Exciting the heart Flashcards
2 populations of cells in the heart
Electrical (1%) and contractile (99%)
Conducting cells have
- Low actin and myosin
- Pale appearance
- AV cells and purkinje fibres
Contractile cells have
- Lots of actin + myosin
- Striated appearance
- myocardial cells
How is Depol spontaneous
Due to Sinoatrial node
What happens after depol happens
This signal spreads to neighbouring cells (dont need nerves)
* In a contractile cell: increased cytosolic Ca2+ level, X-bridge attachment and
contraction
* How does the impulse spread betw
How are cells joined
Intercalated discs
Space between intercal discs
Pores
What are the gap junctions (pores)
Pores with low resistance to
ionic current
– allow current flow between
adjacent cells
How do Gap junnctions help
- SNA depols
- Signal carried through gap junction
- Along conduction pathway
- Between electrical and contractile
cells - Between contractile cells, activates other cells and coordinates
Why is there a pause at the AV node
To allow the artrium to contract - pause – then the vens get the signal to contract
Electrical wiring
SNA –> interatrial bundle –> internodal bundles –> AV node –> AV bundles –> purkinje fibres
Why do purkinje fibres run up the myocardium
To push the blood out
What does ECG detect
Change in cell voltage i.e the difference between the two leads that create a virtual line
What is the P WAVE
Atria start depol
FLat after P?
No change, pause at AV node
