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MCAT-BIOLOGY > Circulatory & Lymphatic Systems > Flashcards

Circulatory & Lymphatic Systems Flashcards

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1
Q

what is the purpose of the circulatory system?

A

distribute nutrients, transport oxygen and carbon dioxide, transport/remove metabolic wastes from tissues to excretory/kidney, transport hormones and provide feedback, maintain homeostasis of body temperature, hemostasis (blood clotting)

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2
Q

perfusion

A

the flow of blood through a tissue

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3
Q

ischemia

A

inadequate blood flow (i.e. no waste removal either)

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4
Q

hypoxia

A

reduced oxygen (i.e. blood can still remove waste)

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5
Q

heart

A

muscular pump that forces blood through a branching series of vessels to the lungs and the rest of the body

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6
Q

arteries

A

vessels that carry blood away from the heart at high pressure

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7
Q

veins

A

vessels that carry blood back toward the heart at low pressure

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8
Q

arterioles

A

increasingly smaller arteries, contain walls of smooth muscle that can constrict/dilate to control resistance and amount of blood flow into the capillaries of tissues

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9
Q

capillaries

A

very small vessels that are wide enough for only a single blood cell to pass, one endothelial cell layer, where exchange of material with tissues occur

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10
Q

venules

A

small veins where blood collects after exiting capillaries

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11
Q

endothelial cells

A

a thin inner lining found in all blood vessels, capillaries are formed from only a single layer of endothelial cells, have important roles in vascular function

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12
Q

what are some functions of endothelial cells?

A

vasodilation and vasoconstriction, inflammation (release of inflammatory chemicals from injured tissues stimulate endothelial cells to increase their expression of adhesion molecules), angiogenesis (formation of new blood vessels), thrombosis (blood clotting, undamaged endothelial cells secrete substances that inhibit the coagulation cascade)

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13
Q

pulmonary circulation

A

the flow of blood from the heart to the lungs and back to the heart

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14
Q

systemic circulation

A

the flow of blood from the heart to the rest of the body and back again

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15
Q

portal systems

A

circulatory systems that consist of two sets of capillaries, allow for direct transport between tissues without having to pass through the whole body

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16
Q

what are the two portal systems in the human body?

A

hepatic portal system (capillaries in intestines and liver for nutrient delivery) and hypothalamic-hypophysial portal system (capillaries in hypothalamus and pituitary for hormone delivery)

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17
Q

atria

A

chambers that collect blood

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18
Q

right atrium receives:

A

deoxygenated blood from the systemic circulation via the inferior and superior vena cava

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19
Q

ventricle

A

chambers that pump blood out of the heart at high pressure

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20
Q

coronary arteries

A

the very first branches from the aorta which supply blood to the wall of the heart

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21
Q

coronary veins

A

where deoxygenated blood from the heart collect, merges to the coronary sinus which drains directly into the right atrium

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22
Q

what are the two types of valves in the heart?

A

atrioventricular valves (tricuspid valve-right and bicuspid/mitral-left) and semilunar valves (pulmonary and aortic semilunar valves)

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23
Q

valves in veins prevent:

A

backflow and help to push the low pressure blood to the heart, contractions of skeletal muscle also helps to pressurize and push venous blood

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24
Q

diastole

A

ventricles relax and blood is able to flow into the atria, atria contract to push blood into ventricles, AV valves open, at the end ventricles contract and AV valves close (lub, S1)

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25
Q

systole

A

ventricles contract while ventricles relax and blood enters, semilunar valves open, at the end semilunar valves close because artery pressure is larger than ventricle pressure, (dub, S2)

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26
Q

heart rate/pulse

A

the number of times the diastole/systole cardiac cycle is repeated per minute

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27
Q

stroke volume (SV)

A

the amount of blood pumped with each systole

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28
Q

cardiac output (CO)

A

the total amount of blood pumped per minute, the product of stroke volume times heart rate

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29
Q

Frank-Starling mechanism

A

increase cardiac output by increasing the volume of blood entering the heart which stretches heart muscle and causes it to contract more forcefully

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30
Q

venous return

A

the return of blood to the heart by the venous cava

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31
Q

what are the two principal ways of increasing venous return?

A

increase the total volume of blood in the circulation (peeing less) or contraction of large veins can propel blood toward the heart (valves prevent backflow)

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32
Q

what is the difference between neurons and cardiac muscle cells?

A

cardiac muscle is a functional syncytium

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33
Q

syncytium

A

a tissue in which the cytoplasm of different cells can communicate via gap junctions which are found in intercalated disks (connections between cardiac and muscle cells) in the cardiac muscle, this is an example of an electrical synapse

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34
Q

cardiac conduction system

A

the action potential in the heart is transmitted from the atrial syncytium to the ventricular syncytium (which are two separate syncytia), transmission is delayed at the A-V node (located at the tricuspid valve, aka atrioventricular node)

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35
Q

fast sodium channels

A

involved in cardiac muscle action potential

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36
Q

slow calcium channels

A

involved in cardiac muscle action potential, stay open longer than do sodium channels and causes a plateau phase (phase 2)

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37
Q

T-tubules

A

involutions of the membrane of cardiac muscle cells to maximize entry of calcium from extracellular environment (sarcoplasmic reticulum also releases intercellular calcium) to cause contraction of actin-myosin fibres

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38
Q

contractility

A

strength of contraction of the heart

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39
Q

is the heart stimulated to contract by neuronal/hormonal influences?

