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S2 Bio 109 A&P 2 > Physiology of heart > Flashcards

Physiology of heart Flashcards

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1
Q

Facts

A
  • heart beats 115,000x/day
  • 2000 gallons of blood/day
  • aorta is almost the diameter of a garden hose
  • capillaries are so small that it takes ten of them to equal the thickness of a human hair
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2
Q

Hemodynamics

A

Used to describe a collection of mechanisms that influence the active and changing (dynamic) circulation of blood

  • circulation of different volumes of blood per minute at different times is essential for survival
  • circulation control mechanisms must accomplish 2 functions: maintain a circulation and vary volume and distribution of the blood circulated
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3
Q

Cardiac cycle

A

Complete heartbeat or pumping cycle consisting of contraction (systole) and relaxation (diastole) of both atria and both ventricles

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4
Q

Systole

A

Contraction of both ventricles of the heart forcing blood out of these chambers
- atria are in a relaxed state

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5
Q

Diastole

A

Ventricular muscles relax, allowing for blood to fill these chambers
- at the end, the atria start contracting to fill the ventricles

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6
Q

Pic

A

Pic

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7
Q

Autorhythmic cardiac muscle fibers

A

These repeatedly generate action potentials that trigger contraction

  • they continue to stimulate a heart beat even after the heart has been removed from the body (for several minutes)
  • ensures that the cardiac chambers are stimulated to contract in a coordinated manner
  • hormones, chemicals, and nerve impulses can alter the heartbeat strength and heart rate but do not change the coordinated contractions of the heart
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8
Q

Conduction system has four structures

A
  1. Sinoatrail node
  2. Atrioventricular node
  3. AV bundle (bundle of His)
  4. Subendocardial branches (purkinje fibers)
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9
Q

Pic

A

Pic

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10
Q

Pic

A

Pic

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11
Q

SA node

A

Natural pacemaker of the heart

  • initiates each heartbeat and sets its pace
  • located high in the R atrial wall
  • impulses spread from the SA node to the muscle fibers of both atria causing atrial contraction
  • fires between 60-100 BPM
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12
Q

AV node

A

Acts as the only gateway for electrical impulses from the atria to the ventricles

  • located at the base of the R atrium
  • electrical activity travels very slowly thought the AV node
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13
Q

AV bundle (bundle of His)

A
  • AV node stimulation sends impulses to the AV bundle of His
  • the bundle of His carries electrical impulses (action potentials) into the ventricles
  • bundle of His impulses travel though the R and L bundle branches to the purkinje fibers
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14
Q

Subendocardial branches

A

Purkinje fibers
- fibers that further spread electrical activity to all parts of the ventricles so that there is a coordinated contraction of each ventricle

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15
Q

electrocardiogram

A

ECG or graphic record of the heart’s electrical activity, specifically the conduction of impulses

  • it is not a record of the heart’s contractions, but of the electrical events/current that precede them
  • a composite record of action potentials produced by the heart muscle fibers during each heartbeat
  • changes in voltage are seen as deflections of a line drawn on a paper or traced on a video monitor
  • the normal ECG is composed of defection waves called P wave, QRS wave, and T wave
  • 12lead ECG obtains 12 electrical tracings of the heart from different angles or orientations
  • patterns of abnormalities can indicate areas of abnormal conduction
  • these abnormalities can correlate to areas of decreased blood flow
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16
Q

ECG pic

A

Pic

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17
Q

P wave

A

Represent depolarization of the atria

- deflection related to passage of an electrical impulse from the SA node thought the muscle of both atria

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18
Q

QRS complex

A

Represents depolarization of the ventricles and repolarization of the atria

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19
Q

T wave

A

Represents ventricular repolarization

20
Q

P-R interval

A

The length of time for atrial depolarization and conduction from the SA node to the AV node

21
Q

ST interval/segment

A

The time period from the end of ventricular depolarization through ventricular repolarization
- clinically, unhealthy myocardium can affect the height of this interval (either upward or downward)

22
Q

Cardiac cycle

A
  • complete heartbeat consisting of systole and diastole of both atria and ventricles
  • two atria contract simultaneously filling the ventricles more efficiently
  • as the atria relax, the two ventricles contract, instead of the entire heart contracting as one unit. Allows for a pumping action o the heart
23
Q

