Chapter 19: Part II

complete cards in order

cardiac cycle

one complete contraction and relaxation of all four chambers of the heart

systole

contraction

diastole

Relaxation

atrial contraction

as the atria contracts, the blood atria fills

1. Blood is moving from the atria to the ventricles (ventricular filling)

2. AV valves are open and semilunar valves are closed

3. Atrial pressure exceeds ventricular pressure

isovolumetric contraction

when the ventricles begin to contract so there pressure, not enough pressure to open SL, but enough pressure to open the AV

1. Blood is not moving at the point, all 4 valves are temporarily close

2. As the ventricles begin to contact, the AV valves will close

3. No movement

4. Ventricular pressure is higher than atrial pressure and lower than the vessel pressure

ventricular ejection

when the ventricles are fully contracted and blood is ejected

1. Pressure in ventricle exceeds pressure in atria and vessels

2. Semilunars are open and AV valves are closed

isovolumetric relaxation

blood is not moving, all 4 valves are closed because the ventricles have started to relax


1. Enough pressure to keep AV closed, but not enough to keep SL open

atrial relaxation and ventricular filling

passive filling occurs

1. Blood is coming into the atria from the great veins

2. AV valves are open and semilunar valves are closed

3. Passive→ most of the EDV is from the passive filling

stroke volume

the amount of blood ejected from the ventricles in one beat

auscultation

Listening to sounds made by body

lub

• Occurs with the closing of the AV valves

• first heart sound

• longer and louder

dub

• Second heart sound

• Softer and sharper

• Occurs with the closure of semilunar valves

third heart sound

caused by a sudden deceleration of blood flow into the left ventricle from the left atrium

ventricular balance

equal amounts of blood are pumped by left and right sides of the heart

congestive heart failure

results from the failure of either ventricle to eject blood effectively

cardiac output

the amount of blood ejected by each ventricle in 1 minute

* heart rate X stroke volume = amount of blood in one beat

cardiac reserve

Capacity to increase cardiac output above rest level

* exercise output - cardiac output = level of exercise an individual can pursue

chronotropic agents

affect time or rate; change heart rate

• Influence SA node to change its firing rate

• Influence AV node to alter amount of delay

• work via ANS or hormones

AV delay

AV node to AV bundle (P-R segment)

positive chronotropic agents

increase heart rate

* ex.) electrolytes, hypercapnia, thyroid hormone, caffeine, nicotine, and cocaine

negative chronotropic agents

decrease heart rate

* ex.) parasympathetic activity, beta-blocker drugs

bainbridge reflex

The reflex that involves baroreceptors found in the aortic arch and carotid sinus

venous return

volume of blood returned to the heart

* determines end diastolic volume

preload

how much blood is loading into the heart

inotropic agents

external agents that alter contractility

• Generally due to changes in calcium available in sarcoplasm

• More calcium available → more crossbridges formed → greater contraction

afterload

the pressure in the aorta or the pulmonary trunk to open the semilunar valves

• resistance in arteries

• Pressure that must be exceeded before blood ejected

end diastolic volume

the amount of blood in each ventricle following ventricular filling

end systolic volume

the amount of blood remaining in the ventricle after ejection/after stroke volume

hypovolemia

low blood volume

starling law of the heart

Venous return increases during exercise and with a slower heart rate (e.g. in high-caliber athletes with strong hearts)

* Increase EDV stretches the heart volume to contract with greater force

postive inotropic agents

increase available calcium

• Epinephrine and norepinephrine increase calcium

• Thyroid hormone increases number of receptors for epinephrine and norepinephrine

negative inotropic agents

decrease available Ca2+

• Electrolyte imbalances such as increased K+ or H+

• Certain drugs, e.g., Ca2+ channel-blocking blood