The Heart's Conduction System
The heart's conduction system is responsible for initiating and coordinating the heartbeat. This intricate system ensures the heart functions efficiently and rhythmically.
Components of the Conduction System
The conduction system consists of specialized cardiac muscle cells that generate and transmit electrical impulses throughout the heart.
Highlight: The sino-atrial node (SAN), located in the right atrium wall, is known as the heart's natural pacemaker, initiating each heartbeat.
The main components of the conduction system include:
- Sino-atrial node (SAN)
- Atrio-ventricular node (AVN)
- Bundle of His
- Left and right bundle branches
- Purkinje fibers
Vocabulary: Auto-rhythmic cells are specialized cardiac cells capable of generating their own electrical impulses.
The electrical activity of the heart can be measured and recorded using an electrocardiogram (ECG).
Example: On an ECG, the P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization.
Nervous System Control of Heart Rate
The autonomic nervous system plays a crucial role in regulating heart rate through its sympathetic and parasympathetic branches.
Definition: The medulla oblongata is the part of the brain stem that controls involuntary functions, including heart rate.
- Sympathetic stimulation increases heart rate through the release of noradrenaline.
- Parasympathetic stimulation decreases heart rate through the release of acetylcholine.
Highlight: During stress, the sympathetic nervous system activates the adrenal glands to release adrenaline, further increasing heart rate.