L1 ANS Flashcards
Autonomic Nervous System
– innervates all tissues except skeletal muscle
– operates outside conscious control
– essential role in homeostasis
Sensory Nervous System
– detects stimuli inside and outside the body
– transmits to specific brain regions for processing
– external stimuli – light, sound, smell, touch, taste
– internal stimuli – O2 concentration, pressure, pH
Somatic Nervous System
– skeletal muscle nervous system
– voluntary movement of skeletal muscle
Name the two neurones synapse in specialised autonomic ganglia
- Preganglionic neurone
– neurone with cell body in CNS - Postganglionic neurone
– neurone with cell body in ganglia
- Preganglionic neurone
- Postganglionic neurone
– neurone with cell body in CNS
– CNS origin is the basis of initial classification of sympathetic and parasympathetic divisions
– neurone with cell body in ganglia
– innervates the target tissue
Sympathetic neurotransmitter release simple
CNS→ganglion→ACh→Nicotinic receptors→postganglionic neuron→Noradrenaline in neuroeffector juction→alpha/beta adrenoceptors
Parasympathetic Neurotransmitter release
CNS→preganglionic neuron→ACh→ganglion/nicotinic receptors→ACh→muscarinic receptors
PNS
Heart
↓ rate (bradycardia)
PNS
Lungs
bronchoconstriction, secretion
PNS
GI tract
↑ tone, motility of small & large intestine, ↑ secretion of saliva and gastric acid
PNS
Glands
↑sweating, salivation, lacrimation
PNS
Eye
sphincter muscle contraction, ciliary muscle contraction
PNS
Blood vessels
most blood vessels not innervated vasodilatation in some vessels
How acetylcholine is formed
Choline + acetyl-Co-enzyme A
|
Choline acetyltransferase
↓
Acetylcholine
Cholinergic Synapse routes of ACh
- Diffuse
- (Might cross synapse but don’t hv to) ACh-esterase →choline (+ acetyl-co-A→ACh
- M2 receptors that will decrease production of ACh
- M3 receptors that will cross the synapse and cause contractions in smooth muscle
In chlinergic veins`
Parasympathomimetic Agents:
- Acetylcholine
- Muscarine
- Nicotine
Parasympathomimetic Agent Acetylcholine
- Nico and Muscar
- Stim those receptors
- Agonist at ganglionic (nico) and postganglionic (mascarinic) receptors
Parasympathomimetic agent: Muscarine
- Alkaloid obtained from Amanita muscaria (toadstool)
- Quaternary ammonium compound
- Resistant to acetylcholinesterase
- Selective for muscarinic receptors (postganglionic)
- Does not stimulate nicotinic (ganglionic) receptors
Parasympathomimetic agent: Nicotine
- No resemblance to either ACh or muscarine
- Selective for nicotinic (ganglionic) receptors
- Does not stimulate muscarinic (postganglionic) receptors
Parasympathetic agent agonist will
Stimulates the receptor
Mimics acetylcholine
Parasympathetic agent antagonist will
Binds to the receptor
Blocks effects of acetylcholine
Parasympathetic agent chonlinesterase inhibitor will
- Inhibits metabolism of acetylcholine
- Acetylcholine levels increase
- Effects of receptor stimulation are potentiated / prolonged
Analogues of ACh
- ACH (M&N) - highly susceptable to ACH Est (+++) [short acting]
- Methacholine (M) - more resistant to ACH Est (+) [longer acting]
- Carbachol (M&N) - resistant to ACH Est (-) [long acting]
- Pilocarpine (M) - resistant to ACH Est (-) [miotic agent ↑ glandular secretion]
Car- NH2
Meth-CH3
Anterior Chamber of the Eye
- response to increased light
- accommodation for near vision
- aqueous humour
Uses of Muscarinic Agonists and open angle glaucoma
- Treats open angle glaucoma where pressure inside eye increases and can cause optic nerve damage
- When pupil is dilated it hinders drainages of aqueous humour
- the iris will fold at an angle and block where the aqueous humour is supposed to drain
- Muscarinic agonist will stim the parasympathetic NS leading to pupil constriction (miosis), opening the drainage angle and aqueous humour flow out of eye more ↓
- Reducing the intraocular pressure.
Uses of Muscarinic Agonists and urinary rentention
- Condition where person cannot empty bladder
- Muscarinic will contraction of bladder muscles helping urination
Uses of Muscarinic Agonists and paralytic Ilieus
- Condition where intestines can’t move food and waste through DT
- Mscarununc receptors in GI tract promote constriction of smooth muscles in intestines to restore bowel movements.
Shouldn’t use muscarinic agnoist if you have what diseases/conditions
- Asthma - bronchoconstriction, hypersecretion of mucus
- Peptic ulcer - ↑gastric acid secretion
- Heart attacks - bradycardia causing coronary insufficiency
- Hyperthyroidism - hypersecretion of thyroid hormone↑↑
ACh-Est and Cholinergic Synapse diagram
- ACh to M/N
- ACh to ACh-est → Choline + acetic acid = taken back up to synthesise more ACh
ACh-Est stucture
- Anionic site for ACh’s N+
- esteratic site for ACh’s ester
Cholinesterase Inhibitors
- Cholinesterase catalyse hydrolysis of Ach
– acetylcholinesterase + pseudocholinesterase - Acetylcholinesterase terminates action of ACh at nerve terminals
- Cholinesterase inhibitors inhibit catalytic activity of cholinesterase enzymes
– ACh accumulates ↑
– neurotransmission increases
Name a short-acting Cholinesterase Inhibitor
Edrophonium
Edrophonium
– combines reversibly with acetylcholinesterase
– effective for only a few minutes
– used to diagnose myasthenia gravis
* skeletal muscle disease
* autoimmune disease affecting the neuromuscular junction
* nico receptors blocked by antibodies
Name two Longer-acting Cholinesterase Inhibitors
- Physostigmine
- Neostigmine
Physostigmine (Calabar bean) and neostigmine do what
- Bind to cholinesterase to form carbamylated intermediate that hydrolyses in min-hrs
- ACh forms acetylated intermediate
- Physostigmine and neostigmine are destroyed in reaction
Therapeutic Uses of Cholinesterase Inhibitors for the eye
- Pupil constricts
- ↓Intraocular pressure in open angle glaucoma
- In cycloplegia will contract ciliary muscle, thicken lens and constric pupil and accommodate for near vision
Therapeutic Uses of Cholinesterase Inhibitors for the Skeletal neuromuscular junction
- Has nicotine receptors
- Reverse paralysis caused by curare-like drugs
- diagnosis and treatment of myasthenia gravis
