Cardiovascular System Flashcards
1
Q
Main function and structure of Resistance/Muscular artery
A
Muscular element is most significant, plays major role in regulation of blood pressure
2
Q
Main function and structure of arteriole
A
Muscular tissue is most significant (although smaller amount than resistance artery), plays major role in regulation of blood pressure
3
Q
Main function and structure of Capillary
A
Assembled of only endothelium and basal tissue, slows rate of blood flow to maximise exchange
4
Q
Structure of Venules
A
Muscle tissue is less significant, larger lumen
5
Q
Structure of Veins
A
Large proportion of fibrous tissue, large lumen and relatively large smooth muscle layer
6
Q
Functions of Heart
A
Pumping blood around the body and generating blood
pressure
Sending deoxygenated blood to the lungs to be oxygenated
Sending oxygenated blood to the whole body
Separates pulmonary and systemic circulation
Provides unidirectional (one-way) blood flow and prevents back flow (valves)
7
Q
Which part of the heart is more muscular
A
Left part (Ventricle)
8
Q
Why is the left ventricle more powerful
A
As the systemic circuit comprises of many parallel circuits therefore requires greater pressure
9
Q
Functions of CVS
A
- Oxygen and CO2 transport
- Nutrient and waste product transport
- Disease protection and healing
- hormone delivery
- body temperature regulation
10
Q
What is the adaptation of Ohm’s law used for calculation of cardiac output.
A
Q = ΔP/R
ΔP - Mean Arterial Pressure Q - Cardiac Output
R - Total Peripheral Resistance
11
Q
What is Polycythaemia?
A
Elevated red blood cell count in Haematocrit
12
Q
Describe the main function and structure of Conduit/Elastic Arteries
A
Large Proportion of elastic tissue and smooth muscle. Main function is to conduct blood under High pressure
13
Q
What is starling’s law?
A
the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles
14
Q
Which side of the heart is located most anteriorly ?
A
Right (Pulmonary)
15
Q
Which side of the heart is located most posteriorly ?
A
Left (Systemic)
16
Q
What separates the Right and Left Ventricles?
A
Anterior Interventricular Groove
17
Q
What separates the Right Atrium and Ventricle?
A
Anterior Atrioventricular Groove
18
Q
Where is the right auricle located?
A
Superior surface of the right atrium
19
Q
What vessels supplies the lungs with deoxygenated blood?
A
Pulmonary Arteries
20
Q
Where do the pulmonary arteries arise from?
A
Pulmonary Trunk from Right ventricle
21
Q
Where does the Inf. Vena Cava arise from?
A
Diaphragm, brings blood from lower half of body
22
Q
Where does the Sup. Vena Cava arise from?
A
Joining of Brachiosophalic and Subclavian artery.
23
Q
What are the 3 parts of the pericardium?
A
Fibrous Pericardium
Parietal Pericardium
Visceral Pericardium
24
Q
What is the gap between the parietal and visceral pericardium called?
A
Pericardium Cavity (Full of pericardiac fluid)
25
What forms the majority of the view on the posterior aspect of the heart?
Left Ventricle
26
What are the roles of the valves in the heart?
To prevent flowback in the heart during constriction
27
What valve separates the Right Ventricle and Pulmonary Trunk?
Semi Lunar Valve
28
What valve separates the Right Atrium and Ventricle?
Tricuspid Valve
29
What do the Chorda Tendini do?
They prevent the tricuspid valves from 'blowing back' into the right atrium.
30
Where do the Chorda Tendini attach?
Papillary Muscles and Tricuspid Valves
31
What is the Fossa Ovalus?
A fossa in the right atrium and left ventricle. Open as foetus to allow blood to 'skip' pulmonary system.
32
What is the Coronary Sinus?
A collection of veins delivering deoxygenated blood to the right atrium
33
What is the coronary's sinus relationship to the position of the AVN?
It is slightly inferior
34
What is the AVN?
Atrio Ventricular Nodes
35
What is the SAN?
Sino-Atrial Nodes
36
What is known as the pacemaker?
The SAN
37
What are the layers of the heart wall?
Pericardium,
Myocardium
Endocardium
38
Function of Pericardium?
Fixes the heart to the mediastinum,
Gives protection against infection
Provides the Lubrication for the heart
39
What is the function of the Myocardium?
Stimulates heart contractions and relaxation
| Provides scaffolding for heart chambers
40
What is the function of endocardium?
Controls myocardial function
| Controls blood-heart barrier
41
What are the main cells of the myocardium?
Cardiomyocytes
42
What are the main identifiable structures in a cardiomyocyte?
