Ch 13/14 Cardiovascular Physiology (Day 1) Flashcards
Main functions of the cardiovascular system
- Transport of respiratory gases, nutrients, and wastes
- Communication/Regulation—hormones & temperature
- Defense/Protection–clotting and immunity
Cardiovascular System Components
Blood—fluid medium
–>Cells and plasma
Heart—pump (primary motive force)
–>Septum divides left and right halves
Blood vessels—conduit/delivery system (plumbing)
- -> Arteries, arterioles, capillaries, postcapillary venules, veins
- ->Pulmonary and systemic circulation
Associated w/cardiovascular system:
Lymphatic System: return fluid that has leaked out back to cardiovascular system, immune function
–>Lymphatic vessels, lymphoid tissues, lymphatic organs
(spleen, thymus, tonsils, lymph nodes)
Diffusion
–>simple method for moving things down a concentration gradient
equation for diffusion time: t=x2/2D
(t=time, x=distance you want molecule to move, D=diffusion coefficient)
Diffusion is fast over short distances, but slow over greater distances
Why is a cardiovascular system important?
-most important function of the circulatory system is
bulk transport [overcomes limitations of diffusion]
Overview of Cardiovascular system
- pulmonary circulation: blood from body to heart to lungs
- systemic circulation: blood from heart to body back to heart
–>right and left hearts are in series – so output from each side matches the other
Arrangement of Circulation
- arrangements of circulation to different organs is parallel (exception: GI series in liver: liver has two sources of blood, straight from heart and from GI tract)
- -> this arrangement prevents blood flow changes in one organ from affecting flow to others
-lungs get 100% of cardiac output, rest of organs share the 100%
Blood
the fluid medium
- Average adult volume: 5 liters
- 45% formed elements (platelet cells); 55% plasma (by volume): platelets are not real cells, fragment elements
- ->blood plasma + formed elements + RBCs + “buffy coat” (platelets + WBCs)
- Arterial blood – leaving the heart; bright red, OXYGENATED
[except for pulmonary artery - taking deoxygenated blood –> lungs] - Venous blood – entering the heart; dark red, DEOXYGENATED
[except for pulmonary veins - carrying oxygenated blood back to the heart]
Plasma volume
regulated to maintain BP
[CV/renal/hypothalamo-anterior pituitary-adrenal axis]
Plasma osmolality
regulated to maintain solute (Na+) concentration
[CV/renal/hypothalamo-posterior pituitary axis]
plasma constituents
water ions organic molecules (AA, proteins, glucose, lipids, nitrogenous waste) trace elements/vitamins gases (CO2, O2)
What is the most important plasma protein?
Albumins
source: liver
functions: Major contributors to colloid osmotic pressure of plasma (holds fluid-determines volume), carriers for various substance
Formed Elements (cells)
RBCs (erythrocytes)
WBCs
Platelets (cell fragments –> clotting)
RBCs
“Erythrocytes”: Oxygen Transport
- Small, flattened, biconcave discs, no nuclei, no mitochondria
- 120-day life span
- % of blood volume (hematocrit)—index of O2 carrying capacity of blood
- heme: binds to iron –> makes red color
–>Anemia: abnormally low hematocrit or hemoglobin count
Blood Count
+/- 58% blood plasma
>1% white cells
42% red cell packed volume
WBCs
“Leukocytes”
- Granular: have granules (ex. neutrophils, eosinophils, basophils)
- Agranular: no granules (ex. monocytes, lymphocytes)
- Have nuclei, mitochondria
- Move in amoeboid fashion—can move from capillaries, post-capillary venules into tissues (diapedesis/extravasation)
- Major role in innate & adaptive immune systems & inflammatory response
Platelets
“thrombocytes”
- Smallest formed element, fragments of megakaryocytes
- No nuclei
- Short-lived (5−9 days)
- Clot blood with several other chemicals and fibrinogen
- Release serotonin (stimulates vasoconstriction)
Hematopoiesis
development of blood cells and platelets—begins in bone marrow
Thrombopoiesis
production of platelets
-The cytokine, thrombopoietin stimulates growth of megakaryocytes and maturation into platelets
Erythropoiesis
production of red blood cells
- Red bone marrow produces about 2.5 million RBCs/sec
- Stimulated by the hormone erythropoietin (EPO) from kidneys in response to low blood O2
- Most iron is recycled from old RBCs (by macrophages), the rest comes from the diet
Leukopoiesis
production of white blood cells
- Begins in bone marrow, final development requires maturation in lymphoid tissues (lymph nodes, tonsils, spleen, thymus)
- As cells differentiate, they express membrane receptors to CYTOKINES, which have both general and specific effects in determining the final cell subtype:
- –Multipotent growth factor-1
- –Interleukin-1
- –Interleukin-3
- —-> above three are all general effects on all subtypes
- –Granuloctye colony stimulating factor (G-CSF) —>neutrophils
- –Granulocyte-monocyte colony-stimulating factor (GM-CSF)–> monos, eos
Cytokines
- Signaling molecule (peptide), usually, but not exclusively, secreted by cells of the immune system (e.g. EPO comes from kidney).
- Have effects on development and function of leukocytes and other cell types.
- May operate as paracrine or autocrine (paracrine & endocrine signals)
Hemostasis
Cessation of bleeding when a blood vessel is damaged.
Damage exposes collagen fibers to blood, producing:
- Formation of platelet plug
- Vasoconstriction (less blood able to leak out)
- Formation of fibrin protein web mature clot (wraps around platelets)
Blood Clotting: platelets and blood vessel walls
Intact endothelium secretes prostacyclin and nitric oxide, which:
- Vasodilate
- Inhibit platelet aggregation
- -> makes surface slippery, prevents platelets from sticking
And CD39, which:
- Breaks down ADP into AMP and Pi to inhibit platelet aggregation further
- ->preserves “slippery” nature
Normal intact endothelium:
- expresses/secretes platelet inhibitory factors
- barrier function—prevents exposure of platelets to sub-endothelial, extracellular matrix molecules
- ->act as if nothing is there, platelets just float by
Damaged Endothelium
exposes collagen
- Platelets bind to exposed collagen and Von Willebrand Factor which hold them in place
- -> ACTIVATION –> GET STICKY
- Activated platelets recruit MORE platelets and form plug by secreting: (Platelet release reaction)
- –ADP (sticky platelets)
- –Serotonin (vasoconstriction- act upstream to close down arterioles so less blood can be lost)
- –Thromboxane A2 (sticky platelets and vasoconstriction)
- Activated platelets also activate & bind to soluble plasma clotting factors
Formation of Platelet Plug and Clot
- Platelets bind to fibrin –> wraps around and reinforces mass of aggregated platelets which effectively plugs the defect
- RBCs become entwined in the plug–>mature, solid clot
Coagulation Cascade
–>don’t need to know specifics, BUT… both intrinsic and extrinsic pathways converge on formation of THROMBIN (converts fibrinogen –> fibrin which aids in cross linkage of platelets in blood clotting)
Clot formation/dessolution
- thrombin involved in BOTH (depends on which enzymes activates it)
- as vessel heals, factors are released which digest fibrin polymers
