Peripheral Nervous System Flashcards
(19 cards)
How can altering a drug target’s function help treat disease?
Drugs can enhance or inhibit target functions to restore balance in disease states
What are the two branches of the Peripheral Nervous System?
Somatic - Controls voluntary movement (skeletal muscle)
Autonomic - Controls involuntary functions (cardiac, digestion)
What is the neuromuscular junction (NMJ?)
A synapse where motor neuron transmits signals to skeletal muscle via acetylcholine (ACh)
What are the key steps in synaptic transmission at the NMJ?
1 - Choline uptake into the nerve terminal
2 - ACh synthesis and packaging into vesicles
3 - Action potential arrival, leads to depolarisation
4 - Calcium channel activation, triggers vesicle function
5 - ACh release and receptor binding at muscle membrane
6 - Muscle depolarisation -> Contraction
7 - AChE breakdown of ACh, stopping the signal
What are drug targets at the NMJ?
- Nicotinic ACh receptors -> Influence depolarisation (agonists/antagonists)
- Acetylcholinesterase (AChE) -> Inhibitors prevent breakdown, prolonging signal transmission
What causes Myasthenia Gravis?
Autoimmune depletion of nicotinic ACh receptors leads to weak muscle contraction
What are symtpoms of Myasthenia Gravis?
Muscle weakness and fatigue
Drooping eyelids (in humans)
Weak mouth (in dog)
How is Myasthenia Gravis treated?
AChE inhibitors (neostigmine, physotigmine) –> Increase ACh avaliability at synapse
How do muscle relaxants work?
Block ACh transmission at NMJ –> Prevent muscle contractions (e.g., tubocurarine)
What is tubocurarine and how was it historically used?
- Found in Amazon blowgun poison (“tube curare”)
- Paralyses prey when entering the bloodstream but harmless if ingested
How does botulinum toxin affect NMJ transmission?
- Blocks vesicle fusion and ACh release, preventing muscle contractions
- Clinical uses: Muscle spasm relief, urinary incontinence, cosmetic injections
What are the differences between the somatic and autonomic nervous system?
- Somatic: Voluntary control, single neuron, ACh -> nicotinic receptors
- Autonomic: Involuntary control, ganglia, ACh or noradrenaline (NA)
What are the two branches of the autonomic nervous system?
Sympathetic (Fight or flight) - Increase heart rate, dilates pupils
Parasympathetic (rest and digest) - Lowers heart rate, stimulates digestion
What are the primary neurotransmitters in the ANS?
Acetylcholine (ACh)
Noradrenaline (NA)
What recepors do these neurotransmitters target?
Nicotinic ACh receptors -> Autonomic ganglia (neuronal communication)
Muscarinic ACh receptors -> Parasympathetic effectors (GPCRs)
Adrenoreceptors -> Sympathetic effectors (GPCRs)
How does receptor specificity impact drug targeting?
Muscarinic receptors (M1-M3) -> Pharmacologically indistinct, requiring selective drug delivery
Adrenoreceptors -> Distinct tissue distribution, allowing targeted drugs
What drugs act on parasympathetic system?
Pilocarpine (mACh agonist) -> Treats glaucoma (reduces eye pressure)
Atropine (mACh antagonist) -> Used in anaesthesia (prevents heart rate slowing)
What drugs act on the sympathetic system?
Phenylephrine (α1 agonsit) -> Decongestant, dilates pupils
Atenolol (β1 antagonist) -> Lowers blood pressure, reduces heart rate
Salbutamol (β2 agonist) -> Treats asthma (bronchodilation)
What are the key drug targets in the PNS?
NMJ -> Treat uscle disorders
Autonomic receptors -> Regulate heart rate, digestion, blood flow
Selective targeting -> More effective with sympathetic adrenoreceptor drugs due to distinct receptor distribution
