Cardiovascular Principles Flashcards
1
Q
What is an electrically controlled muscular pump which sucks and pumps blood?
A
The heart
2
Q
Where are the electrical signals which control the heart generated?
A
Within the heart itself
3
Q
What is the term used to describe the hearts capability of beating rhythmically in the absence of external stimuli?
A
Autorhythmicity
4
Q
Where does excitation of the heart normally originate?
A
In the pacemaker cells in the sino-atrial node
5
Q
What cluster of cells in the SA node initiate the heart beat?
A
Specialised pacemaker cells
6
Q
Where is the SA node located?
A
In the right upper atrium, close to where the superior vena cava enters the right atrium
7
Q
What is a heart controlled by the SA node said to be in?
A
Sinus rhythm
8
Q
Do cells in the SA node have a stable resting membrane potential?
A
No
9
Q
What do cells in the SA node exhibit?
A
Spontaneous pacemaker potential
10
Q
What takes the membrane potential to a threshold to generate action potential in the SA nodal cells?
A
Pace maker potential
11
Q
What is the threshold of an SA node cell?
A
-40 mV
12
Q
What is the permeability to K+ in pacemaker cells like between action potentials?
A
Not constant
13
Q
What is - the slow depolarisation of membrane potential to a threshold?
A
The pacemaker potential
14
Q
What is the pacemaker potential due to?
A
Decrease in K+ efflux superimposed on a slow Na+ influx (the funny current)
15
Q
Once the threshold for SA nodal cells has been reached, what is the rising phase of the action potential (i.e. depolarisation) caused by?
A
Activation of voltage-gated calcium channels
Ca influx
16
Q
In the ionic basis for pacemaker action potential: what causes the falling phase of the action potential (i.e. repolarisation)?
A
Activation of K+ channels, resulting in K+ efflux
17
Q
How does the SA node excitation spread to teh AV node?
A
By cell-cell conduction
18
Q
Where does the SA node excitation spread to after the AV node?
A
Bundle of His
Left and right branches
Purkinje fibers
19
Q
What does cell-cell spread of excitation occur via?
A
Gap junctions
20
Q
What is a small bundle of cardiac cells?
A
AV node
21
Q
Where is the AV node located?
A
At the base of the right atrium; just above the junction of atria and ventricles
22
Q
Where is the only point of electrical contact between the atria and ventricles?
A
AV node
23
Q
What cells are small in diameter and have slow conduction velocity?
A
AV node cells
24
Q
How does spread of excitation occur across the atria?
A
Mainly cell-cell conduction, via gap junctions
25
Where is the conduction in the heart delayed?
At the AV node
26
What does the delay of conduction in the AV node allow?
Atrial systole to precede ventricular systole
27
What allows rapid spread of action potential to the ventricles?
Bundle of His and Purkinje fibres
28
Is the contractle cardiac muscle cell action potential different from the action potential in pacemaker cells?
Yes
29
In ventricular muscle cells what does the resting membrane potential remain at before excited?
-90 mV
30
In ventricular muscle cells: what is the rising phase of action potential (i.e. depolarisation) caused by?
Fast Na+ influx
31
In ventricular muscle cells: what does the fast Na+ influx reverse?
The membrane potential to +30
32
What is known as Phase 0 of action potential in contractile cardiac muscle cells?
The depolarisation of action potential by fast Na+ influx, reversing the membrane potential from -90 to +30
33
What occurs in phase 1 of contractile cardiac muscle cell action potential?
Closure of Na+ channels and transient K+ efflux
34
What occurs in phase 2 of contractile cardiac muscle cells action potential?
Mainly Calcium influx
35
What occurs in phase 3 of contractile cardiac muscle cell action potential?
Closure of calcium channels and K+ efflux
36
What occurs in phase 4 of contractile cardiac muscle cell action potential?
Resting membrane potential
37
What is the phase called of ventricular muscle action potential, where the membrane potential is maintained near the peak of action potential for a few hundred seconds?
The plateau phase of action potential
38
What is a unique characteristic of contractile cardiac muscle cells?
The Plateau phase
39
What is the plateau phase due to?
Influx of calcium through voltage gated calcium channels
40
What causes the falling phase of action potential (i..e. repolarisation) in ventricular muscle action potential?
