Module 5: Cardivascular Function And Regulation During Exercise

Question 1

What are the functions of the cardiovascular system?

Answer 1

Transportation of oxygen, energy substrate, and hormones to the muscle tissue, and waste products

Question 2

What are the three major CV adjustments to acute exercise?

Answer 2

1. Cardiac output (Q) is increased
2. Q is redistributed throughout the body
3. Tissues adjust the rate of O2 removal from the blood

Question 3

What must be maintained with regards to the CV system?

Answer 3

Driving pressure

Question 4

Describe the pathway in which blood flows throughout the heart:

Answer 4

Pulmonary veins -> left atrium and through the mitral (AV - regulate flow within the heart between the atria and ventricle) valve -> left ventricle and through the aortic (SL - regulate flow out of the heart into the pulmonary and systemic circulation) valve -> blood is systemically circulated and utilized by the muscle tissue and returns via the inferior vena cava -> right atrium and through the tricuspid (AV) valve -> right ventricle and through the pulmonary (SL) valve -> pulmonary artery and the blood is then delivered to the lungs

Question 5

What sounds are produced by the closing AV and SL valves?

Answer 5

AV: Lub
SL: Dub

Question 6

Describe the cardiac conduction system:

Answer 6

1. SA node (hearts pacemaker located in the right atrium) initiates the contraction signal which is sent to the atria causing it to contract, and the AV node
2. AV node delays this signal (allows the atria to completely empty and maximize ventricular filling), relays the signal from the atria to the ventricles and the AV bundle
3. AV bundle relays signal further - travels along the interventricular septum where it eventually splits up into the right and left bundle branches, sends signal toward the apex of the heart
4. Purkinje fibres - terminal branches of the right and left bundle branches, they are spread throughout the entire ventricle wall and work to stimulate ventricular contraction

Question 7

What are the variables associated with an ECG of the cardiac conduction system:

Answer 7

Atrial depolarization (P wave): occurs when the signal is travelling from the SA node to the AV node - ventricular filling
Atrial repolarization occurs between the P and QRS
Ventricular depolarization (QRS complex): occurs when the signal is spread from the AV bundle to the Purkinje fibers causing ventricular contraction
Ventricular systole occurs between QRS and ST
Ventricular repolarization (ST segment)

Question 8

What is the cardiac cycle?

Answer 8

All the events that occur between successive heartbeats
Two main phases which cause changes in pressure and volume:
1. Systole (contraction - eject blood from the ventricles)
2. Diastole (relaxation - ventricular filling)

Question 9

How does the cardiac cycle look at rest?

Answer 9

HR = 75 bpm, cycle = 0.8s (60/75)
Systole: 0.3s (40%)
Diastole: 0.5s (60%)

Question 10

How does the cardiac cycle look during exercise?

Answer 10

HR = 150 bpm, cycle = 0.4s (60/175)
Systole: 0.25s (60%)
Diastole: 0.15s (40%)

Logically, when your exercise, you need blood ejected faster so you have less time for ventricular filling. Thus, systole composes 60% of the cycle and diastole is only 40% (flipped from rest)

Question 11

What are the four phases that compose the cardiac cycle?

Answer 11

1. Ventricular filling - diastole (relaxation)
   Blood is going through our atrium to the ventricles via the AV valve (mitral and tricuspid), SL valves (aortic and pulmonary) are both closed, atrial contraction
   Increase in volume of blood, increase in pressure
2. Isovolumetric contraction - systole (contraction)
   The volume of blood in the ventricle is not changing - both AV and SL valves are closed, ventricles are starting to contract and the pressure is starting to build up
   N/c in volume of blood, increase in pressure
3. Ventricular ejection - systole (contraction)
   SL valves (aortic and pulmonary) open due to increased pressure, blood is ejected out of the heart
   Decrease in volume of blood, increase in pressure
4. Isovolumetric relaxation - diastole (relaxation)
   All of the blood has been ejected, both AV and SL valves close, and the pressure goes down
   N/c in volume of blood, decrease in pressure

Question 12

Define EDV (preload):

Answer 12

The volume of blood in the ventricles at the end of diastole
At rest for an untrained individual = ~100 mL

Question 13

Define SV:

Answer 13

The volume of blood ejected from the ventricles per beat
At rest for an untrained individual = ~60 mL

Question 14

Define ejection fraction:

Answer 14

The volume of blood that is actually being ejected from the EDV
EF = SV/EDV
EF = 60/100
EF = 60%

Question 15

What is the effect of exercise on ventricular volumes?

Answer 15

EDV increases : less time for filling, but still more blood in the ventricle at end of diastole, heart is more effectively getting blood in

SV increases take advantage of inc diastolic volume and eject MORe blood with every beat, so ESV goes down as well

^ Frank starling law: As a result of inc venous return -> inc EDV -> inc stretch on the walls -> inc force of contraction -> inc SV

decrease ESV eject more with each beat(less blood left in heart)

Question 16

What mechanism promotes venous return to the heart?

Answer 16

Contraction of skeletal muscles squeezes veins and promotes venous return to the heart

Question 17

How do you calculate cardiac output (Q) at rest? What are some normative values for untrained and trained males and females at rest?

Answer 17

Q = HR (beats/min) x SV (mL/beat)

Untrained male
Q = 75 x 80 -> 6000 mL/min or 6 L/min

Untrained female
Q = 75 x 60 -> 4500 mL/min or 4.5 L/min

~5 L/min is the normative value that we can use

Trained male:
Q = 55 x 110 -> 6050 mL/min or 6 L/min

Trained female:
Q = 55 x 80 -> 4400 mL/min or 4.5 L/min

SV increases due to increased EDV and ejection fraction

Question 18

How do you calculate cardiac output during maximal exercise? What are some normative values for untrained and trained males and females during maximal exercise?

Answer 18

Q max = HR max x SV max
HR max = fixed (220-age)
SV max = semi-adjustable (genetics and training can alter it)

Untrained male
Q = 200 x 100 -> 20 L/min

Trained male
Q = 200 x 140 -> 28 L/min

Untrained female
Q = 200 x 80 -> 16 L/min

Trained female
Q = 200 x 120 -> 24 L/min

Question 19

What are the ways in which SV increases during exercise?

Answer 19

1. Increased venous return (muscle pumps) -> Increased EDV (preload) -> Increased SV
2. Increased left ventricular contractility (Increased NE and EPI) -> increased SV
3. Decreased afterload (aortic pressure) via vasodilation -> increased SV

Question 20

how can heart rate be used to prescribe training intensity and determine maximal fitness?

how can we use HR to predict VO2 max(what are some assumptions?

Answer 20

can be prescribed in different zones of % of Max Heart Rate
1. Recovery Zone: 50% or less

2. Fat Burning zone: 50%-65%
   -burn highest relative fat but not absolute
3. Target Heart Rate Zone: 65%-85%
4. Anaerobic Threshold Zone: 85-100%

• HR is directly proportional to exercise intensity
• Maximal HR(HR max): highest HR achieved in an all-out effort to volitional fatigue: slight decline with age
  220-age (NOT EVERYONE) but still most common
  208-(0.7 x age in years)

Assumptions:
1. linear (direct) relationship bw Hr and workload
2: Hr max= 220-age

Procedure:
1. measure Hr at more than 2 submax workloads
2. extrapolate line to predicted HR max
3. Determine predicted VO2 max

what happens?
Stage 1: 30 W
Stage 2: 60 W
Stage 3: 90 W

HR increases ad workload (W) increases

plot it on graph
more trained = lower Hr at given workload =more fit-higher predicted maximal workload or Vo2 MAX