Cardiovascular System Flashcards
(301 cards)
1
Q
What is the essential role of the cardiovascular system?
A
meeting the metabolic demands of almost every cell, tissue and organ in the body
2
Q
What happens to speed of diffusion rates over long distances?
A
become very slow
3
Q
Can diffusion meet physiological demands over large distances?
A
no
4
Q
What sort of transport system is the cardio vascular system?
A
bulk/convective transport system
5
Q
What does the cardiovascular system transport?
A
respiratory gasses, nutrients, hormonal signals
6
Q
What organs does the pulmonary circulation provide?
A
lungs
7
Q
What processes are supported by systemic circulation?
A
metabolic
8
Q
in what part of the cardiovascular system does diffusion occur?
A
capillaries in tissues and the lungs
9
Q
Describe the flow of blood through the heart.
A
deoxygenated blood from the body flows into the right atrium from the vena cava and into the right ventricle, out of the pulmonary artery and to the lungs for exchange of O2 and CO2. From the lungs blood flows through the pulmonary vein into the left atrium and then left ventricle. Blood flows out of the left ventricle into the aorta.
10
Q
Name the 5 primary functions of the cardiovascular systems.
A
respiratory gas exchange nutrient supply/waste removal hormonal signalling fluid maintenance body temperature regulation
11
Q
How does the cardiovascular system regulate body temperature?
A
brings blood from deep tissues and organs to the skin so heat can be lost during vasodilation. Vasoconstriction reduces blood flow to peripheries so it isn’t lost in this way
12
Q
What can be done to a sample of blood in a tube to separate it’s contents?
A
centrifugation
13
Q
What are the components of blood?
A
Plasma, white blood cells, red blood cells
14
Q
How will a sample of centrifuged blood look?
A
plasma on the top with a buffy coat in the middle of white blood cells. Red blood cells form the bottom layer
15
Q
What colour is plasma?
A
straw coloured
16
Q
what does plasma consist of?
A
mainly water but, also contains electrolytes, glucose plasma proteins and other organic molecules
17
Q
What is the total blood volume in an average human?
A
5l
18
Q
What is the average plasma volume of a human?
A
3l
19
Q
where are most plasma proteins produced?
A
the liver
20
Q
what are immunoglobulins produced by?
A
mature B lymphocytes
21
Q
what is serum?
A
plasma with clotting agents removed
22
Q
What the 3 major fluid compartments of the body?
A
intracellular, interstitial and vascular
23
Q
what proportion of body water is intracellular?
A
2/3
24
Q
What gradient moves blood around the body?
A
pressure gradient generated by pump action of heart
25
what is the resting blood pressure in the left ventricle?
120 mmHg
26
What structure in the aorta prevents backflow during diastole?
aortic valve
27
What is the average systolic blood pressure in main arteries?
120 mmHg
28
What is the average diastolic blood pressure in the main arteries?
80 mmHg
29
What are the function of the atria?
receives blood from veins
30
what are the function of the ventricles?
pump blood into arteries
31
How does the length of the relaxation phase in the heart compare to the length of the contraction phase?
usually twice as long
32
What is systole?
contraction of the heart
33
Is blood pressure in veins lower or higher than that in the arteries?
lower - approx 10 mmHg
34
What are the major types of blood vessel?
arteries (arterioles)
veins
capillaries
35
What do arterioles control?
entry of blood into capillaries
36
How do veins compare to arteries?
more elastic and thinner walled
37
How thick are capillary walls?
single celled
38
What is the distribution of blood volume in a resting human?
