HTHS Mod 16

  1. Describe the position of the heart in the thoracic cavity
    • Located in the mediastinum
    • lies medially btwn lungs
    • about 2/3's of heart lies left of midline, about nipple level
    • Apex of the heart is inferior and rests on diaphragm
    • Base of heart is superior to apex
  2. mediastinum
    • the thoracic cavity MINUS pleural cavity (lungs & associated structures)
    • extends from the sternum anteriorly to the vertebral columns posteriorly
    • includes the esophagus, thymus, great vessels of heart and the heart
  3. pericardium
    • a membrane (slippery bag) which covers and protects the heart
    • keeps heart in place in mediastinum
    • gives enough freedom to contract
    • consists of two parts: serous pericardium and fibrous pericardium
    • *think of the example of imagining yourself ramming a fist into a balloon.
  4. TEE
    • transesophageal echocardiography
    • an ultrasound (sound wave pics) of heart
    • done by placing a transducer in the esophagus, which lets docs get a pic of heart that is unobstructed by tissues
  5. viscera refers to
    • the organs
    • *remember the layer of the serous membrane that lines the organ itself will be the visceral layer
  6. Layers of heart wall... from deepest to outermost layer
    • three layers=
    • deepest: endocardium
    • middle: myocardium
    • outermost: epicardium
  7. endocardium
    • the deepest layer of the heart wall
    • consists of a thin layer of simple squamous epithelium over a thin layer of connective tissue
    • provides a smooth surface for blood as it flows through the cambers and valves of heart
    • most important to prevent friction that may cause blood clots to form
    • *Can develop chronic infections
  8. myocardium
    • the thick middle layer
    • is the muscular wall of heart
    • makes up 95% of heart and is responsible for pumping action
  9. epicardium
    • the thin, outermost layer of heart
    • a delicate membrane of epithelial and connective tissue giving the heart a slippery covering
    • is also called visceral layer of pericardial covering
  10. endocarditis
    • chronic infections of the endocardium w microorganisms that can lodge on heart valves or walls of heart
    • Risk factors: heart defects, degeneration of valves, transplanted heart valves and rheumatic fever
    • *dental cleanings can allow small # of bacteria into bloodstream. Therefore, these pts should receive antibiotics prior to dental work
  11. serous pericardium
    • the deeper part of the pericardium
    • has two layers: visceral layer and parietal layer
  12. visceral layer of the serous pericardium
    • is the deeper layer of the serous pericardium
    • covers the heart 
    • is synonymous with the epicardium
    • *In analogy of fist ramming water balloon, this would be the part of the balloon which surrounds your fist
  13. parietal layer of serous pericardium
    • fused with the fibrous pericardium
    • *In analogy with fist ramming water balloon, this would be the part of the balloon not touching your hand (but on outside of balloon, NOT the inside)
  14. fibrous pericardium
    • the outermost part of the pericardium
    • a tough, dense connective tissue that prevents the heart from over expanding
    • anchors the heart to the mediastinum
  15. pericardial fluid
    fills the pericardial cavity btwn the visceral and parietal layers of the serous pericardium
  16. pericardial effusion
    • an accumulation of excess pericardial fluid
    • may occur due to infections, trauma, or myocardial infarction
    • puts pressure on the heart; can become great enough to prevent heart from pumping (cardiac tamponade)
  17. cardiac tamponade
    • life-threatening condition in which excess pericardial fluid or leaking blood prevents the heart from pumping blood
    • *Think of needing to insert a tampon into the pericardial space to soak up the extra fluid
  18. histologic features of myocardium
    • myocardium = heart muscle
    • ~intercalated discs for structural strength
    • ~gap junctions to synchronize muscle cell contraction
    • ~plentiful mitochondria for energy
    • ~branched fibers
    • ~centrally-placed nucleus
  19. cardiac muscle vs skeletal muscle
    • Cardiac & skeletal are both striated
    • Unlike skeletal, cardiac fibers are shorter, branch, and have one centrally-located nucleus
  20. intercalated discs
    • in heart muscle
    • are transverse thickenings of sarcolemma (cell membrane), which connect neighboring fibers together
  21. desmosomes
    • are the "spot welds"
    • are contained in discs of heart muscle
    • they hold fibers together n keep the heart cells from pulling apart
  22. gap junctions in heart muscle
    • allow communication & muscle action potentials to travel btwn fibers
    • synchronize muscle cell contraction
  23. 4 chambers of heart
    • R & L Atria are superior and are holding chambers and reservoirs for blood
    • R & L Ventricles are inferior portion and pump blood to lungs & body
  24. 2 Atruim
    • Right atrium - chamber which receives deoxygenated blood from body
    • Left atrium - chamber which receives oxygenated blood from lungs
    • have thin walls, little muscle tone
  25. 2 ventricles
    • Right ventricle - receives blood from right atrium, it pumps the deoxygenated blood out to the lungs
    • Left ventricle - receives oxygenated blood from left atrium, it pumps oxygenated blood out to body
  26. 4 valves of heart
    • 2 atrioventricular valves (AV) = tricuspid and bicuspid valve
    • 2 semilunar (outflow) valves
    • Don't actively open; operate by pressure
    • when enough pressure builds up behind a valve, it forces valve open.
