Lecture 9: The Excitable Heart Flashcards
What is the appearance of electrical /conduction cells?
Pale striated appearance
What is the appearance of contractile cells?
Striated appearance
What are electrical/conduction cells made of?
Low actin/myosin
What are contractile cells made of?
High actin/myosin
Where do action potentials propagate in cardiac cells?
Along the surface membrane of electrical and contractile cells
Where does depolarisation in the heart start?
The Sinoatrial node
What connects the cells of the heart?
Intercalated disks
What do gap junctions do?
Allow current flow between adjacent cells
What are gap junctions?
Pores with low resistance to ionic current
Where are gap junctions found?
Between contractile and electrical/conduction cells
What is a functional syncytium?
Many cells functioning as one unit
Following the sinoatrial node where does an electrical current go?
Internodal bundles/interatrial bundle
Following the internodal bundles where does an electrical current go?
AV node
Following the AV node where does an electrical current go?
AV bundle
Following the AV bundle where does an electrical current go?
Right/left bundle branches
Following the left/right branches where does an electrical current go?
Purkunje fibers
What does the AV node do to an electrical impulse?
It briefly pauses it, allowing the atria to finish contracting
Why is the wiring of the heart conduction system done in the manner that it is?
To follow the direction of blood flow through the heart
What happens corresponding to the P wave during the excitation and the conduction pathway?
Left/right atrium depolarise and signal is arriving at this part of the heart therefore contraction is occurring
What happens corresponding to the base line following the P wave during the excitation and the conduction pathway?
Both atria are fully depolarised therefore in full contraction and signal is being held at the AV node
What happens corresponding to the QRS complex during the excitation and the conduction pathway?
Atria are repolarising as signal has left whilst AV node allows signal through the septal wall
What happens corresponding to the base line following the QRS complex during the excitation and the conduction pathway?
Ventricles are fully depolarised and contracting as signal has moved through purkinje fibres
What happens corresponding to the T wave during the excitation and the conduction pathway?
Repolarization of the ventricles begins as blood has been pushed out
What happens corresponding to the base line following the T wave during the excitation and the conduction pathway?
Ventricles fully repolarize
What does an ECG measure?
Electrical signals in your heart
What is depolarisation at the atria shown by on an ECG?
P wave
What is full depolarisation of the atria shown by on an ECG?
A base line
What is repolarised atria and depolarising ventricles shown by on an ECG?
QRS complex
What is full depolarisation of ventricles shown by on an ECG?
A base line
What is repolarisation of the ventricles shown by on an ECG?
T wave
What does ‘lubb’ reference in heart sounds?
The atrioventricular valves closing
What does ‘Dubb’ reference in heart sounds?
The semilunar valves closing
