lecture 9 - the excitable heart Flashcards
(35 cards)
What are the 2 types of cells that make up the heart?
Electrical and contractile
What is the alternative name for cardiac electrical cells?
Conduction cells
What percentage of heart tissue is made up of electrical cells?
1%
What is the appearance of cardiac electrical/conduction cells?
Pale striations - due to low actin and myosin as contraction is redundant
Purkinje cells and AV nodal cells are examples of what type of cardiac cell?
Electrical/conduction cells
What is the appearance of cardiac contractile cells?
Striated, due to actin and myosin filaments forming sarcomeres.
Cardiomyocytes are what type of cardiac cell?
Contractile cells
How do action potentials propagate along and between cardiac cells?
They propagate along the surface membrane of both electrical and contractile cells.
Where do depolarisations that initiate contraction originate in the heart?
The sinoatrial (SA) node
How do electrical signals spread between neighbouring cells in cardiac tissue?
Via gap junctions
How do gap junctions facilitate the transmission of an electrical signal between cardiac cells?
They are pores with low resistance to ionic current, allowing it to flow to the surrounding cells.
How are conduction cells connected in terms of signal transmission?
By gap junctions
How are contractile cells connected in terms of signal transmission?
Gap junctions
How are conduction cells and contractile cells connected in terms of signal transmission?
Gap junctions
Why is the heart described as a ‘functional syncytium?
Because all of the cardiac cells behave and contract as one
What are are the key components (in order) of the heart’s conduction pathway?
SA node, internodal bundles, AV node, AV bundle branches (left and right), purkinje fibres
What connects the SA node and the AV node?
Internodal bundles
Where is the SA node located?
At the superior of the right atrium
Where is the AV node located?
At the inferior of the right atrium
Where do the AV bundle branches run?
From the AV node, down the surface of the interventricular septum to the apex of the heart, then branch into perkinje fibres.
What are the 2 AV bundle branches?
Left and Right
Where do purkinje fibres originate?
At the end of the AV bundle branches at the apex of the heart
Where do purkinje fibres run?
Up the left and right ventricles from the apex of the heart.
What is the function of the AV node?
Helps to transmit electrical signals from the atria to the ventricles. Provides a short delay in transmission to allow the atria to finish contracting before the ventricles start contracting.