```
T-Tubule
Sarcomere
Z Disk
Intercalated Disk (Joint with neighbouring cell)
Sarcoplasmic Reticulum
```
43
Characteristics of cardiomyocytes?
Single centrally located nucleus
Branching structure
Plenty of mitochondria
Abundant reserve of myoglobin
44
What two fibres make up the cardiac autorythmic system?
Pacemaker Cells
| Conduction fibres
45
What is sarcoplasmic reticulum?
Periphery layer of endoplasmic reticulum, important in cardiomyocytes for absorption and storage of calcium
46
What is the main substrate for oxidative phosphorylation in cardiomyocytes?
Lipids
47
What do T-Tubules do?
Increase surface area of cardiomyocytes. Allows for maximum Ca2+ absorption Required for excitation of the cells.
48
Where are T-Tubules found?
In the outer membrane, present as indentations increasing surface area
49
Where could you find a gap junction in cardiac muscle?
Between the cardiomyocytes, more specifically the intercalated disks
50
What are gap junctions?
intercellular channels that allow for direct chemical communication between adjacent cells through diffusion of ions and small molecules without contact with the extracellular fluid.
51
What are desmosomes?
fasteners through the plasma membrane of adjacent cells by means of intermediate filaments composed of keratin or desmin to form a dense plaque.
52
What are Tight junctions?
act as barriers that regulate the movement of water and solutes between epithelial layers.
53
Are tight junctions present in cardiomyocytes?
NO!!!!!!
54
What proteins are present in the gap junctions?
Connexin
Innexin
Pannexin
55
What is Connexon?
6 Connexin subunits
56
What is Innexon?
6 Innexin subunits
57
What is Pannexon?
6 Pannexin subunits
58
What are the main pacemakers in the heart?
```
SAN
AVN
Bundle of His (Their)
Purkinje Fibres
Bachmann's Bundle
```
59
What does the SAN do?
- establishes rhythm at the highest rate of pulse generation (70-100 bpm)
- impulse spreads from the SA node throughout specialized internodal pathways:
60
What is the AVN?
- intrinsic rate of AV node is 40-60 bpm
- delays the impulse from SA node by ~100-120 ms to let ejected blood fully migrate from atria before ventricles contract
- it electrically connects the right atrium and right ventricle
61
What is the Bundle of His
- intrinsic rate of the bundle of His is 20-40 bpm
- transmits impulses from the atrioventricular node to the ventricles of the heart
- branches into the left and the right bundle branches
- speed of impulse is 1 m/s
62
What are the purkinje fibres?
- intrinsic rate of Purkinje fibers is 15-30 bpm
- distribute the impulse to the myocardial contractile cells in the ventricles
- speed of impulse is 5 m/s
- excitation and contraction begin at the apex and travels toward the base of the heart
63
What is Bachmann's bundle?
a specialized pathway band that conducts the impulse directly from the right atrium to the left atrium
64
What is the importance of Calcium?
regulation of Ca2+ homeostasis is central to the control of the heart
- It is responsible for depolarisation and execution
- Responsible for activation of contraction of cardiac muscle
- Important signal molecule and second messenger
65
What is the basic mechanism of contraction?
1 – Na+ channels
2 –L-type Ca2+ channels
3 – Ca2+ induced Ca2+ release from Ryanodine receptors (RYR)
4 – Ca2+ stimulates the contractile apparatus
66
What is the basic mechanism of Relaxation?
1 – Ca2+ reuptake into SR
2 – withdrawal of Ca2+ to the extracellular media
3 – Exchange of Ca2+ for 3Na+ then 3Na+ exchanged for 2K+
4 – Activation of K+ channels
67
Where are Ryanodine Receptors found?
On the sarcoplasmic reticulum
68
What helps exchange Ca2+ for 3Na+ in relaxation?
A Na+/Ca2+ exchanger
69
What helps swap 3Na+ for 2K+ in relaxation?
Na+/K+ ATPase
70
What is SERCA?
Sarco Endoplasmic Reticulum Calcium ATPase
71
What is SERCA's function?
It helps 'pump' Ca2+ ions into the sarcoplasmic reticulum
72
How is SERCA activated?
It is constantly inhibited by PLB, when PLB is phosphorylated the SERCA is activated
73
Average diastolic (relaxed) sarcoma length is?
2-2.2 um
74
Maximal length of sarcomere is?
2.6 um
75
What is average man's resting cardiac output?
5L/min
76
What is the average man's exercise cardiac output?
Fit young person: 20L/min
| World Class Athlete: 35L/min
77
What is Diastole?
