heart

Question 1

Two circuits of the heart

Answer 1

Pulmonary circuit: to lungs (rids CO2 and gets O2)

Systemic circuit: oxygenated blood to body

Question 2

Heart location

Answer 2

• in mediastinum (paricardium)
• bt 2nd and 5th intercostal space
• 2/3 to the left of midsternal line
• anterior to vertebral column
• posterior to the sternum

Question 3

Base and Apex

Answer 3

Base = posterior surface towards right
Apex = inferior, left–> points towards hip
Apex pulse bt 5th and 6th ribs (mid clavicular) –> Point of Maximal Impulse

Question 4

Pericardium layers

Answer 4

• Fibrous pericardium: protects and anchors to surrounding structures and prevents overfilling
• Serous pericardium = parietal and visceral
• Parietal lines internal surface of fibrous pericardium
• visceral (epicardium) on external surface of heart
• Pericardial cavity filled with fluid to reduce friction

Question 5

Pericarditis

Answer 5

• inflammation of pericardium

- roughens membrane surfaces -> pericardial friction rub (creaking sound)

Question 6

Cardiac tamponade

Answer 6

excessive fluid sometimes compresses heart

-limits pumping ability

Question 7

layers of heart wall

Answer 7

Epicardium: visceral layer of serous pericardium
Myocardium: spiral bundles of contractile cardiac muscle cells –> cardiac skeleton = interlacing CT that ancors muscle fibers, supports vessels/valves, and limits APs to specific areas)
Endocardium: continuous with endothelial lining of blood vessels –> lines heart chambers and covers cardiac skeleton of valves

Question 8

fossa ovalis

Answer 8

in interatrial septum

-remnant of foramen ovale of fetal heart

Question 9

Sulci

Answer 9

Coronary sulcus encircles junction of atria and ventricles
Anterior interventricular sulcus
Posterior interventricular sulcus

Question 10

Auricles

Answer 10

appendages that increase atrial volume

Question 11

Right atrium features vs left

Answer 11

pectinate muscles in both
right has crista terminalis which separates posterior from anterior
right has tricuspid valve
left has mitral/bicuspid valve

Question 12

Which blood vessels enter into each atria?

Answer 12

superior/inferior vena cava and coronary sinus empty into right
four pulmonary veins empty into left

Question 13

location of right vs left ventricle

Answer 13

right is most of anterior surface

left is posteroinferior surface

Question 14

trabeculae carneae and papillary muscle

Answer 14

• irregular ridges of muscle on walls of ventricles

- anchor chordae tendineae

Question 15

do atria or ventricles contribute more to the pumping of the heart

Answer 15

VENTRICLES!

atria barely pump anthing

Question 16

purpose of heart valves

Answer 16

• ensure unidirectional bloodflow

- open and close in response to pressure changes

Question 17

AV valves

Answer 17

prevent backflow when ventricles contract

chordae tendinea anchor cusps to papillary muscles and hold valve flaps in closed position

Question 18

semilunar valves

Answer 18

prevent backflow when ventricles relax

aortic and pulmonary

Question 19

Incompetent valve

Answer 19

-blood backflows so heart repumps the same blood over and over

Question 20

valvular stenosis

Answer 20

stiff flaps constrict openeing

-heart has to exert more force to pump blood

Question 21

pulmonary circuit

Answer 21

right atrium
tricuspid valve
right ventricle
pulmonary semiluar valve
pulmonary trunk
pulmonary arteries
lungs 
pulmonary veins 
left atrium

Question 22

systemic circuit

Answer 22

left atrium
mitral valve
left ventricle
aortic semilunar valve
aorta
tissues

Question 23

ratio of blood in systemic circulation to pulmonary circulation

Answer 23

they’re equal
pulmonary = short, low pressure
systemic = long, high friction

Question 24

coronary circulation

Answer 24

• part of systemic circulation
• functional blood supply to heart muscles
• delivered when heart is relaxed
• left ventricle receives most blood
• has many anastosomes (junctions)

Question 25

Arteries of coronary circulation

Answer 25

Left coronary artery branches - anterior interventricular artery - circumflex artery - supply interventricular septum, anterior ventricular walls, left atrium, and posterior left ventricle walls Right coronary artery branches - right marginal artery - posterior interventricular artery - supplie right atrium and most of right ventricle

Question 26

Angina pectoris

Answer 26

thoracic pain caused by fleeting deficiency in blood delivery to myocardium -weakens cells

Question 27

Myocardial infarction

Answer 27

- prolonged coronary blockage | - areas of cell death repaired with noncontractile scar tissue

Question 28

Cardiac muscle cells

Answer 28

- short, striated, branched, fat, interconnected - 1-2 nuclei - t tubules wide and less numerous - SR simpler than skeletal muscle - 25-35% of cell volume is mitochondria

Question 29

Intercalated discs

Answer 29

- junctions between cells, anchoring them - desmosomes prevent cells from separating during contraction - gap junctions allow ions to pass from cell to cell; electrically couple adjacent cells --> allow heart to be functional synctium

Question 30

Difference in cardiac muscle contraction from skeletal muscle contraction

Answer 30

- 1% of cells have autorhythmicity (don't nees NS and can depolarize entire heart) - All cardiomyocytes contract as a unit (all or none) - long absolute refractory period (250 ms) preventing tetanic contractions - Depolarization wave opens slow Ca channels in sarcolemma (Ca surge prolongs depolarization phase) - AP and contraction last longer so blood can be ejected - repolarization results in inactivation of Ca channels and opening of voltage K channels (Ca returns to SR)

Question 31

Similarities between cardiac muscle contractions and skeletal muscle contractions

Answer 31

- Depolarization opens few voltage gated fast Na channels in sarcolemma (RMP foes from -90 to +30) --> close fast - Depolarization wave down T tubules --> SR to release Ca - Excitation contraction coupling occurs --> Ca binds troponin and filaments slide

Question 32

summary of electrical activity of muscle contraction

Answer 32

1. Depolarization: fast voltage-gated Na channels open and are quickly inactivated (pos feedback) 2. Plateau phase: Ca influx through slow Ca channels keep the cell depolarized 3. Repolarization due to Ca channels inactivating, allowing a K efflux

Question 33

cardiac energy requirements

Answer 33

lots of mitochondria for aerobic respiration | -will switch to lactic acid from skeletal muscles if it needs a fuel source

Question 34

Does the nervous system control heart contraction?

Answer 34

Nah | BUT AND can impact heart rate

Question 35

How does the heart beat all at the same time?

Answer 35

- Gap junctions - Intrinsic cardiac conduction system = network of noncontractile (autorhythmic) cells which initiate and distribute impulses

Question 36

Pacemaker cells

Answer 36

- have unstable RMP due to slow opening of Na channels (always depolarizing) - @ threshold, ca channels open - explosive Ca influx = "rising phase" of AP - Repolarization = inactivation of Ca channels and opening of voltage gated K channels

Question 37

Summary of AP initiation by pacemaker cells

Answer 37

1. Pacemaker potential --> repolarization closes K channels and opens slow Na channels, creating an ion imbalance 2. Depolarization --> Ca channels open and a ton of Ca comes in ("rising phase") 3. Repolarization --> K channels open and K goes out of cell