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ISAP (HUMB1002) > Heart > Flashcards

Heart Flashcards

1
Q

4 Function of the heart

A
  1. generate BP
  2. route for blood: pulmonary & systemic circulation
  3. one-way blood flow
  4. provide blood supply for metabolic needs
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2
Q

describe how heart gets its own blood supply

A

blood supply to myocardium

  • R&L coronary arteries @ ascending aorta
  • > large arteries travel in sulci on <3 surface, small branches penetrate myocardium
  • > cardiac veins -> coronary sinus (posterior <3) -> R atrium
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3
Q

3 Purpose of CT ring around 4 valves

A
  1. anchorage
  2. structural stability
  3. electrical insulation b/w atria & ventricles
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4
Q

2 Properties of cardiac muscle that allow it to function

A
  • functional synctium= very fast electrical conduction w/in muscle fibres
  • myocardinal fibres very aerobic w/ many mitochondria, oxidise FA & glucose for energy
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5
Q

location of <3

A

mediastinum

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6
Q

coverings of heart

A
  • Fibrous pericardium: anchor & protection

- Serous pericardium: parietal + viseral = pericardial cavity

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7
Q

wall layers of <3

A
  • epicardium (/visceral pericardium)
  • myocardium (cardiac muscle)
  • endocardium (simple squamous)
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8
Q

What is the cardiac cycle?

A

One complete <3 beat = atrial sys & dias + ventricular sys & dias. Note: depolarise => contract, repolarise => relax

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9
Q

Describe depolarisation sequence (7 steps)

A
  1. SA node (cause auto rhythmicity)
  2. Atrial muscle
  3. AV node
  4. Atrioventricular bundle
  5. R&L bundle branches
  6. Purkinje fibres
  7. Ventricular muscles
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10
Q

Does the pacemaker have a stable RMP?

A

No because after repolarisation it SLOWLY DEPOLARISE again

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11
Q

Describe AP of cardiac muscle fibres

A

AP initiated by adjacent current flow & fibres remain depolarised&raquo_space; prevent premature re-excitation & tetany (spasm)
* myocardial fibres stable RMP = return to normal RMP

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12
Q

What is an ECG & function

A

Electrocardiogram: sum of all electrical events during cardiac cycle measured on surface of body.
» determine heart health, identify heart attack

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13
Q

waves of an ECG

A
  1. P: atrial depol
  2. QRS: ventricular depol (behind it atrial repol)
  3. T: ventricular repol
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14
Q

Describe mechanical phases of cardiac cycle

A
  1. Atrial depol -> atrial sys: pushes out 20% blood remaining
  2. Ventricular depol -> ventricular sys: isovolumetric ventricular contraction = hi pressure (AV valves close & semilunar valves open) -> ventricular ejection
  3. Ventricular repol. followed by ventricular dias: semilunar valve close -> isovolumetric ventricular relaxation -> AV valves open = rapid passive ventricular filling (80%)
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15
Q

How Neural factor affects <3 rate?

A
  • note: SA & AV innervated by para&sympathetic nerves from cardiovascular centre in medulla oblongata
  • Para (via VAGUS): acetylcholine= slow <3 rate ,innervate SA & AV nodes.
  • Symp (via thoracic spinal cord): noradrenaline = increase <3 rate, innervate SA node
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16
Q

Other factors (except neural) that affect <3 rate

A
  • Hormones: nor&adrenaline, thyroid hormones
  • Tb
  • drugs
  • sleep
17
Q

3 factors that affect SV (stroke volume)

A
  1. preload (intrinsic effect): force on ventricular muscle @ EDV & venous return
  2. contractility (extrinsic effect): inotropic state of heart- strength of ventricular contraction (by [Ca2+])
  3. afterload: force developed by ventricles -> eject blood in arteries (RV is lo, LV is hi)
18
Q

Cardiac volumes (3)

A
  • End diastolic vol. (EDV): vol of ventricle @ end of filling (120-130mL)
  • End systolic vol. (ESV): vol of ventricle @ end of emptying (50-60mL)
  • stroke vol. (SV): vol blood ejected per beat (70mL). SV = EDV - ESV
19
Q

What is Starling’s law of the heart? (type of effect)

A

Relationship b/w stretch of ventricles as blood fills it and the contraction required to eject blood out. More filling = more force to empty (intrinsic effect)

20
Q

What is extrinsic effect (affects contractility)?

A

Para/sympathetic NS involved in <3 function.

  • Contractility increase= Sympathetic NS innervate ventricular muscle -> nor+adrenaline act on beta 1 receptors (+ve inotropic effect)
  • Contractility decrease= decrease stimulation -> decrease nor+adrenaline and beta blockers

ISAP (HUMB1002) (12 decks)

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