Inactivation of Ca channels and activation of K+ channels, resulting in K+ efflux
41
What is the heart rate mainly influenced by?
The autonomic nervous system
42
What stimulation increases the heart rate?
Sympathetic
43
What stimulation decreases the heart rate
Parasympathetic
44
What gives parasympathetic supply to the heart?
The vagus nerve
45
What exerts a continuous influence on the SA node under resting conditions?
The vagus nerve
46
What dominates under resting conditions?
The vagal tone
47
What does the vagal tone do?
Slows the intrinsic heart rate from ~100bpm to produce a normal resting heart rate of ~70 bpm.
48
What is considered to be a normal resting heart rate?
60 to 100 bpm
49
What is a resting heart rate of
Bradycardia
50
What is a resting heart rate of more than 100bpm said to be?
Tachycardia
51
What supplies the SA node and AV node?
Vagus nerve
52
What does vagal stimulation do?
Slows the heart rate and increases AV nodal delay
53
What does parasympathetic neurotransmitter acetyl choline act through?
M2 receptor
54
What is a competitive inhibitor of acetylcholine and what is it used in?
Atropine
| Used in extreme bradycardia to speed up the heart
55
What are the 5 effects of vagal stimulation on pacemaker potentials?
1. Cell hyperpolarises
2. Longer to reach threshold
3. Slope of pacemaker potential decreases
4. Frequency of AP decreases
5. Negative chronotropic effect
56
What 3 things does the cardiac sympathetic nerve supply?
1. SA node
2. AV node
3. Myocardium
57
What increases the force of contraction?
Sympathetic stimulation
58
What is the sympathetic neurotransmitter and what does it act through?
Noradrenaline acting through B1 adrenoceptors
59
What are the 3 effects of noradrenaline on pacemaker cells?
1. Slope of pacemaker potential increases
2. Pacemaker potential reaches threshold quicker
3. Frequency of action potentials increases - positive chronotropic effect
60
What do the surface electrodes on an ECG detect?
Waves of depolarisation and repolarisation moving across the heart and setting up electrical currents
61
What is ECG lead I?
RA - LA
62
What is ECG lead II?
RA - LL
63
What is ECG lead III?
LA - LL
64
What does the P wave represent?
Atrial depolarisation
65
What does the QRS complex represent?
Ventricular depolarisation (masks atrial repolarisation)
66
What does the T wave represent?
Ventricular repolarisation
67
What does the PR interval represent?
Largely AV node delay
68
What does the ST segment represent?
Ventricular systole
69
What does the TP interval represent?
Diastole
70
What type of fibre pattern does cardiac muscle have?
Striated
71
What is cardiac muscle striation caused by?
Regular arrangmenet of contractile protein
72
What are cardiomyocytes electrically coupled by?
Gap junction
73
What is the term for protein channels which form low resistance electrical communication pathways between meighbouring myocytes?
Gap junctions
74
What do the desmosomes within the intercalated discs of cells provide?
Mechanical adhesion between adjacent cardiac cells
75
How is tension developed by one cardiac myocyte transmitted to the next?
By desmosomes
76
What does each muscle fibre contain many of?
Myofibrils (contractile units of muscle)
77
What do myofibrils have alternating segments of?
Thick and thin protein filaments
78
What causes the lighter appearance in myofibrils and fibers?
Actin (thin filament)
79
What causes the darker appearance in myofibrils and fibers?
Myocyin (thick filaments)
80
Within each myofibril, what are actin and myocin arranged into?
Sacromeres
81
How is muscle tension produced?
By sliding of actin filaments on myocin filaments
82
What does force generation depend on?
ATP-dependent interaction between thick (myosin) and thin (actin) filaments
83
What is required for both contraciton and relaxation?
ATP
84
What is required to switch on cross bridge formation?
Calcium ions
85
In an excited cell state, what has occured between troponin and actin binding site?
Binding
86
Where is calcium released from?
The sarcoplasmic reticulum
87
In cardiac muscle, what is the relase of calcium from SR dependent on?
Presence of extra-cellular calcium
88
In relation to systole, when the action potential has passed - what occurs?
Calcium influx ceases, calcium is re-sequestered in SR by calciumATPase and the heart muscle relaxes
89
When the cardiac muscle fibre is relaxed, why is there no cross-bridge binding?
