Normal Structure And function Flashcards
1
Q
Cardiac muscle is unstriated - TRUE OR FALSE
A
False - it is striated
2
Q
Cardiac myocytes are electrically coupled by…
A
Gap junctions
3
Q
Desmosomes have what function within cardiac muscle?
A
Provide mechanical adhesion between adjacent cardiac cells
4
Q
Contractile unit of muscle
A
Myofibril
5
Q
Actin filaments form the light/dark appearance of myofibrils?
A
Light
6
Q
Within each myofibril, actin and myosin are arranged into….
A
Sarcomeres
7
Q
Muscle tension is produced by ___ of actin filaments over myosin filaments
A
Sliding
8
Q
Force generation depends upon ________ interaction between myosin and actin filaments
A
ATP-dependent
9
Q
Requirements for muscle contraction (2)
A
ATP
Calcium
10
Q
Role of calcium in muscle contraction
A
Binds to troponin, moving the tropomyosin away from the actin myosin binding site
11
Q
Calcium is released from the _______ _______ in cardiac muscle
A
Sarcoplasmic reticulum
12
Q
TRUE OR FALSE - the release of calcium from the sarcoplasmic reticulum is dependent on the presence of extra cellular calcium
A
True
13
Q
Calcium induced calcium release is
A
The release of calcium in response to the release of calcium
14
Q
Where does the CIcR start in cardiac muscle?
A
The calcium influx during ventricular muscle action potential through L-type calcium channels - travels down T-tubules increasing the release from SR
15
Q
Channel that removes calcium from the cell back to the SR
A
Ca-ATPase
16
Q
Excitation of the heart normally originations in the ________ cells of the ___ ____ ____
A
pacemaker cells of the SAN
17
Q
The heart is normally under the control of the ___
A
SAN
18
Q
TRUE or FALSE - the cells in the SAN have a resting membrane potential
A
False
The SAN constantly drifts towards depolarisation
19
Q
The pacemaker potential is due to what 3 ion currents?
A
Na influx and K influx (funny current)
Transient Ca influx
Decreased K efflux
20
Q
Ion channel responsible for the rising phase of the action potential in the SAN?
A
LTCC
21
Q
Ion channel responsible for the falling phase of the action potential in the SAN?
A
K channel –> K efflux
LTCC inactivation
22
Q
Why is conduction is delayed within the AVN?
A
to allow for atrial systole
23
Q
Phase 0 of ventricular AP
A
Na influx
24
Q
Phase 1 of ventricular AP
A
closure of Na, transient K efflux
25
Phase 2 of ventricular AP
LTCC balanced with transient K efflux
26
Phase 3 of ventricular AP
Ca channels close but delayed rectifier K channels remain open
27
Phase 4 of ventricular AP
resting membrane potential
28
Nerve which exerts continuous control over the heart?
Vagus nerve
29
Autonomic predominant control over the heart?
Parasympathetic
30
Ach from parasympathetic system acts on which receptor in the heart?
M2 muscarinic
31
NA from sympathetic system acts on which receptor in the heart?
B1 adrenoceptors
32
NA has a positive/negative chronotropic effect on the heart?
positive
33
ACh has a positive/negative chronotropic effect on the heart?
negative
34
P wave represents...
atrial depolarisation
35
QRS complex represents...
ventricular depolarisation
36
T wave represents...
ventricular repolarisation
37
Drug that can be used in extreme bradycardia
Atropine
38
Atropine works as...
competitive antagonist of ACh
39
Two requirements for cardiac muscle contraction
ATP and Calcium
40
requirement for cardiac muscle relaxation
ATP
41
Calcium binds to ______ to move the ______ out of the vicinty of the actin-myosin binding site
troponin, tropomyosin
42
Calcium is released from the _______ _______ during ventricular contraction
sarcoplasmic reticulum
43
T-tubules ensure...
that calcium gets to all levels of the cell to maximise contraction
44
What is the purpose of the refractory period in cardiac muscle?
it prevents tetanic contraction within the heart muscle.
