cardiac Flashcards
1
Q
what is the general purpose of the cardiac system?
A
deliver nutrients and oxygen
remove waste
provide thermoregulation
2
Q
describe the general purpose of the heart?
A
serves as a pump that establishes the pressure gradient needed for blood to flow to tissues
3
Q
describe the general purpose of blood vessels?
A
passageways through which blood is distributed from heart to all parts of the body and back to the heart
4
Q
decribe the general purpose of blood?
A
a transport medium which whihc materials being transported are dissolved or suspended within
5
Q
how big is the heart?
A
approximately the size of a clenched fist
6
Q
where does the heart lie in the chest?
A
midline in the thoracic cavity between sternum and spine
7
Q
which part of the heart is called the base?
A
the top, broad portion
8
Q
which part of the heart is called the apex?
A
the bottom, pointed portion
9
Q
how is the heart oriented?
A
at an angle with the base to the right and apex on the left
10
Q
when beating, which part of the body does the apex beat against?
A
the left chest wall
11
Q
what are the 2 cardiovascular circulations?
A
pulmonary and systemic
12
Q
what is the pulmonary circulation?
A
closed loop of vessels carrying blood between heart and lungs
13
Q
what is the systemic circulation?
A
circuit of vessels carrying blood between the heart and other body systems
14
Q
describe the purpose of the right side of the heart;
A
pumps blood to be reoxygenated
15
Q
describe the purpose of the left side of the heart;
A
recieves freshly oxygenated blood to be sent elsewhere
16
Q
how are the right and left side of the heart generally related?
A
the volume of blood pumped by the right side will become the volume of blood pumped by the left side
17
Q
what is the pressure and resistance flow of pulmonary circulation?
A
low pressure, low resistance
18
Q
what is the pressure and resistance flow of systemic circulation?
A
high pressure, high resistence
19
Q
which side of the heart can generally be said to do more work?
A
the left ventrical since the volume is the same but pumped at a hugher pressure against higher resistence
20
Q
what is the purpose of valves?
A
ensure blood flow is unidirectional
21
Q
when do valves open?
A
when there is a higher forward pressure gradient
22
Q
when do valves close?
A
when there is a higher backward pressure gradient
23
Q
the left and right sides of the heart contract and pump ____
A
simultaneously
24
Q
what are papillary muscles and where are they located?
A
ventricals
contract with heart contraction to secure the valve and keep the seal intact
25
what are chordae tendinae and where are they located?
ventricles
fibrous tendons
heart strings
26
what valves are known as the semilunar valves?
aortic and pulmonaary
27
the right AV valve is ____
tricuspid
28
the left AV valve is ____
bicuspid
29
what are the fibrpus rings of the heart?
connective tissue that seperates the atria and ventricles. they encapsulate each valve to hold them in place during beats
30
describe the endocardium;
a single cell thick wall that lines the inner layer of the heart
31
descirbe the myocardium;
holds contractile and electrical cells that underlie spontaneous contraction
32
what are the features of the cardiac wall?
endocardium
myocardium
epicardium
pericardial cavity
pericardial sac
33
why does cardiac muscle have lots of mitochondria?
because the heart has a high energy requirement and has high oxidative tendancies
34
what system innervates cardiac muscle?
autonomic nervous system - not voluntary
35
cardiac muscle fibers are connected by ____
intercalcated discs
36
99% of cells in the heart are ____
contractile
37
1% of cardiac cells have ____ activity that stimulate the heart
pace maker/autorhythmicity
38
do atria and ventricular cells have gap junctions?
no, they are seperated by non-conductive barrier (fibrous skeleton)
39
what are the 2 consequences of high connectivity by sepcial system?
1 - spontaneous impulse generated at one place spreads throughout the heart
2: all cardiac fibers contract or none do
40
what are the 4 specialized conduction pathways?
SA node
AV node
bundle of His
purkinje fibers
41
describe the SA node;
in superior vena cava of the R atria. drives regular paace
42
describe teh AV node;
slow things down to ensure atrial contraction before delivering to ventricles
43
describe the purkinje fibers;
conducts electrical signals along the wall of the heart
44
what are the 3 efficiency criteria for cardiac function?
