Cardio Lec 6

Question 1

Positive chronotropic agents do what

Answer 1

elevate hr (epi, norepi)

Question 2

Negative chronotropic agents do what

Answer 2

lower hr (ach)

Question 3

Heart beats independent of NS

Answer 3

t

Question 4

At rest _NS dominates

Answer 4

PNS (keeps hr < 100bpm)

Question 5

During exercise _NS dominates

Answer 5

SNS (hr > 100bpm)

Question 6

What keeps hr < 100 bpm at rest

Answer 6

Ach

Question 7

1 heart beat every time __ fires

Answer 7

SA node

Question 8

Tachycardia factors

Answer 8

stress, drugs, heart disease, fever, caffeine, anemia, hyperthyroidism (very common)

Question 9

Bradycardia factors

Answer 9

sleep, athletes, hypothermia

Question 10

Intrinsic rate of SA node

Answer 10

100 bpm (but kept below this at rest by…)

Question 11

Heart rate controlled by

Answer 11

pacemaker potential (rate of rise to threshold by nodal cells ANS affects this)

Question 12

SNS makes pacemaker cells depolarize more

Answer 12

quickly

Question 13

PNS makes pacemaker cells depolarize more

Answer 13

slowly

Question 14

Main mediator of the PNS

Answer 14

vagus n.

Question 15

If vagus n. severed & remove parasympathetic influences from the heart, hr would

Answer 15

go up bc PNS is what keeps hr down

Question 16

How does the PNS affect the pacemaker cells?

Answer 16

Ach closes ca & na channels (doesn’t allow + ions in) -> opens k channels (allow + ions to exit) -> makes nodal cells take VERY LONG to DEPOLARIZE

Question 17

How does the SNS affect the pacemaker cells?

Answer 17

norepi bind beta1 rs -> incr cAMP -> opens ca & na channels (+ ions enter cell) -> allow cells to DEPOLARIZE to threshold QUICKER

Question 18

CO peaks at about __ & why

Answer 18

180 bpm bc anything greater -> filling time compromised bc diastole shortens so much & output will start to fall

Question 19

EDV aka

Answer 19

preload

Question 20

At rest, most blood is held on __ side

Answer 20

venous (capacitance vessels)

Question 21

During exercise, venous return goes

Answer 21

up

Question 22

When EDV/preload incr so too does

Answer 22

SV (Starling’s Law of the heart) HEALTHY HEART

Question 23

Frank Staling’s Law

Answer 23

SV is directly proportional to EDV/preload

Question 24

In a healthy heart, EDV is proportional to

Answer 24

SV

Question 25

In an unhealthy heart, as EDV increases or stretches too much, eventually

Answer 25

SV begins to fall bc some cross-bridges lost -> fibers not aligned -> can't be used since binding sites on actin not aligned w/ myosin heads

Question 26

The more cross-bridges (actin & myosin interactions) the more

Answer 26

contractile force

Question 27

If EDV too low ->

Answer 27

ventricles not stretched enough -> actin filaments overlap one another -> can't use binding sites -> can't maximize cross-bridges -> can't get max contractile force

Question 28

EDV changes commonly so have to match more blood in w/ more blood out

Answer 28

T

Question 29

Contractility refers to

Answer 29

greater contractile force at a CONSTANT EDV

Question 30

Contractility uses excess ___ to get more interactions for a greater force of contraction

Answer 30

calcium

Question 31

Starling's Law vs Contractility

Answer 31

IN BOTH: greater contractile force due to more actin & myosin interactions. Starling's more interactions due to: fibers align properly VENTRICLES MORE STRETCHED; Contractility more interactions due to: EXCESS CALCIUM (calcium moves tropomyosin & allows actin & myosin to interact)

Question 32

Inotropicity

Answer 32

by flooding more calcium -> more interactions -> bc inhibition relieved

Question 33

The only thing that can increase contractility is

Answer 33

an increase in intracellular calcium

Question 34

Starling's Law relies on

Answer 34

STRETCH

Question 35

Ejection fraction refers to

Answer 35

% of EDV that is ejected at a given afterload

Question 36

After load refers to

Answer 36

load heart has to work AGAINST to eject blood

Question 37

Norm ejection fraction

Answer 37

65%

Question 38

Ejection fraction calc

Answer 38

EDV / SV

Question 39

ONLY factor that can increase ejection fraction is

Answer 39

increase in contractility

Question 40

Only thing that can increase contractility

Answer 40

calcium

Question 41

Aortic pressure is the

Answer 41

after load

Question 42

Only way semilunar valve opens

Answer 42

ventricular pressure must exceed aortic pressure

Question 43

We want after load to be low or high?

Answer 43

low so heart doesn't have to work as hard

Question 44

Muscles isometric point

Answer 44

point at which muscle can only generate ISOMETRIC CONTRACTION bc after load is so great - heart cant contact against it

Question 45

If bp got so high that reached isometric point ->

Answer 45

Co would be 0 -> stay in isovolumetric phase -> wouldn't enter ejection phase

Question 46

As you get to a higher EDV, isovolumetric point shifts

Answer 46

out bc heart can generate more forceful contraction bc fibers more aligned

Question 47

If nothing else changes, why would SV decrease as after load increases?

Answer 47

bc aortic semilunar valve will open LATER. (its spending more time generating PRESSURE, less time for blood to get EJECTED)

Question 48

Main determinant of after load

Answer 48

total peripheral resistance (TPR)

Question 49

TPR refers to

Answer 49

sum of all arterial resistance; determines bp & aortic pressure

Question 50

An increase in tpr result in an increase in

Answer 50

after load

Question 51

Venous return affects EDV

Answer 51

t

Question 52

Capacitance vessels

Answer 52

veins (store blood)

Question 53

Resistance vessels

Answer 53

arteries

Question 54

Venous side low press low resistance pathway

Answer 54

t

Question 55

Factors that aid venous return

Answer 55

valves, respiratory pump/breathing (by lowering r. atrial press), skeletal muscle pump, PRESSURE GRADIENT (high->low), exercise/MOVEMENT, sympathetic stimulation

Question 56

Anything that lowers r. atrial pressure will

Answer 56

improve press gradient -> aid venous return

Question 57

Anything that increases r. atrial pressure will

Answer 57

lowers press gradient -> retards venous return

Question 58

We want to keep r. atrial press __ so that __

Answer 58

minimized, blood can go from bottom up (high press -> low)