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MCAT - Chap 7: Cardiovascular System

Transmission of Cardiac Impulse
Sinoarterial node (SA node) in the right atrium
--> SA node usually hits faster than a regular heartbeat, but the parasympathetic vagus nerve slows the contractions down
Pathway of the electrical signal in the heart
Parasympathetic nervous system --> vagus nerve --> SA node --> AV node --> [bundle of His = conductive fibers] --> [Purkinje fibers = conductive fibers]
How to cross capillary walls (4)
1. pinocytosis
2. diffusion or transport through capillary cell membranes
3. movement through pores in the cells called fenestrations
4. movement through the space between the cells
Oxygen saturation of hemoglobin depends on what? (3)
1. carbon dioxide pressure
2. pH
3. temperature of blood
Bohr shift
shift in oxygen dissociation curve due to pH
Carbon dioxide is carried by the blood in three forms
1. physical solution
2. bicarbonate ion
3. carbamino compounds
What does carbonic anhydrase do?
regulates bicarbonate ion formation
-exists inside red blood cells
-sodium bicarbonate moves into the red blood cell
-chlorine moves out of the cell (chlorine shift)
What type of tissue is blood?
Connective tissue:
-cells AND matrix
What is hematocrit?
percentage of blood by volume of red blood cells
What is blood plasma?
Plasma = matrix component

Contains: water, ions, urea, ammonia, proteins
Important proteins: albumin, immunoglobins, clotting factors
What does albumin do?
-transport fatty acids and steroids
-regulate osmotic pressure
What do immunoglobins do?
Immunoglobins ARE antibodies
What is fibrinogen?
A clotting factor in the blood
What is blood without fibrinogen?
Where are most plasma proteins made?
Liver! Horray!
Define: Erythrocytes, Leukocytes, Platelets
Erythrocytes: red blood cells --> bags of hemoglobin, they have no nucleus, no organelles, expendables, after about 120 days, they burst, usually in the spleen, trying to squeeze through tiny capillaries or in the liver

Leukocytes: white blood cells --> have organelles, no hemoglobin, all different types of leukocytes come from stem cells in the blood marrow, they lose their nucleus in the marrow, then lose their organelles in the 1-2 days, also expendable, generally a longer life span then RBC (much longer sometimes, depending on what type of white blood cells they are)
What are some granular leukocytes?
1. neutrophils
2. eosinophils
3. basophils

--> these guys live for DAYS
--> function non-specifically against all infectious agents
--> die once the infection is gone
What are platelets all about?
-small portions of membrane-bound cytoplasm torn from megakaryocytes

--> megakaryocytes stay mainly in the bone marrow

-platelets avoid healthy endothelium, and stick to damaged endothelium

-half-life of about 8-12 days
what are some agranular leukocytes?
1. monocytes
2. lymphocytes
3. megakaryocytes

--> these guys live for YEARS
--> function specifically against certain infections, so they form the bulk of the body's memory
Coagulation process, the generals
starts with the plaetelets, includes plasma proteins prothrombin and fibrin.

More on that pathway:
1) lots of coagulation factors form complex called protrobin activator
2) protrombin activator catalyzes the conversion of prothrombin (plasma protein) --> thrombin (enzyme)
3) Thrombin causes fibrinogen to form fibrin threads that attach to platelets and form a tight plug
--> blood clot formation
Causative agents of inflammation
1. histamine
2. prostagladins
3. lymphokines
Chain of events when an infectious agent enters cells
1. skin & digestive defenses (innate immunity)
2. macrophages, widely in circulation
3. neutrophils, drawn by chemicals, move into cells via diapedesis
4. monocytes, also drawn by chemicals, also move in via diapedesis
Eosinophils work mainly against what?
parasitic infections
Basophils work mainly how?
Basophils are primarily agents of an inflammatory reaction
Two types of acquired immunity
1. humoral or B-cell immunity
2. cell-mediated or T-cell immunity
Humoral or B-cell immunity details
Cell-mediated or T-cell immunity details