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Cardiovascular System > ANS control > Flashcards

ANS control Flashcards

1
Q

The ANS is under voluntary or involuntary control?

A

Involuntary control

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2
Q

What are some examples of physiological functions that the ANS controls?

A

Heart rate

Blood pressure

Body temperature

Response to exercise, stress

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3
Q

What are some examples of tissues that the ANS controls?

A

Cardiac muscle

Smooth muscle - vascular, viscerall

Exocrine gland secretion

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4
Q

What are the two divisions of the ANS?

A

Sympathetic

Parasympathetic

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5
Q

How is the ANS divided into sympathetic and parasympathetic divisions?

A

Based on where the pre-ganglionic nerve fibres emerge from the spinal cord

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6
Q

The sympathetic and parasympathetic divisions of the ANS tend to have opposite or similar effects on a tissue?

A

Opposite effects

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7
Q

When is sympathetic activity increased?

A

During stress

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8
Q

When is parasympathetic activity more dominant?

A

During basal conditions

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9
Q

How is sympathetic activity to different tissues increased?

A

Sympathetic activity to one particular tissue can increase independently

Or sympathetic activity to all tissues can increase altogether

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10
Q

What are the receptors of the sympathetic nerveous system?

A

A1
B1
B2
M3

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11
Q

Where are A1 receptors found?

A

Pupil of eye

Sweat glands

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12
Q

What does stimulation of A1 receptors lead to?

A

Contraction of radial muscle
dilation of pupul

Localised secretion of sweat
e.g. palms

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13
Q

Where are B1 receptors located?

A

The heart

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14
Q

What does stimulation of B1 receptors lead to?

A

Increase in heart rate

Increase in force of contraction

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15
Q

Where are B2 receptors located?

A

Lungs

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16
Q

What does stimulation of B2 receptors lead to?

A

Relaxation of smooth muscle in bronchi

bronchodilation

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17
Q

Where are sympathetic M3 receptors located?

A

Sweat glands

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18
Q

What does stimulation of sympathetic M3 receptors lead to?

A

Generalised secretion of sweat

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19
Q

What are the receptors of the parasympathetic nervous system?

A

M2

M3

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20
Q

Where are M2 receptors located?

A

Heart

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21
Q

What does stimulation of M2 receptors lead do?

A

Decrease in heart rate

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22
Q

Where are parasympathetic M3 receptors located?

A

Pupil of eye

Lungs

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23
Q

What does stimulation of the parasympathetic M3 receptors lead to?

A

Contraction of sphincter muscle
constriction of pupil

Contraction of smooth muscle in bronchi
bronchoconstriction

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24
Q

What does the ANS control in the cardiovascular system?

A

Herat rate

Force of contraction of heart

Peripheral resistance - contraction, relaxation of smooth muscle in arterioes

Venoconstriction - contraction, relaxation of smooth muscle in veins

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25
Q

At rest, sympathetic or parasympathetic inputs to the heart dominate?

A

Parasympathetic input

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26
Q

If the heart was denervated, would it still beat? Why?

A

Yes

SA node myocytes would still spontaneously depolarise

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27
Q

If the heart was denervated, how would the heart rate change? Why?

A

Heart rate would increase

because would have removed large parasympathetic input

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28
Q

What is the 10th cranial nerve?

A

The vagus nerve

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29
Q

What does the vagus nerve innervate?

A

SA node

AV node

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30
Q

Where does the vagus nerve synapse with the post-ganglionic nerve fibre?

A

Epicardial surface

or within myocardium at SA and AV node

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31
Q

Which neurotransmitter do the parasympathetic post-ganglionic nerve fibres release?

A

Acetylcholine

32
Q

What receptor does the acetylcholine act on?

A

M2 receptors

33
Q

How does the stimulation of M2 receptors affect the heart?

A

Negative chronotropic effect - decrease in in heart rate

Decrease in AV node conduction velocity

34
Q

Where do post-ganglionic nerve fibres of the sympathetic nervous system arise from?

A

The sympathetic trunk

35
Q

What do post-ganglionic nerve fibres of the sympathetic nervous system innervate in the heart?

A

SA node
AV node

Myocardium

36
Q

Which neurotransmitter do post-ganglionic nerve fibres of the sympathetic nerve system release?

A

Noradrenaline

37
Q

Which receptors do noreadrenaline act on in the heart?

A

B1 receptors

38
Q

How does stimulation of the B1 receptors affect the heart?

A

Positive chronotropic effect - increase in heart rate

Positive inotropic effect - increase in force of contraction

39
Q

What are receptors that detect changes in pressure called?

A

Baroreceptors

40
Q

Where are baroreceptors of the cardiovascular system located?

A

Aortic arch

Carotic sinus

41
Q

What is the cardiovascular control centre in the nervous system?

A

Medulla oblongata

42
Q

Where is the medulla oblongata located?

A

Brainstem

43
Q

How are sensory inputs carried from the carotid sinus to the medulla oblongata?

