Myocardium

Definition

The myocardium is the muscular middle layer of the heart wall, responsible for the heart's pumping action. It is composed of cardiac muscle tissue that contracts rhythmically to circulate blood throughout the body.

5 Must Know Facts For Your Next Test

1. The myocardium is the thickest layer of the heart wall, comprising the bulk of the heart's muscular structure.
2. Cardiac muscle cells within the myocardium are interconnected, allowing for the coordinated contraction of the heart.
3. The myocardium is supplied with oxygenated blood through the coronary arteries, which branch off from the aorta.
4. Damage or dysfunction of the myocardium, as seen in conditions like myocardial infarction (heart attack), can impair the heart's ability to effectively pump blood.
5. The myocardium's contractile properties are regulated by the autonomic nervous system, which modulates heart rate and force of contraction.

Review Questions

• Describe the role of the myocardium in the overall structure and function of the heart.
  • The myocardium is the middle and thickest layer of the heart wall, composed of specialized cardiac muscle tissue. It is responsible for the heart's rhythmic contractions, which drive the circulation of blood throughout the body. The myocardium's contractile properties are essential for the heart's pumping action, as it generates the force needed to propel blood out of the ventricles and into the pulmonary and systemic circulations.
• Explain how the myocardium is supplied with oxygenated blood and the potential consequences of impaired blood flow to this layer.
  • The myocardium is supplied with oxygenated blood through the coronary arteries, which branch off from the aorta. Disruption of blood flow to the myocardium, as seen in conditions like myocardial infarction (heart attack), can lead to damage or death of cardiac muscle cells within the affected area. This impairs the myocardium's ability to contract effectively, compromising the heart's pumping function and ultimately leading to reduced blood flow to the body's tissues.
• Analyze the role of the autonomic nervous system in regulating the contractile properties of the myocardium and discuss how this regulation contributes to the heart's overall function.
  • The autonomic nervous system, consisting of the sympathetic and parasympathetic divisions, plays a crucial role in modulating the contractile properties of the myocardium. The sympathetic nervous system stimulates the myocardium, increasing the heart rate and force of contraction, while the parasympathetic nervous system (via the vagus nerve) has the opposite effect, slowing the heart rate. This dynamic regulation of the myocardium's contractility allows the heart to adjust its pumping capacity to meet the body's changing demands for blood flow, ensuring that vital organs and tissues receive an adequate supply of oxygenated blood.

Related terms

Endocardium: The innermost layer of the heart wall that lines the heart's chambers and valves.

Epicardium: The outermost layer of the heart wall, also known as the visceral pericardium, that provides protection and support to the heart.

Cardiac Muscle: The specialized muscle tissue found in the myocardium that is responsible for the heart's rhythmic contractions.