Chapter 13: Blood, Heart, Circulation Flashcards
(203 cards)
1
Q
What are the three main functions of the circulatory system?
A
- Transportation: Transports respiratory gases (O2 and CO2) nutrients and wastes. 2. Regulation: Maintains homeostasis through hormonal regulation and temperature control. 3. Protection: Provides defense against pathogens (immunity) and facilitates clotting to prevent blood loss.
2
Q
What are the major components of the circulatory system?
A
- Cardiovascular system: Includes the heart (four-chambered pump) blood vessels (arteries arterioles capillaries venules and veins) and blood (cells and plasma). 2. Lymphatic system: Composed of lymphatic vessels lymphoid tissues and lymphatic organs such as the spleen thymus tonsils and lymph nodes. It also includes lymph the fluid that returns to the bloodstream.
3
Q
What is the role of the heart in the circulatory system?
A
The heart acts as a four-chambered pump that facilitates blood circulation supplying oxygenated blood to the body (systemic circulation) and deoxygenating blood to the lungs (pulmonary circulation).
4
Q
What types of blood vessels are included in the circulatory system and their functions?
A
- Arteries: Carry oxygenated blood away from the heart. 2. Arterioles: Smaller branches of arteries that regulate blood flow to capillaries. 3. Capillaries: Microscopic vessels where gas and nutrient exchange occurs. 4. Venules: Small vessels that collect blood from capillaries. 5. Veins: Carry deoxygenated blood back toward the heart.
5
Q
What is lymph and its significance?
A
Lymph is a fluid in the lymphatic system that originates from blood plasma. It is essential for returning proteins excess interstitial fluid and immune cells to the bloodstream thus maintaining fluid balance and providing immunity.
6
Q
What role do lymphatic organs play in the lymphatic system?
A
Lymphatic organs such as the spleen thymus tonsils and lymph nodes are involved in filtering lymph producing lymphocytes (a type of white blood cell) and responding to infections thereby enhancing immunity.
7
Q
What is the composition of blood?
A
Blood consists of plasma (which makes up about 55% of blood volume) and formed elements including red blood cells (erythrocytes) white blood cells (leukocytes) and platelets (thrombocytes). It is critical for transport regulation and protection.
8
Q
What is the average blood composition in terms of cells and plasma?
A
Blood is composed of approximately 45% formed elements (red blood cells white blood cells and platelets) and 55% plasma which contains water electrolytes proteins hormones nutrients and waste products.
9
Q
What is the average adult blood volume?
A
The average adult blood volume is about 5 liters.
10
Q
What is the characteristic of arterial blood leaving the heart?
A
Arterial blood leaving the heart is bright red oxygenated except for blood going to the lungs.
11
Q
What is the characteristic of venous blood entering the heart?
A
Venous blood entering the heart is dark red deoxygenated except for blood coming from the lungs.
12
Q
What are the main components of blood composition?
A
Blood is made up of approximately 45% formed elements and 55% plasma.
13
Q
What is plasma?
A
Plasma is the straw-colored fluid part of blood that does not contain cells and forms extracellular fluid.
14
Q
What are the main components of plasma?
A
The main components of plasma include water and dissolved solutes such as proteins and ions as well as organic molecules like metabolites hormones enzymes and antibodies.
15
Q
What percentage of plasma is made up of plasma proteins?
A
Plasma proteins make up 7 to 9% of the plasma.
16
Q
What is the function of albumin in blood plasma?
A
Albumin creates osmotic pressure to help draw water from tissues into capillaries to maintain blood volume and pressure.
17
Q
What is the role of globulins in plasma?
A
Globulins include alpha and beta globulins that transport lipids and fat-soluble vitamins and gamma globulins which are antibodies that function in immunity.
18
Q
What is the function of fibrinogen in plasma?
A
Fibrinogen aids in clotting after it converts to fibrin.
19
Q
How do regulatory mechanisms affect plasma volume?
A
Regulatory mechanisms are in place to maintain plasma volume at appropriate levels aiding in bodily functions.
20
Q
What triggers the release of ADH from the posterior pituitary gland?
A
Osmoreceptors in the hypothalamus trigger the release of ADH (Antidiuretic Hormone) when fluid is lost.
21
Q
What is the primary function of erythrocytes (red blood cells)?
A
The primary function of erythrocytes (RBCs) is to carry oxygen from the lungs to the tissues and return carbon dioxide from the tissues back to the lungs.
