Cardiovascular System Flashcards
1
Q
What are erythrocytes?
A
Red blood cells
2
Q
What is the role of erythrocytes?
A
To transfer oxygen to tissues
3
Q
What makes red blood cells red?
A
Haemoglobin
4
Q
What is the role of white blood cells?
A
Protection against infection and immunity
5
Q
What does plasma mainly consist of
A
Water
6
Q
What is the role of plasma?
A
To carry ions and proteins, to keep things flowing
7
Q
Approximately what percentage of blood is plasma?
A
55%
8
Q
Approximately what percentage of blood is cellular elements?
A
45%
9
Q
What is the role of blood electrolytes (ions)
A
Osmotic balance, pH buffering and regulation of membrane permeability
10
Q
Give 3 ions found in the plasma
A
Sodium, potassium, calcium
11
Q
Give 2 examples of plasma proteins and their roles
A
Albumin = osmotic balance Fibrinogen = clotting
12
Q
What is the role of platelets?
A
Blood clotting
13
Q
Give 2 examples of white blood cells
A
Lymphocytes and neutrophils
14
Q
Where do arteries take blood to?
A
Brain and body
15
Q
Where do veins take blood to?
A
Heart and lungs
16
Q
What do veins have that arteries don’t and why?
A
Valves since they have to flow against gravity and so need to be able to stop back flow
17
Q
Why is arteries veins and capillaries having thin walls beneficial?
A
Easier exchange of oxygen and nutrients to target tissues
18
Q
What is the layer between smooth muscle and blood flow?
A
Endothelium
19
Q
Most blood vessels don’t have any direct affect on smooth muscles in the parasympathetic pathway, what is the exception?
A
Coronary vessels
20
Q
What is the indirect pathway for the activation of smooth muscles surrounding most blood vessels?
A
Endothelial cells (next to smooth muscles) contain receptors (typically M3) which when activated leads to the synthesis of NO. This diffuses to the smooth muscle cells causing relaxation (vasodilation) (via increase cGMP).
21
Q
What happens in the pulmonary loop?
A
Deoxygenated blood flows via the pulmonary artery to be oxygenated and exits via the pulmonary vein
22
Q
Outline the stages of blood flow through the heart
A
D.O blood from the body enters through the right atrium. It then enters the right ventricle and exits through the right ventricle via the pulmonary artery to the lungs. O. blood enters from the lungs through the left atrium and is sent to the rest of the body through the left ventricle via the aorta.
23
Q
Why is the left ventricle more muscular?
A
It has to pump the blood to the rest of the body
24
Q
What is venous blood?
A
deoxygenated blood
25
What part of the heart is responsible for the heart rate?
SA node
26
What is the SA node and where is it located?
A cluster of neuronal-like cells responsible for the heart rate found in the right atrium
27
How does the SA node control heart rate?
The SA node produces a signal which causes the atria to contract. This signal then travels down specialised bundles of conductive fibres to the AV node. The AV node creates an action potential which coordinates the contraction through the ventricles
28
Why is the delay between the atria and ventricles contracting important?
So that blood can flow nicely between the 2
29
On an ECG/EKG track, what do the 3 peaks represent per heart beat?
1. Activation of atria
2. Activation of ventricles
3. Recovery of ventricles
30
What are HCN channels?
Hyperpolarisation-activated Cyclic Nucleotide-gated Channels
31
How do SA and AV nodes release a signal/ action potential?
The opening of HCN channels results in slow depolarisation of the SA node and influx of Na+. T-type Ca2+ channels open allowing an influx of Ca2+ ions. Once the polarisation of the cells reach the threshold, rapid depolarisation (action potential) occurs as a result of L-type Ca2+ channels opening. HCN channels close. The K+ channels then open, polarising the cells due to an efflux of K+. The HCN channels then open.
32
When do HCN channels open?
If the nodes are very negative (polarised)
33
What part of the nervous system control the rate at which the HCN channels open?
Autonomic nervous system
34
How do signals travel through the ventricles and atria?
Contractile cells begin at resting membrane potential. The signal from the nodes arrive resulting in rapid depolarisation due to the opening of Na+ channels which allow an influx of Na+. Ca2+ channels also open = influx of Ca2+. The Na+ channels are then deactivated and the cells slowly repolarise as well as the opening of K+ channels allowing K+ efflux. The Ca2+ channels are still open and so prevents rapid polarisation. The Ca2+ channels then close resulting in polarisation of cells to its resting potential
35
What voltage is the threshold for the rapid depolarisation of node cells?
-30 mV
36
What are myocyte cells?
Pacemaker cells
37
What causes the negative resting membrane potential?
More Na+ and Ca2+ outside the cell and some K+ inside the cell - net negative on the inside
38
What is the resting membrane potential of contractile myocytes
-90 mV
39
How does the rate of repolarisation of the pacemaker cells and the contractile cells compare to nerve cells?
Much slower but pacemaker cells are faster than contractile cells
40
Why do contractile cells repolarise slower?
The calcium channels remain open for some time and balance out the efflux of K+ ions (repolarisation)
41
What is the standard heart rate
80 beats per minute
42
How does the sympathetic system affect heartrate?
Speeds up
43
How does the parasympathetic system affect heartrate?
Slows down
44
What neurotransmitter is responsible for sympathetic change in the heart?
Noradrenaline and adrenaline
45
What receptor does noradrenaline and adrenaline bind to in the heart?
