Test Three Flashcards
What is the normal blood volume in adults?
5 L
How does blood move through vessels?
Bulk flow
What happens when aortic pressure excedes that of the ventricle?
The aortic semilunar valve closes
When does the aortic semilunar valve open?
When left vent pressure exceeds aortic
What causes S1 and S2?
S1: closing of the AV valves
S2: closing of the SL valves
Which semilunar valve is most anterior?
Pulmonary valve
What causes mechanical events in the heart?
Electrical events- SA and AV node actionpotentials
What is a syncytium?
Fibers of the ventricles and separately fibers of the atria are functionally connected to rapidly spread action potentials
How does deoplarization occur in the SA node?
Gradually, after an AP the membrane potential returns o resting and gradually starts to depolarize again
What is a pacemaker potential due to?
Leakiness of sodium and other ions
All cardiac muscle cells are excited at the rate of the ____.
fastest one
What is an ectopic pacemaker?
When the pacemaker is not located in the SA node, another part of the heart develops a rhythm faster than the SA node
T or F: The atria contract at different times?
False the atria contract at relatively the same time, the AP spreads via gap junctions
How does an AP travel down to ventricles?
The SA node signal reaches AV node and it spreads through the AV buncle (bundle of his), through the left and right bundle branches to purkinjie fibers. The AV node is responsible for the delay in contraction between atria and ventricle.
P wave?
depolarization of atria
QRS Complex?
Deoplarization of the ventricles
T wave?
Repolariztion of ventricles
EKG’s record what kind of potential difference?
Extracellular recordings of leaking currents through the ECF from cardiac cells depolarizing or repolarizing
PR interval?
“pause” between depolarization of atria and the ventricles
QT interval?
Time during ventricular contraction where they are generating force
What is second degree heart block?
Skipped ventricular depolarization, no QRS complex,
What is third degree heart block?
QRS and P waves are are off beat
What causes the initial rising phase of an AP
sodium ions
The initial deoplarization causes what kind of channels to open and where?
Slow voltage gated calcium channels in the t tubules which results in plateau of depolariztion
Does intracellular calcium or extracellular calcium bind to troponin?
Intracellular, extracellular calcium causes the release of calcium from the sarcoplasmic reticulum
What muscle has a longer refractory period, skeletal or cardiac?
cardiac
How does premature ventricular contraction occur?
If the ventricle fires before the SA node, but after the refractory period. This could cause the SA node to fire during the refractory period resulting in no contraction
Systole?
Contraction divided into isovolumetric ventricular and ventricular ejection
Diastole?
Relaxation divided into isovolumetric ventricular relaxation and ventricular filling
When does the bicuspid valve open?
when atrial pressure is greater than ventricle
What is the first stage of systole?
Period of isovolumetric ventricular contraction both valves are closed and pressure is building to open the pulmonary or aortic semi lunar valve.
Second stage of systole?
Ventricular ejection
What marks the end of of isovolumetric contraction and beginning of ejection?
Opening of the aortic valves for ejection
How does ejection occur?
For the first half of vent ejection the pressure is rising and volume is falling, this works because the walls are powerful enough to squeeze the rest of the blood in the ventricles. During the second half the vent contraction weakens and prssure falls due to the weaker contraction and less blood volume, blood is ejected at a slower rate
What happens to the aorta during ventricular ejection?
Pressure rises, but not enough to close the valve bc vent pressure is also rising. Half way through ejection the rate of blood leaving and entering aorta is the same. Near end of systole aortic pressure falls bc the amount of blood leaving is greater than amount pumped in.
When does the systemic system start and end?
Left side of the heart and ends in the right side
Ventricular pressure begins to ___ immediately after the production of the QRS wave because ___.
rise; the ventricular fibers have become excited and began to squeeze in on the blood within the ventricle
Frank starling law states that ___ ventricular filling leads to a direct increase in____.
Increased; stroke volume
During the period of isovolumetric contraction the volume of blood in the left ventricle is___.
not changing because both the AV valve and SL valve are closed
What is the first stage of diastole?
isovolumetric ventricular relaxation
What marks the end of systole and beginning of diastole?
aortic valve closing producing S2
What is the incisura?
A bump on the aortic pressure curve when blood rebounds against the semilunar valve, a brief surge of pressure increase
When would the incisura and S2 occur?
Nearly the same time because the semilunar valve closing causes both
What marks the end of isovolumetric ventricular relaxation?
Opening of the bicuspid valve
What is CO?
CO=HR x SV
Volume of blood pumped by each ventricle per unit time
What is stroke voulme?
volume of blood ejected by each ventricle during each contraction.
Avg SV is 70
EDV-ESV=SV
What does parasympathetic stimulation to the SA node done and what is released?
Ach and it slows the heart rate down
What occurs when epinephrine and norepinephrine stimulate the heart?
Speeds it up
How does the release of Epi, Norepi, or Ach work on the heart?
They change the permeability of SA node cells to ions changing the slope of gradual depolarization
What is one way congestive heart failure occurs?
dysfunction of the left ventricle- doesn’t pump enough out and blood backs up into the left atrium and then pulmonary veins and capillaries resulting in congested lungs
Where would edema occur in right sided heart failure?
Systemically
How can sympathetic nerves and circulating epi increase SV?
By acting on other areas in the heart that aren’t the SA node
An increase in contractility leads to ___.
more complete ejection of the EDV
What is ejection fraction?
ratio of stroke volume to EDV
EF=SV/EDV
What is afterload?
increased arterial BP that decreases SV because the arterial pressure is what the ventricle has to work against to eject blood.
What has a direct effect on CO?
SV and Heart rate
What has a direct effect on SV?
EDV
Plasma epi
Sympathetic activity
What has a direct effect on heart rate?
parasympathetic activity, sympathetic activity, and plasma epi
What pressures do the aorta and large arteries transport blood under?
90-100 mm Hg
What is the function of arterioles?
main control site for blood flow and major site of resistance to flow
What is the function of capillaries?
Major site of water and solute exchange between blood and tissues
Where can a pulse be found?
only in arteries and arterioles
Mean Arterial Pressure can be estimated how?
MAP=Diastolic pressure + (pulse pressure)(1/3)
pp= 120-80
Why is the MAP not the halfway value ?
because diastole lasts longer that systole
Describe laminar flow?
blood flow in streamlines with each layer of blood the same distance from the wall, also silent
What is turbulent flow?
When blood flows crosswise and causes murmurs
What happens if you decrease the diameter of a vein?
you increase flow
What happens if you decrease diameter of an artery?
you decrease flow