Cardiovascular System Flashcards
Heart
- primarily composed of cardiac muscle
- right side of heart accepts deoxygenated blood returning from the body and moves it to the lungs via the pulmonary arteries (pulmonary circulation)
- left side of heart receives oxygenated blood from the lungs via the pulmonary veins and pumps it out to the body through the aorta (systemic circulation)
Atria
thin-walled structures where blood is received from either the venae cavae (deoxygenated blood entering the the right heart) or the pulmonary veins (oxygenated blood entering the left heart)
Ventricles
- receive blood from the atria
- after they are filled they contract to send blood to the lungs and systemic circulation
- far more muscular than the atria
What valves separate the atria and ventricles?
Atrioventricular Valves
Atrioventricular Valves
LAB RAT
Left Atrium = Bicuspid
Right Atrium = Tricuspid
What valves separate the ventricles from the vasculature?
Semilunar Valves
What valve separates the right ventricle from the pulmonary circulation?
Pulmonary Valve (three leaflets)
What valve separates the left ventricle from the aorta?
Aortic Valve (three leaflets)
Which side of the heart is more muscular?
the left heart – because it has to pump blood into systemic circulation
List the pathway of electrical conduction in the heart
- Sinoatrial (SA) Node
- Atrioventricular (AV) Node
- Bundle of His
- Purkinje Fibers
SA Node
- small collection of cells located in the wall
- generates 60-100 beats per minute, even if all innervation to the heart is cut
- does not require neurological input, as neurological input only functions in speeding up and slowing down rate of contraction
- depolarization causes the two atria to contract simultaneously
AV Node
- sits at junction of the atria and ventricles
- signal is delayed here to allow the ventricles to fill completely before they contract
Intercalated Discs
- connect muscle cells in the ventricles
- contain many gap junctions directly connecting the cytoplasm if adjacent cells, thereby allowing for coordinated ventricular contraction
The circulatory system is under ____ control
autonomic
What are the effects of sympathetic signals to the heart?
increased heart rate and increased contractility of cardiac muscle
What are the effects of parasympathetic signals to the heart?
slowed down heart rate
What nerve sends parasympathetic signals to the heart?
Vagus Nerve
Systole
-ventricular contraction and closure of the AV valves occurs (ventricular pressure > atrial pressure), and blood is pumped out of the ventricles
Diastole
- heart is relaxed
- semilunar valves are closed (aortic/pulmonary pressure > ventricular pressure), and blood from the atria fills the ventricles
- ventricular pressure continues to increase as blood enters the relaxed ventricle from atrium
- at end of this phase SA Node discharges and atria depolarize, leading to contraction of atria thus increasing atrial pressure which forces a small push of blood volume into ventricle (“Atrial Kick”)
Contraction of the ventricles generates a ____ pressure during systole, whereas their relaxation during diastole causes the pressure to ____.
- higher
- decrease
What allows the vessels to maintain sufficient pressure while the ventricular muscles are relaxed?
the elasticity of the walls of the large arteries
Cardiac Output
- the total blood volume pumped by a ventricle in a minute (volume of blood pumping through each ventricle is the same)
- about 5 liters per minute
- CO = HR x SV
HR
- heart rate
- beats / minute
SV
- stroke volume
- volume of blood pumper per beat
“Lub”
- first heart sound
- closure of AV valves
- occurs at beginning of systole (ventricles beginning to contract, pressures above atrial pressure, blood wants to flow back into atria but valves prevent this)
“Dub”
- second heart sound
- closure of SL valves
- occurs at beginning of diastole
What causes valves in the heart to open and close?
pressure differences
What type of cells line all blood vessels?
Endothelial Cells – help maintain the vessel by releasing chemicals that aid in vasodilation and vasoconstriction, also allow white blood cells to pass through the vessel wall and into the tissues during an inflammatory response
Arteries
- Arteries carry blood Away from the heart*
- most arteries contain oxygenated blood, but pulmonary arteries and umbilical arteries contain deoxygenated blood
- highly muscular and elastic, creating tremendous resistance to the flow of blood
- elastic recoil from their walls maintains a high pressure and forces blood forward
- composed of connective tissue, endothelium and smooth muscle
Arterioles
- arteries branch into these
- high resistance
- strong contractile capability
- determine how fast blood can move through circuit
- composed of endothelium and smooth muscle
Capillaries
- have a single endothelial cell layer
- RBCs must pass through these in a single-file
- gases (CO2, O2), nutrients (glucose), and wastes (ammonia, urea) easily diffuse through the walls
- perfuse tissues
Venules
smaller venous structures that connect capillaries to the larger veins of the body
Veins
- thin-walled, inelastic vessels that transport blood to the heart
- except for the pulmonary and umbilical veins, all veins carry deoxygenated blood
- very small amount of smooth muscle so have less recoil than arteries
- have valves that push blood forward and prevent back-flow
- composed of connective tissue, smooth muscle, and epithelium
Where is 3/4ths of our total blood volume at any one time?