```
systemic veins and venules: 60-70%
pulmonary circulation: 10-12%
heart: 8-11%
systemic arteries: 10-12%
systemic capillaries: 4-5%
```
39
how is percentage of blood volume in systemic veins and venules affected by exercize?
much reduced
40
What does autonomic regulation of the cardiovascular system ensure for the body?
metabolic demands of body are met despite changes in activity
41
What afferent feedback is given from the cardiovascular system?
blood pressure, O2 level, pH level
42
Why is bulk transport necessary?
diffusion is too slow to meet the metabolic demands of the body
43
What part of the nervous system is the cardiovascular system under the control of?
autonomic
44
where does electrical activity in the heart arise from?
sino-atrial node
45
What sort of cell are all cells in the heart?
muscle cells
46
In normal hearts how many routes are there for action potential to travel to the ventricles?
one
47
Is the fibrous septum conductive or non-conductive?
non-conductive
48
what is the name of the fibres that supply electrical signal to the ventricles down the septum?
purkinje fibres
49
How long is the duration of a cardiac action potential?
long (300-350 ms)
50
How does the length of action potential compare between atria and ventricles?
atrial AP is much shorter
51
How many phases are there of the ventricular action potential?
5 (0-4)
52
What happens during phase 0 of the ventricular action potential?
due to activation of voltage gated Na+ channels there is an inward current of Na+ (movement towards Na+ equilibrium potential) and a rapid upstroke of action potential
53
How does the membrane potential change during phase 0 of ventricular action potential?
membrane becomes + (depolarizes) as permeability to sodium increases
54
What happens during phase 1 of the ventricular action potential?
early repolarisation of the membrane due to inactivation of sodium channels
55
How does the membrane potential change during phase 1 of ventricular action potential?
starts to become more negative
56
What is phase 2 of the ventricular action potential known as?
plateau phase
57
What happens during phase 2 of the ventricular action potential?
plateau phase due to inward current through voltage gated calcium channels.
58
How quick are calcium channels to activate and inactivate?
slow
59
What happens during phase 3 of the ventricular action potential?
repolarization brought about by inactivation of calcium channels and increase in membrane permeability to potassium
60
What happens during phase 4 of the ventricular action potential?
corresponds to the resting membrane potential and is largely determined by permeability to K+
61
What action triggers Ca2+ release from the sarcoplasmic reticulum?
Ca influx through open gated Ca channels
62
What process initiates cardiac muscle contraction?
Ca influx through open gated Ca channels triggers Ca2+ release from the sarcoplasmic reticulum
63
What does the inward current of Ca delay?
repolarization
64
What does delayed repolarization of cardiac myocytes maintain?
plateau phase of ventricular contraction cycle
65
What is the second part of the plateau phase?
the refractory period
66
How excitable is the cell while it is depolarized?
it is electrically in excitable
67
Why is it important that the cell is in-excitable while depolarized?
each action potential only generates a single twitch as tetany would be fatal
68
What state are sodium channels in during the absolute refractory period?
sodium channels are inactivated
69
When do sodium channels begin to recover from inactivation ?
as the membrane potential repolarizes from -50mV
70
What is the process of sodium channels recovering from inactivation called?
relative refractory period
71
Why do sinoatrial nodes show an unstable resting membrane potential?
combination of slow inward sodium and calcium currents
72
Which branches of the autonomic nervous system innervate sino-atrial and conduction fibres?
both sympathetic and parasympathetic neurons
73
How does sympathetic fibre activity accelerate the heart?
noradrenaline binds to beta1-adrenoreceptors resulting in an increased slope of the pacemaker potential
74
What is the acceleration of heart rate called?
positive chronotropism
75
How does parasympathetic fibre activity slow the heart?
acetylcholine binds to muscarinic receptors causing a decrease in the slope of the pacemaker potential and also slight hyperpolarisation
76
What is deceleration of the heart called?
negative chronotropism
77
What is found within intercalated disks which aid the transfer of electrical signal between myocytes?
gap junctions
78
Why is the conduction velocity of the AV node relatively slow?
ensures atrial filling of the ventricles is complete before the ventricles contract
79
What does the electrocardiogram detect?
electrical field around the heart set up by the conduction of action potential throughout the heart
80
what does the P wave on a ECG show?
atrial depolarisation
81
What does the QRS complex on a ECG show?
ventricular depolarization
82
What does the T wave on an ECG show?
ventricular repolarisation
83
during which of the waves of a ECG does atrial repolarisation occur?
