conduction system Flashcards
in which layer does the contraction and relaxation happen?
myocardium layer
whats allows the cardiac tissue to contract and relax at the same time?
intercalated discs
whats forms an intercalated discs?
1- gap junction
2- desmasomes
whats the pacemaker of the heart?
SA node
what nerve supply does the sa node recieves?
autonomic nerve fibers
whats the anatomical position of SA node?
back wall of the right atrium at the superior end of the crista terminalis in front of SVC opening
whats the node located between atrium and ventricles?
AV node
whats the anatomical position of AV node
bottom right of atrium near the septum js above the coronary sinus opening
why is theres a delay in av node? and whats the reason behind it?
due to less gap junctions
and its allows ventricular filling and atrium to finish contracting
where do the signals go after AV node?
bundle of his, right and left branches
where are the purkinje fibers located?
spread with the muscle wall of the ventricle
wheres the fastest conduction?
P fibers
wheres the slowest conduction?
AV node
what happens when theres a complete bundle block?
dissociation in the rate of contraction of atria and ventricles
what is the most cause of defective conduction through AV bundle?
Atherosclerosis of the coronary arteries which causes diminished supply to the conducting system
whats the innervation of the heart?
1- sympathetic
2- parasympathetic
whats the name of the network of the nerves supplying the heart
cardiac plexus
what forms cardiac plexus?
right and left vagus nerve ( para )
sympathetic trunk
wheres the location of cardiac plexus?
below the arch of the aorta
wheres the main control of the heart found?
medulla oblongata
whats forms the cardioregulatory center?
1- cardioacceleratory center
2- cardioinhibitory center
whats the othe name of cardioacceleratory center and wheres it found?
pressor center and its found on the upper part of medulla oblongata
whats the other name of cardioinhibitory center and where is it located?
depressor center and its found in lower part
whats the function sympathetic nervous system?
+ inotropic –> increase contractility ( cuz it increases ca influx )
+ chromotropic —-> increase firing rate
+dromotropic ———> increase the conduction
recall how it works from physiology
Fight or flight
whats the function of parasympathetic system on the heart?
- chromotropic —> decrease firing rate
- dromotropic —–> decrease conduction
which is normally more dominant in resting conditions?
parasympathetic
whats the course of sympathetic nerve?
exist the medulla
Travel down the spinal cord with SHORT myelinated preganglionic FIBERS to the sympathetic GANGLIA
the preganglionic are shorter
the postganglionic are longer
which segment of the spinal cord has preganglionic fibers innervating the heart?
T1 - T5 segment
what does the LONG POSTGANGLIONIC sympathetic fibers innervate
1- SA node ( + chromotropic )
2- AV node ( + dromotropic )
3- CARDIAC MUSCLE FIBERS ( remember + inotropic effect )
4- coronary arteries ( vasodilation in fight or flight )
describe the course of the parasympathetic
exist the medulla as VAGUS nerve and ITS LONG PREGANGLIONIC efferent fibers ( sympathetic was short )
the long preganglionic will form synapses with the SHORT postganglionic fibers
opposite to sympathetic has short preganglionic and LONG postganglionic
what does short postganglionic parasympathetic fibers innervate?
1- SA node (- chromotropic )
2- AV node ( - dromotropic )
3- coronary artery ( constriction during rest )
no innervation to the myocardium cuz no effect on contractility .
compare the axons branches of sympathetic and parasympathetic
axons of symp are highly branches and work on many organs
axons of para have fewer branches and are only localized
compare the postganglionic fibers or sympathetic and parasympathetic
sympathetic :
preganglionic –> short
postganglionic –> LONG
parasympathetic :
preganglionic –> LONG
postganglionic –> short