1: atrial excitation and contraction must complete before ventrical contraction can begin
2: cardiac muscle excitation coordinated for heart chamber to contract as a unit
3: pair of atria and pair of ventricles coordinated as a pair that contracts siumltaneously
45
describe the 4 steps of the spread of strial excitation;
1: keep atria beating together
2: 30 ms delay. keeps the atria beating before ventricles
3: AV nodal delay, 100ms, allow atria time to fully contract to fill ventricles
4: from AV node to entire cardiac purkinje system, 30 ms. keep ventricles beating together
46
SA failure would lead to ____
abnormal pace maker activity by latent pacemakers
47
what is complete heart block?
loss of conduction between atria and ventricles. would require an atrifical pace maker
48
what is ectopic focus?
overy excitable region that depolarizes faster that SA node. can lead to premature ventricle contraction so therefore it will not have the full effective contraction.
49
what is the orientation of the aortic valve?
approximately at the level of the sternal angle which is between the manubrium and sternal body
50
veins lead ___
into atria
51
arteries lead __-
out of ventricles
52
the septum refers to ___
the wall between the 2 halves of the heart
53
which ventrical wall is thicker?
left
54
the aorta is a single large artey that exits the ___ ventricle
left
55
what is resistence?
the opposition to flow caused in part by friction betwen the flowing blood and vessel wall
56
how is prolapse/eversion of the AV valves prevented?
by tension on the valve leaflets exerted by the chordae tendineae when the papillary muscles contract
57
how is prolapse/eversion of the semilunary valves prevented?
when semilunary valves are swept closed, their upturned edges fit together in a deep, leak proof seam that prevents eversion
58
the left AV valve is referred to as the bicuspid or ___ valve
mitral
59
closure of the AV valve produces the ___ sound
lub
60
do semilunary valves have chordae tendinae?
no
61
closure of the semilunary valves produce the ____ sound
dub
62
the epicardium makes up ____
the visceral layer of the serous pericardium
63
what is thge pericardial sac filled with?
pericardial fluid
64
what does pericardial fluid do?
reduces friction between sirfaces
65
the parietal layer of the ____ is the inner layer of the pericardial sac
serous pericardium
66
what part of the pericardial sac helps keep the heart hanging in the thoracic cavity?
fibrous pericardium
67
how do cardiac muscles orient themselves for the heart?
around it in a spiral
68
when the heart muscle contracts, what do the muscle fibers do?
twist in an upward direction - sort of wringing it out
69
cardiac muscle fibers are joined by ___
gap junctions and mechanical connections (desmosomes)
70
what does autorhythmicity mean?
it means that cells can generate their own action potentials across cardica muscle membranes to cause contractions
71
the 'I(f)' channel is activated upon ___
hyperpolerization.
72
' I(Ca,T)' differ from longer lasting voltage gated Ca2+ channels because:
they open at lower membrane potentials and further depolarizes the membrane
73
once threshold is reach, the rising phase occurs due to ___
a large influc of Ca2+ passing through L-type channels
74
the falling phase is due to efflux of ___
K ions through 'I(K)' channels
75
after action potential, the slow closure of K channels and opening of ___ channels initiates the next depolarization
'I(f)'
76
what is 'I(Ca,L)'?
a long lasting voltage gated Ca2+ channel present in contractile ccells
77
what is 'I(K)' responsibel for?
repolarization
78
what is the bundle of HIs?
a tract that origniates at the Av node, enters the inter-ventricular septum and divides to form right and left bundle branches. they follow the septum down and curve around the tip of the ventricular champers and travel back toward the atria along the walls
79
what is fibrillation?
uncoordinated excitation and contraction of cardiac cells. can occur in either or both atria and ventricle
80
what is electrical defibrillation?
corrective measure for ventricular fibrillation
81
what is the interatrial pathway?
SA node -- left atrium (keeps atria beating together)
82
what is the internodal pathway?
