Cardiac Flashcards

Question

What are the different aspects of an ECG (ex. Waves, segments, intervals)?

Answer 1

Waves appear as deflections above or below the baseline Segments are the sections of baseline between two waves Intervals are the combination of waves and segments

Answer 2

The P wave is the first little bump on an ECG, it happens when the atria depolarize. - Connected to the SA node

Answer 3

It is the segment immediately following the P wave, it happens when there is conduction through AV node and AV bundle. - During this the atria contract - Conduction spreads in all directions

Answer 4

Q wave: small depolarization of interventricular septum R wave: main mass of ventricles contracting S wave: Final bit of ventricular depolarizing. QRS complex: overall represents ventricular depolarization - Biggest bump on ECG

Answer 5

It is the segment immediately following the QRS complex. It happens when all cells plateau. - During this segment the ventricular contract.

Answer 6

It is the wave immediately following the ST segment. It represents ventricular repolarization.

Answer 7

P wave to P wave

Answer 8

- Arrhythmias (electrical problems during the generation or conduction of AP’s through the heart) can appear as elongated segments or intervals, altered, missing or additional waves.

Answer 9

- Happens when the purkinje fibres randomly kick in as pacemaker, can be do to insufficient oxygen to myocardium, excessive Ca2+, hypokalemia, medications, exercise, high levels of adrenaline) -perceived as skipped beat or palpitation on ECG

Answer 10

An example of an arrhythmia: - inherited channelopathy (K+, Na+) -delayed repolarization of the ventricles -palpitations, fainting, and sudden death due to ventricular fibrillation -can be drug induced

Answer 11

Diastole: the time during which cardiac muscle relaxes Systole: the time during which cardiac muscle contracts -because the atria and ventricles do not contract and relax at the same time the events are discussed separately. BOTH refer generally to ventricles but can refer to other things.

Answer 12

1. The heart at rest: (atrial and ventricular diastole, late diastole) 2. Completion of ventricular filling (atrial systole) 3. Early ventricular contraction (isovolumetric ventricular contraction) 4. The heart pumps (ventricular ejection) 5. Ventricular relaxation (isovolumetric ventricular relaxation, early diastole)

Answer 13

1. The heart at rest: atrial and ventricular diastole (late diastole) • Cycle starts with atria relaxed and filling with blood from veins • the ventricles begin to relax, when the ventricles are sufficiently relaxed and pressure in atria exceeds ventricles, AV valve opens and ventricles passively fill with blood from atria. - Starts at End systolic volume

Answer 14

2. Completion of ventricular filling (atrial systole) • Most blood enters ventricles passively but under normal resting conditions the last ~ “20%” enters when the atria contract. - Atrial contraction forces a small amount of additional blood into the ventricles. - At the end the ventricles are at end diastolic volume

Answer 15

3. Early ventricular contraction (isovolumetric ventricular contraction) • The ventricles begin to contract, this builds up pressure in the ventricles and causes the AV valves to snap shut (first heart sound s1 “lub”) • Both valves are now closed and then the ventricle continues to contract building up pressure.

Answer 16

4. The heart pumps (ventricular ejection) • As the ventricles contract pressure in the ventricle exceeds pressure in the outflow arteries (aorta or pulmonary arteries) causing the semi lunar valves to open and blood to flow out. - At the end it is at end systolic volume

Answer 17

5. Ventricular relaxation (isovolumetric ventricular relaxation) • The ventricles then begin to relax, pressure in the outflow arteries begins to exceed the ventricles causing blood to attempt to flow backward into the ventricles causing the semi lunar valves to snap shut (second heart sound s2 “dub”)

Answer 18

End diastolic volume (EDV)-the maximal volume in the ventricle, after ventricular filling, 70kg man at rest ~135ml End-systolic volume (ESV)- the minimal amount of blood in the ventricles, blood left after ventricular contraction, ~65ml (decreases during exercise) Stroke volume (SV) -amount of blood ejected during a single ventricular contraction, ~70ml (L/beat or ml/beat) SV = EDV-ESV

Answer 19

Ejection fraction (EF)=(the percentage of EDV that is ejected from the heart (SV) EF=SV/EDV =70ml/135ml=52%

Answer 20

Flow of blood delivered from one ventricle in a given time period (usually 1 minute) is the cardiac output (CO) - CO’s of the pulmonary and systemic circuit are usually identical. -if offset, blood tends to pool in the circuit feeding the weaker side of the heart. Total blood flow (cardiac output) = heart rate x stroke volume CO=F=HR*SV

Answer 21

- CO can be modified by adjusting Heart rate.*(check notes?)* - CO can be adjusted by modulating stroke volume.

