Cardio Flashcards
(111 cards)
1
Q
What is the purpose of the cardiac valves?
A
to ensure unidirectional flow
2
Q
What are the two valves on the left side of the heart? (systemic circulation)
A
mitral valve and aortic valve
3
Q
What are the two valves on the right side of the heart? (pulmonary circulation)
A
tricuspid valve and pulmonic valve
4
Q
what is the main function of pulmonary circulation?
A
gas exchange
5
Q
what is the main function of the systemic circulation?
A
transport O2 to and from organs/tissues
6
Q
The two circulatory systems are in ____
A
series
7
Q
Define a portal system
A
when blood passes through two consecutive capillary networks
8
Q
List the three main adult portal systems
A
-hepatic
-kidneys
-anterior pituitary
9
Q
What is the major blood supply to the liver? ~75%
A
the hepatic portal vein
10
Q
of the total blood volume, what percent is in the systemic circulation at a time?
A
85%
11
Q
True/False: distribution of cardiac output is proportional with organ mass at rest
A
false
12
Q
What is the major site of arterial pressure regulation?
A
arterioles
13
Q
What vessel serves as the major blood reservoir?
A
veins
14
Q
Capillaries have the ____ cross sectional diameter per vessel, but the ______ cross sectional diameter when combines
A
smallest, largest
15
Q
Why are pulmonary circulatory pressure lower than systemic?
A
to ensure gas diffusion
16
Q
True False: fetal lungs don’t perform gas exchange
A
true
17
Q
What are the two shunts in a fetal heart
A
ductus arteriosis and foramen ovale
18
Q
Why does the heart have to have autoregulation to maintain coronary blood flow during high heart rates?
A
because during systole, the coronary arteries are compressed and blood flow decreases
19
Q
Where does the cardiac action potential originate?
A
the SA node
20
Q
Describe how cardiac muscle contraction differ from skeletal?
A
-linked end to end by intercalated discs which contain gap junctions
-shorter and branched
-action potentials can be propagated from cell to cell
21
Q
How are action potentials propagated from atria to ventricles?
A
funneled through the AV node
22
Q
True/False: nerves are required for conduction of electrical activity through the heart
A
false
23
Q
What is the importance of myocyte bifurcation?
A
as AP are conducted from cell to cell activity spreads throughout the cells of the heart
24
Q
What are the two types of cardiac muscle cells?
A
-Contractile
-Conductiong
25
What is autorhythmicity of conduction myocytes?
generation of spontaneous APs by undergoing slow depolarization until threshold is reached
26
What are the three components of the conduction system in the heart?
-AV node, the bundle of His, and purkinje fibers
27
What are the two main functions of the conduction system
-Delays impulse conduction from the atria to the ventricles which allows the ventricles to fill properly
-faster conduction that through gap junctions, so the whole ventricular mass can contract simultaneously
28
What is the annulus fibrosus? what is its function?
it acts like an electrical insulator, it enforces the passage of the electrical signal through the AV node which slows them down
29
Briefly describe the sequence of activation of the heart
-first cells reach threshold in the SA node
-APs are conducted to the AV node through atrial myocytes
-conduction slowly through the AV node
-from the AV node, APs are conducted through purkinje fibers to the bottom of the ventricles
-the bundle splits into right and left branches and activates myocytes in the left and right ventricles
-ventricles contract from apex to base
30
Describe the generation of action potentials in the SA node
-f channels are open and permeable to Na and K, Na flows in
-the membrane slowly depolarizes, the f channels close, the voltage gated Ca channels open, Ca flows into the cell, cell depolarizes further, threshold is reached
-another type of Ca channel opens, Ca flows into the cell, causing steep depolarization
-Ca channels close, K channels open, K leaves cell, repolarization occurs
-K channels close at ~65mV
31
What is the plateau phase of the cardiomyocyte due to?
opening of Ca channels which slows repolarization
32
What are two main differences between excitation-contraction coupling in cardiomyocytes and skeletal muscle?
-Ca release from the SR is induced by Ca in the cytosol not directly due to the action potential
-the long depolarization leads to an absolute refractory period that lasts for almost as long as the contraction.
33
what is chronotropy
heart rate
34
what is inotropy
contractility
35
What neurotransmitter is released by the SNS and what is its affect on the heart rate
Norepinephrine, SA node is depolarized to threshold more frequently
36
What neurotransmitter is released by the PNS? what is its affect on the heart rate? why what two mechanisms?
Acetylcholine. SA node depolarizes to threshold less frequently. it does so by decreasing f-channel current, and increases conductance of K out of the cell which hyperpolarizes the cell
37
How does the SNS affect inotropy?