    • Prevent backflow
  27. Atrioventricular valves
    • valves that control the flow of blood btwn atria and ventricles:
    • Tricuspid valve - (right atrioventricular valve) btwn right atria and right ventricle
    • Bicuspid valve - (mitral valve or left AV) btan left atria and left ventricle
  28. Semilunar valves
    • Are the outflow valves which control the flow of blood leaving the heart from the ventricles:
    • Pulmonary semilunar valve: regulates blood flow from the right ventricle to pulmonary trunk (to lungs)
    • Aortic semilunar valve: regulates blood flow from the left ventricle to the aorta (to body)
  29. names for tricuspid valve
    Right AV valve
  30. names for pulmonary valve
    • pulmonary semilunar valve
    • also known as an outflow valve
  31. names for bicuspid valve
    • Left AV
    • mitral valve - (recall mitral comes from it looking like a bishops hat... like a pope)
  32. names for aortic valve
    aortic semilunar valve
  33. atrial "kick"
    • the small pumping action of atria
    • Drainage of blood from atria to ventricles, drains by gravity
    • when atria contract, they force remaining blood out (like ketchup bottle)
  34. pulmonary trunk
    • divides into R and L arteries
    • Called arteries cause they leave the heart, BUT they carry deoxygenated blood from the right ventricle
    • These are the ONLY arteries that carry deoxygenated blood
  35. pulmonary veins
    • veins which carry oxygenated blood from lungs to left atrium 
    • *only veins which carry oxygenated blood
  36. Aorta
    • Duh - largest artery in body
    • leaves left ventricle
    • Ascending aorta arches to the left; forming aortic arch. Descends to thoracic aorta and abdominal aorta
  37. Chordae tendinae
    • cordlike tendons that are anchored to papillary muscles
    • help keep valves in place
  38. operation of valves of heart
    • valves operate in pairs:
    • AV valves open together: tricuspid, bicuspid (mitral)
    • Outflow valves open together: pulmonary, aortic
    • Therefore:
    • As blood is ejected from the atria, both AV valves open and SL valves close
    • As blood is ejected from ventricles, both SL valves are open and AV valves are closed
  39. Valvular stenosis
    • occurs when the valves are narrowed from being too stiff or from not opening properly;leave blood behind
    • *causes chamber behind valve to work harder as there is extra blood to pump
    • **Stiff & Stenosis
  40. valvular incompetence
    • occurs when valves are too "floppy" and leak
    • leads to valvular regurgitation
    • **Incompetent man has "floppy" penis
  41. valvular regurgitation
    • term for "leaky" valves
    • occurs if valves are incompetent & blood flow leaks back into the chamber behind the valve
    • *causes chamber behind valve to work harder as there is extra blood to pump
  42. Mitral valve prolapse
    • most common valvular heart disease
    • the mitral valve become misaligned - falls out of place
    • often genetically inherited and more common in women
  43. mitral regurgitation
    • happens when the left ventricle can't pump blood sufficiently and becomes dilated (stretched out)
    • occurs when mitral valve becomes leaky from muscle damage of left ventricle, usually due to myocardial infarction or hypoxia (lack of oxygen)
  44. vegetations
    • bacterial growth
    • can happen on heart valves when there's an infection
    • the valves don't work properly, bits of vegetation may break free and become emboli
  45. autorhythmic cell
    • cells which can fire action potential w/o nervous stimulation (no outside stimulation or control)
    • never rests so it doesn't have resting membrane potential ~ cause of funny channels
  46. Parts of the conduction system of the heart
    • 1 ~ SA Node
    • 2 ~ AV node
    • 3 ~ AV bundle
    • 4 ~ R & L bundle branches
    • 5 ~ purkinje fibers
  47. What happens with the action potential that is generated by autorhythmic cells?
    It travels through the conduction system of the heart and then spreads to the contractile cells of the atria and ventricles
  48. cardiomyocytes
    • a cluster of specialized heart muscle cells at base of heart 
    • used to set rhythm of heart
    • referred to as the heart's pacemaker
    • have autorhythmicity
    • found in SA node
    • comprised of only 1% of heart cells
  49. SA node
    • sinoatrial node ~ contraction impulse begins here
    • called pacemaker
    • fibers (made up of cardiomyocytes) here fire the fastest; about 100x min
    • Are considered primary pacemakers
    • located in superior right atrium,also by coronary sinus
    • Action potential generated at SA node travels through gap junctions through both atria which then contract
    • **to remember "sino-atrial", think of En"sino" man....
  50. coronary sinus
    little depression in right atrium where blood is coming back into the right atrium from the coronary circulation (blood circulation of the heart muscle)
  51. AV node
    • Atrioventricular node
    • Where the action potential travels to when it leaves the SA node; it's collected here
    • located near junction of left atrium and right ventricle
    • These fibers only act as pacemaker if SA node cells are dead ~ are slower than SA node
  52. ectopic pacemaker
    • Refers to the fibers in the AV node
    • they could act as pacemaker ONLY if SA node cells are dead
    • but act much slower. So heart rate would be slower
  53. bundle of His
    • AV bundle (atrioventricular bundle)
    • Where action potential travels when it leaves AV node
    • only place action potential can communicate btwn the atria and ventricles
    • branches shortly after it begins into R and L bundle branches
    • bundle of conductive muscle cells which leads from AV node through interventricular septum
  54. Right and Left bundle branches
    • after action potential leaves AV bundle, travels down these branches
    • branches run down to interventricular septum to apex of heart
  55. Purkinje fibers
    • where the action potential goes after R & L bundle branches
    • fibers which run upward through the ventricles, conducting the action potential
    • reaches cells in ventricles, then ventricles contract
  56. Three ions involved with action potential of a cardiac autorhythmic cell
    • Na+ ~ with funny channels
    • Ca++ ~ after threshold is reached, making membrane more and more positive

    K+ ~ like neuron, channels open for 2nd half of action potential for repolarization
  57. Funny channels
    • a special kind of Na+ channel only found in autorhythmic cells
    • opening causes the membrane of autorhythmic cell to slowly drift back to threshold after an action potential ~ therefore, it has NO RESTING POTENTIAL!!
