Notes
Blood
- Blood is plasma (about 55%) and formed elements (RBCs, WBCs, platelets). Hemoglobin in RBCs carries oxygen; EPO controls RBC production. Hemostasis involves vascular spasm, a platelet plug and coagulation.
- ABO blood types depend on antigens on RBCs; type O is the universal donor for red cells and AB the universal recipient.
Heart and vessels
- The right heart pumps to the lungs; the left heart pumps to the body. Valves prevent backflow. The SA node sets the pace; the AV node delays the signal; Purkinje fibers spread it.
- Cardiac output = heart rate times stroke volume. Arteries carry blood away from the heart, veins return it, capillaries exchange materials. Blood pressure depends on cardiac output and peripheral resistance, and is regulated by baroreceptors.
Lymph and immunity
- Lymph returns fluid to blood. Innate defenses are fast and nonspecific; adaptive immunity uses B cells (antibodies) and T cells and creates memory. Vaccines produce active immunity.
Topics in this unit
Each topic has its own short notes and practice.
Practice
Blood goes through the pulmonary circuit before returning to the left side for the systemic circuit.
The AV node (and other conduction tissue) has a lower intrinsic rate and can act as a backup pacemaker.
The vessel constricts first, platelets form a plug, and coagulation builds the fibrin clot.
HR = CO divided by SV = 4,800 divided by 60 = 80.
Type A people have anti-B antibodies, which bind to B antigens on transfused cells.
Active immunity involves the person's own adaptive response and memory.
Free response
Write your answer first, then open the scoring guide.
Free-response question
A 55-year-old man has a blood pressure reading of 150/95 at three visits. He has high cholesterol, and an ultrasound shows plaque in his arteries.
(a) Identify the systolic and diastolic pressures and the pulse pressure, and state whether the reading is normal.
Show the answer and scoring guide
Systolic is 150 mm Hg and diastolic is 95 mm Hg. Pulse pressure is 150 minus 95 = 55 mm Hg. The reading is high (hypertension).
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(b) Explain how narrowing of arteries by plaque can raise blood pressure.
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Plaque (atherosclerosis) reduces vessel diameter and elasticity, which increases peripheral resistance. Higher resistance raises blood pressure and makes the heart work harder.
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(c) If a coronary artery becomes blocked, explain what happens to the heart muscle.
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Heart muscle supplied by that artery is deprived of oxygen and can die, causing a myocardial infarction. Cardiac muscle regenerates poorly, so the area heals by scar tissue.
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