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Pharmacology > Autonomic Neurotransmission- Cholinergic transmission > Flashcards

Autonomic Neurotransmission- Cholinergic transmission Flashcards

1
Q

How is the nervous system divided?

A

the Nervous system is divided into - CNS and PNS

  • PNS -> sensory neurons and motor neurons
  • Motor neurons -> autonomic and somatic
  • Autonomic - sympathetic and Parasympathetic
  • ANS: independent, activities are not under conscious control, concerned with visceral functions such as cardiac output, blood flow distribution, and digestion.
  • Somatic: voluntary functions such as movement, respiration, and posture
  • Parasympathetic - rest and digest
  • Sympathetic- fight or flight
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2
Q

What is the morphology of the nerves in the ANS?

A

2 neurons:

  • Preganglionic -> cellular bodies in the CNS
  • Postganglionic ->cellular bodies in the autonomic ganglia
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3
Q

What is the function of the nerves in the ANS?

A

control of heart, smooth muscles, and exocrine glands

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4
Q

Compare sympathetic and parasympathetic nerves.

A 
Sympathetic: 
- site of origin: thoracolumbar (thoracic and lumbar region of the spinal cord)
- length of fibers: 
Short preganglionic 
Long postganglionic
Parasympathetic:
- site of origin: 
Craniosacral (brain and sacral area of teh spinal cord)
- length of fibers
Long preganglionic 
Short postganglionic
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5
Q

How do the neurotransmitters and motor nerves function in the ANS?

A

What are the neurotransmitters involved:

  • Acetylcholine
  • Norepinephrine
  • Dopamine

Acetylcholine:

  • all preganglionic nerve fibers (S and PS)
  • Postganglionic parasympathetic fibers
  • postganglionic sympathetic fibers to the sweat glands
  • voluntary motor fibers

Norepinephrine:

  • Postganglionic sympathetic fibers
  • Adrenal medulla (+epinephrine)

Dopamine:
- Postganglionic sympathetic fibers to the renal vascular smooth muscle

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6
Q

What are the different types of cholinergic receptors?

A

Which is a cholinergic receptor?

Cholinergic receptors are receptors on the surface of cells that get activated when they bind a type of neurotransmitter called acetylcholine.

  • Nicotinic (Nn, Nm)
  • Muscarinic (M1-5)
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7
Q

Where are M1 receptors localized and what type of cellular response do they elicit?

A

M1 = ‘neural’

Localized:

  • Cerebral cortex
  • Autonomic ganglia
  • glands: gastric, salivary, lacrimal, etc.

Cellular response:
- GPCR (Gq)
increase IP3, DAG, Excitation

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8
Q

Where are M2 receptors localized and what type of cellular response do they elicit?

A

M2 = ‘cardiac’

Localized:

  • heart - atria
  • CNS: widely distributed

Cellular response:

  • GPCR (Gi)
  • inhibition of AC (adenylyl cyclase), lower cAMP, inhibition
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9
Q

where are M3 receptors localized and what type of cell response do they elicit?

A

M3 = ‘glandular/ smooth muscle’

Localized:

  • Exocrine glands: gastric, salivary, etc.
  • Smooth muscle: gastrointestinal tract, eye, airways, bladder
  • Blood vessels: endothelium

Cellular response:

  • GPCR (Gq)
  • increase IP3, DAG, Excitation
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10
Q

Where are M4 receptors localized and what type of cell response do they elicit?

A

M4

Localized:
- CNS

cellular response:

  • GPCR (Gi)
  • inhibition of AC (adenylyl cyclase), lower cAMP, inhibition
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11
Q

Where are M5 receptors localized and what type of cell response do they elicit?

A

M5

Localized:
- CNS

Cellular response:

  • GPCR (Gq)
  • increase IP3, DAG, Excitation
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12
Q

where are Nn receptors localized and what type of cellular response do they elicit?

A

Nn

Localization:

  • Autonomic ganglia: mainly postsynaptic
  • adrenal medulla
  • CNS

Cellular response:
- Ionotropic (α,β-pentamer)
Excitatory
Increased cation permeability (mainly Na+, K+)

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13
Q

where are Nm receptors localized and what type of cellular response do they elicit?

