Cardiovascular Physiology Flashcards
1
Q
What does the P wave represent on an ECG?
A
Atrial depolarisation
2
Q
What does the T wave represent on an ECG?
A
Ventricular repolarisation
3
Q
What does the QRS complex represent on an ECG?
A
Ventricular depolarization
4
Q
What is a positive chronotrope?
A
Something that increases heart rate
5
Q
What is a positive inotropy?
A
Something that increases the contractility of the heart
6
Q
Where does nervous system regulation of the heart originate?
A
The cardiovascular centre of the medulla oblongata
7
Q
What neurotransmitter does the vagus nerve release?
A
Acetylcholine
8
Q
What is the effect of the PSNS on the heart?
A
Decreased heart rate
9
Q
What is the effect of the SNS on the heart?
A
Increased heart rate
10
Q
What is cardiac reserve?
A
The difference between the cardiac output at rest and the maximum cardiac output
10
Q
How does hypothermia affect the heart?
A
Decreases heart rate
11
Q
What is cardiac output?
A
The amount of blood ejected into the aorta per minute
11
Q
How does hyperthermia affect the heart?
A
Increases heart rate
12
Q
What is the equation for cardiac output?
A
CO = HR x SV
13
Q
What is stroke volume?
A
The amount of blood ejected out of the ventricle each cardiac cycle
14
Q
What is contractility?
A
The forcefulness of contraction
14
Q
What is after-load?
A
The amount of work the heart must do to generate ventricular pressure sufficient to eject blood.
15
Q
What is pre-load?
A
The stretch on the heart before in contracts
16
Q
What 3 factors affect SV?
A
Preload, afterload, contractility
17
Q
Describe the Frank-Starling law
A
The stretch of the ventricular walls as the ventricle fills determines how forceful the contraction is - the more the muscle fibres are stretched, the more forceful the contraction.
18
Q
What is TPR?
A
The amount of force affecting resistance to blood flow throughout the circulatory system
19
Q
Is the mean blood pressure in the aorta closer to the systolic or diastolic blood pressure?
A
Diastolic
20
Q
What is the speed of conduction from the SA node through the Atrial muscle?
A
Slow, 0.5m/s
20
Q
What is the speed of conduction through the AV node?
A
Very slow, 0.05m/s
21
What is the speed of conduction through the AV bundles and purkinje fibres?
Fast, 5m/s
22
What is the time of delay of the AP through the AV node to the ventricels?
100ms
23
What is the purpose of the delay in AP through the AV node?
Allows for the atria to contract before the ventricles to fill them with a bit more blood
24
Where is the SA node located, precisely?
Right atrial wall just inferior to the opening of the superior vena cava
25
Approximately how many APs does the SA node fire a minute?
100
26
What is the intrinsic heart rate of the SA node?
40-60 BPM
26
What is the size of the AP produced by the SA node (mV)
1.5mV
27
Where is the AV node located, precisely?
Interatrial septum, just anterior to the opening of the coronary sinus
28
What is the last part of the heart to contract?
Apex
29
What kind of junctions are between cardiac myocytes?
Gap
30
What causes the gradual depolarisation of pacemaker cells?
Leaky Na+ channels
30
Approximately how long is a pacemaker cell AP?
0.8 seconds
30
What ion causes depolarisation of ventricular myocytes?
Na+
30
What causes the plateau phase of a ventricular myocyte AP?
VG slow Ca2+ channels inflow and K+ outflow
31
What ion causes the repolarization of the cardiac myocytes?
K+
31
What is the ion that rushes into the pacemaker cells once threshold is reached?
Ca2+
32
What causes the repolarisation of the ventricular myocyte?
Ca2+ channels closing and more K+ channels opening
33
How long does a ventricular myocyte AP last?
300ms
34
What is the change in MP in the ventricular myocyte AP (mV)
-90mV to +30mV
35
What is the change in MP in the pacemaker cell AP (mV)
-60mV to +10mV
36
How long does the depolarisation of ventricular myocytes take?
1-2ms
37
How long does the plateau phase of ventricular myocyte APs last?
200ms
38
How long is the repolarization phase of ventricular myocyte APs?
20-50ms
39
What is the refractory period?
The time in which a second AP cannot be triggered
40
Why is it good that the cardiac refractory period last longer than the normal AP?
To prevent tetanus from occuring
41
Do cardiac action potentials have after-hyperpolarisation phases?
No
42
What is the order of waves on an ECG?
P, QRS, T
43
What might an enlarged P wave indicate?
Damage/enlargement of the atria
44
What does the S-T segment of an ECG represent?
The plateau phase of the ventricular AP, when the entire ventricle is depolarised
45
When on the ECG does atrial repolarisation occur?
QRS wave (not seen though due to being smaller than ventricular depolarisation)
45
Where are baroreceptors located?
Aortic arch and carotid sinus
46
What is angina pectoris?
Pain accompanying myocardial ischemia
47
What is the function of baroreceptors?
Monitor changes in blood pressure
48
What does the vasomotor region of the cardiovascular system control?
Vasoconstriction
49
What do cardiac accelerator nerves from the CV centre do?
