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BRS 6 Cardio and respiratory > Control of Heart Function > Flashcards

Control of Heart Function Flashcards

1
Q

What three categories can the main anatomical components of the heart be categorized into?

A
  1. Muscle cells - cardiomyocytes
  2. Specialised electrical cells
  3. Vessels
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2
Q

Which cell type in the heart is most prominent in controlling heart function?

A

Electric cells

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3
Q

What is the pacemaker of the heart?

A

The Sinoatrial Node

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4
Q

What limits does the SAN work to keep the heart rate between?

A

60-100 bpm

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5
Q

Where is the SAN found?

A

At the junction of the cristae terminalis, upper wall of right atrium and opening of superior vena cava

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6
Q

What is the name given to the tracts between the SAN and the AV Node?

A

Internodal tracts

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7
Q

What is the tract which runs down the intraventricular septum?

A

Bundle of His

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8
Q

What are the fibres which project upwards around the ventricles from the apex of the heart?

A

The Purknje Fibres

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9
Q

Where is the AVN found?

A

At the triangle of Koch at the base of the right atrium

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10
Q

What are purkinje fibres?

A

Specialised conducting fibres

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11
Q

Does the AVN have pacemaker activity?

A

Yes - slow calcium mediated action potentials

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12
Q

What are the three main souces of control of the heart?

A

The kidneys, the central nervous system and the blood vessels

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13
Q

Which three phases does a nodal action potential have?

A

0, 3 and 4

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14
Q

What is phase 0?

A

The upstroke phase

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15
Q

What is Phase 1?

A

early repolarisation

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16
Q

What is phase 2?

A

Plateau phase

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17
Q

What is phase 3?

A

repolrisation

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18
Q

What is phase 4 in nodal and ventricular cells?

A

Pre-potential in nodal cells (Na+ influx)
Resting membrane potential in ventricular cells (Na/K ATPase)

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19
Q

What causes the upstroke (Phase 0) in nodal cells?

A

The influx of calcium from outside the nodal cell into the nodal cell

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20
Q

What causes the repolarisation seen in nodal cells?

A

Due to K+ efflux

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21
Q

What causes the pre-potential seen in SAN?

A

The slow flow of Na+ through a funny channel

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22
Q

How does the length of a cardiac muscle action potential differ from a nerve action potential?

A

Cardiac muscle action potential is much longer - 200-300ms compared with 2-3ms

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23
Q

What does the duration of the cardiac muscle action potential control?

A

The duration of the contraction of the heart

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24
Q

What type of contraction is required to produce an effective pump?

A

Long and slow contraction

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25
Q

How may phases does the Cardiac Muscle action potential have?

A

5

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26
Q

What are the 5 phases of the cardiac muscle action potential?

A 
Phase 0 - Upstroke
Phase 1 - Early Repolarisation
Phase 2 - Plateau
Phase 3 - Repolarisation
Phase 4 - Resting Membrane potential
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27
Q

What is meant by the absolute refractory period?

A
  • The period in which no action potential can be initiated regardless of stimulus intensity
  • Limits the rate at which the heart can beat at
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28
Q

What is the relative refractory period?

A

Period of time after the absolute refractory period in which the heart can elicit another action potential if a large enough stimuli is provided

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29
Q

Why is the plateau phase of the cardiac muscle cell action potential so important?

A

L type Ca2+ Channels open slowly resulting in Ca2+ influx, which maintains the cell at the level of depolarisation - this is essential for generating a large force of contraction

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30
Q

What triggers the repolarisation phase in cardiac muscle cells?

A

The efflux of K+ from the cell

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31
Q

What happens when the Cardiac muscle has been sufficiently repolarised?

A

The K+ channels close, returning the muscle cell to resting membrane potential

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32
Q

Why is Ca2+ influx essential for contraction?

A

Ca2+ is needed for the release of Ca2+ from the sarcoplasmic reticulum which then binds to troponin on muscle to shorten the fibres and contract it

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33
Q

Which ion is the upstroke more reliant on?

A

Na+

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34
Q

What does the autonomic nervous system that controls the heart comprise of?

A

The cardio-regulatory center and the vasomotor centers in the medulla

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35
Q

What nerve is responsible for the parasympathetic changes which are seen in the heart (decrease in heart rate)

A

Vagus nerve

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36
Q

What happens to the slope of Phase 4 (Pre-Potential) of the SAN Action potential during the parasympathetic response?

A

Decreases the slope

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37
Q

Which nerves are involved in the sympathetic control of the heart to increase heart rate?

A

Cardiac nerves from the lower cervical and thoracic ganglia

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38
Q

What affect does the sympathetic response have on the slope of Phase 4 in the sympathetic nervous system?

A

It increases the slope

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39
Q

What length are parasympathetic pre-ganglionic fibres?

A

Long

40
Q

What length are parasympathetic post-ganglionic fibres?

A

Short

41
Q

What length are sympathetic post-ganglionic fibres?

A

Long

42
Q

What length are sympathetic pre-ganglionic fibres?

A

Short

43
Q

What NT is used at both pre and post-ganglionic synapses in parasympathetic?

A

ACh

44
Q

What NT is used at sympathetic pre-ganglionic synpases?

A

ACh

45
Q

What NT is used at sympathetic post-ganglionic synpases?

A

Noradrenaline

46
Q

What receptors are used at both sympathetic and parasympathetic pre-ganglionic synapses?

A

nicotinic receptors

47
Q

What receptors are found at parasympathetic post-ganglionic synpases?

A

muscarinic receptors

48
Q

What receptors are found at sympathetic post-ganglionic synapses?

