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Cardiovascular > 5. Physiology III - Blood Pressure and Cardiac Cycle > Flashcards

5. Physiology III - Blood Pressure and Cardiac Cycle Flashcards

1
Q

HEART RHYMTH is normally DETERMINED by PACEMAKER CELLS in the ….

A

SINO-ATRIAL NODE (SAN)

  • which DEPOLARISE SPONTANEOUSLY
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2
Q

CARDIAC ELECTRICAL ACTIVITY is the result of the MOVEMENT of… across the cell membrane

A

IONS: Na+, K+, Ca2+

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3
Q

how is the RESTING MEMBRANE POTENTIAL / PHASE 4 in the SA NODE ACTION POTENTIALS and why

A

UPSLOPING, NOT flat
around -60 mV (less polarised than av node)

  • GRADUAL RISE due to
    gradual REDUCTION in OUTWARD K+ current
    & INCREASE in INWARD current of Na+ and Ca2+
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4
Q

How are the ION CHANNELS in PHASES 0,2,3 of SAN ACTION POTENTIALS

A

0: Ca2+ channels open, LARGE Ca2+ INFLUX once threshold reached (slower rise)

(1: initial repolarisation)

2: (plateau as Ca2+ channels and K+ channels open) Ca+ channels start to close

3: Repolarisation as K+ EFFLUX (Ca2+ channels are closed, K+ channels open)

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5
Q

RESTING POTENTIAL in SAN

A

around -60mV

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6
Q

RESTING POTENTIAL in AV NODE

A

-85 / -90 mV

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7
Q

NON-PACEMAKER ACTION POTENTIALS (ie AV NODE) PHASES:

A

0: DEPOLARISATION as Na+ channels OPEN (FAST)

1: INITIAL REPOLARISATION (Na+ channels CLOSE, some K+ EFFLUX)

2: PLATEAU as Ca2+ channels open, Ca2+ INFLUX (and K+ efflux) (SLOW)

3: REPOLARISATION (Ca2+ channels CLOSE) K+ EFFLUX

  1. RESTING POTENTIAL (FLAT)
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8
Q

ECG is a … MEASUREMENT

A

VECTOR

  • measures MAGNITUDE of Depolarisation and DIRECTION
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9
Q

CHANGES in the ECG are used to DIAGNOSE..

A

HEART ARRYTHMIAS (ABNORMAL RHYTHM)

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10
Q

ECG
P WAVE:
QRS:
T WAVE:

A

P: ATRIA DEPOLARISE

QRS: VENTRICLES DEPOLARISE

T: VENTRICLES REPOLARISE

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11
Q

how does the WAVE OF DEPOLARISATION SPREAD starting from SA NODE (PACEMAKER) FIRING

A
  1. ATRIA - DEPOLARISE
  2. AV NODE - DELAYS
  3. BUNDLE of HIS
  4. LEFT & RIGHT BUNDLE BRANCHES
  5. PURKINJE FIBRES
  6. VENTRICLES - DEPOLARISE (contract)
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12
Q

name of structure that Connects Right and Left ATRIA and allows Impulses to pass from right to left (from SAN) for simultaneous contraction

A

BACHMANN’S BUNDLE

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13
Q

define CARDIAC CYCLE
the sequence of….

A

sequence of ONE HEART BEAT ENDING to the BEGINNING OF ANOTHER

  • Cardiac Diastole (whole heart relaxed)
  • Atrial Systole (contract)
  • Ventricular Systole (contract)
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14
Q

PHASES of CARDIAC CYCLE

A
  1. ATRIAL SYSTOLE
  2. ISOVOLUMETRIC VENTRICULAR CONTRACTION
    no change in volume as valves are still shut
  3. RAPID VENTRICULAR EJECTION
    ventricular pressure overcomes pulmonary trunk or aorta pressure, so valves open
  4. ISOVOLUMETRIC VENTRICULAR RELAXATION
    while blood fills atria. no change in volume as atrioventricular valves shut
  5. RAPID VENTRICULAR FILLING
    atrial pressure overcomes ventricular pressure so av valves open, increase in volume as ventricles fill
  6. atrial systole
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15
Q

what happens in CARDIAC CYCLE AFTER VENTRICULAR FILLING

A

ATRIAL SYSTOLE - atria CONTRACT

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16
Q

in a PHONOCARDIOGRAM what are the 1st, 2nd and 3rd SOUNDS picked up

A

1st: MITRAL VALVE CLOSING (bicuspid)

2nd: AORTIC VALVE CLOSING

3rd: Ventricular filling (rapid inflow of blood) during diastole

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17
Q

what is CARDIAC OUTPUT and how is it CALCULATED

A

VOLUME OF BLOOD PUMPED EACH MINUTE

CO = STROKE VOLUME X HEART RATE

in L/MIN

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18
Q

STOKE VOLUME (blood pumped out of left ventricle in one beat) is determined by which 3 FACTORS