veins
Superior Vena Cava
returns blood to the right atria from the portions of the body above the heart
Inferior Vena Cava
returns blood to the right atria from the portions of the body below the heart
End-Diastolic Volume (EDV)
amount of blood in ventricle at the end of ventricular diastole
End-Systolic Volume (ESV)
amount of blood remaining in ventricle after ejection into aorta and pulmonary arteries during systole
P Wave
occurs during end of diastole when SA Node discharges and atria depolarize
QRS Wave
occurs during start of systole when the wave of depolarization from the AV Node passes into and throughout ventricular tissue
T Wave
occurs during early diastole and is ventricular repolarization
Dicrotic Notch
occurs during diastole after the aortic valve has closed, and the combination of elastic recoil of the aorta and blood rebounding against the valve causes this rebound of aortic pressure
What are the 3 portal systems in the body where blood may pass before returning to the heart?
- Hepatic (blood leaving capillary beds in walls of gut pass through the hepatic vein before reaching capillary beds in the liver)
- Hypophyseal (blood leaving capillary beds in hypothalamus travel to a capillary bed in the anterior pituitary)
- Renal (blood leaving the glomerulus travels through an efferent arteriole before going to the vasa recta)
By volume, blood is __% liquid and __% cells
55% liquid and 45% cells
Plasma
- liquid portion of blood
- aqueous mixture of nutrients, salts, respiratory gases, hormones, and blood proteins
What 3 things constitute the cellular portion of blood?
- erythrocytes
- leukocytes
- platelets
What cell are all blood cells formed from?
Hematopoietic Stem Cells (originate in bone marrow)
Erythrocytes
- red blood cell
- specialized cell designed for oxygen transport
- contain hemoglobin, which can bind four molecules of oxygen at once
- biconcave (indented on both sides) which assists them in traveling through capillaries and increases the cell’s surface area for greater gas exchange
- when they mature they lose their mitochondria, nuclei, and other membrane bound organelles
- rely on glycolysis for ATP because they are anaerobes
- lack nuclei so are unable to divide
- lifespan of 120 days in the bloodstream before cells in the liver and spleen phagocytize them
Hematocrit
measurement of how much of the blood sample consists of red blood cells, given as a percentage
Leukocytes
- white blood cells
- compromise less than 1% of total blood volume
- crucial part of immune response – act as defenders against pathogens, foreign cells, cancer and other materials not recognized
- 5 basic types that are organized into 2 classes: granulocytes and agranulocytes
What are the 3 portal systems in the body where blood may pass before returning to the heart?
- Hepatic (blood leaving capillary beds in walls of gut pass through the hepatic vein before reaching capillary beds in the liver)
- Hypophyseal (blood leaving capillary beds in hypothalamus travel to a capillary bed in the anterior pituitary)
- Renal (blood leaving the glomerulus travels through an efferent arteriole before going to the vasa recta)
By volume, blood is __% liquid and __% cells
55% liquid and 45% cells
Plasma
- liquid portion of blood
- aqueous mixture of nutrients, salts, respiratory gases, hormones, and blood proteins
What 3 things constitute the cellular portion of blood?
- erythrocytes
- leukocytes
- platelets
What cell are all blood cells formed from?
Hematopoietic Stem Cells (originate in bone marrow)
Erythrocytes
- red blood cell
- specialized cell designed for oxygen transport
- contain hemoglobin, which can bind four molecules of oxygen at once
- biconcave (indented on both sides) which assists them in traveling through capillaries and increases the cell’s surface area for greater gas exchange
- when they mature they lose their mitochondria, nuclei, and other membrane bound organelles
- rely on glycolysis for ATP because they are anaerobes
- lack nuclei so are unable to divide
- lifespan of 120 days in the bloodstream before cells in the liver and spleen phagocytize them
Hematocrit
measurement of how much of the blood sample consists of red blood cells, given as a percentage
Leukocytes
- white blood cells
- compromise less than 1% of total blood volume
- crucial part of immune response – act as defenders against pathogens, foreign cells, cancer and other materials not recognized
- 5 basic types that are organized into 2 classes: granulocytes and agranulocytes
What are the five basic types of leukocytes?
