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Medsci 142 Test 1 > Heart continued L7 > Flashcards

Heart continued L7 Flashcards

1
Q

Where is the location of the heart in males and immature females?

A

Level of Nipples T4

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2
Q

Where does the Apex of the heart point?

A

Anteriorly (front)
Inferiorly (down)
To the LEFT

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3
Q

What is the apex composed of?

A

Entirely the LV

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4
Q

What proportion of the heart is to the right of the midline(sternum)?

A

1/3

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5
Q

What proportion of the heart is to the left of the midline (sternum)?

A

2/3 and is Rotated slightly

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6
Q

Is the heart rotated?

A

Yes, is rotated slightly

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7
Q

What does the Right border of the heart consist of?

A

RA (due to the vertical rotation if superior and inferior vena cava)

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8
Q

What does the Inferior border of the heart consist of?

A

RV

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9
Q

What does the Left border of the heart consist of?

A

LV mainly ( a little bit of the LA sometimes)

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10
Q

What is the base of the heart?

A

The point at which the heart is attached/connected to the rest of the body

  • where the vessels enter and exit
  • the ventricles are free to move depending on how close to the base of the heart they are
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11
Q

What does the heart sit very close to?

A

The diaphragm

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12
Q

What is Cardiohypertrophy?

A

“Cardio” =heart
“hypertrophy”= enlarged
Cardiohypertrophy is the enlargement of the heart
this results in a boot shaped heart
This is shown in X-rays by a heart with a Cardiothoracic ratio of the heart : rib-cage-width ,which is greater than 50% of the width of the ribcage at its widest points (larger than normal)
Caused by aortic stenosis (“aorta outlet” “narrowing”)

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13
Q

What is the condition called when there is an enlarged boot shaped heart?

A

Cardio Hypertrophy

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14
Q

How do you know if a heart is enlarged?

A
  1. Use the borders as see if each border consists of it’s normal components (i.e. RB=RA IB=RV LB=LV)
  2. Use cardio Thoracic ratio (heart should be at or less than 50% of width of the ribcage at its widest points)/ If greater than 50% of the ribcage at its widest points = enlarged heart = cardiohypertrophy
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15
Q

What is the Cardio thoracic ratio?

A

The heart should be less than or at 50% of the width f the ribcage at its widest points

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16
Q

Does Aortic stenosis cause cardio hypertrophy, or does cardiohypertrophy cause aortic stenosis?

A 
Aortic Stenosis (narrowing of the heart) causes cardiohypertrophy (enlargement of the heart)
-the heart gets bigger due to the narrowed aortic outlet valve which makes the muscle work harder and thicken (and hence get bigger)
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17
Q

What is the condition when there is a narrowing of the heart?

A

Stenosis

-aortic stenosis when there is a narrowing of the LV Aortic outlet valve

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18
Q

What is Aortic Stenosis?

A

Stenosis=”Narrowing”
Aortic “of the Aorta”/LV outlet valve
Aortic Stenosis “ Narrowing of the aorta”
Due to a Streptococcus viral infection which leads to Rheumatic fever
-can be readily fixed with antibiotics
Decreased integrity of valve + Narrowing of the Outlet valve
Strep infection = 1. causes the body to produce antibodies which attack your own body tissue (endo, myo, and peri cardium) and ESPECIALLLY the CT connective tissue COLLAGEN- which is what the Valve leaflets are made up of
=This decreases the structural stability of the valve leaflets -leaflet tissue is rebuilt with scar tissue, vegetation and lumps= Decreased Integrity of the pockets
2. Narrowing of the outlet valve
=Narrowed outlet= restricts blood flow
=LV has to Work harder to push blood out (greater Afterload to work against)
= Working harder = LV becomes more muscular (hypertrophy)
1. stiffer = heart struggles to inflate, as the stiffness means the heart doesn’t pump as well.
2. stiffer = Loses flexibility/compliance
3. Lumen = lumen smaller, due to the increased wall thickness
4. CO= Cardiac Output will Decrease =increased Afterload(pressure ventricle has to work against)= therefore LV must generate More pressure
Overall: Decreased ability to fill = due to smaller lumen and increased stiffness

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19
Q

What causes Rheumatic fever?

