Circulatory system Flashcards
1
Q
What is the fossa ovalis?
A
The remnant of a hole - foremen ovale - in the inter-atrial septum during foetal development
2
Q
What is the difference between blood and interstitial fluid?
A
Blood - contained within vessels
ISF - bathes tissues, and allows diffusion at capillary beds
3
Q
How do insects handle gas exchange in an open circulatory system?
A
They have a separate tracheal system for oxygen and carbon dioxide transport
4
Q
What are the main features of an open circulatory system? What organisms does it exist in?
A
- Fluid is open to body cavities and cells (in intercellular spaces)
- Lower pressure system
- Less efficient
- In most molluscs and some annelids
5
Q
What are the main features of a closed circulatory system?
A
- Fluid is enclosed within the system and doesn’t contact cells directly
- Higher pressure system
- More efficient
- In all vertebrates, cephalopod molluscs, and some annelids
6
Q
What is the circulating fluid in an open circulatory system known as?
A
Haemolymph
7
Q
How do insects transport nutrients and CO2?
A
Insects use their tracheal systems to transport nutrients and CO2
8
Q
What is the fluid in closed circulatory systems’ vessels called?
A
Blood
9
Q
What is in intercellular spaces in closed circulation?
A
Interstitial fluid (ISF)
10
Q
Where does diffusion occur in closed circulatory systems?
A
Capillary beds (between blood and ISF)
11
Q
How do closed circulations vay between species?
A
- Pump: anatomy of the heart varies (e.g. blood vessels entering/exiting, number of chambers can vary)
- Distribution vessels: single/double circulation patterns
12
Q
Flow rate equation?
A
flow rate = ΔP / R
- P = Pressure
- R = Resistance
13
Q
Resistance equation?
A
R = 8ηL / πr^4
14
Q
Compare changes in pressure (ΔP) and resistance (R) over open and closed circulatory systems
A
- Closed circulatory system: ΔP is high and R is high
- Open circulatory system: ΔP is low and R is low
15
Q
What are the functions of the mammalian cardiovascular system?
A
- Distribution of O2 and nutrients
- transport of CO2 and removal of metabolic waste
- Distribution of water, electrolytes, and hormones
- Thermoregulation
- immune system infrastructure
16
Q
What is the arrangement of the mammalian cardiovascular system?
A
- 4 chambered heart
- Systemic blood blood to vascular beds runs in parallel
- Pulmonary circulation runs in series
- High pressure system
17
Q
What do the heart and blood vessels provide the system?
A
- Heart = pressure/pump
- Blood vessels = resistance
18
Q
What is cardiac output (CO) and how do you calculate it?
A
Cardiac output is the total volume of blood pumped by the heart in one minute
cardiac output = heart rate x stroke volume
CO = L/min, HR = beats/min, SV = L/beat
19
Q
What happens to the CO during extreme exercise?
A
It approximately increases by five times the normal output
20
Q
How does the heart generate its own rhythm?
A
- SAN (pacemaker of the heart) sends a signal to the AVN, causing the atria to contract
- The AVN pauses to allow the ventricles to fill with blood
- The AVN passes the electrical impulse through to the LHS and RHS braches of the bundle of His
- Signal then passes through to the Purkinje fibres
- Left and right ventricles contract simultaneously
21
Q
What are the letters on a ECG waveform?
A
P, Q, R, S, T
22
Q
What happens in the heart during the P wave of an ECG waveform?
A
Depolarisation and contraction of the atria
23
Q
What happens in the heart during the PR interval of an ECG waveform?
A
Conduction of the signal through the AVN
24
Q
What happens in the heart during the QRS complex of an ECG waveform?
A
Depolarisation of the ventricles
25
What happens in the heart during the QT interval of an ECG waveform?
Ventricular depolarisation and repolarisation
26
What happens in the heart during the T wave of an ECG waveform?
Repolarisation of the ventricles so that they may become depolarised and contract again
27
How can the autonomic nervous system affect the heart rate?
- Parasympathetic nervous system: slows HR
- Sympathetic nervous system: accelerates HR
## Footnote
parasympathetic = rest and digest
sympathetic = fight or flight
HR adjusts according to this
28
What happens in phase 0 of a ventricular action potential?
3 Na+ move into the cell, depolarising it
29
What happens in phase 1 of a ventricular action potential?