Granulocytes -Neutrophils -Eosinophils -Basophils Agranulocytes -Lymphocytes -Monocytes
Granulocytes
- includes: Neutrophils, Eosinophils, Basophils
- contain cytoplasmic granules that contain compounds that are toxic to invading microbes and can be released through exocytosis
- involved in inflammatory reactions, allergies, pus formation, and destruction of bacteria and parasites
Agranulocytes
- includes: Lymphocytes, Monocytes
- do not contain granules that are released by exocytosis
Lymphocytes
- important in specific immune response (body’s targeted fight against pathogens like viruses and bacteria)
- some act as primary responders against infection while others function to maintain a long-term memory bank of pathogen recognition
- mature in: bone marrow (B-cells), thymus (T-cells)
- B-cells are responsible for antibody generation
- T-cells kill virally infected cells and activate other immune cells
Monocytes
- phagocytize foreign matter like bacteria
- renamed as macrophages once they leave the bloodstream and enter an organ
- called microglia in the nervous system
- called langerhans cells in the skin
- called osteoclasts in bone
Thrombocytes (Platelets)
- cell fragments or shards that are released from cells in bone marrow known as megakaryoctes
- function in assisting in blood clotting and are present in high concentrations
Hematopoiesis
- the production of blood cells and platelets
- triggered by many hormones including growth factors and cytokines
Erythropoietin
- hormone involved in hematopoiesis
- secreted by the kidney and stimulates mainly RBC development
Thrombopoietin
- hormone involved in hematopoiesis
- secreted by the liver and kidney
- stimulates mainly platelet development
Antigens
- surface proteins expressed on red blood cells
- any specific target (usually a protein) to which the immune system can react
- are the stimuli for B-cells to make antibodies; after exposure of a B-cell to its specific antigen, the cell becomes an antibody-producing factory
What are the two major antigen families relevant for blood groups?
ABO Antigens and Rh Factor
ABO Antigens
- comprised of three alleles for blood type
- erythrocyte cell-surface proteins
- A and B are co-dominant, and O is recessive
Blood Type A
- Genotypes:
- Antigens Produced:
- Antibodies Produced:
- Can Donate to…
- Can Receive from…
- I^A I^A, I^A i
- A
- anti-B
- A, AB
- A, O
Blood Type B
- Genotypes:
- Antigens Produced:
- Antibodies Produced:
- Can Donate to…
- Can Receive from…
- I^B I^B, I^B i
- B
- anti-A
- B, AB
- B, O
Blood Type AB
- Genotypes:
- Antigens Produced:
- Antibodies Produced:
- Can Donate to…
- Can Receive from…
- I^A I^B
- A and B
- none
- AB only
- A, B, AB, O
Blood Type O
- Genotypes:
- Antigens Produced:
- Antibodies Produced:
- Can Donate to…
- Can Receive from…
- ii
- none
- anti-A and anti-B
- A, B, AB, O
- O only
Which blood type is considered universal donors?
Type O negative – this is because regardless of the recipients actual blood type, type O blood cells will not initiate any immune response since they do not express either antigen variants
Which blood type is considered universal recipients?
Type AB positive – this is because no blood antigen is foreign to AB individuals so no adverse reactions will occur upon transfusion
Rh Factor
- surface protein expressed on red blood cells
- Rh+ or Rh- refers to the presence or absence of a specific allele called D; it an also be indicated with a plus or minus subscript on the ABO blood type
- Rh+ follows autosomal dominant inheritance – one positive allele is enough for it to be expressed
- particularly important in maternal-fetal medicine
What happens when a mother is Rh- and her fetus is Rh+?
the mother will become sensitized to the Rh factor and her immune system will begin making antibodies against it; this is not a problem for the first child because it is usually born by the time the mother makes antibodies against it but if her second fetus is Rh+ then maternal anti-Rh antibodies can cross the placenta and attack the fetal blood cells (called erythroblastosis fetalis)
Why is there less concern with ABO mismatching between mother and fetus?
because maternal antibodies are of a class called IgM which does not readily cross the placenta (unlike anti-Rh IgG antibodies which can)
Blood Pressure
- measure of the force per unit area exerted on the wall of the blood vessels
- expressed as a ratio of the systolic (ventricular contraction) to diastolic (ventricular relaxation) pressures
Where does the largest drop in blood pressure occur?
across the arterioles – this is necessary because the capillaries are thin-walled and unable to withstand the pressure of the arterial side of the vasculature
Equation for pressure difference across the circulation (ΔP)
ΔP = CO x TPR
where CO is cardiac output and TPR is teh total peripheral (vascular) resistance
___ and ___ act much like resistors in a circuit
arterioles and capillaries
What are the 3 factors resistance is based on?