22
Q
What shape do erythrocytes have?
A
Erythrocytes have a flattened biconcave disc shape.
23
Q
Do erythrocytes contain nuclei and mitochondria?
A
No erythrocytes lack nuclei and mitochondria.
24
Q
What is the normal count of erythrocytes per mm³ of blood?
A
There are approximately 5 million erythrocytes per mm³ of blood.
25
What is the life span of an erythrocyte?
Erythrocytes have a life span of about 120 days.
26
Where are erythrocytes removed from circulation?
Erythrocytes are removed by phagocytic cells in the liver spleen and bone marrow.
27
How many hemoglobin molecules does each erythrocyte contain?
Each erythrocyte contains about 280 million hemoglobin molecules.
28
What are leukocytes?
Leukocytes are white blood cells (WBCs) that play an important role in the immune response.
29
Do leukocytes contain nuclei and mitochondria?
Yes leukocytes have nuclei and mitochondria.
30
How do leukocytes move?
Leukocytes move in an amoeboid fashion.
31
What is diapedesis in the context of leukocytes?
Diapedesis refers to the extravasation movement of leukocytes allowing them to move out of blood vessels and into tissues.
32
What is the normal count range of blood cells in mm³?
Approximately 5000 to 9000 mm³ blood for leukocytes.
33
What are the types of leukocytes?
1. Granular leukocytes (granulocytes) - Neutrophils Eosinophils Basophils. 2. Agranular leukocytes (agranulocytes) - Monocytes Lymphocytes.
34
What are the formed elements of blood?
1. Red Blood Cells (Erythrocytes) 2. White Blood Cells (Leukocytes) 3. Platelets (Thrombocytes).
35
What are platelets and their characteristics?
1. Smallest formed element. 2. Fragments of large cells called megakaryocytes. 3. Lack nuclei. 4. Very short-lived (5 to 9 days). 5. Forms fibrin to clot blood alongside fibrinogen and other chemicals. 6. Release serotonin to stimulate vasoconstriction and secrete growth factors.
36
What is the normal count range for platelets in mm³?
130000 to 400000 mm³ blood.
37
Define anemia and its relation to red blood cells (RBCs).
Anemia is characterized by an abnormally low count of red blood cells (RBCs).
38
Define polycythemia and its relation to red blood cells (RBCs).
Polycythemia is characterized by an abnormally high count of red blood cells (RBCs).
39
Define leukopenia and its relation to white blood cells (WBCs).
Leukopenia is characterized by an abnormally low count of white blood cells (WBCs).
40
Define leukocytosis and its relation to white blood cells (WBCs).
Leukocytosis is characterized by an abnormally high count of white blood cells (WBCs).
41
What is leukemia?
Leukemia is a cancer of the bone marrow that causes a high number of abnormal immature white blood cells (WBCs).
42
What is hematopoiesis (hemopoiesis)?
Hematopoiesis is the process of blood cell formation.
43
What are hematopoietic stem cells?
Hematopoietic stem cells are embryonic cells that give rise to all types of blood cells. They are characterized by their ability to self-renew through mitotic division.
44
Where does hematopoiesis occur after birth?
Hematopoiesis occurs in myeloid tissue primarily in red bone marrow and also in lymphoid tissue.
45
What is the definition of hematopoiesis?
Hematopoiesis also known as hemopoiesis is the process of blood cell formation.
46
What is erythropoiesis?
Erythropoiesis is the formation of red blood cells specifically from precursor cells known as erythroblasts.
47
How many red blood cells are produced by red bone marrow per second?
Red bone marrow produces approximately 2.5 million red blood cells (RBCs) per second.
48
What regulates the process of erythropoiesis?
Erythropoiesis is regulated by erythropoietin a hormone produced by the kidneys which responds to low blood oxygen (O2) levels.
49
How long does the process of erythropoiesis take?
The process of erythropoiesis takes about 3 days from the formation of erythroblasts to the maturation of red blood cells.
50
What are antigens and where are they found?
Antigens are molecules found on the surface of cells that help the immune system recognize self-cells.
51
What role do antibodies play in the immune system?
Antibodies which are secreted by lymphocytes bind to foreign antigens to help identify and neutralize pathogens.
52
How does low blood O2 levels affect erythropoiesis?
Low blood O2 levels stimulate the production of erythropoietin from the kidneys which in turn increases the production of red blood cells in the bone marrow.
53
What type of cells do hematopoietic stem cells differentiate into?