Heart muscles at rest
78
What is systole?
Heart muscles contracting
79
Roughly, how long is spent in diastole?
2/3 of the time
80
What does MAP stand for?
Mean Arteriole Pressure
81
How do you calculate MAP?
Diastolic Pressure + 1/3 Pulse Pressure
82
What unit is pressure measure in?
mmHg
83
What is Pulse Pressure?
Systolic - Diastolic pressure
84
How do you work out Diastolic pressure?
Lower end of Aortic Pressure
85
How do you work out Systolic Pressure?
Upper end of Aortic Pressure
86
What causes the characteristic 'Lubb' 'Dubb' sounds?
Closing of AV and Aortic valves respectively
87
What are the phases of the cardiac cycle?
- Atrial Contaction
- Isovolumetric Contraction
- Ventricular Ejection
- Isovolumetric Relaxation
- Atrial Filling
- Ventricular Filling
88
What is Cardiac output (CO)?
Amount of blood pumped by the heart per minute
89
What is heart rate (HR) ?
Number of beats per minute
90
What is stroke volume (SV)?
Amount of blood pumped per beat
91
What is the calculation for CO?
CO = HR * SV
92
What is significant about venous return?
It is the SAME as cardiac output
93
What is End-Diastolic Volume (EDV) ?
Volume of blood in ventricles just before systole.
| Relares to the length of sarcomeres in cardiac muscle prior to systole
94
What is End-systolic volume (ESV)?
Volume of blood in a ventricle and end of contraction.
| It is used clinically as a measurement of systolic function
95
How can you calculate Stroke Volume (SV)?
SV = EDV - ESV
96
What is Ejection Fraction (EF)?
This is the % of blood ejected from a ventricle with each heartbeat
97
How do you calculate Ejection Fraction (EF)?
EF = SV/EDV
98
What is the Frank-Starling Law?
Stroke volume (SV) of the heart increases in response to an increase in the volume of blood filling the heart when all other factors remain constant.
99
What helps regulate the heart rate?
Sympathetic stimulation can raise the heart rate to close to 200bpm
Vagal Stimulation can suppress the heart rate to 20bpm and also decrease strength of contraction
100
What can regulate the SAN?
Acetylcholine and Noradrenalin
101
How does Acetylcholine regulate the SAN?
It increases K+ permeability thus decreasing rate of spontaneous depolarisation
102
How does noradrenaline regulate the SAN?
Increases Na+/Ca2+ permeability thus increasing rate of spontaneous depolarisation
103
What is Resting membrane potential?
It is a voltage difference across the plasma membrane
104
What's the typical resting membrane potential in cardiomyocytes?
-90 to -80 mV
105
What is an action potential?
Change of voltage polarity across the plasma membrane
106
What molecules help form the typical cardiac membrane potential?
- Potassium Channels (K+) (Main)
- Sodium Channels (Na+)
- Calcium Channels (Ca2+)
- Chloride Channels (Cl-)
107
What is the major ion for membrane potential maintenance?
Potassium (K+)
108
What is Phase 4?
Resting membrane potential
109
What is Phase 0?
Depolarisation as Na+ starts to enter in abundance.
110
What is Phase 1?
Early Repolarisation,
K+ 'leak' through the membrane increases.
Inactivation of sodium channels
111
What is Phase 2?
The Plateau,
Ca2+ Channels activated increasing concentration inside the cell
K+ 'leak' still occurring
112
What is Phase 3?
Rapid Repolarisation,
Calcium Channels inactivated.
K+ leaving and Ca2+ absorption by organelles cause return to resting membrane potential
113
What is different about the action potential in pacemaking and contractile cardiac cells?
- In pacemaking cells they don't have a Phase 2 (Plateau).
- In Pacemaking cells the depolarisation is mainly caused by influx of Ca2+.
- The resting potential in pacemaking cells are - 60mV
114
What is the basic sequence of electrical events in the heart?
- SAN depolarises
- Waves of depolarisation spread across both atria
- AVN slows the signal from the atria to ventricles
- Wave of depolarisation spreads to the bundle of His
- Depolarisation spreads throughout the myocardium of the heart via the Purkinje fibres
- Once depolarisation has occurred depolarisation of the ventricles begin
115
What does the P wave represent?
Atrial depolarisation
116
What does the QRS complex represent?
Ventricular depolarisation
117
What does the T wave represent
Ventricular repolarisation
118
What does the U wave represent?
Papillary muscle repolarisation and repolarisation of the Purkinje fibres
119
What is the PR interval?