A

Via the glossopharyngeal nerve - cranial nerve 9

44
Q

How are sensory inputs carried from the aortic arch to the medulla oblongata?

A

Via the vagus nerve - cranial nerve 10

45
Q

How is parasympathetic output carried from the medulla oblongata to the heart?

A

Via the vagus nerve - cranial nerve 10

46
Q

How does stimulation of B1 receptors increase heart rate?

A 
second messenger cAMP produced
ligand for HCN channels 
increased activity of HCN channels
increased influx of Na+
faster depolarisation to threshold
action potential fired earlier
47
Q

How does stimulation of M2 receptors decrease heart rate?

A

decrease in cAMP

Beta-gamma subunit acts on K+channels
increases their conductance
more negative membrane potential

takes longer to reach threshold
action potential fired later

48
Q

How does stimulation of B1 receptors increase force of contraction?

A

PKA activated
increased uptake of Ca2+ in SR
more Ca2+ available for release

phosphorylates VGCCs, increasing their activity
more Ca2+ influx

increased sensitivty of contractile proteins to Ca2+

49
Q

Do blood vessels recieve sympathetic or parasympathetic innervation? What is the exception?

A

Sympathetic

Erectile tissue has parasympathetic innervation

50
Q

What type of receptor do most blood vessels contain?

A

A1 adrenoceptors

51
Q

Some blood vessels have additional types of receptors. What are they?

A

Skeletal muscle vasculature
Coronary arteries

Also have B2 receptors

52
Q

What is vasomotor tone?

A

The degree of vasoconstriction
at resting output
of sympathetic nervous system

53
Q

What are the functions of the vasomotor tone?

A

To allow for vasodilation

Promote return of blood to heart

54
Q

What does increased stimulation of A1 adrenoceptors in blood vessels lead to?

A

Vasoconstriction

55
Q

What does decreased stimulation of A1 adrenoceptors in blood vessels lead to?

A

Vasodilation

56
Q

In skeletal muscle vasculature, coronary arteries…noradrenaline prefentially binds to what type of receptor?

A

A1 adrenoceptors

57
Q

In skeletal muscle vasculature, coronary arteries…adrenaline preferentially binds to what type of receptor?

A

Physiological conc. - B2 adrenoceptors

High conc - B2+A1 adrenoceptors

58
Q

What does increased stimulation of B2 adrenoceptors in blood vessels lead to?

A

Vasodilation

59
Q

How does stimulating A1 adrenoceptors in blood vessels lead to vasconstriction?

A

second messenger IP3

increased Ca2+ release from SR store

60
Q

How does stimulating B2 adrenoceptors in blood vessels lead to vasodilation?

A

PKA phosphorylates MLCK
inhibits it

PKA also opens K+ channels
hyperpolarisation of smooth muscle cell

61
Q

What are some examples of metabolites that have vasodilator effects?

A

Adenosine

H+

Increased pCO2

62
Q

In skeleta muscle, coronary arteries…is vasodilation produced by stimulation of B2 adrenoceptors or vasodilation by local metabolites more important?

A

Vasodilation by local metabolites

63
Q

What are the groups of drugs acting on the ANS?

A

Sympathomimetics - adrenoceptor agonists

Adrenoceptor antagonists

Cholinergics - muscarinic agonists and antagonists

64
Q

What is an example of a B1 agonist and when it’s used?

A

Dobutamine
given in cardiogenic shock

Adrenaline
given in anaphylactic shock, cardiac arrest

65
Q

What is an examle of a B2 agonist and when it’s used?

A

Salbutamol

given for asthma

66
Q

What is an example of a non-selective B1 antagonist?

A

Propanolol

67
Q

What is an example of a selective B1 antagonist?

A

Atenolol

68
Q

What are the advantages of selective B1 antagonists over non-selective?

A

Only have cardiac effects - reduce heart rate and force of contraction
No respiratory side effects - bronchoconstriction

69
Q

What is an exanple of a selective A1 antagonist and when it’s used?

A

Prazosin

used to treat resistant hypertension

70
Q

How do A1 antagonists work?

A

Block A1 adrenoceptors
Prevent noradrenaline stimulating A1 receptors
Loss of vasconstriction
Gives vasodilation

71
Q

What is an example of a muscarinic agonist and what it’s used for?

A

Pilocarpine

used to treat glaucoma

72
Q

How does a muscarinic agonist treat glaucoma?

A

M3 receptors in eye
stimulate sphincter muscle to contract
constricts pupil back to normal

73
Q

What are some examples of muscarinic antagonists and what they’re used for?

A

Atropine, tropicamide

Increase heart rate
Bronchodilation
Diates pupils of eye for eye examination

74
Q

What is the pre-ganglionic parasympathetic nerve fibres to the heart?

A

Vagus nerve

75
Q

How is sympathetic output carried from the medulla oblongata to the heart?

A

Via tract nerve to lower down in spinal cord
Pre-ganglionic nerve fibre from spinal cord to post-ganglionic nerve fibre
Post-ganglionic nerve fibre to SA node, AV node, myocardium

Cardiovascular System (22 decks)

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