9-30b acute and chronic responses to aerobic exercise

Question 1

What contributes to increase in HR?

Answer 1

Increased B1 receptor activation on SA node by sympathetic stimulation and circulating catecholamines

Question 2

What accounts for the differences in resting HR and the initial HR response?

Answer 2

parasympathetic withdrawal

first 100 bpm

Question 3

For a SCI vs. sedentary, what accounts for difference in differences in resting HR and the initial HR response?
What accounts for the similar maximum heart rate?

Answer 3

Higher resting HR in HTx b/c no parasympathetic innervation.
Withdrawal of parasympathetic innervation explains the early rise in SCI.
both only have circulating catecholamines so they cannot reach max HR

Question 4

For a Htx vs. Sedentary, what accounts for the difference in heart rate response in sedentary v. athlete?

Answer 4

Lack of innervation in HTx causes 1) higher

resting HR, 2) slowed initial response, 3) blunted max HR response

Question 5

What accounts for the difference in heart rate response in sedentary v. athlete?

Answer 5

Lower resting and submax HR in athlete due
to ↑ parasympathetic activity/↓ sympathetic activity at all
submaximal workloads. Max HR is similar.

Question 6

Explain differences in SV b/w SCI vs. HTx

Answer 6

SCI has no venous m. pump to augment venous return w exercie

Question 7

Explain differences in SV b/w Sedentary vs. HTx

Answer 7

Initial similar increase due to intact venous muscle pump/↑ preload/Frank-Starling mechanism. Later increase in sedentary due to sympathetic innervation, which increases contractility. HTx has no direct innervation.

Question 8

Explain differences in SV b/w Sedentary vs. Athlete

Answer 8

Athlete has larger ventricular volume and slower HR at all submaximal workloads, allowing longer filling time and a greater SV

Question 9

Explain differences b/w SCI and HTx for CO

Answer 9

Lack of muscle pump blunts SV increase in SCI, and therefore CO. Also, VO2 max limited due to less activated muscle mass

Question 10

Explain CO differences b/w Sedentary and HTx

Answer 10

Initially similar due to similar SV response. But blunted HR response in HTx due to lack of sympathetic innervation of heart limits later increases

Question 11

Explain CO differences b/w Sedentary and athlete

Answer 11

Similar at low workloads. However, athlete can achieve

higher CO because SV is much higher than sedentary at all workloads

Question 12

Compare Athlete vs. Sedentary a-vO2 differences

Answer 12

Maximal oxygen extraction is similar. Higher CO in
athlete allows him to achieve same VO2 with less
oxygen extraction.

Question 13

What is MAP equal to

Answer 13

CO * TPR

diastolic pressure plus 1/3 of pulse pressure

Question 14

what is pulse pressure equal to?

Answer 14

systolic - diastolic

Question 15

What is pulse pressure directly related to?

Answer 15

SV
↓ stroke volume due to ischemia→ ↓ pulse pressure
↑ stroke volume during exercise → ↑ pulse pressure

Question 16

What is pulse pressure inversely related to?

Answer 16

vessel compliance

Arterial stiffening with aging and arteriosclerosis → ↑ pulse pressure

Question 17

Explain differences in SBP for SCI vs. HTx

Answer 17

Lack of a muscle pump in SCI blunts the SV response, and therefore the SBP response.

Question 18

Explain differences in SBP for HTx vs. Sedentary

Answer 18

SV, and therefore SBP, doesn’t increase as much in HTx

because of lack of sympathetic innervation

Question 19

Explain differences in SBP for Athlete vs. sedentary

Answer 19

Athlete has greater increase in SV, so greater SBP

response

Question 20

What is SV affected by?

Answer 20

Preload
Afterload
Contractility
Sympathetic stimulation
Circulating catecholamines

Question 21

What is SV affected by?

Answer 21

Preload
Afterload
Contractility
Sympathetic stimulation
Circulating catecholamines

Question 22

What mainly affects DBP?

Answer 22

CO, primarily HR

Total Peripheral Resistance (TPR)

Question 23

Compare Athlete to HTx for DBP

Answer 23

DBP falls in the athlete
because the fall in TPR
is greater than the
increase in CO. TPR
falls due to
vasodilation in skeletal
muscle via vasodilator
metabolites produced
by muscle.

In HTx, DPB is elevated at rest because resting HR is
higher than the athlete. During exercise, DBP stays
the same or increases slightly. This indicates that
the fall in TPR is balanced by the increase in CO

Question 24

What are the effects of training?

Answer 24

↑ VO2 max
• ↑ Maximal CO
– ↓ HR at rest and
submaximal workloads due
• ↑ parasympathetic/↓
sympathetic activity
– ↑ SV due to
• ventricular remodeling
(larger chamber)
• Slower HR = longer time for
diastolic filling
• No change or slight ↑ in
max a-v O2diff
↓ myocardial oxygen
demand during exercise
– ↓ Rate Pressure Product
• ↓ Resting blood pressure