A

streptococcus viral infection

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20
Q

What can streptococcus infection/Rheumatic fever lead to?

A

Aortic Stenosis

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21
Q

What causes Aortic Stenosis?

A

Streptococcus infection –> which causes Rheumatic Fever

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22
Q

What are the two essential things that is caused by aortic stenosis due to a Streptococcus infection causing rheumatic Fever?

A
  1. decreased integrity of the valve flaps

2. narrowing of the outlet valve opening

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23
Q

How does the integrity of the valve decrease due to strep infection which causes Aortic Stenosis?

A

causes the body to Produce Antibodies
These antibodies Attack your Own Tissue (end, myo and peri cardium) but Especially CT connective tissue called Collagen which is what the Valve Leaflets are made out of
-this leads to decreased integrity of valve flaps

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24
Q

What do the antibodies produced by the body upon a strep infection during rheumatic fever attack particularly?

A

collage CT connective tissue
This is what the Valve Leaflets are made out of
-hence the leaflet integrity decreases

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25
Q

What are the features of the aorta outlet valve narrowing during aortic stenosis?

A
  1. Narrowing of the outlet valve
    =narrowed outlet = restricts the blood flow = LV has to work harder in order to push the blood out as there is an Increased Afterload which they have to work against
    = working harder = LV becomes more muscular (hypertrophy)
    INCREASED STIFFNESS due to INCREASE AFTERLOAD
    OVERALL: decreased ability to Fill - due to Increase Stiffness and decreased size of Lumen
  2. stiffer = heart struggles to INFLATE , as the STIFFNESS means the heart cannot pump as well
  3. Stiffer= Decreased Compliance
  4. Lumen = smaller, due to increased thickness of the LV wall
  5. CO= cardiac output Decreased due to Increased Afterload/greater pressure to work against = meaning the LV has to generate More pressure and therefore grows more muscular
    Overall: Decreased ability to fill = due to smaller lumen and increased stiffness
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26
Q

What 4x main things occur due to Aortic Stenosis?

A

Overall: decreased ability to FILL = due to Increased Stiffness (increased afterload) and Decreased Lumen

  1. Stiffer = Heart struggles to INFLATE = as more Rigid due to the STIFFNESS of thicker walls as the heart cannot pump as well
  2. Stiffer = decreased compliance
  3. Lumen = smaller, due to increased thickness of the LV wall
  4. CO= cardiac Out put DECREASED due to an increase AFTERLOAD which means the heart has to generate more force in order to pump blood out
    - therefore grows more muscular, to generate more pressure to pump the blood out = Hypertrophy
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27
Q

What are the 5x components of the Pericardium?

A
  1. Visceral Pericardium (viscera = organ)
  2. Pericardial space
  3. Serous fluid
  4. Parietal Pericardium (parietal = peripheral component)
  5. Fibrous Pericardium
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28
Q

What is the Pericardium?

A

Pericardium is a Continuous Double layer of parietal and visceral pericardium which Surrounds and Protects the heart
Single layer
Squamous (flattened) Mesothelial cells
Thin
These Mesothelial cells secrete Serous fluid
Function: Reduces Friction. Results in the Pericardium Sliding Effortlessly, Avoiding friction of the dynamic organs (e.g. with lungs as well) which can lead to organs rubbing raw and causing infections
Heart isn’t Inside the pericardium is tis Surrounded from it (hand pushing into the pericardium)

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29
Q

What is the function of the Pericardium?

A

to Surround and Protect the heart

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30
Q

Is the Pericardium separated or continuous?

A

Continuous

-the visceral and parietal pericardium are parallel to one another/fold over each other

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31
Q

What type of cells is the Pericardium composed of?

A

Mesothelial cells
Single layer
Squamous (flattened) Mesothelial cells -Thin

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32
Q

What type of Mesothelial cells is the pericardium made of?

A

Squamous (flattened) Mesothelial cells

-a single layer -thin

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33
Q

Where does serous fluid for the pericardium originate from?

A

the Mesothelial cells

Secreted by the thin single layer of flattened Mesothelial cells

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34
Q

What is the function of the thin single layer of squamous (flattened) Mesothelial cells which compose the continuous pericardium?