Answer 22

1. The contractility of the heart -the intrinsic ability of a cardiac muscle fibres to contract at any given fibre length and is a function of Ca2+ entering and interacting with the contractile filaments. 2. The length of the muscle fibres at the beginning of contraction -this is determined by the volume of blood in the ventricle at the beginning of contraction (end-diastolic volume)

Answer 23

- Any chemical that affects contractility is called an inotropic agent and its influence is referred to as an inotropic effect. -chemicals increasing contractility have a positive inotropic effect and ones decreasing contractility a negative inotropic effect. -Catecholamine's (Norepinephrine and epinephrine) released from the sympathetic neurons or adrenal medulla cause a positive inotropic effect regardless of EDV. -contractility increases as the amount of Ca2+ available for contraction increases.

Answer 24

1. Phosphorylation of Ca2+ channels increases calcium conductance during action potentials. 2. Phosphorylation of ryanodine receptors enhances sensitivity to Ca2+, increasing release of Ca2+ from the sarcoplasmic reticulum. 3. Increases rate of myosin ATPase 4. Phosphorylation of SERCA (PLN) increases the speed of Ca2+ re-uptake which increases Ca2+ storage.

Answer 25

1. Raising sarcomere length increases the Ca2+ sensitivity of the myofilaments. -a stretched sarcomere has a decreased diameter which may reduce the distance that Ca2+ needs to diffuse increasing probability of cross-bridge cycling. 2. Raising sarcomere length puts additional tension on stretch- activated Ca2+ channels, increasing Ca2+ entry from extracellular space and increasing Ca2+ induced Ca2+ release increasing tension.

Answer 26

-the amount of force developed by the cardiac muscle of a ventricle (as indicated by stroke volume) depends on the initial stretch of the ventricle walls (caused by ventricular filling) -the degree of myocardial stretch prior to contraction is known as the preload on the heart. According to frank-starling law, stroke volume increases with increasing end-diastolic volume.

Answer 27

- Increased venous return = increased venous pressure = increased atrial filling = increased ventricular filling Factors: 1. Skeletal muscle pump: Skeletal muscle activity compresses veins in the extremities pushing blood back to the heart. -increased muscle activity of the extremities can increase venous return. 2. Respiratory pump: during inspiration the chest expands and diaphragm moves down creating a subatmospheric pressure in the thoracic cavity, this draws blood into the vena cava that exist within this cavity -also during inspiration veins in the abdomen are compressed also forcing blood back to the heart. 3. Sympathetic constriction of veins: decreases their volume squeezing blood back towards that heart.

Answer 28

Afterload is the is the end load against which the heart contracts to eject blood -primarily determined by the combination of the EDV and the pressure in the outflow artery prior to contraction (aorta or pulmonary artery). -afterload can be increased in pathological situations (eg. increased arterial blood pressure, decreased aortic compliance) -clinically arterial blood pressure an indirect indicator of afterload

Answer 29

Arteries: Pressure resivoir that maintains blood flow during ventricular relaxation. Contains: thick smooth muscle layer and elastic fibrous connective tissue. Arterioles: site of variable resistance (diameter can change) - Mainly contain vascular smooth muscle Capillaries: exchange between blood and cells Veins: serve as an expandable volume resivoir All contain inner layer of thin endothelial cells and can be wrapped in a combination of elastic tissue, smooth muscle or fibrous tissue.

Answer 30

-the amount of smooth muscle in each vessel type varies -in most vascular smooth muscle there is always a state of partial contraction (tone) -vascular smooth muscle can be influenced by a variety of substances including neurotransmitters, hormones, paracrines -these substances bind receptors ultimately resulting in an increase in cytosolic Ca2+ causing contraction

Answer 31

The main determinant of resistance in the majority of arterioles is the sympathetic nervous system: -primarily sympathetic neurons innervate arterioles and tonically control arteriolar diameter through activation or deactivation of α1 adrenergic receptors. -Sympathetic neuron that release norepinephrine act on a receptors to change diameter of vessel - Moderate = intermediate diameter - increased norepinephrine = constriction of vessel - Decreased norepinephrine = dilation of vessel

Answer 32

-arterioles, capillaries and venules make up the microcirculation -across the microcirculation you have metarterioles which act as a capillary bypass vessels (also for WBC’s).