SA node --- AV node
83
what are the general purpose of contraactile cells?
do the mechanical work
84
do contractile cells initiate their own action potentials?
no
85
what is the general purpose of autorhythmic cells?
initiating and conducting action potentials responsible for contraction of working cells
86
what are the 5 phases of action potential in contractile cells?
Phase 0 - rapid depolarization
Phase 1 - rapid repolarization
Phase 2 - plateau
Phase 3 - repolarization
Phase 4 - rest
87
what happens during phase 0/rapid depolarization in contractile cells?
cell becones less negative because of activation of Na channel and movement of Na (fast voltage gated Na+ channels)
88
what happens during phase 1/rapid repolarization of contractile cells?
cells begin to reverse polarity toward the negative direction because of a specific activation of a K+ pathway while those fast-sodium channels close
(activation of transient outward K+ channels)
89
what happens during phase 2/plateau of contractile cells?
long type calcium channels open during the rapid depolarization and remain open (delayed K+ channel)
90
what happens during phase 3/repolarization of contractile cells?
closing of long calcium channels and dominant outward K+ movement (delayed K+ channel)
91
what happens during phase 4/rest of contractile cells?
inward rectifying of Na and K channels.
92
describe the pathway of excitation-contarction coupling;
- action potential initiated in contractile cells
- goes down T tubule
- small amount of Ca2+ enter from ECF AND Ca also released from internal store in the SR - most released from here
- cytosolic Ca2+ increased
- troponin-tropomyosin complex in THIN filaments pulled aside
- cross bridgin between thick and thin filaments
- thin filaments slide inward
- contraction
93
can summation occur in cardiac muscle?
no
94
how can electrical currents be detected in skin in the body isnt a piece of electrical equipment?
the body fluids are conductive!
95
what do EKGs show?
direction and magnitude of currents over time - SUM of all electrical currents at any given time
96
what cell activity is an EKG dominated by?
contractile cells
97
what does the P wave on an EKG show and what does it look like?
- a little tiny hump before the QRS
- shows atrial depolarization prior to contraction
98
what does the PR segment on an EKG show and what does it look like?
- from the P wave (little hump) to the peak of the QRS segment
- shows AV nodal delay - the time for electrical current to pass from atria to ventricals
99
what does the QRS segment on an EKG show and what does it look like?
- sharp peak/jump - sometimes surrpounded by 2 dipping sections before and after Q and S
- shows ventrical depolarization where the atria is repolarizing at the same time
- R is always present
100
what does the ST segment on an EKG show and what does it look like?
- the end of the QRS segment + a large hump (larger than P wave)
- the time during which the ventricles are contracting and emptying
101
what does the T wave on an EKG show and what does it look like?
- a large hump (larger than P wave)
- shows ventricular repolarizatin
102
what does the TP interval look like on an EKG and what does it show?
- the plateau from the end of the T wave to the start of the P wave
- shows time during which the ventricles are relaxing and refilling before the process begins again
103
why are EKG leads placed so specifically?
so that you can see conduction within the heart from different perspectives
104
where does Lead 1 lie?
right arm (-) to left arm (+)
105
where does Lead 2 lie?
right arm (-) to left leg (+)
106
where does Lead 3 lie?
left aarm (+) to left leg (+)
107
how many chest leads are there?
6
108
how many augmented leads are there?
3
109
where does aVF get placed?
left leg
110
where does aVR get placed?
right arm
111
where does aVL get placed?
left arm
112
how many axis does the EKG show?
12
113
where does electrical excitation originate/begin?
SA node
114
onset of electrical excitation has a total magnitude in mostly the ____ direction
positive/left
115
onset of electrical excitation has a total magnitude in mostly the ____ direction - in comparison to lead 2
a downward positive
116
the QRS can represent _____
spread of excitation
117
tachycardian can be viewed on an EKG as ____
extremely close QRS complexes that indicated a bpm of usually >160
118
brachcardia can be viewed on an EKG as ____-
abnormally far apart QRS complexes indictive of a bpm <60
119
what is extrasystole and how would it look on an EKG?