45
Calcium is taken back into the sarcoplasmic reticulum by...
the Ca-ATPase
46
SV =
EDV - ESV
47
EDV is determined by...
the venous return to the heart
48
EDV determines the....
preload
49
diastole
the heart ventricles are relaxed and fill with blood
50
systole
the heart ventricles contract and pump blood into the aorta and pulmonary artery
51
5 phases of cardiac cycle
1. passive filling
2. atrial contraction
3. isovolumetric ventricular contraction
4. ventricular ejection
5. isovolumetric ventricular relaxation
52
What phase during the cardiac cycle is the P wave seen?
during phase 2 - atrial contraction
53
The ventricles are 80% full by the end of passive filling - true or false
true
54
The atria contract between the ____ and the ____ _____
P wave and the QRS complex
55
Where is the QRS complex seen in the cardiac cycle?
Phase 3 - the isovolumetric ventricular contraction
56
The first heart sound occurs when?
during isovolumetric ventricular contraction
57
What causes the first heart sound?
the pressure in the ventricles exceeding that of the atria
58
T wave signals...
ventricular repolarisation
59
What happens during ventricular ejection?
valves open and the SV is ejected
60
what causes the second heart sound?
the ventricular pressure falling below the aortic and pulmonary artery pressure
61
Auscultation for aortic valve
right sternal edge, 2nd intercostal space
62
Auscultation for pulmonary valve
left sternal edge, 2nd intercostal space
63
Auscultation for tricuspid valve
inferior left sternal margin, 4th intercostal space
64
auscultation for mitral valve
5th intercostal space in mid-clavicular line
65
during diastole the ventricles are _______ and ____ with blood
relaxed and fill with blood
66
During systole the ventricles ____ and ____ blood into the ____ and _____ _____
contract and pump blood into the aorta and pulmonary artery
67
At a heart rate of 75bpm, ventricular diastole lasts (0.5/0.3) secs and ventricular systole lasts (0.5/0.3) secs
0.5, 0.3
68
5 stages of the cardiac cycle
1. Passive Filling
2. Atrial Contraction
3. Isovolumetric Ventricular Contraction
4. Ventricular Ejection
5. Isovolumetric Ventricular Relaxation
69
Events during passive filling of the heart
Pressure in atria and ventricles is nearly 0, AV valves are open allowing venous return to flow into ventricles, Ventricles fill about 80%
70
Events during atrial contraction
P wave signals depolarisation of atria, End diastolic volume of ~130ml
71
Events during isovolumetric ventricular contraction
Ventricular contraction starts QRS of ECG, pressure rises, first heart sound as ventricular pressure rises over atria, tension rises rapidly
72
Events during ventricular ejection
aortic and pulmonary valves open, aortic pressure rises, ESV left behind
73
Events during isovolumetric ventricular relaxation
T wave signals ventricular repolarisation, ventricles relax and pressure falls, aortic and pulmonary valves shut leading to second heart sound
74
When might splitting of the heart sound be heard?
at inspiration as the inspiratory pressure is not high enough to promote pulmonary valve closure at the exact same time as the aorta.
75
When does the JVP occur in relation to the atrial pressure wave?
right after atrial pressure waves
76
Systolic blood pressure is...
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
77
Systolic blood pressure should be maintained between ____ and ____ and not exceed ____mmHG
90 and 120, not exceed 140mmHg
78
Diastolic blood pressure is...
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
79
Diastolic pressure should not reach or exceed...
90mmHg
80
Blood normally flows in the arteries in a laminar fashion - True or false?
True
81
Korotkoff sounds are heard when...