A

Nm

Localization:
- Skeletal neuromuscular junction: mainly postsynaptic

Cellular response:
- Ionotropic (α,β,γ,δ-pentamer)
Excitatory
Increased cation permeability (mainly Na+, K+)

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14
Q

What are the effects of stimulation of cholinergic receptors on the Eye? Which receptors are found here?

A

Receptor = M3

Eye:

  • pupil
  • Ciliary muscle
  • Lacrimal secretion

Effect:

  • Contraction (miosis)
  • Contraction (accomodation)
  • Increase
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15
Q

What are the effects of stimulation of cholinergic receptors on the heart? Which receptors are found here?

A

Receptor = M2

Heart:

  • SA nose
  • AV node

Effect:

  • decrease excitation (negative bathmotropic effect)
  • decrease conductance (negative dromotropic effect)
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16
Q

What are the effects of stimulation of cholinergic receptors on the GIT? Which receptors are found here?

A

Receptor= M1 (stomach) & M2 (Intestines)

Stomach:
HCl -> increase secretion

Intestines:

  • longitudinal muscles -> contraction
  • Sphincter muscles -> relaxation
  • intestinal glands _> increased secretion
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17
Q

What are the effects of stimulation of cholinergic receptors on the genitourinary tract? Which receptors are found here?

A

Receptor = M3

Effect:
Genitourinary tract:
- Bladder 
Detrusor: contraction
Sphincter: relaxation
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18
Q

What are the effects of stimulation of cholinergic receptors on the Bronchi? Which receptors are found here?

A

Receptor = M3

Effect:
Bronchi:
smooth muscles -> contraction
Glands -> increase secretion

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19
Q

What are the effects of stimulation of cholinergic receptors on the glands? Which receptors are found here?

A

Receptor = M3 (salivary glands) & M (sweat glands)

Effect:

Salivary glands -> increase secretion

Sweat glands (thermoregulatory, S fibers) -> increase secretion

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20
Q

What are the effects of stimulation of cholinergic receptors on the skeletal muscles? Which receptors are found here?

A

Receptors = Nm

Effect:

Skeletal muscle -> contraction

21
Q

What are the effects of stimulation of cholinergic receptors on the autonomic ganglia? Which receptors are found here?

A

Receptors = Nn

Effect:
Autonomic ganglia -> Excitation (S & PS)

22
Q

How does cholinergic transmission occur?

A
  • ACh synthesis:
  • > ACetyl CoA + choline
  • ACh is stored in synaptic vesicles
  • release of ACh (exocytosis) with the participation of Ca2+
- Binding to and activation of postsynaptic receptors:
Nicotinic receptors (Nn + Nm)
Muscarinic receptors (M1-5)
  • Inactivation of ACh
    acetylcholinesterase
  • regulation of Ach release
    Presynaptic heteroreceptors
    postsynaptic heteroreceptors
23
Q

What are the possible ways to affect cholinergic transmission?

A
  • Hemicholiniums
    = inhibit choline transporter (stop formation of ACh)
  • Vesamicol
    = inhibit vesicle-associated transporter (VAT)
  • Botulinum toxin
    = blocks acetylcholine vesicle release process through the enzymatic removal of two amino acids from one or more of the fusion proteins)
  • Receptor agonists and antagonists
  • Inhibitors of acetylcholine esterase (acetylcholine is not inhibited)
24
Q

How are the different cholinergic drugs classified?

A
  • Drugs affecting muscarinic (mAChR) and nicotinic (nAChR) receptors:
    ~ Choline esters (directly acting)
    ~ Anticholinestertase drugs (indirectly acting)
  • Drugs affecting muscarinic receptors (mAChR):
    • Muscarinic agonists
    • Muscarinic antagonists
  • Drugs affecting nicotinic receptors (nAChR):
    • Nicotinic agonists
    • Nicotinic antagonists (neuromuscular-blocking drugs, muscle relaxants)
  • Drugs inhibiting acetylcholine release
25
Q

What drugs can be used to treat glaucoma?

A
  • Cholinoreceptor-activating drugs
    = carbachol

(more possibilities)

26
Q

How are the cholinesterase inhibitors (ChEI) classified?