- premature ventricular contraction
- a strong dip between T and P outside of correct contraction timing
120
what does ventricular fibrillation represent and how would it look on an EKG?
- inadequate depolarization
- would have no discernable waves at all. would be relatively small - like a scribble
121
what does complete heart block represent and how would it look on an EKG?
- conduction not passed from atria to ventrical
- would have a multitude of P complexes between QRS complexes
122
what does myocardial infarction represent and how would it look on an EKG?
- heart attack
- strange mountain looking QRS complexes that are not straight and sharp
123
what is systole?
contractionn and emptying period
124
what is diastole?
relaxation and filling period
125
what is excitation-contraction coupling in the heart driven by?
Ca2+ release
126
what is the primary store for Ca2+?
sarcoplasmic reticulum
127
ECF concentrations of K+ and Ca2+ influence what in regards to contractile AND autorhythmic cells?
starting point, duration, ending point
128
an elevated K+ concentration in the ECf would cause?
reduces membrane potential which can lead to develop ectopic contractions and ectopic pacemaker potentials
129
an elevated Ca2+ concentration in the ECF would cause?
increases strength of contraction and lengthens action potential = less time between contractions
130
what is the absolute refractory period?
the time when a second action potential cannot be triggered
131
leads 1, 2 and 3 are known as ____ leads
bipolar because 2 leads are used
132
why are augmented leads known as unipolar if they also use both leads?
only the actual potential under one electrode is recorded the other is set to 0
133
what are the 4 stages of the generation of the QRS complex known as?
1: septal depolarization
2: apical depolarization
3: L ventricualr depolarization
4: L ventricular depolarization
134
variations from normal heart rate are known as ____
arrhythmias
135
what is it known as when all valves are closed and the ventricles are filled with all the blood that they will recieve?
isovolumetric ventricular contraction
136
describe phase 1 (slow ventricular filling) for the right side of the heart;
- atria AND ventricles are in diastole
- vena cava has low pressure
- right atrium has lower pressure so there is free flow between them
- the right ventricle has lower pressure so the valve is opened allowing blood through
- the pulmonary trunk has high pressure so its valve is closed, no blood can come through
137
describe pase 2 (active ventricular filling) for the right side of the heart;
- atria in systole, ventricle is diastole
- the vena cava remains unchanged
- the atria contracts which increases the pressure and causes a small amount of backflow into the vena cava
- the right ventrical valve remains open as the pressure has not increased too musch
- the pulmonary trunk loses a bit of pressure but not enough to cause the valve to open
138
describe phase 3 ( ventricular emptying) for the right side of the heart;
- atria in diastole, ventricle in systole
- vena cava increases slightly
- atria relaxes so pressure falls
- pressure rises drastically in the ventrical so the valve shuts and ventrical contracts
- the valve to the pulmonary trunk opens and blood enters pulmonary circulation causing an increase in pressure here
1ST HEART SHOUND HEARD
139
describe phase 4 (rapid ventricular filling) for the right side of the heart;
- atria diastole, ventrical diastole
- vena cava remains at low pressure
- atria is also at low pressure
- ventricular pressure drastically decreases so the valve reopens to fill with blood again
- pressure in the pulmonary trunk is high so the valve shuts
2ND HEART SOUND HEARD
140
which side of the heart is constantly under higher pressure?
left
141
describe phase 1 (slow ventricular filling) for the left side of the heart;
- atria AND ventricles in diastole
- pulmonary vein is at low pressure
- atria is at low pressure
- ventricle is at low pressure so the valve is open and slowly filling with blood
- aorta is at extremely high pressure so the valve is shut
142
describe pase 2 (active ventricular filling) for the left side of the heart;
- atria systole, ventricle diastole
- pulmonary vein is at low pressure
- atria increases is pressure so there is backflow
- atria contracts
- pushes blood into ventricle
- aorta pressure decreases but not enough to open valve
143
describe phase 3 ( ventricular emptying) for the left side of the heart;
- atria diastole, ventrical systole
- pulmonary vein is at low pressure
- atria decreases in pressure as it relaxes
- ventrical drastically increases is pressure so valve shuts between atria
- similar pressure in aorta and ventrical causes opening of valve into systemic circulation
1ST HEART SOUND HEART
144
describe phase 4 (rapid ventricular filling) for the left side of the heart;
- atria AND ventricle in diastole
- pulmonary vein is low pressure
- atria is low pressure
- pressure in ventrical drops and relaxes so valve reopens between atria and ventricle
- pressure stays high in aorta so the valve shuts
2ND HEART SHOUND HEARD
145
around how long does systole last?
