1
Q
In single muscle fibres, when does contraction start?
A
Just after depolarisation.
2
Q
When does contraction finish?
A
About 50ms after repolarisation is completed.
3
Q
Which part of the ECG corresponds with when atrial systole starts?
A
Just after the P wave
4
Q
Which part of the ECG corresponds with when ventricular systole starts?
A
Near the end of the R wave
5
Q
Which part of the ECG corresponds with when ventricular systole ends?
A
Just after the T wave
6
Q
What does the term systolic pressure relate to?
A
The peak pressure reached in the vascular system during systole.
7
Q
What does the term diastolic pressure relate to?
A
The lowest pressure reaches in the vascular system during diastole.
8
Q
What is happening to the AV and semilunar valves during late diastole?
A
AV valves: open
AND
Semilunar valves: closed
9
Q
What happens during diastole?
A
Blood flows to fill the atria and the ventricles
10
Q
When does the rate of ventricular filling during diastole decline?
A
When the ventricles become distended
AND
When the heart rate is low
11
Q
What happens to the AV valves when the rate of ventricular filling starts to decline?
A
They drift closed
12
Q
What percentage of ventricular filling occurs passively during diastole?
A
70%
13
Q
What happens to the AV valves and semilunar valves during isovolumetric ventricular contraction?
A
AV valves: closed
Semilunar valves: closed
14
Q
What happens to the AV valves and semilunar valves during ventricular ejection:
A
AV valves: closed
Semilunar valves: open
15
Q
What happens to the AV valves and semilunar valves during isovolumetric ventricular relaxation?
A
AV valves: closed
Semilunar valves: closed
16
Q
What happens to the AV valves and semilunar valves during ventricular filling AND atrial contraction?
A
AV valves: open
Semilunar valves: closed
17
Q
What is the purpose of atrial contraction?
A
Propels any additional blood into the ventricles.
18
Q
Contraction of the atria narrows the orifices of which structures?
A
Superior vena cava
Inferior vena cava
Pulmonary veins
19
Q
What happens to the AV valves at the start of ventricular systole?
A
They close
20
Q
What happens to intraventricular pressure at the start of ventricular sysotle?
A
Pressure rises very quickly
21
Q
Why does intraventricular pressure increase at the start of systole?
A
Because the myocardium presses on the blood in the ventricle
22
Q
How long does isovolumetric ventricular contraction last for?
A
0.05 seconds
23
Q
When does isovolumetric ventricular contraction end?
A
When pressures in the right and left ventricles exceed pressures in the aorta and pulmonary artery
AND
When the aortic and pulmonary valves open
24
Q
What is the usual pressure in the aorta?
A
80mmHg
25
What is the usual pressure in the pulmonary artery?
10mmHg
26
Why is there a small rise in atrial pressure during isovolumetric ventricular contraction?
Because the AV valves bulge into the atria during this time.
27
What happens to the aortic and pulmonary valves during isovolumetric ventricular relaxation?
They close.
28
What are the 5 phases of the cardiac cycle?
1 = atrial systole
2 = isovolumetric ventricular contraction
3 = ventricular ejection
4 = isovolumetric ventricular relaxation
5 = ventircular filling
29
What is phase 1 of the cardiac cycle?
Atrial systole
30
What is phase 2 of the cardiac cycle?
Isovolumetric ventricular contraction
31
What is phase 3 of the cardiac cycle?
Ventricular ejection
32
What is phase 4 of the cardiac cycle?
Isovolumetric ventricular relaxation
33
What is phase 5 of the cardiac cycle?
Ventricular filling
34
What happens to the pressures of the aorta and left ventricle during late systole?
Aortic pressure actually EXCEEDS left ventricular pressure
35
When aortic pressure exceeds left ventricular pressure at the end of systole, how does blood keep flowing?
Momentum keeps blood flowing out of the ventricle for a short period of time.
36
When does the phase of ventricular ejection begin?
When the aortic and pulmonary valves open.
37
What happens to ejection as systole progresses?
It begins to slow down.
38
What is the peak pressure that is reached in the left ventricle?
120mmHg
39
What is the peak pressure that is reached in the right ventricle?
25mmHg
40
How much blood is ejected by each ventricle per stroke at rest?
70-90mls
41
What is the usual end-diastolic ventricular volume?
130mls
42
How much blood tends to remain in each ventricle at the end of systole?
~50ml
43
What is the usual end-systolic ventricular volume?
