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My LSS- CVS > CVS 11: Regulation of the cardiovascular system > Flashcards

CVS 11: Regulation of the cardiovascular system Flashcards

1
Q

How is the venous blood distributed?

A
  • Peripheral Venous tone
  • Gravity
  • Skeletal Muscle pump
  • Breathing
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2
Q

What feature of veins allows them to act as a storage vessel for blood?

A

Capacitance

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3
Q

What is central venous pressure and what does it indicate?

A
  • Mean pressure in the right atrium

- amount of blood flowing back to the heart

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4
Q

What does the amount of blood flowing back to the heart determine?

A

Strokoe volume (Starling’s Law)

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5
Q

What is determined by the constriction of veins?

A
  • Compliance

- Venous return

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6
Q

What does the constriction of arteries determine?

A
  • blood flow to the organs they serve
  • Mean arterial blood pressure
  • Patter of distribution of blood to organs
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7
Q

How is blood flow mainly changed and what are the relevant equations for this?

A

Mainly changed by altering radius
F= ∆P / R
R= 1/ R^4

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8
Q

What are the three different control mechanisms behind regulating flow?

A

1) Local Mechanisms- Intrinsic to smooth muscle/ closely related to it
2) Hormonal
3) Autonomic Nervous System- Innervates vessels to produce vasoconstriction/ dilation

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9
Q

Define autoregulation

A

The intrinsic capacity to compensate for changes in perfusion pressure by changing vascular resistance

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10
Q

What happens when blood pressure drops when you have auto regulation?

A

BP= CO x TPR
F= ∆P/ R
fall in BP=> fall in TPR=> rise in flow

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11
Q

What happens when blood pressure drops, in the absence of autoregulation?

A
  • Resistance stays basically the same. It increases slightly because of passive constriction as intravascular pressure drops
  • flow rate drops
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12
Q

What are the two theories for explaining the autoregulation mechanism

I DONT GET THIS?!?!

A
  1. Myogenic theory
    • pressure rises
    • smooth muscle fibres respond to stretch
    • muscle fibres contract to keep flow constant
  2. Metabolic theory
    • vessel supplying particular bed contract
    • flow to bed decreases
    • bed produces more metabolites
    • feeds back to vessels supplying the bed
    • causes vasodilation
    • increases flow to vascular bed, metabolites washed away
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13
Q

What other factor can change autoregulation and how?

A

INJURY

  • vessel injury –> platelets aggregate and release SEROTONIN
  • serotinin= vasoconstrictor
  • constricts injured vessel
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14
Q

Name some substances released by the endothelium which is involved in regulation blood flow

A
  1. Nitric oxide: vasodilation
  2. Prostacyclin and thromboxane A2: vasodilator and vasoconstrictor respectively
  3. Endothelins: vasoconstrictor
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15
Q

Name three groups of hormones involved in regulating blood flow

A
  1. Kinins
  2. Anti Natriuretic Peptide
  3. Circulating vasoconstrictors
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16
Q

Give an example of a kinin and explain how it regulates blood flow

A

BRADYKININ

  • interact with Renin- Angiotensin system
  • tend to relax smooth muscle
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17
Q

What is ANO and where is it secreted from?

A
  • Secreted from the cardiac atria as the atria stretch

- a circulating peptide which causes vasodilation

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18
Q

Name three circulating vasoconstrictors and where they’re secreted from

A
  • Vasopressin ADH- posterior pituitary
  • Angiotensin II- renal secretions
  • Noradrenaline- adrenal medulla
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19
Q

Describe the structure of parasympathetic nerves

A
  • Long preganglioic
  • Short postganglionic
  • ganglion right next to SAN
20
Q

What are the main functions of sympathetic and parasympathetic innervation?

A
  1. Sympathetic- controls FLOW

2. Parasympathetic- regulates HEART RATE

21
Q

Sympathetic nerve fibres innervate all vessels except…

A

capillaries

22
Q

Describe the distribution of sympathetic nerve fibres

A

MORE: kidney, gut, spleen and skin
FEWER: skeletal muscle and brain

23
Q

Why is there more sympathetic innervation to the kidney, gut, spleen and skin?

A

So that there is more potential to constrict the blood going to these places to divert this blood to the organs which need it more

24
Q

Describe how the concentrations of adrenaline affects its binding to certain receptors and its function

A
  1. Circulating adrenaline: binds to smooth muscle B2 adrenoreceptors –> vasodilation in some organs
  2. High concentrations: adrenaline binds to a adrenoreceptors –> overrides vasodilatory effects of B2 –> vasoconstriction
    * * constriction in blood vessels alpha 1- adrenoreceptor effect
25
Q

Where is the vasomotor centre located in the brain?