A

NO, the sinoatrial node (SA node) at the outside of the top of the right atrium is the pacemaker of the heart, but neuronal/hormonal influences can change the rate and strength/contractility

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40
Q

outline the action potential of the SA node

A

phase 4 (slow inward sodium through leak channels contributes to unstable resting potential), once threshold reached, phase 0: depolarization (inward calcium through voltage gated channels, phase 3: repolarization (outward potassium through voltage gated channels)

41
Q

how does the SA node transmit the action potential to the rest of the conduction cells in the heart?

A

by intercalated disks/gap junctions/electrical synapses

42
Q

outline the action potential in a cardiac muscle cell

A

phase 0: depolarization (fast sodium voltage gated channels open, sodium influx)
phase 1: initial repolarization (sodium channels inactivate, potassium voltage gated channels open, potassium efflux)
phase 2: plateau (calcium voltage gated channels open and calcium influx results in equilibrium with potassium efflux from open potassium voltage gated channels)
phase 3: repolarization (calcium voltage gated channels close, potassium voltage gated channels still open, potassium efflux)
phase 4: resting potential (potassium channels close and resting membrane potential maintained by sodium/potassium ATPase and slow potassium leak channels)

43
Q

internodal tract

A

special conduction pathway that allows for rapid transmission of action potential between the SA node and the AV node, faster transmission than rate of impulse travelling through the atria

44
Q

at the AV node, the impulse is delayed slightly before passing to ventricles by what conduction pathway?

A

the AV bundle (bundles of His) which divides into right and left bundles branches, then into Purkinje fibers which allow the impulse the spread rapidly and evenly over both ventricles at the apex

45
Q

what is the role of the ANS on the heart?

A

it regulates the rate of contraction

  • parasympathetic nervous system contributes to vagus tone: continual inhibition of SA node depolarization (i.e. inhibits rapid automaticity)
  • sympathetic nervous system directly innervates the heart and releases norepinephrine and epinephrine from medulla can also bind to receptors on cardiac muscle cell to stimulate heart rate and force of contraction
46
Q

what are autonomic nervous system receptors regulating the heart?

A

in the aortic arch and carotid arteries (contain baroreceptors to monitor pressure)

47
Q

hemodynamics

A

the study of blood flow

48
Q

Ohm’s Law

A 
summarizes relationship between pressure, output and resistance
pressure gradient (change in pressure,mmHg)=Q (blood flow/cardiac output, L/min) * R (resistance)
49
Q

what is the principal determinant of resistance?

A

the degree of constriction of arteriolar smooth muscle/precapillary sphincters/peripheral resistance

50
Q

which portion of the nervous system controls the peripheral resistance?

A

the sympathetic nervous system which provides a basal level of pressure (adrenergic tone) by a constant level of norepinephrine released by postganglionic axons innervating precapillary sphincters, can also specifically divert blood away from one tissue to preferentially perfuse another tissue

51
Q

systemic arterial pressure

A

force per unit area exerted by blood upon the walls of arteries, systolic pressure/diastolic pressure

52
Q

systolic pressure

A

heard when systolic arterial pressure is higher than cuff pressure, the highest pressure that can occur in the circulatory system, attained as ventricles contract, between S1 and S2

53
Q

diastolic pressure

A

when pulse can’t be heard, the lowest ARTERIAL pressure occurring at any time during the cardiac cycle, between S2 and next S1 as ventricles are filling with blood

54
Q

what is the pressure at the vena cava?

A

approximately 0 mmHg

55
Q

pulse pressure

A

the difference between systolic and diastolic pressures

56
Q

what is used to measure blood pressure?

A

sphygmomanometer

57
Q

local autoregulation

A

mechanism whereby certain metabolic wastes have a direct effect on arteriolar smooth muscle and causes to relax, this allows extra tissue perfusion and automatic vasodilation, the principal determinant of coronary blood flow

58
Q

what are the components of blood (from least dense to most dense)

A

plasma (54%) - water, electrolytes, nutrients, hormones, wastes, plasma proteins, lipoproteins
leukocytes (1%) - white blood cells and platelets (formed elements)
hematocrit (45%) - formed elements

59
Q

plasma

A

the liquid portion of blood

60
Q

formed elements

A

the cellular elements of blood

61
Q

what is the principal blood buffer?

A

bicarbonate

62
Q

what are the plasma proteins?