~50ml
44
What is a normal ejection fraction?
65%
45
How to you calculate ejection fraction?
Stroke volume / end-diastolic ventricular volume
46
How can ejection fraction be measured?
Equilibrium radionuclide angiocardiography OR CT scan
47
In early diastole, when the ventricular muscle is fully contracted, what happens to ventricular pressure?
It falls rapidly
48
What is protodiastole?
The period of time when the ventricles are fully contracted and the falling ventricular pressure falls more rapidly.
49
How long does protodiastole last?
0.04 seconds
50
When does protodiastole end?
When the aortic and pulmonary (semilunar) valves close.
51
What causes the aortic and pulmonary valves to close at the end of protodiastole?
When the momentum of ejected blood into the aorta and pulmonary artery is overcome.
52
What happens to pressure in the ventricles during isovolumetric ventricular relaxation?
It drops rapidly
53
When does isovolumetric ventricular relaxation end?
When ventricular pressure falls below the atrial pressure
AND
When the AV valves open
54
What happens to atrial pressure during ventricular systole?
It rises.
55
Atrial systole occurs on which side of the heart first?
Right side
56
Ventricular contraction occurs on which side of the heart first?
Left side
57
Ventricular ejection occurs on which side of the heart first?
Right
58
Why does ventricular ejection of the right ventricle happen before the left?
Because pressure in the pulmonary artery is lower than the pressure in the aorta and therefore easier to overcome.
59
What happens to the aortic and pulmonary valves during expiration?
Both valves close at the same time.
60
What happens to the aortic and pulmonary valves during inspiration?
Aortic valve closes slightly before the pulmonary valve.
61
What is cardiac muscle able to do to compensate for a faster heart rate?
It is able to contract and repolarise faster when the heart rate is higher.
62
What is the duration of systole when the heart rate is 65bpm?
0.27 seconds
63
What is the duration of systole when the heart rate is 200bpm?
0.16 seconds
64
What allows for a decreased duration of systole with faster heart rates?
A decrease in the duration of systole.
65
Does systole or diastole decrease in duration most to compensate for faster heart rates?
Diastole
66
What is the duration of diastole when the heart rate is 65bpm?
0.62 seconds
67
What is the duration of diastole when the heart rate is 200bpm?
0.14 seconds
68
Coronary blood flow to which part of the heart occurs during diastole?
Subendocardial portions of the left ventricle.
69
At a heart rate of 180bpm, what factors ensure that ventricular filling during diastole is adequate?
Ample venous return
Cardia output per minute is increased by rate
70
What is the maximum number of impulses that the AV node can conduct during a minute?
230 impulses
71
Why can the AVN not conduct more than 230 impulses per minute?
Due to its long refractory period.
72
When is the only time a ventricular contraction rate of more than 230bpm will be seen?
Paroxysmal ventricular tachycardia
73
What rate does the pulse wave travel at in the aorta?
4 m/s
74
What rate does the pulse wave travel at in the large arteries?
8 m/s
75
What rate does the pulse wave travel at in the small arteries?
16 m/s
76
How long after the peak systolic ejection into the aorta is the radial pulse felt?
0.1s
77
What happens to the pulse wave with advancing age?
The pulse wave moves faster because the arteries become more rigid.
78
The strength of the pulse is determined by what?
The pulse pressure
79
How does the pulse feel in a patient with aortic regurgitation?
Very strong (due to an incompetent aortic valve)
80
What can happen to the head in a patient with aortic regurgitation?
Nodding can occur in time with the pulse.
81
What type of pulse pathognomonic for aortic regurgitation?
Corrigan pulse OR water-hammer pulse
82
What is a dicrotic notch?
A small oscillation in the falling phase of the pulse wave caused by vibrations set up when the aortic valve snaps shut
83
Is the dicrotic notch palpable at the wrist?
No
84
Does the pulmonary artery pressure have a dicrotic notch?
Yes
85
What happens to the AV valves in early diastole?
They are open.
86
Atrial pressure changes are transmitted to where?
The relevant great veins
87
Atrial pressure changes form which graphs?
Jugular venous pressure graphs
88
What causes the a wave on a jugular venous pressure graph?
Atrial systole
89
Why does the a wave on a jugular venous pressure graph occur?
Because during atrial systole, there is some blood regurgitation back into the great veins when the atria contract
90
What causes the c wave on a jugular venous pressure graph?
