum, and most of the left ventricle. LCA bifurcates into LDA and LCX
84
Resting coronary blood flow averages ____ mL/100g of heart weight or ______mL/min (~5% of total cardiac output)
70; 250
85
How many folds can CO increase during strenuous exercise
4-fold to 7-fold
86
How many folds can coronary blood flow increase during strenuous exercise?
3-fold to 4-fold to supply nutrients
87
What is influenced by physical, neural and metabolic factors?
Coronary blood flow
88
Amount of oxygen that the heart requires to maintain optimal function
Myocardial oxygen demand
89
Amount of oxygen provided to the heart by the blood which is controlled by the coronary arteries
Myocardial oxygen supply
90
Conditions that increase oxygen demand or decrease oxygen delivery may contribute to an exacerbation of previous stable angina:
Fever, infection, anemia, tachycardia, thyrotoxicosis, heart failure, and cocaine use
91
Determinants of myocardial consumption:
1. HR (main determinant- increasing HR by 50% increases the myocardial oxygen consumption by 50%)
2. Preload (minor contributor)
3. Contractility (major contributor)
4. Afterload (major contributor)
92
Vasodilatory substances released from the myocardium in response to decreased oxygen delivery include:
1. Adenosine (primary substance)
2. Adenosine phosphate compounds
3. Potassium ions
4. Hydrogen ions
5. Carbon Dioxide
6. Bradykinin
7. Prostaglandin
93
Sense blood pressure in carotid sinus and aortic arch
Low BP- increased SNS tone (increased HR, inotrophy and vasoconstriction)
High BP- increased PNS tone (CN X, reduced HR/inotropy
Barorecptor Reflex
94
Stretch receptors in the right atrium that sense CVP
High CVP- increases SNS tone(increased HR) and decreased PNS tone (CN X)
Atrial Receptor (Bainbridge) Reflex
95
PaO2 and pH sensors in carotid bodies and aortic bodies
Low PaO2 and pH- increased ventilation and PNS tone- decreased HR and inotropy
Chemoreceptor Reflex
96
Stretch receptors in extraocular muscles sense pressure on globe (ciliary nerves and CN V)
High globe pressure- increased PNS tone (CN X- decreased HR)
Oculocardiac Reflex
97
Increased ICP
High ICP- increased SNS tone- increased inotropy and vasoconstriction- low HR (baroreceptor reflex)
Cushing Reflex