Hematopoietic stem cells differentiate into various blood cell types including red blood cells white blood cells and platelets.
54
What is the source of erythropoietin?
Erythropoietin is primarily produced by the kidneys.
55
What is the significance of the red blood cell production rate of 2.5 million cells per second?
The high rate of red blood cell production ensures adequate oxygen transport in the body adapting to the body's changing oxygen demands.
56
What type of tissue produces blood cells?
Blood cells are produced in myeloid tissue (red bone marrow) and lymphoid tissue.
57
What happens if erythropoiesis is not adequately stimulated?
If erythropoiesis is not adequately stimulated the body may experience anemia where there are insufficient red blood cells to transport adequate oxygen.
58
Describe the role of lymphocytes in relation to blood antigens.
Lymphocytes are a type of white blood cell that produces antibodies. These antibodies target specific antigens on pathogens or foreign cells aiding in the immune response.
59
What are the antigens present on erythrocyte (red blood cell) surfaces for Type A blood?
Type A blood has the A antigen present on the erythrocyte surface.
60
What are the antigens present on erythrocyte surfaces for Type B blood?
Type B blood has the B antigen present on the erythrocyte surface.
61
What antigens are present on erythrocytes for Type AB blood?
Type AB blood has both A and B antigens present on the erythrocyte surface.
62
What antigens are present on erythrocytes for Type O blood?
Type O blood has neither A nor B antigens present on the erythrocyte surface.
63
What antibodies does Type A blood plasma contain?
Type A blood plasma contains anti-B antibodies.
64
What antibodies does Type B blood plasma contain?
Type B blood plasma contains anti-A antibodies.
65
What antibodies are present in Type AB blood plasma?
Type AB blood plasma contains no antibodies against A or B antigens making it the universal recipient.
66
What antibodies does Type O blood plasma contain?
Type O blood plasma contains both anti-A and anti-B antibodies making it the universal donor.
67
What is a transfusion reaction?
A transfusion reaction occurs when a person receives blood of an incompatible type leading to antibodies binding to erythrocytes and causing agglutination.
68
What is agglutination in the context of blood typing?
Agglutination is the clumping of red blood cells that occurs when antibodies in the plasma bind to specific antigens on the erythrocytes. This reaction can be used to determine blood types.
69
What is the Rh factor?
The Rh factor is an antigen specifically the D antigen (or RhoD) that can be present on the surface of red blood cells.
70
What characterizes Rh-positive blood?
Rh-positive blood has the D antigen present on its erythrocytes.
71
What characterizes Rh-negative blood?
Rh-negative blood does not have the D antigen on its erythrocytes.
72
When does a Rh-negative person develop antibodies against the Rh factor?
A Rh-negative person will develop antibodies against the Rh factor only if exposed to Rh-positive blood such as through a blood transfusion or during pregnancy.
73
What are the implications of receiving the wrong blood type during a transfusion?
Receiving the wrong blood type can lead to serious health complications due to the immune response caused by agglutination of the recipient's antibodies binding to the donated erythrocytes.
74
What is the significance of understanding ABO and Rh blood typing systems?
Understanding ABO and Rh blood typing systems is critical in medicine for ensuring safe blood transfusions preventing transfusion reactions and managing pregnancy-related complications.
75
What is the Rh factor?
The Rh factor is an antigen that can be present on the surface of red blood cells specifically referred to as Antigen D or RhoD.
76
What distinguishes Rh-positive from Rh-negative blood types?
Rh-positive blood types have the Rh antigen (Antigen D) present while Rh-negative blood types do not have this antigen.
77
Can an Rh-negative individual have antibodies against the Rh factor?
No an Rh-negative individual will not have antibodies against the Rh factor unless they are exposed to Rh-positive blood through a blood transfusion or during pregnancy.
78
What is hemostasis?
Hemostasis is the process of cessation of bleeding when a blood vessel is damaged.
79
List the three steps involved in hemostasis.
1. Vasoconstriction 2. Formation of a platelet plug 3. Formation of a fibrin protein web.
80
What occurs during the vasoconstriction phase of hemostasis?
During vasoconstriction the blood vessels narrow to reduce blood flow which helps minimize blood loss.
81
What role do platelets play in forming a platelet plug?
Platelets bind to exposed collagen fibers in damaged blood vessels and recruit more platelets by secreting chemicals like ADP which makes them sticky.
82
What is the function of prostacyclin (PGI2) and nitric oxide in the context of blood vessels?