The cuff pressure is between the systolic and diastolic blood pressure
82
Where is diastolic pressure recorded according to korotkoff sounds?
when no sounds are heard any more
83
1st korotkoff sound
the first sound is heard at peak systolic pressure
84
Pressure gradient =
MAP - Central Venous pressure
85
The right atrial pressure is...
close to zero
86
5th Korotkoff sound
no sound is heard because of uninterrupted smooth laminar flow
87
The MAP is the average _____ blood pressure during a single ____ ____
arterial, cardiac cycle
88
MAP =
[(2xdiastolic) + systolic] / 3
89
How much MAP is required to perfuse the coronary arteries, brain and kidneys?
60 mmHg
90
MAP is also equal to?
CO x TPR
91
SV is...
the volume of blood pumped by each ventricle of the heart per heartbeat
92
Parasympathetic system has an effect on the arteries and arterioles - True or False?
False - the sympathetic stimulation causes vasoconstriction
93
What effect does sympathetic stimulation have on the veins?
increased vasoconstriction --> increased venous return and greater SV
94
Where do the baroreceptors originate?
aortic arch
| carotid sinus
95
How do the aortic baroreceptors send signals to the medulla?
CN X - the vagus nerve
96
How do the carotid sinus baroreceptors send signals to the medulla?
CN IX - the glossopharyngeal nerve
97
Foramen where the CN X exits the skull
the jugular foramen
98
Foramen where CN IX exits the skull
the jugular foramen
99
The baroreceptor reflex is important in acute and chronic situations - true or false?
False - the baroreceptor reflex becomes desensitised in chronic high blood pressure and thus only adapts to acute changes
100
Action of sympathetic nervous system in baroreceptor reflex
Causes vasoconstriction when the MAP decreases; MAP decrease causes reduced firing of baroreceptors decreasing vagal tone and increase sympathetic tone
101
Sympathetic effect on TPR
causes an increase in TPR
102
Long term control of MAP is largely controlled by...
blood volume
103
Around ___% of body weight in men is water
60%
104
Total body fluid =
Intracellular fluid (2/3rd) + Extracellular fluid (1/3rd)
105
ECF =
plasma volume + interstitial fluid
106
What two main factors affect ECF volume?
Water excess or deficit
| Na excess or deficit
107
Hormones that regulate ECF volume (3)
RAAS
ANP
ADH
108
Renin is released from...
the kidneys
109
Renin stimulates the release of?
angiotensin I
110
Angiotensin I is produced from?
angiotensinogen from the liver
111
AngI is converted to Ang II by?
Angiotensin converting enzyme
112
ACE is produced by?
pulmonary vascular endothelium
113
AngII stimulates the release of?
aldosterone
114
Aldosterone is produced
in the zona glomerulosa of the adrenal cortex
115
AngII causes (2)
systemic vasoconstriction, ADH release
116
Aldosterone is a steroid hormone - True or false
True
117
Aldosterone acts ont eh kidneys to?
increase sodium and water retention
118
Increasing sodium and water retention causes?
increase in plasma volume
119
Renin is released from where in the kidney?
the juxtaglomerular apparatus
120
3 things which stimulate renin release
(1) renal artery hypotension
(2) stimulation of renal sympathetic nerves
(3) decreased Na in renal tubular fluid
121
Cells responsible for sensing Na in the renal tubules
Macula densa cells
122
Type of cells that release renin
granular cells
123
Where is atrial naturietic peptide produced?
atrial myocytes
124
What stimulates production of ANP?
atrial distension
125
ANP causes...
excretion of salt and water from the kidnyes
126
ANP acts to ________ the RAAS system
counteract
127
ADH is also known as?
Vasopressin
128
ADH is synthesised by the _______ and stored in the ________
hypothalamus, posterior pituitary
129
What two things stimulate the release of ADH?
1. reduced ECF volume
| 2. Increased ECF osmolarity
130
Normal osmolarity of ECF is...
