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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?
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