Cardiovascular - physio, heart failure Flashcards
CO equation
SV X HR
SV = end-diastolic volume - end-systolic volume
CO left heart = CO right heart
MAP equation
1/3 SBP + 2/3 DBP or (SBP + 2 DBP)/3 or DBP + (SBP-DBP)/3
4 humoral vasoconstrictor agents and 4 humoral agents causing vasodilation of arterioles
- Norepinephrine, epinephrine, angiotensin II, vasopressin, serotonin, thromboxane A2
- Bradykinin, histamine, prostaglandins (prostacyclin and E-series prostaglandins)
(bradykinin and histamine cause VENOUS vasoCONSTRICTION) - histamine also increases capillary permeability
Blood flow equation
Q = (MAP - right atrial pressure) / total peripheral resistance
Poiseuille’s law
R = (8 * n * l)/ (pi * r^4)
Phases of ventricular action potential and ion currents
Phase 0 = depolarization = inward Na+
Phase 1 = early repolarization = outward K+
Phase 2 = plateau = inward Ca2+ and outward K+
Phase 3 = repolarization = outward K+
Phase 4 = resting membrane potential
Phases of SA node action potential and ion currents
Phase 0 = upstroke (depolarization) = inward Ca2+
Phase 3 = repolarization = outward K+
Phase 4 = slow depolarization = inward Na+ (funny current If)
No phase 1 and phase 2
Similar for AV node
Name the sympathetic and parasympathetic neurotransmitters and receptors on the heart
Sympathetic: catecholamines (norepinephrine) on beta1-receptors (Gs receptors)
- increases Ca2+ inward current during the plateau of the action potential –> increase contractility
Parasympathetic: acetylcholine on muscarinic receptors (Gi receptors)
- Decreases the inward Ca2+ current during the plateau
What are the parasympathetic receptors on the vessels and what is their action
Muscarinic M2 receptors located on the endothelial cells -> lead to NO release and vasodilation (mostly venous)
Describe phases of a normal ECG
- P wave = atrial depolarization
- PR interval = conduction velocity through AV node
- QRS = ventricular depolarization
- ST interval = period when ventricles are depolarized
- T wave = ventricular repolarization
Atrial depolarization is buried in the QRS complex
Draw the left ventricle pressure-volume loop with phases of the cardiac cycle and closing / opening of valves. Show the effects of increased preload, increased afterload, increased contractility
Increased preload -> increased end-diastolic volume
Increased after load -> increased pressure at beginning of and during ejection + increased end-systolic volume (decreased stroke volume)
Increased contractility -> increased pressure during ejection with decreased end-systolic volume (increased SV)
Draw the cardiac function curve and systemic vascular function curve. Describe the parameters influencing each curve.
Parameters affecting cardiac function: preload, afterload, contractility
Parameters affecting systemic vascular function: systemic vascular resistance, blood volume, venus compliance
Which compartment contains stressed vs unstressed volume?
Stressed volume = blood volume contained in the arteries
Unstressed volume = blood volume contained in the veins
- the veins contain the highest proportion of the blood in the CV system
Where is the highest resistance in the vascular system?
Arterioles
Describe each component of the vasculature with one term
- Arteries = conduit vessels
- Arterioles = resistance vessels
- Capillaries = exchange vessels
- Veins & venules = capacitance vessels
What are the 4 determining factors of transcapillary diffusion rate?
- Concentration difference
- Surface area for exchange
- Diffusion distance
- Capillary permeability
How is arteriolar resistance regulated?
By the autonomic nervous system
- α1-Adrenergic receptors are found on the arterioles of the skin,
splanchnic, and renal circulations.
-> vasoconstriction - also found in the veins
- β2-Adrenergic receptors are found on arterioles of skeletal muscle and coronaries.
->vasodilation
Velocity equation
V = blood flow / cross sectional area
Higher in the aorta than the sum of all capillaries (optimizing conditions for substance exchange)
When considering Poiseuilles’s law, which factors influence resistance and how do they do it?
- Viscosity - Resistance is directly proportional to viscosity
- Length of blood vessel - Resistance is directly proportional to length
- Radius of blood vessel - Resistance is inversely proportional to radius (to the power of 4! Huge influence on resistance)
Name the 2 main mechanisms of BP regulation and give their respective timing
- Baroreceptor reflex (very acute, min to min) - neurally mediated
- Renin-angiotensin-aldosterone system (slow, long-term) - hormonally regulated
Label Wiggers diagram
See picture
Label CVP curve (or right atrial pressure curve)
See picture
- normal CVP is 0-8 cm H2O
What are the normal pressures within each compartment of the heart?
- Aorta: 120/80
- LV: 120/0
- LA: 5/0
- RA: 5/0
- RV: 30/0
- PA: 30/10
Where are the baroreceptors located
Carotid sinus (mostly) + some additional in aortic arch (responding to increases in BP only)