week 5: cardiac physiology: structure of the lungs and heart and activity of the heart

Question 1

the heart is myogenic meaning

Answer 1

contacts by itself

Question 2

why is the heart myogenic

Answer 2

pacemaker cells within the heart

Question 3

SAN cells

Answer 3

0.1 mm in length
spontaneously beat

Question 4

cardiac AP originates

Answer 4

SA node
not dependent on neuronal stimulation
myogenic
generated own firing rate

Question 5

myogenic tissue within heart

Answer 5

SA node
AV node
bundle of his

Question 6

dominant pacemaker

Answer 6

SA node as it’s at the highest frequency firing rate

Question 7

delay from propagation of electrical signal

Answer 7

100 millisecond

Question 8

how is heart muscle connected

Answer 8

electrically
electrical connection between cardiomyocytes
gap junctions

Question 9

electrical connection between cardiomyocytes allows AP generated in pace maker cells to

Answer 9

spread through to adjacent cells
electrical current passes through gap junctions in intercalated discs

Question 10

gap junctions in intercalated discs forms a

Answer 10

low resistance pathway

Question 11

frequency in which AP fires controls

Answer 11

heart rate

Question 12

pacemaker potential is controlled by

Answer 12

different levels of permeability to different ions

Question 13

maximum diastolic potential

Answer 13

phase 4
lowest part of AP
can move which changes frequenxy heart rate
ussually sits around -70mV

Question 14

why does membrane potential begin to rise in stage 4

Answer 14

due to declining permeability to K+ and increasing permeability to Na+ and Ca2+
more + ions moving into cell faster than Na+ moving out

Question 15

-40mV reached

Answer 15

threshold reached
rapid increase in Ca2+ permeability through altide calcium channles
generate upstroke in AP

Question 16

peak of AP

Answer 16

associated in decrease in Ca2+ permeability, channels shut
increased permeability to K+, K+ channels open
K+ leaves faster than Ca2+ enter,
causes membrane to become more negative
decrease in membrane potential

Question 17

membrane potential reaches -55/60mV

Answer 17

permeability to K+ starts to decrease
re-entry of Na+ and Ca2+
restarting pacemaker potential

Question 18

AP spreads…..

Answer 18

spreads through atrial tissue to AV node via internodial tracts
propagates to all of atiral but specifically goes down internodial tracts to stimulate AV node

Question 19

cells in atrioventricular node AP

Answer 19

slower
cause delay of impulse transmitting down further- 100 milliseconds

Question 20

after impulse reaches AV node,

Answer 20

passed to bundle of His from AV node
only electrical connection between atrial tissue and ventricular tissue

Question 21

after bundle of His,

Answer 21

electrical tissue splits into two branches:
right and left bundle branch

Question 22

where does electrical activity run down to from left and right bundle branches

Answer 22

apex of heart

Question 23

electrical activity after apex of heart,

Answer 23

spread throughout ventricular tissue through Purkinje fibers

Question 24

ventricular action potential has a stable:

Answer 24

resting membrane potential
-90mV

Question 25

because of the stable resting membrane potential of the ventricular AP

Answer 25

unless it receives external stimulus, it will not contract therefore relies on pacemaker cells

Question 26

ventricular AP: phase 0

Answer 26

electrical activity passes to ventricular myocyte through gap junction, rapid depolarisation goes to 20/30mV

Question 27

ventricular AP: phase 1

Answer 27

early repolarisation slight repolarisation before plateau reached

Question 28

ventricular AP: phase 2

Answer 28

plateau phase longer 200/300millisendocnds allows for duration of mechanical event: contraction of myocytes

Question 29

ventricular AP: phase 3

Answer 29

repolarsation back to-90mV

Question 30

ventricular AP (permeability changes): phase 0

Answer 30

controlled by increase in Na+ permeability

Question 31

ventricular AP (permeability changes): phase 1

Answer 31

sudden decrease in Na+ permeability increase in K+ permeability + ions leave cell cell MP becomes more -

