Cardiac Conduction and circulation physiology Anatomy Powerpoint

Question 1

Skeletal muscle fiber contraction mechanism

Answer 1

Motor neuron AP -> acetylcholine release into neuromuscular junction -> Ach binds to ligand gated ion channels -> Na+ floods into cell along T tubules -> Ca2+ entrance into the cell -> Ca2+ induced Ca2+ release -> Ca2+ binds to troponin on thin filament -> troponin moves tropomyosin out of the way -> actin freed -> myosin binds actin -> ATP binds -> ATP hydrolysis shifts myosin head into active phase -> ADP disociates and power stroke occurs

Question 2

Cardiac muscle fiber contraction mechanism

Answer 2

Pacemaker cells thru leaky channels cause slow influx of Na+ -> at threshold Ca2+ ions flow in further depolarizing membrane -> K+ ion channels open, Ca2+ channels close and K+ leaves cell returning voltage to normal ->Intercalated disks propagate to contractile cell -> Na+ channels open and see flooding of Na+ inward -> Ca2+ channels also open slowly influxing to cell -> Na+ close, K+ channels open -> K+ outflux balances Ca2+ influx creating pleateu -> Ca2+ induced Ca2+ release -> myofibril contraction -> Ca2+ channels close

Question 3

Ca2+ channel blockers

Answer 3

Decrease contraction strength, used often to lower blood pressure

Question 4

Troponin I levels in the blood indicate…

Answer 4

…heart damage

Question 5

Cardiac conduction flow pathway, speed of each?

Answer 5

SA node to AV node to Bundle of His to Purkinje fibers (gets slower as we move down)

Question 6

Bachman’s bundle

Answer 6

Goes straight across from SA node to allow left atrium to contract at same time as right atrium, acting quicker than propogation of SA to AV node

Question 7

Intranodal conduction tracts

Answer 7

A series of highly resistive bundles between the SA and AV node that slow the impulse propogation to allow for atrial contraction prior to the ventricles

Question 8

Koch’s triangle

Answer 8

Home of the AV node, located in a triangle enclosed by the septal leaflet of the tricsupid valve, the coronary sinus (drains the heart), and tendon of todaro (valve from inferior vena cava)

Question 9

Intrinsic nodal rate set by AV node

Answer 9

40-60bpm

Question 10

Intrinsic nodal rate set by ventricles

Answer 10

20-40 bpm

Question 11

S1 is….

Answer 11

…closure of AV valves, start of systole

Question 12

S2 is…

Answer 12

…closure of semilunar valves, start of diastole

Question 13

Isovolumentric contraction phase

Answer 13

Brief period when both AV and semilunar valves are closed and pressure is building in the ventricles before the semilunar valves open for the ejection phase

Question 14

Stroke volume

Answer 14

EDV-ESV

Question 15

How can stroke volume be increased?

Answer 15

Increase EDV or decrease ESV

Question 16

Cardiac output

Answer 16

HR x SV

Question 17

Frank Starling law

Answer 17

Greater stretching of the heart up to a point creates greater force of contraction

Question 18

Chronotropic effect

Answer 18

Heart rate affect

Question 19

Inotropic effect

Answer 19

Strength of contractility affect

Question 20

Dromotropic effect

Answer 20

Speed of conductuion affect

Question 21

Vagal tone

Answer 21

Constant parasympathetic innervation given to the heart to slow heart rate from intrinsic rhythm,

Question 22

Preferred metabolic fuel of cardiac muscle

Answer 22

Fatty acids, then glucose, then ketones

Question 23

Cardiac arteries receive blood during what phase of contraction?

Answer 23

Diastole