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Body Systems > 13 Cardiac output II > Flashcards

13 Cardiac output II Flashcards

1
Q

What does venous return effect?

A

Atrial filling

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2
Q

What effects stroke volume?

A
  • ventricular filling rate

- EDV (large causes muscle fibres to stretch more, making them work harder and get stronger)

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3
Q

Starlings Law:

A

What goes into the heart, must come out of the heart

-the energy of the contraction is proportional to the initial length of the muscle fibre

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4
Q

What are the key factors in venous return?

A
  • muscular pumps
  • respiratory pumps
  • posture
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5
Q

what does the preload volume effect?

A

EDV directly

ESV indirectly

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6
Q

How does posture effect venous return?

A

standing causes pooling in the feet and less venous return

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7
Q

How do muscle pumps facilitate venous return?

A

Skeletal muscle contractions constrict venous return and since valves prevents back flow the blood has to go up

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8
Q

How do respiratory pumps facilitate venous return?

A
  • when you breathe in diaphragm flattens increasing abdominal pressure and decreasing thoracic pressure
  • this causes blood to move up from the abdomen into the thorax towards the heart
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9
Q

What are the filling times?

A

times taken for atria and ventricle to contract - directly linked to contractility

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10
Q

Contractility

A

contractile ability of cardiac muscle at a given preload volume

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11
Q

What is an inotropic effect?

A

effects the contractility of the heart (force of contraction)

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12
Q

what does a positive inotropic do?

A

increases contractility and therefore stroke volume

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13
Q

How do you cause an increase in contractility?

A

Increase the levels of intracellular calcium (from intracellular stores) as this increases the binding between the actin and myosin filaments

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14
Q

What has positive inotropic effects?

A

SNS and adrenaline

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15
Q

How does the PNS effect the heart?

A

through the vaygus nerve which effects atria because it doesn’t reach the ventricles.
-it slows HR and decreases contractility and so stroke volume

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16
Q

What effects the filling times of the heart?

A

HR and contractility

17
Q

What changes are there in diastole and systole times when the heart rate speeds up?

A
  • with no SNS systole would be the same length, only diastole would be effected so the filling time would reduce reducing SV and CO
  • SNS slightly slows down diastole and quickens systole allowing the atria/ventricles time to fill
18
Q

What is the afterload?

A

the (aortic) pressure against which the heart has to work to eject blood from the ventricles. this is greater if the vessels are constricted.

19
Q

What effects the afterload?

A

vasoconstriction (blood vessel tone)

blood pressure

20
Q

What effects cardiac output?

A

Blood pressure

21
Q

What determines blood pressure?

A

CO x total resistance of peripheral vessels
CO (HR and SV)
TPR (arterial radius)

22
Q

How do we regulate blood pressure short term?

A

HR
Vasoconstriction and dilation
-regulated by baroreceptors (neural)
-and by chemoreceptors (o2 co2 h+)

23
Q

How do we regulate blood pressure long term (hrs and days)

A

-changing extracellular fluid volume
-kidney NA/Water homeostasis
-Hormones (ADH, aldosterone, atrial natriuretic peptide)
ADH + ALD increased the sodium and water conc in the blood
ANP released from the atria reduces it

24
Q

What is too low blood pressure called?

A

hypotension

25
Q

what is too high blood pressure called?

A

hypertension

26
Q

Where are baroreceptors for blood located?

A
  • in walls of blood vessels
  • aorta
  • carotid artery
27
Q

Where are the chemosensors located?

A

carotid body and in the CNS in the medulla oblongata

28
Q

How do baroreceptors work?

A

They fire more as blood pressure increases. fail to respond 40mmHg or less blood pressure.
-respond more to pulsatile changes in blood pressure than smooth changes

29
Q

Why are baroreceptors located in the aortic arch?

A

so they can detect every beat of the heart

30
Q

What do the peripheral chemoreceptors (heart) detect?

A

-increase in O2
stimulates increase in respiratory rate
-Decrease in CO2 or increase in pH
stimulates vasomotor centre and cardioacceleratory centre

31
Q

What do the central chemosensors detect? (in the cardiovascular system)

A

Not O2, just CO2 and pH.

  • cause vasodilation of cerebral vessels and promote blood flow to the brain
  • effect respiratory function

Body Systems (21 decks)

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