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51 Cards in this Set

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DURATION OF ACTION POTENTIAL

skeletal muscle: 1-5 ms


cardiac muscle: 200 ms

DURATION OF CONTRACTION

skeletal muscle: 15 - 100 ms


cardiac muscle: 200 ms D

DURATION OF ABSOLUTE REFRACTORY PERIOD:

* protracted influx of calcium increases the action potential which increases this duration..



skeletal muscle: 1 - 2 ms


cardiac muscle: 250 ms



HEART ANATOMY

1. cardiac muscles = very short (skeletal muscles = long)


2. cardiac muscles arrange in line (skeletal muscles arranged adjacent)


3. intercalated discs (coming together of sequential cardiac muscles)


4. gap juntions (found in intercalated discs, permit flow of ions between sequential cardiac muscles)


5. A band (region of cardiac muscle that houses myosin)


6. I band (region that houses actin)

LAYERING OF THE HEART

SUPERFICIAL: some adipose tissue surrounding heart (we hope not too much)



PERICARDIUM:


A. FIBROUS PERICARDIUM


B. SEROUS PERICARDIUM


1. PARIETAL LAYER


2. VISCERAL LAYER (EPICARDIUM)


3. PERICARDINAL CAVITY





PERICARDIUM

a double-walled sac


FIBROUS PERICARDIUM

- more superficial layer that's loose


- dense connective tissue


- protects & anchors to adjacent structures

SEROUS PERCARDIUM

- slippery membrane with two parts

PARIETAL LAYER

- lines the deep aspect of fibrous pericardium

VISCERAL LAYER (EPICARDIUM)

- functions as a component of the external heart wall

PERICARDINAL CAVITY

- fluid that decreases friction


- found between parietal & visceral layers

LAYERS TO THE WALL OF THE HEART

1. epicardium


2. myocardium


3. endocardium

MYOCARDIUM

- cardiac muscle


- myofibers tied together by connective tissues


- these fibers provide stability to heart as it expands

ENDOCARDIUM

- white colored sheet of squamous epithelium


- continuous w. endothelial linings of blood vessels

STRUCTURE OF THE HEART

1. superior + inferior vena cava


2. right atrium


3. tricuspid valve


4. right ventricle


5. semilunar valve


6. pulmonary trunk


7. pulmonary veins


8. left atrium


9. bicuspid valve


10. left ventricle

1. SUPERIOR & INFERIOR VENA CAVA

- two major veins that empty deoxygenated blood into the heart

2. RIGHT ATRIUM

- one of the superior chambers


- chamber that superior & inferior cava empty into


- small & thinly muscled


- only push blood a short distance

3. TRICUSPID VALVE

- blood from the right atrium must pass through this before it can enter the right ventricle


- attached to interior region of right ventricle by chordae tendineae



3a. CHORDAE TENDINEAE

- attaches tricuspid valve to interior of right ventricle


- prevent tricuspid from flapping into right atrium when the right ventricle has a higher pressure


- attaches to papillary muscles

3b. PAPILLARY MUSCLES

- contract just prior to contraction of right ventricle

4. RIGHT VENTRICLE

- comprises most of inferior & anterior aspect of heart


- larger/heavily muscled chamber


- ejects blood into the pulmonary trunk

5. SEMILUNAR VALVE

- 3 pocket-like cusps


- prevent blood from returning from the pulmonary trunk back to the right ventricle

6. PULMONARY TRUNK

- directs blood from right ventricle towards right/left pulmonary arteries


- pulmonary arteries take blood toward right/left lung


- capillaries of lung are adjacent to alveoli (small sacs)


- gases can be exchanged


- dead space within lung? get more on this

7. PULMONARY VEINS

- carry the blood back toward left atrium

8. LEFT ATRIUM

- see discussion of right atrium

9. BICUSPID VALVE (MITRAL VALVE)

- same function as tricuspid valve


- BUT different location & formed by 2 flaps


- chordae tendineae that insert into left venticle by way of papillary muscles

10. LEFT VENTRICLE

- forms inferior, left, & posterior wall of heart


- heavily muscled chamber


- ejects blood into aorta


- see discussion about Frank-Starling mechanism

CORONARY CIRCULATION

1. left coronary artery


A. anterior interventricular artery (left anterior descending)


B. circumflex artery


2. right coronary artery


A. marginal artery


B. posterior interventricular artery


3. epicardium/myocardium/stuff

1. LEFT CORONARY ARTERY

- arises from base of aorta


- proceeds toward left side of heart through atrioventricular groove

1a. ANTERIOR INTERVENTRICULAR ARTERY


(LEFT ANTERIOR DESCENDING)