A

1) With a quaternary ammonium group (N+)
- Neostigmine
- Pyridostigmine

  • Poor absorption:
    ◦ Much higher doses are required for oral
    administration than for parenteral injection
  • Do not cross the BBB
2)With a tertiary ammonium group
• Galantamine
• Donepezil
• Rivastigmine
- Good absorption
- Cross the BBB
• Organophosphates (insecticides,
chemical warfare “nerve gases”)
- Good absorption from the GIT,
lungs, skin, and conjunctiva
- Heavy poisoning
27
Q

What is the pharmacokinetics of cholinesterase inhibitors- with a quaternary ammonium group?

A

1) With a quaternary ammonium group (N+)
- Neostigmine
- Pyridostigmine

  • Poor absorption:
    ◦ Much higher doses are required for oral
    administration than for parenteral injection
  • Do not cross the BBB
28
Q

What is the pharmacokinetics of cholinesterase inhibitors- with a tertiary ammonium group?

A 
2)With a tertiary ammonium group
• Galantamine
• Donepezil
• Rivastigmine
- Good absorption
- Cross the BBB
• Organophosphates (insecticides,
chemical warfare “nerve gases”)
- Good absorption from the GIT,
lungs, skin, and conjunctiva
- Heavy poisoning
29
Q

What is the mechanism of action of ChEIs?

A
  • potentiate the actions of the endogenous ACh
30
Q

What are the M-cholinomimetic effects of ChEIs?

A

•M-cholinomimetic (muscarinic) effects:
◦ Eye: myosis, accommodation, ↓IOP
◦ Heart: bradycardia, ↓ AV conductance
◦ RS: Contraction of the smooth muscle of the bronchial
tree and increased secretion of bronchial glands
◦ GIT: stimulation of salivary glands, increased acid secretion, increased
secretion of intestinal glands, increased motor activity of the gut, sphincter relaxation
◦ Urinary bladder: stimulation of the detrusor muscle,
relaxation of the sphincter, thus promotion of voiding

31
Q

What are the N-cholinomimetic effects of ChEIs?

A

◦ Depolarization of the endplates – increased contraction of the
skeletal muscle

32
Q

What are the CNS effects of ChEIs?

A

only the lipid-soluble part
◦ In low concentrations – Activation of the EEG
◦ In higher concentrations – Generalized convulsions ->
coma and respiratory arrest

33
Q

What are the clinical uses of ChEIs?

A
  • Glaucoma
  • Postoperative ileus (atony and paralysis of the stomach and bowel
    following surgical manipulation)
  • Urinary retention
    ◦ Postoperative atony
    ◦ Postpartum
    ◦ Secondary to spinal cord injury
  • Myasthenia gravis
  • Curare-induced neuromuscular paralysis (overdose of nondepolarizing neuromuscular junction blockers)
  • Atropine intoxication (Galantamine)
  • Alzheimer’s disease (Donepezil, Rivastigmine)
34
Q

What are the contraindications and toxicity of ChEIs?

A

Contraindications
◦ Ulcer disease
◦ Bronchial asthma
◦ Obstructive ileus

Toxicity
◦ Eye: myosis
◦ Glands: sweating
◦ GIT: salivation, vomiting, diarrhea
◦ CVS: bradycardia, AV block, hypotension
◦ RS: bronchoconstriction
◦ Depolarizing neuromuscular blockade: paralysis

Treatment of the intoxication:
◦ Atropine
◦ Obidoxime

35
Q

What are muscarinic agonists, what is their mechanism of action, and clinical use?

A

Drug:
◦ Pilocarpine – plant
alkaloid

Mechanism of action:
◦ Agonist of М receptors (direct
interaction)

Clinical use:
◦ For decrease of IOP

36
Q

What are muscarinic antagonists?

A

Natural alcaloids:
◦ Atropine (from Atropa belladonna)
◦ Scopolamine (Hyoscine) (from Datura stramonium)

Drugs:

Natural
◦ Atropine
◦ Scopolamine

Semi-synthetic
◦ Butylscopolamine

Synthetic
◦ Mydriatics
Cyclopentolate

◦ Bronchospasmolytics
Ipratropium
Tiotropium

◦ Urospasmolytics
Oxybutynin
Solifenacin
Darifenacin (selective for M3 receptors)

37
Q

What is the pharmacokinetics of atropine?

