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Atrial contraction usually causes an additional ________ ventricle filling, "primer pump"



Atrial function "unnecessary" except during:

vigorous exercise


Atrial pressure changes:
a wave -
c wave -
v wave -

a wave - during atrial contraction
c wave - onset of ventricular con traction
v wave - end of ventricular contraction


Ventricular filling: after systole, A-V valves open due to build up of pressure in ___________________________________________________________________________.

atrial during systole: period of rapid filling of ventricles followed by 2 additional phases


Ventricle as pump = period of __________________, ___________________ and ____________________.

Isovolumetric contraction, ejection, and isovolumetric relaxation.


preload is defined as:

end-diastolic pressure when the ventricle is filled; amount of tension on the muscle when it begins to contract.


Afterload is defined as:

pressure in the artery leading from the ventricle; load against which the muscle exerts its contractile force


Heart and/ or circulation pathology can severely alter:

preload and/or afterload


Chemical energy requirements for cardiac contraction: great dependency / almost exclusive reliance on O2 for energy metabolism (oxidative) compared to ______________________________________________________________________.

skeletal muscle which can utilize anaerobic metabolic sources as well.


Chemical energy requirements for cardiac contraction: energy derived primarily from oxidative metabolism of fatty acids (_________________ of energy source), some lactate, glucose (___________).



Chemical energy requirements for cardiac contraction: cardiac muscle can also use lactic acid generated by what?

skeletal muscle activity


How is the volume of blood pumped by the heart regulated?
Heart pumps ___________ liters of blood/ minute

4-6 liters


How is the volume of blood pumped by the heart regulated?
Heart may be required to pump ___________ this amount (4-6 liters of blood/ minute) with heavy EX.

4-7 x


How is the volume of blood pumped by the heart regulated?
Blood volume pump is regulated by:

1) intrinsic cardiac regulation of pumping in response to changes in volume of blood flowing into the heart.
2) (extrinsic) control of heart rate and strength of heart pumping by the autonomic nervous system


Intrinsic regulation of heart pumping: Frank-starling mechanism
Heart automatically pumps incoming blood, I.e., amount of blood pumped determine primarily by______________________________. As cardiac muscle is stretched with returning blood volume,

by rate of blood flow into heart

approach optima length of actin and myosin fibers for contraction.


Extrinsic regulation of cardiac pump =

- sympathetic nervous system (SNS)
- Norepinephrine released by sympathetic nerve fibers in response to stressors such as fright, anxiety, or exercise; threshold reached more quickly


Norepinephrine released by sympathetic nerve fibers in response to stressors such as fright, anxiety, or exercise; threshold reached more quickly:

- increase cardiac output (CO)
--> pacemaker fires more rapidly
--> enhanced mm contractile try
- effects of inhibiting SNS


What are 3 more components of extrinsic regulation of the cardiac pump?

1) parasympathetic nervous system
2) reduces HR when stressors removed
3) Acetylcholine hyper polarizes membranes of cells --> opens K+ channels
---> PNS fibers in vagus nerves to heart can decrease CO
------> primarily affects HR rather than contractile try


parasympathetic NS =

feed, bread, and rest
(constricts pupil, stimulates flow of saliva, slows heartbeat, constricts bronchi, stimulates peristalsis and secretion, stimulates release of bile and contracts bladder).


Sympathetic NS =

fight or flight (dilates pupil, inhibits flow of saliva, accelerates heartbeat, dilates bronchi, inhibits peristalsis and secretion, conversion of glycogen to glucose, secretion of adrenaline and noradrenaline, inhibits bladder contraction)


During the autonomic innervation of the heart the vagus nerve:
sympathetic chain ganglion:

vagus nerve: stimulates SA node and AV nose via parasympathetic fibers
sympathetic chain ganglion: stimulate SA node and AV node via sympathetic fibers


resting conditions include:
1. SA node receives impulses from both ________________________________.
2. Dominant influence is inhibitory - heart said to exhibit "____________________."
3. "Disconnect" vagaries nerves = HR increases ~____ bpm almost immediately.

1. automatic divisions continuously
2. "vagal tone"
3. 25


normal sinus rhythm =

In a normal sinus rhythm, the electrical impulse originates within the SA node and travels through the AV node. After a brief delay, the impulse travels down the bundle branches.


sick sinus=

resultant in bradycardia (slow heart, often due to problems with SA node)


atrial flutter =

(tachycardia) Upper chambers (atria) of heart beat too fast, making them out of sync with ventricles.


atrial fibrillation =

Atria fibrillate (quiver or twitch quickly). Impulses begin in atria and fight to get through the AV node. (Disorganized electrical pulses causing fast an irregular pattern)



When there is an extra electrical pathway b/n heart's atria and ventricle causing tachycardia. (present at birth)


ventricular tachycardia

(cause sudden death) any rhythm faster than 100 (or 120 beats/min), with 3 or more irregular beats in a row, arising distal to bundle of His.


pacemaker =

small device that's placed in chest or abdomen to help control abnormal heart rhythms. (traditionally inserted into a vein to heart). regulate hearts rate. "new" SA node


Heart pumps ~ 1,9000 gallons of blood through _______________________________ miles of blood vessels each day.

60,000 - 100, 000