cardiovascular - lecture 5 Flashcards
(T or F) All deoxygenated blood passes through either the superior or inferior vena cava on its way to right chambers of the heart
false
coronary circ pumps directly into right atria
(T or F) The pulmonary artery transports oxygenated blood from the heart.
false
in general arteries carry oxygenated blood but exception = pulmonary vessels
(T or F) The Purkinje fibers can fire on their own if an impulse isn’t generated by the sinus node.
true
all cells of specialized conduction system have potential to beat on their own
usually dont as sa node fires faster
(T or F) The Purkinje fibers form synapses with the myocardium in the ventricles, allowing the ventricles to fire in synchrony.
false
bc purkinje fibers are muscle and do not form synapses
only nerves do that
(T or F) Na+ ions pass through gap junctions of cells where one is active and the other is resting.
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
describe gap junctions
mostly located at ends of myocytes
oriented perpendicular to cell axis
concentrated at ends of cells
less gap junctions on sides of cells
what is electrocardiogram and electrocardiograph
gram is reading = recording
graph takes reading = device
what is ecg/ekg
recording of electrical activity of heart
extracellular recordings
only appear when potential difference
describe ecg set up
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
what is purpose of gel for ecg
lowers resistivity of skin
allows free flowing of ions
describe typical ecg
divisions to help read it
around 1 second
standard man = resting bpm 60
describe all waves
end and start at baseline
what is complex
deflection away from base line
what is potential mv of ecg reading
+1 mv total amplitude
vs ~100mv for intracellular recording
what is p wave
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
what is q wave
his bundle invisible
left bundle invisible
septum = visible = q wave = left to right propagation
first neg deflection
what is qrs complex
r wave and s wave
what is r wave
purkinje fibers - invisible
ventricles - visible = r wave
what is s wave
late activation
what is t wave
ventricles repolarize
Why are ECG waves sometimes positive and sometimes negative? What controls its shape?
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
Case 1: cell A is depolarized (active). B is hyperpolarized (resting). Propagation is going from left to right.
v = + - - = +
positive voltage
what is voltage equal to
v = pos end minus neg end
cell A is hyperpolarized (resting) . B is polarized (active)
Propagation is going from right to left
v = - - + = -
neg voltage
cell A is hyperpolarized (resting). B is polarized (active). A repolarization (relaxation) wave is going from left to right.
v = - - + = -
describe voltage when depolarization
depolar going towards +ve electrode, V is +ve
depolar going towards -ve electrode, V is -ve
describe voltage during repolarization
repolar going towards +ve electrode, V is -ve
repolar going towards -ve electrode, V is +ve
describe overview of ecg
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
when do atria relax
during qrs but not seen
since ventricles mask
describe ap durations
diff on inside muscle vs outside
propagates
inside out with depolarizing and outside in when repolarizing
could see some neg t waves
why is t wave positive
bc depolarization wave moves in opp dir as repolarization wave
due to diff in ap duration from inside to outside of heart
describe bipolar limb leads
triangle arounf heart = all display diff info on ecg
triangulating
reference leads also attacked
lead = wire, but also difference between 2 wires
describe kirchhoffs voltage law - triangle
sum of changes in potential encountered in complete loop circuit = 0
so voltage of all leads sum 0
describe unipolar ecg leads
using kirchhofs law
exploring lead
limb unipolar and chest unipolar
describe sa node ap graph
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
describe atria ap graph
v fast upstroke
~ -90
very negative
no hint of pacemaking current
describe his purkinje system ap graph
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
describe ventricular ap graph
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
describe ionic channels in cardiac cells
sodium and potassium channels
describe ionic basis underlying ventricular ap
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
describe Pk+ PNa+ PCa2+(L)
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
describe slow aps
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
describe fast aps
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
what are most important fort aps/ecg
atrial and ventricular cells mostly but many things happening