Prostacyclin (PGI2) and nitric oxide secreted by intact endothelium serve to vasodilate and inhibit platelet aggregation helping to maintain normal blood flow and prevent unnecessary clotting.
83
What happens to the endothelium of blood vessels when they are damaged?
When the endothelium is damaged it exposes collagen fibers which leads to changes in platelet behavior including adhesion and activation.
84
What role does von Willebrand factor (VWF) play in hemostasis?
Von Willebrand factor (VWF) helps to mediate the binding of platelets to collagen by holding them in place at the site of injury.
85
What are the biochemical agents released by activated platelets during hemostasis?
Activated platelets release several agents including ADP (which promotes platelet stickiness) serotonin (which promotes vasoconstriction) and thromboxane A2 (which promotes both platelet aggregation and vasoconstriction).
86
What is the purpose of the fibrin protein web in blood clotting?
The fibrin protein web stabilizes the platelet plug by creating a mesh-like structure that traps blood cells thereby forming a more solidified clot to prevent further bleeding.
87
What is the primary outcome of the platelet activation process?
The primary outcome of the platelet activation process is the formation of a stable blood clot that effectively prevents blood loss following vascular injury.
88
What role do platelets play in blood clotting?
Platelets activate plasma clotting factors and facilitate the process of forming a blood clot by aggregating at the site of injury.
89
What are the two pathways for the conversion of fibrinogen to fibrin?
1. Intrinsic contact pathway: Activated by exposure to collagen polyphosphates and NETS Factor XII activates a cascade of other blood factors which amplifies the extrinsic pathway. 2. Extrinsic pathway: Initiated by tissue thromboplastin (factor III) this pathway is more direct and shorter.
90
What is the role of calcium and phospholipids in the clotting process?
Calcium and phospholipids derived from platelets are crucial for converting prothrombin to thrombin which in turn converts fibrinogen to fibrin.
91
What is the function of vitamin K in blood clotting?
Vitamin K is essential for the liver to synthesize several clotting factors necessary for the coagulation process.
92
What is the significance of Fibrinogen in the clotting process?
Fibrinogen is converted into fibrin which is essential for the formation of a stable blood clot.
93
What is the current understanding of Factor VI in the context of coagulation?
Factor VI is no longer referenced separately and is believed to be the same substance as activated Factor V.
94
List the main plasma clotting factors and their functions.
1. Factor I (Fibrinogen): Converted to fibrin in the common pathway. 2. Factor II (Prothrombin): Converted to thrombin.
95
Explain the intrinsic and extrinsic pathways of clotting in terms of their activation.
The intrinsic pathway is activated by contact with collagen or certain negatively charged surfaces while the extrinsic pathway is activated by tissue injury leading to the exposure of tissue factor (thromboplastin).
96
What happens when thrombin is produced during blood clotting?
Thrombin converts fibrinogen into fibrin leading to the formation of a fibrin mesh that stabilizes the platelet plug in a blood clot.
97
Describe the cascade effect in the intrinsic pathway of coagulation.
In the intrinsic pathway once Factor XII is activated it catalyzes a series of reactions leading to the activation of various other clotting factors ultimately enhancing the coagulation process.
98
Why is understanding the clotting process important in medicine?
Understanding the clotting process is essential for diagnosing and treating bleeding disorders thrombotic conditions and managing surgical risks related to blood loss.
99
What is thrombin and what role does it play in blood clotting?
Thrombin is an enzyme that plays a key role in the common pathway of blood clotting. It converts fibrinogen into fibrin which is essential for the formation of blood clots.
100
What is the significance of tissue thromboplastin in the clotting process?
Tissue thromboplastin also known as thromboplastin is a cofactor that initiates the extrinsic pathway of blood coagulation. It interacts with factor VII to activate factor X.
101
Describe the function of calcium ions (Ca2+) in the blood clotting process.
Calcium ions (Ca2+) act as a cofactor in both the intrinsic and extrinsic pathways of coagulation. They are essential for the activation of various clotting factors and contribute to the overall clotting cascade.
102
What is Proaccelerin and what is its role in the coagulation cascade?
Proaccelerin also known as factor V is a cofactor in the common pathway of the blood clotting process. It works alongside thrombin to convert prothrombin into thrombin.
103
What is Proconvertin and which pathway does it participate in?
Proconvertin also known as factor VII is an enzyme that participates in the extrinsic pathway of blood coagulation. It activates factor X in the presence of tissue thromboplastin and calcium ions.
