Section4. Cardiovascular physiology

Question 1

The pulmonary circulation normally contains what percentage of the total blood volume?

Answer 1

9%

Question 2

The heart in diastole, normally contains about what percentage of the total blood volume?

Answer 2

7%

Question 3

Which vessels contain the greatest amount of elastin?

Answer 3

aorta and pulmonary artery

Question 4

Capillaries are generally more permeable on the arterial or venous end?

Answer 4

more permeable on the arterial end

Question 5

The resting state red blood cell transit time from the arteriolar to the venular end of an average-sized capillary bed (70 kg mammal) is about?

Answer 5

1 to 2 seconds

(0.07 cm/second)

Question 6

The velocity of blood flow normally reaches its lowest point in which vessels?

Answer 6

capillaries

Question 7

B/c of Bernoulli, what relationship exists between blood velocity and pressure in the capillary bed?

Answer 7

IN a closed tube, such as a blood vessel, total energy must remain constant. Thus kinetic energy of flow plus pressure energy must remain constant. When applied to a narrow portion of a blood vessel- kinetic energy is increased as velocity increases and potential energy must be reduced

Question 8

What is thought to be the primary determinant of resistance to blood flow in the vascular system?

Answer 8

the radius of blood vessels

Question 9

What are factors that enhance lymph flow:

Answer 9

skeletal muscle contraction
rhythmic pumping action of lymphatic vessels
pulsations of arteries
suction pressure created within lympahtic vessels

Question 10

The amount of lymph formed per day in the body is roughly equivalent to the

Answer 10

plasma volume

Question 11

What is normal plasma volume?

Answer 11

4% of bodyweight

Question 12

The colloid osmotic pressure is normally greatest in lymph collected from what organ?

Answer 12

The liver

Question 13

Over one-half of the lymph formed in the body normally comes from which organs?

Answer 13

Liver and GIT

Question 14

The lymphatic system is a major route of absorption of nutrients from the intestinal tract, being particular responsible for:

Answer 14

the absorption of dietary fat
–> chylomycrons are too large to enter the vascular system of the intestine, but are absorbed into lacteals of the lymphatic system

Question 15

What are the causes of edema:

Answer 15

1. increased capillary pressure d/t venular constriction or increased venous pressure (ie: heart failure, venous obstruction, etc)
2. decreased oncotic pressure gradient across capillaries (ie: decreased plasma protein concen d/t nephrosis)
3. increased capillary permeability d/t histamine, kinins or related substances
4. inadequate lymph flow

Question 16

What factors are known to cause increased cerebral blood flow?

Answer 16

-CSF H concen increases (cerebral blood vessels dilate)
-INC in perivascular K concen
-INC adenosine concen in brain tissue (inc d/t ischemia, hypoxemia, hypotension, electrical stim or seizures)

Question 17

What are the two most known resistance vessels in the skin?

Answer 17

arterioles
arteriovenous anastomoses

Question 18

Parasympathetic vasodilater nerve fibers do not supply cutaneous blood vessels, however, stimulates of:

Answer 18

sweat glands, which are innervated by cholinergic sympathetic fibers, results in vasodilation of skin resistance vessels

Question 19

Splenic contraction is facilitated by:

Answer 19

alpha-adrenergic agents

Question 20

Skeletal muscle accounts for what percentage of basal O2 consumption at rest?

Answer 20

20 to 30%

Question 21

Under resting conditions, which organ, normally receives, per unit of weight, a greater blood flow than any other major organ in the body?

Answer 21

Kidney

Question 22

During exercise, pulmonary vascular resistance

Answer 22

falls

Question 23

SA node pacemaker activity is governed largely by:

Answer 23

magnitude of the initial resting membrane potential, the rate of depolarization and the threshold

Question 24

What is the effective refractory period of the cardiac cycle is the:

Answer 24

period during which a stimulus, no matter how strong, fails to produce a propagated electrical response

Question 25

define intercalated disk

Answer 25

entire, continuous stepwise boundary joining the end regions of adjacent cardiac mm cells

Question 26

Dihydropyridine receptor on the T-tubule, functions as:

Answer 26

a voltage sensor in skeletal mm

Question 27

The decreased early resting pacemaker preportential that causes faster heart rates is usually attributable to an altered ratio of intracellular to external (what electrolyte?

Answer 27

K

Question 28

acetylcholine has what effect on the heart?

