Cardiovascular Physiology Flashcards
The cardiovascular system solves the problem of __________ in
_____________.
a) blood flow — muscle cells
b) transport — unicellular organisms
c) diffusion — multicellular organisms
d) oxygen transport — acid-base regulation
diffusion — multicellular organisms
__________is the volume of blood occupied by __________ .
a) Hematocrit — erythrocytes
b) Albumin — protein
c) Fuzzy layer — lymphocytes
d) Cardiac output — plasma
Hematocrit — erythrocytes
Which of the following statements is correct?
a) The AV valves open when the atria contract.
b) The aortic and AV valves open simultaneously.
c) The AV valves open when the ventricles contract.
d) The AV valves close when the ventricles contract.
The AV valves close when the ventricles contract
In contrast to arterial vessels, veins have:
a) thinner walls.
b) more smooth muscle.
c) higher resistance.
d) thicker endothelium.
Thinner walls
What are the purposes of the cardiovascular system?
Regulation of body temperature
Fluid homeostasis
Control of O2/nutrient supply
What is the evolutionary need for a circulatory system?
Small organisms with no circulatory system are able to use diffusion for their metabolic needs. Due to the larger size and complexity of multicellular organisms, the cardiovascular system is an evolutionary consequence that allows our bodies to exchange compounds through these very large distances.
What are the two components of blood?
Plasma and Cells
What are the functions of blood?
Delivery of metabolic substrates
Removal of metabolic waste
Defense against invading microorganisms/injury
Maintenance of acid/base balance
Serum
Plasma without clotting factors
Two groups of plasma proteins
Albumin and Globulins
Where are most plasma proteins produced from?
Liver
Where are antibodies (immunoglobulins, a type of plasma protein) produced from?
Plasma cells during an immune response
Cellular elements of the blood
Erythrocytes (RBCs)
Leukocytes (WBCs)
Platelets
Where do blood cells originate?
STEM cells in the bone marrow
Two blood cell lineages
Lymphoid
Myeloid
Lymphoid cells
B and T lymphocytes, natural killer cells
Myeloid cells
Erythrocytes
Leukocytes (monocytes, neutrophils, eosinophils, basophils)
Platelets
Purpose of Erythrocytes
Carrying O2 from lungs to tissues
Carrying CO2 from tissues to lungs
Buffering of acids and bases
Purpose of Leukocytes
Involved in inflammation and immune responses
Purpose of Platelets
Involved in hemostasis/blood clotting
What is hematocrit?
The fraction of the blood occupied by erythrocytes (a measure of erythrocyte concentration)
Thrombocytopenia
Too few platelets
Increases the risk of abnormal bleeding
Thrombocytosis
Too many platelets
Increases the risk of abnormal clotting
Methods that achieve hemostasis:
Vasoconstriction
Increased tissue pressure
Platelet plug formation in capillary bleeding
Coagulation/Clot formation
Process of platelets plugging small breaches
Adhesion: surface platelet receptors bind to ligands present around tissue damage
Activation: triggered by the binding, platelets secrete contents of cytoplasmic granules, which recruit and activate more platelets
Aggregation: platelets will aggregate and join, forming a mass that covers the endothelial defect
Blood Clot
Semisolid mass of serum, platelets, erythrocytes, and leukocytes in a mesh of fibrin
Thrombus
Blood clot inside a vessel
Procoagulant Forces
Platelet adhesion
Platelet aggregation
Fibrin clot formation
Anticoagulant Forces
Natural inhibitors of coagulation and fibrinolysis
Extrinsic Clotting Pathway
Tissue factor (blood contacts a negatively charged surface)
Intrinsic Clotting Pathway
Contact activation (blood contacts damaged cell membranes)
Explain the process of the clotting pathway
Trigger event (either extrinsic or intrinsic) initiates a chain reaction
Plasma proteins are activated by enzymes
Enzyme converts prothrombin into thrombin, which will initiate a positive feedback loop by amplifying the clotting cascade
Thrombin will also convert fibrinogen into loose and stabilized fibrin, which will form a mesh that traps platelets and erythrocytes
Antithrombotic mechanisms
Prevent clotting under normal circumstances – makes sure that there is only clotting where there is injury
What is the purpose of endothelial cells in clotting?
