Test 2 Parasympathetic Nervous System Flashcards
“fight or flight”
sympathetic nervous system
“rest and digest”
parasympathetic nervous system
Parasympathomimetic
Drug that stimulates the parasympathetic nervous system
Parasympatholytic
Drug that blocks the parasympathetic nervous system
Where does the parasympathetic nervous system originate?
In the central nervous system at the craniosacral region of the spinal cord
Cranial nerves: 3, 7, 9, 10
Sacral spinal segments: S2 - S4
Parasympathetic preganglionic neurons are __________
and postganglionic neurons are __________
Preganglionic are LONG
Postganglionic are SHORT
in the parasympathetic nervous system
The predominate neurotransmitter at the terminal synapses of
parasympathetic neurons
Acetylcholine (cholinergic)
The two major cholinergic (acetylcholine) receptors of the
parasympathetic nervous system
are
Muscarinic Recceptors
Nicotinic Receptors
This receptor of the parasympathetic nervous system
is present at all ganglionic and somatic synapses
Nicotinic receptors
This receptor of the parasympathetic nervous system
is found on only the target tissues of the parasympathetic nervous system
Muscarinic receptors
The 3 EXCITATORY
Muscarinic Receptors of the parasympathetic nervous system
M1
M3
M5
Receptor of the parasympathetic nervous system
that is
Excitatory
Neural (CNS stimulation, gastric acid secretion, increased GI motility)
M1
Receptor of the parasympathetic nervous system
that is
Excitatory
Glandular (secretions, smooth muscle contraction, vasodilation)
M3
Receptor of the parasympathetic nervous system
that is
Excitatory
Salivary glands, iris
M5
The receptor of the parasympathetic nervous system
that is
Inhibitory
Cardiac (and neural inhibition)
M2
The receptor of the parasympathetic nervous system
that is
Inhibitory
CNS/Smooth muscle
M4
When **acetylcholine **is released at the ganglia
It stimulates the post-synaptic neuron to carry on the action potential
When **acetylcholine **is released at the neuromuscular junction
It stimulates muscle contraction
When acetylcholine is released at the CNS, it can cause
convulsions
When acetylcholine is released at a parasympathetic terminal synapse with the
target organ, it will facilitate ____________ signs
Muscarinic signs
Diarrhea
Urination (smooth muscle contraction)
Miosis
Bradycardia (slowing of heart)
Bronchoconstriction
Emesis (increased GI motility)
Lacrimation
Salivations (increases secretions)
Drugs that cause the same response as acetylcholine
that interact directly with post-synaptic receptors
Muscarinic agonists
will cause muscarinic signs
Diarrhea, Urination, Miosis,
Bradycardia, Bronchoconstriction, Emesis,
Lacrimation, Salivation
What are the direct acting
parasympathomimetics?
Bethanechol
Pilocarpine
- will cause muscarinic signs*
- DUMBBELS*
What are the indirect-acting
parasympathomimetics
that are reversible?
Neostigmine
Pyridostigmine
Edrophonium
Physostigmine
Demarcarium
- These impair the function of acetylcholinesterase, so acetylcholine cannot be*
- bound or broken down. These will have muscarinic effects*
Oral medication
Tx of urinary disorders
(associated with spinal injury) (lower motor neuron bladder dysfunction)
Muscarinic agonist
M3 selectivity (excitatory-glandular: secretion, smooth muscle cont. vasodilation)
Stimulates detrusor muscle contraction
Bethanechol
only used if urethra is patent (no obstruction)
Ophthalmic medication
Used to *stimulate miosis *to decrease intraocular pressure
or to localize the cause of anisocoria
Pilocarpine
should not be used if anterior uveitis or lens luxation
Impairs the function of acetylcholinesterase
Approved in cattle, horses, pigs, and sheep
Injection med
ARCI Class 3
Tx of rumen atony
Used to stimulate intestinal motility in horses
Can be used to reverse competitive NMBs
Neostigmine
Longer duration than Neostigmine
Impairs the function of acetylcholinesterase
Used to Tx myasthenia gravis in small animals
Pyridostigmine
Very short acting anticholinesterase
Used in the Dx of myasthenia gravis
Used to differentiate between *myasthenic crisis *and cholinergic crisis
Requires a “crash cart” with atropine on hand when testing
Edrophonium
Topical ophthalmic drug
Used to induce miosis that will last 12 hours
Used systemically to Tx Ivermectin toxicity in dogs
Used to Dx narcolepsy in dogs and horses
Unlike other cholinesterase inhibitors, it WILL cross the BBB
Physostigmine
Should not be used if anterior uveitis or lens luxation
An anticholinesterase drug
A topical ophthalmic drug
Used to induce miosis in the management of glaucoma
Demarcarium
Toxicity that induces
Muscarinic signs –> Nicotinic Excitement (muscle tremors, CNS excitement)–> Nicotinic blockade
Carbamate Insecticide Toxicity
involves a very high dose, WILL cross the BBB
Echothiophate Iodide
and
Organophosphate Insecticides
are both
Irreversible INDIRECT acting parasympathomimetics
Topical ophthalmic drug
Not used clinically very often
Can undergo “aging”
Induced miosis that will last 12 hours, decreases intraocular pressure
Echothiophate iodide
do not use if anterior uveitis or lens luxation
What is the antidote to organophosphate toxicity
2-PAM/ Pralidoxime
can also be treated with atropine
These drugs act as muscarinic antagonists
preventing the action of acetylcholine at PSNS target tissues
Direct Acting ParasympathoLYTICS
A non-specific muscarinic antagonist
Injectable or Ophthalmic
An alkaloid originally extracted from the belladonna plant
Its major actions are antimuscarinic
Most often used to Tx bradycardias
Can be used to Tx OP and Carbamate toxicity
Atropine
- Do not use if glaucoma because will increase intraocular pressure*
- Do not use if pre-existing tachycardia*
- Can cause cycloplegia (blurred vision), panic in horses*
- Severe hypersalivation in cats using ophthalmic formula (very bitter)*
- Rabbits metabolize Atropine VERY quickly, can’t use in rabbits*
A muscarinic antagonist
Injectable form
It is a **quaternary ammonium compound **so it does NOT cross the BBB
Preferred over Atropine in Rabbits
Glycopyrrolate
What is the difference between Atropine and Glycopyrrolate
Atropine crosses the BBB, Glycopyrrolate does not
Glycopyrrolate has a *slower onset *and longer duration than Atropine
Tachyarrhythmias are seen *less frequently *with Glycopyrrolate
Glycopyrrolate is preferred in use in Rabbits
(because they metabolize Atropine very fast)
A direct muscarinic antagonist
Known as a urinary antispasmodic
Used for urinary incontinence due to detrusor hyperreflexia (overactive bladder)
It will relax the detrusor muscle
Not often used in vet med
**Oxybutynin **and Propantheline
A muscarinic antagonist
Topical ophthalmic used as a mydriatic to dilate pupils
Can cause cycloplegia
More rapid onset and shorter duration than ophthalmic atropine
Mostly used to facilitate ophthalmic retinal exams
Tropicamide
Should not use in glaucoma, will increase the IOP
