Heart Flashcards
1
Q
cardiovascular system
components
A
heart
arteries
veins/lymphatics
capillaries
2
Q
heart
A
acts as a pump for the blood
3
Q
arteries
A
supply blood to the heart
4
Q
veins/lymphatics
A
drains deoxygenated blood from heart to lungs
5
Q
capillaries
A
where gas exchange occurs
6
Q
components of the cardiovascular system are made up of vascular tissue which is made of
A
connective tissue
cells - consists of epithelia and muscle
7
Q
blood vascular system
A
a closed supply and drainage system - a continuous loop
8
Q
lymphatic (vascular) system
A
an open-entry drainage system - a one-way system
9
Q
left pump sends
A
blood away from the heart
10
Q
right pump sends
A
blood back towards the heart and lungs
11
Q
organisation of the cardiovascular system
supply side
A
arteries are the only supply path
major arteries are situated to avoid damage e.g. deep in the trunk
important structures often receive supply from two sources (two separate arteries)
arteries change their name at each major branch
12
Q
organisation of the cardiovascular system
exchange network
A
capillaries of varying degrees of permeability
continuous (controlled - tight)
fenestrated (leaky)
sinusoidal (very leaky)
13
Q
organisation of the cardiovascular system
drainage
A
3 pathways for drainage - deep veins, superficial veins, lymphatics
cross sectional area of veins is at least twice that of arteries (to shift the same volume of blood/seconds)
14
Q
heart structure
A
blunt, cone shaped, size approximately that of a closed fist
heart is rotated posteriorly and tilted so the apex is pointed anteriorly
15
Q
Apex
A
pointed end (bottom) sits against 5th/6th ribs - PMI (point of maximal impulse) = apex beat
16
Q
Base
A
broad end (top) sits between 2nd and 3rd ribs
17
Q
4 chambers of the heart
A
right atrium
right ventricle
left atrium
left ventricle
18
Q
right atrium
A
receiving chamber
deoxygenated blood from body to right ventricle
19
Q
right ventricle
A
pumping chamber
deoxygenated blood from heart to lungs
20
Q
left atrium
A
receiving chamber
oxygenated blood from lungs to left ventricle
21
Q
left ventricle
A
pumping chamber
oxygenated blood to body
22
Q
atrial chambers
A
thin walled receiving chambers
right atrium receives deoxygenated blood from
left atrium receives oxygenated blood
23
Q
right atrium receives deoxygenated blood from
A
superior vena cava
inferior vena cava
coronary sinus
24
Q
left atrium receives oxygenated blood
A
four pulmonary veins
25
layers of the heart wall
endocardium
myocardium
epicardium
pericardium
26
endocardium
```
tissue in the heart
simple squamous epithelium (endothelium)
loose irregular fibrous connective (FCT)
(small) blood vessels
Purkinje fibres
```
27
myocardium
heart muscle
myocardial thickness - right side = 0.5cm, left side = 1.5cm
left side thicker as it pumps oxygenated blood with high pressure and velocity, thus requiring more muscle tissue
28
epicardium
tissue of the outer of the heart
visceral pericardium - adheres to the epicardium
(large) blood vessels
loose irregular FCT, adipose
29
pericardium
```
sac heart is in
serous pericardium
parietal pericardium
pericardial fluid
visceral serous pericardium
```
30
serous pericardium
layer that forms a closed cavity around the heart
31
serous pericardium
layer that forms a closed cavity around the heart
32
parietal pericardium
outer layer of seroud pericardium
33
pericardial fluid
fills the cavity
34
visceral serous pericardium
inner layer of cavity that borders the heart
35
pericardial layers
fibrous pericardium (top layer of pericardium)
parietal layer of serous pericardium
pericardial cavity
visceral serous pericardium
36
Atrioventricular (AV) valves
| function
prevent blood returning to atria during ventricular contraction
37
AV valves
| right side
tricuspid valve
38
AV valves
| left side
bicuspid (mitral) valve
39
semilunar valves
| function
prevent blood returning to ventricles during filling (diastole)
40
semilunar valves
| right side
pulmonary (semilunar) valve
| 3 cusps
41
semilunar valves
| left side
aortic (semilunar) valve
| 3 cusps
42
semilunar valves
| operation
pushed open as blood flows out of heart
| close as blood starts to backflow
43
diastole
when heart is not contracting
AV valves open
semilunar valves closed
rising pressure
44
systole
when heart is contracting
AV valves closed
semilunar valves open
falling pressure
45
chordae
attaches AT valve leaflet to papillary muscles to stop it from prolapsing into the atrial chamber
papillary muscle contracts to put tension into the chordae tendineae to shut the valve in a slow controlled manner rather than shutting fast under the high pressure of the moving blood
46
myocardium
| extended structure
```
striated
short, branched cells
