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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
Where is the vasomotor centre located in the brain?
Bilaterally in the reticular substance of the medulla and in the lower third of the pons
26
What does the vasomotor centre consist of?
1. Vasoconstrictor area (pressor) 2. Vasodilator centre (depressor) 3. Cardioregulatory inhibitory area
27
What does the lateral portion of the VMC control?
Heart activity by influencing: - heart rate - contractility
28
What does the Medial portion of the VMC do?
Transmits signals via the vagus nerve to the heart | --> decreases Heart Rate
29
What is the function of the VMC?
allows an anticipatory response to exercise | -> hr and ventilation rate go up slightly before exercise
30
What sot of innervation do blood vessels receive and which neurotransmitter is involved?
- receives sympathetic postganglionic innervation - noradrenaline * not much parasympathetic innervation
31
What is the importance of the blood vessels being tonically active
- at baseline have certain frequency of impulses= vasomotor tone - increase impulse-> constriction - decrease impulse -> dilation
32
What innervates the heart and which neurotransmitters are involved?
- Parasympathetic- decreases heart rate- acetylcholine | - sympathetic- increases heart rate - adrenaline and noradrenaline
33
How do the neurotransmitters involved in controlling the heart rate work?
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
What is the resting heart rate? What is the heart rate with no innervation?
70 bpm | 100 bpm
35
How can force of contraction be increased?
- Starling's law | - increase sympathetic activity
36
Explain how sympathetic activity increases the force of contraction
- 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
How is stroke volume increased?
``` 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
How could you increase venous return to help increase stroke volume?
Increase RESPIRATORY MOVEMENT: - decreasing intrathoracic pressure - increases filling of the heart and EDV
39
How is cardiac output increased during the fight or flight response?
- increased respiratory movement - increased plasma adrenaline - increased sympathetic activity to the heart
40
Where are baroreceptors found? what do they feedback back to?
- 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
Between what range do carotid sinus baroreceptors respond to pressure ? Which range are they most sensitive?
Respond: 60-180 mmHg Most sensitive: 90-100 mmHg
42
What is meant by reciprocal innervation w.r.t. baroreceptor firing
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
How does parasympathetic stimulation of the heart occur? What is the result of this?
Via the VAGUS NERVE | - causes a decrease in heart rate
44
What is the result of the decrease in sympathetic stimulation to the heart?
Decreased heart rate | decreased stroke volume
45
What is the result of decreased sympathetic stimulation to the blood vessels?
Vasodilation
46
What is the afferent and efferent activity of the vagus nerve?
``` Afferent= baroreceptor impulse to VMC Efferent= VMC back to the heart ```
47
Describe the sequence of events after an increase in arterial blood pressure
- 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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