A

to secrete Serous fluid for the pericardial space

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35
Q

What is the function of the pericardium?

A

Function:
Reduce Friction
results in the pericardium Sliding Effortless against itself as a continuous layer with the lubricating serous fluid secreted by the Mesothelial cells within the pericardial space
Avoid the tissue Rubbing raw (due to friction of dynamic organs -such as heart and lungs) which can lead to infections

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36
Q

What is the function of the Visceral Pericardium?

A

viscera = organ
Visceral pericardium is the Inner walls of the pericardium (closest to the organ)
Adheres to the heart (organ)
forms the hearts Outer Surface (epicardium)

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37
Q

What does the visceral pericardium adhere to?

A

Heart’s Epicardium

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38
Q

What is the function of the Pericardial space?

A

capillary thin
Contains only Serous fluid
Serous fluid is secreted by the Mesothelial cells
thin film - grossly exaggerated in diagrams
Reduces the friction of the dynamic organs
Acts as a Lubricant to prevent the heart from rubbing against the Thoracic cavity with friction as the heart dynamically beats

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39
Q

How thin is the Pericardial space?

A

capillary thin

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40
Q

What is in the pericardial space?

A

ONLYYYYY Serous Fluid - no organs or tissue

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41
Q

What friction is the heart trying to avoid by having the pericardium?

A

Friction with the Thoracic cavity

-due to both the heart and the lungs (thoracic) being Dynamic (moving/pumping) muscles

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42
Q

What is the function of the Parietal Pericardium?

A

Outer wall of the pericardium

Is the inner lining of the Fibrous Pericardium which is on its outside

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43
Q

What is the function of the Fibrous Pericardium?

A

Is on the outside of the Parietal pericardium (partial pericardium lines it)
Touch
Fibrous sac
Dense Irregular Tissue: Made out of fibres and Collagen
Function to Resist Tension -protective
Doesn’t stretch
-Note: not normally seen in rats

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44
Q

What is the fibrous Pericardium made out of?

A

Dense Irregular CT

-fibres and collagen

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45
Q

Why is the fibrous pericardium made out of dense irregular connective tissue (a lot of fibres and collagen) and on the outside?

A

Resist Tension

Doesn’t Stretch

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46
Q

What part of the pericardium isn’t located in rats but is located in humans?

A

Fibrous Pericardium

-thin and glandular instead

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47
Q

What is the condition when there is too much Serous fluid in the Pericardial space?

A

Pericarditis
-Can get an infection in here
- effects the filling of the heart
-as the heat is more compressed
-compression of the heart is due to the External pressure of the increased fluid
Increase fluid = affects ability to fill = Compression of heart>expanding bag

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48
Q

What is the condition of Pericarditis?

A

Increase serous fluid in the pericardial space
Can lead to infections in there
Affects the heart’s ability to fill
Increase compression of the heart
-compression of the heart is due to External pressure generated by the increased serous fluid
Increased fluid =affects ability of the heart to fill
Compression of the heart>expanding bag

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49
Q

Does he condition of Pericarditis affect the heart ability o relax, contract, empty or fill?

A

Pericarditis (increased serous fluid in pericardial space) affect hearts Ability to Fill

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50
Q

What does increased serous fluid result in?

A

Increased External pressure
Increased compression of the heart
Ability of the heart to fill

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51
Q

When there is increased fluid in the pericardial space, does it affect the compression of the heart or the expansion of the bag more?

A

Increase compression of the heart more
Increased compression of heart>expansion of the pericardial bag
Results in More external Pressure onto heart affects heart’s ability to fill

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52
Q

What are the 3x layers of the heart wall?

A

Inner –> outer

  1. Endo cardium
  2. Myo cardium
  3. Epi cardium
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53
Q

What is the epicardium?

A

Outer layer of the heart wall

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54
Q

What is the visceral pericardium?

A

Inner most layer of the pericardium

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55
Q

Which term in the layers of the heart has multiple names?

A

Visceral pericardium/Epicardium
Pericardium = Visceral pericardium = Inner most layer
Heart wall = Epicardium = Outer most layer of the heart wall

56
Q

Which two layers of the heart are continuous with each other?