Because the cross-bridge binding site on actin is physically covered by the troponin-tropomyosin complex
90
What triggers powerstroke and pulls thin filament inward during contraction?
Binding of actin and muosin cross bridge
91
When the muscle fiber is excited, what occurs when calcium binds with troponin?
It pulls troponin-tropomyosin complex aside to expose cross-bridge binding site, then cross-bridge binding occurs
92
What does the long refractory period prevent?
Generation of tetanic contracion
93
What is the refractory period?
The period following an action potential in which it is not possible to produce another action potential.
94
During the plateau phase of ventricular action potential what are the Na channels like?
In a depolarised, closed state (i.e. not available for opening)
95
During the descending phase of action potential, the K+ channels are open - what cant the membrane do?
Be depolarised
96
What ejects the stroke volume?
Contraction of ventricular muscle
97
What is the stroke volume defined as?
The volume of blood ejected by each ventricle per heart beat.
98
What is an equation for stroke volum?
EDV - ESV (end diastolic volume - end systolic volume)
99
What brings about changes in stroke volume?
Changes in the diastolic length of myocardial fibers
100
What is the diastolic length of myocardial dibers determined by?
The volume of blood within each ventricle at the end of diastole. This is called end diastolic volume.
101
What does end diastolic volume determine?
Preload
102
What is the end diastolic volume determined by?
Venous return to the heart
103
What describes the relationship between venous return, end diastolic volume and stroke volume?
The Frank-Starling mechanism
104
What states that "the more the ventricle is filled with blood during diastole (EDV), the greater the volume of ejected blood will be during the resulting systolic contraction (stroke volume)?
Frank-Starling Curve
105
What does stretch also increase?
The affinity of troponin for calcium
106
What is optimal length in cardiac muscle achieved by?
Stretching the muscle (Frank-Starling mechanism)
107
What happens when venous return to the right atrium increases?
EDV of right ventricle increases
108
What does Starling's law lead to?
Increased SV into pulmonmary artery
| Increased SV into aorta
109
Whta does venous return to left atrium from pulmonary vein increase?
EDV of left ventricle
110
What does hte Frank-Starling mechanism partially compensate for?
Decreased stroke volume caused by increased afterload
111
What is afterload?
The resistance into which the heart is pumping
The extra load is imposed after the heart has contracted
112
What condition is there incrwased afterload continuously?
Hypertension
113
What does increased afterload eventually lead to?
Ventricular hypertrophy
114
What does extrinisc control of stroke volume involve?
Nerves and hormones
115
What kind of effect is increasing the force of contraction, and what effect is increasing the heart rate?
Positive inotropic
| Positive chronotropic
116
What is the force of contraction effect mediated by?
cAMP
117
During sympathetic stimulation, what happens to the ventricular pressure?
Rises
118
What does the increased rate of pressure change during systole, as a result of peak ventricular pressure rising reduce?
Duration of systole
119
When the peak ventricular pressure rises and the contractility of the heart at a given EDV rises, what happens to the Frank-Starling curve?
It is shifted to the left
120
Where does heart failure shift the FS curve to?
The right
121
What is cardiac output?
The volume of blood pumped by each ventricle per minute.
122
What is the equation for CO?
SV x HR
123
What is the resting CO in a healthy adult normally?
5 litres per minute (70 ml SV x 70 bpm = 4900 ml CO)
124
Do heart valves produce a sound when they shut and open?
Only a sound is heard when they shut
125
What does the orderly depolarisation/repolarisation sequence trigger?
A recurring cardiac cycle of atrial and ventricular contractions and relaxations
126
What does the cardiac cycle refer to?
All events that occur from the beginning of one heart beat to the beginning of the next
127
What is the term for the stage where the heart ventricles are relaxed and fill with blood?
Diastole
128
What stage occurs where the heart ventricles contract and pump blood into the aorta (LV) and pulmonary artery (RV)?
Systole
129
At a heart rate of 75 bpm; how long is ventricular diastole and how long is ventricular systole?
Diastole 0.5 sec
| Systole 0.3 sec
130
What are the five events that occur during the cardiac cycle?
1. Passive filling
2. Atrial contraction
3. Isovolumetric ventricular contraction
4. Ventricular ejection
5. Isovolumetric ventricular relaxation
131
During passive filling, what happens to the pressure in the atria and ventricles?