104
What is the Antihemophilic factor and what pathway does it belong to?
The Antihemophilic factor known as factor VIII is a cofactor in the intrinsic pathway of blood coagulation. It works with factor IX to activate factor X.
105
What is the role of the Plasma thromboplastin component (Christmas factor) in the coagulation cascade?
The Plasma thromboplastin component also known as factor IX or Christmas factor is an enzyme that participates in the intrinsic pathway of blood coagulation facilitating the activation of factor X.
106
Describe the function of Stuart - Prower factor in blood clotting.
Stuart - Prower factor or factor X is an enzyme in the common pathway of coagulation. It is responsible for converting prothrombin to thrombin when activated.
107
What is the role of Plasma thromboplastin antecedent in the coagulation process?
Plasma thromboplastin antecedent is also known as factor XI and functions as an enzyme in the intrinsic pathway. It activates factor IX thereby promoting further coagulation processes.
108
What is the Hageman factor and its role in blood clotting?
Hageman factor known as factor XII is an enzyme involved in initiating the intrinsic pathway of blood coagulation. It activates factor XI when in contact with negatively charged surfaces.
109
What is the significance of Fibrin stabilizing factor in the clotting process?
Fibrin stabilizing factor or factor XIII is an enzyme in the common pathway of coagulation. It cross-links fibrin fibers stabilizing the clot to enhance its integrity.
110
What is the process for the dissolution of clots regarding Factor XII?
Factor XII converts an inactive plasma molecule into kallikrein which then catalyzes the conversion of plasminogen to plasmin allowing for the digestion of fibrin and subsequent dissolution of the clot.
111
What role does plasmin play in blood clotting?
Plasmin is an enzyme that digests fibrin which is vital for the dissolution of blood clots allowing for the restoration of normal blood flow after the healing process.
112
What are anticoagulants and how do they function?
Anticoagulants are substances that prevent blood clotting. They can include drugs that act as calcium chelators which prevent the clotting process by binding calcium ions necessary for the activation of clotting factors.
113
What is the role of sodium citrate in anticoagulation?
Sodium citrate is an anticoagulant that works by binding calcium ions in the blood thereby preventing coagulation by inhibiting the clotting cascade.
114
How does EDTA function as an anticoagulant?
EDTA (Ethylenediaminetetraacetic acid) functions as an anticoagulant by chelating calcium ions which are essential for blood coagulation processes.
115
What is the mechanism of action of heparin regarding thrombin?
Heparin inactivates thrombin and factor Xa through the formation of a heparin-antithrombin complex effectively reducing the body's ability to form blood clots.
116
What is the primary action of Warfarin (Coumadin) in the body?
Warfarin (Coumadin) functions by inhibiting the synthesis of vitamin K-dependent clotting factors (II VII IX and X) in the liver thereby preventing thrombus formation.
117
What is Rivaroxaban (Xarelto) and how does it work as an anticoagulant?
Rivaroxaban (Xarelto) is an oral anticoagulant that inhibits Factor Xa essential for the conversion of prothrombin to thrombin in the coagulation cascade.
118
What genetic trait is associated with hemophilia?
Hemophilia is associated with an X-linked recessive trait meaning it primarily affects males as they have only one X chromosome.
119
What is Von Willebrand's disease and how does it differ from hemophilia?
Von Willebrand's disease is a bleeding disorder caused by a defect in von Willebrand factor which affects platelet function and is different from hemophilia which is caused by deficiencies in specific clotting factors.
120
What is the most common bleeding disorder?
Von Willebrand's disease is the most common bleeding disorder.
121
Define the cardiac cycle. What are its phases?
The cardiac cycle is the repeating pattern of contraction (systole) and relaxation (diastole) of the heart that allows for blood pumping.
122
What occurs during the systole phase of the cardiac cycle?
During systole the heart muscles contract pumping blood out of the ventricles into the arteries.
123
What is diastole in the cardiac cycle?
Diastole is the phase of the cardiac cycle in which the heart muscles relax allowing the chambers to fill with blood.
124
What is end-diastolic volume (EDV)?
End-diastolic volume (EDV) is the total volume of blood in the ventricles at the end of diastole right before the heart contracts.
125
What is end-systolic volume (ESV)?
End-systolic volume (ESV) is the amount of blood left in the left ventricle after systole indicating how much blood was not ejected during contraction.
126
What is the significance of measuring the stroke volume?
