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Pharmacology > ANS Background > Flashcards

ANS Background Flashcards

1
Q

Divisions of the ANS

A

Sympathetic (Fight or Flight)
Parasympathetic (Rest & Digest)
Enteric (GIT)

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2
Q

Layout of SNS

A 
Origin: Thoracolumbar (T1 - L2)
Short Pre-ganglionic neuron
 -> Paravetrebral Ganglion
Long Post-ganglionic neuron
-> Target organ
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3
Q

Layout of PNS

A 
Origin: CN II, VII, IX, X & S 2, 3, 4
Long Pre-ganglionic neuron
-> Synaps near Target organ
Short Post-Ganglionic Neuron
-> Target organ
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4
Q

Neurotransmitters of the ANS

A

Acetylcholine (ACh)
Noradrenalin (NA)
Non-adrenergic Non-cholinergic (NANC): Serotonin, Dopamine, GABA, Histamine, NO

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5
Q

Where is Acetylcholine (ACh) found?

A

Pre-ganglionic
Post-ganglionic PNS
(Exception -> also post-ganglionic in sweat glands in SNS)

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6
Q

Where is Noradrenalin (NA) found?

A

Post-ganglionic SNS

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7
Q

What are the 6 basic steps of Transmission in the ANS?

Possible sites of Drug action?

A
  1. Synthesis of neurotransmitter (NT)
  2. Storage of NT
  3. Release of NT
  4. NT-Receptror interaction on Effector cell
  5. Removal / Degradation / Recycling of NT
  6. Repair of Effector cell membrane
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8
Q

Describe the synthesis of Ach

A
  1. Choline taken up by neuron (in conjunction with Na, via Na/K pump active transport)
  2. Glucose enters neuron via facilitated transport -> enters mitochondria -> converted to Acetyl-CoA
  3. Choline + Acetyl CoA = Acetylcholine (ACh) in cytoplasm of neuron
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9
Q

Describe storage and release of Ach at Cholinergic Junction

A
  1. ACh stored in vesicles (H released)
  2. Exocytosis into pre-synaptic cleft
  3. Binds receptors (reversible)
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10
Q

Describe the degradation of ACh

A

RAPID
1. Acetylcholine esterase (AChE)
ACh ——————————————-> Choline + Acetate
2. Bound ACh dissociates from receptor and is also broken down (hydrolysed)
3. No ACh enters circulation
4. Plasma-esterases also deactivates ACh immediately

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11
Q

Describe the synthesis and storage of the adrenergic neurotransmitters

A
  1. Tyrosine enters neuron with Na via active transport
  2. RATE LIMITING STEP:
    Tyrosine —Tyrosine Hydrolylase—> Dopa
  3. Dopa —-> Dopamine
  4. Dopamine taken up by vesicle via Vesicle Mono-Amine Transporter (VMAT)
  5. Dopamine —–B-hydroxylase—-> NA
  6. NA converted to Adrenalin ONLY IN adrenal medulla by Phenylethanolamine N-methyl-transferase (PNMT)
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12
Q

Describe the release of adrenergic neurotransmitters at Adrenergic Junction

A

Stored NA leaks out of vesicles. Taken up via active Granular uptake (also dopamine)
B hydroxylase enzyme released with NA during exocytosis

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13
Q

Describe the deactivation and degradation of NA

A

SLOWER & more COMPLEX than ACh

  1. Reuptake by adrenergic neuron NA transporter (NAT) - Na facilitated (reuptake 1)
  2. Removal by circulation -> degradation in the liver
  3. Active transport and enzymatic degradation in effector cells (reuptake 2)
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14
Q

Describe the negative feedback of the adrenergic neurotransmitters

A
  1. High levels of cytosolic NA inhibits tyrosine hydroxylase

2. NA binds to Autoceptors on pre-synaptic neuron (alpha2 receptors

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15
Q

Name the 2 enzymes which metabolise catecholamines

A

COMT (Catechol-Oxygen-MethylTransferase)

MAO (Mono-Amino-Oxidase)

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16
Q

Name the function and effect of COMT

A

Methylates the meta hydroxyl group of catecholamines.
Very specific
Lowers activity of NA & adrenaline by 100x
Works rapidly

17
Q

Name the function and effect of MOA

A

Deaminates dopamine, tyramine, 5-HTP, amine containing drugs, as well as NA & adrenaline
i.e. Protective - Destroys exogenous biologically active amines.
Not as specific as COMT

18
Q

Describe the effects of NA binding to alpha 1 receptors

A

Post-synaptic

Increased production of DAG and IP3 -> increased cellular calcium ions and depolarisation

19
Q

Describe the effects of NA binding to alpha 2 receptors

A

Auto-receptors on neuron (pre-synaptic)

Decrease cAMP production -> inhibits further release of NA from neuron

20
Q

Name the cholinergic receptors and state where these receptors are most likely found

A 
1. Nicotinic: 
 Nn - autonomic ganglia
 Nm - skeletal muscle (not in ANS)
2.  Muscarinic: PNS post-ganglionic
  M1 - gastric parietal
  M2 - heart
  M3 - glands / smooth muscle
21
Q

Name the adrenergic receptors and state where these receptors are most likely found

A

alpha 1 -> post-synaptic neurons (esp smooth muscle)
alpha 2 -> pre-synaptic mainly (auto receptors)
beta 1 -> heart, intestinal smooth muscle
beta 2 -> bronchial, uterine, vascular smooth muscle

22
Q

What overall effect does stimulation of alpha receptors bring about?

A

Excitation (except in intestinal smooth muscle)

23
Q

What overall effect does stimulation of the beta receptors bring about?

A

Inhibition (except in heart)

24
Q

Where are alpha 1 receptors mostly found?

A

post-synaptic neurons (esp smooth muscle)

25
Q

Where are alpha 2 receptors mostly found?

A

pre-synaptic mainly (auto receptors)

26
Q

Where are beta 1 receptors mostly found?

A

intestinal smooth muscle and heart

27
Q

Where are beta 2 receptors mainly found?

A

bronchial, uterine and vascular smooth muscle

28
Q

Name the different organs which are innervated by both the SNS and the PSN

A 
Heart
Bronchial tree
Iris
GIT & sphincters
Salivary glands
Bladder
Sex organs
29
Q

Name the organs which are innervated by the SNS only

A

Blood vessels
Spleen
Sweat glands
Pilo-erector muscles

30
Q

Name the major effects of stimulation of the alpha 1 receptors (5)

A
  1. Vasoconstriction
  2. Increased peripheral resistance
  3. Increased blood pressure
  4. Mydriasis (pupil dilation)
  5. Increased closure of the internal sphincter of the bladder
31
Q

Name the major effects of stimulation of the alpha 2 receptors (2)

A
  1. Inhibition of NA release

2. Inhibition of insulin release

32
Q

Name the major effects of stimulation of the beta 1 receptors (4)

A
  1. Tachycardia
  2. Increased lipolysis
  3. Increased myocardial contractility
  4. Increased release of renin
33
Q

Name the major effects of stimulation of the beta 2 receptors (6)

A
  1. Vasodilation
  2. Slightly decreased peripheral resistance
  3. Bronchodilation
  4. Increased muscle & liver glycogenolysis
  5. Increased release of glucagon
  6. Relaxed uterine smooth muscle

Pharmacology (3 decks)

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