05 - Hemodynamics and Blood

Question 1

What is blood pressure
how is it generated

Answer 1

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

Question 2

What regulates blood pressure

Answer 2

cardiac output (SV x HR)
blood volume
vascular resistance : resistance to blood flow

Question 3

Where is BP highest
Where is BP the lowest

Answer 3

aorta, arteries, arterioles
veins, venae cavae

Question 4

What is systolic blood pressure

Answer 4

maximum blood pressure measured in the aorta or pulmonary trunk

Question 5

What is diastolic blood pressure

Answer 5

minimum bp measured in the aorta or pulmonary trunk

Question 6

What is pulse pressure

Answer 6

the difference between systolic and diastolic pressure

Question 7

What is the mean arterial blood pressure

Answer 7

the average bp observed in arteries over one cardiac cycle

DBP +1/3 PP

CO x total peripheral resistance

Question 8

What is vascular resistance

Answer 8

the opposition to blood flow due to friction between the blood nad the walls of blood vessels

total pressure resistance
systemic vascular resistance

Question 9

What is SVR dependent on

Answer 9

size of blood vessel lumen (vasocontriction/dilation)

blood viscocity (dehydration, anemia, hemorrhage, polycythemia)

total blood vessel length (increased adiposity)

Question 10

What is blood flow

Answer 10

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)

Question 11

What are the short term regulators of blood pressure

Answer 11

neural

hormonal

Question 12

Describe short term neural regulation

Answer 12

• 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

1. carotid sinus/aortic sinus
2. glossopharyngeal nerves
3. cardiovascular centre
4. medulla oblongata /vagus nerves
5. sympathetic ganglion in spinal cord / SA node
6. myocardium / AV node

Question 13

Describe short term
hormonal regulation

Answer 13

1. epinephrine (adrenaline) - stimulates B1 and A1 receptors
2. norepinephrine (noadrenaline) - preferentially stimulates a1 receptors

b1: increased HR and contractility
a1: increased SVR through vasoconstriction

Question 14

What are the hormones that contribute to long term blood pressure

Answer 14

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)

Question 15

What is shock

Answer 15

failure of the cardiovascular system to deliver adequate oxygen and nutrient to tissues to meet their needs

Question 16

What are the functions of blood

Answer 16

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)

Question 17

What are the components of blood

Answer 17

blood plasma (55%) - liquid extracellular matrix (water, plasma proteins, nutrients, gases, regulatory substances, wastes)

formed elements (buffy coat – wbc and platelets & rbc – hematocrit)

Question 18

What does a complete blood cell count do

Answer 18

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

Question 19

how are blood samples obtained

Answer 19

arterial blood gas (ABG) analysis –> arterial blood
blood chemistry (hormones, electrolytes, toxins) –> venous blood

Question 20

Describe the structure of erythrocytes

Answer 20

• 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

Question 21

Describe hemoglobin

Answer 21

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

Question 22

What is hematopiesis

Answer 22

process by which all formed elements of the blood develop

Question 23

What is erythropoiesis

Answer 23

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

Question 24

Describe the neg feedback loop when O2 levels change

Answer 24

hypoxemia (o2 levels decrease) –> erythropoietin release –> stimulates red bone marrow –> increased RBC count –> increased O2 carrying capacity

Question 25

What happesn when RBC are damaged or worn

Answer 25

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