Cardiovascular System Flashcards
(244 cards)
1
Q
The cardiovascular system is made up of four main organs. What are these four organs called and what is there basic function?
A
Heart: pump
Arteries: supply
Capillaries: exchange
Veins/lymphatics: drainage
2
Q
Organs are made up of
A
vascular tissue
3
Q
Vascular tissue is made up of what two things?
A
Connective tissues and cells
4
Q
What two cell types are involved in the cardiovascular system?
A
Epithelial cells
muscle cells
5
Q
What is the purpose of the cardiovascular system?
A
to transport blood to the tissue around the body to exchange nutrients, oxygen and waste
6
Q
The cardiovascular system consists of what two smaller systems?
A
- blood vascular system
- lymphatic (vascular) system
7
Q
Describe the blood vascular system
A
This is a closed supply and drainage system (a continuous loop) with the heart at the centre supplying capillaries and draining back to the heart via the veins
8
Q
Describe the lymphatic system
A
Some of the fluid leaves the closed loop of the blood vascular system and goes through into surrounding tissue. The purpose of the lymphatic system to drain that fluid and bring it back into the vascular system on the right side of the heart (one way drainage)
9
Q
What are the two parts of the cardiovascular system (oxygenation)?
A
Pulmonary circuit
Systematic circuit
10
Q
Briefly describe the pulmonary circuit
A
Deoxygenated blood travels from the heart to the lungs to be oxygenated (gas exchange) and then return to the heart.
11
Q
Briefly describe the systematic circuit
A
Oxygenated blood leaves the heart and travels to the tissues via arteries and deoxygenated blood returns to the heart via veins
12
Q
What are the three primary principles of the cardiovascular system?
A
Supply
Exchange circuit
Drainage
13
Q
Describe the supply side of the cardiovascular system
A
- arteries are the only supply path
- oxygenated blood is pushed out of the heart at high pressure and high velocity into the arteries
- major arteries are situated to avoid damage (eg. deep in the trunk, flexor aspect aspect of limbs)
- important structures (eg. brain and hands) often receive supply from two sources
14
Q
What’s the difference between arteries and veins?
A
Arteries are thin, high pressure, high velocity and carry blood out of the heart.
Veins are thicker, low pressure, low velocity and carry blood back to the heart
15
Q
Describe the exchange side of the cardiovascular system
A
this involves the capillaries of varying permeability
- continuous (these are tightly controlled with a continuous cellular barrier of epithelial cells)
- fenestrated (leaky because of the little openings called fenestrations so solutions can enter or leave)
- sinusoidal (very leaky exchange)
16
Q
Describe the drainage side of the cardiovascular system
A
- deep veins (opposite to deep supply arteries)
- superficial veins (eg. in the hand)
- lymphatics (blood leaves the interstitial space)
17
Q
The cross-sectional area of veins/arteries is at least twice that of veins/arteries?
A
veins
arteries
18
Q
Describe the shape of the heart
A
- blunt, cone shaped
- pointed end (apex)
- broad end (at the top) is the base
19
Q
Describe the location of the heart
A
- in the media sternum between the two pleural cavities
- rotated to the left and tilted so that the base is tilting to the posterior
- the base is between the 2-3 numbered ribs and the apex is halfway along from the clavicle and down to between the 5-6 ribs
20
Q
What are the three layers of the heart wall
A
- endocardium
- myocardium
- epicardium
21
Q
What is the innermost tissue of the heart?
A
endocardium
22
Q
What is the middle tissue of the heart?
A
myocardium
23
Q
What is the outer tissue of the heart?
A
epicardium
24
Q
Describe the endocardium layer of the heart wall
A
- squamous epithelium (endothelium)
- loose irregular fibrous connective tissue (FCT) for support
- small blood vessels
- Purkinje fibres
25
List two diseases of the blood vascular system
- coronary artery disease (heart disease)
| - cerebrovascular diseases (stroke)
26
State a disease of the lymphatic system
spread of metastases (cancers)
27
Where can you find the labelled heart and a description of what the parts do?
On the wall
28
How does the left and right ventricles differ in terms of thickness of the myocardial (heart wall)?
The left side supplying the aorta is 1.5 cm thick whereas the right side supplying the pulmonary arteries is 0.5 cm thick
29
Describe the epicardium layer of the heart wall
- has a visceral pericardium which is part of the pericardium that has fused with the epicardium
- has large blood vessels
- has loose regular FCT and adipose/fat
30
What is the heart surrounded by?
