conduction system

Question 1

in which layer does the contraction and relaxation happen?

Answer 1

myocardium layer

Question 2

whats allows the cardiac tissue to contract and relax at the same time?

Answer 2

intercalated discs

Question 3

whats forms an intercalated discs?

Answer 3

1- gap junction

2- desmasomes

Question 4

whats the pacemaker of the heart?

Answer 4

SA node

Question 5

what nerve supply does the sa node recieves?

Answer 5

autonomic nerve fibers

Question 6

whats the anatomical position of SA node?

Answer 6

back wall of the right atrium at the superior end of the crista terminalis in front of SVC opening

Question 7

whats the node located between atrium and ventricles?

Answer 7

AV node

Question 8

whats the anatomical position of AV node

Answer 8

bottom right of atrium near the septum js above the coronary sinus opening

Question 9

why is theres a delay in av node? and whats the reason behind it?

Answer 9

due to less gap junctions

and its allows ventricular filling and atrium to finish contracting

Question 10

where do the signals go after AV node?

Answer 10

bundle of his, right and left branches

Question 11

where are the purkinje fibers located?

Answer 11

spread with the muscle wall of the ventricle

Question 12

wheres the fastest conduction?

Answer 12

P fibers

Question 13

wheres the slowest conduction?

Answer 13

AV node

Question 14

what happens when theres a complete bundle block?

Answer 14

dissociation in the rate of contraction of atria and ventricles

Question 15

what is the most cause of defective conduction through AV bundle?

Answer 15

Atherosclerosis of the coronary arteries which causes diminished supply to the conducting system

Question 16

whats the innervation of the heart?

Answer 16

1- sympathetic

2- parasympathetic

Question 17

whats the name of the network of the nerves supplying the heart

Answer 17

cardiac plexus

Question 18

what forms cardiac plexus?

Answer 18

right and left vagus nerve ( para )

sympathetic trunk

Question 19

wheres the location of cardiac plexus?

Answer 19

below the arch of the aorta

Question 20

wheres the main control of the heart found?

Answer 20

medulla oblongata

Question 21

whats forms the cardioregulatory center?

Answer 21

1- cardioacceleratory center

2- cardioinhibitory center

Question 22

whats the othe name of cardioacceleratory center and wheres it found?

Answer 22

pressor center and its found on the upper part of medulla oblongata

Question 23

whats the other name of cardioinhibitory center and where is it located?

Answer 23

depressor center and its found in lower part

Question 24

whats the function sympathetic nervous system?

Answer 24

+ 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

Question 25

whats the function of parasympathetic system on the heart?

Answer 25

- chromotropic ---> decrease firing rate - dromotropic -----> decrease conduction

Question 26

which is normally more dominant in resting conditions?

Answer 26

parasympathetic

Question 27

whats the course of sympathetic nerve?

Answer 27

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

Question 28

which segment of the spinal cord has preganglionic fibers innervating the heart?

Answer 28

T1 - T5 segment

Question 29

what does the LONG POSTGANGLIONIC sympathetic fibers innervate

Answer 29

1- SA node ( + chromotropic ) 2- AV node ( + dromotropic ) 3- CARDIAC MUSCLE FIBERS ( remember + inotropic effect ) 4- coronary arteries ( vasodilation in fight or flight )

Question 30

describe the course of the parasympathetic

Answer 30

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

Question 31

what does short postganglionic parasympathetic fibers innervate?

Answer 31

1- SA node (- chromotropic ) 2- AV node ( - dromotropic ) 3- coronary artery ( constriction during rest ) no innervation to the myocardium cuz no effect on contractility .

Question 32

compare the axons branches of sympathetic and parasympathetic

Answer 32

axons of symp are highly branches and work on many organs axons of para have fewer branches and are only localized

Question 33

compare the postganglionic fibers or sympathetic and parasympathetic

Answer 33

sympathetic : preganglionic --> short postganglionic --> LONG parasympathetic : preganglionic --> LONG postganglionic --> short