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Regulation of Heart Rate

The Autonomic Nervous System in Cardiovascular Control

The SA node controls HR, therefore stimuli that influence HR act through

the SA node

PNS-Parasympathetic Nervous System

PNS carried in Vagus nerve fibers to SA node and AV node

Postganglionic PNS fibers use neurotransmitter ACh (acetylcholine)

SNSaccelerates

HR, PNSdecelerates

HR via influences on theSA node firing rate (and also conduction velocity in the heart)

Changes in PNS activity can therefore cause HR to

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Regulation of Heart Rate

The Autonomic Nervous System in Cardiovascular Control

SNS carried in Cardiac accelerator nerves to SA and AVnodes

NE working through Beta adrenergic receptors increasesthe rate of spontaneous depolarization of SA node cells (increases

HR)

SNS

alsoinnervates the cardiac myocytes to affect the strength of the

Postganglionic SNS fibers use neurotransmitter NE (norepinephrine

SNS-Sympathetic Nervous System

Changes in SNS activity can therefore cause HR to

or

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Regulation of Heart Rate

The Autonomic Nervous System in Cardiovascular Control

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Regulation of Heart Rate

Factors increasing or decreasing the SA node firing rate and the conductionvelocity within the heart

Increasing Decreasing

Sympathetic stimulation Parasympathetic stimulation

Circulating catecholamines (epinephrine,Norepinephrine)

Ischemia/hypoxia

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Regulation of Heart Rate

The Autonomic Nervous System in Cardiovascular Control

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Regulation of Heart Rate

Progressive

PNS to heart in proportion to exercise intensity

(especially from rest to exercise intensity associated with ~10bpm HR)

These responses during exercise are critical to support the

C.O. and redistribution of C.O.

so that skeletal muscle blood flow can be enhanced and muscle can receive2

During recovery from exercise

VO2= HR * SV * (CaO2

CvO2)

VO2

= CO * (CaO2 CvO2)

Why does HR have to

during dynamic exercise?

How does HR

during exercise?

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Figure 9.25 from Powers and Howley. Changes in cardiac output, stroke volume and

heart rate during the transition rest to

Transitions from Rest to Exercise and Recovery

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Regulation of Heart Rate

HR response to exercise

Workload (indexed to VO2)

rest

Intensity of exercise and training/disease status effects

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Three questions about HR that relate to

Workload (indexed to VO2)

rest

Is HR

maxdifferent across groups?

Is resting HR different across groups?

Intensity of exercise and training/disease status effects

Is HR at a given submaximal workloaddifferent across groups?