one (or sometimes 2) nuclei per cell
central (oval shaped) nucleus
cytoplasmic organelles packed at the poles of nucleus
interconnected with neighbouring cells via intercalated disks (ICD's)
mitochondria = 20% of volume of cell
irregular branched sarcomeres
```
47
intercalated disks
3 intracellular junctions
48
3 intracellular junctions of intercalated disks
adhesion belts
desmosomes
gap junction
49
adhesion belts
link actin to actin
| vertical position
50
desmosomes
link cytokeratin with cytokeratin
51
gap junction
electrochemical communication
| horizontal portion
52
conduction system of the heart
it's actions greatly increase the efficiency of heart pumping
this system is responsible for the coordination of heart contraction and of atrioventricular valve action
autonomic nerves alter the rate of conduction impulse generation
53
conduction cells (TS)
(some) peripheral myofibrils
central nucleus, mitochondria, glycogen, lots of gap junctions, some desmosomes and few adhesion belts
1% cardiac cells
54
great saphenous vein
longest vein in the body
55
3 layers of the walls of blood vessels
```
tunica intima (inner)
tunica media (middle)
tunica adventitia (externa - outer)
```
56
tunica intima
| structure
- endothelium
a simple squamous epithelium which lines the lumen of all vessels
- subendothelium
a sparse pad of loose FCT cushioning the endothelium
- Internal Elastic Lamina (IEL)
a condensed sheet of elastic tissue
the IEL is well developed in arteries and less developed in veins
57
tunica media
| structure
- smooth muscle
- a variable content of connective tissue fibres, mainly elastin and collagen
- thickness of the media is proportional to both vessel diameter and blood pressure
- thickest layer in arteries because this layer is made of muscle which is needed to pump the blood around the body under a certain amount of pressure
58
```
tunica adventitia (externa)
structure
```
- loose FCT with a high content of collagen and variable amount of elastin
- in larger vessels, the adventitia contains vasa vasorum (the little extra ones)
- lymphatics and autonomic nerves are also found in this region
59
elastic artery
tunica media is dominated by elastin and elastic content
60
muscular artery
tunica media is dominated by smooth muscle
61
arterioles
| function
the resistance vessels of the circulation thus determines blood pressure
62
capillaries
| function
site of exchange between blood and tissues
63
venules
start of the collecting (drainage) system
64
veins
| functions
low pressure, large volume transport system
one-way (unidirectional) flow
capacitance vessels
65
veins
| structure
irregular, flattened shape with large lumen and thin wall
| have spare capacity (can take up extra blood volume) - capacitance vessels
66
veins
| 3 layers
intima
media - much thinner than arteries, a few layers of smooth muscle (often in two distinct layers) as doesn't need to pump blood under pressure
adventitia - often the thickest layer of a vein
67
valves in veins
prevent blood from back flowing when skeletal muscle pumps blood
as skeletal muscle pushes blood it travels in both directions but the valves shut to keep the blood flowing forward
68
capillaries
| function
site exchange between blood and tissues
69
capillary function demands
very thin walls
large total cross sectional area of capillary bed
slow and smooth blood flow
large total area of the capillary bed (compared to arterioles) means much slower blood flow
70
capillaries
| 3 structures
continuous capillaries
fenestrated capillaries
sinusoidal capillaries
71
continuous capillaries
the most widespread
8-10µm diameter
e.g. skeletal and cardiac muscle
72
fenestrated capillaries
leaky
8-10µm diameter
e.g. glomerulus in the kidney and small intestine
73
sinusoidal capillaries
very leaky
30-40µm diameter
e.g. liver sinusoids
74
lymphatic system
| structure - lymphatic vessels
- commence as large, blind ending capillaries
- from small intestine, a special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli
- larger (thin wall) collecting vessels have numerous valves to prevent backflow
75
mammalian cardiovascular system
four chambered heart
blood flows in one direction - unidirectional
arterial blood flows away from the heart
venous blood flows towards the heart
76
the heart is two pumps that lie 'in series'
| meaning...
there is equal flow through the two circuits
77
heart cycle
relaxation (heart full of blood to be pumped = lots pressure) --> atria contract --> ventricles contracts --> relaxation
right and left pumps contract simultaneously
atria contract first and ventricles contract second
valves open and close to direct blood
78
AV valves control flow between..
the atria and ventricles
79
Aortic and pulmonary valves control flow
| from...