Start of the P wave to the start of the QRS complex
120
What is the QT interval?
Start of the QRS complex to the end of the T wave
121
What is the ST segment?
End of S wave to start of T wave
122
What two ways can you measure heart rate?
- Atrial Rate; frequency of P waves
| - Ventricular Rate; Measuring the RR interval
123
How do you calculate heart rate using RR interval?
- Measure the RR interval.
- Divide length by 5.
- Then divide 60 by this number
124
What artefacts could you have on the ECG?
Muscle Tremor
Sloping Baseline
Patient movement artefact
Alternating current interference
125
What is sinus bradycardia?
Slow heart rate
| - defined as under 60 BPM in adults
126
What is sinus tachycardia?
Heart rate exceeding normal resting rate
| - Above 100 BPM is accepted as tachycardia
127
What is Sinus arrhythmia?
Normal increase in heart rate during inspiration.
128
What is Atrial Fibrillation?
abnormal heart rhythm characterised by rapid and irregular beating.
No clear P waves
129
What is Atrial premature beat/ectopic?
Heart beat of atrial origin that occurs earlier than expected
early and abnormal p wave
130
What is ventricular premature beat/ ectopic?
Abnormal impulse originating from with the ventricle.
p waves not seen before ecotopic
no PR interval
QRS wide and bizarre
131
What is Ventricular tachycardia?
Usually defined as three or more ventricular beats with a heart rate greater than 120bpm
independent p wave activity
'fusion' of beats
132
What is ventricular fibrillation?
Impulse originates in one or more places in the ventricles at a very fast rate, resulting in uncoordinated activity in the ventricular muscle
p wave unrecognisable
PR interval absent
QRS absent
133
What is Asystole?
Also known as flatline, state of no electrical activity.
134
Atrial depolarisation is represented by?
P wave
135
Ventricular depolarisation is represented by?
QRS complex
136
Ventricular repolarisation is represented by?
T wave
137
What is Heart Failure?
A condition in which the heart can't pump enough blood to meet the body's needs.
138
What is congestive heart failure?
The heart cannot pump blood to the rest of the body with enough force
139
What are common risk factors for development of heart failure?
- Previous heart attacks
- Hypertension
- Heart Valve disease
- Heart muscle disease
- Congenital heart defects
- Alcohol/tobacco/drug use
140
What factors of cardiac output become abnormal in heart failure?
Contractility, Heart Rate, Afterload and Preload
141
What is the sequence of heart failure?
- Incapability to pump enough blood the maintain blood pressure
- Systemic vasoconstriction
- Reduced flow to Brain, Heart, Kidneys etc.
- Ischemic tissue damage
- Pain
- Death (if no adequate treatment)
142
What are direct causes of heart failure?
Heart Muscle and heart valves
143
What are indirect causes of heart failure?
Circulation - peripheral blood vessels
144
What is Hypertrophic cardiomyopathy?
Disease in which a portion of the myocardium in enlarged without any obvious cause
145
What are problems with hypertrophic cardiomyopathy ?
The hear can't fill with enough blood
146
What is dilated cardiomyopathy?
A condition in which the heart becomes enlarged
147
What are the problems with dilated cardiomyopathy?
The heart can't pump enough blood to the rest of the body with enough force
148
What two types of heart valve disease are there?
```
Valve stenosis (Narrowing)
Valve incompetence (leaky)
```
149
What are the problems with Valve stenosis?
If the valve does open fully it will obstruct the blood flow, this will put extra strain on the hear
150
What are the problems with valve incompetence?
It will allow blood to leak backwards
151
What is coronary circulation?
The circulation of the blood in the blood vessels of the heart muscle
152
What is hyperaemia?
Increase of blood flow to the tissue
153
What is active hyperaemia?
The increase in organ blood flow that is associated with increased metabolic activity of an organ or tissue
154
What is reactive hyperaemia
the transient increase in organ blood flow that occurs following a brief period of ischemia
155
What is ischemia?
Inadequate supply of blood to an organ or part of the body, especially the heart muscles
156
What is Atherosclerosis?
Hardening of the arteries due to plaque formation
157
What is Atheroma?
Degeneration of the walls of the arteries caused by accumulated fatty deposits and scar tissue
158
What are factors that may induce atherosclerosis?
Increased cholesterol in diet, cigarette smoking, obesity
159
What can atherosclerosis result in?
Ischemia and local necrosis
160
What is Coronary artery disease (CAD) sometimes known as?
Ischemic Heart Disease (IHD)
161
What diseases come under CAD and IHD?