2 K+ move out of the cell, repolarising the cell slightly
30
What happens in phase 2 of a ventricular action potential?
- K+ is still moving out of the cell
- Ca2+ moves in
31
What happens in phase 3 of a ventricular action potential?
More K+ move out of the cell until resting membrane potential is restored
32
What happens in phase 4 of a ventricular action potential?
Resting membrane potential is restored
33
What causes contracgtion of the cariac muscle?
- The contractile force follows shortly after the action potential
34
What are the names of the valves in the heart? Where are they?
LHS:
- Mitral valve (between atrium and ventricle)
- Aortic valve (betweenventricle and aorta)
RHS:
- Tricuspid valve (between atrium and ventricle)
- Pulmonary valve (between ventricle and pulmonary artery)
35
What are the phases of the cardiac cycle?
Systole (contraction) and diastole (relaxation)
36
What are the events of the cardiac cycle?
1. Atrial systole (ventricular diastole)
2. Ventricular systole
3. Ventricular ejection
4. Ventricular diastole
5. Passive filling of the atria
37
What can modify strok volume of the heart?
- How far the muscles are stretched (Starling's Law dictates the more they stretch the more they are able to recoil)
- Sympathetic stimulation (modulation of Ca2+ availability)
38
What tissue protects the heart and keeps it and the great cessels in place?
Pericardium
## Footnote
The pericardium also prevents overexpansion, provides lubrication, and limits the spread of infection
39
What supplies the cardiac tissue with its own blood?
The coronary vessels
## Footnote
Clots in these vessels are the predominant cause of myocardial infarction
40
Where does the right atrium recieve blood from?
- The head, neck, thorax, and upper limbs via the **superior vena cava**
- The coronary circulation via the **coronary sinus**
- The trunk, pelvis, and lower limbs via the inferior vena cava
## Footnote
blood is brought from the GI system to the vena cava by the hepatic portal vein
41
What direction do veins and arteries travel to the heart?
- Veins = into the heart
- Arteries = away from the heart
## Footnote
Remember: Ve(in) goes in!! The A in the artery stands for away!!
42
What is the name for the remnants of the hole in the inter-atrial septum during foetal development?
Fossa Ovalis
43
Where does the left atrium recieve blood from?
4 pulmonary veins (2 from each heart)
44
What are the heartstrings called? What are they controlled by? what do they do?
- Name: chordae tendinae
- Controlled by: papillary muscle
- Function: prevent atrioventricular valve prolape during ventricular systole
45
How many layers of cells are there in the heart tissue? What are they called?
there are 3 layers:
- Endocardium (innermost)
- Myocardium (middle muscle layer)
- Epicardium (outermost visceral pericardium)
46
What is the endocardium comprised of?
- Thin layer of endothelium
- Middle layer of connective tissue
- Deeper layer containing Purkinje fibres
47
What is the mycardium comprised of?
- Cardiac myocytes are joined by intercalated discs to form a syncitium
- connective tissues between the cardiac muscle fibres
## Footnote
Individual myocytes contain one or two central nuclei
48
What are the 3 types of cell-cell junctions linking the heart muscle at intercalated discs? What do they do?
1. Adherens Junctions link the actin
cytoskeleton to allow sarcomere
contraction
2. Demosomes link intermediate filaments
to provide strength
3. Gap junctions physically connect adjacent muscle cells to allow
cell-cell communication, coordination of
contraction from cell to cell along heart
muscle fibres
49
What are the 3 components that blood vessels *nearly* always have?
- Endothelium
- Smooth muscle
- Connective tissue
50
What are the 3 concentric layers that compose blood vessels?
- Tunica intima: endothelial cell layer plus connective tissue in contact with the lumen
- Tunica media: smooth muscle and connective tissue, much thicker in arteries than in veins, bordered by the **internal elastic lamina**, and the **external elastic lamina**
- Tunica adventitia: connective tissue
51
Compare the thickness of the tunica media in veins and arteries
- Thicker in arteries (to deal w the higher pressure)
- Thinner in veins (due to lower pressure in vessels)
52
What is exchanged across the endothelium? What does this fluid do?
Tissue fluid is exchanged across the endothelium:
- A filtrate of plasma that bathes cells
- Drained by the lymphatic system
- Blood exchanges materials with tissue fluid, then cells access that fluid
53
What junctional complexes compose the tunicca intima?