Ca2+ channel open time is prolonged which means more Ca entering the cell, which yields more forceful contraction
38
How do cardiac glycosides affect contractility? how?
digitalis increases the force of cardiac contraction by slowing the removal of Ca2+ from the cytosol
39
What is circulating troponin I and T a biomarker for?
cardiac injury
40
How do ECGs work?
measures the tiny potential differences on the surface of the body that reflect the electrical activity of the heart.
41
Where should electrodes be placed in animals to get the largest amplitude ECG recording?
The net depolarization moving through the ventricles is moving toward the left hind leg
42
What is the physiological basis of the P wave?
depolarization of the atria
43
What is the physiological basis of the QRS complex?
depolarization of the ventricles
44
What is the physiological basis of the Q wave?
depolarization of the ventricle septum
45
What is the physiological basis of the S wave
depolarization of the base of the left ventricle
46
What is the physiological basis of the T wave
repolarization of the ventricles
47
What cardiac events are not visible on ECG?
repolarization of the atria and depolarization/repolarization of the conducting system
48
What does the PQ interval represent?
the time it takes an AP to go from the SA node to the ventricle. aka conduction time through the AV node
49
What does the QT interval represent?
time from onset of ventricular depolarization to end of ventricular repolarization
50
When are AV valves open?
when Patria> Pventricle
51
When do AV valves close?
Pventricle > Patria
52
When is the aortic valve closed?
Paorta > Pventricle
53
When is the aortic valve open?
Pventricle > Paorta
54
What are the two main phases of the cardiac cycle? and what events are they in reference to?
Diastole: ventricular relaxation
Systole: ventricular contraction
55
What are the 3 parts of diastole?
First 1/3:rapid filling with blood that has accumulated in the atria
Middle 1/3: filling with blood flowing straight from the venous return
Final 1/3: filling with blood from atrial contraction
56
Define isovolumetric contraction
the brief moment where the pressure n the aorta is higher than the ventricle, so the aortic and pulmonic valves are closed and the ventricles contract against a fixed volume
57
Define isovolumetric relaxation
once the ventricle starts to relax and the pressure falls below the aorta/pulmonary artery, the aortic/pulmonic valves close, and once again both valves are closed for a brief moment
58
Describe the cardiac cycle
Blood fills the artia, the pressure causes the AV valves to open, ventricles fill and the pressure causes AV valves to close, then once the ventricular pressure exceeds the aortic/pulmonary artery pressures the corresponding valves open and blood is pumped out of the ventricles
59
What is the difference in resting heart rates in individuals due to?
difference in vagal tone (PNS mediated control of the heart)
60
What is end diastolic volume?
the vol of blood in the ventricles at the end of diastole
61
What is end systole volume?
the volume of the ventricle at the end of systole
62
True/False: up to a certain limit, increase in EDV automatically results in a proportional increase in SV
true
63
What is Starlings Law of the Heart?
The intrinsic regulatory mechanism that enables the two ventricles to continuously adjust their stroke volumes to match each other. "more in=more out"
64
What is the main function of arterioles?
vasoconstriction/dilation to regulate blood flow into capillaries
65
What is the only thing that can be regulated to influence vascular resistance?
radius of the blood vessels
66
Where is the highest and slowest speed of flow in tube during laminar flow?
the slowest moving molecules are closest to the wall and the fastest is in the center of the tube
67
What is Reynolds number?
a dimensionless number that is used to predict whether blood flow will be laminar or turbulent
68
define MAP
mean arterial pressure is the pressure driving blood trough the tissues
69
define TPR
the resistance to blood flow exerted by the entire systemic circulation is called the total peripheral resistance
70
When is MAP closest to diastolic pressure?
at rest
71
When is MAP closest to systolic pressure?
at high heart rates because the diastolic phase is shortened more than the systolic phase when heart rate increases
72
Define pulse pressure
the difference between systolic and diastolic pressures
73
What is the amplitude of the pulse pressure dependent on?
heart rate and stroke volume, the elasticity of the arteries, and the total peripheral resistance
74
What are 4 factors that can affect arterial blood pressure?
-cardiac output
-total peripheral resistance (TPR)
-elasticity of the blood vessels
-blood volume (acute changes)
75
What 3 ways is can arteriolar diameter be regulated?
-Sympathetic innervation
-Neurohormonal regulation
-Autoregulation
76
Describe sympathetic regulation of arteriolar diameter
ending of nerve fibers release Norepinephrine, bind to alpha adrenergic receptors, depolarization, Ca2+ influx, vasoconstriction
77
Describe neurohormonal regulation of arteriolar diameter
occurs mainly via epinephrine and angiostensin II
-angeotensin II causes constriction of arterioles except in the brain and heart
-epinephrine constricts the arterioles in most organs through activation of alpha adrenergic receptors
78
What are the two types of autoregulation of arteriolar diameter?
metabolic and pressure
79
Describe metabolic autoregulation of arteriolar diameter
metabolic by products cause local vasodilation
80
Describe pressure autoregulation of arteriolar diameter
when arterial pressure falls, vascular smooth muscle cells in some organs relax and vice versa. only some organs are very sensitive to acute changes in blood flow
81
What are the roles of endothelial cells in arteriolar diameter autoregulation?
