Chapter 5A, 2 Flashcards
Cardiac ….: cardiac events that occur from the beginning of one heartbeat to the
beginning of the next.
cycle
- A cardiac action potential arises in the SA node, continues down to the AV node. As the atrial contractile fibers depolarize, the ….. appears in the ECG.
p wave
The cardiac cycle consists of a period of relaxation called ….stole, during which the
heart fills with blood, followed by a period of contraction called …tole
dia
sys
- After the P wave begins, the atria contract (atrial
…tole). Conduction of the action potential slows at the AV node because the fibers there have much smaller diameters and fewer gap junctions. The resulting delay gives the atria time to contract, thus adding to the volume of blood in the ventricles, before ventricular systole begins.
sys
(P wave ends)
- The action potential propagates rapidly again after entering the AV bundle. After the P wave, it has propagated through the bundle branches, Purkinje fibers, and the entire ventricular myocardium.
Re/depolarization progresses down the septum,
producing the …… At the same time, atrial
re/depolarization is occurring, but it is not usually evident in an ECG because the larger QRS complex masks it.
depolarization
QRS complex
repolarization
- Contraction of ventricular contractile fibers (ventricular …tole) begins shortly after the QRS complex appears and continues during the ….. As contraction proceeds, blood is
squeezed upward toward the semilunar valves
sys
S–T segment
- Re/depolarization of ventricular contractile fibers begins and spreads. This produces the …. in the ECG after the onset of the P wave.
Repolarization
T wave
- Shortly after the T wave begins, the ventricles start to relax (ventricular …stole). Then, ventricular re/depolarization is complete and ventricular contractile
fibers are relaxed
dia
repolarization
The heart valves open and close actively/passively
passively, because of pressure
differences on either side of the valve
Blood flows from lower/higher to lower/higher pressure.
higher to lower
Cardiac output = (definition)
amount of blood pumped by the heart/minute
Cardiac output = (formula)
CO = HR (heart rate) x SV (stoke volume)
Heart rate = (definition/ ..)
beats/min
SV = (… / …)
ml/beat
A …..cardia is defined as a rate greater
than 100 beats/min.
* A …..cardia is defined as a rate less
than 60 beats/min (or <50 beats/min
during sleep).
tachy
Brady
- Several factors contribute to regulation
of heart rate:
- Autonomic nervous system
- Somatic nervous system
- Chemicals: hormones and cations
- Others
true/false
false, not the somatic, which is about voluntary movements
Nervous system regulation of the heart originates in the ….. center in the
medulla oblongata (lowest portion of the brainstem).
cardiovascular
The cardiovascular center in the medulla receives input from:
1. Sensory receptors: propioceptors (monitor position of limbs and muscles),
chemoreceptors (monitor chemical changes in blood), ……receptors (monitor
the stretching of major arteries and veins caused by the pressure of the blood
flowing through them).
2. Higher brain centers: limbic system and cerebral cortex.
baro
The cardiovascular center directs appropriate output by increasing or decreasing
the frequency of nerve impulses in only the
parasympathetic branches (vagus nerves) of the ANS
true/false
False, also sympathetic (cardiac accelerator nerves)
What two chemicals regulate heart rate?
Hormones (epinephrine and norepinephrine)
and cations
Cations:
Excess potassium speeds/slows the heart rate
Excess of calcium ions speeds/slows the heart rate
pot: slows
Calcium: speeds
OTHER FACTORS REGULATING HEART RATE?
age, gender, fitness, body temp
The end-diastolic volumen or EDV (preload) is a measure of the filling/emptying of the ventricle,
filling
determined by ventricular distensibility and the ventricular filling pressure.
The end-systolic volumen or ESV (afterload) is the volume left in the heart at the end
of systole.
true/false
true
Stroke Volume = end-diastolic volume - end-systolic volumen
SV = EDV - ESV
* According to this formula, how can we increase SV?
- Increasing the end-diastolic volumen (EDV) (preload)
- Decreasing the end-systolic volumen (ESV) (afterload)
Three factors regulate stroke volume and ensure that the left and right ventricles
pump equal volumes of blood:
(1) Preload: the degree of stretch on the heart before it contracts.
(2) Afterload: the pressure that must be exceeded before ejection of blood from the
ventricles can occur.
(3) Contractility or inotropy: the forcefulness of contraction of individual ventricular
muscle fibers
ok
Preload: Effect of Stretching or Frank–Starling law of the heart:
the more it fills, the greater the force of contraction
ok
Afterload: ejection of blood from the heart begins when pressure in the right
ventricle exceeds the pressure in the pulmonary trunk (about 20 mmHg), and
when the pressure in the left ventricle exceeds the pressure in the aorta
true/false
true
- The pressure that must be overcome before a semilunar valve can open is termed
the preload
true/false
false, afterload
increase in afterload causes stroke volume to in/decrease, so that more blood
remains in the ventricles at the end of systole
decrease
Myocardial contractility or inotropy: the strength of contraction at any given
(constant) pre/afterload.
pre
