Cardiovascular Physiology Flashcards
1
Q
What fluids make up the extracellular fluid?
A
Lymph, plasma and interstitial fluid
2
Q
What is serum?
A
Serum is blood fluid that has had the cells and clotting factors removed
3
Q
What are the major cells in blood?
A
Erythrocytes
Leukocytes
Thrombocytes (Platelets)
4
Q
What is a Reticulocyte?
A
An immature blood cell that hasn’t lost it’s nucleus yet
5
Q
Describe the general structure of a RBC
A
Biconcave disc with no nucleus
7-8 um diameter
No organelles
Has haemoglobin and metabolic enzymes
6
Q
What is the function of a RBC?
A
Transport of oxygen and carbon dioxide via haemoglobin
7
Q
What is Carbonic Anhydrase?
A
An enzyme in RBC’s that catalyses the slow reaction of carbon dioxide and water
8
Q
Describe the structure of Haemoglobin
A
4 poly-peptide sub-units (globin) (2a and 2B globin chains)
4 Haeme units
9
Q
Explain how oxygen is transport via haemoglobin?
A
- Each haeme unit can bind 1 oxygen at the Fe2+ site
- Oxygen binds to haemoglobin via a reversible reaction
- 4 oxygen molecules can be bound at once due to the presence of 4 haeme units
10
Q
Why does foetal haemoglobin have a greater affinity for oxygen?
A
It is to assist in the transport across the placenta
11
Q
Describe what stimulates the production of RBC’s
A
- low oxygen causes hypoxic environment
- Erythropoietin is secreted by the kidneys
- Erythropoietin increased the production of RBC’s in the bone marrow
N.B. Testosterone, Growth hormone and Thyroid hormone also stimulate production
12
Q
What is Packed Cell Volume (PCV) or haematocrit?
A
The percentage of RBC in a given volume. Normal values are 45% for men and 42% for women
13
Q
What are the 3 main types of WBC?
A
Granulocytes (Polymorphonuclear leukocytes)
Lymphocytes
Monocytes
14
Q
What is the function of an Eosinophil?
A
It destroys parasites via extracellular means (it is weakly Phagocytic).
Also has a role in allergies and inflammation
15
Q
What is the function of a Neutrophil?
A
Consume debris and pathogens, especially bacteria, they are first responders
16
Q
What is the function of a Basophil?
A
Contribute to allergic reactions and inflammation
17
Q
What is the role of Monocytes?
A
They become Macrophages, they are powerful phagocytes and release cytokines that enhance the immune response
18
Q
What are Thrombocytes?
A
Cytoplasmic fragments of Megakaryocytes (large cell in the bone marrow)
They are small flat discs about 1-4um wide
They have a cell membrane and organelles but no nucleus
19
Q
What is the function of Thrombocytes?
A
They clump together to plug gaps in the blood vessel
They respond to exposed collagen
Release growth factors and iniate repair
20
Q
What are the functions of the Cardiovascular System?
A
Delivery of nutrients to active tissues
Removal of waste products from active tissue
Transport of metabolites
Transport of hormones, antibodies and other substances to their active sites
21
Q
What is Pulmonary Circulation?
A
Circulation that goes to the lungs
22
Q
What is Systemic Circulation?
A
Circulation through the rest of the body
23
Q
What is Systole?
A
The period of contraction of the heart
24
Q
Whats is Diastole?
A
The period of relaxtion of the heart
25
What is Systolic Pressure?
The highest pressure in the systemic arteries during sytole, usually 120mmHg
26
What is Diastolic Pressure?
The lowest pressure in the systemic arteries during diastole, usually 80mmHg
27
How is blood pressure written?
Sytolic BP over Diastolic BP
28
What is pulse pressure?
The pressure difference between the Systolic and Diastolic BP, usually 40mmHg
29
What is mean arterial pressure (MAP)?
The arterial pressure averaged over the cardiac cycle, usually 90-95mmHg
30
What is the formula for MAP?
```
MAP = 2/3 DBP + 1/3 SBP
MAP = CO x total resistance
```
31
Blood flows from an area of ______ pressure to _____ pressure. Flow through the vascular system is produced by _______ to ________ blood pressure
Flows from high pressure to low pressure
Flow in the vascular system is produced by arterial to venous blood pressure
32
What is the Cardiac Output? What is it's formula?
The amount of blood pumped per minute, 5L/min at rest
| CO = SV x HR
33
What is the Frank-Starling Law of the heart?
Within physiological limits the heart pumps all the blood it receives
34
Increased venous return ______ ventricular volume which ________ the pressure that can be generated by the ventricles which ________ stroke volume
Increases, Increases, Increases
35
Why are myocardial cells connected by gap junctions?