A

Visceral and Parietal pericardium

Endocardium and Blood vessel Endothelium

57
Q

If a knife pierced a person from the side what would be the last thing that they hit before blood?

A

Endocardium

-write it out! :)

58
Q

What is the Endo cardium continuous with?

A

Endothelium of blood vessels

59
Q

What are the 8x layers of the heart, starting from the outer most part of the heart?

A
  1. Outside the heart
  2. fibrous Pericardium
  3. Parietal Pericardium
  4. Pericardial space -containing ONLY serous fluid
  5. Visceral pericardium/Epicardium
  6. Myocardium
  7. Endocardium - continuous with blood vessel endothelium
  8. blood vessel
60
Q

Is the blood vessel endothelium continuous with anything?

A

Yes

Blood vessel endothelium is continuous with Endothelium

61
Q

What are the key features of the fibrous Skeleton of the heart?

A

composed of dense connective tissue rings of course fibres
- openings of the heart in line and in contact, allows the (atria and vessels) and Ventricles to be separated by the structural lines of the fibrous skeleton
4x Functions:
1. Strengthening holes/valves
2. it’s Fibres Anchor the Valve leaflets to the side of the heart
3. Electrical Insulator (between the atria and ventricles)
4. prevents Overstretching of the valves
LEFT pump of heart= high pressure = Full rings
RIGHT pump of the heart = low pressure = partial no rings

62
Q

What is the Fibrous Skeleton composed of?

A

Dense CT rings

Course Fibres

63
Q

What is the 4x functions of the fibrous skeleton?

A
  1. Strengthening of the Holes/valves
  2. fibres Anchor the valve leaflets to the side of the heart
  3. Electrical Insulator (between the atria and ventricles)
  4. prevents Overstretching of the valves
64
Q

Are the openings of the heart in line with one another and what does this mean in relation to the fibrous skeleton?

A

Yes the openings of the heart are inline
also Incontact with one another
Positive: as this allows the (atria and vessels) and the Ventricles to be separated by the structural lines of the fibrous skeleton

65
Q

What is the relationship between the completeness of the fibrous skeleton?

A

LEFT pump= higher pressure = complete rings

RIGHT pump= lower pressure = partial/absent rings

66
Q

What sort of fibrous rings does the LEFT PUMP of the heart have?

A

Left Pump = High pressure = Complete rings

  • needs more structural support
  • needs to avoid over stretching more due to increased pressure
  • more insulation
67
Q

What sort of fibrous rings does the RIGHT PUMP of the heart have?

A

Right Pump = Low pressure = Incomplete/Absent rings
Tricuspid =partial
Pulmonary = absent

68
Q

What support and insulation and anchoring does the Mitral/Bicuspid valve have?

A

Complete ring
Left pump = under High Pressure
-prevents overstretching and strength and insulation control

69
Q

What support and insulation and anchoring does the Aortic valve have?

A

Complete ring
Left Pump = under High Pressure
-prevents overstretching and strength and insulation control

70
Q

What support and insulation and anchoring does the Tricuspid valve have?

A

Partial ring
Right Pump = under relatively Lower Pressure (2nd lowest out of all holes of heart)
Inlet = bigger hole the right Outlet/pulmonary valve
-Fatty connective tissue and Loose fibres (less densely packed than other CT connective tissue) are still present in areas where the fibrous skeleton in incomplete

71
Q

Is there anything present where there is an incomplete fibrous skeleton?

A

Yes
2x things
1. Fatty Connective tissue
2. Loose fibres (less densely packed than other CT connective tissue) -is still present in areas where the fibrous Skelton is incomplete

72
Q

What support and insulation and anchoring does the Pulmonary Valve have?

A

None
Requires the least support and insulation and anchoring out of all the holes (smallest pressure)
-Fatty connective tissue and Loose fibres (less densely packed than other CT connective tissue) -is still present in areas where the fibrous skeleton is incomplete

73
Q

What are the 2xtypes of cardiac muscle?

A
  1. Myocytes (branched, highly contractile and Can conduct AP)
  2. Purkinje cells (non-branched, thicker and wider, good wiring to the heart and Conducts AP Better)
74
Q

What are the 3x features of Myocyte?

