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1102 > Cardiac System > Flashcards

Cardiac System Flashcards

1
Q

Describe the conduction system of the heart.

A

Specialised tissue conducts nerve impulses, SA & AV node, bundle of His, bundle branches & Purkinje fibres.

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2
Q

Describe the hearts nerve supply.

A

Nerve branches from sympathetic & parasympathetic divisions of autonomic NS.

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3
Q

State the functions of the pericardium.

A
  • protects & anchors heart
  • prevents overfilling w blood
  • serous fluid reduces friction
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4
Q

Pulmonary circuit

A

blood to & from lungs (vena cava & pulmonary artery)

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5
Q

Systemic circuit

A

Blood to & from body (pulmonary vein & aorta)

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6
Q

arteries are ___ vessels

A

pressure

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7
Q

veins are ___ vessels which can ___ to match blood volume

A

capacitance, distend

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8
Q

Diastolic Phase

A

myocardium relaxes

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9
Q

Systolic phase

A

myocardium contracts

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10
Q

State the phases of cardiac cycle.

State the valves involved.

A 
1. Atrial diastole & systole
AV valves open.
2. Ventricular filling: mid-to-late diastole
3. Ventricular systole
AV valves close (lubb)
4. Ventricular diastole
semilunar valves close (dubb)
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11
Q

Ventricular systole:
Atria ___ , rising ventricular pressure closes __ valves. -___ sound.
_____ _____ phase

A

relax, AV, lubb

Isovolumetric contraction

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12
Q

Ventricular diastole:
Ventricles ___ , closes ___ valves.
___ sound.

A

relax, semilunar.

dubb

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13
Q

State the AV valves

A

mitral (bicuspid) & tricuspid

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14
Q

State the semilunar valves

A

Aortic & pulmonic

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15
Q

Tachycardia

A

High resting heart rate

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16
Q

Bradycardia

A

Low resting heart rate.

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17
Q

Pulse

A

Surge in arterial pressure.

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18
Q

Cardiac Output (CO)

A

Vol. of blood pumped by each ventricle per min

CO (mL/min) = HR (bpm) x SV (mL/b)

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19
Q

What is cardiac reserve?

Compare that of an athlete to an average person.

A

difference between resting & max. CO.

Athlete CR is GREATER.

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20
Q

What factors determine heart rate?

A

Autonomic innervation & hormones

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21
Q

What factors determine stroke vol.?

A

End-diastolic & systolic vol.

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22
Q

Stroke Volume (SV)

A

Vol. of blood pumped LEFT by ventricle per beat.

SV = EDV - ESV
end diastolic/systolic vol.

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23
Q

Blood pressure

A

Force exerted by blood against blood vessel walls

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24
Q

Function of baroreceptors

A

Detect change in BP.

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25
Q

What does BP 120/80 show

A

PUMP (peak) pressure / FILL (minimum) pressure

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26
Q

PRELOAD

A

Degree of stretch before contraction.

= EDV

27
Q

AFTERLOAD

A

Pressure required to eject blood from ventricles.

28
Q

Frank-Starling Mechanism

A

The change of hearts force of contraction in response to a change in venous return.

Increased venous return increases EDV hence preload.

Myocyte stretching increases force generation.

29
Q

__ afterload –> &laquo_space;CO

Cardiac Output (CO)

30
Q

__ contractility –>&raquo_space;CO

31
Q

> > CO = __HR X SV

32
Q

State the 5 features of the cardiac conduction system

A

SA node, AV node, Bundle of His, bundle branches, purkinje fibres.

33
Q

SA node

A

Pacemaker

- generate spontaneous action potentials.

34
Q

AV node

A 
Controls heart rate.
Delays impulse (~0.1s) from SA node before it passes down ventricles - allows atrial emptying.
35
Q

Purkinje fibres

A

DISTRIBUTE IMPULSE across ventricular myocardium

36
Q

Where does depolarisation occur in heart.

A

From SA node across atria.

-

37
Q

Describe impulse conduction through heart.