Gap junction is a gap in the cell membrane that connect one cells cytosol with another's. It allows action potentials to move through a low resistance pathway. This means electrical signals are conducted smoothly
36
What is Annulus Fibrosus and what is it's function?
It is a fibrous "skeleton" that isolates the atria and ventricles electrically
37
What is the Sino-Atrial node?
A cluster of electrically active cells found where the sinus venosus joins the right atrium that generates the action potential that causes a heartbeat
38
What is the Atrio-Ventricular node?
A cluster of cells located at the top of the septum where the right atrium joins the ventricle. It delays and then conducts the impulse sent from the SA node
39
Which node has the faster pacemaker potential?
SA node, 90-100bpm
40
What is an ectopic beat?
A beat generated outside the normal pacemaker
41
Agents that alter the heart rate are called.....
Chronotropic agents
42
Positive chronotropic agents __________ the heart rate. For example _________
Increase the heart rate
| Adrenaline and Noradrenaline
43
Negative chronotropic agents __________ the heart rate. For example _________
Decrease the heart rate
| Acetylcholine
44
What happens during the P-wave on an ECG?
The atria depolarise
45
What happens during the QRS complex on an ECG?
The ventricles depolarise and the atria repolarise
46
What happens during the T-wave on an ECG?
The ventricles repolarise
47
Why does the QRS complex go down and then quickly up?
Because the heart contracts from the bottom upwards
48
Blood doesn't flow into the arteries until.......
Ventricular pressure exceeds the arterial pressure
49
What produces the heart sounds?
The closing of the valves
50
What is S1?
The first and loudest heart sound caused by the abrupt closure of the Atrioventricular valves
51
What is S2?
The second heart sound caused by the closure of the semi-lunar valves
52
What stage on a ECG does S1 occur?
The QRS complex
53
What stage on a ECG does S2 occur?
The start/middle of the T-wave
54
The thick and elastic walls of the arteries maintain ________ and _________ during diastole
Arterial pressure and blood flow
55
What is the formula for Mean Arterial Pressure?
```
MAP = CO x total resistance
MAP = 2/3 DBP + 1/3 SBP
```
56
Arterial resistance is controlled by __________
Sympathetic tone, directly proportional
57
__________ control the flow in a vascular bed by _______________
Arterioles by vasoconstriction and vasodilation
58
What is venoconstriction?
The constriction of veins to decrease capacitance, this increase venous return
59
Veins have a ____ capacitance and hold ____ of the volume of blood at rest
High capacitance and hold 2/3 of the blood volume at rest
60
What is the normal range for central venous pressure?
2-5mmHg
61
What is the normal Pulmonary Blood pressure? Why is it this value?
22/8 mmHg. It is less than systemic BP because there is less total resistance in the pulmonary circuit
62
The microcirculatory system consists of:
Arterioles, Venules, Metarterioles (aka preferred channels) Capillaries and Arteriovenous shunts
63
How do substances move across the capillary wall?
There are fenestrations between cells that allow the passage of small water soluble substances. Substances can also move through the cell.
64
What is Para-cellular transport?
Transport through the gaps between cells
65
What is Trans-cellular transport?
Transport through the cell via channels or endo/exocytosis
66
What is a colloid?
A relatively large particle that stays in constant suspension
67
What is colloidal osmotic/oncotic pressure?
The osmotic pressure formed by large proteins, like albumin, in the blood that tends to pull water into the vessel. It is about 25mmHg
68
What is Hydrostatic pressure?
The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity.
69
What is Starling equilibrium?
The point at which inward and outward pressure are equal and there is no net fluid movement
70
How is lymph circulated?
Peristaltic contractions move lymph along the lymphatic vessels and valves prevent back flow
71
What is Hyperaemia?
Increased blood flow
72
What is Ischemia?
Lack of blood flow
73
What is Active Hyperaemia?
The increase of blood flow due to increase metabolic rate
74
Following Ischemia, ________ occurs when flow is re-established. This is called___________
Hyperaemia occurs and we call this Reactive Hyperaemia
75
What metabolites cause Vasoconstriction?
O2 (except in pulmonary circuit)
| Glucose
76
What metabolites cause Vasodilation?
K+ in low doses
CO2 (except in pulmonary circuit)
Adenosine
H+
77
What is Angiogenesis?