    • These channels open when cell becomes more neg after action potential
    • At the same time, K+ channels close decreasing outflow of K+
  58. Recall charges on inside vs. outside of cell
    • Inside is more negative that outside
    • Helps to draw Na+ and Ca++ into cell
  59. steps in autorhythmicity
    • 1. Na+ funny channels open causing membrane to "drift" towards threshold
    • 2. After threshold is hit, Ca++ channels open causing depolarization of cell membrane
    • 3. K+ channels open causing repolarization of cell membrane
    • *Again, these cells never go back down to a flat line of resting. Once it is repolarized, the funny channels open again, and begin drifting back to threshold leading to action potential
  60. What would happen if there was an excess of K+ outside of cell?
    • Would lower the K+ being pulled out of the cell by concentration gradient. The negative charge inside cell would equal pull out. No K+ movement eventually will stop all action potentials
    • Can cause a decrease in heart rate and contractility
    • What they use when someone is put to death by lethal injection.
    • The heart just stops
  61. What is the issue with old blood - the reason blood bags used for transfusion are dated with expiration date?
    • If blood sits for too long, RBC die and release intracellular K+
    • This is dangerous as it can cause K+ overload
    • *Recall that RBC only live 120 days. When blood is taken, there are RBC that are close to death. Can't sit for too long.
  62. What happens with increase of Na+ in the blood
    • Na+ blocks Ca++ from entering the cells, stopping the action potential
    • this slows down the heart & stops action potential
  63. What happens with a moderate increase in Ca++
    will speed up and strengthen the heart
  64. Explain the nervous control of the heart
    • *Recall that the heart does not need nervous stimulation to beat
    • The autonomic nervous system can speed up or slow down the rate of heart and controls the strength of contractions. 
    • Recall the effects of the sympathetic nervous system and the parasympathetic nervous system.
  65. cardiovascular center
    is a cluster of cells in the medulla that responds to input from baroreceptors by increasing or decreasing outflow via sympathetic and parasympathetic nervous systems
  66. carotid arteries
    • those arteries that branch off from the aorta
    • have baroreceptors in sinus
  67. baroreceptors
    receptors in the sinus of the carotid artery which sense blood pressure
  68. What cranial nerves are involved with innervation of the heart?
    • CN 9 ~ glossopharyngeal nerve - is afferent (sensory) from baroreceptors in carotid sinus
    • CN 10 ~ Vagus nerve - is both afferent and efferent. 
    • >>is afferent from baroreceptors in arch of aorta to medulla
    • >>is efferent from medulla to SA node & AV node
  69. What happens if the baroreceptors sense that blood pressure is too high?
    • The parasympathetic nervous system responds to slow down the heart through the CN X (Vagus nerve)
    • Signal travels out of medulla on efferent Vagus nerve to the SA node & AV node
  70. What happens if the baroreceptors sense the blood pressure is too low?
    • The sympathetic nervous system responds to speed up the rate of the heart through *sympathetic cardio accelerator spinal nerves
    • These *efferent nerves leave medulla, travel through spinal cord, then synapse in a sympathetic trunk ganglion (the chain ganglion that line spinal cord)
    • From there it can go to SA node, AV node and into the ventricular area
    • Results in turning up the pacemaker
  71. Where does all the input for the cardiovascular center come from... what areas?
    • From higher brain centers: cerebral cortex, limbic system, and hypothalamus (can involve emotional responses that stimulate heart)
    • From sensory receptors: Proprioceptors (monitor movements), Chemoreceptors (monitor blood chemistry), Baroreceptors (monitor blood pressure)
  72. Summarize output info to heart
    • Cardio accelerator nerves (sympathetic) speeding heart up
    • Vagus nerves (CN 10 - parasympathetic) slowing it down
  73. How does heart respond to sympathetic NS
    • recall sympathetic responds to norepinephrine and epinephrine release
    • Increases heart rate and stroke volume
    • > β1 - adrenergic receptors & β2 - adrenergic receptors
  74. How does heart respond to parasympathetic NS
    • In the heart, parasympathetic responds to ACh release
    • decreases heart rate
    • involves muscarinic (M2) receptors (** think of hallucinogenic mushrooms - u get relaxed)
    • *recall acetylcholine (ACh) was an excitatory neurotransmitter in skeletal muscle. Here, it's parasympathetic. WHETHER IT'S EXCITATORY OR INHIBITORY depends on the receptor!!
  75. 3 phases of cardiac muscle action potential
    • 1 - depolarization
    • 2 - plateau
    • 3 - repolarization
  76. What is going on in the depolarization of cardiac contractile muscle cells
    • they have resting potential of about -90 mv
    • When action potential is triggered, voltage-gated fast Na+ channels open which quickly lead to depolarization of the cell
  77. Compare/contrast difference in action potentials btwn cardiac muscle and skeletal muscle
    • Cardiac muscle action potentials last about 200x longer than skeletal muscle or nerve action potentials
    • Both depend on voltage-gated Na+ channels for initial depolarization, but cardiac muscle uses voltage-gated slow Ca++ channels to prolong the action potential and therefore muscle contraction
  78. What is going on in the plateau of a cardiac muscle action potential
    • Is a prolonged depolarization phase
    • Voltage-gated slow Ca++ channels in the sarcolemma open
    • Ca++ flows into cytosol, triggering further release of Ca++ from sarcoplasmic reticulum
    • Ca++ ions bind to troponin, allowing actin and myosin to bind, sliding past each other and increasing tension causing contraction (just as in skeletal muscle)
  79. what's going on during repolarization of a cardiac muscle action potential?
