Ch. 13/14 Cardiovascular (CV) Physiology Flashcards
What are the functions of the circulatory system?
- Transport of respiratory gases, nutrients, and wastes
- Communication/regulation of hormones and temperature
- Defense/protection - clotting and immunity
CV 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, post capillary venules, veins
- -pulmonary and systemic circulation
Lymphatic system
- -lymphatic vessels, lymphoid tissues, lymphatic organs (spleen, thymus, tonsils, lymph nodes)
- -return fluid leaked from CV system back to CV system
- -immune functions/system
Why do we need a CV system?
Bulk transport! Diffusion has limitations over long distances
Diffusion is fast over short distances, but slow over greater distances
What is diffusion?
Simple method for moving things down a concentration gradient
Equation: t = x^2/2D
(x = distance traveled, D = diffusion coefficient [different for each solute])
–note: time varies w/ the square of the distance
Overview of CV System
Right and left hearts are in series - so output from each side matches the other
Pulmonary circulation: blood from body –> heart –> lungs
Systemic circulation: blood from heart –> body
Arrangement of circulation to different organs is?
Parallel
Exception: GI in series w/ liver
Parallel arrangement prevents blood flow changes in one organ from affecting flow to others
W/ every heartbeat lungs get 100% of cardiac output; all other organs share 100% cardiac output
Blood
Fluid medium
Average adult volume: 5L
45% formed elements (cells/platelets); 55% plasma (by volume)
Arterial blood: leaving heart, bright red, oxygenated [except for pulmonary artery]
Venous blood: entering the heart, dark red, deoxygenated [except for pulmonary veins]
In a centrifuged blood sample, what is the layer in between the blood plasma and formed elements?
“Buffy coat”
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
Plasma is made up of lots of things, ranging from water, ions, organic molecules (proteins, AAs, fibrinogen), trace elements/vitamins, and gases (CO2 and O2)
Plasma Proteins make up what percentage of total plasma?
7-8% of plasma
What is the most important plasma protein?
Albumin
Made in liver (lack of it during liver failure)
Fxn: major contributions to colloid osmotic pressure of plasma, carriers for various substances
Holds fluid in CV system, determines volume
Formed Elements (cells)
RBCs
Platelets
WBCs
–lymphocytes, monocytes, neutrophils, eosinophils, basophils
RBCs
“Erythrocyte”
Oxygen transport
Flattened, biconcave discs, NO NUCLEI OR MITOCHONDRIA
120-day lifespan
% of blood volume (hematocrit) - index of O2 carrying capacity
Anemia: abnormally low hematocrit or HB count
Heme (contains iron molecule) carries O2
–each heme can carry a maximum of 4 oxygen molecules
Blood Count
58% plasma volume
WBCs
“Leukocytes”
Granular (granulocytes): neutrophils, eosinophils, basophils
Agranular: monocytes, lymphocytes (T and B cells)
Have nuclei, mitochondria
Move in amoeboid fashion - can move from capillaries, post-capillary venules into tissues (diapedesis/extravasation)
Major role in innate and adaptive immune systems and inflammatory response
Platelets
“Thrombocytes”
Smallest formed element, fragments of megakaryocytes
No nuclei
Short-lived (5-9 days)
Clot w/ several other chemicals and fibrinogen
Release serotonin (stimulate vasoconstriction)
Hematopoiesis
Development of blood cells and platelets - begin in bone marrow
Erythropoiesis
Production of RBCs
Red bone marrow produces about 2.5 million RBCs/sec
Stimulated by erythropoietin (EPO) from kidneys in response to low blood O2
Most iron recycled from old RBCs, the rest comes from diet
Thrombopoiesis
Production of platelets
The cytokine, thrombopoietin stimulates growth of megakaryocytes and maturation into platelets
Leukopoiesis
Production of WBCs
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 subtype:
- -multipotent growth factor-1 (general effects on all subtypes)
- -interleukin-1 (general effects on all subtypes)
- -interleukin-3 (general effects on all subtypes)
- -granulocyte colony stimulating factor (G-CSF) - neutrophils
- -granulocyte-monocyte colony-stimulating factor (GM-CSF) - monocytes, eosinophils
Cytokine
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 autocrine, paracrine, and endocrine signals
Blood Clotting
Hemostasis: cessation of bleeding when a blood vessel is damaged
Damage exposes collagen fibers to blood, producing:
a) Formation of platelet plug
- -platelets stick to collagen fibers –> activate –> stick to each other
b) Vasoconstriction
c) Formation of fibrin protein web –> mature clot
Platelets and Blood Vessel Walls
Intact endothelium secrete prostacyclin and nitric oxide, which:
- -vasodilate
- -inhibit platelet aggregation (keeps them from sticking)
AND CD39, which:
- -breaks down ADP into AMP and Pi to inhibit platelet aggregation further
- ->ADP makes endothelial cells sticky; converting ADP to AMP and Pi retains stickiness of platelets
Intact Endothelium
Expresses/secretes platelet inhibitory factors
Barrier function - prevents exposure of platelets to sub-endothelial extracellular matrix molecules
Damaged Endothelium
Exposes collagen
Platelets bind to exposed collagen and Von Willebrand Factor which hold them in place
Activated platelets recruit more platelets and form plug by secreting (platelet release reaction - all starts w/ platelets)
- -a) ADP (sticky platelets)
- -b) Serotonin (vasoconstriction - acts upstream to close arteriole so less blood is lost)
- -c) Thromboxane A2 (sticky platelets and vasoconstriction)
Activated platelets also activate and bind to soluble plasma clotting factors
Formation of Platelet Plug and Clot
Platelets bind to fibrin –> reinforces mass of aggregated platelets which effectively plugs the defect
RBCs become entwined in the plug –> solid clot
Coagulation Cascade
Both intrinsic and extrinsic pathways converge on formation of THROMBIN
Thrombin converts fibrinogen to fibrin (aids on cross linkages of platelets in blood clotting)
Clot Formation and Dissolution
Thrombin involved in BOTH
Formation of clot: making fibrin
Dissolution of clot: breakdown of fibrin
As vessel heals, factors are released which digest fibrin polymers
