cardiovascular - lecture 5

Question 1

(T or F) All deoxygenated blood passes through either the superior or inferior vena cava on its way to right chambers of the heart

Answer 1

false
coronary circ pumps directly into right atria

Question 2

(T or F) The pulmonary artery transports oxygenated blood from the heart.

Answer 2

false
in general arteries carry oxygenated blood but exception = pulmonary vessels

Question 3

(T or F) The Purkinje fibers can fire on their own if an impulse isn’t generated by the sinus node.

Answer 3

true
all cells of specialized conduction system have potential to beat on their own
usually dont as sa node fires faster

Question 4

(T or F) The Purkinje fibers form synapses with the myocardium in the ventricles, allowing the ventricles to fire in synchrony.

Answer 4

false
bc purkinje fibers are muscle and do not form synapses
only nerves do that

Question 5

(T or F) Na+ ions pass through gap junctions of cells where one is active and the other is resting.

Answer 5

true
but sodium concentrations arent as high as potassium inside cells
can still pass through gap junctions tho
impact on local circuit current = mostly in interstitial space

Question 6

describe gap junctions

Answer 6

mostly located at ends of myocytes
oriented perpendicular to cell axis
concentrated at ends of cells
less gap junctions on sides of cells

Question 7

what is electrocardiogram and electrocardiograph

Answer 7

gram is reading = recording
graph takes reading = device

Question 8

what is ecg/ekg

Answer 8

recording of electrical activity of heart
extracellular recordings
only appear when potential difference

Question 9

describe ecg set up

Answer 9

LL lead = left ankle
RL lead = right ankle
LA and RA lead = right and left wrist
cheat lead
5 leads
lead selector switch - measures potential diff (voltage)
voltmeter v sensitive
rl = right leg always connected = reference lead, set to 0

Question 10

what is purpose of gel for ecg

Answer 10

lowers resistivity of skin
allows free flowing of ions

Question 11

describe typical ecg

Answer 11

divisions to help read it
around 1 second
standard man = resting bpm 60

Question 12

describe all waves

Answer 12

end and start at baseline

Question 13

what is complex

Answer 13

deflection away from base line

Question 14

what is potential mv of ecg reading

Answer 14

+1 mv total amplitude
vs ~100mv for intracellular recording

Question 15

what is p wave

Answer 15

sinus node here fires, invisible tho
atrial contraction = p wave
halfway = av node starts to activate, not seen tho
ends = atria stop contracting and recovery

Question 16

what is q wave

Answer 16

his bundle invisible
left bundle invisible
septum = visible = q wave = left to right propagation
first neg deflection

Question 17

what is qrs complex

Answer 17

r wave and s wave

Question 18

what is r wave

Answer 18

purkinje fibers - invisible
ventricles - visible = r wave

Question 19

what is s wave

Answer 19

late activation

Question 20

what is t wave

Answer 20

ventricles repolarize

Question 21

Why are ECG waves sometimes positive and sometimes negative? What controls its shape?

Answer 21

cell A depolarized and cell B RESTING = ion flow causes b to depolarize
intracellular = +ve ions move from a to b, - ve ions move from b to a
extracellular = +ve ions move from b to a and -ve ions move from a to b

other ions also flow, like if neg opp dir like chloride
ions can flow in both dir
put electrodes on body and sense current flow on outside

Question 22

Case 1: cell A is depolarized (active). B is hyperpolarized (resting). Propagation is going from left to right.

Answer 22

v = + - - = +
positive voltage

Question 23

what is voltage equal to

Answer 23

v = pos end minus neg end

Question 24

cell A is hyperpolarized (resting) . B is polarized (active)
Propagation is going from right to left

Answer 24

v = - - + = -
neg voltage

Question 25

cell A is hyperpolarized (resting). B is polarized (active). A repolarization (relaxation) wave is going from left to right.

Answer 25

v = - - + = -

Question 26

describe voltage when depolarization

Answer 26

depolar going towards +ve electrode, V is +ve
depolar going towards -ve electrode, V is -ve

Question 27

describe voltage during repolarization

Answer 27

repolar going towards +ve electrode, V is -ve
repolar going towards -ve electrode, V is +ve

Question 28

describe overview of ecg

Answer 28

atrial excitation = activation of sa node, av node right to left, p wave
ventricular excitation = q contraction of septum left to right, r s contraction of ventricles
ventricular relaxation = t wave, relaxation wave

Question 29

when do atria relax

Answer 29

during qrs but not seen
since ventricles mask

Question 30

describe ap durations

Answer 30

diff on inside muscle vs outside
propagates
inside out with depolarizing and outside in when repolarizing
could see some neg t waves

Question 31

why is t wave positive

Answer 31

bc depolarization wave moves in opp dir as repolarization wave
due to diff in ap duration from inside to outside of heart

Question 32

describe bipolar limb leads

Answer 32

triangle arounf heart = all display diff info on ecg
triangulating
reference leads also attacked
lead = wire, but also difference between 2 wires

Question 33

describe kirchhoffs voltage law - triangle

Answer 33

sum of changes in potential encountered in complete loop circuit = 0
so voltage of all leads sum 0

Question 34

describe unipolar ecg leads

Answer 34

using kirchhofs law
exploring lead
limb unipolar and chest unipolar

Question 35

describe sa node ap graph

Answer 35

pacemaker potential
spontaneous diastolic depolar
driven by flux of calcium
one cell drives other
potential diff not as great = slower
no resting membrane potential since pacemaker cells
no Ina in sinus node cells: Ica generates upstroke

Question 36

describe atria ap graph

Answer 36

v fast upstroke
~ -90
very negative
no hint of pacemaking current

Question 37

describe his purkinje system ap graph

Answer 37

pacemaking current
no stable resting membrane potential
can beat on own
sodium channel but has pacemaking activity
higher rate of flow = depolarization faster
has Ina and a fast upstroke and a fast propagation

Question 38

describe ventricular ap graph

Answer 38

resting potential - stable
upstroke
plateau, longer than other aps
repolarization = 150-300ms
much longer than nerve or skeletal aps
resting potential more hyperpolarized than in neurons

Question 39

describe ionic channels in cardiac cells

Answer 39

sodium and potassium channels

Question 40

describe ionic basis underlying ventricular ap

Answer 40

change in conductance of channels
log scale
at rest Pk»Pca and Pna
so Vrest = close to Ek
Ina = fast inwards na+ current
Itotal + Ik1 + Iks + Ikr +…
many = can do many things at same time

Question 41

describe Pk+ PNa+ PCa2+(L)

Answer 41

Pk+ = high then sense voltage and close then opens again = repolarization
Pna+ = poor conduction of na then channels open, massive change in conductance then closes
Pca2+ = channels open and influx calcium into cell = plateau phase, then closes

Question 42

describe slow aps

Answer 42

sa now
av noode
physiological delay in av node since slow propagation
slow upstroke
1-10 v/sec
important for synchrony
conduction velocity = 0.01-0.05m/sec

Question 43

describe fast aps

Answer 43

activation for rest of them
100-1000 v/sec
conduction velo = 0.5-5m/sec
ventricular muscle
atrial muscle
bundle of his
bundle branches
purkinje fibers

Question 44

what are most important fort aps/ecg

Answer 44

atrial and ventricular cells mostly but many things happening