Answer 33

-smallest vessels in the cardiovascular system, where the majority of exchange between the blood and interstitial space occur. -single thin endothelial layer surrounded by a basal lamina (extracellular matrix) -gases can normally passively diffuse across the endothelial cells -linked by interendothelial junctions that also aid in the transport of small solutes and water -Some cells contain fenestrations, membrane lined conduits running through them to allow the transport -capillaries are often surrounded by pericytes (BBB)

Answer 34

A. Continuous capillary: most common -thicker endothelial cells that do not contain fenestrations. -Only allow passage of water and small ions through intercellular junctions B. Fenestrated capillary: thin endothelial cells that are perforated with fenestrations. The fenestrations often have a thin diaphragm. -small molecule passage C. Discontinuous (sinusoidal) capillary: lack a basal membrane, have large open fenestrations as well as gaps between the endothelial cells. (liver and spleen)

Answer 35

Transcellular transport- diffusion or osmosis across the endothelial cell membrane. -gases, small lipid soluble molecules, water (aquaporin channels). Paracellular transport: diffusion through interendothelial junctions, pores or fenestrations (water, small water soluble and small polar molecules). Transcytosis: the combination of endocytosis, vesicular transport, and exocytosis that transports macromolecules across endothelial cells.

Answer 36

Angiogenesis: the formation of new blood vessels -Angiogenic growth factors (mitogens-pro mitotic) activate receptors on endothelial cells -activated endothelial cells produce proteases that degrade the basal lamina so it can move away from the parent vessel -endothelial cells proliferate into the surrounding matrix and form sprouts towards the angiogenic stimulus in tandem. -sprouts then form loops to become a full- fledged vessel lumen as cells migrate to the site of angiogenesis

Answer 37

-pressure highest in the aorta and decreases throughout circuit -aortic pressure highest during ventricular contraction (systole): systolic pressure (120 mm Hg) and lowest during ventricular relaxation (diastole): diastolic pressure (80 mm Hg).

Answer 38

-the difference between the systolic and diastolic pressure is known as the pulse pressure Pulse pressure= systolic pressure-diastolic pressure - Pulse pressure normally only exists on the arterial/arteriole side of circuit

Answer 39

-because the pressure is pulsatile we look at a single value, the mean arterial blood pressure as the driving pressure for blood flow. -The mean arterial blood pressure is not simply the average of the systolic and diastolic pressures (100 mm Hg) because equal amounts of time are not spent in systole and diastole. MAP = Diastolic + 1/3 pulse pressure MAP & CO x peripheral resistance

Answer 40

- Hypertension represents when the blood pressure is chronically elevated (>140/90) • High pressure on the vessel walls can cause them to become weakened or even rupture and leak - Hypotension represents when the blood pressure falls too low (<90/60) • This can cause the driving force for blood flow to be inadequate to overcome the opposition by gravity - Cerebral hem orange: high BP in brain, can cause stroke

Answer 41

A tool to measure blood pressure Steps: 1. When the cuff is inflated so that it stops arterial blood flow, no sound can be heard through the stethoscope and the pressure measured is your systolic pressure 2. The pressure is slowly released and korotkoff sounds are created by turbulent blood flow.(arterie is still slightly compressed) 3. Blood flow is silent when the artery is no longer compressed the pressure measured is your diastolic

Answer 42

Determinants: 1. Blood volume: Fluid intake or fluid loss (may be regulated at kidneys or passive) 2. Effectiveness of the heart as a pump: Heart rate and stroke volume 3. Resistance of the system to blood flow: Diameter of the arterioles 4. Relative distribution of blood between arterial and venous blood vessels: Diameter of the veins

Answer 43

- Arteries are low-volume vessels that contain ~11% of the total blood volume at any one time -veins are high volume vessels and hold ~60% of the circulating blood volume at any one time

Answer 44

- Small changes in blood volume occur from ingestion of food and liquids. ~ primarily resolved by kidneys - Decreases in blood volume require an integrated response from the kidneys, the cardiovascular system (increase sympathetic output) and ingestion of fluid *Slide in notes with pathway*