QRS
84
What occurs during the R wave?
depolarization spreads downwards and outwards from the ventricular septum
85
What happens in the heart and on the ECG during the ST segment?
ventricles are depolarized and ECG returns to isoelectric line
86
What happens in the heart during the T wave?
repolarization spreading inwards towards the ventricular septum
87
Where do action-potentials arrive?
specialised cardiac myocytes in the sinoatrial nodes
88
What is heart rate controlled by?
changing the rate of diastolic depolarization of pacemaker cells in the sinoatrial node
89
What is the action potential conducted around the heart by?
conduction system of specialised cardiac myocytes
90
What phase is the plateau phase?
2
91
What does Ca influx during phase 2 trigger?
Ca release and cardiac muscle contraction
92
what does the plateau phase establish?
a relatively long refractory period that prevents sustained contraction and re-entrant arrhythmias
93
What substances does the ideal gas law apply to?
fluid and gas
94
what key substance in the body can the ideal gas law be applied to?
blood
95
What does the ideal gas law state?
as pressure increases volume will reduce
96
What is the name of the right atrial valve?
tricuspid valve
97
What is the name of the right aortic valve?
pulmonary artery valve
98
what is the name of the left atrial valve?
mitral valve
99
what is the name of the left aortic valve?
aortic valve
100
How many pumps are contained within the heart?
2
101
What part of the ECG shows the onset of atrial depolarisation and systole?
P wave
102
what part of the ECG shows depolarization of ventricles?
QRS complex
103
When does passive ventricle filling occur?
diastole
104
What part of the ECG shows pressure decrease in LV and aortic valve closing?
T
105
Why is it important that the aortic and pulmonary valves close once the pressure in the ventricles decreases?
prevents back flow
106
What happens to ventricular volume during ventricular filling?
passive filling of ventricles so volume increases
107
What does ventricular filling end with?
atrial systole
108
What is isovolumetric contraction?
Ventricle is contracting but the aortic valve remains closed. Pressure is high enough to close mitral valve but not to open aortic valve
109
What happens during the ejection phase?
aortic valve opens and blood is expelled, volume of ventricles decreases rapidly
110
What happens during isovolumetric relaxation in the left ventricle?
aortic valve closes, mitral valve remains closed
111
What is end diastolic volume (EDV)?
volume of ventricles before atrial systole (maximum volume)
112
Does EDV or ESV describe the maximum ventricular volume?
EDV
113
Does EDV or ESV describe the minimum ventricular volume?
ESV
114
What is end systolic volume (ESV)?
volume of ventricles after ventricular systole and before mitral/tricuspid valves reopen
115
What is the difference between end diastolic volume and end systolic volume known as?
stroke volume
116
Define stroke volume
volume of blood ejected from each ventricle on each beat
117
when does the aortic valve open in the left ventricle?
when ventricular pressure is greater than aortic pressure
118
what phase of ventricular volume changes is started by the opening of the aortic valve?
ejection phase
119
What pressure changes must take place in the left ventricle before the aortic valve closes?
when ventricular pressure is less than aortic pressure
120
what pressure changes must take place in the left ventricle before the mitral valve opens?
ventricular pressure is greater than atrial pressure
121
what is the dicrotic notch?
slight rise in aortic blood pressure after the aortic valve closes
122
define cardiac output (CO)
volume of blood in litres pumped by the heart per unit time
123
what is stroke volume measured in?
litres per beat
124
what is the equation for cardiac output?
CO = stroke volume(litres per beat) X HR (bpm)
125
what is average cardiac output?