The pericardium
31
Describe the pericardium including its relationship with the epicardium
The pericardium is a lubricated membranous sac that the heart sits in. It consists of fibrous pericardium and serous pericardium. The two layered serous pericardium is made up of a parietal layer and a visceral layer. These layers are separated by a fluid-filled space called the pericardial cavity. The visceral serous pericardium fuses with the epicardium
See slide 25 for a diagram
32
What is the function of the superior vena carva?
transporting deoxygenated blood from above the diaphragm (ie. head/chest/neck) to the right atrium of the heart
33
What is the function of the inferior vena carva?
transporting deoxygenated blood from below the diaphragm (everything apart from head/chest/neck) to the right atrium of the heart
34
What is the function of the left and right pulmonary artery?
To transport deoxygenated blood from the right ventricle to the left and right lung for oxygenation
35
What is the function of the left and right pulmonary veins?
To take deoxygenated blood to the left atrium of the heart from the left and right lungs
36
What is the function of the right atrium?
To receive deoxygenated from the superior and inferior vena carvae and the coronary sinus and transport it through the tricuspid valve to the right ventricle.
37
What is the function of the Pulmonary semilunar valve?
To prevent blood returning to right ventricle during filling (diastole)
38
What is the function of the coronary sinus?
To carry deoxygenated blood from the heart back to the right atrium
39
What is the function of the tricuspid valve?
To prevent blood from returning to the right atria during ventricular contraction
40
What is the function of the chordae tendinae?
To stop the tricupsid from slamming shut and flicking through to the other side
41
What is the function of the right ventricle?
Pumping blood to the lungs for oxygenation via the pulmonary arteries
42
What is the function of the papillary muscles?
These muscles connect the chordae tendinae to the free edge of the atroventricular valves to stop them from slamming shut
43
What is the function of the interventricular septum?
To separate the left and right ventricles
44
What is the function of the left ventricle?
To pump oxygenated blood through the aortic semilunar valve to the aorta to enter the systemic system
45
What is the function of the bicupsid valve?
To prevent blood from returning to the left atria during ventricular contraction
46
What is the function of the aortic semilunar valve?
To prevent blood returning to left ventricle during filling (diastole)
47
What is the function of the left pulmonary artery?
To transport deoxygenated blood from the right ventricle to the lungs to be oxygenated
48
What is the function of the aorta
To transport oxygenated blood from the left ventricle to the systemic system
49
What is the function of the left atrium?
To receive oxygenated blood from the pulmonary veins to transport through the bicupsid valve to the right ventricle.
50
Describe the atrioventricular valves, including the function and what they are called on the left and right side:
Function: prevent blood returning to the atria during ventricular contraction
right side: tricuspid valve
left side: bicuspid valve
51
At what stage are the AV valves open?
during diastole (filling phase)
52
At what stage are the AV valves closed?
during systole
53
Where are the AV valves located?
Between an atrium and a ventricle
54
Describe the semilunar valves, including the function and what they are called on the left and right side:
Function: prevent blood retuning to the ventricles during filling (diastole)
right side: pulmonary (semilunar) valve
left side: aortic (semilunar) valve
They are pushed open as blood flows out of the heart and closed as blood starts to backflow
55
How many cusps does the pulmonary (semilunar) valve have?
3
56
How many cusps does the aortic (semilunar) valve have?
3
57
At what stage are the semilunar valves open?
during systole
58
At what stage are the semilunar valves closed?
during diastole
59
Where are the semilunar valves located?
Between a ventricle and a exit tube (either the pulmonary artery or the aorta)
60
Describe the flow of blood into the heart from the heart
Immediately branching off the aorta are the right and left coronary arteries.
The RCA supplies the ventricular wall of the right ventricle.
The LCA branches to go over the inter ventricular septum and becomes the circumflex artery and the anterior inter ventricular artery which enters the left ventricle. The circumflex artery wraps between the left atrium and the left ventricle
61
Which side of the heart needs more blood supply and why?
The left side needs more blood supply because there is more muscle to pump the blood further around the systemic system
62
Describe the flow of blood out of the heart
The deoxygenated blood from the left side of the heart drains into the great cardiac vein and the deoxygenated blood from the right side of the heart drains into the small cardiac vein.
Both of the cardiac veins drain into the coronary sinus to enter the left atrium
63
Describe cardiac muscles
Similar to both smooth muscle and skeletal muscle:
one central nucleus like smooth muscle
striated like skeletal muscle
64
How thick are the capillary walls and why?