A
  • PRELOAD
    volume of blood INTO VENTRICLE (that ventricle is able to pump)
  • CONTRACTILITY
    force that the muscle can create
  • OUTLOAD
    the arterial pressure (pressure of blood in aorta) that the ventricle must overcome to open the valve
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19
Q

does the LEFT VENTRICLE EMPTY COMPLETELY during SYSTOLE

A

NO

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20
Q

CALCULATION for STROKE VOLUME (amount of blood transferred from Left ventricle to arterial system in systole)

A

SV =
END DIASTOLIC VOLUME (EDV) - END SYSTOLIC VOLUME (ESV)

EDV - total volume of blood IN ventricle at end of diastole (dependent on PRELOAD)

ESV - volume of blood REMAINING in ventricle at the end of systole (dependent on AFTERLOAD)

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21
Q

what is the STROKE VOLUME in a HEALTHY PERSON

A

> 60 ml

(approx 80-90ml)

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22
Q

what is END DIASTOLIC VOLUME (EDV) and what is the approx amount

A

total VOLUME of BLOOD IN VENTRICLE at the END OF DIASTOLE (filling from aorta)

  • dependent on PRELOAD

approx 140 ml

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23
Q

what is END SYSTOLIC VOLUME (ESV) and what is the approx amount

A

VOLUME of BLOOD REMAINING IN VENTRICLE at the END of SYSTOLE (after contraction, and expelling into aorta)

  • dependent on AFTERLOAD

approx 50ml

24
Q

what is EJECTION FRACTION and what is the normal %

A

STROKE VOLUME / END DIASTOLIC VOLUME

(proportion of blood in the ventricle that is pumped out)

normally 55-75 %

25
Q

EJECTION FRACTION (EF) is an important measurement of…

A

CARDIAC EFFICIENCY

used to asses cardiac status in patients with heart failure

26
Q

BLOOD PRESSURE is a MEASUREMENT of…

A

the FORCE AGAINST THE WALLS of the ARTERIES
as the heart pumps blood throughout the body

  • measured in mmHg
27
Q

what is SYSTOLIC PRESSURE (P systolic)

A

the MAXIMAL AORTIC PRESSURE following EJECTION from ventricle

(pressure in aorta after blood pumped out of ventricle)

28
Q

what is DIASTOLIC PRESSURE (P diastolic)

A

the LOWEST AORTIC PRESSURE which occurs JUST BEFORE VENTRICLE EJECTS BLOOD INTO AORTA

as the left ventricle is relaxing and filling

29
Q

what is NORMAL SYSTOLIC PRESSURE and NORMAL DIASTOLIC PRESSURE

A

p systolic: 120 mmHg
p diastolic: 80 mmHg

120/80

30
Q

what is the DIFFERENCE between the SYSTOLIC and DIASTOLIC PRESSURE called and what is it normally

A

AORTIC PULSE PRESSURE

ranges between 40 and 50 mmHg

31
Q

how do you calculate the MEAN AORTIC/ARTERIAL PRESSURE (MAP) - the average pressure (geometric mean) during the whole cardiac cycle

A

MAP =
CARDIAC OUTPUT X SYSTEMIC VASCULAR RESISTANCE (SVR)

  • OHM’S LAW
    based upon relationship between flow, pressure, resistance
32
Q

MEAN ARTERIAL PRESSURE (MAP) is an estimate of LEFT VENTRICULAR PRESSURE and can be approximated by which EQUATION
MAP =

A

MAP = DIASTOLIC + 1/3 (AORTIC) PULSE PRESSURE

(as heart spends 2/3rd time in diastole)

= 80 + 1/3 (120-80)
= 93 mmHg

33
Q

what BP is the cut off for HYPERTENSION (HIGH BP)

A

140/90 and HIGHER

(varies according to age)

34
Q

what provides an INDIRECT MEASURE of CENTRAL VENOUS PRESSURE (CVP)

A

JUGULAR VENOUS PRESSURE (JVP)

aka jugular venous pulse

  • from visualization of the internal jugular vein, using ultrasound probe
  • patient placed at 45 degree angle
35
Q

why does the INTERNAL JUGULAR VEIN act as a column for the blood in the right atrium

A

CONNECTS DIRECTLY to the RIGHT ATRIUM
WITHOUT any intervening VALVES

36
Q

CARDIOVASCULAR SYSTEM is under AUTONOMIC CONTROL
SYMPATHETIC control acts on which RECEPTORS

A
  • mostly cardiac BETA-1
  • sometimes ALPHA-1 adrenoreceptors
37
Q

CARDIOVASCULAR SYSTEM is under AUTONOMIC CONTROL
PARASYMPATHETIC control acts on which RECEPTORS

