Cardiac anatomy regulation of Q, exercise triggers and cardiac response to exercise

Question 1

what is stroke volume?

Answer 1

Preload - afterload

Question 2

What is Q?

Answer 2

Cardiac output

Question 3

What is preload?

Answer 3

the amount of blood in the ventricles before contraction (EDV)

Question 4

what is afterload?

Answer 4

the amount of blood left in the ventricles after contraction (ESV)

Question 5

what is the ejection fraction?

Answer 5

of the initial starting volume how much was ejected?

Question 6

What is the equation for EF?

Answer 6

EF = SV/EDV

Question 7

what is the equation for Q?

Answer 7

Q = HR X SV

Question 8

approximately what is the ejection fraction at rest?

Answer 8

70%

Question 9

what is the shortening fraction?

Answer 9

How much does the chamber reduce in size whilst it contracts

Question 10

Approximately what is the shortening fraction at rest?

Answer 10

35%

Question 11

How does preload affect cardiac output?

Answer 11

How well does the chamber fill prior to the hear beating?

How big is the chamber?

venous return - we want optimal venous return

Question 12

How does afterload affect cardiac output?

Answer 12

How strong are the contractions?

How much resistance was there? A lot of resistance, more will remain in the heart

Question 13

What factor is force directly related to regarding the hearts contractions?

Answer 13

Muscle cross-sectional area (more muscle, stronger contraction)

Question 14

What system is adrenaline released from?

Answer 14

Sympathetic

Question 15

What actions does the autonomic nervous system carry out and give examples?

Answer 15

Subconscious actions in the body e.g. breathing, digestion

Question 16

What actions does the parasympathetic nervous system bring about?

Answer 16

Rest and digest

Question 17

What system is your heart a part of?

Answer 17

Autonomic system

Question 18

what does the parasympathetic nervous system do to heart rate?

Answer 18

Decrease it

Question 19

The PNS is wired from the CNS to where?(3)

Answer 19

SA node
AV node
atrial muscle

Question 20

What does the sympathetic nervous system do to heart rate?

Answer 20

increase HR

Question 21

The SNS is wired from the CNS to where?(3)

Answer 21

SA node
AV node
ventricular muscle

Question 22

Roughly what is a normal heart rate?

Answer 22

~72/min

Question 23

What is a limiting factor of how much the ventricles can fill?

Answer 23

Pericardium

Question 24

What did Stray-gundersen, Circ Res, 1986 find when they studied the hearts of dogs?

Answer 24

pericardectomy in dogs allowed a greater SV and Q and peak VO2

Question 25

what is the frank-starling principle?

Answer 25

increase stretching of myocardial walls will increase strength of contraction

Question 26

what type of muscle does cardiac muscle have similar length-tension properties to?

Answer 26

skeletal muscle

Question 27

what is the cardiac muscle length-tension relationship?

Answer 27

increasing ventricular volume stretches the ventricular muscle towards optimum length. if we over stretch the muscle then the contractile strength starts to break away

Question 28

how does the heart muscle avoid getting to a point where contraction forces decrease

Answer 28

it becomes stiffer

Question 29

what is the typical blood volume of adults?

Answer 29

5L

Question 30

what can reduce blood volume in adults

Answer 30

haemorrhage | dehydration

Question 31

where is blood flow always maintained?

Answer 31

the brain

Question 32

how much blood resides in the veins at rest

Answer 32

two thirds

Question 33

How does the body cope with insufficient blood for maximal exercise?

Answer 33

Blood is shunted away from non-working and towards working muscles to support and sustain that exercise

Question 34

What causes resistance vessels (arterioles) smooth muscle to relax

Answer 34

vasodilators

Question 35

Give me examples of some vasodilators

Answer 35

``` Increase nitric oxide Increase bradykinin Increase prostaglandins Increase K+ Increase Co2 Increase lactate Local decrease in PO2 ```

Question 36

How does an increase in nitric oxide work as a vasodilator?

Answer 36

as we increase the blood flow through the system that will stretch the endothelium and that will stimulate the endothelium to produce nitric oxide which will further allow the vasodilation

Question 37

how do vasoconstrictors work?

Answer 37

Increase SNS activity release NE (norepinephrine) has an effect on a small amount of vasodilation (against what we are trying to achieve here). NE acts on alpha-receptors in smooth muscle to cause constriction

Question 38

What effects are greater? Vasodilation or vasoconstriction?

Answer 38

vasodilation

Question 39

How much blood resides in the venous system at rest?

Answer 39

70%

Question 40

How do we increase venous return?

Answer 40

increase SNS activity constriction of venous smooth muscle venoconstriction

Question 41

How much % of blood shunting occurs through venoconstriction?

Answer 41

20%

Question 42

why do we promote blood flow back to the central circulation?

Answer 42

stop blood pooling

Question 43

what is the most important way the blood comes back

Answer 43

muscular pump

Question 44

how do we enhance various return and why ?

Answer 44

moving - veins embedded within the muscle get squeezed and result in the blood being pushed

Question 45

what happens in the heart after stole has occurred?

Answer 45

the recoil creates a low pressure environment in the ventricles actively sucking blood towards it to promote the filling

Question 46

Why does the heart twist when it beats?

Answer 46

action facilitates the wringing out of the blood

Question 47

How does breating out help push blood back towards the heart?

Answer 47

out increase in thoracic pressure then squeeze the vena cava and helps push blood back towards the heart

Question 48

How does breating in help suck blood back towards the heart?

Answer 48

♣ the pressure drops there is a low pressure in the thorax facilitate blood being sucked up back towards the heart

Question 49

what effects how much blood is left in the heart at the end of contraction?

Answer 49

volume of blood in atrial circulation pressure in aorta at onset at onset of ejection compliance of aorta size of pulmonary/aorta lumen inertial component of the ejecting blood column systemic vascular resistance

Question 50

where does the pressure have to be lower in order to allow the blood to squirt into the valves?

Answer 50

ventricle

Question 51

what are the effects on an increased afterload?

Answer 51

increase preload Stroke volume will be reduced in the acute phase Reduced velocity of contraction and ejection in acute phase Marked increase in myocardial O2 consumption

Question 52

what are mechanoreceptors?

Answer 52

movement changes

Question 53

what are metaboreceptors?

Answer 53

metabolic changes

Question 54

what are baroreceptors?

Answer 54

pressure changes

Question 55

what triggers the CV response? (3)

Answer 55

mechanoreceptors, metaboreceptors, baroreceptors

Question 56

what are metaboreceptors sensitive to?

Answer 56

Increase lactate Increase phosphate Increase prostaglandins Decrease pH

Question 57

where are baroreceptors located?

Answer 57

in walls of the carotid sinus and aortic arch are baroreceptors

Question 58

where are chemoreceptors located?

Answer 58

in the walls of carotid sinus and aortic arch

Question 59

what do chemoreceptors sense?

Answer 59

high levels of CO2 in the blood

Question 60

What is the bainbridge reflex?

Answer 60

Increased cardiac filling elicits tachycardia Increase right atrium filling from increase venous return, Stretch receptors in the right atria and vena cava stretched, Increased firing rate to brain, Brain increases SNS tone, Increase HR and SV