Lesson 1 Flashcards
What are the heart’s three general functions?
- Electrical - specialized cells have the properties of
creating electrical impulses - Mechanical - cardiac muscle cells have the property of
contracting - Endocrine - atrial muscle cells secrete Atrial Natriuretic Peptide (ANH) and B-type Natriuretic
Peptide (BNP)
What are 5 properties of myocardial cells?
- Automaticity – the ability to initiate electrical impulses
- Conductivity – the ability to transmit electrical impulses from one cell to another
- Excitability – the ability to respond to electrical impulses
- Extensibility – the ability to stretch
- Contractility – the ability to contract
Where is the anterior interventricular sulcus?
This groove runs from the superior to inferior
surface. This sulcus is the demarcation line of the left and right ventricles.
Where is the posterior
interventricular sulcus?
The anterior interventricular sulcus continues around the apex to the posterior surface and becomes the posterior interventricular sulcus.
Where is the atrioventricular sulcus?
- At the base of the heart, this groove goes around the heart. This sulcus is also known as the corona (crown) sulcus, as it
resembles a crown around the heart. - Within the heart, the atrioventricular valves and
cardiac skeleton are found in the atrioventricular sulcus.
What is the crux cordis?
Posteriorly, the point at which the interatrial sulcus, the posterior interventricular sulcus
and the atrioventricular sulcus intersect.
Where is the cardiac skeleton found?
Within the interventricular
septum
What is the purpose of the cardiac skeleton?
- Provide an attachment for the atrial and ventricular muscles
- Anchor the 4 valves of the heart
- Electrically insulate the myocardium of the ventricles from the atria
What/where is the right fibrous trigone or central fibrous body of the cardiac skeleton?
- The triangular formation, between the aortic valve and medial parts of the tricuspid valve opening
- The right fibrous trigone is the strongest portion of the cardiac skeleton
Where is the left fibrous trigone of the cardiac skeleton?
It is smaller in size and is formed between the aortic valve and anterior leaflet of the mitral valve.
Where is the tricuspid annulus of the cardiac skeleton?
The part of the cardiac skeleton that serves as an attachment for the tricuspid valve.
Where is the bicuspid annulus of the cardiac skeleton?
The part of the cardiac
skeleton that serves as an attachment for the bicuspid (mitral) valve.
Where are the aortic annulus and pulmonary annulus of the cardiac skeleton?
These are strong collagenous tissues which support the aortic and pulmonary valves.
Where is the membranous interventricular septum of the cardiac skeleton?
This is the inferior extension of the right fibrous trigone that is anchored to the interventricular septum.
What are the 4 main components of the cardiac skeleton?
- Membranous Interventricular Septum
- Annulus
- Left Fibrous Trigone
- Right Fibrous Trigone (Central Fibrous Body)
Describe the arrangement of cardiac muscles.
- The muscle fibers of the heart are arranged in a spiral fashion with the vortex at the apex.
- With this arrangement of the fibers, expulsion of blood from the chambers is very efficient.
What are the three layers of the heart?
- Epicardium
- Myocardium
- Endocardium
Describe the epicardium.
- The outermost layer of the heart and is composed of simple squamous cells lined with collagen, elastic fibers, and other connective tissue.
- has a rich blood supply because the coronary arteries run along its surface.
- also known as the visceral layer of the pericardium.
What are the three main
characteristics of cardiac muscle?
- Branched
- Joined at complex junctions called intercalated discs, which form a cellular network
- Contain centrally located nuclei
What are desmosomes?
Contains adherence, which holds cells together.
What are gap junctions?
Membrane channels that allow ions to pass from one cell to another.
What is a sarcomere?
The distance between two successive Z-lines.
Describe the make-up of myocardial cells.
- Myocardial cells consist of about 300-700 myofibrils
- There are about 200-1000 myosin filaments in each myofibril and 6 actin filaments around each myosin filament
What are the A-band and I-band?
- The A-band is the dark portion of the sarcomere, where actin and myosin overlap
- The lighter portion only contains actin and is called the I-band
What is the sarcolemma?
A thin membrane that encloses the muscle cell
What are Transverse tubules (T-tubules)?
Deep invaginations of the sarcolemma that cross myofibrils and allow electrical impulses to quickly enter the cell
What is the sarcoplasmic reticulum?
Regulates calcium ion concentration within
the muscle cell. Calcium ions are essential to contraction.
What are the terminal cisternae?
Enlarged areas of the sarcoplasmic reticulum surrounding the T-tubules that serve as reservoirs for calcium ions
Actin filaments have 2 regulatory proteins; what are they?
- Tropomyosin - is a
double-stranded and helical-coiled protein - Troponin is a globular protein which has 3
subunits:
1. TnC – a calcium binding subunit
2. TnI – subunit that inhibits muscle contraction
3. TnT – subunit that connects the troponin complex to tropomyosin and actin
Describe the structure and function of the endocardium.
- innermost layer of tissue which lines the heart
- composed of endothelial cells that rest on a thin layer of
connective tissue known as the basement membrane - lines the chambers, creating a slick environment, which decreases the resistance of blood flow and prevents clot formation
- valves of the heart are also formed from the endocardium
- prevents ions and other components of the blood from interfering with the sensitive ionic composition
of the myocardium
