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Sustaining life > drugs and the autonomic nervous system (part 2 - sympathetic) (W5) > Flashcards

drugs and the autonomic nervous system (part 2 - sympathetic) (W5) Flashcards

1
Q

what neurotransmitter do preganglionic sympathetic nerves secrete

A

acetylcholine

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2
Q

what neurotransmitter do postganglionic sympathetic nerves secrete

A

mainly noradrenaline

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3
Q

what receptors do acetylcholine released from preganglionic sympathetic nerves act on?

A

nicotinic receptor at preganglionic synapse

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4
Q

when do postganglionic nerves not secrete noradrenaline? what do they secrete instead and what receptors does it act on?

A

the skin
acetylcholine
acts on muscarinic cholinergic receptors

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5
Q

what receptors does noradrenaline from sympathetic postganglionic nerves act on

A

alpha or beta adrenoreceptors in effector organs

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6
Q

what enzyme is responsible for degradation of intracellular noradrenaline

A

monoamine oxidase (MAO)

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7
Q

what enzyme is responsible for degradation of noradrenaline in the synaptic cleft

A

catechol-O-methyl transferase (COMT)

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8
Q

what are alpha-1 receptors linked to

A

inositol triphosphate (IP3)

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9
Q

what does inositol triphosphate (IP3) cause in smooth muscles

A

constriction

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10
Q

what are beta receptors linked to

A

cyclic adenosine monophosphate (cAMP)

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11
Q

what does cyclic adenosine monophosphate (cAMP) cause in smooth muscle

A

relaxation

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12
Q

what causes negative feedback down-regulation of noradrenaline release

A

pre-synaptic alpha-2 adrenergic receptors

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13
Q

catecholamine neurotransmitters?

A

adrenaline (A)
noradrenaline (NA)

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14
Q

what are catecholamines synthesised from

A

the essential amino acid phenylalanine

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15
Q

where are catecholamines stored

A

terminal branches of postganglionic fibres visible as varicosities (swellings - creates string of beads appearance)

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16
Q

name for specific postsynaptic cell surface receptors that mediate the actions of catecholamines?

A

adrenoceptors

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17
Q

alpha-adrenoceptor-mediated effects (eg vasoconstriction) have been termed what? why?

A

alpha1-effects.
this differentiates them from the feedback inhibition by noradrenaline on its own release from presynaptic terminals, which is mediated by alpha2-adrenoceptors on the presynaptic membrane

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18
Q

what are beta1-adrenoceptor-mediated effects important to be differentiated from?

A

beta2 effects (smooth muscle relaxation in bronchi and blood vessels)

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19
Q

beta1-adrenoceptor-mediated effects in the heart?

A

increase force and rate of contraction

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20
Q

adrenaline and noradrenaline difference in effects on beta1 adrenoceptors in the heart?

A

equal effect

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21
Q

adrenaline and noradrenaline difference in effects on beta2 adrenoreceptors in smooth muscle?

A

receptors more sensitive to circulating adrenaline than noradrenaline

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22
Q

what do alpha1-adrenoreceptors cause?

A

vasoconstriction of blood vessels (IP3)

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23
Q

alpha2-adrenoceptors?

A

located in presynaptic membrane, feedback inhibition by noradrenaline on its own release from presynaptic terminals

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24
Q

beta1-adrenoreceptors?

A

increased force and rate of contraction of the heart (cAMP)

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25
Q

beta2-adrenoreceptors?

A

bronchial smooth muscle relaxation (cAMP)
vasodilation of blood vessels

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26
Q

parasympathetic effects?

A

decreases heart rate (causing reduced bp)
promotes:
-conservation of energy
-glandular secretions
-peristalsis in gi tract
-emptying bowel & bladder
constricts bronchi and pupils

27
Q

sympathetic effects?

A

increased circulation to exercising muscle
release of energy stores
diverts blood flow from less important circulations
dilates bronchi
dilates pupils
constricts sphincters

28
Q

parasympathetic effects on heart

A

act at muscarinic receptors (M2) which inhibits cAMP generation, reduces calcium entry and stabilises the membrane potential of excitable pacemaker cells by increasing potassium conductance. these effects reduce cardiac output.

29
Q

sympathetic nervous systems 2 actions on the heart?

A

increase heart rate
increases contractility of ventricular myocardial muscle

30
Q

how does the sympathetic nervous system increase heart rate

A

increases rate that pacemaker cells in SA node and AV node depolarise and transmit action potential. also increases rate of conduction of electrical impulses

31
Q

what does the sympathetic nervous systems change in contractility result in

A

increase in stroke volume

32
Q

what is the effect of the sympathetic nervous system on cardiac contractility called

A

positive inotropic effect

33
Q

what is the effect of the sympathetic nervous system on heart rate called

A

positive chronotropic effect

34
Q

how does the parasympathetic nervous system relax smooth muscle in blood vessels

A

muscarinic M3 receptors cause increase in nitric oxide, stimulating guanylate cyclase (enzyme for cGMP synthesis). cGMP causes smooth muscle relaxation and vasodilation

35
Q

sympathetic activation on vasculature?

