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Human Physiology (BIOL 2410/2420) > The Heart > Flashcards

The Heart Flashcards

1
Q

What is the function of the cardiovascular system?

A

Deliver “supplies” to cells far removed from the site of uptake/manufacture

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2
Q

What are 5 supplies and 3 wastes the cardiovascular system transports?

A
  1. O2 (via hemoglobin carrier due to insolubility of gases in blood)
  2. water and nutrients
  3. hormones
  4. antibodies/platelets/leukocytes
  5. heat
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3
Q

What are 3 wastes transported by the cardiovascular system?

A
  1. CO2 (via bicarbonate due to insolubility of gases in blood)
  2. urea (catabolism byproduct ammonia + CO2, protection from toxicity)
  3. creatinine (breakdown product of creatine phosphate in muscles)
  4. bilirubin (breakdown product of hemoglobin that is used to break down fats)
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4
Q

What are the three primary components of the cardiovascular system and their functions?

A
  1. blood: medium for bulk transport of materials
  2. heart: pump that generates hydraulic pressure gradient
  3. vasculatrue: closed dual circuit (pulmonary and systemic) for one way flow of blood
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5
Q

How does the bulk flow of blood work?

A

Unidirectional flow down hydraulic pressure gradient generated by the heart.

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6
Q

What is the pressure and resistance of the pulmonary circuit?

A

Pressure: low pressure due to short distance from heart to lungs and back.

Resistance: low resistance because the pulmonary vessels are shorter and wider

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7
Q

What is the pressure and resistance of the systemic circuit?

A

Pressure: high pressure due to large distanced covered by blood to the rest of the body.

Resistance: high resistance due to longer vessels and smaller arteries/arterioles, which create more friction against blood flow.

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8
Q

What is the relation between blood volume in the pulmonary and systemic circuit?

A

The same volume of blood is pumped from the left ventricle to the systemic circuit as the right ventricle to the pulmonary circuit.

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9
Q

What is blood? What are the 4 parts?

A

Complex suspension of water, solutes and formed elements 5-5.5 L in volume. Includes plasma, erythrocytes, leukocytes, platelets.

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10
Q

What is plasma made of?

A
  • 90% water
  • proteins
  • electrolytes
  • nutrients (glucose, AA, lipids, vitamins)
  • gases (N2, O2, CO2, NO)
  • metabolic waste products (urea, creatinine)
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11
Q

What are types of proteins found in the plasma?

A
  • albumin: carrier proteins for ligands and maintains osmotic pressure in the body
  • globulins: important for liver and kidney function, blood clotting, and immune system
  • Fibrinogens: plays a key role in blood clotting and wound healing
  • hormones: chemical messengers for cell communication
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12
Q

What is the function of electrolytes found in the plasma, and examples?

A

Purpose: help your body regulate chemical reactions and maintain the balance between fluids inside and outside your cells

Examples: Na+, Cl-, K+, HCO3-

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13
Q

How abundant are eryhtrocytes?

A

99% of blood cells in the body (5 billion per ml) and regenerate in the bone marrow 2mil per second. Make up 80% of the body’s cells.

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14
Q

What is the shape of erythrocytes?

A

Biconcave disk containing hemoglobin and lack organelles (contain all organelles when first formed).

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15
Q

What is blood serum?

A

Plasma where fibrinogen and other clotting proteins are removed as they plug diagnostic machines.

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16
Q

What is hematocrit (Hct)?

A

% of blood volume that is erythrocytes (42% in women, 47% in men)

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17
Q

What is erythropoeitin?

A

hormone released by kidney stimulating RBC production in response to low blood O2 saturation.

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18
Q

What is anemia and polycythemia?

A

Anemia: Plasma > RBC

Polycythemia: RBC > Plasma

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19
Q

What are leukocytes? Where are they found and for how long?