    • Voltage-gated K+ channels open causing K+ to rush out of cell, restoring the negative membrane potential
    • Ca++ channels close at the same time leading to repolarization
  80. What's going on during the refractory period of a cardiac muscle action potential
    • Period of time in which a second action potential cannot be triggers
    • longer than in skeletal muscle
    • allows the ventricles to relax while the atria contract, and for ventricles to contract while the atria rest
  81. arrhythmias & treatments
    • is a disorder of the rhythm of heart
    • either bradycardic or tachycardic
    • Drugs used affect either ion channels or neurotransmitter receptors
    • -beta blockers block norepinephrine transmitters or hormones that speed up HR
    • -Calcium channel blockers slow the flow of calcium into and out of cells
    • -Quinidine, lidocaine, and others block sodium channels
  82. EKG
    • also called ECG
    • is a recording of the electrical changes on the surface of the body resulting from the depolarization and repolarization of the myocardium
    • As the electrical wave spreads over the surface of the heart, the charges shift from one place to another
  83. What can an abnormal ECG show?
    • probs within conduction pathways of heart 
    • can show if heart is enlarged, if certain regions of heart are damaged, and cause of chest pain
  84. ECG waves
    • P Wave
    • QRS complex (wave)
    • T wave
    • *Atrial repolarization is hidden behind the large QRS complex
  85. Explain what is happening in each "wave" or segment of an EKG
    • P wave = atrial depolarization
    • P - Q interval = atrial "kick" fills ventricles
    • QRS wave = ventricles depolarize, atria repolarize
    • S - T segment = blood flows out, empting ventricles
    • T wave = ventricular repolarization
  86. What is measured in the P - Q interval?
    • This is the area btwn P and Q, during which atrial "kick" fills ventricles
    • On the ECG, it measures the time it takes for atria to depolarize
    • *The cell must depolarize in order for the muscle to contract
  87. What is measured in the S - T segment?
    Measures the time it takes to empty the ventricles before the repolarize
  88. What is measured during the Q - T interval?
    • Includes the area from the start of QRS complex to end of T wave
    • measures time from ventricular depolarization to end of ventricular repolarization
  89. What is the difference btwn a normal EKG reading compared to increased and max HR
    • As heart rate increases, PQRST get closer
    • at max HR, no space btwn PQRST
  90. Abnormal EKG tracings:
    • consist of missing waves, abnormal wave shape or abnormal time interval btwn waves
    • Examples: A-fib, V-tach, V-fib
  91. A-fib
    • Atrial fibrillation
    • most common acute ECG abnormality
    • Almost normal QRS but missing P
  92. V-tach
    • Ventricular tachycardia
    • ventricle depolarizes, but pumping action not effective
    • can progress to V-fib
  93. V-fib
    • ventricular fibrillation
    • disorganized electrical activity
    • life threatening
  94. Compare Cardiac muscle action potential with EKG
    • QRS is rapid depolarization as ventricular muscle cells open Na+ channels
    • QT interval is the time Ca++ channels are open
    • T is the repolarization from an influx of K+
  95. cardiac cycle
    • includes all the events associated with one heartbeat, including:
    • diastole
    • atrial systole
    • ventricular systole
  96. What happens during diastole in cardiac cycle
    • this is relaxation period ~ time btwn ventricular contraction and atrial contraction
    • At beginning of cycle, the heart is completely relaxed, w blood entering both the left and right atria
  97. What happens during Atrial systole of cardiac cycle
    • systole = contraction
    • As the heartbeat begins, the atria contract
    • this forces blood from the atria into the ventricles
    • atrial "kick"
  98. What happens during the ventricular systole of cardiac cycle
    • systole = contraction
    • Soon after atrial systole, ventricular systole occurs
    • The atria relax during ventricular systole
    • The ventricles remain contracted for a measurable time, and then the entire heart returns to diastole
  99. Name the individual events of the cardiac cycle
    • 1. action potential starts @ SA node, causing depolarization of atrium, producing P wave
    • 2. Atria contract (atrial systole)
    • 3. Action potential pauses at AV node. Then spreads to ventricles causing depolarization (QRS wave)
    • 4. Contraction of ventricles - begins shortly after QRS complex appears and continues during S -T segment
    • 5. Repolarization of ventricles (T wave)