There are only one red blood cell thick because to bring them closest to the interstitial space to allow for maximum gas exchange as the distance is short
65
What is the function of myocardium?
beating of the heart
66
What are capillaries made of?
endothelium cells wrapped around to form a circle
67
Describe the cardiac muscle structure:
- are the striated?
- what do the cells look like?
- how many nuclei per cell?
- what do the nuclei look like?
- where are the cytoplasmic poles packed?
- how are they interconnected to neighbouring cells?
- striated
- short branched cells
- usually one nuclei per cell
- central, oval shaped nucleus
- cytoplasmic poles packed at the poles of the nucleus
- interconnected with neighbouring cells via intercalated disks
68
What is an intercalated disk (ICD)?
a specialisation of cardiac muscle
69
What percentage of the volume of the cell is made up of mitochondria?
Why is this significant?
20%
this mean that there is a very high ATP driven metabolism which is needed for the high energy requirements of cardiac muscle to beat
70
An intercalated disk is made up of what three intercellular junctions?
1. Adhesion belts
2. desmosomes
3. gap junction
71
Describe the role of the adhesion belt
Link the actin in one cell to the actin of another cell so that when the sarcomere in one cell contracts, it tugs on the actin of another cell to physically stimulate contraction.
72
How does an adhesion belt work?
by physical propagation of contraction
73
Do adhesion belts work in the vertical or horizontal portion?
vertical
74
Describe the role of a desmosome in an ICD
It links the cytokeratin of one cell to the cytokeratin of another cell with a lot of force (their skeletons are essentially buttoned together)
75
What is the cytokeratin?
A cell's flexible skeleton
76
Describe the role of a gap junction
For electrochemical communication from myocyte to myocyte to allow synchronisation between these short stubby cells to allow them to function as one long cell
77
Do desmosomes work in the vertical or horizontal portion and why?
vertical because it is perpendicular to the plane of contraction so you need them there to hold the neighbouring cells together
78
Do gap junctions work in the vertical or horizontal portion and why?
horizontal
79
Why is the conduction system of the heart important?
so that the filling and ejecting of the heart occurs in a synchronised motion
80
What is the purpose of the conduction system of the heart?
for coordination of heart contraction and atrioventricular valve action
81
How does the conduction system of the heart function?
by autonomic nerves altering the rate of conduction impulse generation
82
What are Purkinje fibres?
modified cardiac muscles
83
Briefly describe the conduction pathways of the heart
The first part of the conduction pathway is on the superior aspect of the right atrium. This is the sinoatrial node. It spreads through the atrial chamber by pathways called internodal pathways. When exiting the atrial chamber to enter the ventricular chamber, the pathways come together to form the atrioventricular node. This leads into the AV bundle which splits to the right and left bundle branches. The terminal parts of the network are Purkinje fibres.
84
Conduction pathways of the heart are not ______ _______ but _______ ________ ________
nervous tissue
| modified cardiac muscle
85
What is the sinoatrial (SA) node?
a little cluster of cells that spontaneously conduct action potentials, the rate of which are increased by sympathetic nerves or decreased by parasympathetic nerves
86
What is the purpose of the left and right bundle branches?
They are specialised pathways making sure that after contraction of the atrium occurs, we shoot the contraction down towards the apex to get contraction from the apex back up, not just as a continuous wave from the atria into the ventricles
87
Describe Purkinje cells
Differentiated myofibrils with
- central nucleus
- mitochondria
- glycogen
- lots of gap junctions
- some desmosomes
- a few adhesion belts
- make up 1% of cardiac muscle
88
Describe the pathway from the aorta to the sole of the feet
- The ascending, arching and descending thoracic aorta become the abdominal aorta which travels through the diaphragm.
- It leaves the thoracic cavity and splits at the aortic bifurcation into the common iliac artery. This branches down into the pelvic bowl to the exterior iliac artery.
- The EIA passes under the inguinal ligament and becomes the femoral artery until it reaches the knee.
Here is passes behind the knee as the politeal artery.
- Below the knee it splits into the posterior tibial artery (behind the tibia) which travels to the arches of the foot, and the anterior tibial artery (in front of the tibia) which travels to the top of the foot
89
Describe the pathways from the sole of the feet to the inferior vena cava
The plantar venous arch travels to the posterior tibial vein next to the posterior tibial artery. It hits the popliteal vein, the femoral vein, under the inguinal ligament to the exterior iliac artery and the common iliac artery and into the big vein that runs through the abdominopelvic cavity to the inferior vena carva
90
Describe the vein that is not matched by an artery
The great saphenous vein is superficial and so is not matched by an artery. It travels from the medial malleolus to the groin
91
What are the three layers of the blood vessels?