Close to 0
132
During passive filling, why do AV valves open?
So venous return flows into the ventricles
133
During passive filling, once the AV valve has opened and venous return flowed into the ventricles, what happens to the aortic pressure and valve?
Aortic pressure ~80 mmHg and aortic valve is closed
134
During passive filling, similar events happen in the right side of the heart - however what can be said about the pressures (RV and PA)?
Much lower
135
How full do ventricles become by passive filling?
80% full
136
What occurs between the P-wave and the QRS?
Atria contracts
137
What is the EDV in resting normal adults, after atrial contraction?
130ml
138
During isovolumetric ventricular contraction, when does ventricular contraction start?
After the QRS signals ventricular depolarisation in the ECG
139
During isovolumetric ventricular contraction, what occurs after the ventricular contraction has started?
Ventricular pressure rises
140
During isovolumetric ventricular contraction, what happens once the ventricular pressure exceeds atrial pressure?
The AV valves shut
141
What produces the first heart sound (LUB)?
The AV valve shutting
142
During isovolumetric ventricular contraction, after the first heard sound what is the aortic valve doing?
Still shut, so no blood can enter or leave the ventricle
143
What is isovolumetric contraction?
The tension rising around a closed volume
144
During ventricular ejection, what occurs when the ventricular pressure exceeds aorta/pulmonary artery pressure?
Aortic/pulmonary valve opens
145
During ventricular ejection, once the aortic/pulmonary valves have opened - what occurs?
Stroke volume is ejected by each ventricle leaving behind the end systolic volume (ESV)
146
What is the equation for SV (stroke volume), with values added?
SV = EDV - ESV
135 - 65
= 70ml
147
During ventricular ejection, once the SV has been ejected what happens to the aortic pressure?
Rises
148
What does the T wave in the ECG represent?
Ventricular repolarisation
149
What starts to occur during ventricular repolarisation?
The ventricles relax and ventricular pressure starts to fall
150
During ventricular ejection, what occurs when the ventricular pressure falls below aortic/pulmonary pressure?
Aortic/pulmonary valves shut
151
What produces the second heart sound (DUB)?
When the ventricular pressure falls below aortic/pulmonary pressure: aortic and pulmonary valves shut
152
During ventricular ejection, what produces the dicrotic notch in the aortic pressure curve?
The valve vibration produces the dicrotic notch
153
What signals the start of isovolumetric ventricular relaxation?
Closure of aortic/and pulmonary valves
154
What is "isovolumetric relaxation"?
The tension falls around a closed volume
155
During isovolumetric ventricular relaxation, what occurs when the ventricular pressure falls below atrial pressure?
AV valve open and the heart starts a new cycle
156
What does the closure of mitral and tricuspid valves cause?
First heart sound (S1)
157
What does S1 herald?
The beginning of systole
158
What does the closure of aortic and pulmonary valves cause?
The second heart sound (S2)
159
What does S2 hearald?
The end of systole and beginning of diastole
160
Is S3 diastolic or systolic?
S3 is diastolic
161
Where does S4 occur?
Just before S1
162
What does JVP occur after?
Right atrial pressure waves
163
JVP - what does "a" stand for?
Atrial contraction
164
JVP - what does "c" stand for?
Bulging of tricuspid valve into atrium during ventricualr contraction
165
JVP - what does "v" stand for?
Rise of atrial pressure during atrial filling: release as AV valves open
166
What is the outwards (hydrostatic) pressure exerted by the blood on blood vessel walls?
Blood pressure
167
What is the systemic systolic arterial blood pressure?
The pressure exerted by the blood on the walls of the aorta and systemic arteeries when the heart contracts.
168
What should systolic BP not exceed under resting conditions?
140 mmHg
169
What is systemic diastolic arterial blood pressure?
The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxe
170
What should siastolic arterial blood pressure not exceed under resting conditions?
90 mmHg
171
How does blood flow in normal arteries?
In a laminar fashion
172
Can you hear laminar blood flow through a stethoscope?
No
173
If external pressure (e.g. cuff pressure) exceeding the systolic blood pressure is applied to an artery, what happens to the flow and sound of that artery?
The flow in that artery would be blocked and no sound is heard through a stethoscope.
174
If external pressure is kept between systolic and diastolic pressure, what happens to the flow?
