Responses to CVS stress

Question 1

Where are veins more likely to distend and why?

Answer 1

In the lower limbs because of gravity

Question 2

What effect does gravity have in the hydrostatic pressure of the blood?

Answer 2

Increases the hydrostatic pressure of the blood in various tissues below the heart with more fluid being lost into the tissues

Question 3

What effect does increased hydrostatic pressure have on circulating blood volume?

Answer 3

It reduces the effective circulating blood volume

Question 4

Why might reduction in effective circulating blood volume induce a hypertensive effect?

Answer 4

More fluid being lost in tissues, less volume in the venous system, less blood returned to the heart, heart beats less powerfully (Starling’s law of the heart), reduction in stroke volume

Question 5

Where do you find arterial baroreceptors?

Answer 5

In the carotid sinus

In the aortic arch

Question 6

When are baroreceptors the most sensitive?

Answer 6

Either side of the mean arterial blood pressure

Question 7

What is the effect of a drop in blood pressure on baroreceptors? What effect does this have on CO?

Answer 7

Decrease in firing rate, drop in parasympathetic stimulation, less inhibitory signals so increased sympathetic stimulation which speeds up the heart and increases stroke volume(reflexes via medullary centers)

Increase in CO since CO=SV X HR

Question 8

Equation for BP

Answer 8

CO X TPR

Question 9

Where do parasympathetic nerves have an effect?

Answer 9

In the heart

Question 10

Where do sympatheric nerves have an effect?

Answer 10

In the heart (increased contractility)

In arterioles and veins

Question 11

What effect does increased sympathetic discharge have on circulation? (4)

Answer 11

Heart:
Increased HR
Increased contractility

Kidneys:
Increased splanchnic/renal vasoconstriction

In lower limbs:
Vasoconstriction

Question 12

How does BP increase with sympathetic stimulation?

Answer 12

BP = CO X TPR

Increase in cardiac contractility –> Increase in HR and SV therefore increase in CO

Vasoconstriction of arterioles –> Increase in TPR

Vasoconstriction of veins –> Increased EDV therefore increased SV therefore increased CO

Question 13

What is the effect on sympathetic discharge to veins?

Answer 13

Increased stroke volume by:

Increased venous tone
Increased venous pressure
Increased venous return
Increased ventricular filling
Increased EDV

Question 14

What happens if any of the mechanisms fail when standing up?

Answer 14

Faint –> horizontal position , blood goes back to the brain

Question 15

Difference bn increased hydrostatic pressure and haemorrhage

Answer 15

Increased hydrostatc pressure: reduction n effective circulating blood volume
Haemorrhage: reduction in actual circulating blood volume

Question 16

Responses to haemorrhage

Answer 16

Decreased baroreceptor firing rate, increased HR and increased Heart contractility (helps maintain CO), organ specific vasoconstriction (increase TPR)

Question 17

Which is more effective, hydrostatic pressure or oncotic pressure? Net movement of fluid?

Answer 17

Hydrostatic pressure, net movement of fluid out of the blood vessels into tissues

Question 18

How does the balance bn hydrostatic and oncotic pressure change in haemorrhage?

Answer 18

Net movement of fluid into the blood to preserve pressure.

Question 19

What is autotransfusion?

Answer 19

Net movement of fluid into the blood to preserve pressure.

Question 20

List 3 hormones that are released to preserve pressure

Answer 20

Aldosterone
Angiotensin II
ADH/Vasopressin

Question 21

What is the general function of ADH?

Answer 21

Increase h2o retention

Question 22

What is the general function of Angiotensin II?

Answer 22

Decrease renal blood flow and vasoconstriction

Question 23

What is the general function of Aldosterone?

Answer 23

Increase Na/H2O retention

Question 24

How much percentage of blood should be lost before tissues go into shock?

Answer 24

> 30%

Question 25

When replacing fluid loss why should you consider not warming the patient?

Answer 25

Vasodilation –> further drop of blood pressure

Question 26

What happens to TPR while exercising and why?

Answer 26

Decreases
Because vessles in muscle dilate to supply more blood to the muscle because of increased metabolism and increased O2 usage

Question 27

What is active hyperemia?

Answer 27

the increase in organ blood flow that is associated with increased metabolic activity of an organ or tissue

Question 28

Explain the pre-programmed patterns associated with exercise

Answer 28

anticipation of exercise sends a sensory signal (afferent input) to the medullary cardiovascular center
switch on sympathetic nervous system, switch off parasympathetic nervous system
Increased HR, increased contractility, vasoconstriction

Question 29

Which organs are going to be controlled by the medulla and which are not?

Answer 29

GIT/ kidney - vasoconstriction therefore reduced blood flow, direct compensatory response
Skin - decreased sympathetic activity, body has to be cooled down therefore vasodilation

Not controlled:
Skeletal muscle - not controlled because it has its own local control - vasodilaton
Heart and Lungs also under local control

Question 30

3 responses to exercise

Answer 30

Local - vasodilating
Central - muscle chemoreceptors
preprogrammed pattern

Question 31

Where does blood flow increase in response to exercise and what is the effect?

Answer 31

Increased blood flow to heart
Increased blood flow to skeletal muscle
Increased blood flow to the skin

Decrease in TPR

Question 32

Where does blood flow decrease in response to exercise and what is the effect?

Answer 32

Increased blood flow to GIT
Increased blood flow to abdomen
Increased blood flow to other tissues

Increase in TPR

Question 33

Net effect on TPR after exercising?

Answer 33

Decrease

Question 34

How do you compensate for a decreased TPR when exercising?

Answer 34

Skeletal muscle pump really effective during exercise, increased venous return, increased stroke volume, increased CO since

BP = CO X TPR

Question 35

Equation for CO

Answer 35

CO = SV X HR

Question 36

What is driving up CO?

Answer 36

Sympathetic nervous system (medulla): Increased SV and Increased HR
Skeletal muscle pump: Increased SV
Increased venous return –> Increased contractility –> Increased SV

Question 37

What can decrease CO?

Answer 37

Increase hydrostatic pressure in muscle vessels

Sweating - loss of water and salts

Question 38

When exercising what predominates? Vasoconstriction or vasodilation?

Answer 38

Vasodilation