Stroke volume is the amount of blood ejected from the left ventricle during each contraction and is crucial for assessing cardiac output and overall heart function.
127
What is Stroke Volume (SV)?
Stroke Volume is the amount of blood pumped by the heart with each beat. It is a crucial measure of heart function and is typically expressed in milliliters.
128
What is Ejection Fraction (EF)?
Ejection Fraction is the percentage of blood that is pumped out of the ventricles each time the heart beats. It is calculated using the formula: EF = (SV / End-Diastolic Volume) x 100. An EF of 55% to 70% is considered normal.
129
How are Stroke Volume and Ejection Fraction related?
Stroke Volume and Ejection Fraction are interconnected; while Stroke Volume indicates the absolute volume of blood ejected per heartbeat Ejection Fraction provides a percentage that reflects the efficiency of the heart's pumps relative to the volume of blood in the ventricle just before contraction.
130
What is the average cardiac rate and how does it relate to the cardiac cycle?
The average cardiac rate is approximately 75 beats per minute which implies that each cardiac cycle lasts about 0.8 seconds.
131
Describe the events occurring during the isovolumetric contraction phase of the cardiac cycle.
During isovolumetric contraction the ventricles begin to contract causing the pressure within them to rise. This increase in pressure results in the closure of the AV (atrioventricular) valves which creates the 'lub' sound.
132
What happens during the ejection phase of the cardiac cycle?
In the ejection phase as the pressure in the ventricles continues to rise the semilunar valves open. This allows blood to be ejected from the ventricles into the arteries.
133
What occurs during the isovolumetric relaxation phase of the cardiac cycle?
During isovolumetric relaxation the pressure in the ventricles falls below that in the arteries leading to the closure of the semilunar valves generating the 'dub' sound. Both sets of heart valves (AV and semilunar) are closed during this phase.
134
What happens when the pressure in the ventricles falls below that in the atria?
When the ventricle pressure falls below atrial pressure the AV (atrioventricular) valves open allowing blood to flow from the atria into the ventricles.
135
What is the role of atrial contraction in the cardiac cycle?
Atrial contraction occurs after the ventricles fill with blood. It sends the final volume of blood into the ventricles completing the filling process before the next contraction.
136
What is the resting potential of cardiac muscle cells?
Cardiac muscle cells have a resting potential of approximately -85 mV.
137
How are myocardial action potentials initiated?
Myocardial action potentials are initiated when the cells are depolarized to threshold by action potentials from the SA (sinoatrial) node which is the heart's natural pacemaker.
138
What effect do sympathetic neurotransmitters such as epinephrine and norepinephrine have on the heart?
Sympathetic neurotransmitters like epinephrine and norepinephrine increase heart rate and enhance the strength of cardiac muscle contractions.
139
What is the significance of the SA node in the heart's electrical system?
The SA node is critical as it generates action potentials that regulate the heart's rhythm initiating the contraction cycle and influencing heart rate.
140
What neurotransmitter do parasympathetic neurons secrete to influence heart rate?
Parasympathetic neurons secrete acetylcholine.
141
How does acetylcholine affect the heart rate?
Acetylcholine opens potassium (K) channels which slows the heart rate.
142
Describe the phases of myocardial action potentials.
1. Phase 0: Voltage-gated sodium (Na) channels open causing fast Na influx.
143
2. Phase 1: Na channels close and calcium (Ca) channels open.
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3. Phase 2: Membrane potential plateaus at -15mV for 200 to 300 msec due to the balance between slow Ca influx and K efflux.
145
4. Phase 3: K channels open causing repolarization.
146
5. Phase 4: Resting membrane potential is reached.
147
What is the function of the SA node in the conduction system of the heart?
The SA node initiates the electrical impulse that stimulates atrial contraction.
148
What is the pathway of electrical conduction from the SA node to the ventricles?
The pathway starts from the SA node to the AV node then to the bundle of His which conducts towards the ventricles dividing into right and left bundle branches in the interventricular septum and finally through Purkinje fibers stimulating ventricular contraction.
149
What occurs during Phase 2 of the myocardial action potential?
During Phase 2 the membrane potential plateaus at -15mV for 200 to 300 msec due to a balance between slow influx of Ca 2+ and efflux of K+.
150
What happens during the electrical activity of the heart in Phase 3?
In Phase 3 potassium (K) channels open leading to repolarization of the cardiac muscle cells.