1. tunica intima
2. tunica media
3. tunica adventitia
92
What constitutes the blood vessels?
Heart valves, veins, arteries, capillaries
93
Describe the tunica intima
consists of:
- endothelium: a simple squamous epithelium which lines the lumen of all vessels
- sub-endothelium: a pad of loose FCT for the endothelium to sit on to support the delicate cells
- Internal elastic lamina: a condensed sheet of elastic tissue
94
Describe the purpose of internal elastic lamina
Because it is rich in elastin, it can store energy. Therefore it can take up energy and expand under pressure and re exert energy when the pressure decreases
95
The internal elastic lamina is well-developed in _______ and less developed in __________
arteries
| veins
96
The internal elastic lamina forms the boundary between
the tunica intima and the tunica media
97
Describe the tunica media
made up of smooth muscle and a variable content of connective tissue fibres, mainly collagen and elastin
98
How is the thickness of the tunica media proportional to the blood vessel diameter and the blood pressure?
Therefore, do arteries or veins have a thicker tunica media?
If two vessels have the same diameter but one has a thicker media, it means that that one is carrying blood at a higher pressure. This means that arteries have a thicker tunica media than a vein
99
Describe the structure of the tunica adventitia/externa
Made up of loose FCT with a high content of collagen and variable amounts of elastin.
Larger vessels contain the vasa vasorum
Lymphatics and autonomic nerves are also found in the region
100
What is the role of the vasa vasorum?
Larger vessels need blood vessels to bring blood into the capillaries to supply the smooth muscle in the tunica media. These blood vessels penetrate the adventiture.
101
Why are lymphatics and autonomic nerves also found in the tunica adventiture?
The smooth muscle of the adventiture is under autonomic control so there are sympathetic and parasympathetic nerves which penetrate the tunica media to control the contractile state of the smooth muscle
102
How does the femoral artery and the thoracic artery differ?
The thoracic artery is an elastic artery close to the heart and the femoral artery is a muscular artery out in the periphery.
The thoracic artery has a thick band of elastin whereas the femoral artery has a thicker band of smooth muscle.
103
Describe the differences in pressure between the thoracic and femoral artery
We have a heart (pump) driving circulation which is pulsatile but in capillaries, we don't want pulsatile flow (we want steady flow) so a pump does not fit the purpose. Instead, we engineer blood vessels to take out pulsatility (eg. thoracic aorta which dampens pulsatility).
We start with the heart and the pressure increases to systolic pressure, the heart relaxes, and the pressure decreases to diastolic pressure (filling pressure).
The elastic tissue in the thoracic aorta take up the energy during sytole and then during diastole when the heart is not pumping, the elastic tissue recoils back and squeezes on the blood to passively squeeze it.
104
What is an arteriole and what is its funciton?
It is the last part of an artery. It acts as the resistance vessel of circulation and this determines blood pressure.
105
How does an arteriole affect blood pressure?
The state of contraction of the smooth muscle in the tunica media controls the lumen. The pressure rises as it constricts as there is a smaller lumen so it is harder to blood to pass through
106
What is the function of capilllaries?
It is the site of exchange between the blood and the tissues
107
What are venules?
Assume exchange has occurred, the first past of drainage is the venules. Venules contain a monocuspid valve which ensures unidirectional flow to the right atrium
108
What are the functions of veins?
- they provide a low pressure, large volume transport system
- unidirectional flow
- they are capacitance vessels
109
Describe veins, including their three layers
irregular, flattened shape with large lumen and a thin wall
1. intima
2. media
3. adventiture
110
How do the three layers of veins and arteries differ?
The media of veins is only a few layers thick and the adventiture of veins is the thickest layer which is needed for capacitance
The IEL of veins is not as thick
111
Why do veins have spare capacitance?
Veins can hold extra blood volume. It can pool in the limbs if you are standing still. This means that the blood volume in the legs increases in the veins
112
Why do we get varicose veins?
Deep veins are surrounded by skeletal muscle which constricts to compress the vein and push the blood in both directions. The blood can not go back so a bicuspid valve stops back flow. If the walls move apart, the valve leaflets can not stop the the back flow so blood pools in the veins which causes varicose veins
113
What is the function of the capillaries?
they are the site of exchange between the blood and the tissues
114
What do we want to get into the tissue?