Cardiac cycle events

A
  • atrial systole
  • isovolumetric ventricular contraction
  • ejection
  • isovolumetric ventricular relaxation
  • passive ventricular filling
24
Q

Atrial systole

A
  • begins with the P wave of the ECG: electricity precedes contraction
  • the atria contract simultaneously completing emptying blood out of the atria into the ventricles
  • AV valves are open
  • SL valves are closed
  • ventricles are relaxed and filling with blood
25
Q

Chart

A

Chart

26
Q

Isovolumetric ventricular contraction

A
  • onset of ventricular systole coincides with R wave and appearance of the first heart sound (S1), as the AV valves close
  • between the start of ventricular systole and the opening of the SL valves
  • volume in the ventricles remains constant as the pressure increases rapidly = isovolumetric contraction
27
Q

Ejection

A
  • pressure increases enough to open the aortic and pulmonary SL valves and blood is ejected from the heart
  • blood enters the systemic and pulmonary circulations via the aorta and pulmonary artery
  • this period coincides with ST interval
  • residual volume: the blood that remains in the ventricles at the end of the ejection period (roughly half)
28
Q

Isovolumetric ventricular relaxation

A
  • ventricular diastole/relaxation begins with an isovolumetric period
  • occurs between closure of the SL valves and opening of the AV valves
  • closure of the SL valves produce the second heart sound (S2)
  • this corresponds to the T wave and continues until the next P wave
  • there is a dramatic fall in intraventricular pressure
29
Q

Passive ventricular filling

A
  • returning venous blood increases intraatrail pressure until the AV valves are forced open and blood rushes into the relaxing ventricle
  • results in a dramatize increase in ventricular volume before the atria contract
  • lasts about 0.1 sec
30
Q

Cardiac output

A

Amount of blood that flows out of a ventricles of the heart per unit of time
- (mL/min) = stroke volume (mL/beat) x HR (beats/min)

31
Q

Stroke volume

A

Measured by the mL of blood pumped out of the L ventricles in one stoke (beat)

32
Q

At rest vs during exercise

A

CO = SV (70mL/beat) x HR (75bpm) = 5250 mL/min

CO = SV (140 mL/beat) x HR (150 bpm) = 21000mL/min

33
Q

Heart sounds

A
  • the heart makes certain typical sounds during each cardiac cycle
  • sounds like lub dup
  • sounds are created by blood turbulence and vibration as valves close
  • **
  • S1, lub: comes with the closure of the mitral and tricuspid valves as ventricular systole begins
  • S2, dup: comes with the closure of the aortic and pulmonary SL valves as systole ends and diastole begins
  • any variation from normal in these sounds indicates imperfect functioning of the valves
  • surgery can repair damaged valves
34
Q

Pic

A

Pic

35
Q

Stethoscope

A
  • using the bell is most useful for low sounds nand may work best with pediatric patients
  • using the diaphragm is most useful for higher pitch sounds
36
Q

Pic

A

Pic

37
Q

Using a stethoscope

A
  • with men, the stethoscope can be placed under the shirt or removal of the shirt if necessary
  • with women, it may be necessary to remove bra, and/or use a gown
  • with women, it may be necessary for the pt to move the left breast, so that the stethoscope can be applied to the chest wall in the correct positions
  • clean stethoscope bell/diaphragm with alcohol between pts
38
Q

Pic

A

Pic

39
Q

Preload:

A

Degree of stretch on the heart prior to contraction

40
Q

Contractility

A

Forcefulness of contraction of individual ventricular mm fibers

41
Q

Afterload

A

Pressure that must be exceeded before the ejection of blood from the ventricles can occur

42
Q

CAD

A

Reduction of blood flow to the myocardium

  • leading cause of death for men and women
  • arteriosclerosis/atherosclerosis
43
Q

cardiomegaly

A
  • physiological: hypertrophy related to fitness training

- pathological: related to heart disease

44
Q

CHF

A
  • loss of pumping efficiency by the heart

- caused by CAD, congenital defects, long term high blood pressure, valve disorders

45
Q

Tachycardia

A

Heart rate higher than the normal SA node range 60-100

  • med related
  • hyperthyroidism
  • increase in interstitial Ca+
46
Q

Bradycardia

A

A resting heart rate under 50 BPM

  • can be normal depending on fitness level
  • med related
  • bradycardia
  • tachycardia
  • fibrillation

S2 Bio 109 A&P 2 (29 decks)

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