Answer 28

mild stimulus: slowing of heart rate, decreases strength of atrial contraction and marked reduction of conduction velocity through AV node

Question 29

The first heart sound of the cardiac cycle heard with a stethoscope is

Answer 29

is caused by oscillation of blood in the ventricular chambers and vibration of the chamber walls

Question 30

The second heart sound of the cardiac cycle occurs with

Answer 30

closure of the semilunar valves

Question 31

What conditions increase intensity of the second heart sound?

Answer 31

pulmonary or systemic hypertension

Question 32

The third heart sound of the cardiac cycle is associated with

Answer 32

rapid inflow of blood into the ventricles

Question 33

Left ventricular isometric contraction involves

Answer 33

a period of rising tension in the ventricles, however there are no changes in intraventricular volume

Question 34

Cardiac valve closure occurs when

Answer 34

pressure in the distal chamber exceeds that in the proximal chamber **opening of semilunar valve by rise of pressure in ventricle ** fall of pressure in the distal chamber--opening of mitral and tricuspid valves

Question 35

What is the normal end-ventricular systolic volume (ie. residual volume)?

Answer 35

at rest is about equal t o the ejected during systole

Question 36

Is atrial contraction essential for normal ventricular filling (at rest)?

Answer 36

No, since hte bulk of ventricular filling normally occurs before strial systole

Question 37

What percentage of total blood inflow into the coronary circulation normally enters the right coronary artery of dogs?

Answer 37

15%

Question 38

Describe coronary blood flow

Answer 38

-onset of isometric ventricular contraction, coronary blood flow falls abruptly -opening of aortic calve and systolic inc in aortic pressure, coronary flow rises to a mod peak then fall again -closure of the aortic valve, coronary flow rises to a maximum, to again decline slowly during diastole

Question 39

What percentage of oxygen in coronary blood is normally removed by the heart

Answer 39

70%

Question 40

In the postabsorptive state the principle fuel used by myocardial cells is:

Answer 40

fatty acids

Question 41

What is the effective circulating volume?

Answer 41

reflects the adequacy of tissue perfusion -related directly to the fullness of and pressure within the vascular tree, and under normal circumstances varies directly with ECF volume

Question 42

Of the mechanoreceptors within the body, which one is considered to be low-pressure baroreceptors that primarily sense fullness of the vascular tree rather than the pressure therein?

Answer 42

atrial stretch receptors

Question 43

An increase in heart rate is sometimes produced by large intravenous infusion of saline or blood. This "Bain bridge reflex" is caused by:

Answer 43

the firing of type A high-pressure baroreceptors in atria of the heart

Question 44

Which of the cranial nerves are considered buffer nerves? (which nerves receive input from aortic arch and carotid sinus baroreceptors and send info to hypothalamic and medullary centers via)

Answer 44

X: vagus IX: glossopharyngeal

Question 45

What occurs when sensory input from baroreceptors decreases:

Answer 45

sympathetic outflow to the heart and blood vessels increases

Question 46

Where is the cardiovascular control center located?

Answer 46

medulla of the brain stem

Question 47

The cardiovascular control center is tonicallya ctive system that is inhibited by input from baroreceptors through which cranial nerves?

Answer 47

IX: glossopharyngeal: innervates the carotid sinuses X: vagus: innervates the aortic arch and low pressure volume receptors in the atria and pulmonary circulation

Question 48

When sensory input to from baroreceptors decreases, as it does when arterial pressure decreases, how does the sympathetic/parasympathetic system respond?

Answer 48

sympathetic outflow from hypothalamus to heart and blood vessels increases parasympathetic outflow from the hypothalamus to the heart decreases ANS: helps to oppose a fall in arterial pressure and restore both blood pressure and volume

Question 49

When sensory input to baroreceptors increases, as it does when arterial pressure increases, how does the sympathetic/parasympathetic system respond>

Answer 49

Sympathetic outflow to heart and blood vessels decreases parasympathetic outflow increases

Question 50

What is the ultimate effect of atrial natriuretic peptide?

Answer 50

rapidly increases excretion of NaCl and water by the kidneys

Question 51

What are the effects of ANP on the kidney?