    • 6. Ventricular diastole begins shortly after T wave begins
  100. How long should each of the 3 phases of cardiac cycle take?
    • In a heart rate of 75 bpm:
    • atrial systole: 0.1 sec ~ on EKG, starts in middle of P wave, ends about midway btwn R & S
    • ventricular systole: 0.3 sec ~ on EKG, starts about midway btwn R & S, ends approx. 3/4 through T wave (almost end of plateau)
    • Diastole period: 0.4 sec ~ on EKG, occurs from end of ventricular systole to beginning of atrial systole
  101. What makes the "lup-dup" sound of the heart
    valve closure
  102. What are the two loudest sounds of the heart
    • S1: lower pitched "lub" - is the AV valves closing plus semilunar valves opening. Heard at S (in QRS)
    • S2: higher pitched "dup" - this is the semilunar valves closing plus the AV valves opening. heard at end of T wave
  103. How to figure cardiac output
    • Heart rate x stroke volume output
    • Ex: 72 beats per min x 70 ml per beat = 5L
  104. How to figure max heart rate
    220 minus age of person
  105. EDV
    • End-diastolic volume
    • amount of blood that are in the ventricles after they fill - BEFORE CONTRACTION
    • approx 120 ml
  106. ESV
    • End-systolic volume
    • amount of blood remaining in ventricles after contraction
    • about 50 ml
  107. SV
    • Stroke volume
    • amount of blood pumped out of heart after ventricles contracted
    • SV = EDV - ESV
  108. ejection fraction
    % of blood ejected

    Ejection fraction = Image Upload 1

    *recall stroke volume is EDV - ESV

    • normal is 60%
    • Lower ejection fraction means blood is pooling in heart & may clot. Heart isn't pumping effectively. Ex: congestive heart failure
    • Can lead to fatigue, blueness in extremities,
  109. Frank-Starling mechanism
    • states that the more blood that returns to the heart, the greater the force the heart can pump blood out
    • Ex: when exercising, you need more blood flow. need to have bigger contraction
  110. cardiac output
    • refers to the amount of blood being pumped out each minute
    • CO = SV X HR
    • { cardiac output = volume of blood ejected by ventricle during each contraction x # of heart beats per minute }
  111. structures of a blood vessel
    • lumen
    • tunica interna
    • tunica media
    • tunica externa
  112. tunic
    • layers which make up the vessel walls
    • all blood vessels in body share components of three basic tunics:
    • Tunica interna
    • Tunica media
    • Tunica externa
  113. endothelium
    • consists of a thin layer of squamous epithelium which lines the internal layer of blood vessels
    • endothelial cells are active participants in a variety of vessel-related activities that influence blood clotting, blood flow, and capillary permeability
  114. tunica interna
    • forms the innermost layer of a blood vessel
    • consists of a simple layer of squamous epithelium (endothelium)
    • connected to a basement membrane
    • provides very smooth, almost friction free surface for blood cells to "skate" on
  115. Tunica media
    • middle tunic in blood vessels
    • is a muscular and connective tissue layer that displays the greatest variation among the different tissues
    • responsible for vasoconstriction and vasodilation in arteries to control blood flow and blood pressure
    • much thicker in artery
  116. tunica externa
    • the outer covering, or layer, of blood vessels
    • made up of elastic and collagen fibers (connective tissue)
    • contains numerous sympathetic nerves which control the diameter of the vessel
    • also contains vasa vasorum
  117. vasa vasorum
    tiny blood vessels which are especially present in large vessels like the aorta
  118. Arteries vs. veins
    • Artery: smooth muscle layer is thicker; lumen diameter can change depending on muscle tone
    • Veins: thinner walls, less or absent smooth muscle and elastic tissue layer; lumen diameter doesn't change; have valves to prevent backflow. Operate at much lower pressures than arteries
  119. Different types/sizes of blood vessels
    • Elastic arteries
    • Muscular (distributing) arteries
    • arterioles
    • capillaries
    • venules
  120. elastic arteries
    • Also called conducting arteries
    • large in diameter
    • thin walls
    • able to withstand high pressure
    • Ex: aorta
  121. muscular arteries
    • also called distributing arteries
    • medium in diameter
    • their tunica media contains more smooth muscle, which is also thicker
    • has fewer elastic fibers than elastic arteries
    • these arteries will vasoconstrict/dilate, control blood pressure, shunt blood flow to other places in body
  122. arterioles
    • smallest arteries
    • they deliver blood to capillaries
    • important in adjusting the rate of blood flow into capillaries
    • has sympathetic nerves in tunica externa to regulate muscular layer that regulates resistance
    • also have muscular cufts, or sphincters, to regulate blood flow
  123. Capillaries
    • join arterioles and venules
    • occur as capillary beds of interconnected vessels
    • 3 types: continuous, fenestrated, sinusoids
    • so small RBC's must fold upon themselves to pass through (reversible-deformity) 
    • It's through the walls of the capillaries that the exchange of nutrients, oxygen, and waste products occur
    • Walls consist of single layer of endothelial cells, attached to basement membrane to facilitate easy exchange of gases and nutrients
    • Tissues with higher metabolic needs, like muscle, have more capillaries than tissues w lower metabolic needs, like tendons and ligaments
  124. Continuous capillaries
    • endothelial cells for a continuous tube ("tile floor")
    • interrupted only by small intercellular clefts (precapillary sphincters)
    • passage of substances by pinocytosis
  125. fenestrated capillaries
    • fenestra = "window" in latin
    • are much more porous; acts like strainer
    • holes + basement membrane allows passage of substances
    • found in kidneys, small intestine, and endocrine glands
  126. Sinusoids
    • type of capillaries that have open spaces btwn cells and basement membrane to facilitate easy passage of substances
    • found in liver and spleen
  127. precapillary sphincters
    • collars of smooth muscle that regulate flow of blood through capillary bed
    • kinda like the "on/off" valve; can allow blood to flow through, or can shunt it to another area
    • When closed, blood takes the thoroughfare channel
  128. Processes of capillary exchange of nutrients, gases and wastes:
    • Filtration - delivery to tissues
    • reabsorption - taking the garbage out
  129. filtration
    process by which blood pressure drives fluid and solutes out of blood capillaries into the interstitial fluid & delivers oxygen, glucose, and other nutrients to cells
  130. reabsorption
    • process by which interstitial fluid pressure drives fluid into blood capillaries
    • carbon dioxide, acid, urea, and other wastes are exposed of
  131. Starling forces
    refers to the balance btwn the blood hydrostatic pressure and the interstitial fluid osmotic pressure
  132. Starling's law of the capillary
    • refers to the equation that relates to the "starling forces"
    • explains the pressure/forces that occur at the capillary level - getting the goods to the cells and then taking the garbage out
  133. hydrostatic blood pressure
    • refers to force at capillaries from blood pressure
    • -on the arteriole end of the capillary bed, pressure is high & moves stuff out into the interstitial fluid; force is about 33 mmHg
    • -on the venule end, pressure drops to about 17 mm Hg.