300 ms
146
around how long does diastole last?
500 ms
147
around hoe long does the entire cardiac cycle last?
800 ms
148
during excercise what volume decreases?
stroke volume - ventricular volume from end diastole to end systoliv
the atria pumps harder to keep up
149
is filling highly impaired during excercise?
nope! much of ventricular filling occurs early in diastole during rapid filling
150
stenotic semilunar valve causes what kind of sound?
what is the defect?
when is the murmur timed?
lub-whistle-dub
a valve that should be opne during systole is not opened all the way
systolic
151
stenotic av valve causes what kind of sound?
what is the decfect?
when is the murmur timed?
lub-dub-whistle
a valve that should be open during diastole does not open all the way
diastolic
152
insufficient AV valve causes what kind of sound?
what is the defect?
when is the murmur timed?
lub-swish-dub
a valve that should be closed during systole does not fully close
systolic
153
insufficient semilunar valve causes what kind of sound?
what is the defect?
when is the murmur timed?
lub-dub-swish
a valve that should be closed durin diastole does not fully close
diastolic
154
what is cardiac output?
the volume of blood ejected by each ventricle each minute
155
is cardiac output through the pulmonary and systemic circulations equal?
yes
156
what is the equation for determining cardiac output?
heart rate x stroke volume
157
what is stroke volume?
how much blood is pumped OUT
158
how can heart rate be varied?
by altering balance of parasympathetic and sympathetic influence
159
what nerve does the parasympathetic system have control over?
vagus
160
what nerve does sympathetic system have control over?
cardiac
161
what is average heart rate?
70 bpm
162
where are the cardio- inhibitory/accelatory centers located?
in the medulla
163
influence of the PNS is to ____ heart rate
decrease
164
describe how the PNS decreases heart rate;
- vagus nerve releases acetylcholine that increases potassium permeability of the SA node (hyperpolarizes SA increasing neg potential and bringing it further away from threshold)
- slowing of Ca2+ inward shortens the plateau phase causing weaker atrial contraction
- this slows down the closure of K+ channels, decreases the AV nodes excitability and increases AV nodal delay
- no effect on ventrical contraction
- slows the time to reach the threshold and AV node
165
influence of the SNS is to _____ heart rate
increase
166
describe how the SNS increases heart rate;
- the SA node is stimulated by norepi
- noepi decreases the time to reach threshold which results in more frequent action potentials and speeds their spread through the conduction pathways
- the atrial and ventricle contractile cells beat more forcefully due to higher Ca2+ permeability AND enhanced excitation-contraction coupling
167
how is stroke volume calculated?
end diastolic violume - end systolic volume
168
what is the intrinsic control of stroke volume?
preload - extent of venous return
169
what is the extrinsic control of stroke volume?
sympathetic activity
170
how do intrinsic and extrinsic controls increase stroke volume?
increasing strength of heart contraction (contractility)
171
what is preload?
the initial stretching of the cardiomyocytes prior to contraction ( related to sarcomere length at the end of diastole)
172
what is contractility?
relative effectiveness or strength of the ventricular pump
173
what is afterload?
the pressure that each ventricle has to work against when pumping blood
174
waht are the 3 determinants of stroke volume?
preload
contractility
afterload
175
what is intropy?
how much the muscle can contract
176
what increases ventricular preload?
atrial intropy
venous blood volume
venous pressure
ventricular compliance
outflow resistance
177
what decreases ventricular preload?
heart rate
ventricular intropy
inflow resistance
venous conpliance
178
the SNS shifts the frank-starling curve to the _____
left
179
what does the ejection fraction represent?
the % of blood pumped out of the heart for every beat
180
what is the equation for the ejection fraction?
stroke volume - end diastolic volume
181
what is the average resting stroke volume?