Oxygen and nutrients
115
What do we want to get out the tissue?
Waste
116
What are three physical features of the capillaries that allow it to perform its function?
1. very thin walls
2. large cross sectional area of the capillary bed
3. slow and smooth blood flow
117
Why do capillaries have thin walls?
To allow minimum distance for the exchange of O2, nutrients and waste
118
Why do capillaries need a large cross sectional area?
To maximise the rate of exchange
119
Why do we want slow and smooth blood flow through the capillaries?
to have the best opportunity for gas exchange to occur
120
The larger surface area of the capillary bed compared to the arterioles means
much slower blood flow
121
How does an endothelial cel wrap around to form a tube?
The cytoplasm of the tube is spread around in a tube and then it binds to itself by tight intercellular junctions
122
Describe the role of precapillary sphinctors
PCS control the flow of blood into the capillary beds. When they constrict, blood can not go into the capillaries and instead the blood goes straight to the venules
123
Precapillary sphinctors (PCSs) are made out of what?
smooth muscle cells
124
What is it called when the PCS stops blood flow to the capillaries and allows it to go straight into the venules?
vascular shunt
125
When would a vascular shunt be necessary?
If it is cold, then the PCS stop blood flow to the capillaries to stop loss of heat when blood flows to the epidermis
126
Describe the makeup of continuous capillaries
There is the endothelium cells wrapped around to form a complete tube. There is also a layer of connective tissue called the basement layer which is complete. If substances want to enter or leave the lumen, they have to pass through both the endothelium and the basement layer
127
Why do endothelium cells have two surfaces, where are they and what are they called?
All epithelium cells are polarised and so endothelium cells have two surfaces: the free surface which opens to the lumen (the apical surface) and the layer which faces the underlying tissue (basal)
128
What is the purpose of the basement layer?
It is a way to bond the basal surface of the endothelium cells to the underlying tissue
129
Describe the makeup of fenestrated capillaries
There are physical openings in the endothelium cells but the basement layer is still in tact. This means that solutes can physically bypass the endothelium but they still have to go through the basement layer
130
Describe sinusoidal capillaries
Thicker (3 or 4 RBC can fit) diameter capillaries for nutrient exchange rather than gas exchange.
There are large fenestrations in the endothelium cells and also large gaps in the basement layer
131
What is a good example of a sinusoidal capillaries?
In the liver to that the the nutrients from the blood can leak into the hepatocytes
132
What are three ways that substances can get through continuous capillaries?
1. diffusion through the membrane (for lipid soluble gas exchange)
2. movement through the intercellular clefts
3. transport via vesicles
133
What are four ways that substances can get through fenestrated and sinusoidal capillaries?
1. diffusion through the membrane (for lipid soluble gas exchange)
2. movement through the intercellular clefts
3. transport via vesicles
4. movement through fenestrations
134
What are the 4 functions of the lymph vascular system?
1. drains excess fluid and plasma proteins from tissues and returns them to the blood
2. filters foreign material into the lymph
3. Screens lymph for foreign antigens and responds by releasing antibodies and activated immune cells
4. absorbs fat from the intestines and transports it to the blood
135
Describe the lymphatic vessels
- large finger like projections, sitting around the blood vascular capillary
- lymphatic vessels called lacteals drain fat-laden lymph from the intestines to a collecting vessel called the cisterna chyli
- larger vessels have lots of valves to prevent backflow
136
Do the lymph vessels have tight cells for the fluid to flow through or not
no they have porous flaps so fluid can freely drain into the lymph channel
137
Are lymph walls thicker or thinner then veins?
Thinner
138
Describe the regions of the body drained by lymphatics
The right side of the body up until just above the end of the diaphragm drains into the right lymphatic duct and then into the right subclavian vein
The rest of the body drains into the thoracic duct and then into the left subclavian vein
139
Describe how lymphatic vessels called lacteals drain fat-laden lymph from the intestines to a collecting vessel called the cisterna chyli
Blood flows from the intestinal arteries to the capillaries There is an exchange between oxygen to the epithelium (the villi) and nutrients into the blood vascular system. Deoxygenated nutrient rich blood flows to the portal vein and there is an exchange between nutrient rich blood in the liver.
The fat drains into the lacteal and then it drains up to the cisterna chyli and then continues up to the left subclavian vein
140
When draining into the subclavian veins, the lymph passes through lymph nodes
And that's straight facts
141
Describe the flow of lymph through the lymph nodes
Lymph flows from afferent lymphatics to the meshwork of fibres inside the node. Here there are immune cells which you bath in the lymph to monitor for foreign antigens and possibly activate antibodies. Lymph continues to efferent channels.