A

MUSCARINIC RECEPTORS
(M2 & M3)

38
Q

Which NERVOUS SYSTEM controls ALL COMPONENTS of the HEART (SAN,AVN, VENTRICLES)

A

SYMPATHETIC

  • via BETA-1 RECEPTORS
39
Q

which does the PARASYMPATHETIC NERVOUS SYSTEM CONTROL in cardiac function

A

SA NODE & AV NODE

40
Q

SYMPATHETIC NERVOUS SYSTEM controls heart by RELEASING…

A

NORADRENALINE

41
Q

via Noradrenaline and Beta-1 Receptors, what is the affect of SYMPATHETIC NERVOUS SYSTEM

A

INCREASE HEART RATE (positive chronotropic effect)
and
INCREASE Cardiac CONTRACTILITY (force) (positive inotropic effect)

(fight or flight)

42
Q

what does SYMPATHETIC NERVOUS SYSTEM cause by ACTIVATING ALPHA-1 RECEPTORS

A

VASOCONSTRICTION

43
Q

PARASYMPATHETIC NERVOUS SYSTEM controls SAN and AVN by RELEASING…

A

ACETYLCHOLINE (Ach)

44
Q

EFFECT of PARASYMPATHETIC NERVOUS SYSTEM via release of Ach and Muscarinic receptors..

A

DECREASES HEART RATE (Negative chronotropic effect)

PROLONGS DELAY at AV NODE (slowing down rate of transmission)

  • VASODILATION

(little effect on contractility)
(rest and digest)

45
Q

what are chronotropic effects

A

effects on Heart Rate

46
Q

what are inotropic effects

A

effects on Contractility / Force

47
Q

what is dromotropy

A

rate of Electrical Impulses

48
Q

BP =

A

CO X SVR (systemic vascular resistance)

SVR aka PR (peripheral resistance)
(BP = CO X PR)

49
Q

to Maintain normal BP, CO and PR/SVR are controlled by 2 overlapping mechanisms:

A
  • SHORT-TERM BP REGULATION (Neural mechanisms)
  • LONG-TERM BP REGULATION (Endocrine/Hormonal ie RAS system)
50
Q

example of LONG-TERM BP REGULATION

A

RAAS SYSTEM

  • angiotensin II is a potent VASOCONSTRICTOR
  • angiotensin II also directly acts on kidney to INCREASE SODIUM REABSORPTION in the pct
  • ALDOSTERONE release for NaCl and H2O retention at dct (increase expression of epithelial sodium channels)
  • ADH for H2O REABSORPTION
51
Q

RENIN is released from juxtaglomerular apparatus in response to…

A
  • SYMPATHETIC STIMULATION (juxtaglomerular Beta1 receptors)
  • REDUCED NaCl delivery to the DCT
  • DECREASED BLOOD FLOW to the kidney (low CO)
52
Q

SHORT-TERM REGULATION of BP is controlled by the AUTONOMIC NERVOUS SYSTEM.
CHANGES in BLOOD PRESSURE are detected by? where?

A

BARORECEPTORS

in AORTIC ARCH and CAROTID SINUS

53
Q

SHORT-TERM REGULATION of BP is controlled by the AUTONOMIC NERVOUS SYSTEM.

changes in BP, detected by BARORECEPTORS in AORTIC ARCH and CAROTID SINUS, is RELAYED TO…

A

the CARDIOREGULATORY CENTRE in the MEDULLA OBLONGATA

54
Q

SHORT-TERM REGULATION of BP is controlled by the AUTONOMIC NERVOUS SYSTEM.

CHANGES in Blood PH, O2 and CO2 Levels are DETECTED by…

A

CHEMORECEPTORS

(in aortic arch and carotid sinus)

55
Q

INCREASED ARTERIAL PRESSURE STRETCHES the wall of the blood vessel, triggering BARORECEPTORS which feedback to the ANS to REDUCE HEART RATE, CARDIAC CONTRACTILITY and CARDIAC OUTPUT

via which nervous system FIBRES of which NERVE?

A

EFFERENT PARASYMPATHETIC FIBRES

  • VAGUS NERVE
56
Q

DECREASED ARTERIAL PRESSURE detected by BARORECEPTORS triggers which NERVOUS SYSTEM RESPONSE to INCREASE HEART RATE, CONTRACTILITY and CARDIAC OUTPUT and also VASOCONSTRICTION

A

SYMPATHETIC response

  • via CARDIAC BETA-1 RECEPTORS
    (noradrenaline)
    & ALPHA-1 receptors for vasoconstriction
57
Q

how does VASOCONSTRICTION (sympathetic) INCREASE BLOOD PRESSURE

A

via ALPHA-1 RECEPTORS

INCREASES PERIPHERAL RESISTANCE (PR) (aka SVR)

BP = CO X PR

Cardiovascular (16 decks)

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