Conduction System of the Heart
Explain the mechanism of parasympathetic effects on heart rate
Acetylcholine is the neurotransmitter released, and it binds to muscarinic cholinergic receptors on the SA node. The binding of ACh to these receptors opens K+ channels. K+ flows out of the cell (down its concentration gradient) and hyperpolarizes the cell. This reduces the rate and strength of contraction.
Sinoatrial node
Also called the SA node, these nerve fibers are embedded in the right atrium and have autorhythmicity that begins the electrical signal through the heart that results in a heartbeat.
Wolf-Parkinson-White Syndrome
An "accessory" electrical pathway that allows the signal to circulate around the heart muscle rapidly. Results in supraventricular tachycardia, which means the heart beats too fast due to the atrial pathway not slowing down appropriately before depolarizing the ventricles. ∙Treatment is *radiofrequency ablation.*
Bundle Branches
Branches off the AV Bundle/Bundle of His that conduct impulses to the left and right ventricles
Atrioventricular Node
Nerve cells located at the atrioventricular junction in the heart. They receive the electrical signal from the SA node and pass it on to the AV Bundle.
ectopic focus
any region of spontaneous firing other than the SA node. Very common and usually benign. Exacerbated by fatigue, stress, caffeine.
heart block
arrhythmia in which there is interference with the normal transmission of electric impulses from the SA node to the Purkinje fibers
P Wave
atrial depolarization
ECG/EKG
electrocardiogram
parasympathetic effect on the heart
slows down heartrate and decreases force of contraction. Carried via the vagus nerves.
Purkinje fibers
specialized conductive fibers located within the walls of the ventricles
Atrioventricular Bundle (Bundle of His)
specialized muscle fibers connecting the atria with the ventricles and transmitting electrical impulses between them. It's #3 in this picture.
QRS complex
ventricular depolarization
T wave
ventricular repolarization