Bulging of the tricuspid valve into the atria during isovolumetric ventricular contraction.
91
Why does the c wave on a jugular venous pressure graph occur?
Due to the transmitted manifestation of the rise in atrial pressure that occurs by the bulging of the tricuspid vale during isovolumetric ventricular contraction.
92
What causes the v wave on a jugular venous pressure graph?
Rise in atrial pressure before the tricuspid valve opens during diastole.
93
What happens to venous pressure during inspiration?
It falls during inspiration.
94
Why does venous pressure fall during inspiration?
Due to the increased negative intrathoracic pressure.
95
What causes the first heart sound?
Sudden closure of the AV valves at the start of ventricular systole.
96
What causes the second heart sound?
Vibrations associated with the closure of the aortic and pulmonary valves just after the end of ventricular systole.
97
What are the characteristics of the first heart sound?
Low pitched
Slightly prolonged
Lub
98
What are the characteristics of the second heart sound?
Higher-pitched
Shorter
Dub
99
When does the first heart sound occur?
Start of ventricular systole
100
When does the second heart sound occur?
Just after the end of ventricular systole.
101
When would a 3rd heart sound be heard?
About 1/3rd of the way through diastole
102
What causes a 3rd heart sound?
Vibrations set up by the inrush of blood during rapid ventricular filling
103
What action does a 3rd heart sound coincide with?
Rapid ventricular filling
104
What are the characteristics of the 3rd heart sound?
Soft
Low-pitched
105
When would a 4th heart sound be heard?
Immediately before the first heart sound
106
What 2 factors can cause a 4th heart sound to be heard?
High atrial pressure
Stiff ventricle (ventricular hypertrophy)
107
Which people can 3rd heart sounds commonly be heard in?
Young, healthy individuals
108
What is a 4th heart sound due to?
Ventricular filling
**Rarely heard in normal adults
109
What is the duration of the 1st heart sound?
0.15 seconds
110
What is the auditory frequency of the first heart sound?
25-45 Hz
111
What is the duration of the second heart sound?
0.12 seconds
112
What is the auditory frequency of the second heart sound?
50Hz
113
What causes physiological splitting of the 2nd heart sound?
The interval between the aortic and pulmonary valves closing during inspiration.
114
What is the duration of the 3rd heart sound when present?
0.1 seconds
115
What are the characteristics of normal blood flow?
Laminar
Non-turbulent
Silent
(Up to a critical velocity)
116
What causes blood flow to be turbulent?
When blood flow exceeds the critical velocity (such as after an obstruction).
117
When does blood flow tend to speed up?
When an artery or a heart valve is narrowed.
118
What is the timing of the murmur in aortic stenosis?
Systolic
119
What is the timing of the murmur in pulmonary stenosis?
Systolic
120
What is the timing of the murmur in aortic regurgitation?
Diastolic
121
What is the timing of the murmur in pulmonary regurgitation?
Diastolic
122
What is the timing of the murmur in mitral stenosis?
Diastolic
123
What is the timing of the murmur in tricuspid stenosis?
Diastolic
124
What is the timing of the murmur in mitral regurgitation?
Systolic
125
What is the timing of the murmur in tricuspid regurgitation?
Systolic
126
Why can systolic murmurs be heard in patients with anaemia?
Because the low viscosity of the blood is associated with rapid flow.
127
In patients with congenital interventricular septal defects, what type of murmur can there be?
Systolic murmur
128
What are 2 methods of measuring cardiac output?
Direct Fick's method
Indicator dilution method
129
What does Fick's principle state?
Total oxygen consumption by tissues equals the product of blood flow (cardiac output) and the arteriovenous oxygen difference (oxygen delivered minus oxygen used).
130
When is the only time that Fick's principle can be applied?
When the arterial blood is the only source of the substance taken up.
131
How can Fick's law be used to determine cardiac output?
By measuring the amount of O2 consumed by the body in a given period and dividing this value by the A-V difference across the lungs.
132
Why can an arterial O2 content be measured in a sample obtained from any artery in the body?
Because systemic arterial blood has the same O2 content in all parts of the body.
133
How is a sample of venous blood from the pulmonary artery obtained?
Cardiac catheter
134
How do you calculate cardiac output using Fick's law?
CO = O2 consumption (ml/min) / (AO2 - VO2)
135
How do you calculate flow of dye in an indicator dilution technique?