Question 32

ventricular AP (permeability changes): phase 2

Answer 32

increase in Ca2+ permeability, Ca2+ entering cell decrease in K+ permeability, K+ leaving cell

Question 33

ventricular AP (permeability changes): phase 3

Answer 33

increase in K+ permeability, decrease Ca2+ permeability more + ions leaving, less entering allows us to reach resting mp

Question 34

ventricular AP (permeability changes): phase 4

Answer 34

increase permeability of K+ lots of + ions leaving cell helps to keep - MP

Question 35

Ventricular AP refractory period

Answer 35

must reach back to resting membrane potential before AP can be reactivated length in which it takes cell to mechanically contract

Question 36

firing of electrical activity leads to

Answer 36

mechanical event: contraction

Question 37

how does electrical activity turn into mechanical action

Answer 37

excitation contraction-coupling

Question 38

AP opens

Answer 38

opens calcium channels within T Tubules calcium enters diads

Question 39

calcium entering diads causes

Answer 39

further calcium release from viandadeen receptors more calcium being released from internal stores within cell elevates intercellular calcium level

Question 40

once intercellular calcium level in high,

Answer 40

binds to troponin C on thick and thin myosin filaments cross-bridged can occur allow for contraction to occur

Question 41

why and how must calcium levels drop again

Answer 41

allow for cell to relax Ca2+ extruded back out through na/ ca channels into extracellular are or pumped back into intercellular stores within sarcoplasmic reticulum

Question 42

spread of excitation through myocardium creates...

Answer 42

small currents that can be detected on the body's surface

Question 43

Einthoven's triangle

Answer 43

created through electrodes created on left arm right arm and left leg creates triangle around heart

Question 44

Einthoven's triangle lead 1

Answer 44

right arm to left arm

Question 45

Einthoven's triangle: lead 2

Answer 45

right arm to left leg used to represent net amplitude and direction of electrical activity of heart runs in line in same direction in whihc heart is directed, base to apex

Question 46

Einthoven's triangle: lead 3

Answer 46

left arm to left leg

Question 47

ECG: upward deflection on ECG

Answer 47

positive signal moving towards left leg OR negative signal moving towards negative electrode

Question 48

ECG: negative deflection on ECG

Answer 48

positive signal moving away from + electrode

Question 49

ECG: P wave

Answer 49

atrial excitation small + wave

Question 50

ECG: short flat area between P wave and QRS complex

Answer 50

delay at the AV node occurs

Question 51

ECG: QRS complex

Answer 51

ventricular excitation ventricular depolarsation large + defelction at end of S, all ventricles fully depolarised

Question 52

ECG: T wave

Answer 52

ventricular repolarisation small + deflection larger than P wave

Question 53

ECG: flat area after T wave

Answer 53

heart at rest waiting until next beat

Question 54

ECG: P-Q interval

Answer 54

measures delay between atrial and ventricular depolarisation includes AV nodal delay

Question 55

ECG: Q-T interval

Answer 55

measure of the duration of ventricular systole how long they are in mechanical contraction phase

Question 56

ECG: T-Q interval

Answer 56

measure of the duration of ventricular diastole relaxation phase

Question 57

ECG: R-R interval

Answer 57

measure of heart rate

Question 58

caridac cyle

Answer 58

alternates periods of systole(contraction and ejection) and diastole (relaxation and filling)

Question 59

two heart sounds

Answer 59

heart sound 1: lup heart sound 2: dup

Question 60

heart sound 1: lup associated with

Answer 60

closure of AV valves at the start of ventricular systole

Question 61

heart sound 2: dup associated with

Answer 61

closure of the semi-lunar valves at the start of the ventricular diastole

Question 62

other heart sounds

Answer 62

associated with rapid ventricular filling or atrial contraction only heard during pathological conditions or particular circumstances