A

Adrenergic receptors

49
Q

What does the parasympathetic system control?

A

Heart rate

50
Q

What does the sympathetic system control?

A

Circulation

51
Q

Which receptors found in the heart are responsible for an increase in heart rate?

A

Beta 1 and Beta 2 Receptors

52
Q

What type of receptors are Beta1 and Beta2?

A

They are adrenoreceptors

53
Q

What is the the result of an increase in chronotrophy?

A

HR Increases

54
Q

What is the the result of an increase in lusitrophy?

A

The rate at which the myocyte relaxes increases

55
Q

What is the the result of an increase in ionotrophy?

A

Contractility increases

56
Q

What is the the result of an increase in dromotrophy?

A

Conduction velocity increases

57
Q

What are examples of adrenergic agonists?

A

Noradrenaine and the circulating hormone epinephrine

58
Q

What receptors in the heart do parasympathetic neurotransmitters stimulate?

A

M2 muscarinic receptors

59
Q

Why do beta receptors result in an increase in chronotropy, dromotropy, inotropy and lusitropy?

A

The activation of beta receptors results in the stimulation of secondary messenger systems
Adenylyl cyclase is stimulated to make protein kinase A

60
Q

Where is the vasomotor system located?

A

Bilaterally in the reticular substance of medulla and lower third of pons

61
Q

What three areas is the vasomotor system composed of?

A

The Pressor Area - vasoconstrictor
The Depressor Area - vasodilator
The Cardio-regulatory inhibitory area

62
Q

What does the lateral portion of the vasomotor center control?

A

Controls heart activity by influencing heart rate and contractility

63
Q

What does the medial portion of the vasomotor center control?

A

Transmits parasympathetic signals via the Vagus nerve to the heart that tend to decrease heart rate

64
Q

Where does the vasomotor center transmit impulses to?

A

The heart and almost all the blood vessels - through the spinal cord

65
Q

what is the network of nerves which supplies the heart called?

A

The cardiac plexus

66
Q

What does the right vagus nerve primarily innervate?

A

The Sinoatrial Node

67
Q

what does the left vagus nerve primarily innervate?

A

The AV Node

68
Q

What happens to Beta 1 Receptors in the heart during heart failure?

A

They become downregulated

69
Q

What is the result of NA binding to alpha 1 adrenoreceptors found on myocytes?

A

Produces small increases in inotrophy - increase in contractility

70
Q

What is the effect of ACh released from the vagus nerve binding to M2 receptors in the heart - especially SAN and AVN?

A

Decrease in chronotropy and dromotropy in the heart

Decrease in inotropy and lusitropy in the atria

71
Q

What effect does sympathetic innervation on the kidney have on glomerular filtration?

A

Reduces glomerular filtration

72
Q

What affect does sympathetic innervation on the kidneys have on blood volume?

A

Less filtration means less Na+ is excreted
Blood thus has more Na+ and water
Thus higher blood volume

73
Q

What detects the change in blood volume?

A

Venous volume receptors in the heart

74
Q

How does a higher blood volume lead to higher blood pressure?

A

High blood volume = High renin = More Angiotensinogen = More Angiotensin II = More Aldosterone = Vasoconstriction = increase in blood pressure

75
Q

Activation of what receptor causes Increase Renin secretion?

A

Activation of the Beta-1 Adrenoreceptors

76
Q

How does the GFR decrease with sympathetic innervation?

A

Sympathetic nerves stimulate the alpha1 Adrenoreceptors via NA release which causes vasoconstriction, and therefore less GFR and Less Na+ excretion

77
Q

What effect does an increase in blood volume have on inotropy?

A

It will increase inotrophy

78
Q

What do baroreceptors detect?

A

Changes in blood pressure and volum

79
Q

Blood volume changes is due to what system?

A

Decrease GFR due to sympathetic stimulation

80
Q

Blood pressure changes is due to what system?

A

Renin-angiotensin-aldosterone system

81
Q

When baroreceptors firing rate reduces, what happens to SNS activity?

A

It increases to increase heart rate

82
Q

When baroreceptors firing rate increases, what happens to SNS activity?

A

Decreases, so reduction in chronotropy

83
Q

What nerves do volume sensors send signals through?

A

glossopharyngeal and vagus

84
Q

What nerves do pressure sensors send signals through?

A

Glossopharyngeal and vagus

85
Q

Where are pressure sensors found that change baroreceptor firing?

A

In the arterial circuit

86
Q

Where are volume receptors found?

A

In large pulmonary vessels

87
Q

What 4 factors effect venous volume distribution?

A

Peripheral venous tone
Gravity
Skeletal muscle pump
Breathing

88
Q

What is meant by the central venous pressure?

A

The mean pressure of the right atrium - determines how much blood flows back to the heart

89
Q

Which area of the cardiovascular system contain the biggest reservoir of blood

A

Veins and venules

90
Q

What does constriction in veins determine?

A

Compliance (reduced) and venous return (increased)

91
Q

Which physiological change will cause an immediate increase in baroreceptor firing

A

Increased central venous pressure

92
Q

What does constriction in arterioles determine?

A

Blood flow to downstream organs
Mean Arterial Pressure
Pattern of Flow to Organs

93
Q

What are two endothelium derived vasodilators?

A

nitric oxide and prostacylin

94
Q

What are two endothelium derived vasoconstrictors?

A

Endothelins and thromboxane A2

95
Q

How does ADH cause vasoconstriction?

A

Binds to V1 receptors on smooth muscle

96
Q

What is the most potent vasoconstrictor?

A

Angiotensin II

BRS 6 Cardio and respiratory (26 decks)

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