A
  1. Branched
  2. Highly contractile
  3. Can conduct AP
75
Q

What are the 5x features of Purkinje fibres?

A
  1. Specialised Cardiac muscle
  2. Non-branched
  3. Thicker and wider
  4. good wiring to the heart
  5. Conducts AP better
    “Terminal wires of the heart”
76
Q

Where outside of the heart are Purkinje fibres located?

A

Cerebellum

77
Q

What specialised type of cell is located in both the heart and the cerebellum?

A

Purkinje fibres

78
Q

What is the conduction system?

A

the conduction system is the method by which heart Beats are Initiated, and the heart is stimulated
1.Initiation of beats
2. Stimulation of the heart
Function: Network of specialised cardiac muscle fibres, the provide paths for each cycle of cardiac excitation to pass through the heart

79
Q

What is the heart’s pace maker?

A

SA node

80
Q

What is the function of the hearts Pacemaker/SA node?

A

Setting the rhythm of electrical excitation/contraction

-autorhythmic fibres which compose the SA node depolarise and repolarise by themselves as a group

81
Q

Where is the SA Node located?

A

Superior Vena Cava junction to the Right Atria

82
Q

What is located at the junction of the Superior Vena cava and Right Atrium?

A

SA Node

83
Q

What is the function of the Cardiac Conduction system?

A

A network of Specialised cardiac muscle fibres, that proved a pathway for each cycle of cardiac excitation to pass through the heart

84
Q

What are the 9x components of the conduction system?

A
  1. Myocytes
  2. Purkinje fibres (atrium and ventricles)
  3. SA node
  4. Fibrous Skeleton
  5. AV node
  6. Atrio-Ventricular Bundle of His
  7. Right and Left Bundle Branches
  8. Interventricular septum
  9. Purkinje Fibres
85
Q

Where is the heart are purkinje fibres located?

A

in BOTH the ATRIA and the VENTRICLE

86
Q

What are the main 6x features of the SA node?

A

Sino-Atrial Node

  1. Tangled knot/cluster of specialised muscle cells
  2. Sets baseline rhythm - initiates the wave of depolarisation through the heart
  3. Repolarisation period = 60-100 AP per min
  4. SA node’s automatic firing can be influenced. Influenced by NE, Vagal nerve activity, ACh
  5. The cells of the SA node are always depolarising and repolarising by themselves as a group
  6. Located at the junction between the Superior Vena Cava and the Right Atria
  7. Has an INTRINSIC ability to generate activity
87
Q

What sets the baseline rhythm of the heart?

A

SA node

  • the autorhythmic self excitable and repolarising tangled knot of specialised cells
  • its intrinsic ability to generate activity
88
Q

What is the repolarisation period of the SA node?

A

60-100 AP per min

89
Q

Can the SA node be influenced?

A

Yes, its rate of its intrinsic ability to generate activity can be affected by:
by NE, and Vagus nerve and ACh

90
Q

What 3x things can influence the SA node’s autorhythmicity and repolarisation period?

A
  1. NE
  2. Vagal nerve
  3. ACh
91
Q

Does the Heart contain any nerves?

A

No
I has nerves going TO the heart
but NO nerves going THROUGH it
-instead it has highly conductile Purkinje Fibres

92
Q

What does the heart have to compensate for the fact that it doesn’t have any nerves through/within it?

A

it has Highly conductile Purkinje Fibres

93
Q

Are the cells of the SA node strong or weakly contractile?

A

Weakly contractile
-unlike nerve fibres
Has an intrinsic ability to generate activity
as it is only needed for its autorhythmicity and automatic repolarisation and polarisation

94
Q

What is another name for Purkinje fibres?

A

Terminal wires of the heart

95
Q

What are the main features of the AV node?

A
  1. Lower than the SV node
  2. Located in the atrial septum and ventricular junction, as the only hollowed part of the fibrous skeleton
  3. Slower repolarisation
  4. the only electrical connection between the atria and ventricle
  5. Similar cells to SA - therefore can take over its job, just not as well
96
Q

What is the only electrical connection between the atria and ventricle?

A

AV node

97
Q

What is a special function of the AV node?

