Ch. 13/14 Cardiovascular (CV) Physiology

Question 1

What are the functions of the circulatory system?

Answer 1

1. Transport of respiratory gases, nutrients, and wastes
2. Communication/regulation of hormones and temperature
3. Defense/protection - clotting and immunity

Question 2

CV System Components

Answer 2

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

Question 3

Why do we need a CV system?

Answer 3

Bulk transport! Diffusion has limitations over long distances

Diffusion is fast over short distances, but slow over greater distances

Question 4

What is diffusion?

Answer 4

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

Question 5

Overview of CV System

Answer 5

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

Question 6

Arrangement of circulation to different organs is?

Answer 6

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

Question 7

Blood

Answer 7

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]

Question 8

In a centrifuged blood sample, what is the layer in between the blood plasma and formed elements?

Answer 8

“Buffy coat”

Question 9

Plasma Volume

Answer 9

Regulated to maintain BP [CV/renal/hypothalamo-anterior pituitary-adrenal axis]

Question 10

Plasma Osmolality

Answer 10

Regulated to maintain solute (Na+) concentration [CV/renal/hypothalamo-posterior pituitary axis]

Question 11

Plasma constituents

Answer 11

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)

Question 12

Plasma Proteins make up what percentage of total plasma?

Answer 12

7-8% of plasma

Question 13

What is the most important plasma protein?

Answer 13

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

Question 14

Formed Elements (cells)

Answer 14

RBCs

Platelets

WBCs
–lymphocytes, monocytes, neutrophils, eosinophils, basophils

Question 15

RBCs

Answer 15

“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

Question 16

Blood Count

Answer 16

58% plasma volume

Question 17

WBCs

Answer 17

“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

Question 18

Platelets

Answer 18

“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)

Question 19

Hematopoiesis

Answer 19

Development of blood cells and platelets - begin in bone marrow

Question 20

Erythropoiesis

Answer 20

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

Question 21

Thrombopoiesis

Answer 21

Production of platelets

The cytokine, thrombopoietin stimulates growth of megakaryocytes and maturation into platelets

Question 22

Leukopoiesis

Answer 22

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

Question 23

Cytokine

Answer 23

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

Question 24

Blood Clotting

Answer 24

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

Question 25

Platelets and Blood Vessel Walls

Answer 25

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

Question 26

Intact Endothelium

Answer 26

Expresses/secretes platelet inhibitory factors

Barrier function - prevents exposure of platelets to sub-endothelial extracellular matrix molecules

Question 27

Damaged Endothelium

Answer 27

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

Question 28

Formation of Platelet Plug and Clot

Answer 28

Platelets bind to fibrin –> reinforces mass of aggregated platelets which effectively plugs the defect

RBCs become entwined in the plug –> solid clot

Question 29

Coagulation Cascade

Answer 29

Both intrinsic and extrinsic pathways converge on formation of THROMBIN

Thrombin converts fibrinogen to fibrin (aids on cross linkages of platelets in blood clotting)

Question 30

Clot Formation and Dissolution

Answer 30

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