A

White blood cells that play a central role in the body’s immune response. They are mobile and primarily act outside of the bloodstream with a life span of hours to years.

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20
Q

What are thrombocytes function and structure?

A

Function: aggregates to exposed collagen at wound sites and release serotonin for vasoconstriction

Structure: Cell fragments (nucleus lacking) shed into plasma from megakaryocytes ( in bone marrow).

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21
Q

What is the path of blood flow from the aorta?

A
  1. Aorta to systemic arteries and carotid arteries
  2. Arteries to arterioles in tissues
  3. arterioles to capillaries
  4. capillaries to venules
  5. venules to veins
  6. veins to superior and inferior venacavae
  7. venacavae to right atria
  8. right atria to right ventricle
  9. right ventricle to pulmonary arteries
  10. pulmonary arteries to lungs
  11. Lungs to pulmonary veins
  12. Pulmonary veins to left atrium
  13. Left atrium to left ventricle
  14. Left ventricle to aorta
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22
Q

What is microcirculation?

A

The circulation of blood from arterioles, through capillaries, and into venules where exchange occurs.

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23
Q

What is the difference in appearance of oxygenated and deoxygenated blood?

A

Deoxygenated: maroon due to valency when unbound to oxygen

Oxygenated: scarlet due to valency when bound to oxygen.

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24
Q

What are the three layers of the heart wall and its surrounding layer?

A

endocardium, myocardium, epicardium, pericardial sac

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25
Q

What is the endocardium?

A

Thin inner lining of the heart wall made of epithelial tissue specialized to monitor blood in the heart by releasing hormones.

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26
Q

What is the myocardium?

A

Middle lining of the heart wall that contains contractile muscle cells of intercalated discs arranged in circular (atria) and spiral (ventricles) patterns and connected via gap junctions for conduction.

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27
Q

What is coronary circulation?

A

The circulation of highly oxygenated blood from the first branches of the aorta to the myocardium.

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28
Q

what is epicardium?

A

inner layer of serous membrane that surrounds the heart and secretes lubricating pericardial fluid into pericardial cavity

29
Q

What is the pericardial sac?

A

Formed by epicardium and parietal pericardium fused to an outer fibrous pericardium. This prevents distension of heart and anchors it to diaphragm.

30
Q

What are the valves in the heart?

A

atrioventricular valves: between atria and ventricles (bicuspid left, tricuspid right)

semilunar valves: between ventricles and main arteries

31
Q

How does the one way valve system work?

A

Positive pressure in front of the valve will cause it to close, and behind the valve will cause it to open.

32
Q

What is the purpose of the connective tissue ring?

A
  1. Encircles valves
  2. Separates atria and ventricles
  3. stops spread of action potentials between structures
  4. provides firm origin and insertion sites for cardiac muscle
33
Q

What is a heartbeat?

A

orderly wave of contraction that sweeps through the myocardium coordinated by autorhythmic cells and large-diameter conducting cells.

34
Q

What are autorhythmic pacemaker cells?

A

pacemaker cells primarily found in the right atria, including the sinoatrial node (75 depolarization/min) and atrioventricular node (50 depolarization/min ONLY IF sinoatrial is not working)

35
Q

What are large diameter conducting cells?

A

Cells that allow for rapid spread of depolarization from SA/AV nodes through the heart via internodal and interatrial pathways

36
Q

What is the difference between internodal and interatrial pathways?

A

Internodal: carry impulses generated in SA node to AV node

Intertatrial: carry impulses generated in SA node to left atrium so atria contract in unison

37
Q

What is the atrioventricular bundle?

A

Sole electrical pathway connecting the atria to the ventricles that splits into two bundle branches going down the septum

38
Q

What are purkinje fibers?

A

Extensive network of branches that spread upwards towards the valves, resulting in simultaneous contraction of ventricles from apex upwards

39
Q

Why do myocytes have long duration action potentials

A

There is prolonged opening of Ca2+ channels to prevent summation and tetanus (seizing), as well as allows for adequate time for heart chambers to refill between beats.