It becomes turbulent whenever blood pressure exceeds cuff pressure
175
When is the first Korotkoff sound heard?
At peak systolic pressure
176
When is the 2 - 3 Korotkoff sounds heard?
As blood pressure due to turbulent spurts of flow cyclically exceeds cuff pressure
177
When is the 4th Korotkoff sound heard?
The last sound is heard at minimum/diastolic pressure (muffled/muted sound)
178
Which Korotkoff sound is this - no sound is heard thereafter because of uninterurupted, smooth, laminar flow?
5th
179
When is diastolic pressure recorded?
At the 5th Korotkoff sound (point at which sound disappears) - more reproducible
180
The RA pressure is close to 0, so what is the main driving force for blood?
MAP
181
What - between the aorta and right atrium - drives the blood around the systemic circulation?
A pressure gradient
182
What does MAP - Central venous (right atrial) pressure =?
Pressure gradient
183
What is MAP?
The average arterial blood pressure during a single cardiac cycle
184
Formula for estimating MAP?
[(2 x diastolic pressure) + systolic pressure] / 3
185
What is the second method of estimating MAP?
MAP = DBP +1/3 (difference between SBP and DPB)
186
What is normal range of MAP?
70 - 105 mm Hg
187
What does CO x TPR =?
MAP
188
What is the volume of blood pumped by each ventricle of the heart per minute?
co
189
What does SV x HR =?
CO
190
What is the volume of blood pumped by each ventricle per heart beat?
Stroke volume
191
What is total peripheral resistance?
The sum of resistance of all peripheral vasculature in the systemic circulation
192
What are the major resistance vessels?
Arterioles
193
What does parasympathetic stimulation do to MAP?
Lowers it
194
What does sympathetic stimulation do to arterioles, TPR and MAP?
Increases vasoconstriction
Increases TPR
Increases MAP
195
What does sympathetic stimulation do to veins?
```
Increases vasoconstriction
Increases venous return
Increases SV
Increases CO
Increases MAP
```
196
What gives short-term regulation of MAP?
The baroreceptor reflex
197
Where are the two groups of baroreceptors located?
1. Aortic arch
| 2. Carotid sinus
198
How do the carotid baroreceptors signal to the medulla?
Via the IXth CN
199
How do the aortic baroreceptors signal to the medulla?
Via the Xth CN
200
When MAP is low, what happens to carotid sinus afferent nerve fibres firing, cardiac vagal efferent nerve fibres activity, cardiac sympathetic efferent nerve fibres activity and sympathetic vasoconstrictor nerve fibres activity?
Carotid sinus afferent nerve fibres firing - decrease
Cardiac vagal efferent nerve fibres activity - decrease
Cardiac sympathetic efferent nerve fibres activity - increase
Sympathetic vasoconstrictor nerve fibres activity - increase
201
What happens to the venous return to the heart when a normal person stands up suddenly?
Decreases - effect of gravity
202
When the venous return to the heart decreases what happens to the MAP?
Transient decrease
203
When there is a transient decrease in MAP, what happens to rate of firing of baroreceptors?
Decrease
204
When the rate of firing of baroreceptors is reduced, what happens to the vagal tone and sympathetic tone, and what results does this give?
Vagal tone to heart decreases
Sympathetic tone to heart increases
This increases the HR and SV
205
What does sympathetic constrictor tone to the veins increase?
The venous return to the heart and the stroke volume
206
What does postural hypotension result from?
Failure of baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position.
207
What only responds to actue changes in blood pressure?
Baroreceptors
208
What happens to the baroreceptor firing when high blood pressure is sustained?
Decreased
209
What can baroreceptors not supply information about?
Prevailing steady state blood pressure
210
What can be controlled by controlling the extracellular fluid volume?
Blood volume and MAP
211
How much body weight in a 70kg man is water?
60% (42 L)
212
What does total body fluid = ?
Intracellular fluid (2/3rd) + extracellular fluid (1/3rd of total)
213
What does ECF Volume (ECFV) = ?
Plasma volume (PV) + interstitial fluid volume (IFV)
214
What fluid bathes the cells and acts as the go-between the blood and body cells?
ECFV
215
If plasma volume falls, what does the compensatory mechanism do?
Shifts fluid from the intestitial compertment to the plasma compartment
216
What are the two main factors affecting extracellular fluid volume?
