spread citation through heart Flashcards
identify major structures of heart
look pp
describe path of blood flow through heart
1)ventricles relax, atria contract
2) ventricles contract, atria relax
3)atria and ventricles relax-higher pressure in pulmonary artery and aorta causes semi-lunar valves to close
-atria will fill with blood due to higher pressure in vena cava and pulmonary vein
-ventricles continue to relax, their pressure falls below pressure in atria causes AV valves to open and blood flows passively from ventricles to atria
why quick transmission of heart beats
-quick transmission for rapid contraction
-cardiac cells connected by gap junctions inside interrelated discs
-intercelated discs contain desmosomes which resist mechanical stress
-enables resist stretching as occurs every time heart fills with blood
describe electrocardiograms
vena cava=
from body to heart
aorta=
from heart to body
oxygenated on which side
my left, diagram right
semilunar valve
valve between left ventricle and aorta and right ventricle and pulmonary artery, prevents back flow
ventricular septum=
muscles between ventricles, otherwise oxygenated and does would be mixed
bicsupid/tricuspid valve?
left bicuspid, right triscuspid
gas exchange in pulmonary circuit
O2 moves into blood, CO2 moves out
gas exchange in pulmonary circuit
O2 moves into blood, CO2 moves out
gas exchange in systemic circuit
O2 moves out, CO2 moves into blood
trace path of electrical signal through conduction system of heart
1) impulse at SAN of right atrium, travels to AVN
2)AVN transmits less rapidly, 0.1s delay, down to b8ndle of his
3)AP travel down apex to purkyne fibres
myogenic
heart signals itself
authorhythmicity
generates own rhythm
pacemaker cells
spontaneously generate action potentials-found in SAN, AVN
conduction fibres
conduct action potential, have low electrical resistance
why delay in transmission of AP from AV node
0.1s delay-makes sure ventricles contract after atria emptied
electrical activity in pacemaker cells
fire AP spontaneously, doesn’t have steady resting potential
-After AP, pacemaker depolarises until membrane potential reaches threshold (-55mv)
cardiac contractile cells
look paper and one note
what is ECG
-records electrical current through heart
einthovens triangle
right arm, left arm, left leg
-leads calculated
-lead II at 60, lead III at 120
p wave
atrial depolarisation (contraction) 0.1s
QRS wave
ventricular depolarisation (contraction)- 0.08-0.12s
T wave
ventricular repoalrisaiton (relaxation)-0.16-0.27s
P-Q
AV node conduction time 0.12-0.21s
Q-T
ventricular systole- 0.3-0.43s
t-q
ventricular diastole 0.55-0.7s
R-R
time between heart beats 0.85-1s
arrhythmias
abnormal SA firing causes fast (more than 100bpm)/slow heart (less than 50bpm) rates
3rd degree heart block
-no conduction through AV node, causing dissociation between atrial and ventricular contractions
premature atrial contraction
depolarisation can occur from electrical signal outside conduction pathway
ventricular fibrillation
no longer synchronised heart beats, can’t pump blood round effectively
-deadly
atrial fibrillation
weakness but not deadly , ventricles still contract sufficiently
