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24-25 HUMAN PHYSIOLOGY > The Cardiovascular System > Flashcards

The Cardiovascular System Flashcards

1
Q

Describe the composition of blood

A
  • formed elements
    • majority RBC
    • % RBC in centrifuged blood sample = hematocrit
  • plasma
    • H2O, dissolved solutes
    • ions, metabolites, hormones, antibodies
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2
Q

Name the proteins in plasma

A
  • Albumin
    • Creates colloid osmotic pressure
    • Maintains blood volume and pressure
  • Globulins
    • Carry lipids
    • Gamma globulins = antibodies
  • Fibrinogen
    • Clotting factors
    • Converts to fibrin
    • Serum is left after blood clots
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3
Q

Describe the properties of RBC

A
  • Flattened biconcave discs
  • Increases SA for diffusion
  • Lacks nuclei and mitochondria
  • Each holds 280M hemoglobin molecules
  • 300M RBCs produced every day
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4
Q

Describe the general structure of blood vessels (three layers)

A
  • Tunica externa
    • collagen fibres for protection and structural reinforment
    • loose connective tissue
  • Media
    • smooth muscle, collagen, elastic fibres
    • initiate vasoconstriction/vasodilation
  • Tunica interna
    • endothelium (simple squamous endothelium): selectively permeable barrier
    • basement membrane
    • thin layer of connective tissue
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5
Q

Describe the features of arteries

A
  • Carries blood away from the heart
  • Elastic arteries
    • Largest and thickest
    • More elastin to withstand high blood pressure
    • Expands during systole, recoils during diastole → maintains smooth blood flow
  • Muscular arteries
    • Most abundant
    • Deliver blood to specific organs
  • Arterioles
    • Smallest
    • Lead into capillary beds
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6
Q

Describe the features of capillaries

A
  • Networks between arteries and veins
  • Extensive SA → Exchanges dissolved gases, nutrients, wastes
  • Determinded by precapillary sphincters → controls location of blood flow to where it is needed
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7
Q

Describe the three types of capillaries

A
  • Continuous capillaries
    • Found in skin and muscle
    • Endothelial cells tightly joined
    • Narrow intercellular channels → exchange of molecules smaller than proteins
    • In muscle, lungs, adipose tissue
  • Fenestrated capillaries
    • Filtration pores that penetrate endothelial lining
    • Rapid passage of small molecules
    • In brain, endocrine organs, intestinal tract, kidneys
  • Sinusoids
    • irregular blood-filled spaces
    • wide gaps
    • allows entry of albumin, clotting factors, proteins from the liver
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8
Q

Describe features of veins

A
  • Carries blood towards heart
  • Large lumen, low blood pressure → Contains majority of blood
  • Compliant (expands readily)
  • Blood moved towards heart by skeletal muscle pump
  • 1-way venous valves → blood moves in one direction
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9
Q

Describe the three layers of the heart

A
  • Heart wall
    • Epicardium (outer layer)
    • Covers the heart
  • Myocardium
    • Thick muscular wall in the middle
    • Concentric layers of cardiomyocytes
    • Coil around heart in a spiral (vortex)
    • Wringing contraction to enhance blood ejection
  • Endocardium
    • Lines interior of heart chambers
    • Cover the valves
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10
Q

Describe features of the cardiac muscle tissue

A
  • Intercalated discs (dark bands)
  • Single, central nucleus
  • Branching interconnections between cells
  • Linked by gap junctions → enable communication, form channels for movement of ions
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11
Q

Describe the structure of the heart

A
  • 2 atria: receive blood from venous system
  • 2 ventricles: pump blood to arteries
    • Right ventricle wall: thinner, less pressure, pouch-shaped
  • Cardiac (fibrous) skeleton
    • Layer of dense connective tissue
    • Structural support
    • Electrical insulation between atria and ventricles → prevents electrical signal from going to ventricles
  • 2 pumps separated by muscular septum
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12
Q

Right ventricle VS Left ventricle

A
  • Right: Thinner, develops less pressure, pouch-shaped
  • Left: round
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13
Q

Describe the valves of the heart

A
  • Each valve consists of 2-3 cusps: fibrous flaps of tissue
  • Atrioventricular valves: between atria and ventricles
    • Tricuspid: between RA and RV
    • Bicuspid: between LA and LV
    • Closing causes “lub” sound
  • Semilunar valves
    • Pulmonary valves: between pulmonary arteries and RV
    • Aortic valves: between aorta and LV
    • Closing causes “dub” sound
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14
Q

Describe the two types of cardiac muscle cells

A
  • Conducting/pacemaker cells: initiates and conducts electrical impulses, controls and coordinates heartbeat
  • Contractile/myocardial cells: stimulated by electrical impulses, produce contractions to propel blood
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15
Q

Describe the cardiac cycle

A
  1. SA node: impulse to atria, atria contracts
  2. AV node: delays impulse to ventricle, ensure atria has ejected all blood into ventricles
  3. AV Bundle (Bundle of His)
  4. Left and right bundle branches
  5. Purkinje fibres
  6. Papillary muscles contract
  7. Ventricular muscles contract
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16
Q

Describe the features of the SA node

A
  • In the posterior wall of RA
  • Contains pacemaker cells
  • Connected to AV node by internodal pathways
  • Does not contract, only generates signals
17
Q

Distinguish the features of an electrocardiogram

A
  • P wave: atria depolarize → systole (atria contracts)
  • P-Q segment: time for signals to travel from SA node to AV node
  • QRS complex: ventricular depolarize + atria repolarize (obscured)
  • S-T segment: plateau in myocardial action potential → ventricles contract
  • T wave: ventricles repolarize → diastole (ventricles relax)
18
Q

Describe the action potential in pacemaker cells

A
  • Resting membrane potential: -60mV
  • Pacemaker potential: “funny” channels allow slow influx of sodium ions → spontaneous depolarization reaches threshold -40mV
  • Rising (depolarization): calcium channels allow influx of calcium ions
  • Falling (repolarization): potassium channels allow outflow of potassium ions → returns to -60mV
19
Q

Describe the action potential in contractile/myocardial cells

A
  • Resting membrane potential: -90mV
  • Sodium, calcium ions leak thru gap junctions to the adjacent cell → threshold -70mV
  • Rapid depolarization: Fast sodium channels allow rapid influx of sodium ion
  • Early repolarization: Fast sodium channels close, potassium channels allow outflow of potassium ions
  • Plateau: Slow calcium channels allow influx of calcium ions to balance potassium efflux
  • Repolarization: Potassium efflux predominates → returns to -90mV
20
Q

Compare contraction and refractory periods of cardiac and skeletal muscles

A
  • Contraction
    • Cardiac muscle: contracts longer due to plateau phase → allows expulsion of blood from heart chambers
  • Refractory period
    • Cardiac muscle: longer → ensures muscles have relaxed before responding to new stimulus, prevents summation and tetany

24-25 HUMAN PHYSIOLOGY (11 decks)

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