1. Water excess or deficit
| 2. Na+ excess or deficit
217
How do hormones act as effectors to regulate the extracellular fluid volume (including PV)?
By regulating the water and salt balance in our bodies
218
Name three hormones which regulate extracellular fluid volume?
1. The Renin-Angiotensin-Aldosterone system (RAAS)
2. Atrial Natriuretic Peptide (ANP)
3. Antidiuretic Hormone (Arginine Vasopressin) - ADH
219
What system plays an important role in the regulation of plasma volume and TPR and hence the regulation of MAP?
The Renin-Angiotensin-Aldosterone System
220
What are the three components of the Renin-Angiotensin-Aldosterone System?
1. Renin
2. Angiotensin
3. Aldosterone
221
Where is renin released from and what does it stimulate?
Renin is released from the kidneys and stimulates the formation of angiotensin I in the blood from angiotensinogen (produced by the liver)
222
What converts Angiotensin I to angiotensin II?
Angiotensin converting enzyme (ACE)
223
Where is angiotensin converting enzyme (ACE) produced?
By pulmonary vascular endothelium
224
What does Angiotensin II stimulate the release of?
Aldosterone from the adrenal cortex
225
What two things does aldosterone from the adrenal cortex cause?
1. Systemic vasoconstriction - increases TPR
| 2. Stimulates thirst and ADH release (contributes to plasma volume mainly brought about by aldosterone)
226
What type of hormone is aldosterone?
A steroid hormone
227
What results from aldosterone acting on the kidneys?
Increase in sodium and water retention which increases plasma volume
228
When plasma volume decreases, and then BP decreases - what does the kidney release?
Renin
229
Once renin has been released from the kidney, what does it convert?
Angiotensinogen from liver to angiotensin I
230
Once angiotensin I has converted to angiotensin II by ACE, where does angiotensin II stimulate and cause the release of?
Adrenal cortex
| Release aldosterone which increases PV + BP, increases sodium and water reabsoprtion in kidneys
231
Give three effects of angiotensin II, other than stimulating the adrenal cortex?
1. Vasoconstriction (increased TPR & BP)
2. Increased ADH release (increased PV & BP)
3. Increased thirst
232
What is the rate limiting step for RAAS?
Renin secretion
233
Where exactly in the kidney is renin released from?
Juxtaglomerular apparatus - from GRANULAR CELLS
234
What are the three mechanisms which regulate RAAS by stimulating renin release?
1. Renal artery hypotension - caused by systemic hypotension
2. Stimulaton of renal sympathetic nerves
3. Decreased [Na+] in renal tubular fluid
235
What senses the decreased [Na+] in renal tubular fluid?
Macula densa (specialised cells of kidney tubules)
236
What three components is the juxtaglomerular apparatus made from?
1. Macula densa
2. Extraglomerular mesangial cells
3. Granular cells
237
What is Atrial Netriuretic Peptide (ANP) and what is it composed of/stored by?
28 amino acid peptide synthesised and stored by atrial muscle cells (atrial myocytes)
238
What is ANP released in response to?
Atrial distension (hypervolaemic states)
239
How does the release of ANP reduce blood volume and blood pressure?
By causing excretion of salt and water in the kidneys
240
What does ANP act as to reduce blood pressure?
Vasodilator
241
What does ANP do to renin release?
Decreases renin release
242
What acts as a counter-regulatory mechanism for the Renin-Angiotensin-Aldosterone System (RAAS)?
Atrial Netriuretic Peptide (ANP)
243
What is ADH also called?
Vasopressin
244
What is a peptide hormone derived from a prehormone precursor synthesised by the hypothalamus and stored in the posterior pituitary?
ADH
245
Where is ADH synthesised and stored?
Synthesised by the hypothalamus and stored in the posterior pituitary
246
What two things stimulates secretion of ADH?
1. Reduced extracellular fluid volume
| 2. Increased extracellular fluid osmolarity
247
What is the normal osmolarity of extracellular fluid?
280 milli-osmoles/l
248
What monitors plasma osmorality?
Osmoreceptors mainly in the brain in close proximity to the hypothalamius
249
What does increased plasma osmolality stimulate?
The release of ADH
250
What does ADH act on to increase the reabsorption of water? (i.e. concentrate urine (antidiuresis)?