- resistivity
- length
- cross-sectional area
The ___ a blood vessel is, the more resistance it offers
longer
The ___ the cross-sectional area a blood vessel has, the less resistance it offers
larger
With the exception of the portal systems, all systemic capillary beds are in ___ with each other
parallel – this means that opening capillary beds will decrease vascular resistance and increase cardiac output
Baroreceptors
- specialized neurons that detect changes in the mechanical forces on the walls of the vessel
- regulate blood pressure
What happens when BP is low?
baroreceptors stimulate the sympathetic NS which causes vasoconstriction which increases BP
What happens when blood osmolarity is too high (dehydration)?
chemoreceptors sense this and promote the release of ADH (peptide hormone made in hypothalamus but stored in posterior pituitary) which increases the reabsorption of water, thereby increasing blood volume and pressure (while diluting the blood)
What happens when there is low perfusion to the juxtaglomerular cells of the kidney (low BP)?
juxtaglomerular cells of the kidney stimulate aldosterone release from the renin-angiotensin-aldosterone system; aldosterone increases the reabsorption of sodium (and water too) thereby increasing blood volume and pressure
What happens if BP is too high?
- sympathetic impulses could decrease, permitting relaxation of the vasculature with a concurrent drop in BP
- in the heart, specialized cells in the atria secrete hormone Atrial Natriuretic Peptide (ANP) which aids in the loss of salt within the nephron (acting as a natural diuretic)
What allows for exchange of gases, waste, and nutrients between capillaries and tissues?
concentration gradients
Hemoglobin
- oxygen’s primary carrier in blood
- protein composed of 4 cooperative subunits, each of which has a prosthetic heme group that binds to an oxygen molecule which occurs at the heme group’s central iron atom
- binding or releasing of oxygen to or from the iron atom is a redox reaction
Oxygen Saturation
- the percentage of hemoglobin molecules carrying oxygen
- can be measured using a finger probe
- most people have a saturation above 97%
Carbon Dioxide
- primary waste product of cellular respiration that must be removed
- non-polar and has a low solubility in the aqueous plasma (unlike oxygen)
- can be carried by hemoglobin bit hemoglobin has a much smaller affinity for it
- vast majority of CO2 in the blood exists as bicarbonate (HCO3-)
- increased CO2 production causes a rightward shift in bicarbonate buffer equation, resulting in decreased pH (increased [H+])
What cause a rightward shift in the oxyhemoglobin dissociation curve?
- Rightward shift means greater O2 unloading at tissues*
- exercise
- increased temperature
- increased 2,3-bisphosphoglycerate (side product of glycolysis in RBCs)
- increased partial pressure of CO2
- increased [H+] (decreased pH)
What causes a leftward shift in the oxyhemoglobin dissociation curve?
- Leftward shift means less O2 unloading at tissues*
- decreased partial pressure of CO2
- decreased [H+] (increased pH)
- decreased temperature
- decreased 2,3-bisphosphoglycerate
Fetal Hemoglobin
- has a higher affinity for oxygen compared to adult hemoglobin
- exhibits a left-shifted curve
What two pressure gradients in the blood stream are essential for maintaining proper balance of fluid volume and solute concentrations between the blood and interstitium (cells surround blood vessels)?
hydrostatic and osmotic (oncotic) pressures (known as the Starling Forces)
Hydrostatic Pressure
- force per unit area that the blood exerts against the vessel walls
- generated by the contraction of the heart and the elasticity of the arteries
- pushes fluid out of the blood stream and into the interstitium through the capillary walls
Osmotic (Oncotic) Pressure
- the “sucking” pressure generated by solutes as they attempt to draw water into the bloodstream [pulls fluid back into the vessels]
- most of this pressure is attributable to plasma proteins
Describe the Hydrostatic and Osmotic Pressures at a Capillary Bed (from both the arteriole end and the venule end)
- at the arteriole of the capillary bed, hydrostatic pressure is much larger than oncotic pressure and there is a net efflux of water from the circulation
- as fluid moves out of the vessels, the hydrostatic pressure drops but the osmotic pressure remains the same
- at the venule of the capillary bed, hydrostatic pressure has dropped below osmotic pressure and there is a net influx of water back into circulation
Edema
accumulation of excess fluid in the interstitium
Clots
- composed of both coagulation factors (proteins) and platelets
- prevent/minimize blood loss
What starts the coagulation cascade?
exposure of platelets to the protein called tissue factor that is located on connective tissue, which leads to platelets releasing their contents and clumping together
What leads to stabilization of the clot?
activation of prothrombin to form thrombin by thromboplastin; thrombin then converts fibrinogen into fibrin which forms small fibers that aggregate and cross-link into a woven structure that captures RBCs and other platelets, forming a stable clot
What breaks down a clot?
Plasmin – generated from plasminogen