A

noradrenaline at alpha-1 receptors causes vasoconstriction in most areas (causes bp rise).
causes vasodilation in muscles as they mainly have beta-2 adrenergic receptors.
causes venoconstriction which mobilises some venous blood volume to support increase in cardiac output.

36
Q

2 parasympathetic actions on the lungs

A

bronchoconstriction and glandular secretion

37
Q

how does the parasympathetic nervous system cause bronchoconstriction

A

contraction of smooth muscle surrounding bronchi and bronchioles - as a result of activation of muscarinic M3 receptors

38
Q

glandular secretion due to parasympathetic actions on the lungs?

A

mucus secretion from the glands lining the bronchi and upper airways via muscarinic M3 receptors

39
Q

explain bronchodilation due to the sympathetic nervous system? effects?

A

activation of beta-2 adrenoceptors causes relaxation of smooth muscle surrounding bronchi and bronchioles. this reduces airflow resistance, improves alveolar ventilation, increases exercise capacity.

40
Q

parasympathetic actions on salivary and other glands?

A

stimulates secretion (M3).
submandibular and parotid salivary glands, pharyngeal and oesophageal glands

41
Q

parasympathetic actions on stomach?

A

stimulates motility of stomach (M3)
stimulates secretion of gastric acid

42
Q

parasympathetic actions on gallbladder and bile duct

A

stimulates contraction of gallbladder (M3)

43
Q

parasympathetic actions on bowel wall

A

stimulates smooth muscle to increase peristalsis (M3)
stimulates digestive secretions (M3)

44
Q

parasympathetic actions on sphincters?

A

relaxes smooth muscle in sphincters (M3) to permit onward transit of food and bowel contents

45
Q

sympathetic actions on salivary glands

A

stimulates viscous rather than watery secretions (alpha-1)

46
Q

sympathetic actions on bowel wall

A

relaxes smooth muscle of gut wall to decrease peristalsis (alpha-1, beta-2)

47
Q

sympathetic actions on sphincters

A

constricts smooth muscle in sphincters (alpha-1) and so reduces onward transit of food and bowel contents

48
Q

sympathetic actions on liver

A

stimulates glycogenolysis (beta-2), the process of mobilising glucose into circulating blood from glycogen stores
stimulates gluconeogenesis, the process of synthesising glucose from precursors

49
Q

parasympathetic actions on bladder wall

A

constricts smooth muscle (detrusor) of bladder wall (M3) to initiate passage of urine

50
Q

parasympathetic actions on sphincters in bladder

A

relaxes smooth muscle to allow passage of urine (M3)

51
Q

parasympathetic actions on genitalia

A

dilates the blood vessels (M3), supplying the clitoris and penis to promote erection

52
Q

sympathetic actions on bladder wall

A

relaxes smooth muscle of bladder wall (beta-2) reducing possibility of urinating

53
Q

sympathetic actions on sphincters in bladder

A

constricts smooth muscle in sphincters (alpha-1) reducing possibility of urinating

54
Q

sympathetic actions on female reproduction

A

contraction of myometrium of pregnant uterus during labour (alpha-1)
relaxation of myometrium (beta-2)

55
Q

sympathetic actions on male reproduction

A

ejaculation (alpha-1)

56
Q

parasympathetic actions on lacrimal gland of eye

A

secretion of tears (M3)

57
Q

parasympathetic actions on iris

A

contraction of the constrictor pupillae muscle of the iris (M3) causing miosis (small pupils)

58
Q

parasympathetic actions on ciliary muscle

A

contraction of ciliary muscle which adjusts the curvature of the lens (M3) altering its refraction

59
Q

sympathetic actions on iris

A

relaxation of the constrictor pupillae muscle of iris (alpha-1, beta-2) causing mydriasis (dilated pupils)

60
Q

sympathetic actions on renal blood vessels?

A

constrict renal arterioles (alpha-1) reducing blood flow and therefore urine production

61
Q

sympathetic actions on renin secretion

A

stimulates release of renin (enzyme) from the juxtaglomerular apparatus (beta-1, beta-2). renin catalyses the conversion of angiotensinogen into angiotensin 1, which is converted to angiotensin 2. this is a potent vasoconstrictor and stimulates the release of aldosterone (main sodium retaining hormone in the body)

62
Q

sympathetic actions on adipocytes

A

stimulates lipolysis (beta-3), the process of breaking down triglyceride stores to release free fatty acids which are an energy source for muscles

63
Q

other sympathetic effects?

A

muscle tremor (beta-2)
platelets aggregation (alpha-2)
sweating (muscarinic)

Sustaining life (13 decks)

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