Kidney tubules
251
When ADH acts in the kidney tubules to increase the reabsorption of water - what would this also increase?
Extracellular and plasma volume and hence cardiac output and blood pressure
252
What does ADH also act on to cause vasoconstriction?
Blood vessels
253
What effect is small but becomes important in hypovolaemic shock (e.g. haemorrhage)?
ADH causing vasoconstriction, increasing TPR and BP
254
What does long term regulation of MAP involve control of?
Blood volume by hormones
255
What regulates ECF (including PV) volume and osmolality to deal with fluid loads/deficits?
ADH
256
What regulates total body Na+ and with it ECF volume in the longer term?
Aldosterone
257
What are the capacitance vessels?
Veins
258
What is resistance to blood flow directly proportional to and inversely proportional to?
Directly proportional to blood viscosity and length of blood vessel
Inversely proportional to the radius of blood vessel to the power 4
259
How is the resistance to blood flow mainly controlled?
By vascular smooth muscles through changes in the radius of arterioles
260
What does extrnisc control of vascular smooth muscle involve?
Hormones and nerves
261
What nerves are vascular smooth muscles supplied by and what is the neurotransmitter?
Sympathetic nerves
| Noradrenaline acting on alpha receptors
262
What is the term for vascular smooth muscles partially constricted at rest?
Vasomotor tone
263
What is the vasomotor tone caused by?
Tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline.
264
Where is there the only parasympathetic innervation of arterial smooth muscle?
Penis and clitoris
265
Where is adrenaline from?
The adrenal medulla
266
What does adrenaline act on to cause vasoconstriction?
Alpha receptors
267
What does adrenaline act on to cause vasodilation?
Beta receptors
268
Where are alpha receptors predominantly found?
Skin, gut, kidney arterioles
269
What receptors are predominantly found in cardiac and skeletal muscle?
Beta receptors
270
What does angiotensin II do to vascular smooth muscles?
Vasoconstriction
271
What does ADH do to vascular smooth muscles?
Causes vasoconstriction
272
What can over-ride extrinsic mechanisms of control of vascular smooth muscle?
Intrinisc mechanisms like chemical and physical factors
273
What do local metabolic changes within an organ influence?
The contraction of arterial smooth muscles
274
What causes vasodilatation in relation to PO2, PCO2, [H+], [K+], ECF and ATP?
```
Decreased local PO2
Increased local PCO2
Increased local [H+] - decreased pH
Increased extra-cellular [K+]
Increased osmolality of ECF
Adenosine release from ATP
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275
What are local chemicals released within an organ called?
Local humoral agents
276
What can be released in response to tissue injury or inflammation?
Local humoral agents
277
What 4 humoral agents, when released cause vasodilatation?
1. Histamine
2. Prostaglandins
3. Bradykinin
4. Nitric oxide (NO) - this is continuously released by endothelial cells of arteries and arterioles
278
What produces nitric oxide?
Vascular endothelium from the amino acid L-arginine through enzymatic action of nitric oxide synthase (NOS)
279
Name a potent vasdilator which is important in the regulation of blood flow and maintenance of vascular health?
Nitric Oxide
280
What does shear stress on vascular endothelium, as a result of increased flow cause?
Release of calcium in vascular endothelial cells and the subsequent activation of NOS i.e. flow dependent NO formation.
281
What can also induce NO formation?
Chemical stimuli
282
How do chemical stimuli induce NO formation?
Receptor stimulated NO formation - many vasoactive substances act through stimulation of NO formation.
283
NO diffuses from the vascular endothelium into "where", to activate the formation of "what", that serves as "what"?
NO diffuses from the vascualr endothelium into the adjacent smooth muscle cells where it activates the formation of cGMP that serves as a second messenger for signalling smooth muscle relaxation.
284
What converts L-arginine to nitric oxide in the endothelium?
eNOS
285
Give 4 local humoral agents that the release of causes vasoconstriction?
1. Serotonin
2. Thromboxane A2
3. Leukotrienes
4. Endothelin
286
What is a potent vasoconstrictor released from endothelial cells. Its production is stimulatsed by angiotensin II and vasopressin?
Endothelin
287
What does the cold cause to vascular smooth muscle?
Vasoconstriction
288
In relation to myogenic response to stretch: what happens when MAP rises?