142
Describe the lymph drainage of the breast and outline why that might be a problem
The lymphatic vessels of the breast drain into the axillary lymph nodes. This drains into the right lymphatic duct and then into the right subclavian vein.
If someone had breast cancer, it can travel from the breast into the blood using this path. It can travel to other parts of the body (metastasising)
143
How many chambers is the heart?
4
144
Blood flows in how many directions?
1
145
Arterial blood flows towards or away from the heart?
away from
146
Arterial blood flows towards or away from the heart?
towards
147
Why is the heart considered to be two pumps in series?
Because each circuit leads into the other around in a loop
148
How does the flow differ between the pulmonary and systemic circuit?
It is the same
149
How do we make sure the flow is the same between e pulmonary and systemic circuits?
The two pumps have to work together as one which means that the two atria contract first and then the two ventricles.
150
The tricuspid and bicuspid/mitral valves control the flow between the
atria and the ventricles
151
The aortic and pulmonary valves control flow from the
ventricles out to the circulatory vessels
152
When can actin and myosin not interact?
When the heart is relaxed
153
What is the signal to make actin and myosin interact?
Ca2+
154
What happens in terms of Ca2+ when it is time for contraction?
In resting heart, the concentration of Ca2+ is very low. When it is time for contraction, the Ca2+ is released from the sarcoplasmic reticulum which makes myosin bind to actin forming a cross-bridge. The myosin pulls on the actin to generate force
155
During one heartbeat how many myocytes are needed to contract?
All of them
156
How can we increase the force of contraction if all the myocytes are being used in a contraction?
We can increase the cystolic Ca2+ level, increase the number of cross bridges that form and this increases the force of contraction
157
How do you relax the myocytes?
Lower the Ca2+ levels in the cytosol and release cross bridges when ATP binds to myosin. There is a reduction in force because all of the myocytes are relxed
158
Define systole
contraction and rising pressure
159
Define diastole
relaxation and falling pressure
160
What are the key phases of the cardiac cycle? (6)
1. atrial systole
2. atrial diastole
3. ventricular systole (isovolumetric contraction)
4. ventricular systole (ventricular ejection)
5. ventricular diastole
6. isovolumetric relaxation
161
What does isovolumetric mean?
There is the same volume of blood within the ventricles. The Av and semilunar valves are all shut so the blood can not go anywhere. The volume stays the same
162
What is systolic pressure?
The highest pressure due to ventricular systole
163
What is diastolic pressure?
The lowest pressure at the end of ventricular diastole
164
What is pulse pressure?
the difference between the diastolic and systolic blood pressure
165
What is the mean arterial blood pressure?
The average blood pressure over one cycle. It is a bit below half way as more time as spent in diastole than systole so there is less time at high pressure
166
What is systemic blood pressure?
The pressure in the systemic system
167
What is the pulmonary blood pressure?
The pressure in the pulmonary circuit
168
Which is higher, the systemic or pulmonary blood pressure?
Systemic
169
What is hypertension?
Very high systolic blood pressure
170
What is hypotension?
low blood pressure
171
Which is more dangerous, hypertension or hypotension and why?
Hypotension is more dangerous because your body needs to push blood to the extremities including your brain. If the systemic blood pressure is not high enough then the blood can not be pumped to the brain and you can experience dizziness, fainting and nausea
172
How can the flow (Q) be equal in both the systemic and pulmonary circuits if the pressure between the two is so different?
The resistance in the systemic circuit is much higher than the pulmonary circuit because it is much longer
173
What is the equation for how blood flows in a single vessel?
Q = ΔP/R where Q is the flow, P is the change in pressure between one end of the vessel and the other and R is the resistance
174
Where can you find an explanation of the cardiac cycle?
In Google Docs
175
What are the main differences between contractile and electrical cells of the heart?
- electrical cells make up 1% of the cells of the heart whereas contractile cells make up 99% of the cells of the heart
- contractile cells are striated due to actin and myosin whereas electrical cells are pale and non-striated as there is no actin or myosin
- the job of the contractile cells is to form cross bridges and pull, generating power of contraction whereas the job of electrical cells is to conduct electrical current through the heart to get a coordinated heartbeat
176
The electrical signal goes between which cells of the heart?
All of them:
- between electrical cells
- between electrical cells and contractile cells
- between contractile cells
177
How does the impulse spread between both types of cardiac cells?