  134. Interstitial fluid osmotic pressure
    • force which comes from plasma proteins that can't cross into interstitial fluid
    • (recall osmosis - water wants to flow to areas of high concentration so it can dilute it to a lower concetnration. Here, it wants to dilute the proteins within the capillaries.)
    • This pressure pretty much stays consistant at both ends of capillary bed @ 25 mmHg
  135. What happens at the arteriole end of the capillary?
    • forces favor filtration:
    • Blood hydrostatic pressure (pushing force from heart) is about 33mm Hg. 
    • Interstitial fluid osmotic pressure ) It opposes blood hydrostatic pressure @ 25 mmHg
    • Subtracting the two pressures (33 - 25) gives us about +8 mmHG pressure favoring filtration
    • Hence, filtration is the winning force
  136. What happens at the venule end of the capillary?
    • Forces favor reabsorption
    • Blood hydrostatic pressure drops to 17 mmHg
    • Interstitial F.O.P opposes B.H.P and stays at 25 mmHg
    • Since the IFOP is greater than the BHP, the flow reverses, and reabsorption takes place
    • (17 - 25 = -8 mm Hg)
    • *In healthy person, about 20 L are filtered daily from capillaries. About 17 L are reabsorbed. The remaining 3 L are reabsorbed by lymphatic system.
  137. Autoregulation
    • the ability of capillaries to regulate blood flow - so we can shunt blood to areas with higher demand
    • due to low oxygen in tissues
    • Is able to increase capillary blood flow:
    • - to muscles undergoing metabolic demand
    • - brain in areas of greater neural activity
    • - skin autoregulates oxygen & nutrients; neural mechanisms control body temp
    • - lungs operate in opposite way: low oxygen → vasoconstriction, high oxygen → vasodilation
  138. thoroughfare channel
    • main channel from capillary to venule
    • If precapillary sphincters are closed, blood flows here...
  139. venules
    smallest veins
  140. Why do veins need valves
    • to prevent backflow of blood
    • Since intravenous pressures are so low, and blood in veins travels against gravity, veins need valves to keep blood flowing the one direction.
    • The pumping action of the heart and contractions of skeletal muscle helps venous blood return to heart
  141. Varicose veins
    • happens when valves become incompetent and "floppy"
    • backflow and pooling of blood results
    • the pooling of blood increases the risk of clot formation
  142. venous stasis
    • pooling of blood in veins
    • causes varicose veins
  143. Vasoconstrictors
    • constricting vessels to increase BP
    • -epinephrine/norepinephrine
    • -ADH (antidiuretic hormone)
    • -angiotensin II
    • -endothelium-derived factors (substances released during low blood flow to enhance vasoconstriction)
  144. vasodilators
    • dilating vessels decreases BP
    • -ANP (atrial natriuretic peptide) secreted from right atrium w atrial pressure increases
    • Nitric oxide
    • Inflammatory mediators (histamine, prostacyclin, kinins)
    • Ethanol (inhibits ADH & vasomotor)
  145. blood flow
    • the volume of blood that flows through any tissue in a given time period
    • Controlling flow is important:
    • tissues need adequate b.flow to receive oxygen & nutrients
    • blood that flows too slow is prone to clots
    • tissues more active need more blood, while inactive tissues require less
  146. Recall Ohm's law; how can it be used to calculate blood flow?
    • Ohms law: V = I x R ; where V = Voltage, I = current, R = resistance.
    • Can change that to: V = pressure, I = flow rate, R = resistance
    • Therefore ⇉ P = F X R

    • To figure flow rate, get F by itself: Image Upload 2
    • Need to account for difference in arterial & venous pressure:

    Image Upload 3
  147. an equation which gives us the relationship btwn the radius of a vessel and resistance to blood flow
    Image Upload 4

    • R = resistance to blood flow
    • η = blood viscosity
    • L = total length of all blood vessels in body
    • r = radius of vessel
    • *r4 =stands for radius of vessel raised 4x. As radius gets bigger, resistance decreases.
    • Ex: if vessel vasodilates, and diameter doubles in size. If you plug 2 into the equation for r, that vessel now has 16x the flow rate.
    • L : As we get older, and/or gain weight, we have to grow blood vessels to feed fat cells. So we increase our # of vessels, and total length goes up.  This contributes to resistance
  148. Explain the equation: flow α r4
    Says: blood flow is proportional to r4

    • flow, as in blood flow
    • α - symbol meaning "is proportional to"
    • r- remember, radius is from center of circle to edge. So this measures total area of lumen
  149. hypertension
    • high BP
    • results from arteries losing elasticity, which affects their ability to vasodilate or vasoconstrict and regulate blood flow
    • Reasons for elasticity loss: plaque accumulation, age
  150. laminar flow
    • when a fluid flows in parallel layers, with no disruption between the layers
    • therefore, describes most efficient way liquids can flow
    • Friction w walls of vessel reduces velocity at edges
    • Center of vessel, flow is fastest
    • *Ex used in book compared blood flow to the flow of traffic. Just as traffic is divided into lanes, blood separates into layers as it flows
  151. Turbulent flow
    • occurs when laminar flow is disrupted
    • If blood cells encounter a rough surface along edges, causes fluid levels to mix
    • This can activate platelets causing blood clots
  152. Changes in body that lead to increased BP
    • Increase in cardiac output
    • Increase in vascular resistance
  153. What common causes will cause an increase in cardiac output, which results in increased BP?
    • blood volume increase, skeletal muscle pump, respiratory pump, vasoconstriction of veins all lead to increased venous return. 
    • Decreased parasympathetic and increased sympathetic impulses. 