Increase heart rate and contractility
50
What are the inputs to the CV centre?
Proprioceptors (joint movements)
Baroreceptors (blood pressure)
Chemoreceptors (blood acidity)
Higher brain
51
What are some positive inotropic agents?
Increased SNS
Catecholamines (e.g. NE & E)
Glucagon
Thyroid hormones
Ca2+ in extracellular fluid
52
What does the cardiac accelerator nerve innervate?
SA node, AV node, Ventricular myocardium
53
What decreases afterload?
Decreased arterial blood pressure
54
What is starlings law of the capillaries?
The movement of fluid across a capillary wall depends on the balance between hydrostatic and oncotic pressure gradients
55
What does and increase in venous return most directly affect?
Stroke volume
56
What does the viscosity of blood most directly affect?
Vascular resistance
57
What is hypertension?
High BP
58
What is the ejection fraction calculation?
(EDV-ESV/EDV) x100
59
How many papillary muscles are in the right ventricle?
3
60
How many papillary muscles are in the left ventricle?
2
61
At what region of the spinal cord do the sympathetic nerves branch off to the heart?
Thoracic
62
Approx. how many heart beats does it take to decrease heart rate?
1
63
Approx. how many heart beats does it take to increase heart rate?
5-10s
64
What is tachycardia?
Fast resting heart rate >100bpm
64
What is bradycardia?
Slow resting heart rate >50 bpm
65
What does blood flow in specific tissue depend on?
Pressure differences and resistance
66
What is the equation for stroke volume?
EDV-ESV
67
What are 2 negative inotropic agents?
K+ & Na+
67
What do positive inotropic agents usually do?
Increase the flow of Ca2+ into myocardium during APs to increase contraction
68
What is the result of a filtration imbalance?
Oedema
69
Where does the lymphatic system return fluid back to?
Jugular veins in the neck
70
Every cell in the body is within ____ cells of a capillary
2
71
What is velocity of blood proportional to?
1/cross sectional vessel area
72
Besides arterioles alter diameter, what is another way blood flow is controlled through capillaries?
Pre-capillary sphincters
73
What is the carotid sinus?
Main blood supply to the brain
74
What does ANP cause?
Vasodilation and decreased blood volume
75
What is the effect of aldosterone and ADH on blood volume?
Increase in blood volume
76
What are some of the immediate effects of a haemorrhage?
Increased HR -> increase TPR (vasoconstriction) -> increased VR -> BP maintained
77
What nerves connect baroreceptors to the brain?
Cranial nerves
78
What receptors on blood vessels does the SNS stimulate?
Alpha receptors
78
What is tonicity?
Vascular tone
79
What is resistance proportional to?
1/radius
79
What is the equation for BP
CO x TPR
80
Is the circulatory structure a series or in parallel?
Parallel
81
What is the effect of aortic plaques (atherosclerosis) on afterload?
Increased afterload
81
What factors affect preload? (5)
- Venous return
- Blood volume
- Filling time
- Respiratory pump
- Compliance (stiffness)
82
What is the effect of increased afterload on SV?
Decreased SV
83
How many baroreceptors are in the aortic arch?
2
84
What is Poiseuille's law?
Resistance is directly proportional to blood viscosity and vessel length, and inversely related to the fourth power of the radius of the blood vessel
84
How many baroreceptors are in the carotid arteries?
2 (1 in the left, 1 in the right)
85
Where are cardiopulmonary receptors located and what do the sense?
Located in the vena cava and sense changes in blood volume
86
What 2 pressures drive filtration?
BHP & IFOP
87
What 2 pressures drive reabsorption?
BCOP & IFHP
88
What occurs if net filtration is positive?
Filtration
89
What occurs if net filtration is negative?
Reabsorption
90
What is the normal BCOP?
26mmHg
91
What is the normal IFHP?
0mmHg
92
What is the normal IFOP?
1mmHg
93
Which way does IFOP flow?
↑
capillary
94
Which way does IFHP flow?
↓
capillary
95
Which way does BCOP flow?
↓
capillary
96
Which way does BHP flow?
↑
capillary
97
What is the normal BHP at the arterial end of the capillaries?
35mmHg
98
What is the normal BHP at the venous end of the capillaries?
16
99
What happens to fluid left in the interstitial space?
Gets drained by the lymphatic system
100
What are the 3 methods of capillary exchange?
Diffusion
Transcytosis
Bulk flow/filtration
101
What is transcytosis?
Vesicles of large lipid insoluble molecules (e.g. insulin)
102
What is bulk flow/filtration?
Passive movement of fluid and substances
103
What is the key driver of filtration?
Pressure gradients
104
How many litres of fluid are reabsorbed by the capillaries per day?
17L
105
How many litres of fluid are removed by the lymphatic system per day?
3L
106
What is aortic stenosis
Narrowing of the aorta
107
Where are the baroreceptors in the kidneys located?
Juxtaglomerular cells
108
What is the moderator band made of?
Cardiac muscle
109
What does the moderator band do to the papillary muscles?
Primes them to contract chordae tendineae ahead of ventricular contraction