When the cells are affected by local changes such as pO2 and stretch, they release substances that act locally such as nitric oxide and prostacylin
82
capillaries contain what percent of circulating blood?
5%
83
why do capillaries have the slowest velocity of blood flow?
to allow sufficient time for gas exchange
84
What two things constitute the capillary wall?
basal lamina and a single layer of epithelium
85
What does capillary density correlate with?
rate of metabolism of the tissue
86
What is a pericyte and what is its purpose?
a cell that wraps around capillaries and communicate with the endothelial cells. they secrete substances that stimulate the endothelial cells to differentiate, multiply, and angiogenesis, they also regulate glomerular blood glow and store vit A in the liver
87
What are the 3 types of capillaries and where are they?
-Continuous: most common type
-Fenestrated: occurs in organs whose functions depend on extensive movement of material across capillary walls
-Discontinuous: large diameter capillaries with fenestrae large enough for cells and large proteins to pass through.
88
What is hydrostatic pressure in capillaries determined by?
by arterial and venous pressures and decreases along the length of the capillary
89
What is effective osmotic pressure (oncotic) of capillary blood due to?
presence of large plasma proteins
90
Why does capillary oncotic pressure oppose filtration?
because proteins cannot cross the endothelial wall of the capillary
91
normally, do capillaries favor filtration or absorption?
filtration
92
Under what capillary conditions will you have edema?
dilation of the arterioles (increasing hydrostatic pressure) or reduction in plasma proteins (decrease in oncotic pressure)
93
Under what capillary conditions is absorption favored?
constriction of the arterioles or reductions in arterial pressure
94
why is ~90% of the filtered fluid reabsorbed by the capillary eventually?
because hydrostatic pressure decreases down the length of the capillary but oncotic pressure remains the same so absorption is favored
95
What is the purpose of lymphatics?
overall function of the lymphatic system is to regulate the distribution of the extracellular fluid
96
how do lymphatics perform their functions?
lympatic capillaries possess one way flap valves that permit interstitial fluid and macromolecules to enter but not leave
97
where do lymphatic capillaries drain?
they eventually merge into the thoracic duct which empties lymph into large veins usually the internal jugular
98
Why must MAP remain within a relatively narrow range?
to preserve blood supply to vital organs and prevent damage to the heart and blood vessels
99
What is the SNS and PNS affects on chronotropy
(HR) occurs at the SA node
SNS: increases
PNS: decreases
100
What is the SNS and PNS affects on dromotropy
(conduction velocity) at the AV node
SNS: increases
PNS:decreases
101
What is the SNS affects on inotropy
(contractility) in the atria/ventricles
SNS: increases amount of Ca2+ on so a stronger contraction
102
What is the SNS affect on lusitropy?
(relaxation) in the atria/venticles
SNS: quicker Ca2+ resequestration
103
How does the baroreceptor reflex regulate arterial blood pressure?
allows for dynamic, moment-to-moment regulation
104
what two subsequent steps in the baroreceptor reflex allows for return to homeostasis of arterial blood pressure?
-change of radius of arteries (vascoconstriction/dilation)
-increase/decrease cardiac output
105
baroreceptors are mechanoreceptors that mainly operate at high pressure, which sensors are active at low pressure or small changes in pressure?
volume sensors
106
stimulation of volume receptors will result in what 3 effects?
-Direct effect: release atrial natriuretic peptide from atrial myocytes which increases natiuresis which reduces blood volume
-Direct effect:renal vasodilation, increased diuresis, reduced blood volume
- signal hypothalamus to decrease the production of vasopressin (aka antidiuretic hormone)
107
What occurs in the CV system when chemoreceptors are activated?
Primary effects is to increase pulmonary activity
Secondary effects is to stimulate CV activity, so increase SNS and thus increase MAP
108
what three hormonal pathways are involved in the long term regulation of MAP and blood volume?
-Renin-angiotensin-aldostrone
-ADH (vasopressin)
-Natriuretic peptides
109
Describe the short term and long term regulatory mechanisms of hemorrhage
-Initially arterial pressure drops so responses are aimed at maintaining perfusion to vital organs and normalize arterial pressure
-long term goal is to restore normal blood volume
110
what are the effects of vasopressin?
causes vasoconstriction and water reabsorption in kidney
111
what are 7 locally acting factors governing blood flow though capillary beds?
-Histamine
-bradykinin
-PGI2
-PGE2
-TXA2
-LTs
-NO
