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CVS A > Session 4 Lecture 2 > Flashcards

Session 4 Lecture 2 Flashcards

1
Q

Why is the autonomic nervous system important?

A

For regulating many physiological functions e.g. HR, BP

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2
Q

What does the ANS exert control over?

A

Smooth muscle, exocrine secretion and rate and force of contraction of the heart

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3
Q

What are the anatomical divisions of the ANS?

A

Parasympathetic

Sympathetic

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4
Q

Where does the parasympathetic ANS originate from?

A

Cranial sacral region

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5
Q

Where does the sympathetic ANS originate from?

A

Thoracic-lumbar region

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6
Q

What is the third division of the ANS that is often in textbook?

A

Enteric nervous system

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7
Q

What is the enteric ANS?

A

Network of neurones surrounding GI tract and is normally controlled via sympathetic and parasympathetic fibres

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8
Q

What is the function of the parasympathetic ANS?

A

Rest and digest - more dominant over basal conditions

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9
Q

What is the function of the sympathetic ANS?

A

Fight or flight - activity increased under stress

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10
Q

What is the parasympathetic effect on the pupil of eye?

A

dilation - contracts sphincter muscle

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11
Q

What receptor is responsible for the parasympathetic effect on the pupil of eye?

A

M3

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12
Q

What is the sympathetic effect on the pupil of eye?

A

contraction - contracts radial muscle

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13
Q

What receptor is responsible for the sympathetic effect on the pupil of eye?

A

a1

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14
Q

What is the parasympathetic effect on the airways on the lungs?

A

contract

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15
Q

What is the sympathetic effect on the lungs

A

relax

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16
Q

What is the sympathetic effect on the heart?

A

Increases rate and force of contraction

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17
Q

What is the parasympathetic effect on the heart?

A

decreases rate

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18
Q

What is the sympathetic effect on the sweat glands?

A

Localised secretion (e.g. palms). Generalised secretion

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19
Q

What is the parasympathetic effect on the sweat glands?

A

No effect

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20
Q

In the CVS, what does the ANS control?

A

Heart rate, force of contrition, peripheral resistance of blood vessels and venoconstriction

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21
Q

What does the ANS NOT do in the CVS?

A

Does not initiate electrical activity in the heart

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22
Q

Will a denervated heart still beat?

A

Yes - but at a faster rate

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23
Q

Which dominates at rest - parasympathetic or sympathetic?

A

Parasympathetic

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24
Q

Where does the parasympathetic input of the heart come from?

A

Vagus nerve which is the 10th cranial nerve

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25
Q

Where do the preganglionic fibres of the parasympathetic form a synapse?

A

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

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26
Q

What do the postganglionic cells of the parasympathetic nervous system release?

A

acetylcholine

27
Q

What does the acetyl choline act on?

A

M2 receptors

28
Q

What effect do the M2 receptors have?

A

Decrease heart rate (-ve chronotropic effect)

Decrease Av node conduction velocity

29
Q

Where do the postganglionic fibres for the sympathetic nervous system come from?

A

Sympathetic trunk

30
Q

What is the function of the sympathetic nervous system fibres?

A

Innervate SA node, AV node and myocardium.

31
Q

What mediates the action of the sympathetic nervous system?

A

Noradrenaline

32
Q

What do the postganglionic cells of the sympathetic nervous system release?

A

Noradrenaline

33
Q

What does the noradrenaline act on?

A

Acts mainly on B1 adrenoceptors

34
Q

What is the affect of the beta 1 adrenoceptors?

A

Increases heart rate and increase the force of contraction

35
Q

What is the pacemaker of the heart?

A

Action potential firing in the SAN sets the rhythm of the heart

36
Q

How does the SAN set the rhythm?

A

Cells in the SAN steadily depolarise toward the threshold. Slow depolarising pacemaker potential, turning on of a slow Na+ conductance (funny current) and opening of Ca2+ channels.

37
Q

How does sympathetic nervous system affect the pacemaker potential?

A

Increases the slope - reaches threshold sooner. Therefore speeds up pacemaker potential

38
Q

How does the parasympathetic nervous system affect the pacemaker potential?

A

Decreases the slope therefore slows down the pacemaker potential

39
Q

How does the sympathetic nervous system work on the pacemaker potential?

A

Mediated by B1 adrenocpetors, G alpha s. Increases cAMP

40
Q

How does the parasympathetic nervous system work on the pacemaker potential?

A

Mediated by M2 receptors, G alpha I. Decreases cAMP and increase K+ conductance

41
Q

How does noradrenaline increase the force of contraction?

A

NA acting on B1 receptors in myocardium causes an increase in cAMP which activates PKA.

42
Q

How does PKA cause an increase in the force of contraction?

A

PKA phosphorylates Ca2+ channels therefore inc Ca2+ entry during the plateau of the AP.

43
Q

What receptors do most arteries and veins have?

A

alpha 1 adrenoceptros

44
Q

Which receptors do coronary and skeletal vasculature also have?

A

B2 receptors

45
Q

Most vessels receive sympathetic nervous system excepts

A

Some specialised tissue e.g. erectile tissue has parasympathetic innervation

46
Q

What is sympathetic vasomotor tone?

A

The constant activity of the sympathetic nervous system that tends to make arteriolar smooth muscle contract.

47
Q

Describe the vasomotor tone in the body

A

In skin the vasomotor tone is high

In skeletal muscle the vasomotor tone is high at rest but not during exercise

48
Q

Does circulating adrenaline have a higher affinity for alpha 1 receptors or beta 2 adrenoceptors?

A

B2 adrenoceptros

49
Q

What affect does activating B2 adrenoreceptors have?

A

Causes vasodilation

50
Q

What affect does activating a1 adrenoreceptors have?

A

Causes vasoconstriction

51
Q

How does activation of B2 adrenoreceptor cause vasodilation?

A

Increase cAMP so inc PKA so opens K+ channels and inhibits MLCK therefore relaxation of smooth muscle

52
Q

Give some examples of local metabolites that active tissue might produce?

A

Adenosine, K+, H+ and increase PCO2.

53
Q

What affect does the local increases in metabolites have?

A

Strong vasodilator affect

54
Q

What are metabolites more important for?

A

For ensuring adequate perfusion of skeletal and coronary muscle than activation of B2 adrenorecptors.

55
Q

Which afferent nerves are responsible for communicating the changes in the state of the heart to the brain?

A

Baroreceptors - high pressure side of system

Atrial receptors - low pressure side of system

56
Q

What are baroreceptors?

A

Nerve endings in the carotid sinus and aortic arch that are sensitive to stretch. Increase arterial pressure stretched these receptors

57
Q

What is the baroreceptor reflex important for?

A

Maintaining blood pressure over short term

58
Q

What drugs act on the ANS?

A

Sympathomimetics, adrenoceptor antagonists and cholinergic

59
Q

Give some examples of sympathomimetics

A

a-adrenoceptor agonist

b-adrenoceptor agonist

60
Q

What do the a1 adrenoreceptors antagonists do?

A

Inhibit NA action on vascular smooth muscle a1 receptors therefore vasodilation

61
Q

How do the B-adrenoreceptor antagonists work?

A

Slow heart rate and reduced force of contraction (B1) but also acts on bronchial smooth muscle (B2) - bronchoconstriction

62
Q

How is propranolol different to atenolol?

A

Propranolol is a non selective B1/B2 antagonist and atenolol a selective B1 cardio selective.

63
Q

How do muscarinic antagonists work?

A

Increase heart rate, bronchial dilation, used to dilate pupils for examination of the eye.

CVS A (18 decks)

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