Cardiology Flashcards
What is heart failure
Inability to maintain cardiac output
What is homeostasis for the CV system
blood pressure (120/80)
The heart is connected in [SERIES or PARALLEL] through pulmonary circulation
Series
The heart is connected in [SERIES or PARALLEL] to the systemic circulation
Parallel
Why is the heart connected to the pulmonary circulation in series
Decreased resistance, lowers pressure requirements and work load on the heart
Why is the heart connected to the systemic circulation in parallel
Increased resistance; separate control of blood flow to individual vascular beds depending on physiological needs of the organs
Total body water is what % of body weight
60%
Total blood volume is what % of body weight
7%
What % of blood is in the venous system
70%
What % of blood is in the artery system
10%
What % of blood is in the capillaries
5%
Another name for veins is
a) capacitance vessels
b) resistance vessels
c) exchange vessels
a) capacitance vessels
Another name for arteries is
a) capacitance vessels
b) resistance vessels
c) exchange vessels
b) resistance vessels
Another name for capillaries is
a) capacitance vessels
b) resistance vessels
c) exchange vessels
c) exchange vessels
Flow steadily ____________ going from arteries -> arterioles -> capillaries
decreases (increased resistance and decreased blood volume)
Flow steadily _____________ going from capillaries -> venules -> veins
increases (decreased resistance and increased blood volume)
What vascular bed has the greatest total surface area
Capillaries
4 mechanisms for venous return
- some smooth mm contraction
- skeletal mm contraction
- respiratory inspiration
- valves
Blood flows _________ is exposed to the ____________ SA and experiences the _____________ diffusion distances in capillaries, where the _____________ exchange takes place
Blood flows SLOWEST is exposed to the GREATEST SA and experiences the SHORTEST diffusion distances in capillaries, where the MOST exchange takes place
The greatest resistance is in
arterioles (50% of total pressure drop); due to the decreasing volume of blood
What is the pressure when blood reaches the vena cava
0 mmHg
What is stroke volume? What is a normal value
Volume of blood ejected from the left ventricle by 1 beat of the heart; 30 mls
What is cardiac output
Volume of blood circulated in one minute (L/min)
How is cardiac output related to stroke volume (equation)
CO = hr x SV
what is the relationship between resistance, pressure and flow
R = ΔP/Q
What is another way to describe flow? (hint: L/min)
CO (where CO = hr x SV)
What is TPR and what is a typical value
Total peripheral resistance = resistance in the systemic circulation (17 mmHg/L/min)
What is the typical resistance in pulmonary circulation
1.7 mmHg/L/min (note: low pressure low resistance since it is in series)
If pressure increases what happens to resistance
Increases
If flow increases what happens to resistance
Decreases
What is PP
Systolic - diastolic pressure
What is MAP
MAP = diastolic + 1/3 PP
What are two ways to calculate map
1) MAP = diastolic + 1/3 PP
2) MAP = CO x TPR
How is CO measured experimentally
a) direct fick
b) dye/indicator diluation
a)
How is CO measured clinically
a) direct fick
b) dye/indicator diluation
b)
How does dye/indicator dilution work
Input dye (cardiogreen) into venous system and measure it coming back through the arterial system
How do you calculate CO using dye/indicator dilution (what is the equation)
CO = (known amount of dye injected x 60)/ AOC x DFC
Describe Poiseulle’s law
R = 8nl/πr^4); where n = viscosity; l = vessel length; r = vessel radius
What are the implications of Poiseulle’s law
R = 8nl/πr^4; small changes in radius have a large impact on resistance
If vessel radius decreases what happens to resistance? What about if vessel radius increases
If vessel radius decreases, resistance will greatly increase; if vessel radius increases; resistance will greatly decrease (greatly = four-fold change)
If blood flow increases what happens to blood pressure
Decreases (locally)
As a vessel dilates, blood flow _________, blood pressure __________ and resistance _____________
As a vessel dilates, blood flow INCREASES, blood pressure DECREASES and resistance DECREASES
Turbulent flow is related to vessel ________________ and _______________ of blood
Vessel diameter; viscosity of blood
T/F Hydrostatic pressure = MAP
FALSE; HP is a capillary filtration pressure of water
Starlings forces equation
Starling’s forces = (Pc-Pt) - (πc-πt)
Is there net filtration or net reabsorption between arterial and venous ends
Typically net filtration
Where does lymph empty
Subclavian veins
What are the four causes of edema
- increased filtration pressure (HPc)
- decreased oncoticpressure gradient (πc)
- increased capillary permeability
- decreased lymphatic flow
What is an example of an activity that increases VDMs and therefore triggers metabolic autoregulation
exercise (causes hyperthermia, hypoxia, acidosis and hypercapnia)
What are the two types of autoregulation
metabolic and myogenic
Humoral control mechanisms involve
Vasoconstrictor agents and vasodilator agents
3(4) vasoconstrictors are
Epinephrine, norepinephrine, angiotensin II (-> aldosterone)
Vasoconstrictors do what to flow and pressure
increase pressure, decrease flow
Vasodilators do what to flow and pressure
decrease pressure, increase flow
What are the three effects of stimulating a baroreceptor (ex. increased stretch due to bolus of blood entering aorta)
- decreased sympathetic output to blood vessels, heart and medulla (due to an inhibitory signal from the CVLM to the RVLM)
- increased parasympathetic output to the heart (due to a stimulatory signal from the NTS)
