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Year 1 Week 17 - Cardiac Cycle > Cardiac Excitation > Flashcards

Cardiac Excitation Flashcards

1
Q

excitation pathway

A

sinus rhythm - HR controlled by SA node
action potential activates atria
atrial AP activated AV node
AV node activates bundle of His/purkinje fibres
purkinje fibres activate ventricles

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2
Q

features of AV node

A

small cells
slow conduction velocity
introduces delay of 0.1s

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3
Q

myogenic

A

generates own action potentials spontaneously
e.g. cardiac muscle

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4
Q

action potential development at SA node

A

spontaneous

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5
Q

AP conduction from cell to cell

A

via intercalated discs with gap (nexus) junctions

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6
Q

what is the SA node essentially

A

the pacemaker of the heart

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7
Q

SA node action potential - pacemaker potential

A

increased gCa
increased gNa
decreased gK

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8
Q

SA node action potential - AP upstroke

A

increased gCa

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9
Q

SA node action potential - repolarisation

A

increased gK
decreased gCa

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10
Q

SA node action potential - noradrenaline

A

increased gNa
increased gCa

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11
Q

SA node action potential - acetyl choline

A

increased gK
decreased gCa

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12
Q

neurogenic

A

needs a nervous impulse to initiate a contraction
e.g. skeletal muscle

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13
Q

length of skeletal muscle AP

A

50msec

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14
Q

length of cardiac muscle AP

A

500msec

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15
Q

what does the action potential control in the heart vs skeletal muscle

A

controls during of contraction in heart
in skeletal it acts only as a trigger

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16
Q

what does g mean - i.e. gK, gNa, gCa

A

conductance

17
Q

ion currents during action potential - skeletal vs cardiac

A

skeletal - simple
cardiac - complex

18
Q

currents responsible for cardiac AP - depolarisation

A

large gNa

19
Q

currents responsible for cardiac AP - plateau

A

small gNa
increased gCa
decrease gK

20
Q

currents responsible for cardiac AP - repolarisation

A

decrease gCa
increase gK

21
Q

what is released from the sarcoplasmic reticulum

A

calcium
Ca entry from outside required for heart cells - ‘Ca induced Ca release’

22
Q

relaxation (Ca reduction) - uptake of Ca by sarcoplasmic reticulum

A

via an ATP driven Ca pump

23
Q

modes of exit of Ca from a cell

A

ATP driven Ca pump (weak)
Na-Ca exchange protein (energy from Na entry gradient)

Year 1 Week 17 - Cardiac Cycle (4 decks)

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