Regulation of the Heartbeat

Nervous Stimulation of heart

• controlled by autonomic nervous system

• sympathetic nerves increase HR/SV 

• parasympathetic nerves decrease HR/SV

autonomic nervous system

• sympathetic neural pathways

• parasympathetic neural pathways

Sympathetic neural pathways

excites/speeds up functions

Parasympathetic neural pathways

inhibits/slows functions

Epinephrine/norepinephrine

• hormones secreted by adrenal glands during periods of stress/excitement

• speed up the heart rate 

• “fight or flight”

• increases endocrine regulation of heart rate

Conduction system

• ensures that the cardiac chambers are stimulated to contract in a coordinated manner and a specific rhythm

• various hormones can speed up or slow down the pace of the heart by acting on SA node fibers

Sinoatrial node (pacemaker) location

right atrial wall

Sinoatrial node (pacemaker) function

• initiates heartbeat and sets basic pace for heart rate 

• sends action potential to both atria causing them to contract

Atrioventricular node location

interatrial septum

Atrioventricular node function

picks up action potential from SA node and passes it to the atrioventricular bundle

Atrioventricular bundle location

interventricular septum

Atrioventricular bundle function

picks up action potential from AV node and passes it to the right and left bundle branches

right and left bundle branches location

interventricular septum

right and left bundle branches function

picks up action potential and passes it to conduction myofibers

conduction myofibers (purkinje fibers) location

ventricular myocardium

conduction myofibers (purkinje fibers) function

picks up action potential from bundle branches and passes it to ventricular myocardial cells, causing ventricles to contract