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Year 1: Cardiovascular System > 11. Regulation of the cardiovascular system > Flashcards

11. Regulation of the cardiovascular system Flashcards

1
Q

What is venous volume distribution affected by?

A

Peripheral Venous Tone
Gravity
Skeletal Muscle Pump
Breathing

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2
Q

What are the ways of regulating flow?

A

Local Mechanisms - intrinsic to the smooth muscle
Hormonal
Autonomic Nervous System - innervates arterioles and veins to produce constriction or dilation

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3
Q

Define autoregulation

A

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

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4
Q

What happens to resistance when blood pressure decreases?

A

There is a gradual decrease in resistance and hence a gradual increase in flow

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5
Q

What is the myogenic theory?

A

Smooth muscle fibres respond to stretch

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6
Q

What is the metabolic theory?

A

When a vascular bed contracts the flow decreases and the more metabolites are produced. This feeds back on the vessel and causes vasodilation and hence allows more flow to the vascular bed washing the metabolites away

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7
Q

What vasoconstrictor is released by platelets?

A

Serotonin

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8
Q

What hormones regulate blood flow?

A

Kinins
ANP
Circulating vasoconstrictors

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9
Q

What are the effects of kinins?

A

Interact with renin-angiotensin system

Relax vascular smooth muscle

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10
Q

What are the effects of ANP?

A

ANP = Atrial Natriuretic Peptide

Causes vasodilation, secreted from the cardiac atria

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11
Q

List some circulating vasoconstrictors

A

Vasopressin
Angiontensin II
Noradrenaline

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12
Q

What does the sympathetic nervous system control?

A

The flow

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13
Q

What does the parasympathetic nervous system control?

A

Heart rate - The parasympathetic ganglion will be right beside the sinoatrial node due to the long pre and short post ganglionic fibre

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14
Q

What vessels do sympathetic nerve fibres not innervate?

A

Capillaries

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15
Q

Which organs have the greatest sympathetic nerve supply?

A

Kidney, gut, spleen and skin

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16
Q

Which organs receive the fewest sympathetic nerves?

A

Skeletal muscle and brain

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17
Q

What does the distribution of nerve supply suggest?

A

The more nerves the more potential there is to constrict and redirect blood flow away from those organs

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18
Q

What happens at low concentrations of adrenaline?

A

Binds to smooth muscle beta-2-adrenoreceptors causing vasodilation

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19
Q

What happens at high concentrations of adrenaline?

A

Binds to alpha adrenoreceptors overriding the effects of the beta-2-adrenoreceptors. Vasoconstriction

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20
Q

What receptor is responsible for constriction in blood vessels?

A

alpha-1-adrenoreceptor

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21
Q

Where is the VMC located?

A

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

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22
Q

What is the VMC?

A

Vasomotor centre

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23
Q

What does the VMC consist of?

A

Vasoconstrictor area
Vasodilator area
Cardioregulatory inhibitory area

24
Q

What portion of the VMC controls heart activity?

A

Lateral portions

25
Q

What do the lateral portions of the VMC control?

A

Heart rate and contractility

26
Q

What does the medial portion of the VMC send signals to?

A

Vagus nerve to the heart decreasing heart rate

27
Q

What response does the VMC allow before exercise?

A

Anticipatory response to excercise

28
Q

What neurotransmitter is involved with sympathetic innervation?

A

noradrenaline

29
Q

What happens if you increase the nerve traffic in a sympathetic nerve supplying a blood vessel?

A

You constrict the vessel

30
Q

What happens if you decrease the nerve traffic in a sympathetic nerve supplying a blood vessel?

A

You dilate the vessel

31
Q

What are the three factors that can control vessel radius?

A

1) Local Controls
2) Circulating Hormones
3) Sympathetic Vasocontrictor Nerves

32
Q

How is the heart rate changed?

A

By dual innervation - sympathetic and parasympathetic

33
Q

What innervates the SAN?

A

Sympathetic and parasympathetic nerves

34
Q

What is normal resting heart rate?

A

70 bpm

35
Q

How does parasympathetic nerves affect the heart?

A

It slows heart rate - acetylcholine decreases the gradient of the pacemaker potential

36
Q

How does the sympathetic nerves affect the heart?

A

Increases heart rate - adrenaline and noradrenaline increase the gradient of the pacemaker potential

37
Q

What can increase the force of contraction?

A

Starling’s Law and Sympathetic activity

38
Q

How does the sympathetic activity increase the force of contraction?

A

Noradrenaline binds to Adrenoreceptors which increases the amount of cAMP which activates PKA which phosphorylates the L-type calcium channels and the SR calcium release channel and SERCA. So you get MORE CALCIUM INFLUX and more calcium taken back up into the stores

39
Q

What adrenoreceptor does noradrenaline bind to in the heart?

A

beta-1-receptors

40
Q

What does binding of beta-1-receptors cause in the heart?

A

Increased contraction

41
Q

What can increase stroke volume?

A

Starling’s law
Increased sympathetic nerves to heart
Increased plasma adrenaline

42
Q

How does increasing respiratory movements increase venous return to the heart?

A

Decreasing intrathoracic pressure helps filling of the heart

43
Q

What does increasing the sympathetic activity to heart cause?

A

Increased heart rate and Stroke volume

44
Q

Where are baroreceptors located?

A

Aortic arch and in the carotid sinus (bodies)

45
Q

Where do the baroreceptors in the carotid bodies feedback to?

A

To the vasomotor centre via the glossopharyngeal nerve

46
Q

Where do the baroreceptors in the aortic arch feedback to?

A

To the vasomotor centre via the vagus nerve

47
Q

Aortic arch baroreceptor =

A

Vagus nerve

48
Q

Carotid sinus baroreceptor =

A

Glossopharyngeal nerve

49
Q

What pressure do the carotid sinus baroreceptors respond to?

A

60 and 80 mmHg

50
Q

What pressure do the aortic arch baroreceptors respond to?

A

90-100 mmHg

51
Q

Reciprocal innervation - What happens the baroreceptor detects a increase in pressure?

A

Increase in baroreceptor firing = Increase in parasympathetic activity and decrease in sympathetic activity.
The decrease in sympathetic activity is brought about by inhibitory interneurones

52
Q

What is the overall effect when the baroreceptors detect a increase in blood pressure?

A

Decrease heart rate (increased parasympathetic stimulation and decreased sympathetic stimulation) and vasodilation (decreased sympathetic stimulation to the blood vessels)

53
Q

What can the strength of contraction not be altered by?

A

parasympathetic activity

54
Q

Where does an increase in baroreceptor fed to?

A

vasomotor centre causing increased increased traffic in the vagus nerve

55
Q

How does an increase in parasympathetic activity affect the SAN?

A

There is an increased production of acetylcholine in the SAN which serves to decrease the gradient of the pacemaker potential = decreasing heart rate

56
Q

Less innervation from the sympathetic nerves causes what?

A

Decreased force of contraction and increase in vessel radius

57
Q

Overall what does an increased parasympathetic and decreased sympathetic innervation cause?

A

Decrease in blood pressure

Year 1: Cardiovascular System (21 decks)

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