    • This leads to increased HR and stroke volume = increased cardiac output = Increased BP
  154. What common causes will cause an increase in vascular resistance, which results in increased BP?
    • Increased # of red blood cells, as in polycythemia = increased blood viscosity
    • Increased body size, as in obesity = increased total blood vessel length
    • Vasoconstriction
    • ALL THESE LEAD to increased systemic vascular resistance = increase in BP
  155. what part of the heart cycle is measured when taking BP
    • Systolic BP is measured during left ventricular systole, when aortic valve is open
    • Diastolic BP is measured during left ventricular diastole, when aortic valve is closed
    • *BP usually measured in the larger conducting arteries (duh)
  156. What's the official name of a blood pressure cuff
  157. mmHg
    a unit that describes the height that a column of mercury (Hg) could be raised by the pressure we've measured
  158. hypertension
    • elevated systemic arterial BP (duh)
    • Systolic BP over 140
    • Diastolic BP over 90
  159. What kind of complications can come from hypertension?
    • stroke
    • retinal hemorrhage
    • atheroscierotic plaque formation
    • ventricular hypertrophy (enlargement the heart)
    • glomerulosclerosis (harding in kidneys from pressure)
    • aneurysm
  160. prehypertension
    • a category used to indicate an individual at risk of developing hypertension
    • Pressures classified as prehypertensive:
    • Systolic pressures of 121-139
    • diastolic pressures of 81-89
  161. hypotension
    • low BP (duh) that's too low to deliver oxygen and nutrients to vital organs
    • typically defined by S&S rather than #'s
  162. atherosclerosis
    • the build-up of fatty plaque in the arteries that affects BP in 2 ways:
    • decrease in elasticity of arteries
    • decrease in diameter of arteries 
    • leads to hypertension
  163. shock
    a failure of the cardiovascular system to deliver enough oxygen and nutrients to meet cellular needs
  164. Baroreceptor reflexes
    • homeostatic loops that regulate BP
    • baroreceptors that sense pressure are found in aorta, internal carotid arteries, & other large arteries in chest n neck
  165. What involvement does the baroreceptors in the kidneys have in regards to hypotension
    • Kidneys release renin which initiates the renin-angiotensin-aldosterone system
    • Increased renin results in angiotensinogen becoming angiotensin II (in the blood):
    • ~acts on adrenal cortex to release aldosterone
    • ~leads to conservation of salt and water in kidneys AND vasoconstriction of vessels
    • Result: increase BP
  166. What involvement does the baroreceptors in the aorta and carotid sinus play in hypotension
    • 1- stimulates the hypothalamus/posterior pituitary to release ADH, which conserves water from kidneys
    • 2-alerts the cardiovascular center in medulla, which responds by increasing sympathetic stimulation and hormones from adrenal medulla. This causes an increase in heart rate, contractility, and vasoconstriction
    • Net result is to raise BP
  167. How does the baroreceptor reflex detect increased BP?
    How does it detect low BP?
    • increase in BP is detected by stretching at the baroreceptors; impulses are sent at a faster rate to medulla
    • Low BP is detected by the baroreceptors being stretched less; impulses are sent at a slower rate to medulla
  168. What's the baroreceptor reflex response to increased BP
    • ~nerves from medulla increase parasympathetic stimulation by the vagus nerve and decrease sympathetic stimulation
    • ~Rate of impulses on sympathetic neurons to the vessels slow, causing vasodilation. 
    • BP drops as result
  169. What's the baroreceptor reflex response to decreased BP
    • ~The cardiovascular center (in medulla) decreases parasympathetic stimulation & increases sympathetic stimulation
    • ~Adrenal medulla increases secretion of epinephrine and norepinephrine
    • ~Blood vessels constrict
    • BP increases as result
  170. Chemoreceptor reflex
    • sense the chemical composition of the blood
    • chemoreceptors are located close to baroreceptors in carotid bodies (where carotid artery splits) and the aorta (aortic bodies)
    • Detect O2, CO2, and H+ levels
  171. What happens in the chemoreceptor reflex under conditions of:
    hypoxia (low O2)
    acidosis (high H+)
    hypercapnia (high CO2)
    • signals are sent to the cardiovascular center in medulla
    • response is an increase in sympathetic stimulation to arterioles and veins causing vasoconstriction and increasing BP
    • Signals are also sent to respiratory center to adjust n increase the depth and rate of breathing
  172. describe sympathetic control of BP
    • Recall arteries have thick muscle layer
    • This muscle layer is responsive to sympathetic stimulation (epinephrine & norepinephrine)
    • *recall sympathetic/parasympathetic control is our mechanism to shunt blood to essential organs & decrease blood flow to non-essential organs (depending on the moment)
  173. Name 3 types of receptors in the thick muscle layer of arteries & their affects
    • responsive to sympathetic stimulation by Epinephrine/norepinephrine:
    • α1 adrenergic receptors - cause vasoconstriction
    • α2 adrenergic receptors - cause vasoconstriction
    • β2 adrenergic receptors - cause vasodilation
  174. hormonal control of blood pressure:
    • Hormones provide long-term control of BP
    • Renin-angiotensin-aldosterone system (RAAS) of kidney acts to conserve more sodium and subsequently more water from the kidneys & eliminate potassium
    • This increases blood volume & pressure
  175. Describe what happens w hypotension & steps in RAAS control on BP
    • Hypotension: can result from dehydration, Na+ deficiency, or hemorrhage
    • Results in decreased blood volume & BP
    • Kidney's release renin, Which stimulates angiotensin I to become angiotensin II
    • This stimulates adrenal cortex to release Aldosterone
    • Results in kidneys returning more Na+ & water to blood, and eliminating more K+ in urine
    • End result is increase in blood volume & BP
  176. Describe venous reserve
    • Since veins & venules contain a large % of blood volume (approx 60%), they function as blood reservoirs from which blood can be diverted quickly if needed.