Flow (F) = amount of indicator (E) / instant concentration of indication in arterial blood (C)
**THEN input flow as the oxygen consumption number in Fick's equation to get cardiac output.
136
In the thermodilution method of calculating cardiac output, temperature change from normal saline is inversely proportional to what?
The amount of blood flowing through the pulmonary artery.
137
Define stroke volume.
The amount of blood pumped out of the heart per beat.
138
Give the equation for calculating cardiac output from stroke volume and heart rate.
CO = SV x HR
139
What is the average stroke volume from each ventricle per beat during rest in the supine position?
70ml
140
Define cardiac output.
The amount of blood pumped out of the heart per unit of time.
141
What is the average cardiac output in a resting, supine man?
5L/ min
142
The correlation between resting cardiac output and body surface area equals what?
Cardiac index
143
Give the 6 factors that cause an increased cardiac output.
-Anxiety/ excitement
-Eating
-Exercise
-High environmental temperature
-Pregnancy
-Adrenaline
144
Give 3 factors that cause a decreased cardiac output.
-Moving to sitting/ standing from lying position
-Rapid arrhythymias
-Heart disease
145
Give 2 factors that do not change cardiac output.
-Sleep
-Moderate changes in environmental temperature
146
Heart rate is controlled predominantly by which nerves?
Autonomic
147
Which nerves increase heart rate?
Sympathetic
148
Which nerves decrease heart rate?
Parasympathetic
149
Catecholamines have what 2 actions on the heart?
Chronotropic (increased rate)
Imotropic (increase strength of contraction)
150
The force of contraction of cardiac muscle depends on which 2 factors?
Preload and afterload
151
Define preload.
The degree of stretch of cardiac myocytes before contraction.
152
Define afterload.
The resistance that the caridiac myocytes must overcome in order to expel blood.
153
Define the Frank-Starling law of the heart.
States that the energy of contraction is proportional to the initial length of the cardiac muscle fibre.
154
How is the frank-starling law applies to tension in cardiac muscles?
The length of muscle fibres (preload) is proportional to the end-diastolic volume.
155
What does the Frank-Starling curve show?
The relationship between ventricular stroke volume and end-diastolic volume.
156
What is heterometric regulation?
When cardiac output is regulated by changes in cardiac muscle fibre length.
157
What is the effect on stroke volume when systolic contractions are reduced?
SV decreases
158
The myocardium is covered by a fibrous layer called what?
Epicardium
159
The epicardium is surrounded by what?
Pericardium
160
What pericardium separates the heart from what?
The rest of the thoracic viscera.
161
The pericardial sac between the epicardium and pericardium contains how much fluid?
5-30ml
162
What is the function of pericardial fluid?
Lubricates the heart and reduces friction during heart contractions.
163
Give 3 causes of reduced ventricular filling.
1) INCREASED PERICARDIAL PRESSURE:
-infection
-pressure from a tumour
2) DECREASED VENTRICULAR COMPLIANCE:
-MI
-Infiltrative disease
3) DECREASED VENOUS RETURN TO THE HEART
164
Which actions of the atria aid in ventricular filling?
Contractions
165
An increase in total blood volume has what effect on venous return to the heart?
Increased venous return
166
Which action from veins causes increased venous return to the heart?
Constriction of veins
167
Why does constriction of veins cause increased venous return to the heart?
Constricted veins = reduced venous reservoirs = decreased venous pooling = increased venous return.
168
Standing causes what effect on venous return to the heart?
Decreases venous return to the heart
169
Muscular activity has what effect on venous return to the heart?
Increases it
170
Why does muscular activity increase venous return to the heart?
Due to the pumping action of skeletal muscle
171
What is the relationship. between intrathoracic pressure and venous return to the heart?
Inversely proportional
172
What happens to venous return when there is an increase in intrathoracic pressure?
It reduces
173
What happens to venous return when there is a decrease in intrathoracic pressure?
It increases
174
How does decreased intrathoracic pressure reduce venous return to the heart?
Breathing in
=
Decreased intrathoracic pressure
=
Reduced right atrial pressure
=
Bloods is squeezes towards the heart
=
Increased venous return
175
Sympathetic stimulation has what 2 effects on the heart?
Increased contractility
Increased heart rate
176
Parasympathetic stimulation has what 2 effects on the heart?
Decreased contractility
Decreased heart rate
177
What way does the frank-starling curve shift with decreased contractility?
Downwards and to the right
178
What way does the frank-starling curve shift with decreased contractility?