Stable Angina, Unstable Angina, Myocardial infarction and sudden cardiac death
162
What fraction of 'natural' deaths involve IHD
1/3
163
What is Q-T syndrome?
Short and long Q-T syndromes are a condition associated with the dysfunction of depolarisation mechanisms of ventricular cardiomyocytes
164
What is defibrillation?
A treatment for life-threatening dysrhythmias.
165
What 3 methods are used to defibrillate the heart?
Physical: A blow depolarises the heart and allows sinus rhythm to be re-established
Electrical: Stimulus to depolarise and allow AVN to gain control
Chemical: Infusion of KCl to abolish fibrillation, wash out and AVN regains control
166
What does inotropy mean?
Change of the force of cardiomyocytes contraction
167
What does chronotropy mean?
Change of the heart rate
168
What does dromotropy mean?
Change in the conduction speed in AVN
169
What are sympathomimetics?
Increase of Inotropic, Chronotropic and Dromotropic effects
170
What are Parasympathomimetics?
Decrease of Inotropic, Chronotropic and Dromotropic effects?
171
What are examples of sympathomimetics?
Noradrenaline/Adrenaline
| Phenilephrine
172
What are examples of Parasympathomimetics?
Acetylcholine
| Oxotremorine
173
What are catecholamines?
The main neurotransmitters of the sympathetic nervous system
174
What are some examples go catecholamines?
Noradrenaline, Adrenaline, Dopamine
175
What is the main neurotransmitter of the parasympathetic nervous system?
Acetylcholine
176
What are the Parasympathetic (Vagal) regulations of the heart
- Acetylcholine
- Focal innervation of pacemakers, i.e SAN, AVN and Purkinje fibres
- Negative chrono/drono.
/inotropy
177
What are the sympathetic innervation of the heart?
- Noradrenaline
- Diffusive in the myocardium
- Positive chrono/dromo/inotropy
178
What are cardiac glycosides?
Compounds that increase the output force of the heart (+'ve inotropy) and decrease HR (-'ve chronotropy)
179
How do cardiac glycosides work?
They suppress the cellular Na+/K+ ATPase pump. THis increases Na+ concentration in the cell. In turn the cell exchanges this Na+ for Ca2+.
180
What are common cardiac glycosides?
Digitalis, digoxin and ouabain.
181
What is hyponatremia?
Low extracellular Na+
182
What can hyponatremia in the heart cause?
Increased cardiac contractility (inotropic effect)
Increases heart rate (chronotropic and dromotropic effect)
Increased coronary blood flow
183
What is hypernatremia?
High extracellular Na+
184
What can hypernatremia in the heart cause?
Decreased cardiac contractility (negative inotropic effect)
Decreases heart rate (negative chronotropic and dromotropic effect)
Decreased coronary and systemic blood flow
185
What is hyperkalaemia?
High extracellular K+
186
What can hyperkalaemia cause?
Decreased cardiac contractility (Negative inotropic effect)
Decreased heart beat (Negative corn and dronotropic effects)
Deceased coronary and systemic blood flow
187
What are clinically approved approaches to defibrillate the heart?
Electrical stimulus and physical blow
188
What is the action of cardiac glycosides?
Increase SV and decrease HR
189
What ionic conditions cause negative ino/dromo/chronotropic effects?
Hypernatremia, hyperkalaemia and hypocalcaemia
190
What ionic conditions cause positive ino/dromo/chronotropic effects?
Hyponatremia, hypokalaemia and hypercalcaemia
191
What is Blood Pressure?
The pressure of circulating blood on the walls of the blood vessels. It usually refers to the atrial pressure in the systemic circulation
192
How is blood pressure usually expressed?
In terms of systolic pressure over diastolic pressure (mmHg)
193
What is systolic pressure?
Maximum pressure during one heart beat
194
What is diastolic pressure?
Minimum pressure between two heart beats
195
What is the normal resting blood pressure?
120/80 mmHg
196
What are Korotkov sounds?
Created by pulsatile blood flow through the compressed artery
197
When can you hear Korotkov sounds?
When the cuff pressure is between 120/80 mmHg
198
What is turbulent flow?
Occurs with narrowing of arterial lumen
199
What are baroreceptors?
They are stretch receptors found in the carotid body, aortic body and the walls of large arteries in the neck and thorax
200
How do baroreceptors regulate blood pressure?
- Action potentials from the baroreceptors travel to the medullary cardiovascular control centre via sensory (afferent) neurons
- The CV control centre integrates the input and initiates an appropriate response
- Sympathetic or Parasympathetic autonomic neurons from the CV control centre target the Arterial Smooth muscle, Ventricular Myocardium or SAN.