the ventricles out to the circulatory vessels
80
cellular mechanism of cardiac contraction
sarcomeres
Ca2+ levels go up and more Ca2+ is released from the sarcoplasmic reticulum (SR) --> myosin binds to actin to form cross-bridge --> myosin pulls on actin to shorten the sarcomere and generate force --> every myocyte activated during each heartbeat
81
To increase force of cardiac contraction 3 physiological differences occur
every cardiomyocyte is activated during each heartbeat
extent of cross-bridges formed not maximised at rest
- increased cytosolic Ca2+ level
- increased number of cross-bridges formed
- increased force of contraction
82
cellular mechanism of cardiac relaxation
| 4 details
- decrease in cytosolic Ca2+ levels, Ca2+ pumped back into the SR
- cross-bridges release when ATP binds to myosin
- reduction in force means the heart can relax
- all cardiac myocytes relax each beat
83
starting at atrial systole, 1st step of the cardiac cycle
AV valves are open to let the blood through from the atria into the ventricles
84
step 2 of the cardiac cycle
at isovolumetric ventricular contraction:
aortic and pulmonary valves are still closed
ventricles begin to contract
massive and rapid increase of pressure
85
step 3 of the cardiac cycle
ventricular ejection:
| aortic and pulmonary valves open allowing the highly pressurised blood out through the aortic and pulmonary arteries
86
step 4 of the cardiac cycle
isovolumetric relaxation:
| heart relaxes
87
step 5 of the cardiac cycle
passive filling:
| blood enters the heart into the atria
88
'Lubb' sound
AV valves closing
89
'Dupp' sound
pulmonary and aortic valves closing
90
features of a blood pressure trace regarding systole
- periods of systole (rising pressure)
- systole is typically shorter than diastole
- systolic pressure is the highest point on the trace
91
features of a blood pressure trace regarding diastole
- periods of diastole (falling pressure)
- diastole is typically longer than systole
- diastolic pressure is the lowest point on the trace
92
two kinds of cells in the heart
electrical
| contractile
93
electrical cells
- 1% of cardiac cells
- 'pale' striated appearance
- low actin and myosin
- moves electrical signals that cause the heart contractions through the heart as rapidly as possible
94
contractile cells
- 99% of cardiac cells
- striated appearance
- high actin and myosin
95
how action potentials propagate along the surface of the membrane of electrical and contractile cells
depolarisation starts at the sinoatrial node (SA node)
this signal spreads to neighbouring cells
in a contractile cell - increased cytosolic Ca2+ level, crossbridge attachment and contraction
96
what connects cardiac cells
intercalated disks
gap junctions
intercalated disks connect most cells of the heart
97
gap junctions...
- have pores with low resistance to ionic current
| - allow current flow between adjacent cells
98
gap junctions and spreading the impulse
- along conduction pathway
- between electrical and contractile cells
- between contractile cells
99
gap junctions cause ... for spreading the impulse
| and equals...
- increased speed of the impulse throughout the heart
- millions of cardiac cells to behave as one
- makes a functional syncytium
100
conduction pathway
| locations
1. SA node
2. internodal bundles
3. AV node
4. AV bundle, bundle branches
5. Purkinje fibres
101
SA (sinoatrial) node
pacemaker
generates the electrical signal
electrical signal sent in 3 different directions:
- right atrium
- across the interatrial bundle (made of electrical cells so signal moves extremely fast) into the left atrium
- atrioventricular node
102
internodal bundles
where the signal is sent through to get to the AV node
103
AV (atrioventricular) node
collects the electrical signal and pauses it to allow the atria to contract and ventricles to relax
104
AV bundle
| bundle branches
right and left bundle branches
105
Purkinje fibres
spreading up the ventricular walls to reach all the contractile cells of the ventricular wall to allow for maximum contraction
106
why does the contraction start at the apex of the heart not in the middle
having the contraction start at the apex and head towards the base of the heart means we have one efficient contraction to get as much blood out as possible in one big pump
107
excitation and the conduction pathway
1. quiescence ends when excitation spreads from the SA node
2. the atria are fully depolarised and contract
3. atria repolarise and relax, while AV node sends excitation to ventricles
4. ventricles fully depolarised and contract
5. ventricles begin to repolarise and relax
6. ventricles fully repolarised and relaxed, heart is back to quiescence
108
Electrocardiogram (ECG)
'Lead' - virtual line between two surface electrodes
| a single lead detects a difference between electrodes
109
Key features of an ECG
P - first bump
QRS - big peak
T - last bump
110
6 parts of an ECG
1. P
2. between P and Q
3. QRS
4. between QRS and T
5. T
6. after T
111
ECG
| P
atrial depolarisation
initiated by the SA node
causes the P wave
112
ECG
| between P and Q
with atrial depolarisation complete
| the impulse is delayed at the AV node
113
ECG
| QRS
ventricular depolarisation begins at apex
causing the QRS complex
atrial repolarisation
114
ECG
| between QRS and T
ventricular depolarisation is complete
115
ECG
| T
ventricular repolarisation begins at apex
| causing the T wave
