D2. Cardiorespiratory exercise- experiments

Question 1

Summary

Answer 1

Feed-Forward Control
Feedback Control
Neural Circuitry in Central Command
Metabolic Control of Blood Flow

Question 2

1. Krogh & Lindhart 1913

Answer 2

Six subjects, 3 trained, sudden exertions

Immediate and rapid increase in pulse rate when starting exercise

One subject told higher load but didn’t happen

Ventilatory response same as with higher load

Cortical irradiation

Question 3

2. Donald 1968

Answer 3

Sympathetic system’s role in exercise CV response

9 greyhounds (6 normal, 3 denervated hearts)

Denervated → slower HR increase

Propranolol blocked HR increase → adrenaline-mediated

Could use cardio-selective blocker + ventilation comparison

Question 4

3. Boulton 2016

Answer 4

Microneurography of left peroneal nerve MSNA

Electrically stimulated contractions vs dorsiflexion

Electric does not activate central command

MSNA elevated in dorsiflexion, not electrical

Electric contraction still stressful

Question 5

4. Amman 2011

Answer 5

Central motor drive via EMG

Intrathecal fentanyl to block Group III/IV

Fentanyl increased CMD but lowered BP and HR

Reduced time to exhaustion

Question 6

5. Thornton 2002

Answer 6

Hypnosis of exercise during PET

SMA, PMA, DLPFC activated

SMA alone active with voluntary breathing

DLPFC key in central command

Exercise in PET scanner difficult

Question 7

6. Eldridge 1981

Answer 7

Decorticate/decerebrate cats

Decerebrate showed spontaneous locomotion

GABA antagonist or hypothalamus stim induced locomotion

V and BP rose with locomotor activity

Question 8

7. Koba 2022

Answer 8

Optogenetics: RVM → mesencephalic locomotor region

Fos increased post-exercise in these neurons

Light excitation ↑ HR/BP

Chloride channels into MLR-RVLM → inhibition

Wheel running + light ↓ pressure during exercise only

Question 9

8. Alam & Smirk 1937

Answer 9

Thigh occlusion with sphygmomanometer cuffs

Exercise ↑ BP maintained for ~3 min post-exercise

Validated in arm – likely metabolic factor

Question 10

9. McCloskey & Mitchell 1983

Answer 10

Anaesthetised decerebrate cats

Ventral root electrical excitation mimicked Alam & Smirk

Isotonic KCl injection similar effect

Anaesthetic abolished dorsal root activity

Depressed CV response – needs electrophysiology

Question 11

10. Wasserman 1975

Answer 11

Chemoreceptor-denervated patients

Normal ventilation but reduced hyperpnoea above anaerobic threshold

Controls had no asthma

No HR measurements

Question 12

11. Potts 2003

Answer 12

Decerebrate rat with arterial perfusion

Forelimb electric stimulation ↑ HR

Forelimb afferents ↓ baroreflex

Inhibited by GABA A antagonist into caudal NTS

Optogenetics could be used

Question 13

12. Groucher 1990

Answer 13

8-phenyltheophylline adenosine antagonist

Anaesthetised cats, obturator nerve stim

EM flow probe for blood flow

40% decrease with adenosine antagonist

Anaesthetic CV depression

Question 14

13. Zhao 2020

Answer 14

Mouse papillary muscle, small artery pressurised

Pinacidil → vasodilation via KATP

SMC-specific KATP ablation did not stop effect

Kir2.1 conductance ↑ with potassium

Kir2.1 on coronary ECs → hyperpolarisation

Question 15

14. White 1998

Answer 15

Minipigs trained 1, 3, 8, 16 weeks

Capillary ↑ by week 3

Arteriolar growth by week 16

Higher CO

No mechanism – ECs in culture suggested