Lecture 34

Question 1

Role of autonomic nervous system in exercise?

Answer 1

Mediates cardiovascular adjustments to meet metabolic demands.

Question 2

Two divisions of ANS?

Answer 2

Sympathetic and parasympathetic nervous systems.

Question 3

Parasympathetic withdrawal effect at exercise onset?

Answer 3

Increases HR, contractility, stroke volume, and cardiac output.

Question 4

Sympathetic activation during exercise?

Answer 4

Increases HR, contractility, and stimulates adrenal medulla to release epinephrine.

Question 5

Sympathetic vasoconstriction purpose?

Answer 5

Redistributes cardiac output by constricting vessels in non-exercising tissues.

Question 6

Functional sympatholysis?

Answer 6

Reduced vasoconstriction in active muscle due to metabolites (exercise hyperemia).

Question 7

Is sympatholysis global?

Answer 7

No; sympathetic activity still restricts flow to help maintain BP.

Question 8

Impact of autonomic failure on exercise?

Answer 8

Patients cannot maintain even light exercise loads.

Question 9

Three major neural mechanisms for exercise autonomic control?

Answer 9

Central command, exercise pressor reflex, arterial baroreflex.

Question 10

Cardiac regulation at exercise onset?

Answer 10

Immediate HR increase via parasympathetic withdrawal.

Question 11

When is parasympathetic withdrawal most important?

Answer 11

At low workloads; less after HR exceeds 90–100 bpm.

Question 12

When does sympathetic cardiac stimulation dominate?

Answer 12

Increasingly with higher exercise intensity.

Question 13

Peripheral regulation primary controller?

Answer 13

Sympathetic nervous system.

Question 14

Resting vasomotor tone maintained by?

Answer 14

Rhythmic discharge of sympathetic nerves.

Question 15

Peripheral sympathetic response timing?

Answer 15

Delayed 30–60 seconds after exercise onset.

Question 16

Reason for delayed sympathetic response?

Answer 16

Metabolite buildup + stimulation of muscle afferents.

Question 17

Early sympathetic redistribution targets?

Answer 17

Skin and kidney to redirect blood to muscle.

Question 18

Exercise intensity and sympathetic activity?

Answer 18

Sympathetic activity increases with exercise intensity.

Question 19

Exercise duration effect on sympathetic activity?

Answer 19

Longer duration → progressively increased sympathetic outflow.

Question 20

Central command definition?

Answer 20

Feedforward descending signals initiating both movement and autonomic activation.

Question 21

Evidence for central command?

Answer 21

HR and BP increase with imagined exercise or hypnosis (page 28).

Question 22

Central command primary effect?

Answer 22

Parasympathetic withdrawal → rapid HR increase.

Question 23

Exercise pressor reflex definition?

Answer 23

Feedback from muscle afferents to cardiovascular centres.

Question 24

Group III afferents function?

Answer 24

Mechanoreflex; activated immediately at exercise onset.

Question 25

Group IV afferents function?

Answer 25

Metaboreflex; delayed response as metabolites accumulate.

Question 26

Metaboreflex impact during steady-state exercise?

Answer 26

Strong increase in sympathetic activity.

Question 27

Key muscle metabolites activating metaboreflex?

Answer 27

K+, adenosine, nitric oxide, prostaglandins, arachidonic acid.

Question 28

Arterial baroreflex role?

Answer 28

Regulates BP during exercise.

Question 29

Why must baroreflex reset?

Answer 29

To maintain BP control at elevated exercise pressures.

Question 30

What causes baroreflex resetting?

Answer 30

Combined influence of central command + exercise pressor reflex.

Question 31

Summary: What drives HR increase at onset?

Answer 31

Parasympathetic withdrawal via central command and mechanoreflex.

Question 32

Summary: HR regulation during increasing intensity?

Answer 32

Parasympathetic withdrawal at low intensities; sympathetic activation at higher intensities.

Question 33

Summary: What redistributes cardiac output?

Answer 33

Sympathetic vasoconstriction + functional sympatholysis.

Question 34

Sympathetic latency explanation (30–60 s)?

Answer 34

Time required for metabolite accumulation to activate Group IV afferents.

Question 35

Why maintain baroreflex function during exercise?

Answer 35

Ensures perfusion pressure to all organs, not just working muscles.