Autonomic Nervous System and the Heart

Study Notes

The heart receives both sympathetic and parasympathetic innervation.
The sympathetic nervous system increases heart rate, force of contraction, and the conduction of action potentials.
The parasympathetic nervous system reduces heart rate and conduction through the AV node.
At rest, both systems are active, but the parasympathetic system dominates.
Respiration affects the heart rate.
An isolated heart beats at 100 beats per minute.
Adding sympathetic activity increases the rate to 120 beats per minute.
Adding parasympathetic activity decreases the rate to 70 beats per minute.
The heart, at rest, receives both sympathetic and parasympathetic activity, but parasympathetic is dominant.

The table shows sympathetic and parasympathetic innervation of different parts of the heart and arteries.
(Note: the table content of sympathetic/parasynthetic innervation is provided from the image)

Heart rate is recorded using a pressure transducer.
The subject takes a deep breath and submerges their face in ice-cold water.
The subject holds the position for as long as possible (usually about 20 seconds).
Heart rate is recorded throughout the dive.
The heart rate decreases during the dive, for example: from 88 (before) to 68 (during the dive) beats per minute.

During respiratory sinus arrhythmia, the heart rate increases or decreases during inspiration.
This is due to changes in vagal tone and sympathetic activity.
Consequences of RSA affect gaseous exchange in the lungs.
Changes in heart rate are due to mechanisms like the Bainbridge reflex (aka atrial reflex)

Approximately what is the normal heart rate at rest in a human?
At what rate does an isolated human heart beat at normal body temperature(NB. An isolated heart has no functional nerves running to it.)?
At rest, is there sympathetic nerve activity or parasympathetic nerve activity?
During the dive, which nervous system is activated?
Which neurotransmitters and cardiac receptors are involved in the decreased heart rate during the dive response?
What possible advantages does this parasympathetic reflex provide to diving animals?

Heart receives sympathetic and parasympathetic innervation.
Sympathetic nerves increase heart rate, conduction & contraction.
Parasympathetic nerves decrease heart rate, conduction & contraction.
Active at rest but Parasympathetic dominates.
Respiration affects heart rate.
Denervated heart (transplant) - any ANS control?
- Denervated heart shows increased sensitivity to adrenaline.
- Denervation increases the number of beta receptors.