The formation of new blood vessels
78
Increasing sympathetic tone ________ vascular smooth muscle
constricts
79
Vaso-constriction _________ total peripheral resistance
Increases
80
Veno-constriction __________ venous return
Increases
81
Vaso- and Veno-Constriction are controlled by the __________ nervous system
Sympathetic
82
Most sympathetic fibers release _________ that acts on the __________ on the smooth muscle producing contraction
Noradrenaline which acts on the alpha receptors
83
What affect does the parasympathetic nervous system have on the control of blood vessels
Not much, most vessels are not innervated by the parasympathetics
84
Sympathetic stimulation _______ cardiac contractility
Increases
85
Parasympathetic stimulation _________ cardiac contractility because ____________
Has little effect on contractility because the ventricles are not innervated by parasympathetic fibers
86
Venous return provides ________ regulation of the cardiac contraction
Intrinisic
87
Intrinsic regulation gives a _______________________
Constant ejection fraction
88
What are some extrinsic regulators of cardiac contraction?
Autonomic stimulation
Drugs
Hormones
89
Ionotropic Agents alter _________________________
The contractilitiy of the heart
90
Increased Ionotropy causes_______________
an icrease in the ejection fraction
91
Sympathetic nerve stimulation to the heart is a _________ and a _________ agent
Ionotropic and Chronotropic
92
Adrenaline is a _________ and a _________ agent when stimulating the heart
Ionotropic and Chronotropic
93
Sympathetic nerves innervate the __________ and stimulate positive ___________ and _________ actions
The whole heart and stimulate positive Chronotropic and Ionotropic actions
94
Baroreceptors are sensitive to changes in __________ and can be found in _______ and ______ arteries
Central Arterial Pressure and can be found in the aorta and carotid
95
Aortic baroreceptors are _____ sensitive than carotid baroreceptors
less
96
Outline the Cardiac Baroreceptor reflex:
1. Central arterial pressure is low
2. Decrease in parasympathetic tone to the heart increases heart rate
3. Increase in sympathetic tone to the heart increases heart rate
4. Sympathetic increase contractility and stroke volume
5. Increased cardiac output and blood pressure
97
Outline the Vascular Barororeceptor reflex:
1. Central arterial pressure is low
2. Increase in vasotone and total peripheral resistance (coronary and cerebral circulation largely unaffected)
3. Increased venous tone and return
4. Increased stroke volume and cardiac output
5. Increased Blood Pressure
98
How does ADH increase blood pressure?
1. Decreased BP leads to ADH secretion
2. ADH increases resorption of water which increases blood volume
3. Causes Vasoconstriction and increases total peripheral resistance
4. Blood pressure increases
99
What is the Central Ischemic Response?
A response activated when the blood supply to the brain is decreased and blood pressure drops below 60 mmHg.
It mimics the baroreceptor reflex but is much more potent, can raise pressure to 200 mmHg and block blood flow to everything except brain, heart and lungs
100
How is blood flow to skeletal muscles controlled?
During excercise local metabolites controls the flow via vaso- constriction/dilation. Flow can increase to about 15-20L/min
101
The heart receives ___% of Cardiac Output. During systole flow _______ and during flow______
5%, flow stops, flow occurs
102
_________ is an important metabolite in coronary flow . _________ and _________ have little effect on coronary flow
Adenosine
| Sympathetic stimulation and hormones
103
What does Autoregulation of blood flow do?
Keeps blood flow constant as pressure changes
104
What is the myogenic mechanism of autoregulation?
Pressure stretches smooth muscle and it contracts in response, this causes an increase in resistance
105
Fall in blood pressure ________ blood vessels and maintains flow
dilates
106
Increase in blood pressure ________ arterioles which keeps capillary flow and pressure constant
constricts
107
Cerebral blood flow maintains constant from ___mmHg to ___mmHg
60mmHg to 160mmHg
108
Increasing skin blood flow _________ heat loss
increases
109
Decreasing skin blood flow _________ heat loss
decreases
110
A large fall in temperature (to temperatures
Increases
111
___________ sympathetics activate sweat glands. Sweat glands release _________ a potent vasodilator
Cholinergic, Bradykinin
112
What is heat exhaustion?
When the cardiovascular system is unable to supply blood to both working muscles and the skin
113
What is heat stroke?
When the body is unable to cool and temperature rise until death occurs
114
Blood vessels constrict when exposed to ________
Cold
115
Blood vessels relax when exposed to ________
Heat
116
Explain the 3 ways blood flow to the skin is regulated when temperature changes
1. Vessels dilate when warm and contract when cold
2. Sensory nerves measure skin temperature and activate the reflex control of sympathetics via the Hypothalamus
3. Hypothalamus measures core temperature and controls sympathetic nerves to the skin
