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Cardiology part III


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P wave
depolarization of atrial muscle
first atrial depolarization to first ventricular depolarization
QRS interval
ventricular depolarization
T wave
ventricular repolarization
all of ventricle depolarized
first depolarization to last repolarization of ventricle
T/F current must flow in a closed loop
einthoven's triangle
right arm, left arm, and left egg form an equilateral triangle in the frontal plane with the heart in the center
Lead I
Lead II
Lead III
amplitude and sign of lead voltage depend on:
(1) magnitude and diirection of the dipole vector

(2) angle between the lead and the dipole vector
geometric considerations require which two relationships to be true about triaxial and hexaxial systems?
II = I + III

aVR + aVL + aVF = 0
what do arterial peripheral chemoreceptors do?
increase respiration in response to decreases in oxygen tension and increases in CO2 tension.
ischemic response
- blood flow to vasomotor center dec to ischemia, VC becomes strongly excited and there is strong activation of the sympathetic tetrology -- inc CO, inc TPR, inc Pa
Cushing reaction
inc CSF pressure --> ischemic response
behavioral and emotional effects on blood pressure are generally processed here
what is the primary regulator of blood pressure over the short term?
what is the primary regulator of blood pressure over the long term?
RAA system
RAA system
renin-angiotensin-aldosterone system

the skinny:

decreased arterial pressure leads to decreased renal perfusion pressure, which leads kidney to release renin. Renin changes angioteninogen to angiotensin-I. ACE changes A-1 to A-2. A-2 stimulates the release of aldosterone from renal cortex and constricts arterioles (including in kidney). Aldosterone increases rebsorption of Na+, inc BV, inc Pa
atrial nutriuretic peptide

found in atria of heart

released by increases in atrial pressure

suppresses the release of renin
Pressure, flow, resistance eqn
R = delta-P / Q
- eqn
- change with age
Ca = dV/dP
- decreases with age (i.e. less volume change per change increase in pressure)
velocity of blood flow eqn
Q = A x v


v = Q / A
Poiseuille's law
R = ?
R = 8ηl/Ϭr4
Law of Laplace (sphere)
- eqn
- define variables
P = 2HT / r

P = pressure
H = sphere wall thickness
r = sphere radius
T = Tension
Law of Laplace (cylinder)
- eqn
- define variables
T = Pr / w

T = circumferential wall tension
P = transmural pressure
w = sphere wall thickness
Stroke Volume eqn
Ejection Fraction eqn
Ejection Fraction = SV / EDV
Cardiac Output eqn
CO = SV x HR
stroke work eqn
SW = P x SV
minute work eqn
Minute work = P x SV x HR = P x CO
Reynold's number
- eqn
- what are the factors that alter Reynold's number
NR = ρdv/η

Reynolds number above 2000 can create turbulent flow. Conditions that promote turbulent flow are large diameter, high velocity, and low viscosity
what is the major effect of changes in HR to the stages of the cardiac cycle?
duration of diastasis, inversely proportional
which occurs first? RA or LA contraction?
Which starts first? LV or RV contraction?
Which ends first? LV or RV contraction?
what value does pulmonary capillary wedge pressure measure?
closing of AV valves
closing of semilunar valves
blood vibrating ventricular walls as during filling
rapid filling of ventricle by atrial systole
above and below which temperatures is temp regulation lost?
< 84 °F
> 106 °F
what is the most accurate measure of body core temperature?
mixed venous blood --> approx by temp of esophagus at level of heart
thermal neutral zone
ambient temperature range over which the normal body temp is achieved without the activation of metabolic and evaporative processes
sources of heat input
environment, metabolism
mechanisms for heat loss
radiation, convection/conduction, evaporation
Describe how infections produce fevers.
macrophages or B-lymphocytes phagocytize foreign organisms à also activates gene for interleukin-1 (IL-1) --> IL-1 carried to anterior hypothalamus --> activates phospholipase A2 --> arachiodonic acid released from plasma membranes --> cyclooxygenase initiates rxns which produce prostaglandins --> prostaglandin E2 shifts the temp set point in the anterior hypothalamus
Give the APDs for the H-P system, the ventricle, atria, and AVN/SAN
The action potential duration is longest (350-400 ms) in the His-Purkinje system; ~250 ms in ventricle and 150 ms in atria, AVN and SAN
typical ejection fraction for 70 kg person
typical cardiac output for a 70 kg person
5 L/min
transmural pressure
intravascular pressure - extravascular pressure
what is turbulence generally associated with?
Turbulent flow is generally associated with rough surfaces (e.g., damaged endothelium), bifurcations (branches, especially in large vessels with high blood velocity), and valves (i.e., between heart chambers).
cardiac efficiency
atropine fxn
Acetylcholine (ACh) released by postganglionic parasympathetic nerves terminals interacts with muscarinic (M2) receptors in the heart. These receptors are blocked by atropine.
non-selectivie beta-blocker
what effect does ACh have on the atrium?
Parasympathetic Stimulation (ACh) Increases CV = + Dromotropic Effect
Is APD dependent on conduction velocity? dependent on HR?
APD is independent of conduction velocity &
inversely related to HR
does tetanic stimulation increase contractile force in skeletal muscle?
does tetanic stimulation increase contractile force in cardiac muscle?
No, the long refractory period prevents this.
what does acetylcholine do to atrial conduction velocity?
increases it (increase I(K1), hyperpolarizing Em, and thus increases CV)

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