A

albumin (essential for maintenance of oncotic pressure), immunoglobulins (antibodies), fibrinogen (blood clotting, hemostasis)

63
Q

lipoproteins

A

large particles consisting of fat, cholesterol, and carrier proteins, functions to transport lipids in the bloodstream

64
Q

urea

A

principal metabolic waste product, a breakdown product of amino acids, a carrier of excess nitrogen

65
Q

what is the breakdown product of heme?

A

bilirubin

66
Q

where do all formed elements of the blood develop from?

A

bone marrow stem cells

67
Q

serum

A

plasma without fibrinogen

68
Q

erythropoeitin

A

hormone made in the kidneys that stimulates RBC production in the bone marrow

69
Q

what happens to aged RBC’s?

A

degraded by phagocytes in the spleen and liver

70
Q

outline characteristics of RBC’s

A

a cell with no nucleus or organelles, uses ATP by performing glycolysis, 120 day lifetime, concave shape, contains hemoglobin

71
Q

hemolytic disease of the newborn/erythroblastosis fatalis

A

Rh+ baby’s blood mixes with Rh- mother’s blood, if next baby is Rh+, mother’s blood will contain anti-Rh antibodies that can cross the placental barrier and clump or destroy baby’s RBC’s. treatment: injection of mother at the time of birth with anti-RH antibodies to prevent sensitization of mother to Rh

72
Q

what are the six types of leukocytes?

A

monocytes: macrophage, lymphocytes: B cell, T cell, granulocytes: neutrophil, eosinophil, basophil

73
Q

macrophage

A

phagocytose debris and microorganisms, amoeboid motility, chemotaxis

74
Q

B cell

A

mature into plasma cell and produce antibodies

75
Q

T cell

A

kill virus-infected cells, tumour cells, and reject tissue grafts, also controls immune response

76
Q

neutrophil

A

phagocytose bacteria resulting in pus, amoeboid motility, chemotaxis

77
Q

eosinophil

A

destroy parasites, allergic reactions

78
Q

basophil

A

store and release histamine, allergic reactions

79
Q

how are platelets formed?

A

fragmentation of megakaryocytes: large bone marrow cells

80
Q

what is the function of platelets?

A

to form a platelet plug by aggregating at the site of damage to a blood vessel wall

81
Q

fibrinogen is converted to:

A

fibrin (threadlike protein that forms a mesh to hold the platelet plug together) by thrombin which requires calcium for activation

82
Q

how many molecules of oxygen can hemoglobin carry?

A

4, binds cooperatively

83
Q

Bohr effect

A

factors including: decreased pH, increased partial pressure/concentration of CO2, increased temperature, stabilizes tense hemoglobin and reduces oxygen affinity (ie. oxygen is released and allowed to enter cell)

84
Q

percent saturation

A

used to measure oxygen affinity, # of O2 molecules bound/# of O2 binding sites * 100%

85
Q

how is carbon dioxide transported in the blood?

A

73% is converted to carbonic acid by carbonic anhydrase which exists in equilibrium with bicarbonate and protons, 20% sticks to hemoglobin (can be further stabilized by the Bohr effect), 7% dissolves (slightly water-soluble)

86
Q

intercellular clefts

A

spaces between the endothelial cells that make up the capillary wall that facilitate exchange between blood and tissues, allows passage of nutrients, wastes, and white blood cells

87
Q

how to gases enter capillaries

A

by simple diffusion

88
Q

chylomicrons

A

a type of lipoprotein, i.e. lipid transport in the blood stream

89
Q

how do fats in intestine enter bloodstream?

A

packaged into chylomicrons, enter lacteals (lymphatic vessels in intestinal wall), larger lymphatics, drains into vein in neck, enter liver and converted into another type of lipoprotein, carried to adipocytes for storage (i.e. completely bypasses hepatic portal vein)

90
Q

lipemia

A

milky appearance of blood after a fatty meal

91
Q

which two types of white blood cells can squeeze through intercellular clefts in the capillaries?

A

macrophages and neutrophils

92
Q

what are two reasons that water tends to flow out of capillaries?

A

1) hydrostatic fluid pressure, high pressure causes water to squeeze out of capillaries
2) high osmolarity of tissues

93
Q

oncotic pressure

A

albumin in plasma is too large and remains in plasma, provides osmotic pressure and draws most water back into capillaries

94
Q

edema

A

swelling that is the result of water in the tissues

95
Q

how do fluids, proteins, and white blood cells in the tissues return to the bloodstream?

A

by the lymphatic system

96
Q

lymphatic system

A

one-way flow system which begins with tiny lymphatic capillaries that merge into larger lymphatic vessels (with valves) and further into large lymphatic ducts (with smooth muscle) and the thoracic duct (largest lymphatic duct) and ultimately empties into a large vein in the neck

97
Q

what is the fluid in lymphatic vessels called?

A

lymph

98
Q

lymph nodes

A

filters lymph, part of immune system and can initiate an immune response against foreign agents

MCAT-BIOLOGY (17 decks)

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