Beta1
46
Which G protein is activated in the heart when the B1 receptor is activated
Gs
47
What nerve is involved in sympathetic innervation of the SA node and what does it release?
Cardiac nerve, releases noradrenaline
48
What receptor does noradrenaline and adrenaline act on?
B1
49
What G proteins are B1 receptors
Gs
50
When Gs proteins are activated, what is produced?
cAMP
51
How does cAMP increase heartrate?
cAMP binds to calcium and HCN channels, making them more sensitive resulting in faster depolarisation and more action potentials per unit time
52
What does chronotropy refer to?
The rate at which the heart beats
53
What does inotropy refer to?
Force of contraction of the heart
54
How does sympathetic stimulation of B1 receptors increase inotropy?
The Gs pathway is stimulated leading to more cAMP being produced which opens Ca2+ channels slowing the repolarisation of the membrane (stronger action potential), leading to a stronger force of contraction
55
What effect does the parasympathetic pathway have on the action potential trace?
Shifts to the right (slows down)
56
What is the main type of nerves that make up the parasympathetic nervous system?
Vagus nerves
57
When acetylcholine binds to M2 receptors, what is the G pathway that follows
Gi
58
How does the activation of Gi decrease chronotropy?
Adenyl cyclase is inhibited as well as G-protein-linked K+ channels being opened allowing an efflux of K+ (repolarises membrane) so it takes longer for the action potential threshold to be reached
59
What does decreased chronotropy mean?
Decreased heart rate
60
What detects the blood pressure in the main arteries?
Visceral afferents which report back to the brain stem. This then effects the ANS to adjust the blood pressure
61
What is the difference between systolic an diastolic blood pressure?
Systolic is the pressure at the peak of ventricular contraction
Diastolic is the pressure at the peak of ventricular relaxation
62
What is the dicrotic notch?
A notch in the blood pressure trace which occurs at the point where the aortic valve closes
63
What is MAP?
Mean arterial pressure, and indication of how hard the heart is working
64
At what values for MAP does it mean that organs may not get enough blood supply and become hypoxic?
Below 70 mmHg
65
What is the equation for MAP?
SBP + (2xDBP) / 3
66
What is the equation for MAP that includes cardiac output?
MAP = CO x PR, PR = total resistance
67
What is the equation for CO?
```
CO = SV x HR
SV = stroke volume
HR = Heart rate
```
68
What is primary hypertension?
When the cause is unknown and is asymptomatic until organ damage occurs
69
What is secondary hypertension
Caused by disease states, medication or drug abuse. Can also be during pregnancy
70
Give some risk factors of primary hypertension
Obesity, diabetes, smoking, stress, older ages, family history
71
How can cardiac output and heart rate be reduced in patients with hypertension?
By reducing the heart rate and the force of contraction using beta blockers e.g atenolol
72
How can resistance to blood flow be reduced?
By promoting vasodilation using an a-1 adrenergic receptor antagonist however this is not front line treatment
73
Which G pathway do alpha-1 antagonists block?
Gq
74
Which G pathway do beta blockers block?
Gs
75
How do beta blockers reduce blood pressure?
They block the Gs pathway, resulting in less Ca2+, making the action potential weaker so a weaker force of contraction
76
How do calcium channel blockers help to reduce blood pressure?
They reduce the length of the action potentials resulting in a reduced force of contraction (CO) and relaxes blood vessel muscles (PR)
77
briefly describe the renin-angiotensin-aldosterone system
The liver releases angiotensinogen. Renin is released by the kidney and converts angiotensinogen into angiotensin I. Angiotensin I is converted into angiotensin II which affects multiple processes that increase BP
78
Give 5 ways angiotensin II increases BP
Increases sympathetic activity (B1 + Gs stimulation, increase Ca2+), increased absorption of Na+ and K+ excretion = higher blood volume, adrenal cortex releases aldosterone which retains water, arteriolar vasoconstriction, pituitary gland secretes ADH which absorbs water
79
What are the first line treatments for hypertension in adults under 55
ACE inhibitors and ARBs
80
Give an examples of an ACE inhibitor and an ARB
ACEi: ramipril
ARB: losartan
81
When is a calcium channel blocker used as first line treatment?
Those over the age of 55 or of African or Caribbean origin
82
Give an example of a calcium channel blocker
Amlpodipine
83
Why is a CCB sometimes preferred as first line treatment?
Some patients have less renin in their system so the ACE inhibitors will be less effective
84
How do ACE inhibitors inhibit?
They mimic angiotensin I and so stop this being converted into angiotensin II
85
What are some common side effects of ACE inhibitors?
Hypotension, persistent dry cough (more common in women) and hyperkalaemia
86
Which side effect of ACEi is less common in ARBs and why?
Dry cough since bradykinin is less
87
Why do ACE inhibitors cause a dry cough?
ACE normally breaks down bradykinin, if this is inhibited, bradykinin increases which is associated with a dry cough
88
Why were people worried about ACE inhibitors and covid-19?
Angiotensin II binds to ACE2 however, ACEis reduce angiotensin II resulting in more ACE2 available to bind. SARS-CoV-2 binds to ACE2 to infect cells so in theory ACEis may increase the risk of severe covid-19
89
Why do ACE inhibitors not increase the risk of severe covid-19
In order for the virus to infect, it also has to bind to a surface protease. This becomes the limiting factor in the presence of ACEis and stops the increased risk factor
