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Anatomy and physiology > heart physiology > Flashcards

heart physiology Flashcards

1
Q

blood flow around the heart

A

from body to lung:
- vena cava into right atrium
- tricuspid valve open to let deoxygenated blood into right ventricle
- when r ventricle full and ready to contract, tricuspid closes and pulmonary semilunar valve opens so blood flow into pulmonary artery

from lung to body:
- pulmonary vein into left atrium
- bicuspid valve open to let oxygenated blood into left ventricle
- when l ventricle full and ready to contact, bicuspid closes and aortic valve opens to let blood flow into aorta

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2
Q

fossa ovalis

A
  • shallow depression in the right atrium
  • remnant of foramen ovale (fetal circulation)
  • which allow blood to flow from r atrium to l atrium, bypassing the units to reach baby
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3
Q

coronary sinus

A
  • located on posterior side of heart, within the AV sulcus
  • drains blood from the coronary veins (drains deoxygenated blood from myocardium after its supplied heart muscle with nutrient and oxygen)
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4
Q

chordae tendineae

A

“heart strings”
- prevent AV valves from inverting
- originate on the cusps of the valves and insert onto the papillary muscle (on inner walls of the ventricles)

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5
Q

papillary muscles

A
  • anchor the chordae tendineae
  • 3 on right
  • 2 on left
  • prevent inversion
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6
Q

inter ventricular septum

A
  • thick muscular wall
  • needs to be able to withstand pressure of the blood
  • separates the ventricles and prevent blood mixing
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7
Q

diastolic phase

A

ventricle relax
fill with blood

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8
Q

valves of the heart

A

prevent backflow of blood
- open and close in response to pressure changes

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9
Q

coronary artery circulation

A

heart muscle supplied with blood from left and right c arteries
- arise for aortic sinuses within aorta
- located on posterior side of heart within AV sulcus
- provides oxygen and nutrient to myocardium

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10
Q

variation in coronary artery circulation

A

larger left than right
- dominant c artery gives rise to the posterior interventicular branch

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11
Q

coronary venous circulation

A

blood drains into right atrium via coronary sinus

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12
Q

layers of the heart wall

A

endocardium
myocardium
epicardium

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13
Q

endocardium

A
  • inner layer
  • simple squamous endothelium on thin layer of connective tissue
  • smooth lining for chambers of heart
  • SURROUND INDIVIDUAL CHAMBERS
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14
Q

myocardium

A
  • middle layer
  • cardiac muscle tissue
  • bundles organised diagonally around heart
  • generates pumping action of heart
  • SURROUNDS ENTIRE HEART
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15
Q

epicarium

A
  • outer layer

MADE UP OF:
- areolar connective tissue
- mesothelium

  • gives smooth surface to outside of heart
  • contains blood vessels
  • adheres tightly to
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16
Q

pericardium

A

triple layered sac- surrounds and protects the heart

fibrous pericardium: (OUTER)
- tough inelastic, dense irregular connective tissue
- protects heart ans prevent overstretch
- anchor heart in medaistnim

parietal pericardium: MIDDLE)
- fused to fibrous pericardium

visceral layer (INNER):
- epicardium

PERICARDIAL FLUID BETWEEN PAR AND VIS:
- reduce friction as heart beat

17
Q

skeletal and cardiac muscle

A

S:
- under voluntary control

C:
- striated appearance
- under involuntary control
- branching structure
- cells are shorter in S= MORE MITOCHONDAIR
- one nucle per cell

18
Q

electrical activity of the heart

A
  • doesn’t require external stimuli’s for cardiomyocyte contraction
  • AUTORHYTHMIC CELLS:
  • auto generate action poteion that triggers heart contraction
  • specialised cardiomyocytes
  • found in SA (sinoatrial) node
19
Q

SA node action potential

A
  • no stable resting potential
  • repeatedly depolarise to threshold required to trigger action pot
20
Q

what and where is the SA node

A

right atrium
primary pace maker

21
Q

the conducting system

A
  1. SA node activity and atrial activation begins
  2. stimulus spreads across atrial surfaces and reaches AV node
  3. there is a 100 msec delay at the AV node. atrial contraction begins
  4. impulse travels down the interventricular septum within AV bundle and the bundle branches into the purkinje fibres via moderator band to the papillary muscles of th right ventricle
  5. impulse is distributed by purkinje fibres and relay throughout the ventriclar myocardium

ATRIAL contraction is done and VENTRCULAR begins

22
Q

cardiac muscle action potential

A
  • cardiomyocytes have different shape action potentials compared to skeletal muscle
  • longer action potential allows for prolonged contraction in coordinated fashion
  • refractory period between depolarisation and re polarisation where another action potential can’t be formed
  • give time for chambers to fill with blood
23
Q

excitation contraction coupling in cardiomyocytes

A
  1. action potential enters from adjacent cell
  2. L type voltage-gated calcium ions channel open and calcium ions enter the cell
  3. calcium from outside the cell binds to ryanodine receptor
  4. entry of ions trigger the release of ions from sarcoplasmic reticulum (most calcium ions comes from SR)
  5. calcium ions bind to troponin to initiate contraction
24
Q

conduction of cardiac action potential

A
  • cardiac muscle cells connected by intercalated discs
  • secured by desmosomes
  • linked by gap junctions
  • allow for transfer of ions between cells
  • local changes in currents
25
Q

mechanics of cardiac contraction

A

P reload
A fterload
C ontrctlity
E art rate

26
Q

cardiac output equation

A

CO= HR X SV
heart rate x stroke volume

27
Q

stroke volume

A
  • EDV-ESV
  • EDV= volume before contraction
  • ESV= volume after contraction
  • increase in blood coming back to heart (EDV) leads to increase in contractility
  • due to increased Ca ion release and sensitivity
28
Q

after load

A
  • the pressure in which the heart has to pump against to eject blood
  • higher the pressure in aorta= more force required by the heart (systemic circulation)
  • as afterload increase= cardiac output decreases
29
Q

contractility

A

the ability to contract the heart

to increase contractility you need positive ionotropic agents
- promote calcium ion influx or sensitivity during cardiac action potential
- sympathetic nervous stimulation of ventricular muscle fibres
- hormonal control

30
Q

eart rate

A

neuronal and endocrine regulation of SA node

increase HR: positive chronotropic factors (adrenaline and noradrenaline)

decrease HR: negative chronotrpic factors (acetylcholine)

sympathetic increases HR
parasympathetic decreases HR

Anatomy and physiology (26 decks)

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