40
Q

What is an electrocardiogram?

A

Reading of overall spread of electrical activity through the heart by electrodes spread out on the skin surface

41
Q

What are the segments of an ECG?

A
  1. P wave (atria contracts)
  2. PR segment (atria finishes contracting and empties)
  3. QRS segment (ventricles depolarize and contract)
  4. ST segment (contracted ventricles empty)
  5. T wave (ventricles repolarize and are empty half way through)
  6. TP segment (ventricles relax and passively fill)
42
Q

What are types of ECG abnormalities?

A

Atrial fibrillation: no P wave, and irregular QRS complex rhythm

Pre-ventricular contractions: singular heartbeat is initiated by Purkinje fibers

Ventricular fibrillation: heart muscle does not depolarize synchronously making pumping impossible

Heart block: damage to the AV node

43
Q

What are the 4 degrees of heart block?

A

1st degree: decreased rate of AP movement through AV node (longer PR)

  1. 1 of every 3 to 5 atrial AP waves is dropped (lack of QRS)
  2. complete blockage of signal from atria to ventricles, causing atria to be driven by SA node, and ventricles to be driven by AV node
44
Q

What is the difference between systole and diastole?

A

Systole: period of ventricular contraction

Diastole: period of ventricular relaxation

45
Q

What are the steps in the cardiac cycle?

A
  1. Isovolumetric contraction: Ventricle is full and begins to contract, creating increased ventricular pressure that closes AV valves
  2. Ventricular ejection: When ventricular pressure > aortic pressure, semilunar valve opens and ejects stroke volume until ventricular pressure < aortic pressure, which causes semilunar valves to close
  3. Isovolumetric relaxation: Ventricle has emptied and begins to relax, decreasing ventricular pressure which triggers opening of AV valves
  4. passive ventricular filling: After AV valves open, blood from relaced atria begins to pass into ventricles
  5. Atrial contraction: SA node depolarizes atrial cells which ‘tops-up’ ventricles with 20% more blood.
46
Q

What does the lub-dub of a heartbeat signify?

A

Lub: closing of atrioventricular valves

Dub: closing of semilunar valves

47
Q

What are heart murmurs?

A

Whooshing sounds in lub-dub due to backflow of blood as a result of leaky valves

48
Q

What is stroke volume?

A

volume of blood pumped out of the heart’s left ventricle during each systolic cardiac contraction at rest (EDV-ESV)

49
Q

What is the difference between systolic pressure and diastolic pressure?

A

Systolic: maximum pressure measured in the aorta midway through ventricular ejection (120mmHg)

Diastolic: minimum pressure measured in aorta at end of isovolumetric contraction (80mmHg)

50
Q

What is Mean arterial pressure?

A

Driving force that pushes blood through the systemic circuit, measured as the average aortic pressure during the entire cardiac cycle. (~93 mmHg)

51
Q

Why is the mean arterial pressure lower than the average of systolic and diastolic pressure?

A

The heart spends more time in diastole than systole, therefore it is weighted as 66:33 instead of 50:50

52
Q

What is the difference between end diastolic volume and end systolic volume?

A

EDV: maximum ventricular volume attained during cardiac cycle

ESV: minimum ventricular volume attained during blood ejection phase

53
Q

What is the cardiac output?

A

Rate at which each ventricle pumps blood. Determined via Heart rate x Stroke volume.

54
Q

Whats the difference between heart rate, stroke volume, and cardiac output at rest and during exercise?

A

Rest:
- heart rate: 72 beat/min
- stroke volume: 0.07 L/beat
- cardiac output: 5 L/min

Exercise:
- heart rate: 200 beat/min
- stroke volume: 0.125 L/beat
- cardiac output: 25 L/min

55
Q

How does training affect the cardiac output?