- branches off left coronary artery


- proceeds down through interventricular sulcus


- supplies blood to:


- interventricular septum


- anterior walls of both ventricles

1b. CIRCUMFLEX ARTERY

- branches off left coronary artery

- supplies blood to:


- left atrium


- posterior wall of left ventricle


2. RIGHT CORONARY ARTERY

- arises from base of aorta


- continues to right side of heart through atrioventricular groove

2a. MARGINAL ARTERY

- provides blood to lateral aspect of right side of myocardium

2b. POSTERIOR INTERVENTRICULAR ARTERY

- moves downward along posterior aspect of heart until it reaches apex of heart


- supplies blood to posterior ventricular walls

3. EPICARDIUM/MYOCARDIUM/ETC

- each of these arteries are housed within epicardium!


- when heart's relaxed - blood carried through major branches of these arteries to deeper myocardium


- while myocardium is contracting - blood can't be pumped into it because the arteries are compressed by the contraction


- semilunar valves of aorta also obstruct blood flow into coronary artery

HEART PATHOLOGY

1. heart pathology stuff


2. angina pectoris


3. myocardial infarction

1. HEART PATHOLOGY STUFF

- heart = 1/200 of the weight of the body


- requires 1/20 of body's blood supply


- ventricles get largest Q of this blood

2. ANGINA PECTORIS

- thoracic pain by fleeting deficiency in blood delivery to myocardium


- disruption in blood supply - possible causes:


- a physical barrier within the heart arteries


- can be due to stress induced spasm of heart arteries


- differential b/t blood needed & blood demanded



3. MYOCARDIAL INFARCTION

- total interruption of blood delivery to some Q of the myocardium


- myocardium dies from ischemia


- when blood flow returns - inflammatory response begins


- "one component of this process is that free radicals (like nitric oxide) is released by the granulocytes. These free radicals depress cardiac contractility"

AUTORHYTHMICITY OF THE HEART

1. autorhythmicity stuff


2. sinoatrial node (SA)


3. depolarization of atria


4. atrioventricular node (AV)


5. atrioventricular bundle


6. right & left bundle branches


7. purkinje fibers


8. ventricles contract


A. SA - last ventricular muscle


B. arrhythmias


9. heart block?

1. AUTORHYTHMICITY OF HEART STUFF

- some myocardial fibers = self-exciting


- ^ enables heart to maintain some intrinsic regulation of heart rate frequency

2. SINOATRIAL NODE (SA)

- in wall of right atrium just inferior to entrance of superior vena cava


- without external regulation - SA node will depolarize 100 times per minute


- under normal external regulation - depolarizes 75 times per minute


- SA node sets the pace for heart rhythm & sinus rhythm (fastest auto-rhythmic cell in heart)

3. DEPOLARIZATION OF ATRIA

self explanatory

4. ATRIOVENTRICULAR NODE (AV)

50/min




- stimulated by SA node via the internodal pathway


- smaller diameter fibers -- delays passage of depolarization for 0.1 second


- ^ enables atria to complete the contraction prior to the initiation of ventricular depolarization

5. ATRIOVENTRICULAR BUNDLE

30/min




- in superior part of interventricular septum


- only passage of depolarization into ventricles can pass through this mechanism

6. RIGHT & LEFT BUNDLE BRANCHES

- atrioventricular bundle immediately divides into 2 branches


1. one runs inferior toward apex of heart on right side of


interventricular septum


2. one runs toward apex of heart on left side of interventricular


septum

7. PURKINJE FIBERS

- begin toward inferior aspects of interventricular septum


- ends toward apex of heart


- @ apex - fibers turn in a superior direction & begin to move up ventricular walls


- first location they travel to is the papillary muscles that work the chordae tendineae

8. VENTRICLES CONTRACT

- initate a wringing like contraction


- begins @ apex + works in superior direction toward the atria

8a. SA --> LAST VENTRICULAR MUSCLE

total time from SA to last ventricular muscle = 220 ms

8b. ARRHYTHMIAS

- SA node may be defective -- causes ectopic focus (some myocardium in atria become hyperexcitable & can cause extrasystole or extra contraction)


- PVC = premature ventricular contractions

9. HEART BLOCK

- damage to AV node can inhibit SA depolarization from being delivered to ventricles


- so - ventricles contract @ their depolarization rate


- complete heart block requires fixed-rate pacemaker


- incomplte requires demand-type pacemaker