Lectue 9 - The Excitable Heart Flashcards
Contractile cells of the eart
- striated appreance
- high actin and myosin
- ‘ working myocardial cell’
- 99%
Conductile cells of the heart
‘Pale’ striated appearance
- low actin and myosin
- AV nodal cells
- purkinje cells
- 1%
How does AP properget along the surface membrane of electrical and contractile cells
- depolarisation starts at the sinoatrial node (SA)
- this signal spreads to neighbouring cells
- in a contractile cell: increased cytosolic Ca2+ level, A-bridge attachment and contraction
How does AP properget along the surface membrane of electrical and contractile cells - where does delpoleration start
- depolarisation starts at the sinoatrial node (SA)
What connects cardiac cells
- intercollated disks - connect most cells of the heart
- gap junctions
- pores with low resistance to ionic current (ions can flow)
- allow current flow between adjacent cells
Gap jusnctions and how they help spread impulse
- all joined together via gap junctions, intercollated discs
- a signal in one place will spread right through myocardial via conduction pathway
The conduction pathway
The conduction pathway
Yapping
SA node in right atrium
Interatrial bundle connects right and left atrium - passing message quickly to left atrium - both essentiallly activated at same time
Yapppp
- Action potential originates in the SA node in the right atrium, then fires (information) through interatrial bundle (spreading from cell to cell) activating left atrium
- calcium is released in atrium, both atriums contract
- the AV node sits between atrium and ventricles and gets its information from the SA node via the internodal bundles
- conduction through AV node is slow - allowing atria to contact and relax first
- AV bundle forms AV bundle branches form the inter ventricular septum - spreading down to the APEX and back around to walls of myocardium allowing it to be depolarised quickly
What allows the atrium and ventricales to contract at different times
AV node
Where do u most wanna squeezes the heart
- at the bottom - that’s why the Perkinji fibres wrap around heart for contraction - cointidaated contration
Conduction pathway
- starts at SA node
- ends at ventricles
- SA node is known as the phase maker as it sets the pace
- AV node pauses conduction signal so atria can contract and relax before ventricles start contracting
- conduction travels down to the bottom of that heart then back up ventricular walls so that blood is squeezed out like toothpaste
Quiencese means
Quiet
Venrtricles depolarise from…
The bottom up
Excitation and condition pathway - relation and contraction
Electrocardiogram: ECG
- ‘ leads’ - virtual line between two surface electrodes
- a single lead detects a difference between electrodes (measures a change in voltage)
- (depolarisation and repolarisation)
- recorded as a trace not a number - below
ECG trace throughout excitation and the conduction pathway
P wave: Indicates depolarisation
Flat line: full depolarisation - thing is changing
Big QSR spike: artia repolarsing (a change) and ventricles depolarising (a change)
Flat line: all depolarised - nothing change
T wave: stimulus is gone and it repolarises
Shown as time through myocardium getting depolarisation
ONLY DETECTS CHANE
Everything put together
One heart beat…
- length of cycle depends on heart rate
Electricle vs conductile cells of the heart