A

Training increases heart muscle mass, which increases the amount of liters ejected per beat, which decreases heart rate.

56
Q

What are factors that affect heart rate?

A
  1. Neural control: parasympathetic and sympathetic branches of autonomic nervous system
  2. Hormones: Catecholamine secretion (norepi/epi) in response to sympathetic activity reinforces effects of sympathetic neural input.
57
Q

How does the sympathetic nervous system control heart rate?

A

smpathetic neurons relesase norepi that binds to beta adrenergic receptors on autorhythmic cell membranes and stimulates the cAMP second messenger system.

58
Q

What does the stimulation of cAMP via norepi in autorhythmic cell membranes do?

A
  1. Increases influx of Na+ and Ca++ into PACEMAKER CELLS, increasing the slope of spontaneous depolarization which causes SA node to reach its AP threshold faster.
  2. Increases speed of action potential transmission in CONDUCTING CELLS, decreasing duration of systole
59
Q

How does the parasympathetic nervous system affect heart rate?

A

Parasympathetic neurons of vagus nerve (cranial nerve 10) release Acetylcholine that binds to muscarinic receptors on cell membranes of SA node and AV node.

60
Q

What does Acetylcholine do when bound to membrane receptors on SA node and AV node?

A

SA: increases K+ permeability (hyperpolarizes membrane, decreasing slope) and slows inward movement of Ca2+ and Na+

AV: decreases speed of AP movement through AV node, increasing systole duration

61
Q

What are factors that afect stroke volume?

A
  1. Neural control
  2. Hormonal control
  3. EDV influence (preload)
  4. Afterload
62
Q

How do sympathetic neurons control stroke volume?

A
  1. Sympathetic neurons release norepi which binds to beta-adrenergic receptors and stimulates cAMP system
  2. Increases rate of Calcium ATPase taking in Ca++ into SR, increasing speed of muscle relaxation.
  3. Increases force of atrial contraction, increasing EDV
  4. Vasoconstrict peripheral veins increasing speed of venous return to the heart, increasing EDV
63
Q

How does cAMP system stimulation influence stroke volume?

A

Stimulates Ca++ induced Ca++ release from sarcoplasmic reticulum, increasing ventricular contractile strength at any given end diastolic volume.

64
Q

What are the steps for calcium induced calcium release?

A
  1. AP opens voltage gated calcium channels in contractile cells, allowing influx of Ca++ into cytoplasm
  2. Cytoplasmic Ca++ triggers Ryanodine receptor on sarcopalsmic reticulum, resulting in mass Ca++ release into cytoplasm
  3. Mass Ca++ release increases sensitivity of troponin which allows it to move faster, reducing the duration of the cross-bridge cycling.
65
Q

What is important about the sympathetic nervous system controlling stroke volume?

A
  1. Stronger atrial contractions fills the ventricles more, and stronger ventricular contractions eject a larger fraction of EDV
  2. Increasing contraction/relaxation speed, decreases systole duration and allows sufficient time for the heart to refill during exercise. (0.15s SYS: 0.15 DIA)
66
Q

How do hormones affect stroke volume?

A

Epinephrine released from the adrenal medulla influences cAMP levels within contractile cells

67
Q

How does EDV influence stroke volume via Frank-Starling law?

A

Increase in EDV stretches myocardium to optimal position with max active actin/myosin crossbridges. This allows a more powerful contraction to eject the increased EDV.

68
Q

How does afterload affect stroke volume?

A

Stronger mean arterial pressure, the stronger the ventricles must contract to eject enough blood for the pressure to overcome the aortic pressure and open the semilunar valves.

69
Q

What diseases does increased afterload create?

A
  • Chronic hypertension: high BP = more resistance
  • stenosis of semilunar valves: narrowing of valves = more resistance
  • coarctation of aorta: narrowing of aorta = more resistance

Human Physiology (BIOL 2410/2420) (17 decks)

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