4-7 litres per minute
126
what is pre-load?
degree of stretch on resting muscle prior to contraction
127
what is after load?
tension against which the muscle must contract
128
How does cardiac muscle behave in high inotropic state?
has higher elasticity so the stretch in muscle prior to contraction will produce greater tension
129
what effect does increase in preload have on cardiac muscle?
stretches the sarcomeres
130
What do starling curves show the relationship between?
pre-load and amount of blood ejected
131
what does a starling curve show the volume ejected from heart at each beat depends on?
filling pressure of the ventricles
132
What does stretch during preload do to the force of contraction?
increases it
133
How does a fuller ventricle affect stroke volume?
greater stroke volume
134
What is Starlings Law of the Heart?
the energy of contraction of a cardiac muscle fibre is proportional to the initial fibre length at rest
135
What are the heart inlet valves?
tricuspid and mitral (left)
136
what are the heart outlet valves?
pulmonary and aortic (left)
137
When does atrial contraction become significant in filling the ventricles?
where HR is elevated above rest
138
In a normal heart how much of stroke volume is ejected at each beat?
~60%
139
What do stroke volume and cardiac output depend on?
filling of the ventricle during diastole
140
What process determines preload?
filling of the ventricle during diastole
141
What does a greater preload lead to?
greater energy of subsequent contraction
142
What are the 3 physiological consequences of Starlings law?
Output of right and left ventricles is matched
pooling of blood in veins assists with increasing preload and therefore stroke volume during the onset of exercise
heart is sensitive to changes in posture as preload reduces for a short period when moving from lying to standing
143
What are the 3 basic layers of muscular blood vessels?
intima
media
adventitia
144
what is contained within the intima layer of muscular blood vessels?
specialised endothelial cells, basal lamina, intimal connective tissue
145
what is contained within the media layer of muscular blood vessels?
elastin and smooth muscle
146
what is contained within the adventitia layer of muscular blood vessels?
connective tissue, vasoconstrictor fibres (sympathetic nerve fibres)
147
what does connective tissue in the adventitia layer provide?
support for the blood vessels
148
name the 6 vessel types
```
large elastic artery
muscular arteries
arterioles
capillaries
venules
veins
```
149
give 3 examples of large elastic arteries
aorta
pulmonary arteries
carotid arteries
150
what is the wall thickness of the large elastic artery?
2mm
151
what is the lumen diameter of large elastic arteries?
25mm
152
describe the histology of large elastic arteries
thick tunica media with lots of elastin
153
give 3 examples of muscular arteries
radial, femoral, coronary
154
what is the wall thickness of the muscular arteries?
1mm
155
what is the lumen diameter of the muscular arteries?
4.5mm
156
describe the histology of muscular arteries
media mainly composed of smooth muscle. well defined elastic laminae
157
what is the function of large elastic arteries?
windkessel stretch to accommodate blood in systole
158
what is the Windkessel stretch?
energy from systole is stored in the elastic walls and used during diastole
159
what is the function of muscular arteries?
distributing vessels
160
what is the wall thickness of arterioles?
20 micro metres
161
what is the lumen diameter of arterioles?
30 micro metres
162
describe the histology of arterioles
contain one to several layers of smooth muscle
163
what is the function of arterioles?
resistance vessels and act as a gateway to the micro circulation. Dampen oscillations in flow and pressure
164
what is the wall thickness of capillaries?
1 micro metre
165
what is the lumen diameter of capillaries?
6 micro metres
166
describe the histology of capillaries
endothelial cell layer resting on the basement membrane. No smooth muscle
167
describe the function of capillaries
blood travels slowly through these exchange vessels allowing time for diffusion
168
what is the wall thickness of venules?
2 micro metres
169
what is the lumen diameter in venules?
20 micro metres
170
describe the histology of venules
some smooth muscle
171
what is the function of venules?
collecting vessels as blood leaves the capillaries
172
give 2 examples of veins
vena cava, jugular
173
what is the wall thickness of veins?
1.5mm
174
what is the lumen diameter of veins?