151
What does the Bundle of His do in the conduction system of the heart?
The Bundle of His conducts electrical impulses from the AV node towards the ventricles.
152
Explain the function of Purkinje fibers in the heart's conduction system.
Purkinje fibers stimulate ventricular contraction upward ensuring the effective pumping of blood from the heart.
153
What is the resting membrane potential of myocardial cells?
The resting membrane potential is reached at Phase 4 of the myocardial action potential.
154
In which phase do voltage-gated sodium channels open during myocardial action potentials?
Voltage-gated sodium channels open during Phase 0 of the myocardial action potential.
155
What is the speed of action potentials spreading from the SA node?
Action potentials from the SA node spread rapidly at a speed of 0.8 to 1.0 meters per second.
156
What occurs at the AV node that affects the speed of impulse transmission?
At the AV node the speed of impulses slows down measuring about 0.03 to 0.05 m/sec. This delay accounts for half of the time delay between atrial and ventricular contraction.
157
What is the speed of impulses in the bundle of His and Purkinje fibers?
In the bundle of His the speed of impulses picks up and reaches up to 5 msec in the Purkinje fibers.
158
How long after atrial contraction do the ventricles contract?
The ventricles contract 0.1 - 0.2 seconds after the atria.
159
What is the significance of the refractory periods in cardiac cells?
Refractory periods are significant because they prevent the atria and ventricles from sustaining a contraction ensuring they contract as single units and allowing time for the heart to fill with blood.
160
Why do cardiac cells have long refractory periods?
Cardiac cells have long refractory periods due to the prolonged action potential duration which prevents immediate re-excitation and therefore sustains coordinated contractions.
161
What are arrhythmias?
Arrhythmias are abnormal patterns of electrical activity in the heart that result in irregularities of the heartbeat.
162
What is the relationship between myocardial action potentials and myocardial contraction?
The correlation of myocardial action potentials with myocardial contraction shows that action potentials lead to muscular contractions but the long-lasting action potentials also result in long refractory periods.
163
What are the types of blood vessels?
The types of blood vessels include: A. Arteries B. Arterioles C. Capillaries D. Venules E. Veins.
164
What are the three tunics of blood vessels and their characteristics?
The three tunics of blood vessels are: A. Tunica interna - the inner layer composed of simple squamous endothelium on a basement membrane and elastic fibers. B. Tunica media - the middle layer composed of smooth muscle tissue. C. Tunica externa - the outer layer composed of connective tissue.
165
What is the function of elastic arteries?
Elastic arteries which are closer to the heart allow for stretching as blood is pumped into them and recoil when the ventricles relax.
166
What are muscular arteries and where are they located?
Muscular arteries are located farther from the heart and have more smooth muscle in proportion to their diameter compared to elastic arteries.
167
What roles do arterioles play in the cardiovascular system?
Arterioles which are 20 to 30 micrometers in diameter provide the greatest resistance to blood flow and control blood flow through the capillaries through processes of vasoconstriction and vasodilation.
168
What is an aneurysm?
An aneurysm is a balloon-like swelling in an artery or in a weakened ventricular wall and it most commonly occurs in the aorta.
169
Describe the structural composition of the tunica interna of blood vessels.
The tunica interna is composed of simple squamous endothelium that rests on a basement membrane and includes elastic fibers.
170
What is the significance of smooth muscle in the tunica media?
The smooth muscle in the tunica media is significant as it allows for the regulation of blood vessel diameter influencing blood flow and blood pressure.
171
How do arterioles regulate blood flow to capillaries?
Arterioles regulate blood flow to capillaries through vasoconstriction which narrows the vessel and increases resistance and vasodilation which widens the vessel and decreases resistance.
172
Where do aneurysms most commonly occur and why is this important?
Aneurysms most commonly occur in the aorta which is important because this can lead to severe complications such as rupture causing life-threatening internal bleeding.
173
What are the two types of aortic aneurysms mentioned in the text?
The two types of aortic aneurysms mentioned are thoracic aortic aneurysm and abdominal aortic aneurysm.
174
Where else can aneurysms occur besides the aorta?
Aneurysms can also occur in cerebral and other arteries.
175
What is the diameter range of capillaries?
Capillaries have a diameter of 7 to 10 micrometers (µm).
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What type of tissue composes the wall of capillaries?
The wall of capillaries is composed of a single layer of simple squamous epithelium tissue.
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What is the primary function of capillaries?