Through ions passing through gap junctions of the intercalated disks
178
What does the electrical signal tell the cell to do?
Release Ca2+ to stimulate cross bridge formation and so contraction occurs
179
What is a functional syncytium?
When the rapid movement of ions means that the electrical signal is moving through all the cells at once and they are all contracting at the same time
180
What is the part of the heart which holds the electrical signal?
The AV node
181
The sinoatrial node is referred to as the _______. Why?
pacemaker
| because all the cells of the SA node are specialised to let out a continuous and spontaneous release of chemical energy
182
What three places does the SA node send the electrical signal?
The right atrium, the AV node and the left atrium
183
What electrical events are generating the P wave, the ORS complex and the T wave?
P wave: atrial depolarisation
QRS: atrial repolarisation and ventricular depolarisation
T wave: ventricular repolarisation
184
There is high pressure in the ______ _______ _______
large systemic arteries
185
What is one reason why the mean arterial blood pressure has to be kept constantly high?
There needs to be a big difference between the pressure in the arteries and veins to create a driving force for unidirectional blood flow to the peripheries.
186
Arterial blood pressure and volume are determined by
a balance between blood flowing "in" and blood flowing "out" of the arteries
187
What constitutes "blood flowing in" and how does this relate to arterial blood pressure and volume?
- the blood flowing into the arteries (cardiac output)
- this increases the arterial blood volume
- because it is a higher volume in the same space, the pressure rises
188
What constitutes "blood flowing out" of the arteries and how does this relate to arterial blood pressure and volume?
- the blood draining out of the arteries into the capillaries to feed the different organs
- this decreases arterial blood volume
- because it is lower volume in the same space, the pressure falls
189
Cardiac output is determined by
stroke volume and heart rate
190
What is the stroke volume?
the amount of blood pumped out of the ventricle during a single heartbeat
191
What is cardiac output?
The flow of blood pumped by the left ventricle into the arteries each minute (vol of blood per unit time)
192
Cardiac output and arterial resistance affect
blood pressure
193
How is heart rate defined?
The number of contractions per minute
194
Mean arterial blood pressure can be calculated by the equation:
MAP: CO x TPR
195
What does TPR stand for?
total peripheral resistance
196
CO =
SV x HR
197
What are the units for CO, SV and HR respectively?
L/min
L/beat
beat/min
198
What causes peripheral resistance?
resistance of the arteries to blood flow
199
How do we determine what mean arterial blood pressure is, in its most basic sense?
A balance between the blood that is flowing in, and the blood that is flowing out of the arteries because MAP is determined by how much blood is in the arteries.
(fill arteries with more blood means putting more liquid in the same amount of space so pressure increases).
200
How does blood flow into the arteries?
The ventricles contract and they eject blood into the arteries and the ejected blood is what is adding to the amount of blood in the arteries.
201
What control "blood flow out" of the arteries?
resistance of arteries (how long it is, how wide it is and how easily it lets blood flow)
202
What determines blood flow out of the arteries?
Vascular resistance
203
What determines blood flow into the arteries?
Cardiac output
204
What two things can we do to increase MAP?
Increase cardiac output or increase vascular resistance (trapping it in arteries to increase pressure)
205
What is total peripheral resistance?
resistance of all the arteries
206
What are baroreceptors?
They are blood pressure sensors that detect changes in blood pressure measured as a change to the width of the arterial wall
207
Where are baroreceptors primarily located?
In the carotid artery and aorta
208
What afferent signal do they send to the brain?
When they detect a change in blood pressure, they send an afferent signal to the brain. If the blood pressure increases, they increase the frequency of the signal and if blood pressure drops then they reduce the frequency of the signal.
209
What is the difference between afferent and efferent signalling?
Afferent signalling is sent from the baroreceptors to the brain informing the brain of changes to blood pressure
Efferent signalling is sent from the brain/brainstem to the heart to adjust the mean arterial blood pressure
210
How does signalling from the vagus nerve affect the heart?
Due to an increase in blood pressure that is detected by the baroreceptors, an action potential is propagated down the vagus nerve from the brain which innervated the SA node and the AV node.
This tells the SA node to fire more slowly (ie. not conduct action potentials as quickly/frequently) and tells the AV node to put a pause on the signal before firing it again. This reduces the heart rate and therefore the CO is reduced and therefore the MAP is decreased.
211
How does signalling from the sympathetic trunk ganglion affect the heart?