Answer 45

Arterioles! - Vessels with the smallest radius theoretically should have the highest resistance (capillaries). Not the case -Aggregate (total) resistance not only depends on the radius of each vessel but also on how vessels are arranged (series vs parallel). - Because Capillaries are in parallel it lowers their resistance

Answer 46

1. Local control of arteriolar resistance matches tissue blood flow to the metabolic needs of the tissue: -in the heart and skeletal muscle, these local controls often take precedence over reflex control by the CNS 2. Sympathetic reflexes mediated by the CNS maintain mean arterial pressure and govern blood distribution for certain homeostatic needs such as temperature regulation. 3. Hormones-particularly those that regulate salt and water excretion by the kidneys, influence blood pressure by acting directly on the arterioles and by altering autonomic reflex control

Answer 47

- An example of local control of the dilation/constriction of arterioles. -an increase in blood pressure causes the vascular smooth muscle in the wall of the arteriole to stretch, which then causes the vascular smooth muscle to contract, leading to vasoconstriction. -arterioles contain a variety of stretch activated TRP channels, particularly TRPV2, TRPC6, and TRPM4 that are thought to be responsible for the mechano-depolarization leading to a myogenic response *Good flowchart on slide*

Answer 48

The main determinant of resistance in the majority of arterioles is the sympathetic nervous system: -primarily sympathetic neurons innervate arterioles and tonically control arteriolar diameter through activation or deactivation of α1 adrenergic receptors. -secondary mechanism involves release of epinephrine from the adrenal medulla in response to sympathetic activation -epinephrine has a low affinity for alpha receptors that cause vasoconstriction and a high affinity for B2 adrenergic receptors which lead to vasodilation -depends on relative amount of each receptor (eg. muscles more beta than alpha, GI more alpha than beta) - Epinephrine = Dilation

Answer 49

total blood flow through all the arterioles equals the CO -flow for each arteriole depends on the resistance, if an arteriole constricts resistance increases and blood flow through that arteriole decreases. Blood will take the path of least resistance. -eg skeletal muscle receives ~20% of CO at rest, but that can increase to as high as 85% during strenuous exercise -at rest regional amount of blood flow depends on the number and size of arteries feeding the organ -regional variations can occur because arterioles are arranged in parallel (in addition to series branching) meaning they all receive blood at the same time

Answer 50

The CNS coordinates reflex control of blood pressure and the distribution of blood to tissues -main integrating center: medullary cardiovascular control center (CVCC) -primary function: ensures adequate blood flow to the brain and heart by maintaining sufficient mean arterial pressure. -CVCC receives input from sensory receptors and other brain regions and has the ability to specifically alter function in a few organs or tissues

Answer 51

- The primary reflex pathway for homeostatic control of mean arterial blood pressure is the baroreceptor reflex -baroreceptors are tonically active stretch sensitive mechanoreceptors that are situated on the aorta and on the carotid artery -when there is an increase in blood pressure the baroreceptors sense the stretch in the artery walls and increase their firing rate -decrease blood pressure>decrease firing rate. - Reflex is constantly active

Answer 52

Peripheral chemoreceptors located on the aortic arch and carotid artery -sense alterations in blood-gas concentrations [O2], [CO2] as well as changes in blood pH -send information back to the cardiovascular control center which then results in a change in autonomic output to return blood gas levels to normal values. -peripheral chemoreceptor activation changes ventilation within the respiratory system

Answer 53

- The hypothalamus is capable of altering cardiovascular function in response to emotional stress - Some individuals faint in response to sudden emotional distress, sight of blood, phlebotomy (needle insertion), acute pain: Vasovagal syncope -results in a large increase in parasympathetic output (decrease CO) and reduction in sympathetic output (large decrease in peripheral resistance) (fall in blood pressure fails to activate normal baroreceptor response) -the combination of decreased CO and decreased peripheral resistance cause a large fall in mean arterial pressure, primarily parasympathetic decrease in HR

Answer 54

- bulk flow is the mass movement of fluid as the result of hydrostatic or osmotic pressure gradients. -if bulk flow is resulting in fluid moving into the capillaries, absorption is taking place -if bulk flow is resulting in the movement of fluid out of the capillaries this is filtration

Answer 55

-the pressure in the blood vessels drives fluid out of the capillaries through pores and cell junctions (filtration) and is known as the hydrostatic pressure (PH) -the pressure that draws fluid into the capillaries is the pressure created by plasma proteins in the blood and this is known as the colloid osmotic pressure or more simply oncotic pressure (π) (it is the osmotic pressure created by proteins).