30mm
175
describe the histology of veins
thinner walls than arteries, less elastic tissue. Easily distended. Valves present in veins of limbs
176
what is the function of veins?
capacitance vessels act as a reservoir of blood before it returns to the heart
177
what will doubling the radius of the vessel do to the flow?
increase the flow by 16 times (r to the power 4)
178
what is an increase in lumen radius called?
vasodilation
179
what is a decrease in lumen radius called?
vasoconstriction
180
what is vascular tone?
the degree of vasoconstriction/vasodilation of a vessel
181
what does Darcy's law predict?
flow through a tube of fixed radius will increase in proportion to a rise in pressure
182
why may there be a disproportionate increase in flow for a given pressure in blood vessels?
blood vessels are not rigid tubes. They have elastic tissues in their walls which allows them to be stretched .
183
which is the compliance of blood vessels?
the degree to which blood vessels can be stretched due to their elastic walls
184
why are veins described as capacitance vessels?
due to their ability to markedly increase volume at low pressures
185
what does the capacitance of veins depend on?
tone of the smooth muscle within the venous walls
186
what is the tone of smooth venous muscle controlled by?
sympathetic nervous system
187
what is total peripheral resistance (TPR)?
resistance to flow across systemic circulation
188
does pulmonary circulation operate at a lower or higher pressure than the systemic circulation?
lower
189
where does most resistance to flow occur in the CVS?
arterioles
190
what is the total resistance of a system the sum of?
the resistors in the series
191
how can pulse pressure be calculated?
PP= systolic blood pressure - diastolic blood pressure
192
how can mean arterial blood pressure be calculated?
MABP = diastolic blood pressure + one third of pulse pressure
193
how can cardiac output be calculated?
Mean arterial blood pressure divided by total peripheral resistance
194
what is CVP?
blood pressure in the right atrium (usually around 0 mmHg)
195
what is the primary function of pulmonary circulation?
to perfuse the alveoli of the lung for respiratory gas exchange
196
What does all the volume of the right ventricle pass through?
the alveoli
197
Why is there high capillary density in alveoli?
to optimise gas exchange
198
why does the pulmonary circulation operate at much lower pressure than in the systemic circulation?
because the resistance to flow is very low
199
what are the systolic and diastolic blood pressures in human pulmonary circulation?
systolic: 20-25 mmHg
distolic: 8-12 mmHg
200
what is flow through blood vessels driven by?
pressure gradient
201
what does the circular smooth muscle of the medial layer of arteries and veins control?
flow through the arteries and compliance of veins
202
what does contraction of vascular smooth muscle produce?
vasoconstriction
203
what does relaxation of vascular smooth muscle produce?
vasodilation
204
what represents the balance between constriction and dilation?
vascular tone
205
what gradient does pumping by the heart maintain?
arterial pressure gradient
206
what part of the nervous system is involved in short term regulation of blood pressure?
sympathetic
207
what is the increase in blood flow through exersizing tissues known as?
active or metabolic hyperaemia
208
what causes vasodilation in the arterioles supplying the exercizing tissues?
release of metabolites from the active tissue
209
what are examples of vasodilatory metabolites?
K+, ATP and adenosine
210
what effect can hypoxia (reduced o2 levels) have?
vasodilation
211
why is there hyperaemia after exercise?
remains until all metabolites are cleared
212
what does hypoxia in pulmonary blood vessels produce?
vasoconstriction of blood vessels
213
why is ventilation perfusion matching so important?
matching alveolar perfusion with alveolar ventilation to optimise local Va/Q
214
what happens in pulmonary circulation at high altitude?
partial pressure of oxygen in air is low so there is generalised pulmonary vasoconstriction producing pulmonary hypertension
215
what is pulmonary hypertension?
elevated pulmonary artery pressure
216
what is total peripheral resistance determined by?
arteriolar tone
217
what is arteriolar tone controlled by?
metabolites and local hormones
218
what effect does the parasymapthetic nervous system have on heart rate?
reduces it
219
what do baroreceptors monitor?
pressure
220
what effect do changes in pressure have on baroreceptors?
stretch/relaxation of vessel walls, information is sent to the medulla
221
via what nerves is information sent to the medulla from baroreceptors?