201
Where is the CV control centre located?
In the medulla oblongata
202
Where does the parasympathetic output from the CV control centre target?
The SAN
203
Where does the sympathetic output from the CV control centre target?
The Arterial smooth muscle, ventricular myocardium and the SAN
204
How does the arterial smooth muscle control blood pressure?
Vasodilation can decrease peripheral resistance thus decreasing blood pressure
205
How does the ventricular myocardium control blood pressure?
The force of contraction can decrease, this lowers cardiac output and thus blood pressure
206
How does the SAN control blood pressure?
The SAN can lower heart rate, this reduces cardiac output and thus blood pressure
207
Blood pressure regulation is an example of...?
Negative Feedback
208
What is an example of long-term mechanism of blood pressure control?
The renin-angiotensin-aldosterone system
209
Where does the renin-angiotensin-aldosterone system begin?
In juxtaglomerular cells in the kidneys?
210
What do juxtaglomerular cells do?
Convert prorenin (in blood) to renin when renal blood flow is reduced.
211
What does renin do in the blood?
Converts angiotensinogen (released by liver) to angiotensin 1
212
What happens to angiotensin I in the lungs?
It is converted to angiotensin II by the ACE enzyme
213
What does angiotensin II do?
causes blood vessels to narrow and stimulates release of aldosterone from adrenal cortex and ADH in the post. pituitary
214
What does ADH and Aldosterone do?
Increases fluid retention and Na+ retention on the kidneys respectively
215
What is peripheral circulation?
It is a system of blood vessels that delivers and collects blood flow from the distal boundaries and contact surfaces of the body.
216
What are the contact surfaces of the body?
Skin, Alveolar Intestinal epithelium etc.
217
What are the functions of the peripheral circulation?
- Carries the blood
- Exchanges nutrients, waste products and gases
- Regulates blood pressure
- Directs blood flow from large arteries towards the tissues.
218
Peripheral circulation =?
All vessels of the body - Large Conduit vessels
219
What are the blood vessels of peripheral circulation?
Arterioles, Muscular Artery, Capillaries and Venules
220
What happens to peripheral circulation when oxygen levels are low?
It reduces pulmonary circulation but increases systemic.
221
Why does pulmonary circulation slow down in Hypoxic conditions?
- Slows down and redirects pulmonary circulation within the lungs
- Improves ventilation/perfusion ratio and arterial oxygenation
222
Why does systemic circulation speed up in hypoxic conditions?
- Increases systemic circulation
| - Facilitates diffusion and oxygen delivery to the tissues
223
What is the triple response of lewis?
A reaction to scratching of the skin
224
What are the steps of the triple response of lewis?
1) Red Reaction
2) Flare
3) Wheal
225
What is the red reaction?
A red line formed from local vasodilation and histamine and cytokine effect
226
What is the flare?
spreading redness beyond the redline (due to axon reflex)
227
What is the wheal?
Swelling/localised oedema in the region of the red line (appears white)
228
Where does the axon reflex in flare stage synapse?
In the dorsal root ganglion
229
What are histamines?
They are released by mast cells and basophils and are involved in local immune responses acting as a neurotransmitter
230
What is endothelium?
It is the largest endocrine organ formed of a thin layer of cells that line the interior surface of blood vessels and lymphatic vessels
231
What are vascular endothelial cells?
They are in direct contact with blood
232
What are common vasodilators for endothelia?
```
Nitric Oxide (NO)
Prostacyclin
```
233
What are common vasoconstrictors for endothelia?
Thromboxane, Angiotensisn II
234
What pathway do vasoconstrictors act on endothelium?
They increase the concentration of Ca2+
235
What are the main effects of NO in the body?
Reacts with DNA
Reduces blood cell aggregation
Reduces superoxide radicals
DILATES BLOOD VESSELS
236
How is NO generated in the vasculature?
Receptor-stimulated NO formation
| Flow-dependent NO formation
237
Outline how NO dilate blood vessels?
- Hyperpolarisation occurs through stimulation of K+ channels
- The concentration of Ca2+ is reduced in the cell
- As there is less Ca2+ it cannot stimulate contractile apparatus
238
What is the role of the cardiovascular centre (CV centre)?
It regulates HR and SV
| It also regulates vasodilation/constriction
239
Where does the CV centre receive signals from?
- Cerebral cortex, limbic system and hypothalamus
- Chemoreceptors
- Baroreceptors
240
What is somatic sensation?
Touch, pain, pressure, temperature etc.
241
What is visceral sensation?