A

It is the only electrical connection between the atria and the ventricle

98
Q

why must the heart have co-ordinated contraction (especially of its ventricles)?

A

to keep Pumping efficiency High

99
Q

What is the first pathway, AP speed and Result in the propagation of the Cardiac APs?

A

Pathway: SA node/Atrial muscle
AP speed: Slow (0.5ms-1)
Result: atrial contraction (uniformly)

100
Q

What is the second pathway, AP speed and Result in the propagation of the Cardiac APs?

A

Pathway: AV node
AP speed: Very Slow (0.05ms-1)
Result: 100ms-1 delay - between the Atria contracting and ventricle starting to contract. Allowing time for the atria to fill blood into the ventricle (20% top up)- atria is too thin walled and weak itself so needs the change in cell structure to cause delay for it instead Small diameter

101
Q

What is the 100ms-1 delay between?

A

Atria contraction and the ventricles starting to contract

-allows the atria to have time to fill the ventricle with the last 20% of blood (time to op up the ventricle)

102
Q

How long is the delay between the atria contraction and the ventricles starting to contract?

A

100ms-1

  • allows the atria to top up the 20% fill into the ventricles, giving time between the atria contracting and the ventricles starting to contract
  • as the atrial walls are too thin and weak themselves to compete with the ventricle -therefore need change in cell structure to cause this delay for them instead
103
Q

What is the third pathway, AP speed and Result in the propagation of the Cardiac APs?

A

Pathway: AV bundle/Purkinje Fibres
AP speed: fast (5ms-1)
Result: Even/Rapid Ventricular contraction (systole)

104
Q

What initiates the wave of depolarisation through the heart?

A

SA node

105
Q

What 5x things occur during the 1st step out of 5 in the propagation of the cardiac action potential/cardiac conduction system?

A

Cardiac Excitation begins at the SA Node - SLOW
1- Cardiac Excitation begins at the SA Node (Sino atrial node) - AP Action Potential is fired
2-SA node has an Intrinsic ability to generate activity. The SA node is a knot of specialised cardiac muscle fibres which as an unstable resting potential and sets a baseline rhythm. It depolarises to threshold spontaneously reaching via “pacemaker potential”
3- Each AP from the SA node propagates through BOTH atria via GAP junctions in the Intercalated discs of the atrial muscle fibres (Myocytes) and the Atria’s Purkinje fibres
4-The wave of excitation doesn’t leave the atria due to the fibrous skeleton insulator
5-following the AP, the 2x Atria contract at the same time

106
Q

What 2x mediums does the AP pass through in the atria during propagation of its action potential?

A
  1. through Gap junctions in the Intercalated discs of its Myocytes
  2. through the atria’s purkinje fibres
107
Q

Does the wave of excitation leave the fibrous skeleton?

A

No

The wave of excitation doesn’t leave the atria due to the Fibrous Skeleton insulator

108
Q

What happens when the AP action potential goes through the atria?

A

The atrias BOTH contract at the same time

109
Q

What occurs during the 2nd step out of 5 in the propagation of the cardiac action potential/cardiac conduction system?

A

Action potential reaches the AV Node - Very slow
1. AP reaches the AV Atrio ventricular Node
2. AV node is a Cluster of fibres which is located in the Interatrial septum, which forms a hole through the fibrous skeleton
3. Therefore Most of the AP Stops, only with the remainder of it going through the Hole
4. AP slows considerably due to the Difference in CELL STRUCTURE (from the SA node –> Myocytes/purkinje fibres –> AV node)
This results in a 100ms delay between the Atria contracting and the ventricles starting to contract, allowing time for the atria to fill the ventricle with the last bit of blood- TOP UP the ventricle with extra 20%
Delay is needed as the thin WALLS of the ATRIA are WEAKER than ventricular walls, and otherwise cant compete, so needed the cell structure change to initiate this delay so top up can occur

110
Q

Where is the AV node located?

A

In the interATRIAL septum ,
In a HOLE of the fibrous skeleton
between the atria and ventricles

111
Q

What is the purpose of the 100ms-1 delay caused by the change in cell structure as the AP passes from the atria into the AV node?

