Lecture 10 - Cardiovascular responses to stress

Question 1

cardiac output equation

Answer 1

heart rate x stroke volume

usually 72 x 0.07 L = 5L/min

Question 2

what is a more ideal measurement than cardiac output?

Answer 2

mean arterial pressure

Question 3

mean arterial pressure equation

Answer 3

cardiac output x total peripheral resistance

Question 4

what is total peripheral resistance

Answer 4

how much vessels are squeezing

Question 5

how does heart regulate itself to respond to changes?

Answer 5

increase preload - increase stroke volume
decrease in preload - decreases stroke volume
preload best measured as EDV

Question 6

how is edv measured?

Answer 6

echo

Question 7

what does a very high preload result in

Answer 7

decrease in stroke volume

Question 8

what can increase the preload?

Answer 8

increase in circulating volume - overhydration/fluid
increase in central venous pressure - increases amount of blood in heart
eg. respiratory pump
decrease in venous compliance
increase in atrial filling or contraction - atrial fibrillation
decreased heart rate - prolongs diastole
increases in aortic or pulmonary pressure

Question 9

Intrinsic regulation in cardiac function is done by what effect?

Answer 9

Bowditch effect

Question 10

What is the bowditch effect?

Answer 10

relationship between heart rate and cardiac performance

Question 11

What does the bowditch effect suggest?

Answer 11

increase in heart rate - increase in force of contraction
decrease in heart rate - decrease in force
high levels of heart rate - eventually leads to a decreased force of contraction

Question 12

How is bowditch independent to frank-starling?

Answer 12

length of the muscle is not affected

Question 13

How does the extrinsic regulation of cardiac activity work?

Answer 13

autonomic - sympathetic and parasympathetic system

Question 14

What does the sympathetic nervous system supply importantly?

Answer 14

the heart, kidneys and the adrenal gland

Question 15

What does the parasympathetic system innervated

Answer 15

innervates the heart but not kidneys or suprarenal glands

Question 16

Sympathetic actions, the direct cardiac effects

Answer 16

positive chronotropy on sa node
positive dromotropy (conduction) on AV node
Positive inotropy (contraction) ventricles and atria
positive lusitropy (relaxation) - ventricles and atria

Question 17

what are the systemic effects of sympathetic system

Answer 17

RAA system

Suprarenal stimulation - catecholamine release

Question 18

increase in chronotropy/ionotropy/preload

Answer 18

causes an increase in cardiac performance up to a certain point and then it will decrease

Question 19

Outline the RAAS

Answer 19

renin from the kidney converts angiotensinogen from the liver to angiotensin 1.
angiotensin 1 is converted to 2 by ACE.
angiotensin 2 acts on suprarenal glands to produce aldosterone (sodium and water retention) and on pituitary to secrete vasopressin (increase vasoconstriction) and acts on kidneys to increase sodium and water retention.

Question 20

what does aldosterone do

Answer 20

causes sodium and water retention

Question 21

what does vasopressin do

Answer 21

promotes water retention by acting on the aquaporins in the collecting duct of the nephrons

Question 22

actions of raas on stroke volume

Answer 22

increases central venous pressure by an increase in circulating fluid and increase in cardiac output

Question 23

What contributes to total peripheral resistance

Answer 23

vasoconstriction, increases BP

Question 24

which direct action on the suprarenal glands causes an increase in heart rate.

Answer 24

catecholamine release in the blood. leads to production of adrenaline by the suprarenal glands which acts on the kidney to secrete renin and so on…
adrenalin - vasoconstrictor - effects peripheral resistance
increases heart rate and stroke volume

Question 25

What are the parasympathetic actions

Answer 25

decreased heart rate - chronotropy decreased av conduction - dromotropy decreased atrial contractility - inotropy ventricular contractility - no significant effect raas - no significant effect

Question 26

which parts does the parasympathetic system not have much effect on

Answer 26

ventricular contractility | raas - doesnt act on kidneys or suprerenal glands

Question 27

Where are the baroreceptors located

Answer 27

carotid sinus and aortic arch

Question 28

an increase in arterial pressure will result in

Answer 28

increased baroreceptor firing

Question 29

an increase in baroreceptor firing will cause

Answer 29

a decrease in sympathetic tone and an increase in parasympathetic tone

Question 30

a decrease in baroreceptor firing will cause

Answer 30

an increase in sympathetic and a decrease in parasympathetic tone

Question 31

What happens when someone experiences blood loss?

Answer 31

decrease in central venous pressure, decrease in stroke volume, decrease in cardiac output, decrease in arterial pressure, increase in baroreceptor firing leads to an increase in sympathetic tone, decrease in parasympathetic, increase in vascular resistance and an increase in venous tone.

Question 32

poor urine output is indicative of

Answer 32

lack of blood flow to the kidnets

Question 33

What does giving fluids do to someone with blood loss

Answer 33

increases preload, increases central venous pressure increases stroke volume

Question 34

What does giving too much fluid to a person with blood loss do?

Answer 34

the preload becomes too high above threshold and too much stretch of muscle stroke volume decreases again and decreased cardiac output and mean arterial pressure

Question 35

What does an excess left ventricular pressure do?

Answer 35

back pressure to lungs - increase in alveolar capillary pressure. imbalance in mechanical pressure in alveoli and vessel and tissue compartments which causes pulmonary oedema and enlarged heart

Question 36

normal thoracic diameter

Answer 36

when horizontally measured - around half of the cavity.

Question 37

what sort of treatment would you give for pulmonary oedema and increased blood fluid.

Answer 37

furosemide (diuretics) | too much fluid in system - need to get rid of it. treat rapidly

Question 38

cardiopulmonary testing

Answer 38

exercise ECG, treadmill, metabolic cart, sphygmomanometer, rebreathing bag for non-invasive CO

Question 39

What does VO2 max indicate?

Answer 39

overall function of cardiovascular system, overall heart function, maximum amount of oxygen delivered to the tissues.