A

Good oral absorption and absorption through the conjunctiva

Good tissue distribution

Short t1/2 ~ 2 h

Renal excretion ~ 60% unchanged

Effect in the eye >72 h

38
Q

What are the effects of atropine on the eye, heart, RS, and digestive system?

A

Eye:
• Mydriasis (duration: days)
• Cycloplegia (paralysis of the ciliary muscle resulting in a loss of accommodation)
• ↑ IOP (dangerous in glaucoma)
• Reduction of lacrimal secretion (dry or “sandy” eyes)

Heart:
• SA node: tachycardia
• Improvement of AV conductance

RS:
• Bronchial muscle: relaxation
• Bronchial glands: ↓ secretion

Digestive system:
• Stomach and intestines: ↓ motility, spasmolytic effect
• Gallbladder and biliary ducts: spasmolytic effect
• Glands: ↓ secretion of salivary glands (xerostomia, dry mouth) > intestinal glands >
gastric glands

39
Q

What are the effects of atropine on the genitourinary tract, CNS, and sweat glands?

A

Genitourinary tract:

  • Urinary bladder: relaxation of the bladder wall – slow
  • Ureters: relaxation of the smooth muscle, spasmolytic effect
40
Q

What are the indications for atropine?

A

In ophthalmology:
◦ For pupil dilation (mydriasis)
◦ For accurate measurement of refractive error in
young children (loss of accommodation)

For treatment of sinus bradycardia, e.g. acute MI

As a spasmolytic agent for gastro-intestinal, biliary and
renal colics

As a premedication in general surgery (↓ bronchial
secretion)

For the treatment of poisoning with:
◦ Organophosphates (large doses!)
◦ Mushrooms:
◦ Amanita muscaria
◦ Amanita phalloides
41
Q

What are the adverse effects, toxic effects, and contraindications of atropine?

A 
Adverse effects:
◦ Dry mouth (xerostomia)
◦ Constipation
◦ Blurred vision
◦ Tachycardia
Тoxic effects:
◦ CNS: agitation, delirium
◦ Hot and flushed skin
◦ Elevated body temperature
“dry as a bone, blind as a bat, red as a beet, mad as a hatter”

Contraindications:
◦ Glaucoma
◦ Benign prostatic hyperplasia

42
Q

What is scopolamine?

A 
Muscarinic antagonist - plant origin
Scopolamine (hyoscine)
◦ Sedation
◦ Antiemetic effect (М-rec. in the
vestibular apparatus and in the
vomiting center)
◦ For motion sickness (kinetosis)
43
Q

What are Ipratropium and Tiotropium?

A

Muscarinic antagonist - synthetic drugs -> bronchospasmolytics

Ipratropium, Tiotropium
◦ Bronchodilatatory effect, for
inhalation
◦ Treatment of bronchial asthma
and COPD
44
Q

What is Butylscopolamine?

A

Muscarinic antagonist - semi-synthetic drug

Butylscopolamine
◦ A derivative of scopolamine with
a quaternary ammonium group
◦ Spasmolytic action
◦ For gastrointestinal, biliary and
renal colics
45
Q

What is cyclopentolate?

A

Muscarinic antagonist - mydriatics

causes Mydriasis

46
Q

What are oxybutynin, solifenacin, and darifenacin?

A

Muscarinic antagonists - urospasmolytics

Oxybutynin, Solifenacin,
Darifenacin
◦ Relaxation of the urinary bladder
◦ For the treatment of urinary
incontinence in adults
47
Q

What are the drugs affecting nicotinic receptors (nAChR)?

A

Agonists of nicotinic receptors
◦ Nicotine, Cytisine
◦ Usage:
◦ For smoking cessation

48
Q

What are neuromuscular blocking drugs? - Non-depolarizing

A 
Antagonists of nicotinic receptors
◦ Ganglion-blocking drugs
◦ Not used nowadays in Bulgaria
◦ Neuromuscular blocking drugs
◦ Non-depolarizing
Pipecuronium
Atracurium
49
Q

What are neuromuscular blocking drugs? - Depolarizing

A

Antagonists of nicotinic receptors
◦ Ganglion-blocking drugs
◦ Not used nowadays in Bulgaria

Depolarizing
Suxamethonium

Pharmacology (35 decks)

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