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Semester 2-CVS > Session 4-Autonomic Control Of CVS > Flashcards

Session 4-Autonomic Control Of CVS Flashcards

1
Q

What are the two divisions of the ANS?

A

Parasympathetic

Sympathetic

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2
Q

What is the enteric nervous system and what is it controlled by?

A

Network of neurones surrounding GI tract

Controlled via sympathetic and parasympathetic fibres

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3
Q

What does the ANS control in the CVS? (4)

A
  • heart rate
  • force of contraction of heart
  • peripheral resistance of blood vessels
  • amount of venoconstriction
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4
Q

True or false: the ANS initiates electrical activity in the heart

A

FALSE

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5
Q

What does innervation of the heart control?

A

Speed and force of contraction

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6
Q

Where do parasympathetic preganglionic fibres synapse with postganglionic cells?

A

On epicardial surface or within walls of heart at SA and AV node

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7
Q

What do postganglionic cells in the parasympathetic input to the heart release and what does this act on?

A

ACh

Acts on M2-receptors

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8
Q

What effect does activating M2 receptors have on the heart? (2)

A

Decrease heart rate (-ve chronotropic effect)

Decrease AV node conduction velocity

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9
Q

What does the sympathetic trunk innervate and what does it release?

A

SA node
AV node
Myocardium

Releases noradrenaline

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10
Q

What does the sympathetic trunk act on?

A

Beta1-adrenoceptors

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11
Q

What effect does activating beta1-adrenoceptors have on the heart? (2)

A

1) increases heart rate (positive chronotropic effect)

2) increases force of contraction (positive inotropic effect)

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12
Q

True or false: beta2 and beta3 adrenoceptors are also present in the heart but the main effect is mediated by beta1 receptors

A

TRUE

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13
Q

What do baroreceptors detect?

A

Pressure changes

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14
Q

Where is the cardiovascular control centre located?

A

Medulla oblongata

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15
Q

What is the term given to the SA node setting the rhythm of the heart?

A

Sinus rhythm

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16
Q

How does sympathetic activity affect the pacemaker potential?

A

Increases slope in membrane potential/time graph so AP are fired closer together and the heart rate therefore increases

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17
Q

How does parasympathetic activity affect the pacemaker potential?

A

Decreases slope of membrane potential/time graph, action potential fires slower so heart rate decreases

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18
Q

Complete the sentences:

Sympathetic effect on pacemaker potentials is mediated by _______ receptors. Stimulation of G alpha-s ____________ cAMP which _________ ____ pacemaker potential.

A

Beta1
Increases
Speeds up

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19
Q

Complete the sentences:

Parasympathetic effect is mediated by __ receptors. G alpha-_ increases __ conductance and __________ cAMP.

A

M2
i
K+
Decreases

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20
Q

How does noradrenaline increase force of contraction?

A

Acts on beta1 receptors in myocardium, causing an increase in cAMP and this activates PKA:

  • phosphorylation of Ca2+ channels increases Ca2+ entry during plateau of AP
  • increased uptake of Ca2+ in SR
  • increased sensitivity of contractile machinery to Ca2+
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21
Q

True or false: most vessels receive parasympathetic innervation

A

FALSE - sympathetic

22
Q

Give an example of tissue that has parasympathetic innervation

A

Erectile tissue

23
Q

Which receptors do most arteries and veins have?

A

Alpha1-adrenoreceptors

24
Q

What allows for vasodilation to occur?

A

Vasomotor tone

25
Q

Which blood vessels have beta2-adrenoceptors as well as alpha1-adrenoceptors? (3)

A

Skeletal muscle
Myocardium
Liver

26
Q

Which adrenoceptor does circulating adrenaline have a higher affinity for?

A

Beta2

27
Q

True or false: at higher concentrations, circulating adrenaline will also activate alpha1 receptors

A

TRUE

28
Q

What does the activation of beta2 adrenoceptors cause in vascular smooth muscle?

A

Vasodilation

29
Q

How does the activation of beta2-adrenoceptors cause vasodilation?

A

Increases cAMP -> PKA -> opens K+ channels and inhibits MLCK -> relaxation of smooth muscle

30
Q

What does the activation of alpha1-adrenoceptors cause?

A

Vasoconstriction

31
Q

How does the activation of alpha1-adrenoceptors cause vasoconstriction?

A

Stimulates IP3 production -> increase in intracellular Ca2+ from stores and via influx of extracellular Ca2+ -> contraction of smooth muscle

32
Q

True or false: active tissue produces fewer metabolites such as adenosine, K+, H+

A

FALSE - produces more metabolites

33
Q

What effect does a local increase in metabolites have?

A

Strong vasodilator effect

34
Q

Complete the sentence:

Metabolites are more important for ensuring adequate _________ of skeletal and coronary muscle than activation of ____-receptors

A

Perfusion

Beta2

35
Q

How are changes in the state of the cardiovascular system communicated to the brain?

A

Via afferent nerves

36
Q

Which receptors detect arterial pressure and are said to be on the “high pressure side of the system”?

A

Baroreceptors

37
Q

Which receptors detect venous pressure and are said to be on the “low pressure side of the system”?

A

Atrial receptors

38
Q

Where are baroreceptors located? (2)

A

Carotid sinus

Aortic arch

39
Q

What are nerve endings in the carotid sinus and aortic arch sensitive to?

A

Stretching

40
Q

What does increased arterial pressure do to baroreceptors?

A

Stretches the receptors

41
Q

Where do nerves on the aortic arch go to?

A

Vagus nerve

42
Q

What does the baroreceptor reflex do?

A

Maintains blood pressure, especially when posture changes

43
Q

What counteracts increased mean arterial pressure in the baroreceptor reflex?

A

Bradycardia

Vasodilation

44
Q

What do sympathomimetics do?

A

Mimic the sympathetic nervous system

45
Q

What do sympathomimetics do in the cardiovascular system? (3)

A

1) administer adrenaline to restore function in cardiac arrest
2) beta1-agonist - dobutamine given in cardiogenic shock
3) adrenaline administered for anaphylactic shock

46
Q

Which sympathomimetic is used to treat asthma?

A

Beta2-agonist - salbutamol

47
Q

Give an example of an alpha-adrenoceptor antagonist and give its use

A

Alpha1 antagonist eg prazosin

Anti-hypertensive agent - inhibits noradrenaline action on vascular smooth muscle alpha1-receptors (causes vasodilation)

48
Q

Is prazosin used often as an anti-hypertensive agent?

A

No-there are better things to use

49
Q

Give an example of a non-selective beta-adrenoceptor antagonist and its use

A

Propranolol
Non-selective beta1/beta2 antagonist, slows heart rate and reduces force of contraction (beta1) but also acts on bronchial smooth muscle (beta2) to cause bronchoconstriction

50
Q

Give an example of a selective beta1 antagonist

A

Atenolol

51
Q

Give an example of a muscarinic agonist and give its use

A

Pilocarpine

Treatment of glaucoma - activates constrictor pupillae muscle

52
Q

Give an example of a muscarinic antagonist and give its use

A

Atropine or tropicamide
Increases heart rate, bronchial dilation
Used to dilate pupils for examination of eye

Semester 2-CVS (18 decks)

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