Answer 56

-π steady in the capillary and exceeds the interstitial space π (zero) - PH in vessels decreases as blood travels through the capillaries due to the resistance encountered and exceeds interstitial PH (zero) -at the arterial end PH exceeds π causing net filtration -at the venous end π exceeds PH and there is absorption -overall, there is a net filtration from the entire capillary network resulting in a loss of 3L of fluid/day from the blood If PH > Pi then there is net filtration If PH < Pi then there is net absorption

Answer 57

- lymphatic vessels assist the cardiovascular system with returning fluid and proteins lost through the capillaries -similar to capillaries, single endothelial cell layer -contain large interendothelial junctions that act like one way valves -nodes distributed throughout the lymphatic system contain immune cells

Answer 58

- In the intital lymphatic segment, the interstitial hydrostatic pressure is higher than inside the lymphatic causing the microvalves to open and fluid to flow in. - As it fills up with fluid the lymphatic hydrostatic pressure exceeds interstitial, the microvalves close and the secondary valves open. - Collecting lymphatics contain smooth muscle that actively contract to propel fluid and one way valves to prevent backflow, skeletal muscle assists as well

Answer 59

Edema: An abnormal accumulation of fluid in the interstitial space Arises for two different reasons: 1. Inadequate lymph drainage: can occur from obstructions in the lymphatic system particularly within the lymph nodes. 2. A disruption in normal balance between capillary filtration and absorption(filtration>absorption): i. Increased capillary hydrostatic pressure (heart failure) ii. decrease in plasma protein concentration (malnutrition, liver failure) iii. increase in interstitial proteins (excessive leakage of proteins out of capillaries):injury, inflammation https://upload.wikimedia.org/wikipedia/commons/8/84/Combinpedal.jpg

Answer 60

Inflammatory process leading to hardening or narrowing of arteries -The role of elevated blood cholesterol is well established -cholesterol is not readily soluble in aqueous solutions, joins with lipoproteins Clinicians concerned with two types of lipoproteins: 1. High-density lipoprotein-cholesterol complexes (HDL-C) High levels associated with lower risk of heart attack (H-healthy) 2. Low-density lipoprotein-cholesterol complexes (LDL-C) “bad” cholesterol, elevated levels associated with coronary heart disease Necessary for cholesterol transport in to cells, LDL-C’s proteins are digested to amino acids and the freed cholesterol is used to make cell membranes and steroid hormones

Answer 61

See 58 wk 13/14

Answer 62

• If a clot blocks blood flow to the heart muscle, a myocardial infarction (heart attack) ensues • Lack of O2 leads to ATP supply declining, the contractile cells become unable to remove Ca2+ from cytosol •High intracellular[Ca2+] closes gap junctions in the damaged cells, electrically isolating them. • If the damaged region of myocardium is large, disruption can cause an irregular heart beat (arrhythmia) potentially leading to cardiac arrest or death • Atherosclerosis in brain vasculature account for 50% of strokes

Answer 63

-doubles the risk for CVD for each 20/10 mmHg increase in blood pressure above the baseline value of 115/75 - 62 wk 13/14 Effects of hypertension -adaption of the baroreceptors to higher pressure with a down regulation of their activity - is a risk factor for atherosclerosis, the increased pressure exerted on arterial walls damages the endothelial cell lining and promotes plaque formation -hypertension increases afterload -over time the increased force the heart must over come causes myocardial contractile cells to undergo hypertrophy -eventually the heart cannot meet work load and begins to fail

Answer 64

• Ca2+ channel blockers (L-type) to relax the vascular smooth muscle and/or decrease CO (HR and force of contraction) • Diuretics increase urination removing excess fluid to decrease blood volume • Beta blockers block B1 adrenergic receptors decreasing CO • ACE inhibitors and angiotensin receptor blockers prevent vasoconstriction from renin-angiotensin aldosterone axis

Answer 65

A connective tissue composed of cellular elements suspended in an extensive fluid matrix that circulates in the CV system. • Total blood volume:~7-8%of total body weight: • 70mL/1 kg body weight in an adult female and ~80mL/kg body weight in an adult male. • Hematocrit(40-45%)is the fraction of the total column occupied by RBC’s • Buffy coat is WBC’s and platelets (1%<) • Plasma(55-60%):pale white solution of electrolytes, plasma proteins, carbohydrates and lipids.

