Cardiovascular Function Flashcards
Where is the majority of the blood contained in the systemic component?
Veins (50-60%)
What is the primary force for moving blood around the circuit?
left ventricle
What is the purpose of the arteriolar smooth muscle tone?
modulates resistance, pressure, and flow
T/F Arteriolar constriction occurs everywhere in the body.
False - there is no arteriolar constriction in the CEREBRAL + CORONARY circulations. Here, the perfusion is entirely dependent on BP
What are the 3 main arteries of the heart, and what do they supply?
LAD = anterior wall + anterior septum
LCX = lateral wall of L ventricle
RCA = R ventricle + inferior wall of LV + posterior septum
What supplies the SA/AV Node?
RCA
What is the purpose of the carotid sinus massage?
mechanically generated pressure increases pressure in the vessel. This sends afferent signals to the vagus, which sends efferents to decrease sympathetic discharge to the LV to lower SA/AV node firing. This ultimately lowers systemic BP.
Where are systemic efferents distributed?
blood vessels + heart
What are P cells? What are His purkinje cells?
How are they different in terms of electrical resistance?
P cells = autorhythmic with undifferentiated cell junctions (high electrical resistance).
His-Purkinje cells = fibers that arise from the AV node that distribute to the subendocardial layers of ventricles; connected via gap junctions (low electrical resistance)
Myocardial function is comprised of these two independent functions. What are they and what ions govern these processes?
1) Systolic ventricular function - ability of LV to contract; dependent on Ca INFLUX (ionotropy)
2) Diastolic ventricular function - ability of LV to relax; dependent on Ca EFFLUX (lusitropy)
Myocardial contraction is determined by?
1) preload
2) afterload
3) contractility
What is starling’s law of the heart?
increase in Preload (LV diastolic volume) –> increase in LV fiber tension/shortening –> increase CO/SV
What is preload?
initial length of the myocardial fiber, determines how much tension the fiber has to develop.
What is contractility?
What does it depend on?
How is it modulated?
How can it be improved?
intrinsic components of myocardial contraction that is independent of initial fiber length.
Depends on the rate/amount of intracellular Ca influx.
Can be modulated by + ionotropic agents (ie b-adrenergic agonists/digitalis)
Can be improved by decrease in SVR
What does a vasodilator like adenosine do to contractile performance? What does it modulate to do so?
Adenosine/vasodilator
- > Decrease peripheral arteriolar constriction
- > Decrease SVR + preload
- > increase contractile performance
What is afterload?
What modulates it? (3)
How is it measured?
tension developed by a muscle fiber after it starts to contract.
modulated by preload, iontropy, and SVR
measured via systolic BP + EDV
What is the major determinant of myocardial oxygen requirement?
afterload, since TENSION development requires more energy than fiber shortening
What is the Law of LaPlace and how does it relate to O2 consumption?
P = T/r
an increase in heart size (preload) increases oxygen consumption because it requires more tension development to generate the SAME pressure. The heart compensates for the increase in tension development by increasing the thickness of the myocardium (hypertrophy)
What 3 things determine diastolic filling?
LV filling pressure, LV elastic recoil, LV compliance
decrease compliance = increase filling pressure
What is the atrial kick?
atrial contraction that forces additional blood into the ventricles Immediately BEFORE ventricular contraction.
What is pulmonary wedge pressure a measure of?
LA pressure = LV diastolic filling pressure (estimate of preload), which determines LV preload
What is a CXR used for? (2)
What is an ECHO used for? (5)
CXR = cardia enlargement, flow distribution (edema, redistribution, etc)
ECHO = measure of chamber size, wall thickness, systolic/diastolic volumes, ejection fractions, contraction abnormalities (diffuse kinesis/dyskinesis)
What is the EF a measure of?
measure of LV function, or ability of LV to contract
What is the sympathetic squeeze?
systemic venoconstriction induced by systemic stimulation in response to hypotension = BAROREFLEX; represents the combined arteriolar + venous constriction
What 3 factors govern circulation?
Total blood volume (input + renal fxn)
Cardiac function (CO = HRxSV)
Peripheral vascular tone (venous + arteriolar tone)
What is the short and long term responses to cardiac stresses (volume, pressure, underloading)?
short: sympathetic stimulation via baroreflex
gradual: salt/h2O retention via RAAs
long: cardiac hypertrophy via synthesis of extra sarcomeres
What is the hypertrophic response to volume load? pressure load?
Volume load = ECCENTRIC hypertrophy
Pressure load: CONCENTRIC hypertrophy
What does the Valsalva manuever do?
reduces preload since the forced exhalation against a closed glottis results in increased intrathoracic pressure, which decreases the amount of blood flow to the RA and LV (decreased venous return) and ultimately leads to:
decrease preload
How does temperature affect the circulation/oxygen requirements of the heart?
COLD = vasoconstriction of cutaneous vessels redirects flow to systemic circulation –> increase afterload –> increase O2 requirement for LV contraction
HOT: vasodilation of cutaneous vessels –> decrease preload –> decrease O2 requirement to pump reduced load out of the heart
How does weight lifting vs cardio exercise affect the heart?
weight lifting (strength, isometric) –> higher BP required to force blood through the tensed muscles = increase pressure load = concentric LVH
cardio (endurance, dynamic) –> vasodilation increases volume load –> ECCENTRIC hypertrophy
What does orthostatic hypotension do to preload? hemorrhage? hot temperature?
all decrease preload