Stretch, pain, chemical sensitivity, hunger, nausea
242
What are the main neurotransmitters of the sympathetic nervous system?
Catecholamines (adrenaline, noradrenaline, dopamine)
243
How do catecholamines increase contractility in cardiomyocytes?
- They stimulate β adrenoreceptors
- This activates a Gs coupled receptor which in turn stimulates SERCA.
- This has a positive ino/chronotropic effect increasing contractility
244
What is the main neurotransmitter of the parasympathetic nervous system?
Acetylcholine
245
How does acetylcholine reduce contractility in cardiomyocytes?
- They stimulate a M2 cholinoreceptor
- This activates a Gi couple receptor which in turn will inhibit SERCA
- This has a negative chrono/inotropic effect reducing contractility
246
How do catecholamines stimulate vasoconstriction?
They stimulate α adrenoreceptors
- This activates Gq coupled receptors which in turn will stimulate Ca2+ release from the sarcoplasmic reticulum
- This stimulates vasoconstriction
247
What is the effect of Angiotensin II on vasculature?
It triggers vasoconstriction
248
How does acetylcholine effect on smooth muscle cells?
It triggers vasodilation
249
How do postural changes affect circulation?
When standing blood pools in leg veins
When lying down blood is more evenly distributed, this increases central venous pressure, diastolic volume and stroke volume.
This in turn will increase pulse pressure
250
What is venous return (VR)?
It is the volume o blood that returns to the right atrium
251
What mechanisms are responsible for regulation of venous return?
```
Skeletal muscle pump
Respiratory pump
Cardiac suction effect
Venous valves
Sympathetic constriction of venous smooth muscles
```
252
What is the respiratory pump?
The diaphragm contacts so the thoracic cavity volume increases.
Lungs pressure drops and abdominal pressure increases.
Blood moves from higher pressure to lower pressure
253
How do skeletal muscles work as a peristaltic pump?
When the calf muscles contract they pump blood up towards thorax, the venous valves prevent backflow.
254
What class of enzymes generate endogenous Nitric Oxide?
NO-synthases
255
What is the effect of phospholamban phosphorylation in cardiomyocytes?
Contractility Increases
256
How does lying down influence stroke volume?
Increases
257
What is the nature of transient orthostatic hypotension?
Delayed vasoconstriction of peripheral systemic arteries
258
What are the branches of the ascending aorta ?
intercostal arteries
259
What are the branches of the aortic arch?
on the right side - braciocephalic trunk - right common carotid and right subclavian
on the left side - left common carotid and left subclavian
260
What is the braciocephalic vein formed from ?
the subclavian and internal jugular veins
261
What are the branches of the descending aorta ?
intercostal arteries
bronchial arteries
oesophageal arteries
262
What mechanisms exist to ensure blood flows in the correct direction through the heart ?
the right and left atrioventricualr bundles
pulmonary and aortic valves
aided by the chordae tendinae and the papillary muscles
263
What are the features of the right atrium ?
fossa ovalis
crista terminalis
muscuale pectini
264
What are the 3 surfaces of the heart ?
sternocostal
diaphragmatic
posterior
265
What forms most of the anterior surface of the heart ?
right atrium
right ventricle
some left ventricle
266
What forms the posterior surface of the heart ?
left atrium
left ventricle
right atrium
right ventricle
267
What are the atrial and ventricular septa of the heart ?
septa maintain muscular continuity - syncytium
| gap junctions allow impulses between the corresponding chamber
268
What is the atrioventricular septum ?
fibrous skeleton between the atria and the ventricles
no muscular continuity or syncytium
electrically isolates the ventricles from the atrium
269
What are the 2 grooves on the heart ?
anterior atrioventricular groove - between the atria and the ventricles
anterior interventricular groove - between the ventricles
270
What is the crista terminalis ?
between the sup and inf vena cava
| separates the right atrium into a smooth posterior walls and a rough anterior wall
271
What are the musculi pectini ?
radiate from right angles from the crista terminalis
| help to channel blood flow
272
What is the fossa ovalis ?
oval depression in the right atrium - embryonic development shunt
273
Where is the SAN ?
just below the superior vena cava
274
Where is the AVN ?
Just above the coronary sinus
275
What are the trabeculae carnae ?
ridges in the right ventricle
276
What are the chordae tendinae ?
join the tricuspid valve to the papillary muscle
277
What is the mediastinum ?
central component of the thoracic cavity - divides into the right and left pulmonary cavities
278
How is the mediastinum divided ?
by the sternal angle into the superior and inferior mediastinum
279
What are the divisions of the inferior mediastinum ?
anterior , middle and posterior relative to the pericardium
280
What is the contents of the anterior superior mediastinum ?
