Chapter 18.5 Electrical Conduction-Cardiovascular System Flashcards
What does conduction consist of?
specialized cardiac muscle tissue that generates and distributes action potentials
What are components of conduction system?
Sinoatrial (SA) node (pacemaker)
Atrioventricular (AV) node
Atrioventricular (AV) bundle (bundle of His)
Right and left bundle branches, and
Purkinje fibers
What is meaning of automaticity in relation to cardiac muscle tissue?
It means Cardiac muscle tissue contracting on its own in absence of neural or hormonal stimulation
What are part of heart’s conducting system and is also known as?
cells responsible for initiating and distributing stimulus to contract, which are also known as cardiac conduction system or nodal system.
What is SA NODE called
Pacemaker
What does SA Node initiate?
Initiates AP(Action Potential) ~100 times faster than any other region in conducting system
What is SA Node influenced by?
Influenced by neurotransmitters and hormones
What can ANS (sympathetic and parasympathetic) modify but does not establish?
Can modify HR(Heart Rate), but does not establish heart’s fundamental rhythm
Where is SA node located and how does it contribute to conduction system?
Located at RA(Right Atrium) wall, inferior to SVC(superior vena cava) opening.
And AP(Action Potential) spontaneously arises and then conducts to both atria so that they finish contracting at same time
Where is AV NODE located and how does it contribute to conduction system?
Located at Interatrial septum, inferior to coronary sinus and AP slows considerably, allowing for atria to empty
Where is AV Bundle (Bundle of His) located and how does it contribute to conduction system?
Located at Interventricular septum and it is Only site where AP can conduct from atria to ventricles
How do Right and Left Bundle Branches contribute to conduction system?
Extend through interventricular septum towards apex
Where is Purkinje Fibers located and how does it contribute to conduction system?
Originate near apex, extends upwards and AP rapidly conducts from apex to remainder of ventricular myocardium
What is heart innervated by?
innervated by both sympathetic and parasympathetic nerve fibres
What does SNS innervate?
entire heart muscle and node cells which release NE
What does Parasympathetic system innervate?
node cells which releases primarily acetylcholine
What happens when there is reduction in potassium permeability?
Fewer K+ ions move out of cell when membrane potential is negative
How do voltage-gated sodium channels in SA node contribute to depolarization?
They open when membrane potential is negative (-60mV), allow positively charged Na+ to move into cell which end up leading to depolarization
As membrane depolarizes, what does calcium channels opening allow?
Allow further influx of positively charged ions (Ca2+) and e SA node cells to reach threshold level;causes action potential
What does Electrocardiogram (ECG) record
electrical changes that accompany heartbeat
What is charge of Resting Membrane Potential?
negative, so change towards positive =depolarization occurring
What are 3 Waves identified on ECG
P Wave (~0.08 sec), QRS Complex (~0.12 sec), and T Wave (~0.16 sec)
What does P wave represent in electrocardiogram (ECG), and what happens after it?
Represents depolarization from SA node through atria and Atrial contraction follows
What does QRS complex represent in electrocardiogram (ECG), and what happens after it?
Represents Ventricular depolarization and is followed by
ventricular contraction