Answer 51

-vasodilates afferent and vasoconstrict efferent arterioles of the kidney (INC GFR) -decreases renin secretion by juxtaglomerular cells of afferent arterioles (indirect actions on angiotensin II and II concentrations)-- dec peripheral resistance and dec aldosterone release from adrenal cortex -dec ability of ADH to act on medullary collecting ducts of the kidney

Question 52

arterial receptors that respond to changes in the PCO2, PO2 and pH of blood are found in specialized tissues near

Answer 52

aortic archa dn carotid bifurcations

Question 53

When arterial chemoreceptors are stimulated in the carotid arteries, what are the response?

Answer 53

they respiratory response is greater, evoking pulmonary hyperventilation and secondarily inc in heart rate

Question 54

In normal adult mammals, what is the average blood volume (ml/kg bwt) is about?

Answer 54

75 ml/kg

Question 55

Following hemorrhage, what control mechanism for restoration of blood volume is considered to be the most importantly quantitatively?

Answer 55

capillary fluid shift

Question 56

plasma compartment (iin % bwt) in comparison to interstitial fluid compartment?

Answer 56

16% bwt: interstitial fluid compartment 4% bwt: plasma compartment

Question 57

How do red blood cells gain energy?

Answer 57

anaerobic glycolytic pathways & heoxse monophosphate shunt that produces NADPH for glutathione reduction (defense mech against oxidative stress)

Question 58

What is the principle component of the red cell, that makes up about 95% of the dry weight of the cell?

Answer 58

hemoglobin

Question 59

Erythropoiesis requiries all of the following minerals/vitamins

Answer 59

copper cobalt iron folic acid and pyridoxine

Question 60

What is the effect of lead on erythropoiesis?

Answer 60

inhibits conversion of delta-aminoleculinate to porphobilinogen toin heme biosysntehsis, therefore resulting ind ecreases erythropoiesis and anemia

Question 61

Why is ceruloplasmin important in erythropoiesis?

Answer 61

-copper containing protein iof plasma -is a ferroxiase and appears ot be necssary for transfer of irone from reticuloendothelial cells to plasma transferrin

Question 62

Methemoglobin reductase of mature erythrocytes uses what molecule from anaerobic glycosis?

Answer 62

NADH **does not use NADPH

Question 63

What is methemoglobin

Answer 63

an inactive form of hemoglobin in which the iron is oxidzed from teh ferrous to feric state by superoxides that are normally rpesent in RBCs

Question 64

What is the importance of methemoglobin reductase?

Answer 64

important in keeping iron in its active state (since only heme iron in the ferrous form can carry oxygen reversibly)

Question 65

The Rapoport shunt is the source of

Answer 65

2,3-diphosphoglycerate in erythrocytes

Question 66

What is the importance of the Rapoport shunt in RBCs?

Answer 66

It allows for glycolysis to prcoeed when the need for ATP is minimal

Question 67

What are the effects of leukotrienes released from white blood cells?

Answer 67

-contraction of smooth mm -cause vascular permeability to increases - important regulators in many dzes involving inflammatory or immediate hypersensitivity reactions

Question 68

Thromboxane A2 is synthesizes in and causes

Answer 68

platelets causes vasoconstriction and plt aggregation

Question 69

Prostacycline is produces where and causes

Answer 69

releases from endothelial cells of blood vessel wall promotes vasodilation and inhibits plt aggregation

Question 70

Which is the strongest plt aggregator?

Answer 70

thromboxane A2

Question 71

platelets are known to release which compound to ahsten blood coagulation?

Answer 71

thrombopalstin

Question 72

Adenosine release from platelets helps to

Answer 72

facilitate plt aggregation

Question 73

Aspiring irreversibility inhibits

Answer 73

platelet cyclooxygenase and thus formation of thromboxane A2

Question 74

What is the key step in blood coagulation?

Answer 74

conversion of fibrinogen to fibrin by thrombin

Question 75

blood clotting via the extrinsic pathway is initiated by

Answer 75

tissue damage and relase of tissue thromboplastin

Question 76

Blood clotting via the intrinsic pathway is initiated by

Answer 76

exposure of blood to damaged endothelium or a negatively charged surface

Question 77

What is the most important cofactor for blood coagulation (electrolyte)?

Answer 77

Calcium

Question 78

What is an endogenous (active) proteolytic enzyme known to liquefy blood clots?

Answer 78

plasmin

Question 79

Which anticoagulant is know to inhibit synthesis of vitamin K dependent factors involved in blood coagulation?

Answer 79

dicumarol

Question 80

How are the anticoagulant effects of citrate and oxalate peformed?

Answer 80

through removal of calcium fro solution