vagal and glosso-pharyngeal nerves
222
what is a dynamic response in baroreceptors?
frequency of AP is higher as pressure changes
223
what does reduction in pressure produce in the carotid sinus wall?
relaxation which results in a decrease in firing of the afferent fibre
224
what is the set point of a reflex?
the pressure that the reflex strives to maintain
225
how can set point be altered?
by interaction with central neurons (as occurs in exercise
226
how does the kidney regulate blood pressure?
by removal of fluid (plasma) in the urine
227
describe the feedback loop in kidney interaction with blood pressure
```
increased arterial pressure
increased renal output of sodium and water
reduced ECF volume
reduced plasma (blood) volume
reduced central venous pressure
reduced cardiac output
```
228
in systemic circulation what does metabolic activity cause?
vasodilation of the arterioles supplying that tissue through action of metabolites and low oxygen
229
in pulmonary circulation what does low oxygen cause?
vasoconstriction which is important to ventilation-perfusion matching
230
where do baroreceptors relay information about arterial pressure to in the brain?
nucleus tractus solitarius of the brainstem
231
what governs the short term regulation of blood pressure?
baroreceptor reflex
232
what governs the long term regulation of blood pressure?
kidney control of fluid and electrolyte balance
233
what effect does the high density, thin walled nature of capillaries have?
reduced diffusion distance
234
what is the name of the cell layer within capillaries?
endothelial cells
235
what type of solutes cross the capillary walls easily?
lipophillic
236
how thick is the capillary cell wall?
one cell
237
what molcules need to pass through gaps in the capillary wall?
lipophobic
238
what are the 3 types of capillary?
continuous
fenestrated
discontinuous
239
describe the structure of a continuous capillary
continuous endothelial cell layer around lumen
240
describe the structure of a fenestrated capillary
in between endothelial cells there are gaps in the capillary cell wall to allow transfer of higher weight molecules
241
describe the structure of a discontinuous capillary
large gaps in cell endothelium which allow cells to be passed though the capillary wall
242
give an example of where continuous capillaries can be found
heart and lungs
243
give an example of where fenestrated capillaries can be found
kidney and small intestine (sites of significant water transfer)
244
give an example of where discontinuous capillaries can be found
liver and spleen
245
how does metabolite and gas exchange occur across the capillary wall?
diffusion
246
what happens to the concentration of metabolite in the capillary as blood travels down it?
falls with exponential relation
247
what is capillary wall less permeable to?
plasma proteins
248
how do plasma proteins enter interstitium through the capillary wall?
slowly and with great difficulty
249
why do plasma proteins exert osmotic pressure across capillary walls?
capillary wall is less permeable to them and so they cross slowly and with difficulty
250
what is the osmotic pressure exerted by plasma proteins known as?
colloid osmotic pressure (COP)
251
what are the principal plasma proteins?
ablumin and gamma globulins
252
what is the colloid osmotic pressure of plasma?
21-29 mmHg
253
what is the starling principle?
the balance between forces causing movement of water into and out from the capillary lumen
254
what are starling forces?
forces that tend to cause bulk movement of water across the capillary wall
255
what is the reflection coefficient?
how leaky the capillary wall is
256
what would a reflection coefficient of 1 mean?
capillary is not at all permeable to plasma proteins
257
what would a reflection coefficient of 0 mean?
capillary is very leaky to plasma proteins
258
where does net filtration occur within the capillaries?
arteriolar end
259
where does net absorption occur within the capillaries?
at the venous end
260
what is oedema?
excess tissue fluid and leads to a water-logged interstitium
261
what can oedema effect?
metabolite and gas exchange
262
when does oedema arise?
when fluid production by capillaries is greater than the fluid removal by lymphatics
263
what is elephantitis?
a condition caused by a parasitic nematode worm that blocks the lymphatic drainage to the leg
264
what can local oedema be caused by?
venous/lymphatic obstruction and increased capillary permeability due to injury
265
what can generalised oedema be caused by?