Upwards and to the left
179
What is the effect of an increased preload on force of contraction?
Increased preload = increased contractility
180
What is the effect of an increased afterload on force of contraction?
Increased afterload = increased contractility
181
How to catecholamines exert their inotropic effect on the myocardium?
They act on cardiac B1 adrenergic receptors = increased cAMP.
182
Why do xanthines and caffeine cause increased contractility?
Because they inhibit breakdown of cAMP.
183
Why does digoxin increase cardiac contractility?
Inhibit the Na/K ATPase in the myocardium = reduced calcium removal from cytosol by Na/Ca exchange
184
Give 5 causes of decreased myocardial contractility.
Hypoxia
Hypercapnia
Acidosis
Drugs (quinidine, procainamine, barbituates)
Heart failure (intrinsic depression)
185
Give 3 causes of increased myocardial contractility.
Drugs (digoxin, theophylline)
Caffeine
Catecholamines
186
Why is stroke volume reduced in systolic heart failure?
Because ventricular contraction is weak.
187
Why does ejection fraction fall in systolic failure?
Because the reduced strength of ventricular contraction causes an increase in the end-systolic ventricular volume.
188
What are the 2 initial responses of the heart to failure?
Activation of the genes causing cardiac myocyte hypertrophy
AND
cardiac remodelling (thickening of the ventricular wall)
189
Incomplete arterial filling in heart failure causes what 2 responses from the body?
Increased discharge of sympathetic nerves
AND
Increased secretion of renin and aldosterone (causes water and Na retention)
**The above mechanisms initially are compensatory
190
Why is stroke volume reduced in diastolic heart failure?
Reduced elasticity of the myocardium means that filling during diastole is reduced.
191
Why are ACEi's beneficial in heart failure?
Reduce circulating aldosterone = decrease BP = reduced afterload against which the heart pumps.
192
Why are nitrites and hydralazine effective in treating heart failure?
Reduce venous tone = increase venous capacity = reduced return of blood to the heart = lower the preload.
193
What is the effect of digoxin on calcium?
Increases stores of intracellular calcium = positive inotropic effect.
194
In a normal heart during exercise, what is the main way cardiac output is increased?
Increased heart rate
195
In a transplanted heart during exercise, what is the main way cardiac output is increased?
Increased stroke volume
196
Why do transplanted hearts rely on stroke volume to increased cardiac output?
Because a lack of neural input means that heart rate does not increase effectively
197
Why do you get a raised lactate in shock?
Reduced tissue perfusion = increased anaerobic respiration = increased lactic acid produced as byproduct
198
What is basal oxygen consumption by the myocardium?
2ml / 100g / minute
199
What is oxygen consumption by the beating heart?
9ml / 100g / minute
200
What rate is blood flow to resting skeletal muscle?
2-4ml/100g/minute
201
Give 3 local mechanisms that maintain high rates of blood flow in exercising muscle.
Fall in tissue pO2
Rise in tissue pCO2
Accumulation K+ (and other vasodilator metabolites)
202
What is VO2 max?
Maximal oxygen consumption per kg per minute
203
What is the average VO2 max in healthy men?
38ml/kg/min
204
What is the average VO2 max in healthy women?
29ml/kg/min
205
VO2 max is the product of what?
Maximal cardiac output and maximal O2 extraction by tissues
206
Ventricular work is the product of what?
Stroke volume and mean arterial pressure in the pulmonary artery or aorta (depending on if right or left ventricle)
207
Aortic pressure is how many times greater than pulmonary artery pressure?
7x
208
Overall what happens to cardiac output during exercise?
Large increase
209
ACEM primary - physiology
flashcards
Decks in class (24)
# Cards
-
Cardiac physiology - electrical111
-
Cardiac physiology - pump function209
-
ECG physiology110
-
Cardiac muscle physiology0
-
Cardiac regulation physiology0
-
Circulation through specific regions0
-
Circulation physiology0
-
General principles of physiology148
-
Cellular physiology3
-
Physiology calculations and equations7
-
Molecular building blocks117
-
Respiratory structure and function73
-
Respiratory ventilation77
-
Respiratory diffusion73
-
Respiratory blood flow and metabolism172
-
Respiratory ventilation-perfusion relationships0
-
Respiratory gas transport0
-
Respiratory mechanics of breathing0
-
Respiratory control of breathing131
-
Respiratory system under stress0
-
Tests of pulmonary function0