70 mL per stroke
182
what is the average cardiac output?
5L/min
183
what is cardiac reserve?
the difference between the cardiac output at rest and at maximum exercise/exertion
184
what part of the heart does the vagus nerve primarily innervate?
atria, particularly SA and AV nodes
185
what part of the heart does the cardiac nerve primarily innervate?
ventricles
186
acetylcholine released from the vagus nerve binds to ___
muscarinic receptors coupled to inhibitory G protein reducing cAMP pathway
187
norepi binds to ____
beta-1 adernergic receptors coupled to stimulatory G protein accelerating cAMP pathway
188
even at rest there is predominant _____ input which provides continuous _____ of heart rate
parasympathetic
inhibition
189
what does intrinsic control refer to?
ann inherent ability of the heart to adjust stroke volume ( heart pumps out whatever enters)
190
what does the frank-starling curve show?
the relationship between stroke colume and end diastole volume
191
arterial bp is ___________
aortic bp is _______ for the left ventriclce
pulmonic bp is _________ for the right ventricle
afterload
192
what factor will increase the pressure required of the ventricles to eject blood?
high bp of a stenotic valve
193
an increase in afterload _________ stroke volume
decreases
194
what is the word for enlarged heart muscle?
hypertrophy
195
what is heart failure?
the inability of the cardiac output to keep pace withe the body's demands for nutrients and removal of waste
196
does heart failure only ever affect one ventricle?
no. it can affect one or both ventricles
197
a ventricles inability to pump enough blood can cause __-
blood to become congested or backed up in veins upstream of the ventricle
198
what causes heart failure?
heart attack
impaired coronary circulation
prolonged pumping against chronic afterload
199
a decrease in cardiac contractility (weakened heart) is a defect that causes ____
heart failure
200
what is decompensated heart failure?
the point at which the heart can no longer pump out a normal stroke volume despite compensatory measures
201
congestive heart failure is also know as __-
decompensated heart failure
202
describe cogestive heart failure;
- cardiac muscle fibers are stretched to operating in descending limb of the length-tension curve of the frank-starling law
- blood cannot enter and be pumped out and the venous system dams up
203
heart failure is know as canads ____
silent epidemic
204
the heart muscle is supplied by oxygen and nutrients from what circulatory system?
coronary NOT from blood within the chambers
205
the heart recieves most of its own blood supply that occurs during ___
diastole
206
why does the heart recieve most of the blood from systole instead of diastole?
during systole, coronary vessvels are compressed by the contracting heart muscle
207
why does coronary blood flow vary?
to keep pace with cardiac oxygen needs
208
increasing the metabolic activity of cardiac muscle cells ( or increasing the need for oxygen) in turn causes;
- increase in adenosine
- vasodilation of coronary vessel
- increase in blood flow to cardiac muscle cells
- increased availability of oxygen to meet the need
209
what is atherosclerotic coronary artery disease?
pathological changes within coronary walls that diminish bloodflow through the vessels
210
what is the leading cause of death in canada?
coronary artery disease
211
what can coronary artery disease cause?
myocardial ischemia and possible acute myocardial infarction
212
what are the 3 mechanisms of coronary artery disease?
- profound vascular spasms of coronary arteries
- formation of atherosclerotic plaques
- thromboembolism
213
what would cause immediate death in a patient with acute myocardial infarction?
- the heart is too eak to pump effectively to support body tissues
- fatal ventricular fibrillation caused by damage to specialized conducting tissue occuring because the weakened heart was deprived of oxygen
214
waht would cause delayed death (from complications) in a patient with actue myocardial infarction?
- fatal rupture of the degenerating area of the heart wall
- slowly progressing congestive heart failure where the heart becomes unable to pump out all the blood returned to it