Resistance to vessels automatically constricts to limit flow
289
What does sheer stress do to vascular smooth muscles?
Dilatation of arterioles causes sheer stress in the arteries upstream to make them dilate. This increases blood flow to metabolically active tissues.
290
Where do large veins in limbs lie between?
Skeletal muscles
291
What does contraction of muscles aid?
Venous return
292
What structures allow blood to move forward towards the heart?
One-way venous valves
293
What kind of response does exercise cause?
Acute CVS responses
294
During exercise what happens to sympathetic nerve activity?
Increases
295
When sympathetic nerve activity increases during exercise, what happens to HR, SV and CO?
All increase
296
What does sympathetic vasomotor nerves reducing flow to kidneys and gut - vasoconstriction occur in?
Exercise
297
During excersise, in skeletal and cardiac muscle, what does metabolic hyperaemia overcome?
Vasomotor drive - vasodilatation
298
What does increase in CO do to systolic BP?
| What does metabolic hyperaemia do to TPR and DBP?
Increases systolic BP
| Decreases TPR and decreases DBP (i.e. the pulse pressure increases)
299
What does regular aerobic exercise help reduce?
Blood pressure
300
What are these responses due to: reduction in sympathetic tone and NA levels, increased parasympathetic tone to heart, cardiac remodelling, reduction in plasma renin levels, improved endothelial function (increase vasodilators, decrease vasoconstrictors) and decrease arterial stiffening?
Chronic cardiovascular responses to regular exercise
301
What is shock?
An abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation
302
What are the 4 stages in shock that lead to cellular failure?
1. Inadequate tissue perfusion
2. Inadequate tissue oxygenation
3. Anaerobic metabolism
4. Accumulation of metabolic waste products
303
What two factors does adequate tissue perfusion depend on?
1. Adequate blood pressure
| 2. Adequate cardiac output
304
What initiates hypovolaemic shock?
Loss of blood volume
305
What are the 5 steps in hypovolaemic shock that lead to inadequate tissue perfusion?
1. Decreased blood volume
2. Decreased venous return
3. Decreased End Diastolic Volume
4. Decreased stroke volume
5. Decreased cardiac output and decreased blood pressure
306
What is the term for sustained hypotension caused by decreased cardiac contracility?
Cardiogenic shock
307
What are the 3 steps in cardiogenic shock that lead to inadequate tissue perfusion?
1. Decreased cardiac contracility
2. Decreased stroke volume
3. Decreased cardiac output and decreased blood pressure
308
What type of shock is a tension pneumothorax?
Obstructive shock
309
What are the 5 steps in obstrutive shock, that lead to inadequate tissue perfusion?
1. Increased intra-thoracic pressure
2. Decreased venous return
3. Decreased End Diastolic Volume
4. Decreased cardiac output and decreased blood pressure
5. Inadequate tissue perfusion
310
Give the 4 steps that occur in neurogenic shock to cause inadequate tissue perfusion?
1. Loss of sympathetic tone
2. Massive venous and arterial vasodilatation
3. Decreased venous return and decreased TPR
4. Decreased CO and decreased BP
311
What are the 4 steps in vasoactive shock that leads to inadequate tissue perfusion?
1. Release of vasoactive mediators
2. Massive venous and arterial dilatation - also increased capillary permeability
3. Decreased venous return and decreased TPR
4. Decreased CO and BP
312
What is the immediate treatment for anaphylactic shock?
Adrenaline
313
What is used to treat septic shock?
Vassopressors
314
What is used for tension pneumothorax shock?
Immediate chest drain
315
What is used to treat cardiogenic shock?
Inotropes
316
What are the two main causes of hypovolaemic shock, that lead to decreased blood volume?
1. Haemorrhage
| 2. Vomiting, diarrhoea, excessive sweating = decreased ECFV
317
How much blood has to be lost before compensatory mechanisms can not longer maintain blood pressure?
> 30%
318
In class I, II, III and IV of shock - what is the blood loss?
I : up to 750mL
II : 750 - 1500
III : 1500 - 2000
IV : >2000
319
What are the pulse rate values for shock classes I, II, III, and IV?
I :
320
What two classes of shock are the blood pressures normal in?
Class one and two
321
What are the respiratory rate values for all the classes of haemorrhagice shock?
I : 14-20
II : 20-30
III : 30-40
IV : >35
