Cholinergic Pharmacology Flashcards
What does afferent mean
Carries signal toward the brain or spinal cord
What does efferent mean
Carries signal away from the brain or spinal cord
Adrenergic definition
relating to adrenaline or noradrenaline and their receptors
Cholinergic definition
relating to acetylcholine and its receptors
Somatic v Autonomic NS
Somatic - single neurone between CNS and skeletal muscle
Autonomic = two neuron chain, leads to excitation or inhibition
Ganglionic chain structure in sympathetic system
The ganglion is within a chain adjacent to the spinal cord
(Short pre-ganglionic fibre, long post-ganglionic fibre)
Ganglionic chain structure in parasympathetic system
The ganglion is within or very close to the effector organ - long pre-ganglionic fibre, short postganglionic fibre
What receptors do both sympathetic and parasympathetic fibres act on the pre-ganglionic receptor
Ach acts on nicotinic receptor
What receptors do the parasympathetic fibres act on the post ganglionic receptor
Ach on muscarinic receptors
What receptors do the sympathetic fibres ac on the post ganglionic
Adrenaline on alpha beta-adrenergic receptor
Exceptions to the receptor rule
Sometimes Ach is released at sympathetic postganglionic termini (e.g., sweat glands)
Nitric oxide - is released from parasympathetic postganglionic termini in blood vessels
Cholinergic receptor examples
Nicotinic receptors - stimulates the sympathetic and parasympathetic nervous system
Muscarinic receptors - stimulates the parasympathetic nervous system. These M receptors are receptive to drug targeting
Types of muscarinic receptors and where are they found
M1: Brain
M2: Heart - their activation slows the heart, so we can block these
M3: Lungs + All organs with parasympathetic innervation
M4: Mainly CNS
M5: Mainly CNS
All are found outside the cell and activate intracellular processes through G proteins
How do M2 receptors work?
Activation of M2 on heart SA node - decreases heart rate
Activation of M2 on heart AV node - decreases conduction velocity, induces AV node block (increases PR interval)
How do M3 receptors work?
Respiratory system - produces mucus (airways and nasopharynx) and induces smooth muscle contraction (bronchoconstriction)
GI tract - increases saliva production, increases gut motility, stimulates biliary secretion
Skin - only place where sympathetic systemic releases Ach. causes sweating
Urinary system - contracts detrusor muscle, relaxation of internal urethral sphincter
Eye - causes myosis, increases drainage of aqueous humour, secretion of tears
Example of M3 agonist
Pilocarpine eye drops
- increases drainage of aqueous humour
- reduces ocular pressure
- treats acute (closed angle) glaucoma
- also used to treat dry mouth
Example of M3 antagonist
Hyoscine - used in palliative care to treat respiratory secretions and symptoms of bowel obstruction
Role of inhaled antimuscarinic and example
Bronchodilation
e.g., Tiotropium
Side effects of inhaled antimuscarinics
Dry mouth,
Urinary retention
Can worsen existing glaucoma
Other examples of antimuscarinics
Solifenacin - treatment for overreactive bladder = inhibits smooth muscle contraction
Meberevine - IBS - slows contractility in the gut
ACh outside the ANS - CNS
ACh also used in CNS receptors and implicated in memory
- therefore anticholinergics (antimuscarinics) can cause memory problems
Antiemesis - hyoscine can be used for nausea
ACh outside the ANS - Somatic nervous system
Botulinum prevents Ach release - causes flaccid paralysis and death from respiratory muscle involvement - treat painful muscle spasms or BoTox cosmetically
Role of Nicotinic (N1) receptor blockers in somatic nervous system
Inhibit Ach activity
Rocuronium, suxamethonium , pancuronium = used as muscle relaxants in surgery
What is myasthenia gravis
The blockage of normal transmission of Ach leads to skeletal muscle weakness
Most notable on related attempts at movement
Treatment includes anti-cholinesterase (pyridostigmine) to increase Ach availability at neuromuscular junction.
Overstimulation of ACh at neuromuscular junction leads to…
CHOLINERGIC CRISIS (SLUDGE)
- Salivation
- Lacrimation
- Urination
- Defecation
- GI distress
- Emesis
Parasympathetic ACh
Rest and digest
Pupils constricts
Decreased HR
BronchoCONSTRICTION
Increased GI motility and secretion
Bladder contraction (detrusor)
Penis Points (erect)
Sympathetic NAd
FIGHT OR FLIGHT
Pupils dilate
Increased HR
BronchoDILATION
Decreased GI motility + secretion
Detrusor relaxes
Penis shoots (ejaculation)
