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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
What does BP 120/80 show
PUMP (peak) pressure / FILL (minimum) pressure
26
PRELOAD
Degree of stretch before contraction. | = EDV
27
AFTERLOAD
Pressure required to eject blood from ventricles.
28
Frank-Starling Mechanism
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
__ afterload --> << CO Cardiac Output (CO)
Increased
30
__ contractility --> >>CO
Increased
31
>>CO = __HR X SV
>>
32
State the 5 features of the cardiac conduction system
SA node, AV node, Bundle of His, bundle branches, purkinje fibres.
33
SA node
Pacemaker | - generate spontaneous action potentials.
34
AV node
``` Controls heart rate. Delays impulse (~0.1s) from SA node before it passes down ventricles - allows atrial emptying. ```
35
Purkinje fibres
DISTRIBUTE IMPULSE across ventricular myocardium
36
Where does depolarisation occur in heart.
From SA node across atria. | -
37
Describe impulse conduction through heart.
``` 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
Speed of action potential propagation in cardiomyocytes is ____ due to ___________________
Slow, gap junctions & small diameter of fibres.
39
Speed of action potential propagation in skeletal muscle is ____ due to
Fast, larger diameter of fibres.
40
Describe the characeristics of cardiomyocytes.
Striated, mono-nucleated, branched, connected by intercalated discs w desmosomes.
41
Describe the Sliding Filament Theory.
- 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
Describe cardiomyocyte contraction
- Ca2+ enters via L-type - CICR (Ca2+ >>>) - 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
Resting potential ~ __ equilibrium potential
K+
44
Resting potential = __mV
-85mV
45
Action potentials induce __ channel opening
Na+
46
State the phases of an Action Potential:
``` p0 Rapid DEPOLARISATION p1 Initial REPOLARISATION p2 Plateau p3 REPOLARISATION p4 Resting POTENTIAL ```
47
Outline the phases of an action potential
EXCITATION: p0 : >>> Na+ permeability, membrane potential >>> p1 : K+ permeability >>>, 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
Excitation depolarisation threshold potential = __mV
-65mV
49
What is pacemaker tissue?
Areas of unstable resting potential
50
Rhythmic ____ -> rhythmic ____
Depolarisation, contraction
51
Automaticity =
Ability to spontaneously depolarise & trigger AP
52
Where is automaticity active in the heart?
SA & AV nodes & Bundle of His.
53
____ node is the primary pacemaker of the heart, determining __ __ . 1 depolarisation = __ heartbeat(s)
Sinoatrial Heart rate 1
54
Characteristics of sinoatrial node pacemaker cells
No true resting potential | Generate regular spontaneous action potentials.
55
How is the cardiac cycle regulated?
Sympathetic & parasympathetic NS. | Cardiac centres in medulla oblongata receive input from hypothalamus.
56
How does the parasympathetic system regulate the cardiac cycle?
Cardioinhibitory centre - vagus nerve SA & AV nodes ACh secreted - hyperpolarises <<< HR
57
How does the sympathetic system regulate the cardiac cycle?
Cardioaccelerator centre activates cardiac nerves. Norepinephrine secreted >> contractility
58
Electrocardiogram: P wave
atrial depolarisation
59
Electrocardiogram: QRS complex
ventricular depolarisation
60
Electrocardiogram: T wave
ventricles repolarised
61
Electrocardiogram: PR interval
contraction -> relaxtaion. start of atrial to ventricular depolarisation
62
Electrocardiogram: Q-T interval
time for a single cycle of depolarisation & repolarisation.
63
State the 3 groups of pacemaker cells
SA node AV node, Bundle of His & Purkinje fibres

1102 (14 decks)

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