    • If massive blood loss occurs, baroreceptors of carotid sinus signal emergency
  177. Distribution of blood in the body
    • Involves approx 5 L:
    • 9% Pulmonary vessels
    • 7% Heart
    • 13% Systemic arteries & arterioles
    • 7% Systemic capillaries
    • 64% systemic veins & venules (blood reservoirs)
    • Other 1L in organs w venous reserves:
    • spleen, liver, large ab veins, venous plexi under skin
  178. standard abbreviation for artery
    • A
    • multiple arteries are AA
  179. circle of Willis
    • Also called cerebral arterial circle
    • is an anastomosis at base of brain
    • formed from branches of the R & L internal carotid and also basilar arteries
  180. anastomosis
    • ~Recall that mostly, arteries branch like a tree as they move away from the heart
    • At anastomoses, arteries form a circle
    • branches fuse off of that
    • often to provide a " backup plan" if one route of blood supply is blocked
    • ex: found at the base of the brain (circle of Willis)
  181. 3 branches of arteries which rise from aortic arch
    • Left common carotid
    • Left subclavian
    • (Right) brachiocephalic trunk
  182. Ridiculous name changes of artery supplying upper extremity
    • subclavian A → crosses clavicle & becomes...
    • axillary A → crosses plane of shoulder joint & becomes...
    • brachial A
  183. vertebral veins
    • originate in occipital area of brain
    • they descend through foramina of cervical vertebrae & empty into brachiocephalic veins of neck
  184. brachial veins
    • paired
    • drain forearms, elbow joints, arms, and humorous
  185. principal veins for draining blood from upper limbs
    basilic and cephalic
  186. internal & external iliac veins
    • join to form common iliac vein
    • drain pelvis, external genitals, & lower limbs
  187. hepatic portal vein
    • veins which drain digestive organs lead here
    • supplies liver w blood to be filtered
  188. renal veins
    bring filtered blood back to systemic circulation
  189. great saphenous veins
    • longest veins in body, traveling from foot to groin
    • used for grafts in coronary bypass surgery
  190. How is blood delivered to coronary circulation
    when ventricles relax (Ventricular diastole), blood from aorta flows back and fills the coronary circulation
  191. circumflex
    • branch of left coronary artery
    • takes oxygenated blood to walls of left ventricle and left atrium
  192. LAD
    • left anterior descending 
    • also called anterior interventricular
    • branch of left coronary artery
    • delivers oxygenated blood to walls of both ventricles
  193. marginal
    • branch of right coronary artery
    • takes blood to right ventricle
  194. posterior interventricular branch
    • branch of right coronary artery
    • takes blood to walls of both ventricles
  195. angina pectoris
    • severe pain in chest
    • may accompany coronary ischemia, or decreased oxygen to heart muscle
  196. angioplast
    • balloon that pushes on artery walls
    • has blades that cut out blockage in coronary artery
  197. Principle coronary veins
    • great cardiac vein
    • anterior cardiac vein
    • middle cardiac vein
    • small cardiac vein
    • *all drain into coronary sinus which drains directly into right atrium
  198. great cardiac vein
    • lies in anterior interventricular sulcus
    • drains ventricles and left atrium
  199. anterior cardiac vein
    • drains right ventricle
    • opens directly into right atrium
  200. middle cardiac vein
    • lies in posterior interventricular sulcus
    • drains posterior left and right ventricles
  201. small cardiac vein
    drains right atrium and right ventricle
  202. systemic circulation
    includes the arteries and arterioles that carry oxygenated blood from the left ventricle to systemic capillaries, plus the veins and venules that return deoxygenated blood to the right atrium
  203. pulmonary circuit
    carries deoxygenated blood from right ventricle to the alveoli within the lungs and returns oxygenated blood from the alveoli to the left atrium
  204. Where does lymphatic duct drain back into venous circulation
    junction of internal jugular and subclavian veins
  205. Key facts about fetal circulation
    • fetus has special circulation requirements cause it's lungs, kidneys, and GI tract are non-functional
    • fetus derives oxygen and nutrients & eliminates metabolic wastes through maternal blood supply by way of the placenta
  206. How does baby get oxygenated blood
    from the placenta through the umbilical vein (this vessel is going towards the fetal heart, therefore it's a vein)
  207. ductus venosus
    • the fetal vein which carries blood from the umbilical vein
    • bypasses the fetal liver and enter the inferior vena cava with oxygenated blood
  208. Explain path of fetal circulation
    • Oxygenated blood leaves placenta through umbilical vein
    • bypasses liver via ductus venosus & enters inferior vena cava
    • Blood enters right atrium
    • bypasses lungs by traveling directly to left heart through foramen ovale
  209. What happens to remaining blood in right heart that manages to flow through to right ventricle
    • meets w very high resistance from closed and soggy lungs
    • is diverted into left-sided circulation by passing through ductus arteriosus (btwn pulmonary outflow tract and aorta)
    • It then returns to the placenta via the umbilical arteries
  210. placenta
    fetal and maternal oxygen, nutrients, and wastes diffuse btwn fetal and maternal blood (no mixing)
  211. Umbilical vein
    carries oxygenated blood to fetal heart
  212. ductus venosus
    bypasses the fetal liver
  213. foramen ovale
    shunts blood from the right to left atrium bypassing the right ventricle and lungs
  214. ductus arteriosus
    diverts blood from the right pulmonary trunk to the aorta (bypasses the lungs)
Card Set
HTHS Mod 16