A

Delay between the Atria contracting
and the Ventricles starting to contract
-providing time for the atria to top up the ventricle 20% empty blood into the ventricles
-as the Atrial walls are too weak to do this alone, cant compete with ventricular walls

112
Q

When does the atrial 20% blood volume top up occur?

A

as the AP reaches the AV node
very slow
100ms-1 delay

113
Q

What occurs during the 3rd step out of 5 in the propagation of the cardiac action potential/cardiac conduction system?

A

From AV node the AP reaches the Bundle of HIS (FAST)

  • electrical impulses pass through the AV atrio-venricular Bundle of His as it provides/acts as an Electrical link between the atria and ventricles
  • It is the only place where the AP can propagate through without being electrically insulated by the fibrous skeleton
114
Q

What acts as an electrical link between the Atria and Ventricles?

A

AtrioVentricular Bundle of His
-it acts as an electrical link between the atria and ventricles, as it is the only place where an AP can propagate through without being insulated by the fibrous skeleton

115
Q

What is the function of the AtrioVentricular bundle of His?

A

It acts as an Electrical Link b/a atria and ventricles

-is the only place where the AP can propagate without being insulated by the fibrous skeleton

116
Q

What occurs during the 4th step out of 5 in the propagation of the cardiac action potential/cardiac conduction system?

A

AP enters both the Right and Left bundle branches FAST

  • AP enters BOTH the Right and Left bundle branches
  • AP extends through the Interventricular Septum
  • goes towards the Apex of the heart
117
Q

Where is the AP propagating as it conducts down the Right and Left branches of His?

A

down the Interventricular septum
-goes towards the Apex of the heart
FAST - via right and left branches of his

118
Q

What occurs during the 5th step out of 5 in the propagation of the cardiac action potential/cardiac conduction system?

A

AP conducts through the Purkinje fibres (FAST)
-AP conducts through the purkinje fibres
- the Large diameter of the Purkinje fibres Rapidly conducts the AP from the Apex of the heart –> Upwards to the Remainder of the Ventricles
-Results in the Ventricles EVENLY conducting, squeezing BOTH sides of the ventricles SIMULTANEOUSLY, in phase with each other
=Uniform ejection pushing blood out
-This is SYSTOLE
-Pushes bloods towards the semilunar valves
- all happens at once due to the wiring of the heart

119
Q

Where does the cardiac AP conduct as it goes through the Purkinje Fibres?

A
  • Large diameter of the Purkinje fibres allows Rapid conduction of the AP
    -AP goes from Apex –> Upwards to the remainder of the Ventricles
    FAST-via wide diametered and extremely conductile purkinje fibres
120
Q

What is the whole point of the cardiac action potential/cardiac conduction system?

A

to allows for the Ventricles to Contract SIMULATENOUSLY - in phase with one another
UNIFORM EJECTION pushing blood out together
for SYSTOLE to occur
-all happens at once due to the wiring of the heart
-not in phase =uneven ventricular contraction = out of phase = bulges = decreased efficiency of the heart = non-optimum systole

121
Q

What is optimum Systole?

A

When the Ventricles contract SIMULATENOUSLY as there is UNIFORM EJECTION (systole) pushing blood out at the same time- The ventricles being IN PHASE

  • all happens at once due to the wiring of the heart
  • not in phase = uneven ventricular contraction = not in phase = bulges = decreased efficiency of the heart = non-optimum systole
122
Q

What does Non-optimum systole involve?

A 
Ventricular contraction/conduction of AP is NOT in phase
There is NON uniform ejection of blood
BULGES occur
Decreased EFFICIENCY of the heart
NON-optimum SYSTOLE
123
Q

What are the 2x options for a diseased/damaged SA node?

A

SA node conduction blockage
SA node initiates AP around 90-100 per min
1. AV node is able to pick up the task of being the Pacemaker
Different intrinsic rate of AV node 40-60 AP per min
2. Pacemaker can be installed

124
Q

What is the intrinsic rate of AP firing per min from the AV node?

A

slower than the 90-100 AP per min of SA node

is slower at about 40-60 AP perm min of SA node

125
Q

When would a Pacemaker be installed?

A

When the SA node is diseased and damage

When there is a SA node conduction blockage

126
Q

What does the condition of Cardiac Tamponade consist of?

