05 - Hemodynamics and Blood Flashcards
What is blood pressure
how is it generated
force exerted by the blood on the wall of a blood vessels
measured in mmHg (CO x vascular resistance)
pressure generated by the contraction of ventricles
What regulates blood pressure
cardiac output (SV x HR)
blood volume
vascular resistance : resistance to blood flow
Where is BP highest
Where is BP the lowest
aorta, arteries, arterioles
veins, venae cavae
What is systolic blood pressure
maximum blood pressure measured in the aorta or pulmonary trunk
What is diastolic blood pressure
minimum bp measured in the aorta or pulmonary trunk
What is pulse pressure
the difference between systolic and diastolic pressure
What is the mean arterial blood pressure
the average bp observed in arteries over one cardiac cycle
DBP +1/3 PP
CO x total peripheral resistance
What is vascular resistance
the opposition to blood flow due to friction between the blood nad the walls of blood vessels
total pressure resistance
systemic vascular resistance
What is SVR dependent on
size of blood vessel lumen (vasocontriction/dilation)
blood viscocity (dehydration, anemia, hemorrhage, polycythemia)
total blood vessel length (increased adiposity)
What is blood flow
volume of blood that flows through any tissue in a given time period
- speed is inversely related to the cross sectional area (velocity slow where is many tubes – capillaries and venules)
What are the short term regulators of blood pressure
neural
hormonal
Describe short term neural regulation
- baroreceptor reflexes: sensory receptors that monitor bp and provide input to the cardiovascular centre of the brainstem to regulate bp
- chemoreceptor reflexes: sensory receptors that monitor blood chemistry (O2, CO2, H+) and provide input the cardiovascular centre to regulate bp
- carotid sinus/aortic sinus
- glossopharyngeal nerves
- cardiovascular centre
- medulla oblongata /vagus nerves
- sympathetic ganglion in spinal cord / SA node
- myocardium / AV node
Describe short term
hormonal regulation
- epinephrine (adrenaline) - stimulates B1 and A1 receptors
- norepinephrine (noadrenaline) - preferentially stimulates a1 receptors
b1: increased HR and contractility
a1: increased SVR through vasoconstriction
What are the hormones that contribute to long term blood pressure
ADH/vasopressin
- released from the post pitt in response to dehydration/decreased bv
- increases bv by promoting renal water absorption
- increases SVR by stimulating vasoconstriction
Atrial natriuretic peptide (ANP)/B-type natriuretic peptide (bnp)
- released by cells of the atria (ANP) or ventricles (BNP) when overly stretched
- lowers bv by promoting renal water and sodium loss by promoting vasodilation
renin-angiotensin-aldosteroene (RAA) system
- neg feedback loop invovling the prodcution of angiotensin II (promotes release of aldosterone & vasoccontriction of peripheral arterioles –> increases SVR) and aldosterone (promotes renal sodium and water retenation –> Increases bv)
What is shock
failure of the cardiovascular system to deliver adequate oxygen and nutrient to tissues to meet their needs
What are the functions of blood
Transportation: O2, CO2, nutrients, hormones, heat and waste products
Regulation: pH through buffers (bicarbonate), body temp, water content of cells
Protection: blood loos (clotting), diseases (phagocytic WBC, antibodies)
What are the components of blood
blood plasma (55%) - liquid extracellular matrix (water, plasma proteins, nutrients, gases, regulatory substances, wastes)
formed elements (buffy coat – wbc and platelets & rbc – hematocrit)
What does a complete blood cell count do
provides number of RBV and WBC and platelets
- measure of hematocrit (% of RBC in blood), hemoglobin [] (amount of o2 going to tissues) and morphology
- differential: report the % of specific WBC types found in buffy coat
how are blood samples obtained
arterial blood gas (ABG) analysis –> arterial blood
blood chemistry (hormones, electrolytes, toxins) –> venous blood
Describe the structure of erythrocytes
- biconcave disc (greatest SA to volume ratio)
- strong, flexible membrane
- lack nucleus (no DNA) and contain no organelles, generate ATP ANAEROBICALLY
- specialized for O2 transport –> contains hemoglobin and no mitochondria
Describe hemoglobin
consist of protein called globin
composed of four polypeptide chains (2 alpha and 2 beta chains)
nonprotein pigment (heme) bound to each of four chains
iron ion at centre of each heme ring
binds revseribly with O2
1 hemoglobin – 4 O2 molecules
responsible for transporting 23% of CO2 found in circulation
What is hematopiesis
process by which all formed elements of the blood develop
What is erythropoiesis
RBC development
- begins in the bone marrow under the influece of erythropoietin
- pluriopotent stem cells develop into reticulocytes that lose their nucleus and exit the bone marrow
pluripotent stem cell –> reticulocyte –> erythrocyte
Describe the neg feedback loop when O2 levels change
hypoxemia (o2 levels decrease) –> erythropoietin release –> stimulates red bone marrow –> increased RBC count –> increased O2 carrying capacity
What happesn when RBC are damaged or worn
RBC are removed from circulation by liver and spleen
- phagocytosed by macrophages
- globin and iron from hemoglobin recycled
- heme for hemoglobin excreted from the body in the bile as bilirubin –> liver damage can lead to jaundice