280mosml/l
131
AD acts on the kidney tubules to...
increase the reabsorption of water
132
ADH acts on the blood vessels to...
cause vasoconstriction
133
The actions of ADH on the blood vessels is important in...
hypovolaemic shock
134
Pulse pressure =
SBP - DBP
135
Resistance = (Pouiseilles law)
[n.L]/r^4
136
What has the greatest effect on resistance?
radius
137
Extrinsic control of vascular smooth muscle involves which two factors?
hormones
| nerves
138
Which nerves supply the vascular smooth muscle?
sympathetic
139
Sympathetic nerves supply _____ to the vascular smooth muscle
noradrenaline
140
Noradrenaline acts on __ ________ in the vascular smooth muscle
a-adrenoceptors
141
True or False - blood vessels are partially constricted at rest to maintain blood pressure
True - this is called vasomotor tone
142
What causes the vasomotor tone?
the tonic discharge from sympathetic fibres
143
Adrenaline is released from...
the adrenal medulla above the kidneys
144
Adrenaline acts differently depending on the organ and receptor - True or False?
True
145
Adrenaline acts on a adrenoceptors in the cardiac and skeletal muscles to vasodilation - True or False
False - acts on B2 adrenoceptors to cause vasodilation
146
What adrenoceptors does adrenaline act on in the skin, gut and kidney arterioles? What is the effect?
a-adrenoceptors, causes vasoconstriction
147
Why does adrenaline have alternating effects in different organs?
allows for strategic distribution of blood flow
148
Angiotensin II and ADH cause _______
vasoconstriction
149
Intrinsic controls of vascular smooth muscle are...
local metabolic changes which can override extrinsic effects
150
Effect of increased PO2 on vascular smooth muscle
constriction
151
Effect of increased PCO2 on vascular smooth muscle
vasodilation
152
Effect of increased H+ on vascular smooth muscle
vasodilation
153
Effect of increased EC K+ on vascular smooth muscle
vasodilation
154
Effect of decreased osmolality on vascular smooth muscle
constriction
155
Humoral agents which increase relaxation of vascular smooth muscle
histamine, bradykinin, Nitric oxide
156
Humoral agents which increase vasoconstriction of vascular smooth muscle
serotonin, thromboxane A2, leukotrienes, endothelin
157
Endothelin is produced by...
endothelial cells
158
What factors can damage endothelial health? (4)
high BP, hypercholesterolaemia, diabetes, smoking
159
Endothelial produced vasodilators have what effects? (3)
Anti-thrombotic; anti-inflammatory; anti-oxidants
160
Effect of cold temperature on vascular smooth muscle?
vasoconstriction
161
Nitric oxide is produced from?
L-Arginine
162
Nitric oxide has a long half-life - T or F?
False, it has a short half life of a few seconds
163
Calcium is released from the endothelial wall in the presence of...
shear stress - leads to activation of NOS --> NO
164
NO activates ____ which aids vascular smooth muscle relaxation
cGMP
165
Four factors which influence venous return
Increased blood volume
Increased vasomotor tone
Increased skeletal muscle pump
Increased respiratory pump
166
What does increasing venous return do?
increases atrial pressure and thus EDV and SV
167
Are venous smooth muscles supplied by nerves?
yes sympathetic nerves
168
An increase in CO increases DBP - true or false?
false - increases SBP
169
Metabolic hyperaemia causes a decrease in what two things?
TPR and DBP
170
Exercise causes an increase in...
pulse pressure
171
Likely effects of chronic exercise on CVS (6)
reduction in sympathetic tone; increases parasympathetic tone to the heart; cardiac remodelling; reduction in plasma renin levels; improved endothelial function; decreased arterial stiffening
172
Sympathetic stimulation increases HR by exerting what two effects?
increasing rate of SAN firing
| decreases AV nodal delay
173
condition where the pericardial cavity fills with blood preventing contraction
cardiac tamponade
174
Coronary arteries branch of at...?
the ascending aorta, almost instantly after leaving the ventricle
175
Vein that drains blood back into the right atrium from the myocardium
coronary sinus
176
Vagus nerve descends where?
