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CAM201 Pharmacology > ANS > Flashcards

ANS Flashcards

1
Q

What are some of the major functions of the ANS?

A
  • maintain homeostasis
  • coordinate response to external stimuli (fight or flight)
  • specific regulatory functions
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2
Q

what are some of the specific functions of the ANS?

A
  • contraction and relaxation of the vascular and visceral smooth muscle
  • CVS reflexes
  • all exocrine and endocrine secretions
  • energy metabolism, particularly in liver and skeletal muscle
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3
Q

What are the divisions of the ANS? what do they do?

A

SNS

  • dominates during stress and emergency situations
  • expenditure of energy
  • increase in BGL, heart activity and BP

PNS

  • conserve energy
  • reduce HR
  • increase GI and secretions

Enteric
- comprises the intrinsic nerve plexuses of GI tract

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4
Q

What are some of the responses of the SNS?

A
  • increased HR
  • vasoconstriction and increased BP
  • skeletal muscle vasodilation and tremor
  • pupil dilation, adjusting for far vision
  • bronchodilation
  • glycogenolysis, gluconeogenesi, lipolysis, thermogenesis
  • sweating
  • release of adrenaline
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5
Q

What are some responses of the PNS?

A
  • decrease HR to resting
  • digestion and secretion of waste products, increased Gi motility, gastric acid secretion, defecation, urination
  • pupil constriction, accommodation for near vision, lacrimation
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6
Q

What are autonomic efferent pathways made of?

A
  • Preganglionic neurons
  • autonomic ganglia (contains nerve endings of preganglionioc and cell bodies of postganglionic)
  • post ganglionic neurons
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7
Q

What are the main neurotransmitters in the ANS?

A

Acetylcholine and noradrenaline

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8
Q

How do cholinergic nerves function?

A

Using Acetycholine on:

ALL preganglioninc nerves

ALL post ganglionic nerves in the PNS

ACTS on nicotininc and muscurain

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9
Q

How do noradrenergic nerves function?

A

Use noradrenaline on:

most post ganglionic nerves in the SNS

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10
Q

Describe the neurons and their actions in the PNS

A

Preganglionic neurons release Ach which acts on nicotinic receptors in the cell body of the postganglionic neuron

Postganglionic neurons release AcH which acts on the muscarinic receptors on the effector tissue

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11
Q

What is cholinergic transmission?

A

Nerve transmission mediated by acetylcholine

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12
Q

What are the functions of acetylcholine in the CNS and PNS?

A

CNS: arousal, learning, memory and motor control

PNS:

  • ANS: involuntary control of many structures
  • enteric: involuntary control of the GIS
  • somatic: voluntary control of skeletal muscles
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13
Q

Describe the steps in cholinergic transmission

A
  1. Uptake of choline
  2. Synthesis of AcH
  3. Uptake of transmitter into synaptic vesicles
  4. degradation of surplus AcH
  5. depolarisation by propagated action potential
  6. opening of voltage gated Ca2+ channels
  7. release of transmitter by exocytosis
  8. diffusion to postsynaptic membrane
  9. binding to postsynaptic receptors
  10. inactivation of ACh by ACHE
  11. reuptake of transmitter or degradation products by nerve terminal
  12. uptake of ACh by non-neuronal cells
  13. Binding with presynaptic receptors
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14
Q

What is the nicotinic receptor?

A

a cholinergic receptor activated by acetycholine.

Ligand gated ion channel with two Ach binding sites.

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15
Q

What happens when ach binds to a nicotinic receptor?

A

the channel opens and Na+ enters, causing membrane depolarisation

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16
Q

Where are nicotinic receptors located and what do they do?

A

Skeletal muscle: cause contraction

Autonomic ganglia: allow transmission between pre and post ganglionic neurons

adrenal medulla: cause release of adrenaline

CNS: excitation

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17
Q

What is the muscarinic receptor?

A

A GPCR activated by acetylcholine. It passes on a message within the cell that generates a cellular response

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18
Q

What are the types of muscarinic receptors and their general functions?

A

M1: neural
M2: cardiac
M3: glandular/smooth muscle
M4/M5: mostly CNS

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19
Q

What is the role of M1 receptors and where are they located?

A

Found mainly on CNS and peripehral neurons and gastric parietal cells, M1 receptor activation has excitatory effects

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20
Q

What is the role of M2 receptors and where are they located?

A

Found mainly on the heart, M2 receptor activation has inhibitory effects

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21
Q

What is the role of M3 receptors and where are they located?

A

Located mainly on smooth muscle and glands, receptor activation has excitatory effects

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22
Q

What is the role of M4/M5 receptors and where are they located?

A

Mainly in the CNS. Function is not well understood

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23
Q

What is the mechanism of the M1 receptor? What is the result?

A

Gq: activates phospolipase C
= increased IP3 and DAG
= increased Ca2+

RESULT: neuronal excitation

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24
Q

What is the mechanism of the M2 receptor? What is the result?

A

Gi: inhibitis adenylate cyclase
= decreased cAMP
= decreases PKA
= decreased opening of Ca2+ channels

RESULT: reduce HR and contractility

25
Q

What is the mechanism of the M3 receptor? What is the result?

A

Gq: activates phospholipase C
= increased IP3 and DAG
=increased Ca2+

RESULT: contraction of visceral smooth muscle. secretion of exocrine glands.

CAN cause relaxation of some smooth muscles, mainly vascular, via the release of nitric oxide from neighbouring endothelial cells (not innveravted by PNS but respond to circulating muscarinic agonists)

26
Q

What are the PNS effects of M2 on the heart?

