31 Questions
What is the function of the atrium in the heart?
To act as a primer pump for the ventricle
Which ventricle pumps blood through the pulmonary circulation?
Right ventricle
What is the function of the tricuspid valve?
To prevent backflow of blood from the ventricle to the atrium
What causes the AV valves to close?
Backward pressure gradient
What is the difference between AV valves and semilunar valves?
AV valves are thinner and lighter, while semilunar valves are heavier
What is the function of the chordae tendineae?
To attach the papillary muscles to the AV valves
During which phase of the cardiac cycle do the semilunar valves close?
Diastole
What is the main function of gap junctions in cardiac muscle fibers?
To allow free diffusion of ions and nutrients
What is unique about the T-tubules in cardiac muscle compared to skeletal muscle?
They are 5 times larger in diameter
What is the function of the fibrous skeleton of the heart?
To separate the atrial and ventricular syncytium
What is the specialized conductive system that connects the atrial and ventricular syncytium?
The AV bundle
What is the term for the network of cardiac muscle cells that can be excited simultaneously?
Syncytium
What is the main function of the heart?
To pump blood throughout the body
How do action potentials normally spread between the atrial and ventricular syncytium?
Through the AV bundle
What is the difference between the atrial and ventricular syncytium?
The atrial syncytium is separated from the ventricular syncytium by fibrous tissue
What is the weight of the heart?
250-350 gr
What is the result of the interconnected nature of cardiac muscle fibers?
Action potentials rapidly spread to all cells
What is the direction of the heart in the thoracic cavity?
From right superior to left inferior
What is the function of the intercalated disc?
To connect the heart chambers
What is the function of the gap junction?
To connect the heart cells
What is the result of depolarization in the heart?
Increase in intracellular Ca2+ concentration
What is the function of the heart valves?
To prevent backflow of blood
What is the location of the heart in the thoracic cavity?
Behind the sternum, to the left of the midline
What is the function of the chorda tendineae in the heart?
To prevent the valves from bulging backward during ventricular contraction
What is the main component of the myocardium?
Striated muscular cells
What is the function of the pericardium?
To lubricate the surface of the heart during contraction and relaxation
Which nerve has a high distribution in the atrioventricular (AV) node?
Left vagus nerve
What is the purpose of the intercalated discs in cardiac myocytes?
To connect two adjacent muscle cells
What is the correct order of cardiac wall thickness?
LV>RV>LA>RA
What is the function of the gap junctions in cardiac myocytes?
To allow rapid diffusion of ions
Which of the following is a characteristic of cardiac myocytes?
Striated muscle cells
Study Notes
Heart Physiology Overview
- Heart physiology involves the study of the heart's electrical activity, electrocardiography, mechanical function, and overall electromechanical function.
Heart Anatomy and Histology
- The heart is a double muscular pump with a conic shape, located in the thoracic cavity between the lungs and slightly to the left of the midline.
- The heart weighs around 250-350 grams and has four chambers: right atrium, left atrium, right ventricle, and left ventricle.
Heart Chambers
- The heart has two separate pumps: right heart for pulmonary circulation and left heart for systemic circulation.
- Each pump has an atrium and a ventricle, with the atria serving as weak primer pumps for the ventricles.
Heart Valves
- The heart has four valves: tricuspid, mitral, aortic, and pulmonary valves.
- The atrio-ventricular (AV) valves (tricuspid and mitral) prevent backflow of blood from ventricles to atria during systole.
- The semilunar valves (aortic and pulmonary) prevent backflow from aorta and pulmonary arteries to ventricles during diastole.
Function of Heart Valves
- The AV valves close when a backward pressure gradient pushes blood backward and open when a forward pressure gradient forces blood in the forward direction.
- The semilunar valves require rapid backflow for a few milliseconds to close.
Function of Papillary Muscles and Chordae Tendineae
- Papillary muscles attach to the vanes of the AV valves by chordae tendineae.
- These muscles contract when ventricular walls contract, pulling the valve vanes inward to prevent bulging backward during ventricular contraction.
Heart Layers
- The heart has three layers: pericardium (outermost), myocardium (middle), and endocardium (innermost).
- The pericardium is a thin fibrous sac with a small amount of fluid that lubricates the heart.
- The myocardium is the thickest layer, composed of striated muscular cells.
- The endocardium is the innermost layer, composed of endothelial cells.
Nerves of the Heart
- The heart is innervated by the autonomic nervous system, with sympathetic and parasympathetic nerves.
- Sympathetic nerves innervate the atria, ventricles, SA node, and AV node.
- Parasympathetic nerves (vagus nerves) have a higher distribution in the nodes (SA and AV) and a poorer distribution in the ventricles.
Intercalated Disc and Gap Junction
- The intercalated disc is the connection site between two adjacent muscle cells, necessary for atrial and ventricular syncytiums.
- Gap junctions are special structures inside the intercalated discs that allow rapid diffusion of ions, oxygen, and nutrients.
Atrial and Ventricular Syncytium
- The heart is composed of two syncytiums: atrial and ventricular.
- The atrial syncytium constitutes the walls of the two atria, and the ventricular syncytium constitutes the walls of the two ventricles.
- The atria are separated from the ventricles by fibrous tissue that surrounds the atrioventricular valvular openings.
Test your knowledge of heart anatomy, electrical activity, and mechanical function. Covering electrocardiography, heart chambers, and valves.
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