lateral to the trachea, behind the hila of the lungs, medially by the heart
177
Where does the phrenic nerve descend?
down the lateral side of the heart
178
The left coronary artery splits into what three branches?
circumflex, left marginal and left anterior descending
179
the left anterior descending artery has what extra branch?
the lateral branch
180
The right coronary artery splits into which 2 arteries?
right marginal artery anteriorly;
| posterior interventricular artery
181
mitral stenosis can be heard when?
during diastole (without pulse)
182
mitral regurgitation can be heard when?
during systole (with pulse)
183
What germ layer is the heart derived from?
visceral part of the lateral mesoderm
184
during cranio-caudal folding the heart moves from where to where?
the cervical to thoracic area
185
there are initially how many pairs of the aortic arches?
6
186
the 3rd arch of the aorta develops into...
the common carotid artery and the first part of the internal carotid artery
187
The 4th aortic arch develops into...
the right subcalvian artery and part of the aortic arch
188
the 6th aortic arch becomes...
the sprout branches that form the pulmonary arteries and ductus arteriosus on the left
189
the ductus arteriosus becomes what post-birth?
the ligamentus arteriosum
190
What is the function of the Vitelline veins?
drain the yolk sac - important in development of gut and portal system
191
What is the function of the umbilical veins?
oxygenated blood from the placenta - right vein degenerates
192
Which umbilical vein degenerates?
right umbilical
193
What does the left umbilical vein become?
the definitive umbilical vein
194
What do the cardinal veins give rise to?
the systemic venous system
195
The anterior cardinal veins give rise to...
the jugular and left brachiocephalic vein, and the SVC
196
the posterior cardinal veins give rise to...
the azygous and hemiazygous systems, gonadal and renal veins, iliac veins, IVC
197
What two systems are involved in the circulatory systems?
the cardiovascular system, the lymphatic system
198
What are the roles of the circulatory system? (5)
transport of oxygen and nutrients; transport of CO2 and metabolic waste; temperature regulation; distribution of hormones; penile erection in males
199
where is most of the blood held in the circulatory system?
veins ~60%
200
What are the 3 basic layers to the blood vessels?
Tunica intima, tunica media, tunica adventitia
201
What makes up the tunica intima?
single layer of squamous epithelial cells attached to a basal lamina and a thin layer of connective tissue
202
What makes up the tunica media?
smooth muscle and elastic tissue
203
What makes up the tunica adeventitia?
connective tissue
204
true or false - large arteries can get all the nutrients from the lumen of their vessel?
false - only the inner half - the rest can receive nutrients from the vaso vasorum
205
What is the vaso vasorum?
the vascular supply to the large arteries.
206
what cells in the basal lamina may help capillaries constrict to control blood flow?
pericytes
207
what are the 3 types of capillary?
continuous, fenestrated, sinusoidal (discontinuous)
208
which type of capillary is most common?
continous
209
Where are continuous capillaries found?
skin, lung, muscle, connective tissue, nerves
210
What feature determines fenestrated capillaries?
they have pore in their walls
211
where are fenestrated capillaries found?
in the mucosa of the gut, endocrine glands, glomeruli of the kidney
212
What feature determines sinusoidal capillaries?
lack a basal lamina and have large gaps throughout
213
where are sinusoidal capillaries usually found?
liver, spleen, bone marrow
214
3 layers of the heart
endocardium, myocardium, epicardium
215
Where does the endocardium extend to?
the valves
216
What is included in the endocardium structure? (4)
endothelium, basal lamina, collagen fibres, denser connective tissue
217
what is the sub-endocardium?
extension of the endocardium (loose connective tissue) which contains small blood vessels, nerves and impulse conducting system
218
Features of the myocardial cells
one central nucleus (maybe 2), irregularly placed intercalated discs
219
What feature is likely found in the epicardial layer of the heart?
large branches of the coronary blood vessels
220
lymphatic capillaries begin as...
blind sacs
221
most of the excess interstitial fluid returns to...
the venous system
222
The passing of lymph through lymph nodes provides opportunities for...
immunological surveillance
223
Things that aid the movement of lymph (2)
hydrostatic pressure, muscles around the lymph vessels, valves within the vessels
224
The lymphatic system helps to deliver fats to the _____ from the _____ _____
liver, small intestine
225
What is shock?
an abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation
226
What affects Stroke Volume (3)?
