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205 > Lecture 18- cardiovascular foundations I > Flashcards

Lecture 18- cardiovascular foundations I Flashcards

1
Q

99% of the cardiac muscle cells are

A

force-producing

myocardial cells or myocytes

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2
Q

the force producing cells are which muscle fibers?

A

striated muscle fibers

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3
Q

what is the other 1% of cardiac muscle cells?

A

autorhythmic (pacemaker) cells

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4
Q

what do pacemaker cells do?

A

generate spontaneous, rhythmic APs
- the signal for myocyte contraction

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5
Q

do pacemaker cells contribute to the contractile force?

A

very few contractile fibers

no organized sarcomeres

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5
Q

Can both types of cells generate action potentials?

A

yes!!

myocytes and pacemaker cells can generate APs

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6
Q

Autorhythmic cells: 2 characteristics of AP and contraction

A

spontaneously generate APs

do not contribute significantly to the contractile force of the heart

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7
Q

Contractile cells (striated muscle cells): 2 characteristics of AP and contraction

A

generate APs when depolarized

source of contraction force of the heart muscle

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8
Q

Cardiac myocytes: shape and what do they contain?

A

irregularly shaped striated muscle fibers with sarcomeres

-contain actin and myosin
-cross-bridge cycling mirrors skeletal muslce cross-bridge cycling

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9
Q

Cardiac myocytes: how are they connected?

A

connected in series by intercalated disks which contain

  • desmosomes: physical coupling, allows force to be transferred to neighbours
  • gap junctions: electrical coupling
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10
Q

What are 5 differences between cardiac vs skeletal muscle fibers?

A

cardiac:

  1. smaller and have 1-2 nuclei per fiber
  2. irregular, branching cells connected by intercalated disks
  3. T tubules are larger
  4. SR is smaller
  5. mitochondria occupy 1/3 of cell volume
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11
Q

Excitation-contraction coupling in cardiac myocytes: describe the 7 steps

A
  1. action potential enters from adjacent cell
  2. voltage-gated Ca2+ channels open. Ca2+ enters cell
  3. Ca2+ induces Ca2+ release through ryanodine receptor-channels (RyR)
  4. local release causes Ca2+ spark
  5. summed Ca2+ sparks to create a Ca2+ signal
  6. Ca2+ ions bind to troponin to initiate contraction
  7. relaxation occurs when Ca2+ unbinds from troponin
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12
Q

How does Ca2+ induce Ca2+ release through RyR?

A

Ca2+ binds to SR ryanodine receptor-channels (RyR) which triggers channel opening

Calcium-induced calcium release (CICR)

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13
Q

Where is the the summed Ca2+ signal from?

A

90% from SR and 10% from ECF

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14
Q

Mechanism of myocyte relaxation

A
  1. Ca2+ is pumped back into the SR for storage
  2. Ca2+ is exchanged with Na+ by the NCX antiporter
  3. Na+ gradient is maintained by the Na+-K+-ATPase
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15
Q

NCX antiporter=

A

Na+ Ca2+ exchanger

16
Q

SERCA

A

SR Ca2+ ATPase

17
Q

cardiovascular system transport

A

the arteries take blood away from the heart

the veins bring blood back to the heart

18
Q

where is the heart located?

A

on the ventral side of the thoracic cavity
sandwiched between the lungs

19
Q

What is the heart composed of?

A

myocardium (cardiac muscle cells).

there are myocardial cells of the atria and ventricles.

20
Q

4 major blood vessels

A
  1. vena cava (superior and inferior)
  2. pulmonary arteries
  3. pulmonary veins
  4. aorta
21
Q

4 chambers of the heart

A

1,2. right atria and ventricle
3,4. left atria and ventricle

22
Q

4 valves of the heart

A
  1. tricuspid valve (RA and RV)
  2. pulmonary valve (RV to pulmonary artery)
  3. bicuspid (or mitral) valve (LA to LV)
  4. aortic valve (LV to aorta)
23
Q

what do valves do?

A

Valves isolate chambers and ensure unidirectional flow!

–> Atrioventricular valves (AV) between atria and ventricles

–> Semilunar valves between ventricles and arteries

24
Q

Describe a ventricular contraction in terms of valves

A

AV valves close
semilunar valves open

25
Q

how does blood flow in the heart?

A

veins –> atria –> ventricles –> arteries

happens simultaneously on both sides of the heart

26
Q

Describe ventricular relaxation in terms of valves

A

AV valves open
semilunar valves close

27
Q

What do AV valve flaps have to provide stability and prevent backflow?

A

chordae tendinae (attached to papillary muscles)

28
Q

what do semilunar valves have to prevent backflow?

A

they are cup shaped!!
they don’t require tendons to prevent backflow

205 (27 decks)

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