Sereral - including in particular:
- Tight junctions
- Adherens junctions
- Gap junctions
## Footnote
Tight junctions in particular is very important as it seals the intercellular space between two adjacent endothelial cells
54
Please explain the vasular anatomy of the tunica media
- Spindle-shaped smooth muscle cells
- Have a circular arrangement, wrapping around the vessel
- contraction allows for vasoconstriction and relaxation allows for vasodilation
## Footnote
circular rather than longitudinal arrangement
55
What vessel types does the blood flow through in its journey from the heart and back again?
## Footnote
like bilbo omg
1. Heart
2. Elastic arteries
3. Muscular arteries
4. Arterioles
5. Capillaries
6. Venules
7. Veins
## Footnote
Cycle repeats!!
56
What are the elastic arteries? What features do they share?
Aorta and pulmonary trunk are large elastic arteries
- Wide lumen
- Very thick walls
- Lots of **elastin** for stretch and recoil and **collagen** to prevent overexpansion
- Have vasa vasorum in their tunica adventitia to provide O2 to the smooth muscle cells themselves
57
What is the approximate diameter of an arteriole?
100μm
58
How is blood flow from arterioles to capillaries regulated?
Smooth muscle in the tunica media, wrapped circularly around the vessel constricts, acting as a valve to regulate blood flow
## Footnote
Pressure cannot be too high in the capillaries or they may be ruptured
59
What is the main fucntion of the capillaries?
Principal site of exchange between blood and tissue fluid
60
What are sinusoids? Where are they found?
- Sinusoids are specialised, widened capillaries that can carry more erythrocytes
- found in the bone marrow, spleen, lymph nodes and liver
61
What are the three types of capillary endothelium? Where are they found?
1. Continuous - muscle, lungs, skin
2. Fenestrated - kidney glomeruli, endocrine glands, small intestine
3. Discontinuous - liver, spleen, bone marrow (sinusoids)
## Footnote
Fenestrated and discontinuous allow for quicker passage of small molecules. Discontinuous allow larger molecules passage.
62
Where can fluid exchange occur as well as the capillaries?
Venules
## Footnote
Pressure is lower here, so there is a smaller tunica media, allowing diffusion across it
63
Compare lumen sizes of veins and arteries
- Veins tend to have larger lumen
- Arteies have tend to have smaller lumen
64
How do veins promote unidirectional flow?
- **Valves** ensure the blood is under enough pressure to return the blood to the heart and ensure unidirectional flow
- Veins are often**adjacent to arteries**, which can massage the blood in the vessel and gently squeeze the bloos superiorly
- **Adjacent muscles** also help massage the blood superiorly
## Footnote
If valves weaken and dont function properly, blood can pool, leading to their distension, causing varicose veins
65
What is the Blood Brain Barrier (BBB)
The interface between blood in capillaries and the tissues of the brain parenchyma
66
What are the main features of the BBB?
1. A strong, continuous endothelium
2. Specialised (very tight) tight junctions between endothelial cells
3. Additional cell barriers such as astrocytes and pericytes
## Footnote
cancer cell metastasis across the BBB is a serious ssue in breat and lung cancers (these cancers are very good at crossing the barrier and like to grow in the brain)
67
What is the definition of blood (or haemolymph) pressure?
Difference between the pressure in the system and the abient (transmural) pressure
68
Equation for flow rate (Q)?
Q = ΔP / R
69
Resistance equation?
R = 8ηL / πr^4
70
What happens to the resistance of a system in series vs in parallel?
- in series: more resistors = more resistance
- in parallel: more resistors = less resistance
71
What can smooth muscle tone be altered by?
- Neurotransmitters
- Hormones
- Endothelium-derived substances, e.g. endothelin, NO
- Metabolites and related factors e.g. hypoxia, H+, CO2
- Other locally produced factors, e.g. histamine, prostaglandin
- Oher factors:pressure or heat
72
Where does the greatest rsistance in the blood vessels occur?
Arterioles
73
What is the notch in the arterial pulse pressure wave caused by?
Closure of the aortic valve
74
Where does fluid flow in relation to total fluid energy?
Always moves from higher to lower fluid energy
75
How does a giraffe maintain circulation?
## Footnote
You would expect them to die as they drank water due to the increase in blood pressure around the brain
- Giraffe moves its legs and allows the blood to pool a little bit there
- The leg blood vessels vasodilate to try and compensate for this
