ANSWERS 100% PASS
Transport of material - ✔✔gases, nutrients, waste,
communication, defense against pathogens,
temperature homeostasis
Heart is a - ✔✔pump
Atria - ✔✔receives blood returning to heart
Ventricles - ✔✔pump blood out
Left side - ✔✔oxygenated blood
Right side - ✔✔deoxygenated blood
Blood vessels - ✔✔- Veins, arteries, and capillaries
- Pulmonary and systemic circulation
- Portal system joins two capillary beds in series.
Pulmonary circulation - ✔✔from right side (leave right ventricle and go to lung)
(deoxygenated)
Blood - ✔✔cells and plasma
The heart is composed mostly of - ✔✔myocardium (cardiac muscle)
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,Which 2 sets of heart valves ensure one-way flow - ✔✔Atrioventricular valves
Semilunar valves
Atrioventricular valves - ✔✔- Between atria and ventricles
- Tricuspid valve on the right side
- Bicuspid valve, or mitral valve, on the left side
Semilunar valves - ✔✔• Between ventricles and arteries
• Aortic valve
• Pulmonary valve
The heart is encased within . . . - ✔✔the pericardium (a membranous fluid-filled sac)
During ventricular contraction, the AV valves - ✔✔remain closed to prevent blood flow
backward into the atria.
During ventricular relaxation, the semilunar valves - ✔✔prevent blood that has entered
the arteries from flowing back into the ventricles
Contractile cells - ✔✔Striated fibers organized into sarcomeres
Autorhythmic cells, or pacemakers - ✔✔- Signal for contraction
- Smaller and fewer contractile fibers compared to
contractile cells
Cardiac Muscle - ✔✔Do not have organized sarcomeres
Myocardial muscle cells are - ✔✔branched, have a single nucleus, and are attached to
each other by specialized junctions known as intercalated disks.
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,Intercalated disks contain - ✔✔desmosomes that transfer force from cell to cell, and gap
junctions that allow electrical signals to pass rapidly from cell to cell.
Cardiac Muscle versus Skeletal Muscle - ✔✔• Smaller and have single nucleus per fiber
• Branch and join neighboring cells through
intercalated disks
- Desmosomes allow force to be transferred
- Gap junctions provide electrical connection
• T-tubules are larger and branch
• Sarcoplasmic reticulum is smaller
• Mitochondria occupy one-third of cell volume
Cardiac Muscle Contraction Can Be Graded
Action potential starts with the heart pacemaker cells - ✔✔- Voltage-gated L-type Ca2+
channels in the cell
membrane open (extra cellular calcium
contributes 10%)
- Ryanodine receptors open in the sarcoplasmic
reticulum (SR)
- Calcium binds to troponin
- Crossbridge cycle as in skeletal muscle
Cardiac Muscle Contraction Can Be Graded - ✔✔• Relaxation:
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, - Calcium removed from cytoplasm: back into the SR with Ca2+ ATPase and out of the
cell through the
Na+-Ca2+ exchanger (NC)
• Force generated is proportional to number of active
crossbridges
- Determined by how much calcium is bound to troponin
• Sarcomere length affects force of contraction
Figure 14.9 EC coupling in cardiac muscle - ✔✔1. Action potential enters from adjacent
cell.
2. Voltage-gated Ca2+ channels open. Ca2+ enters cell.
3. Ca2+ induces Ca2+ release
through ryanodine receptor channels (RyR).
4. Local release causes Ca2+ spark.
5. Summed Ca2+ sparks create a Ca2+ signal.
6. Ca2+ ions bind to troponin to initiate contraction.
7. Relaxation occurs when Ca2+ unbinds from troponin.
8. Ca2+ is pumped back into the sarcoplasmic reticulum for storage.
9. Ca2+ is exchanged with Na+ by the NCX antiporter.
10. Na+gradient is maintained by the Na+-K+-ATPase.
Myocardial Action Potentials - ✔✔Vary
Myocardial contractile cells - ✔✔- Depolarization due to Na+ entry
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