A

Bilaterally in the reticular substance of the medulla and in the lower third of the pons

26
Q

What does the vasomotor centre consist of?

A
  1. Vasoconstrictor area (pressor)
  2. Vasodilator centre (depressor)
  3. Cardioregulatory inhibitory area
27
Q

What does the lateral portion of the VMC control?

A

Heart activity by influencing:

  • heart rate
  • contractility
28
Q

What does the Medial portion of the VMC do?

A

Transmits signals via the vagus nerve to the heart

–> decreases Heart Rate

29
Q

What is the function of the VMC?

A

allows an anticipatory response to exercise

-> hr and ventilation rate go up slightly before exercise

30
Q

What sot of innervation do blood vessels receive and which neurotransmitter is involved?

A
  • receives sympathetic postganglionic innervation
  • noradrenaline
  • not much parasympathetic innervation
31
Q

What is the importance of the blood vessels being tonically active

A
  • at baseline have certain frequency of impulses= vasomotor tone
  • increase impulse-> constriction
  • decrease impulse -> dilation
32
Q

What innervates the heart and which neurotransmitters are involved?

A
  • Parasympathetic- decreases heart rate- acetylcholine

- sympathetic- increases heart rate - adrenaline and noradrenaline

33
Q

How do the neurotransmitters involved in controlling the heart rate work?

A

ACETYLCHOLINE: decreases gradient of pacemaker potential –> potential takes longer to reach threshold and fire
NORADRENALINE: increases the gradient of pacemaker potential –> potential takes reaches threshold quicker

34
Q

What is the resting heart rate? What is the heart rate with no innervation?

A

70 bpm

100 bpm

35
Q

How can force of contraction be increased?

A
  • Starling’s law

- increase sympathetic activity

36
Q

Explain how sympathetic activity increases the force of contraction

A
  • Noradrenaline binds to adrenoreceptors
  • this increases the amount of cAMP
  • cAMP activates PKA
  • PKA phosphorylates L-type calcium channels and the SR calcium release channels and SERCA
  • more calcium influx
  • more calcium taken into stores

NORADRENALINE ON B-1-receptros increases contraction

37
Q

How is stroke volume increased?

A 
EXTRINSIC: 
- Increase sympathetic activity
- Using plasma adrenaline
INTRINSIC:
- Starling's law- increase venous return which increases atrial pressure and the end-diastolic ventricular volume--> increased force of contraction
38
Q

How could you increase venous return to help increase stroke volume?

A

Increase RESPIRATORY MOVEMENT:

  • decreasing intrathoracic pressure
  • increases filling of the heart and EDV
39
Q

How is cardiac output increased during the fight or flight response?

A
  • increased respiratory movement
  • increased plasma adrenaline
  • increased sympathetic activity to the heart
40
Q

Where are baroreceptors found? what do they feedback back to?

A
  • Found in the aortic arch and carotid sinus
  • receptors in CAROTID BODIES feedback to vasomotor centre by GLOSSOPHARYNGEAL NERVE
  • receptors in AORTIC ARCH feedback to vasomotor centre via VAGUS NERVE
41
Q

Between what range do carotid sinus baroreceptors respond to pressure ? Which range are they most sensitive?

A

Respond: 60-180 mmHg

Most sensitive: 90-100 mmHg

42
Q

What is meant by reciprocal innervation w.r.t. baroreceptor firing

A

Baroreceptor senses increase in pressure–> increased firing

  1. Increase in firing= increase in parasympathetic activity
  2. Increase in firing= decrease in sympathetic activity (via inhibitory neurones)
43
Q

How does parasympathetic stimulation of the heart occur? What is the result of this?

A

Via the VAGUS NERVE

- causes a decrease in heart rate

44
Q

What is the result of the decrease in sympathetic stimulation to the heart?

A

Decreased heart rate

decreased stroke volume

45
Q

What is the result of decreased sympathetic stimulation to the blood vessels?

A

Vasodilation

46
Q

What is the afferent and efferent activity of the vagus nerve?

A 
Afferent= baroreceptor impulse to VMC
Efferent= VMC back to the heart
47
Q

Describe the sequence of events after an increase in arterial blood pressure

A
  • Increase in arterial BP
  • increased frequency of firing by baroreceptors
  • detected by VMC which triggers increased traffic in vagus nerve
  • increase in Each production in SAN –> decrease in gradient of pacemaker potential –> decrease in hr
  • increase in baroreceptor firing = decrease in sympathetic activity as well
  • decreases heart rate and stroke volume and force of contraction
  • increase in vessel radius

==> decrease in blood pressure

My LSS- CVS (21 decks)

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