Preload, Myocardial contractility, Afterload
227
What is hypovolaemic shock?
where a loss in blood volume --> decreased venous return --> decreased EDV and SV --> Decreased CO and MAP --> inadequate perfusion
228
The heart can compensate for what loss in blood volume?
30%
229
What is cardiogenic shock?
Sustained hypotension caused by decreased cardiac contractility
230
How does cardiogenic shock lead to inadequate tissue perfusion?
Decreased cardiac contractility --> decreased SV -->Decreased CO and MAP --> Inadequate tissue perfusion
231
Example of obstructive shock?
Tension Pneumothorax
232
How does a tension pneumothorax lead to inadequate tissue perfusion?
Increased intrathoracic pressure --> decreased venous return --> decreased end diastolic volume & decreased SV --> Decreased CO and MAP --> Inadequate tissue perfusion.
233
What can cause neurogenic shock?
Spinal Cord injury
234
How does a spinal cord injury lead to inadequate tissue perfusion?
Loss of sympathetic tone --> massive venous and arterial vasodilation --> decreased venous return and TPR --> Decreased CO and MAP --> Inadequate tissue perfusion
235
Steps in treatment of Shock?
ABCDE
High flow oxygen
Volume replacement
236
Extra step in treatment of Cardiogenic shock...
ABCDE, high flow oxygen, volume replacement, inotropes
237
Extra step in treatment of shock due to tension pneumothorax...
ABCDE, high flow oxygen, volume replacement, Immediate chest drain
238
Extra step in treatment of anaphylactic shock
ABCDE, high flow oxygen, volume replacement, adrenaline
239
Extra step in treatment of septic shock
ABCDE, high flow oxygen, volume replacement, vasopressors
240
If someone is suffering from haemorrhagic shock, how would you expect to find their pulse?
Fast and thready, potentially weak
241
If someone is suffering from haemorrhagic shock, how would you expect to find their peripheries?
cool and potentially clammy
242
In the presence of blood loss, the baroreceptor reflex sends signals to...
the medulla in the CNS
243
The medulla (increases/decreases) vagal tone during haemorrhagic shock?
decreases
244
The medulla (increases/decreases) sympathetic activity during haemorrhagic shock?
increases
245
An increase in constriction of the veins during haemorrhagic shock leads to....
increased stroke volume
246
An increase in constriction of the arteries during haemorrhagic shock leads to....
increased TPR
247
Effect of sympathetic NS on the heart?
increased HR and contractility
248
Effect of parasympathetic NS on the heart?
decrease HR
249
Where do visceral afferent fibres travel?
alongside sympathetic nerves
250
Visceral reflex afferents from baroreceptors travel mainly in the...
vagus nerve (CN X)
251
Where are the sympathetic ganglia held?
sympathetic chain in the thoracolumbar region
252
What are splanchnic nerves?
pairs of visceral efferents or afferents that carry fibres of the autonomic nervous system
253
Which set of splanchnic nerves are not sympathetic?
pelvic
254
Where are the cardiopulmonary splanchnic nerves are predominantly sided where?
the left side
255
Where is the cardiac plexus found?
At the level of the carina, around the pulmonary trunk
256
WHere are the ganglia for the parasympathetic nerves found?
on the target organ
257
Where are the parasympathetic outputs?
cranial and sacral regions
258
what 4 cranial nerves have their ganglia in the head?