The primary function of capillaries is to facilitate the exchange of gases and nutrients between the blood and tissues.
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How is blood flow to capillaries regulated?
Blood flow to capillaries is regulated by vasoconstriction and vasodilation of arterioles and by precapillary sphincters.
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What are the three types of capillaries mentioned?
The three types of capillaries are continuous capillaries fenestrated capillaries and discontinuous capillaries.
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Where are continuous capillaries found and what is their feature?
Continuous capillaries are found in muscles adipose tissue and the central nervous system and adjacent cells are close together contributing to the blood-brain barrier due to the absence of channels.
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What is the unique feature of fenestrated capillaries and where are they located?
Fenestrated capillaries have pores in their vessel wall and are found in the kidneys intestines and endocrine glands.
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What is a characteristic of discontinuous capillaries and where can they be found?
Discontinuous capillaries have gaps between cells that allow the passage of proteins and they are found in the bone marrow liver and spleen.
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What is the significance of veins in terms of blood volume?
Veins contain most of the total blood volume in the circulatory system.
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What is the average pressure in veins compared to arterial pressure?
Veins have a lower pressure of about 2 mmHg compared to an average arterial pressure of 100 mmHg.
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What are the structural differences between veins and arteries?
Veins have thinner walls than arteries and a larger lumen. When cut veins tend to collapse.
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What role do skeletal muscle pumps play in venous blood return?
Skeletal muscle pumps which involve the muscles surrounding the veins help pump blood back to the heart by squeezing the veins.
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How do venous valves function?
Venous valves ensure one-directional flow of blood preventing backflow and promoting efficient return to the heart.
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What are varicose veins and what causes them?
Varicose veins are enlarged surface veins usually in the lower limbs that occur due to venous congestion causing the veins to stretch and the venous valves to malfunction. Risk factors include genetic susceptibility occupations with prolonged standing obesity age and pregnancy.
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What treatments can help reduce venous congestion related to varicose veins?
Walking wearing compression stockings and elevating the legs can reduce venous congestion.
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What surgical treatments are available for varicose veins?
Surgical treatments for varicose veins include laser therapy ligation and stripping.
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What is atherosclerosis?
Atherosclerosis is the most common form of arteriosclerosis characterized by the hardening of the arteries due to plaque buildup.
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How does atherosclerosis contribute to heart disease?
Atherosclerosis contributes to 31% of deaths due to heart attack and stroke by causing plaques that protrude into the lumen and reduce blood flow.
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What are the possible consequences of the plaques formed in atherosclerosis?
Plaques can reduce blood flow which can lead to ischemia heart attacks and strokes.
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What is Atherosclerosis?
Atherosclerosis is a condition characterized by the buildup of plaques in the arterial walls which can lead to blocked arteries and result in serious cardiovascular diseases.
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What factors contribute to the development of Atherosclerosis?
Factors contributing to Atherosclerosis include smoking high blood pressure diabetes and high cholesterol levels.
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What is the role of endothelial damage in Atherosclerosis?
Endothelial damage serves as a trigger for the formation of plaques in a blood vessel leading to Atherosclerosis.
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What are fatty streaks in the context of Atherosclerosis?
Fatty streaks consist of lipid-filled macrophages and lymphocytes that accumulate at the site of endothelial damage within the tunica interna.
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What are fibrous plaques in Atherosclerosis?
Fibrous plaques are formed when layers of smooth muscle and macrophages are deposited followed by a connective tissue cap that encapsulates these components forming a protective layer over the damaged tissue.
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What is the relationship between thrombus formation and Atherosclerosis?
Thrombus formation can occur at sites of Atherosclerosis due to plaque rupture which leads to blood clot formation and can obstruct blood flow.
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What is the tunica interna and what role does it play in Atherosclerosis?
The tunica interna is the innermost layer of a blood vessel. It plays a critical role in Atherosclerosis as it is where endothelial damage occurs and where lipid accumulation begins.
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How do macrophages contribute to Atherosclerosis development?
Macrophages accumulate at sites of endothelial damage as they ingest lipids eventually contributing to fatty streak formation and the overall process of plaque development.
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List four major risk factors that can cause endothelial damage leading to Atherosclerosis.
1. Smoking 2. High blood pressure 3. Diabetes 4. High cholesterol levels.
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What happens to the smooth muscle during the progression of Atherosclerosis?
As Atherosclerosis progresses layers of smooth muscle cells proliferate and contribute to the formation of plaques increasing arterial wall thickness.
