Cardiology part III
Terms
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- P wave
- depolarization of atrial muscle
- PR-interval
- first atrial depolarization to first ventricular depolarization
- QRS interval
- ventricular depolarization
- T wave
- ventricular repolarization
- ST-segment
- all of ventricle depolarized
- QT-interval
- first depolarization to last repolarization of ventricle
- T/F current must flow in a closed loop
- T
- 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
- LA - RA
- Lead II
- LL - RA
- Lead III
- LL - LA
- 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
- hypothalamus
- behavioral and emotional effects on blood pressure are generally processed here
- what is the primary regulator of blood pressure over the short term?
- baroreceptors
- 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 - ANP
-
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
-
compliance
- 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
OR
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
- SV = EDV - ESV
- 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?
- RA
- Which starts first? LV or RV contraction?
- LV
- Which ends first? LV or RV contraction?
- RV
- what value does pulmonary capillary wedge pressure measure?
- LAP
- S1
- closing of AV valves
- S2
- closing of semilunar valves
- S3
- blood vibrating ventricular walls as during filling
- S4
- 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
- 0.55
- 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
- 5-20%
- atropine fxn
- Acetylcholine (ACh) released by postganglionic parasympathetic nerves terminals interacts with muscarinic (M2) receptors in the heart. These receptors are blocked by atropine.
- propanolol
- 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?
- Yes
- 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)