Answer 66

A type of plasma protien: - Account for ~60% of plasma proteins - Come from the liver - Function as: contributors to colloid osmotic pressure of plasma; carriers for various substances.

Answer 67

A type of plasma protien: - Come from the liver and lymphoid tissue - Function as: clotting factors, enzymes, antibodies, carriers for various substances

Answer 68

A type of plasma protien: - Come from the liver - Function as: Forming fibrin threads that are essential to blood clotting

Answer 69

A type of plasma protien: - Come from the liver and other tissues - Function as: iron transport

Answer 70

Hematopoiesis-production of blood cells In adult: pelvis, spine, ribs, cranium and proximal ends of long bones. Hematopoiesis: lineage development guided by cytokines (cell signaling molecules) Guided by cytokines: Proteins or peptides released from one cell that affect growth or activity in another cell Begins with a pluripotent hematopoietic stem cell > uncommitted stem cells > stem cells > circulation

Answer 71

Erythropoiesis-RBC production (EPO): kidney cells ~ stimulated by low O2 Leukopoiesis- Leukocyte (WBC) production (CSF’s) Thrombopoiesis-Thrombocyte (platelet) production (TPO): liver

Answer 72

- Most abundant cell type in the blood (5 million/ul) (~4 month lifespan) - Non-nucleated biconcave cells with diameter ~7.5um distinctive shape increases surface to volume ratio, decreases diffusion distance - Shape: Allows them to squeeze through capillaries, respond to osmotic changes, provide evidence of disease RBC’s three major tasks: 1. Carrying O2 from the lungs to the systemic tissue 2. Carrying CO2 from the tissues to the lungs 3. Assisting in the buffering of acids and bases.

Answer 73

RBC’s mainly consist of hemoglobin: the O2 transport protein ~96% of dry weight Consists of: - globin proteins: alpha, beta, gamma or delta -most common two alpha and two beta chains, each contain heme group -70% of iron in the body found in heme groups of hemoglobin -each heme group can bind one oxygen (O2) molecule

Answer 74

1. Iron injested from diet 2. Fe absorbed by active transport 3. Transferrin protein transports Fe in plasma 4. Bone marrow uses Fe to make hemoglobin as part of RBC synthesis 5. RBCs live about 120 days in the blood 6. Spleen destroys old RBCs and converts Hb to bilirubin 7. Bilirubin and metabolites are excreted in urine and feces 8. Liver metabolizes bilirubin and excretes it in bile 9. Liver stores excess Fe as ferritin

Answer 75

1. Granulocytes: contain cytoplasmic granules visualized under microscope -brief lifespan in the blood < 12hours, but if activated can migrate into tissues for longer time. Neutrophil: most abundant leukocyte, contain granules with lysosomal enzymes capable of digesting foreign material (phagocytosis). Eosinophil: granules contain Major Basic Protein (MBP) which is toxic to parasites and other enzymes. Important in response to virus’ and in allergic reactions Basophil: least common granulocyte, granules contain histamine, heparin and peroxidase and play a role in allergic reactions

Answer 76

2. Non-granule containing lymphocytes and monocytes Lymphocytes: two types T-lymphocytes and B lymphocytes (T-Cell, B-cell); Adaptive immunity. -T-cells 70-80% of all lymphocytes and responsible for cell mediated immunity, does not involve antibodies. (TMem, TReg THelp, TNK...) -B-cells: responsible for humoral immunity, make antibodies to antigens (Bmem, Breg ....) Monocytes: spend life in peripheral tissues developing into macrophages, which serve two purposes: 1. Phagocytosis of pathogens or cellular debris 2. Present antigens to lymphocytes

Answer 77

• Nucleus-free fragment’s of megakaryocytes, 2-3umin diameter in their inactive state ~10 day life span. • Contain two special types of granules - Densecoregranules - α-granules -contain ATP, ADP, serotonin, Ca2+, von Willebrand factor, platelet activating factor, platelet fibrinogen, and clotting factor V • Essential for hemostasis, the process which keeps blood within a damaged vessel