Produce prostacyclin, nitric oxide, and other factors that will inhibit platelet binding, secretion, and aggregation.
Produce antithrombin which will inhibit thrombin and other clotting factors.
Activate fibrinolytic mechanisms by producing tissue- and urokinase-type plasminogen activator, which will convert plasminogen to plasmin
Plasmin
A protease that breaks down fibrin and allows a clot to be dissolved
Right Heart
Low pressure, Pulmonary circulation
Left Heart
High pressure, Systemic circulation
Why does the left ventricle have a much higher pressure than the right?
The left ventricular wall is much thicker than the right (12-15mm)
Pulmonary Circulation
Low-pressure blood flow to the lungs – thin right ventricular walls
Systemic Circulation
High-pressure blood flow to the body (except the lungs) – thick left ventricular walls
Right Atria BF
Receives blood from the systemic circulation –> Pumps blood into the right ventricle
Left Atria BF
Receives blood from the pulmonary circulation –> Pumps blood to the left ventricle
Right Ventricle BF
Receives blood from the right atrium –> Pumps blood to the pulmonary circulation
Left Ventricle BF
Receives blood from the left atrium –> Pumps blood to the systemic circulation
Why is cardiac flow unidirectional?
Valves open in one direction only
What are the 4 heart valves?
AV valves (Tricuspid/Right and Mitral/Left)
Aortic valve
Pulmonary Valve
Tricuspid Valve
Right (3 cusps)
Mitral Valve
Left (2 cusps)
What is the purpose of the cusps/leaflets in the AV valves?
Upper ends are attached to rings in fibrous cardia skeleton; Lower ends attached to papillary muscles which hold the cusps in place during ventricular contraction and prevent prolapse into the atria; Cusps will create a tight seal that will help blood flow go into the correct direction
How does blood leave the Right Ventricle?
Through the pulmonary valve
How does blood leave the Left Ventricle?
Through the aortic valve
What happens during Ventricular Relaxation?
AV valves open and blood flows from higher pressure in the atria to lower pressure in the ventricles
What happens during Ventricular Contraction?
Ventricular pressure increases, AV valves close, Semilunar valves open, Blood flows into systemic (left) and pulmonary (right) circulations
What happens after Ventricular Contraction?
Pressure drops, Pulmonary and Aortic valves close (preventing backflow)
3 Layers of the Heart Wall
Epicardium
Myocardium
Endocardium
Pericardium
Double-walled membranous sac that encloses the heart and prevents displacement of the heart as well as infection and inflammation. It also contains pain receptors and mechanoreceptors
Epicardium
Outer layer of the heart; A smooth surface that allows cardiac movement within the pericardium
Myocardium
Thickest layer; Composed of cardiac muscle anchored to the heart’s fibrous skeleton
Endocardium
Lines the inside of the atria and ventricles; Composed of connective tissue and a layer of squamous cells; Continuous with the vascular endothelium that creates a continuous circulatory system
Cardiomyocytes
Excitable cells (carry out action potentials) in the cardiac muscle (included in the myocardium)
Blood Vessels
Arteries
Capillaries
Veins
Arteries
Large: elastic, little resistance, sustain blood flow during diastole
Small (arterioles): muscular, high resistance, regulate blood flow to specific areas
Capillaries
One cell layer thick (endothelium)
Exchange with tissues (diffusion)
Veins
Thin, low-resistance vessels
What does blood distribution depend on?
The output of the left ventricle and by the contractile state of the arterioles of different vascular regions
Principle of Blood Volume
Blood is volume is constant, if volume increases in one area it must decrease in another area
Arterial pressure is _______
Pulsative
(due to the pumping action of the heart)
Venules
Collect the blood after the capillaries, then join larger veins that form a very low resistance pathway back to the heart
Lymph
Extra fluid in the interstitial space due to the capillary-tissue exchange. It will return to the cardiovascular system via the lymphatic system