A 
DEPOLARISATION across SA  node & atria.
~0.1s delay at AV node. 
Atrial contraction.
Impulse travels along interventricular septum within AV bundle & purkinje fibres to right ventricle.
Impulse distributed by Purkinje fibres.
Ventricular contraction occurs.
38
Q

Speed of action potential propagation in cardiomyocytes is ____ due to ___________________

A

Slow, gap junctions & small diameter of fibres.

39
Q

Speed of action potential propagation in skeletal muscle is ____ due to

A

Fast, larger diameter of fibres.

40
Q

Describe the characeristics of cardiomyocytes.

A

Striated, mono-nucleated, branched, connected by intercalated discs w desmosomes.

41
Q

Describe the Sliding Filament Theory.

A
  • Ca2+ binds to TN-C on thin filaments
  • Exposed actin binding site for myosin head
  • ATP hydrolysis -> actin-myosin conformational change
  • RATCHET actin-myosin complex & sarcomere shortens
  • Ca2+ dissociates from TN-C, myosin unbinds from actin
42
Q

Describe cardiomyocyte contraction

A
  • Ca2+ enters via L-type
  • CICR (Ca2+&raquo_space;>)
  • Ca2+ interacts w TN-C
  • Actin binding site freed
  • Actin moves over myosin (contraction)
  • IC Ca2+ reabsorbed into SR via SERCA pump, & removed from cell via Na+/Ca2+ exchanger & ATP-dependent Ca2+ pump.
  • Ca2+ dissociates from TN-C & actins binding site inhibited.
43
Q

Resting potential ~ __ equilibrium potential

44
Q

Resting potential = __mV

45
Q

Action potentials induce __ channel opening

46
Q

State the phases of an Action Potential:

A 
p0 Rapid DEPOLARISATION
p1 Initial REPOLARISATION
p2 Plateau 
p3 REPOLARISATION
p4 Resting POTENTIAL
47
Q

Outline the phases of an action potential

A

EXCITATION:
p0 :&raquo_space;> Na+ permeability, membrane potential&raquo_space;>
p1 : K+ permeability&raquo_space;>, CICR (L type open)
p2 : K+ balances Ca2+ flow. Cardiomyocyte contraction.
p3 : K+ channels remain open. Membrane potential falls ~E(k)
p4 : resting potential = -85mV

48
Q

Excitation depolarisation threshold potential = __mV

49
Q

What is pacemaker tissue?

A

Areas of unstable resting potential

50
Q

Rhythmic ____ -> rhythmic ____

A

Depolarisation, contraction

51
Q

Automaticity =

A

Ability to spontaneously depolarise & trigger AP

52
Q

Where is automaticity active in the heart?

A

SA & AV nodes & Bundle of His.

53
Q

____ node is the primary pacemaker of the heart, determining __ __ .

1 depolarisation = __ heartbeat(s)

A

Sinoatrial
Heart rate

1

54
Q

Characteristics of sinoatrial node pacemaker cells

A

No true resting potential

Generate regular spontaneous action potentials.

55
Q

How is the cardiac cycle regulated?

A

Sympathetic & parasympathetic NS.

Cardiac centres in medulla oblongata receive input from hypothalamus.

56
Q

How does the parasympathetic system regulate the cardiac cycle?

A

Cardioinhibitory centre - vagus nerve
SA & AV nodes
ACh secreted - hyperpolarises
«< HR

57
Q

How does the sympathetic system regulate the cardiac cycle?

A

Cardioaccelerator centre activates cardiac nerves.
Norepinephrine secreted
» contractility

58
Q

Electrocardiogram: P wave

A

atrial depolarisation

59
Q

Electrocardiogram: QRS complex

A

ventricular depolarisation

60
Q

Electrocardiogram: T wave

A

ventricles repolarised

61
Q

Electrocardiogram: PR interval

A

contraction -> relaxtaion.

start of atrial to ventricular depolarisation

62
Q

Electrocardiogram: Q-T interval

A

time for a single cycle of depolarisation & repolarisation.

63
Q

State the 3 groups of pacemaker cells

A

SA node
AV node,
Bundle of His & Purkinje fibres

1102 (14 decks)

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