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PPoS > Intro to CVS (#1) > Flashcards

Intro to CVS (#1) Flashcards

1
Q

What is function of SVC?

A

Takes blood from head, neck and arms into R atrium

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2
Q

What is P in vena cavae?

A

~ 3-8mmHg (near atmospheric)

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3
Q

What is blood velocity and its function?

A

~ 25cm/sec gives blood momentum helping its entry into R atrium + vent

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4
Q

What is blood made up of and not abundant cells ?

A
  • 55% plasma

- 45% cells (RBCs most abundant)

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5
Q

What type of sol is blood and ions it contains?

A

Saline with Na+ + Cl- as most abundant cation + anion

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6
Q

What is osm + amount of albumin in blood?

A

~ 290mosmol/l

~ 70g/l

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7
Q

What is pO2, oxyHb sat and O2 content of blood?

A

~ 40mmHg
~ 75%
~ 150ml/l

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8
Q

What is pCO2 + CO2 content?

A

~ 46mmHg

~ 520ml/l

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9
Q

How is CO2 transported in blood?

A
  • HCO3-

- bound to proteins

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10
Q

Why is there higher pCO2 than pO2?

A

when blood goes through cap, it picks up CO2 + drops off O2

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11
Q

Which gases have less O2 - venous/arteriole?

A

venous

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12
Q

Describe process of heart contraction (atrial contraction)

A
  1. wave of dep/AP/contraction arises in SAN in R atrium
  2. Dep spreads into atria (R then L)
  3. Atrial contraction of myocytes + blood injected into vent
  4. Dep cond through AVN slowly to allow delay between atrial + vent contraction (both systole) so atria contract before vent
  5. Atria rep
  6. Atrial relaxation - can accept blood
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13
Q

What is cardiac contraction triggered by?

A

coord dep of myocytes

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14
Q

What is special about SAN AP?

A
  • never stable - mem begins to dep as soon as AP finished + get AP once reaches threshold
  • spontaneously recurring as mem pot between each AP not stable + continually dep
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15
Q

Describe SAN AP

A
  1. Pacemaker currents e.g. funny current
  2. VG L-type channels activated when dep reaches certain threshold + Ca2+ entry
  3. K+ channels open + K+ loss (rep)
  4. Phase 4 dep - rate of AP dep - controlled by ANS
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16
Q

Decsribe AP of other areas e.g. vent

A
  1. Rapid dep due to high conductance Na+ channels (phase 4 dep) - fast Na+ entry
  2. Ca2+ entry triggers contraction
  3. K+ loss (rep)
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17
Q

What is vent contraction triggered by?

A
  • triggered by Ca2+ (tension dev)
18
Q

What is special about vent AP?

A
  • stable RMP as v.few ions moving mem (no phase 4 dep)

- longer AP (300ms)

19
Q

Describe cardiac cond pathways of SAN

A
  • stim initiated in SAN located at junction of SVC + R
    atrium
  • diffuse cond through myocytes in atria (faster near origin of SAN so blood milked from top of atrium to bottom (1m/sec)
20
Q

How does wave of dep move through heart?

A
  • excitation can only pass through AVN

- atria rep as vent begin to dep emphasising the gap

21
Q

List 7 stages of cardiac cycle

A
  1. Atrial systole
  2. Isovol vent systole
  3. Rapid vent ejection
  4. Red vent contraction
  5. Isovol vent relaxation
  6. Rapid vent filling
  7. Red vent filling
22
Q

Describe Phase 1 of cardiac cycle

A
  • Atria contract - inc blood flow into vent by 10% - gives extra kick of blood via tricuspid + mitral valves.
  • Vent relaxed and therefore accept blood easily, allowing them to ~120ml = EDV
23
Q

What is EDV?

A

Vol at end of being filled (determine strength of heart contraction)

24
Q

What is sig of there being no valve between VC + RA?

A
  • nothing stopping blood going into R atrium from veins

- blood continually pouring into R atrium depending on P gradient

25
Q

Describe Phase 2 of cardiac cycle

A
  • Vent begin to contract.
  • As P within them inc, T + M valves close preventing back-flux of blood into atria.
  • P in vent builds up rapidly as blood has nowhere to go (so vol doesn’t change as a result).
  • (Outflow valves - aortic (L) + pul (R) valves still closed due to P in aortic + pul veins keep them shut so blood can’t go forwards either
26
Q

What is ejection fraction?

A

= diff between EDV + ESV

- 60% of blood in both vent ejected, 40% remains and topped up during next diastole

27
Q

What happens in ejection fraction below 40%?

A
  • sign of heart failure as its not pumping enough blood
28
Q

Describe process of heart contraction (vent contraction)

A
  1. Dep enters vent + is rapidly dis throughout them through cond through Bundle of His to Purkinje fibres
  2. Vent contraction
  3. Vent rep
  4. Vent relaxation - so can be filled during diastole
29
Q

Describe cardiac cond pathways Purkinjie fibres, AVN + endo + epicardium

A
  • Dispersion via Bundle of His, L + R bundle branches + Purkinje fibres to vent mass (4m/sec)
  • Cond via AVN (0.05m/sec) - slow - delay to allow atria to help fill vent with blood
  • Finally from endocardium to epicardium (0.3m/sec)
30
Q

Describe Phase 3 of cardiac cycle

A
  • When P in vent exceeds that in pul artery + aorta, pul + aortic valves open.
  • Vent begin to eject blood rapidly due to build up of P into lungs from R side + into aorta from L side
31
Q

Describe Phase 4 of cardiac cycle

A
  • As action pot ends, contraction becomes less forceful and ejection slows.
  • P peaks in aorta ~ 120 (LV) + 20 (RV) mmHg in pul artery.
  • Ejection stops when pul + aortic valves close as P in pul artery + aorta exceeds that in RV + LV.
32
Q

What is ESV?

A

vol at end of ejection (50ml)

33
Q

What is cardiac output?

A
  • amount of blood heart pumping out in a min
  • ~5 l/min at HR of ~70bpm
  • ranges dep on age, size etc
34
Q

Describe what happens in Phase 5 of cardiac cycle

A
  • isovol vent relaxation

- vent relax rapidly as P dec within them

35
Q

Describe what happens in Phase 6 of cardiac cycle

A
  • rapid vent filling
  • as P in vent falls below P in atria, T + M valves open
  • vent begin to suck blood from venae cavae + pul veins via relaxed atria
36
Q

Describe what happens in Phase 7 of cardiac cycle

A
  • red vent filling

- as vent relax completely, refilling progressively slows

37
Q

Where is most Ca2+ found?

A

T-tubules

38
Q

Briefly describe Ca2+ induced-Ca2+ release?

A
  • v. narrow space between SR + T-tubules gets large + rapid inc in Ca2+
  • opens Ca2+ channels on SR
  • Ca2+ released causes inc Ca2+ in cardiac cells
39
Q

What happens after CICR and how is Ca2+ cleared?

A
  • Ca2+ binds to troponin - form cross-bridge cycling
  • Ca2+ channels close
  • Ca2+ pumped through Na+/Ca2+ exchanger out of cell + ATP pumps on mem
  • clears Ca2+ from cells + goes back to resting level
40
Q

How much blood do vent eject?

A

~ 70ml

PPoS (11 decks)

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