Lecture: Heart Flashcards
Differentiate the pulmonary circuit and the systemic circuit.
the pulmonary circuit stems from the right side of heart and sends blood to the lungs for gas exchange, while the systemic circuit stems from the left side of the heart and sends blood to all the organs of the body
Differentiate the circulatory system and the cardiovascular system. What are the components of each and how do their functions vary?
Circulatory system: heart, blood vessels, blood
functions: transportation, protection, regulation
Cardiovascular system: heart and blood vessels
functions: transportation of blood
Describe the location and weight of the heart.
in the thoracic cavity, in the mediastinum
< 1 lb
Describe the structure/layers of the pericardium.
from outer to inner: parietal pericardium --fibrous layer --serous layer visceral pericardium (a.k.a. epicardium) pericardial activity filled with pericardial fluid
What are the 5 functions of the pericardium?
1) Lubrication
2) Reduce friction
3) Protection
4) Expansion of heart
5) Prevents excessive expansion
Describe the structure/layers of the heart wall.
epicardium --coronary blood vessels myocardium --cardiac muscles (left thicker than right) endocardium --covers valves --continuous with blood vessels
Describe the functions of the 2 structural components of the myocardium.
1) cardiac muscle tissue
- -arranged in spiral or circular bundles; links all parts of the heart together
2) Fibrous CT skeleton
- -provides structural support, anchors cardiac muscle fibers, limits the spread of AP’s b/c it is a nonconductor of electricity
Describe cardiac muscle tissue, and compare it to skeletal muscle. Comment on:
- -nucleus,
- -mitochondria,
- -myofibrils,
- -sarcoplasmic reticulum,
- -transverse tubules.
- -single, central nucleus
- -mitochondria are 25% volume of cell
- -myofibrils & sarcomeres similar to skeletal muscle
- -SR is less developed & contains no terminal cisternae (calcium obtained from ECF)
- -T-tubules are larger than in skeletal muscle
Describe intercalated discs and their 3 distinctive features not found in skeletal muscle.
1) interdigitating folds: p. membrane folds up to “lock on” to adjoining cells
2) mechanical junctions: fascia adherens and desmosomes
3) electrical junctions: gap junctions; form a “functional synctium”
Describe the metabolism of cardiac muscle.
aerobic metabolism
vulnerable to oxygen deficiency
not prone to fatigue
adaptable to organic fuels (fatty acids, glucose, etc.)
can change metabolic pathways (ex. can use lactic acid)
What special type of cell enables the cardiac conduction system?
autorhythmic cells
- modified cardiac muscle cells
- function independently; influences by ANS & hormones
- function as pacemakers for the conduction pathway
What is unique about the RMP of the sinoatrial (SA) node?
cells of the SA node have an unstable RMP, which starts at about -60 mV and drifts upward, showing a gradual depolarization called the pacemaker potential
What are the 5 steps of action potentials in the sinoatrial (SA) node?
1) slow Na inflow causes a pacemaker potential to reach a threshold of -40 mV
2) fast, voltage-gated calcium channels open and Ca flows in from ECF
3) AP peaks slightly above 0 mV
4) fast K channels open and K leaves the cell
5) when repolarization is complete, K channels close and pacemaker potential starts over
What are Purkinje fibers?
nervelike processes that distribute excitation through the ventricular myocardium; fastest, supply papillary muscles
What is the RMP of an individual contractile cardiac myocyte?
-90 mV
