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Body Systems > Week 7 - Circulation Of Blood / Cardiac Output > Flashcards

Week 7 - Circulation Of Blood / Cardiac Output Flashcards

1
Q

What is the function of the C/V (cardiovascular) system?

A
  • maintain an adaptable supply of blood to tissues in order to supply nutrients + signalling molecules and remove waste products
  • achieved through generating pressure differentials across tissues to enable capillary exchange
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2
Q

What are some of the components of the C/V system?

A
  • heart
  • brain
  • adrenal glands
  • kidney
  • blood vessels
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3
Q

What two factors is the flow (F) of blood from A to B determined by?

A
  • pressure difference between A and B (deltaP)
  • resistance to flow (R)
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4
Q

What are some factors affecting vascular resistance?

A
  • vessel length (L) - internal SA and flow are inversely proportional
  • blood viscosity (n) - higher viscosity = higher resistance
  • vessel radius (r) - flow proportional to r^4
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5
Q

What is Darcy’s Law?

A

Flow (F) = ΔP/ R

ΔP = pressure difference
R = resistance to flow

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6
Q

What is the Hagen-Poiseulle formula?

A

F = (ΔP x πr^4) / 8Ln

  • F = flow
  • P = pressure
  • r = resistance
  • n = blood viscosity
  • L = vessel length
  • r = vessel radius
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7
Q

Which side of the heart generates more pressure?

A
  • left side generates more pressure - pumps blood all around body via systemic circuit
  • right side generates less pressure - pumps blood to lungs via pulmonary circuit
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8
Q

Outline the cardiac conduction system

A
  • impulse generated at sino-atrial node
  • impulse carried to atrioventricular node (atrial contraction occurs)
  • impulse carried to bundle of His
  • impulse is carried via the purkinje fibres to the ventricular myocardium (ventricular contraction)
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9
Q

What does the P wave on an ECG denote?

A

Atrial contraction
(Atrial depolarisation)

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10
Q

what does the QRS complex denote on an ECG?

A
  • ventricular contraction (depolarisation)
  • atrial relaxation + repolarisation also occurs but is masked by larger ventricular electrical events
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11
Q

What does the T wave on an ECG denote?

A
  • ventricular relaxation (repolarisation)
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12
Q

What is cardiac output?

A

Volume of blood ejected by each ventricle per minute

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13
Q

What is heart rate?

A

Number of heartbeats per minute

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14
Q

What is stroke volume?

A

Volume of blood ejected by each ventricle per beat

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15
Q

How is cardiac output calculated?

A

Cardiac output (CO) = Heart rate (HR) X Stroke Volume (SV)

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16
Q

what factors affect heart rate?

A
  • autonomic innervation
  • hormones
17
Q

What factors affect stroke volume?

A

Preload
- filling time
Contractility
- autonomic innervation
- hormones
Afterload
- vascular tone

18
Q

What 3 things occur to decrease heart rate?

A
  • activation of cardioinhibitory centre in medulla oblongata
  • impulses along vagus nerve
  • acetylcholine release
19
Q

What 3 things occur to increase heart rate?

A
  • activation of cardioacceleratory centre in medulla oblongata
  • impulses along accelerator + sympathetic nerves
  • noradrenaline
20
Q

How can you calculate stroke volume?

A

End diastolic volume (EDV) - End systolic volume (ESV)

21
Q

What two things can occur to increase stroke volume?

A
  • increase end diastolic volume (EDV)
  • decrease end systolic volume (ESV)

Vice versa for decreasing stroke volume

22
Q

What is preload?

A

The degree to which ventricular muscle cells are stretched at the end of diastole

23
Q

What is contractility?

A

The force produced by ventricular muscle cells during systole at a given preload

24
Q

What is afterload?

A

The force the ventricle needs to overcome to open the semilunar valve + eject blood

25
Q

What is the Frank-Starling law?

A

The force developed in a muscle fibre is dependent on the extent it is stretched

26
Q

What are some factors affecting venous return & preload?

A
  • posture - blood pools in leg while standing (therefore venous return decreases)
  • skeletal muscle pump - skeletal muscle movement constricts veins - forces blood through veins (increases venous return)
  • respiratory pump - inspiration reduces intrathoracic pressure whilst increasing intraabdominal pressure (increases venous return)
27
Q

What happens if Venous return is increased?

A
  • preload is increased
  • end diastolic volume (EDV) is increased
  • therefore a higher stroke volume is attained, and a greater cardiac output occurs.
28
Q

What is the effect of the sympathetic nervous system on contractility?

A
  • SNS increases force of contraction and velocity of conduction
  • also allows longer for diastole so increased filling of blood in the heart can occur
29
Q

What is the effect of afterload on stroke volume and cardiac output?

A

Increased afterload reduces SV & CO

30
Q

How do vasodilation and vasoconstriction affect afterload?

A
  • vasoconstriction increases afterload
  • vasodilation decreases afterload

Body Systems (11 decks)

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