Vagus nerve (CN X), Occulomoter (III), Facial (VII), Glossopharyngeal (IX)
259
CN III
Occulomotor
260
CN VII
Facial
261
CN XI
Glossopharyngeal
262
What is pain?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
263
Somatic sources of chest pain (6)
muscle; joint; boney; intervertebral disc; fibrous; nerve
264
Visceral sources of chest pain (4)
Heart and great vessels, trachea, oesophagus, abdominal viscera
265
Somatic pain is typically described as...
well localised, typically sharp and stabbing pains
266
Visceral pain is typically described as...
dull, aching, nauseating and poorly localised
267
Radiating pain is described as...
pain felt in the centre of chest AND spreading from there
268
Referred pain is described as...
pain only felt at a site remote from the area of tissue damage
269
Where does referred pain tend to travel?
along the dermatomes
270
Which dermatome would herpes zoster most likely cause a sharp somatic chest pain?
T4/5
271
Common radiations of cardiac chest pain?
Jaw, arm, neck, back
272
What is a myocardial infarction?
irreversible death of part of the myocardium due to the occlusion of its arterial blood supply
273
3 surfaces of the heart affected by an MI
Anterior, Inferior, Anterolateral
274
Where do 40-50% of MIs occur?
the LAD
275
where do 30-40% of MIs occur?
the right coronary artery
276
where do 15-20% of MIs occur?
the circumflex artery
277
Commonly used vessels in the revascularisation/bypass grafting of the heart?
radial/internal thoracic artery and the great saphenous vein
278
What may occur if the ischaemia affects the SAN or AVN?
arrhythmias
279
AVN damage during MI can result in...
complete heart block
280
Bundle branch damage during an MI can result in...
bundle branch block
281
decreased PO2 causes ______ of the coronary arterioles
vasodilation
282
Adenosine is naturally produced from?
ATP
283
sympathetic vasoconstriction around the coronary arterioles is overridden by ______ ______ during exercise
metabolic hyperaemia
284
coronary arterioles are supplied by sympathetic vasoconstrictor nerves which act via __-adrenoceptors
a-adrenoceptors
285
peak left coronary blood occurs during (systole/diastole)
diastole - the contraction of the heart during systole constricts the movement of blood in to the coronary arterioles
286
Which arteries anastamose to form the circle of willis?
carotids and basilar arteries
287
which arteries supply the brain?
internal carotids and vertebral arteries
288
which particular part of the brain is very sensitive to hypoxia?
grey matter
289
What types of stroke can occur?
ischaemic or haemorrhagic
290
arterial pressure range within the brain?
60-160mmHg
291
autoregulation of brain arterial pressure fails when...
MABP is outwith 60 - 160mmHg
292
an increase in PCO2 within the brain causes vaso_______
dilation
293
why can hyperventilation lead to fainting?
causes a decrease in PCO2 which causes vasoconstriction within the brain.
294
three things which cross the blood brain barrier?
oxygen, carbon dioxide, glucose
295
average intracranial pressure
8-13mmHg
296
Cerebral perfusion pressure =
MABP - ICP
297
How does glucose cross the BBB?
facilitated diffusion
298
pulmonary BP is typically a (high/low) pressure system
low pressure system - approx 10% of that of the systemic
299
how do the lungs protect against pulmonary oedema?
the absorptive forces exceed the filtration forces
300
hypoxia causes vasoconstriction of the pulmonary arterioles - why?
helps direct blood flow to areas of the lung where the ventilation is better
301
circulating adrenaline causes vasodilation in the skeletal smooth muscle via __adrenoceptors
b2-adrenoceptors
302
the one way venous valves and the skeletal muscle pump allows ?
blood to flow back towards the heart
303
Blood pools in the limb veins if...
venous valves become incompetent
304
What is the result of blood pooling in the limbs?
varicose veins
305
why don't varicose veins lead to a reduction in cardiac output?
there is chronic compensatory increases in blood volume