- increased stimulation of vagus (CNX) and glossopharyngeal (CNIX)
OVERALL: decreased hr and decreased bp
How do we get hypo/hypertension
Resetting of baroreceptors due to changes in mean blood pressure
What does the P wave represent
atrial depolarization
What does the QRS complex represent
atrial repolarization/ventricular depolarization
what does the T wave represent
ventricular repolarization
What is systole
Contraction phase; ventricular emptying
What is diastole
Relaxation phase; ventricular filling
What makes the lub sound
Closing of the AV valves; systole
What makes the dub sound
Closing of the aortic/pulmonic valves; diastole
What is the equation for SV, EDV and ESV
SV = EDV - ESV
What is diastasis
Period of diastole in which filling of the ventricles is almost at a standstill, before atrial contraction
Is the ventricle ever fully empty
No; ESV dictates the emptiest the ventricle gets
What causes the dicrotic notch
Backflow of blood in aorta prior to closure of the aortic valve
What makes the third heart sound
When blood flows into almost empty ventricles during diastole
What are the three types of myocardial cell fibres
- atrial
- ventricular
- excitatory/conductive
What separates the atrial and ventricular syncytia
Valvular tissue
What part of the conduction system is fastest
Purkinje
What are three ways to control the SA node firing
- slope of pre-potential
- threshold for firing the AP
- change RMP
T/F there is a prepotential in cardiac muscle
F
T/F there is a prepotential in excitatory cardiac tissue
T
What is the RMP of conducive cells
-55 mV
Describe calcium-induced-calcium release
AP depolarizes the sarcolemma -> voltage-gated Ca channels in cytoplasm open and influx of calcium -> this calcium triggers release of Ca from the sarcoplasmic reticulum. NOTE: this is in addition to depolarization of sarcolemma -> AP travels down transverse tubules to sarcoplasmic reticulum -> release of calcium
What is preload
equal to EDV; amount of filling of the ventricle before contraction
What is afterload
resistance against ventricular emptying ; equal to the pressure in the vessel that the ventricle is trying to empty into (80 mmHg)
What determines changes in SV
preload, afterload, ANS
What determines the performance of the heart (CO)
Changes in hr; changes in SV
chronotropic
affects heart rate
inotropic
affects heart contractility
how does the vagus nerve decrease hr/contractility
Ach acts through muscarinic receptors to increase K permeability; hyperpolarization of cells (LOWERS RMP)
how does the SNS increase hr/contractility
NE acts through β-adrenergic receptors to increase permeability for Na and Ca; decreases conduction time (INCREASES RMP)
What is the Frank Starling Law and what does it relate to
The greater the EDV, the greater the quantity of blood ejected during systole (due to being in an ideal state of overlap between filaments); has to do with preload and contractility
With increased preload, stroke volume [increases/decreases]. Why?
increases; due to increased length of muscle fibers and maximal overlap
What will happen to systolic pressure with increased preload
Will increase beyond 120 mmHg
What happens to SV if afterload increases
If afterload increases, SV decreases initially, but then returns to normal due to increased EDV (which subsequently increases SV)
syncope
collapse
Which of the following can an ECG not be used to diagnose in LA species:
1) rhythm in a patient with abnormal rhythm or rate
2) chamber enlargement
3) electrolyte imbalances
4) myocardial ischemia/hypoxemia
5) drug intoxication
6) thoracic or pericardial effusion
2) chamber enlargement
What is the standard position for an ECG
right lateral recumbancy (note: rhythm diagnosis can be done in any position)
What lead is not always needed in an ECG
RL (always want RA, LA, LL)
Arrhythmias are typically diagnosed with which lead
Lead II
What does Lead I detect
RA - LA
- potential difference across SA node and atria
- top of the heart
What does Lead II detect
RA - LL
- potential difference across atria, nodes, ventricles, conduction, valves
- whole heart
What does Lead III detect
LA - LL
- electrical difference across ventricle
T/F in all animals a negative T wave is normal
False; normal for small animals but indicates ischemia in horses or humans
What does the PR interval represent
Conduction of AP from atria to ventricles
What does the Q wave represent
Septal depolarization
What does the QT interval represent
Duration of ventricular systole, including ventricular repolarization
What is a normal sinus rhythm
Rhythm that arises from the sinus node and travels normally down to the ventricles
Signs of normal sinus rhythm
P wave in front of every QRS
P wave positive on lead II
Regular PR interval
What causes sinus arrhythmia
Hering-Breuer reflex: stretch receptors in lungs influence vagal innervation of sinus node
On ECG you see no P wave, what does this indicate
SA node block
On ECG you see a prolonged PR interval, what does this indicate
First degree AV block
On ECG you see a prolonged PR interval and occasional drop beats (missing QRS complexes), what does this indicate
Second degree AV block
On ECG you see no association between the P wave and QRS-T complexes, what does this indicate
Third degree AV block
What causes 1st degree AV block
High vagal tone or conduction system disease (mild)
What causes 2nd degree AV block
High vagal tone or conduction system disease (moderate)
What causes 3rd degree AV block
Conduction system disease (severe)
In third degree AV block what is responsible for ventricular contraction
Purkinje only (see a very slow heart beat)
what is ventricular escape
strong vagal tone can completely stop signals from SA node, in which case AV and Purkinje take over