```
sternothyroid
sternohyoid
thymus gland
superior vena cava
braciocephalic vein
```
281
How is the braciocephalic vein formed ?
union of the internal jugular and the subclavian
282
What is the contents of the middle superior mediastinum ?
```
aortic arch
braciocephalic trunk
left common carotid and left subclavian arteries
vagus nerve
phrenic nerve
```
283
Where does the right recurrent laryngeal nerve form ?
at the level of the subclavian artery
284
Where does the left recurrent laryngeal nerve form ?
at the aortic arch
285
What are the contents of the posterior superior mediastinum ?
oesophagus
| thoracic duct
286
What is the pathway of electrical impulses from the SAN ?
Heartbeat initiated
passes to the AVN from the atrial walls
passes to the bundle of His
branches into the right and left aAV bundles
purkinje fibres take to the venricualr walls
287
What are the 1st branches of the ascending aorta ?
the right and left coronary arteries
288
Where does the right coronary artery run ?
in the anterior atrioventricular groove
289
What are the branches of the right coronary artery ?
marginal artery
| posterior interventricular artery
290
What are the branches of the left coronary artery ?
anterior interventricular
| circumflex artery
291
What drains into the coronary sinus ?
70% of cardiac venous blood
great cardiac vein
middle cardiac vein
anterior cardiac vein drains into the right atrium directly
292
How is contraction initiated in cardiomyocytes ?
Na channels open
L-type Ca channels open
calcium release from RyR
stimulation of concractile apparatus
293
How is relaxation initiated in cardiomyocytes ?
Calcium uptake by the SR
exchange - calcium out and 3 Na in
Na/K ATPase - 2K in and 3Na out
294
What does phospholamban do ?
inhibits SERCA in the unphosphorylated state
295
How is SERCA activated through phospholamban ?
phosphorylate phospholamban using cAMP depdnent protein kinase A
296
What is pulse pressure ?
systolic pressure - diastolic pressure
297
How do you work out mean arterial pressure?
diastolic pressure + 1/3 pulse pressure
298
What is isovolumetric contraction ?
contraction of the left ventricle means the pressure in the LV is greater than the pressure in the LA - bicuspid valve shuts
Pressure is the less than aortic pressure so the aortic valve is shut
volume is constant but the pressure is increasing
299
What is isovolumetric relaxation ?
relaxation of the LV means that pressure in the LV is falling so the aortic valve shuts
the pressure in the LV is still higher than the LA so the bicuspid valve is shut
pressure is falling but volume is increasing
300
What is cardiac ouTput ?
amount of blood pumped by the heart in a minute
301
What is the heart rate ?
beats per minute
302
What is stroke volume ?
amount of blood pumped per beat
303
What is the EDV ?
end diastolic volume
| amount of blood in the left/right ventricle before systole
304
What is ESV ?
end systolic volume
| amount of blood at the end of contraction
305
How do you work out Stroke volume ?
EDV-ESV
306
What is ejection fraction ?
fraction if blood ejected from the ventricle per beat
| SV/EDV
307
Which valves are open in ventricular systole ?
pulmonary and aortic valves
308
What shows ventricukar diastole in the ECG ?
flatline following the T wave
309
Are there more veins or arteries in the body ?
veins
310
In which phase of the cardiac cycle does most of the blood enter the ventricles ?
atrial diastole
311
What is bradycardia ?
decreased HR
312
which parameter in Pioseuilles law varies physiologically to influence flow rate ?
radius
313
Which connecting structures are present in cardiac intercalated discs ?
desmosomes and gap junctions
314
What does the ECG l;ook like for atrial fibrilation ?
unclear or absent T wave
315
What is the maximal efficinecy of the heart ?
20-25%
316
What type of failure is hypertrophic cardiomyopathy ?
systolic failure
317
What are the components of the peripheral circulation ?
```
resistance arteries
arterioles
capillaries
venules
veins
```
318
Which division of the mediastinum is the heart within ?
middle division of the inferior mediastinum
319
How is the pulsatile flow of the blood from the heart converted into continuous flow ?
Energy of the heart beat is stored in the elasticity of the arterial walls and this is released during dyastole and converts the pulsatile flow into continuous flow by reducing pulse pressure
320
What are the contents of the superior mediastinum ?
```
thymus gland
sternohyoid and sternothyroid
phrenic
vagus
aortic arch
thoracic duct
trachea
oesophagus
braciocephalic vein
```