Due to a decrease in blood pressure that is detected by the baroreceptors, an action potential is propagated down the sympathetic trunk ganglion from the brain which innervated the SA node and the AV node and the Purkinje fibres in the ventricle walls.
This tells the SA node to fire more quickly (ie. conduct action potentials more quickly/frequently) and tells the AV node to not put a pause on the signal before firing it again. This increases the heart rate and therefore the CO is increased and therefore the MAP is increased.
The innervation at the Purkinje fibres stimulates the release of more Ca2+ ions and therefore there is a greater force of contraction. This increases SV. As SV and CO have both increased, MAP increases.
212
What is the other reason (apart from being able to drive unidirectional flow around the body) why MAP needs to remain high?
To allow each organ to control its own perfusion so it is sufficient to meet it own needs
213
Although the heart is considered to be two pumps in series, the division of blood flow through the body can be described as
like a parallel circuit so that cardiac output is distributed to all the organs
214
Hoes exercise affect CO?
Exercise increases SV and HR so it increases CO
215
How does the distribution of CO change during exercise?
```
Increased blood flow to the
- muscle
- heart
- skin
Decreased blood flow to the
- GI tract
- Kidneys
Constant blood flow to the
- brain
```
216
How is MAP controlled during exercise?
If CO increases but MAP does not change greatly then TPR has to decrease
217
TPR reduces only, resistance does not fall for all the organs
True or False?
true
218
What are the organs that are getting more blood flow, and what happens to ensure that this happens without increasing MAP?
muscle, heart, skin are getting increased blood flow and so the resistance decreases
219
What are the organs that are getting less blood flow, and what happens to ensure that this happens without decreasing MAP?
Organs in the GI tract such as the stomach and kidneys are getting decreased blood flow and so the resistance increases
220
How is resistance and regional flow controlled?
arterioles allow us to adjust the resistance because the precapillary sphincters can widen, decreasing resistance and therefore increasing flow or they can tighten, increasing resistance and decreasing flow.
221
What is the rule of 16?
This describes how the resistance relates to vessel radii because if the radius is changes by a factor of 2 (doubling or halving), the resistance is change by a factor of 16
222
What is the equation relating the resistance to the luminal radius?
R = 1/(r^4)
223
What is vasodilation?
When the smooth muscle relaxes, there is decreased resistance and the diameter of the blood vessel increases
224
What is vasocontriction?
When the smooth muscle contracts, there is increased resistance and the diameter of the blood vessel decreases
225
What three things control vascular resistance?
1. mechanical
2. neural
3. humoral
226
The control of regional blood flows is modulated by controlling
Vascular (arteriolar) resistance
227
We need extra blood so there isn't just blood to keep you alive. Where is this kept?
In the veins
228
Define compliance
the extent to which a vessel allows deformation in response to an applied force
229
How does the compliance differ between arteries and veins and why?
arteries have a thick wall which means it has low compliance
| veins have a thin wall which means is has very high compliance
230
What is the equation for compliance?
C = ΔV/ΔP
231
Veins are very compliant which means that as pressure increases, there is
a very large increase in volume
232
Why do veins have survival value?
Because they can transport blood to the arteries in emergencies
233
What happens if there is an arterial puncture?
- loss of arterial blood
- loss of arterial blood pressure
- but we want it to be really high
- using venoconstriction, blood in the veins is pushed back to the heart to increase SV, CO and therefore MAP
234
What is venoconstriction?
constriction of the muscles around the veins to push the blood around the body
235
Which is larger, venous volume or arterial volume?
Venous volume
236
In the upright position, venous volume ________ whereas venous volume above the heart ________ and this causes _________
increases
decreases
venous pooling
237
What are the two ways that the veins counteract pooling?
using valves
| using the tone of surrounding muscles to hold shape
238
Muscle tone acts to
stiffen the veins and make them less compliant and prone to pooling
239
Skeletal muscle pump affects _____ ______ to the heart
venous return
240
How does exercise increase venous return?
when you exercise, you breath faster so your diaphragm is going up and down faster, this pushes on veins which increases venous return
241
Increase venous return means increased
SV
242
What does Starling's Law state
the more stretched the muscles fibres are before a contraction, the stronger the contraction will be
243
How does increasing venous return increase force of contraction and therefore SV?
Increasing venous return stretches the heart which means that the actin and myosin filaments are further apart. This means that they can generate a stronger contraction and therefore SV increases
244
Why does the SV decrease when doing a whole body tilt?
On the tilt, your muscles can not contract which means there is decreased venous return and so the heart is not stretched and therefore it can not generate as much force so SV decreases
