Review Questions Flashcards
What are the 2 main divisions?
pulmonary (low pressure) and systemic (high pressure)
What are the 4 components of each division?
Describe each
Pump: generates energy (atria and ventricles)
Distribution: arteries and arterioles
Exchange: capillaries, via diffusion and ultrafiltration
Collection reservoir: venules and veins (80%)
Define: Blood Flow
volume of blood that moves past a particular point per unit time
F = (P1-P2)/R
What are the two components that determine flow?
blood pressure and resistance
What are the three factors that contribute to changes in pressure?
frictional forces, vessel diameter, vessel length
What is the point of having direct electrical coupling between myocardial cells?
to allow for rapid impulse conduction and depolarization across the myocardium
How is the cardiac action potential different from a skeletal action potential?
it is much broader
Describe the autonomic and hormonal control of the cardiac system.
Preganglionics: nicotinic, acetylcholine
Postganglionic: muscarinic (para), acetylcholine, alpha or beta adrenoreceptors, norepinephrine
Hormones: RAAS, vasopressin, epinephrine (adrenal medulla)
The resting membrane potential (RMP) of cardiac myocytes is primarily a function of __________. This ion is drawn into the cell by the presence of ________.
its high permeability to K+ and low permeability to other ions (Na+ and Ca2+)
large negatively charged proteins (A-)
What happens to the resting membrane potential (RMP) when you: increase extracellular K+
increases (depolarization)
What happens to the resting membrane potential (RMP) when you: increase extracellular Na+
no change (because channels are closed; will lead to a higher peak potential when channels do open)
What happens to the resting membrane potential (RMP) when you: increase extracellular Ca 2+
no change
Why is the myocardial action potential so much longer than skeletal muscle?
there is an influx of Ca 2+ during depolarization in addition to the Na+ and, Ca 2+ channels open and close slowly compared to Na+
What are two types of AP’s and where are each of them found?
Fast type: atrial and ventricular myocytes and Purkinje fibers; rate of rise is fast due to fast type Na+ channels
Slow type: pacemaker cells of SA and AV nodes; conduction velocity slow due to “funny” type Na+ channels
Describe the 5 phases of fast type action potentials
Phase 0: Rapid depolarization- rapid influx of Na+ (fast type channels numerous on myocardial cells, open/close quickly)
Phase 1: Transient repolarization- Na+ channels rapidly close and K+ currently activated
Phase 2: Plateau phase- slow type Ca 2+ channels begin to open and large influx into cell, gradually close
Phase 3: Rapid repolarization- K+ flows out as channels open, hyperpolarization
Phase 4: Resting membrane potential- previous changes fixed by Na+/K+ ATPase, Ca 2+ changes fixed by both Na+/Ca 2+ exchanger and reuptake of Ca 2+ into sarcoplasmic reticulum
What is the point of an extended refractory period?
allows for adequate filling time and enough time for sufficient Ca 2+ reuptake