A

decreased rate and force of contraction

27
Q

What are the PNS effects of M3 on the blood vessels?

A

generally none as there is no PNS innervation.

exception: erectile tissue which has mediated vasodilation via nitric oxide. dilated by exogenous muscarinic agonsts

28
Q

PNS effects of M3 on smooth muscle (incl. bronchi, GI and bladder)?

A

contraction

29
Q

PNS effects of M3 on the eye?

A

Contraction of the pupil = miosis

contraction of the ciliary muscle = near vision

30
Q

PNS effects of M3 on the exocrine sweat glands

A

No PNS innervation, but muscarinic receptors respond to sympathetic innervation

31
Q

PNS effects of M3 on the exocrine lacrimal, salivary and bronchial glands?

A

secretion

32
Q

What does the SNS do?

A

control the fight or flight response

33
Q

What do preganglionic neurons in the SNS relase?

A

Ach which acts on nicotinic receptors in cell bodies of the postganglionic neuron

34
Q

What do most postganglionic neurons release in the SNS?

A

noradrenaline, which acts on alpha or beta receptors of the effector tissue

35
Q

How are sweat glands innervated?

A

By SNS Ach acting on muscarinic receptors

36
Q

How is the adrenal medulla innervated?

A

by SNS Ach acting on nicotinic receptors

37
Q

What is the transmitter used in noradrenergic transmission?

A

noradrenaline

38
Q

What are the functions of NA in the CNS and periphery?

A

CNS: arousal, mood and BP regulation

Peripheral: functions associated with the SNS

39
Q

What are the receptors that are activated by noradrenaline and adrenaline?

A

alpha and beta

40
Q

What are the steps in noradrenergic transmission?

A
  1. uptake of precursor (tyrosine)
  2. synthesis of NA
  3. uptake of NA into synaptic vesicles via vesicular monoamine transporter (VMAT)
  4. degradation of surplus NA via monoamine oxidase (MAO)
  5. depolarisation by propagated action potential
  6. opening of voltage gated ca2+ channels
  7. release of transmitter by exocytosis
  8. diffusion to postsynaptic membrane
  9. binding to postsynaptic receptors
  10. inactivation of transmitter (most is recycled)
  11. reuptake of transmitter by nerve terminal via norepinephrine transporter (NET)
  12. uptake of transmitter by non-neuronal cells via extra neuronal transporter (ENT)
  13. binding with presynaptic receptors (alpha 2 autoinhibitory receptors)
41
Q

What are the 3 actions of noradrenaline?

A
  1. stimulate post synaptic noradrenergic receptors on effector organs
  2. stimulate pre synaptic auto-inhibitory receptors
  3. undergo re-uptake back into the nerve for re-storage in vesicles or metabolism to inactive metabolites by monoamine oxidase
42
Q

Describe a noradrenergic receptor

A

GPCR that is activated by adrenaline and noradrenaline. Passes on a message within the cell, generating a cellular response

43
Q

What are the four types of noradrenergic receptors? What are their functions?

A

Alpha-1

  • smooth muscle
  • excitation

Alpha-2

  • presynaptic autonomic nerves
  • inhibition

Beta-1

  • cardiac muscle
  • excitation

Beta-2

  • smooth muscle
  • inhibition
44
Q

Describe the receptor mechanism of alpha-1

A

Gq: activates phospholpiase C

  • increased IP3 and DAG
  • increased intracellular calcium
  • causes contraction of smooth muscle
45
Q

describe the receptor mechanism of alpha-2

A

Gi: inhibits adenylate cyclase

  • decreased cAMP
  • decreased PKA
  • decreased opening of ca2+channels
  • acts on autonomic nerves to inhibit and cause a decrease in NA release
46
Q

Describe the mechanism of beta-1 receptors

A

Gs: activates adenylate cyclase

  • increased cAMP
  • increased PKA
  • opening of ca2+ channels
  • increases HR and contractility of cardiac muscle
47
Q

Describe the mechanism of beta 2 receptors

A

Gs: activates adenylate cyclase

  • increased cAMP
  • increased PKA
  • inhibition of contractile enzymes leading to contraction
48
Q

What is the effect of B1 on the heart

A

increased rate, increased force of contraction

49
Q

What is the effect of A1 on the blood vessels of the viscera, skin, brain and large coronary

A

constriction

50
Q

What is the effect of B2 on the blood vessels of the skeletal muscle and small coronary

A

dilation

51
Q

What is the effect of B2 on the bronchial smooth muscle

A

relaxation

52
Q

What is the effect of B2 on the GI muscle

A

relaxation

53
Q

What is the effect of B2 on the smooth muscle of the bladder

A

relaxation

54
Q

What is the effect of A1 on the pupil

A

dilation (control of radial muscles)

55
Q

What is the effect of B2 on the ciliary muscle of the eye

A

relaxation (far vision)

56
Q

What is the effect of A1 and B2 on the liver

A

Increased glycogenolysis

increased gluconeogenesis

57
Q

What is the effect of A2 on the pancreas

A

decreased insulin secretion via adrenaline

58
Q

What is the effect of B2 on the skeletal muscle

A

tremor

59
Q

Summarise the drug targets in the ANS

A

Receptors

  • Muscarinic
  • nicotinic
  • alpha
  • beta

Enzymes

  • ACHE
  • MAO

Transporters

  • NET
  • VMAT

CAM201 Pharmacology (3 decks)

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