Answer 78

Hemostasis: the prevention of hemorrhage (bleeding) from a damaged vessel

Answer 79

1. Vasoconstriction: contributes to hemostasis by closing the vessel and preventing blood flow to the damaged region. -can be triggered by direct injury to vascular smooth muscle, the release of paracrine signals from damaged endothelial cells (endothelin) or platelets (serotonin, thromboxane A2) -bring down the pressure within the vessel so a secure mechanical seal can be applied in the form of a clot

Answer 80

2. Platelet plug formation: -inactivated platelets do not adhere to themselves or to the intact endothelium cells that line the vessel (possibly due to like charges) -platelets contain cell surface receptors (integrins) - A breach of the endothelium exposes integrins to collagen, fibronectin and laminin, which are all part of the subendothelial layer causing platelets to bind.

Answer 81

- binding of integrins causes the activation of an intracellular signaling pathway in platelets causing them to release the contents of their granules: serotonin (vasoconstrictor), ADP and platelet-activating factor (PAF-activates more platelets) -PAF signals platelets to release thromboxane A2 (vasoconstrictor) -morphological changes, platelet extends many finger-like filopodia - Intact endothelial cells release substances to prevent activated platelets from binding

Answer 82

- ADP, serotonin and thromboxane A2 released all activate additional platelets causing them to recruit to the site and aggregate -von Willebrand factor causes platelets to form molecular bridges between one another.

Answer 83

-Intrinsic pathway: A plasma protein in the blood known as factor XII is converted to factor XIIa (activated form) when it comes into contact with an activated platelet or damaged vessel wall -Final product is factor Xa through a series of proteolytic steps.

Answer 84

Extrinsic pathway: another cascade of protease reactions occurring outside the vascular system. -subendothelial cells express a membrane protein known as tissue factor, which is a receptor for a plasma protein, factor VII -when factor VII leaves vessel through damaged region and comes into contact with tissue factor its converted (non-proteolytically) to factor VIIa - Tissue factor, factor VIIa and Ca2+ form a complex that proteolytically cleaves factor X to produce factor Xa -factor Xa produced from either the intrinsic or extrinsic pathway is important for the common pathway

Answer 85

Common pathway: -factor Xa produced from the intrinsic and extrinsic pathway join together with factor Va and Ca2+ to create prothrombinase. -Prothrombinase converts prothrombin to thrombin -thrombin is a central protease of the coagulation cascade -Fibrinogen (one of the main plasma proteins in blood) is then cleaved by thrombin to fibrin monomers -the fibrin monomers spontaneously polymerize to form a gel of fibrin polymers that weaves through plug and traps blood cells. -thrombin also activates factor XIII to XIIIa which assists in forming the fibrin polymers into a stable fibrin mesh.

Answer 86

3. Coagulation – Intrinsic pathway (surface contact pathway) • Factor XII is activated when contacting exposed collagen, activated platelets • Final product is factor Xa – Extrinsic pathway (cell injury pathway) • Factor VII leaves vessel and binds to tissue factor receptor and become activated Factor VIIa • Final product is factor Xa – Common pathway • Factor Xa from intrinsic and extrinsic is used to create thrombin which ultimately converts fibrinogen to a stable fibrin clot

Answer 87

- A name given to several diseases in which one of the factors in the coagulation cascade is defective or lacking. -bruise easily, spontaneous bleeding -bleeding in the joints and muscles can be painful and disabling and if bleeding occurs in the brain it can be fatal. Types: • Hemophilia A: a factor VIII deficiency – Mostcommon~80%ofcases • Hemophilia B: factor IX deficiency • Both X-linked recessive Treatment: • Treated with synthetic factors • Just recently AAV treatment increased factor production in clinical trials

Answer 88

- Too much coagulation can be a very bad thing (Thrombus: stroke, heart attack, pulmonary embolism). - Endothelial cells also produce a variety of anticoagulant factors that interfere with the clotting cascade. - Prostacyclin and NO prevent platelet binding

Answer 89

The breakdown of blood clots: -Begins with the conversion of plasminogen (produced in liver) to plasmin through proteolysis. -endothelial cells produce tissue plasminogen activator (t-PA) that causes this conversion -Plasmin is capable of breaking down both stable fibrin as well as fibrinogen Fibrinogen > fibrin polymer > fibrin fragments

Cardiac Flashcards

(119 cards)