Cardiovascular Flashcards
Define the SA node
generates impulse, spindle shaped,20 mm long, 3 mm wide at the junction of superior vena cava and the RT. atrium, 1 mm below epicardium
The AV node is located …
1 mm below the RT. atrium endocardium, anterior to the ostium of the coronary sinus
Why AV node conduction is slow?
to allow the atria enough time to finish its contraction
what is the effect of sympathetic stimulation on AV node?
speeds up conduction and decrease refractory time.
* parasympathetic stim. has an opposite effect
Define the His-Purkinje system (ventricular conduction)
comprises His bundle, bundle branches & purkinje fibers altogther.. It has fast conduction speed. Made up of purkinje cells
The bundle branch is divided into ….. & ….
RBB (thin), & LBB (thick)
* LBB is further divided to ant. thin, and post. broad
What is the function of Purkinje fibers?
penetrate the ventricular myocardium to depolarize the muscle cells
The nexus (gap) in the …….. is used…..
intercalated discs
to low resistance electrical connection
The RMP for AV and SA node is …., while for the purkinje & cardiac muscle cells ….
- 70 mV (slow fibers)
- 90 mV (fast fibers)
- The inside is more negative with respect to the outside
Conduction speed depends on ….., …… & …..
protein content, diameter of the fiber, presence of gap junctions (e.g His-Purkinje system)
Automaticity is ….
ability to depolarize toward threshold automatically
* Cells with automaticity can function as pacemakers
Effective refractory period is …..
Relative refractory period is ……
- the interval during which AP can not be elicited no matter how strong the depolarizing stimulus
- The interval in which AP is elicited in response to a stimuli stronger than the needed to depolarize a resting cell
During AP, Ca enters the cell through …..
voltage gated L type Ca channels
* Ca leaves the myocell via Ca-Na exchange
At the Z line of the sarcomere, ….. extend to the interior of the myocardial fiber
T tubules (invagination of the sarcolemma)
What is the Ca induced Ca release?
The entry of Ca will cause the release of large amount of Ca from the sarcoplasmic reticulum, providing sufficient amount to initiate contraction.
* Still, it relies more on extracellular Ca than skeletal muscles
Sympathetic stim. and beta agonists increase ….. , so it increases the contraction force
the probability that a Ca channel is open which increase Ca influx
How is the myocardium relaxes?
- Stop Ca influx by closing the channels
- the endoplasmic reticulum actively reduces intracelluar Ca (ATPase activity)
- Troponin and tropomyosin restore their inhibitory configuration
Prolonged contraction is possible in cardiac muscle. T/F
False. unlike skeletal muscles, relaxation is part of the cardiac cycle
Skeletal muscles change in contractile force is due to ……
While for the cardiac muscle, is due to ….
change of number of fully activated fibers
change in contractility of all fibers
Atrial kick is ….. .
atrial systole (150 milisec)
* ECG P wave just before actual contraction
* EDV is max (120 mL), EDP is max (but below atrial)
* Left atrial pressure: a wave
* S4 is heard in pathologic condition
see p. 409
Mitral valve closure defines ….. . It occurs …… the tricuspid valve closure. Atrial pressure slightly ….. due to …..
the beginning of the isovolumetric contraction
before
increase c wave, bulging of the mitral into the left atrium
The loudest heart sound is …..
S1
Aortic valve opening marks ….. . It occurs …… the pulmonary valve
the beginning of the ventricular ejection
after (isovolumetric contraction is longer in the left ventricle)
V wave shows the ….
increase in atrial pressure due to refilling
* mitral is closed