Respiratory Sinus Arrythmia

A Respiratory Sinus Arrhythmia is a change in the heart rate that corresponds to the frequency
of respiration. 

Typically the heart rate will increase during inspiration due to stimulation of the sympathetic 
nervous system during this time, and the heart rate will decrease during expiration due to 
stimulation of the parasympathetic nervous system. The rhythmic change in heart rate can be 
attributed to varying levels of the neurotransmitters acetocholine (sympathetic) and norepinephrine
(parasympathetic) at nerve endings. However, parasympathetic activity influences heart rate by RSA
much more so than sympathetic activity. 

Respiratory Cardiac Arrythmia is influenced by two factors. A reflexive factor, which consists of 
arteriole response to sympathetic stimulation alters arterial blood pressure; baroreceptors and
stretch receptors in the lungs alter the heart rate accordingly in a feedback manner. Also, the 
Bainbridge Reflex plays a major role in the alteration of heart rate as a result of respiration.

The second factor that controls the heart rate with respect to respiration is the central nervous 
system, which connects the heart and lungs through the cardiac/vagal center of the medulla. This has
been demonstrated experimentally. It is known that Respiratory Sinus Arrythmia is the result of both
reflexes in which the heart responds to the respiratory cycle and control from the central nervous
system.

Sample Problems:

1. Which of the following contributes to a Respiratory Sinus Arrythmia?
	A. the Bainbridge Reflex
	B. the Baroreceptor Reflex
	C. the Respiratory Center in the Medulla
	D. Stretch Receptors in the lungs
	E. All of the above

Answers:

1. E

For more information on this topic, please refer to Berne & Levy , pages 90-3

Also, check out the following links that may be helpful:

• Report: Experiment in Effects of forced and spontaneous respiration on ECG
• Research Abstract: Vagally Mediated Baroreflex Control of Heart Rate
• And, as always, if you have questions, or if you can suggest a helpful link, please e-mail me.

No!
Please don't make me go to any of those pages!
I want to go somewhere completely different!

This page was written by David Huber , a student in this course.

BME 403 Pages maintained by the T.A., Douglas Miles.