A

Occurs due to a Cardiac infarction (heart attack)-due to part of your heart muscle tissue dying
Decreased integrity of replaced tissue - even though the Macrophages clean up the dead tissue the puss and fluid which is caused to enter due to the infection, The dead tissue over time is replaced with Scar tissue which is thin and weak
Under the High pressure of the LV left Ventricle the blood moves through these weakened areas, as the LV ruptures and the blood move INTO the Pericardial space
Every time the ventricle contracts MORE BLOOD takes the path of LEAST RSISTANCE into the pericardial space
As the fibrous pericardium is quite rigid, instead of the pericardial sac Expanding, the bag compresses the heart. Compression occurs due to the Higher volume of blood which is Stretching/forcing the pericardium to force inwards
Overall AFFECTING the ability of the heart to FILL
-overall the heart be squeezed smaller and smaller due to the accumulation of blood in the pericardial space
- decreased CO leads to DIFFICLTY BREATHING
5x main outcomes of Cardiac Tamponade
1. compression inwards onto the heart (more than expansion outwards of space due to fibrous pericardium)
2.ventricular filling decreases
3. CO is decreased
4. decreased venous return to the heart
5. blood pressure falls
6. Difficulty breathing

127
Q

What does Cardiac Tamponade occur due to?

A

due to Heart attack/myocardial infarction
Due to part of your heart muscle tissue dying
- and there being weaker scar tissue which ruptures under the high pressure of the ventricle and causes the blood to flow through the PATH OF LEAST RESISTANCE and into the pericardial space COMPRESSING the heart and DECREASED CARDIAC OUTPUT
symptom = DIFFICULTY BREATHING

128
Q

How does a myocardial infarction/heart attack cause Cardiac Tamponade?

A

Heart attack/myocardial infarction causes cardiac Tamponade due to part of the heart muscle tissue dying

129
Q

What are the properties of scar tissue?

A

thin and weak
-often containing lumps and vegetation
results in decreased integrity of the now dead muscle tissue

130
Q

If a Myocardial Infarction occurs what is the path of least resistance?

A

Through the weaker scar tissues wall of the ventricle
Ruptures this weaker wall and becomes the PATH OF LEAST RESISTANCE
the blood goes INTO THE PERICARDIAL SPACE

131
Q

What is the condition called when there is an accumulation of blood in the pericardial space?

A

Cardiac Tamponade
-is basically like a period which you need a tampon for
-the path of least resistance is just out the vajayjay
Impacts CO Cardiac Output
Resulting in Difficulty Breathing

132
Q

What is the major symptom of Cardiac Tamponade?

A

Difficulty breathing

133
Q

What is the state of difficulty breathing a major symptom of for which disease?

A

Cardiac Tamponade

  • heart attack
  • due to scar tissue weaker forming which is thinner and weaker
  • blood ruptures this weaker tissue in LV wall as is the path of Least Resistance
  • Blood squirts into the pericardial space
  • fibrous pericardium on outside and tough causes compression inwards> expansion of the bag outwards
  • compression on heart
  • affecting heart’s ability to fill
  • Decreases CO
  • leads to Difficulty breathing
134
Q

What is the role of the Fibrous Pericardium in Cardiac Tamponade?

A

Outer shell off the pericardium
More rigid
And therefore when the LV is ruptured and blood is taking path of least resistance into the pericardial space every contraction, more blood fills the pericardial space (increasing pericardial volume)
Rigidity calls for more Compression inwards onto the heart> than expansion outwards
Affects heart’s ability to fill
Decrease in Cardiac Output CO (+ venous return to heart falls and blood pressure falls)
-Leads to DIFFICULTY IN BREATHING

135
Q

What are the 6x main outcomes of cardiac Tamponade?

A
  1. compression inwards onto the heart (more than expansion of the increased volume of pericardial sac outwards, due to rigidity of outer fibrous pericardium)
  2. Ventricular filling is decreased (hearts ability to fill decreases due to this compression)
  3. CO cardiac output Decreased
  4. Venous return to the heart diminishes
  5. Blood pressure falls
  6. DIFFIULTY BREATHING

Medsci 142 Test 1 (20 decks)

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