heart failure
| hypo-proteinaemia (a fall in colloid osmotic pressure)
266
how are respiratory gasses and metabolites transfurred across the capillary wall?
diffusion
267
what is ultrafiltration?
the process by which water is transferred across the capillary wall
268
what does ultrafiltration depend on?
balance of hydrostatic and oncotic pressures and the reflection coefficient of the capillary wall
269
what is excess fluid production across the capillary walls drained by?
the lymphatic system
270
how does oedema limit the effectiveness of respiratory gas and metabolite exchange?
by increasing diffusion distances
271
how is venous blood distributed while you're lying down (supine)?
evenly distributed throughout the body
272
how is venous blood distributed when you move from lying down (supine) to standing?
pools in the legs under the influence of gravity
273
what is reduced as an individual moves from supine to standing position?
central venous pressure is reduced
| mean arterial blood pressure
274
what is transient hypotension?
temporary reduction in blood pressure due to pooling of blood in the legs after standing
275
what does transient hypotension trigger?
the baroreceptor reflex
276
what does the baroreceptor detection of transient hypotension trigger?
increased sympathetic output from the medulla
increase in heart rate and total peripheral resistance
mean arterial blood pressure recovers
277
in what areas does blood flow increase in response to leg exercise?
leg muscle - build up of metabolites
heart
skin - heat loss
lungs - reflects the increase in cardiac output
278
what is the Fick Principle?
rate of O2 consumption must be matched by rate of O2 uptake
279
what is metabolic hyperaemia?
increased blood flow during exercise
280
what causes metabolic hyperaemia?
build up of metabolites causes vasodilation, in arterioles supplying exercising muscles, and local increase in blood flow
281
what information relating to the cardiovascular system do chemoreceptors feed to the brainstem?
circulating O2 and CO2 and blood pH
282
during exercise, what branch of the nervous system does feedback from baroreceptors and chemoreceptors influence?
sympathetic branch of ANS
283
what is the set point of a reflex?
the pressure which the reflex tries to maintain
284
how can the set point of a reflex be altered?
central nervous system can alter the set point in response to exercise
285
what are the cardiovascular responses to exercise?
```
metabolic vasodilation
coronary vasodilation
pulmonary blood flow increase
stroke volume increase
splanchnic/renal vasoconstriction
skin blood flow
```
286
what does coronary vasodilation cause?
increased blood flow to the heart
287
why does stroke volume increase plateau?
increased heart rate means that filling time is shortened which means that preload is reduced and volume expelled is smaller
288
why can diastolic blood pressure fall during exercise?
depends on the total peripheral resistance
289
why may total peripheral resistance fall?
vasodilation of exercising muscles and blood vessels at the skin to remove heat
290
what is dynamic exercise?
alternating contraction and relaxation of exercising muscles
291
what are the effects of dynamic exercise on the cardiovascular system?
systolic BP increases as a result of increased cardiac output
diastolic BP may decrease owing to a fall in TPR
vasodilation to aid heat loss
292
what is static exercise?
sustained contraction of exercising muscles
293
what are the effects of static exercise on the cardiovascular system?
both systolic and diastolic BP increase
compression of muscle impairs blood flow
muscle metaboloreceptors mediate a peripheral vasoconstriction
294
what is the central command hypothesis?
anticipation of exercise leads to heart rate and breathing increase
295
what does the cerebral cortex influence?
autonomic and respiratory neurones of the brainstem
296
Is the central command effect seen when there is partial neuromuscular blockade?
yes
297
where is acral skin found?
fingers, toes, palms and the sole of the foot
298
what are arteriovenous anastomosis?
allow bypass of the capillary bed and come closer to the skin
299
what effect does dilation of arteriovenous anastomosis have?
increases skin blood flow to increase heat loss
300
why does arterial blood pressure vary around the day?
in response to changing activity and circadian rhythms in the regulation of blood pressure
301
why do responses to static exercise differ to responses to dynamic exercise?
differences in effects on total peripheral resistance
