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Drugs of the Peripheral Nervous System

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Presentation on theme: "Drugs of the Peripheral Nervous System"— Presentation transcript:

1 Drugs of the Peripheral Nervous System

2 The Nervous System Review

3 Organization of the Nervous System
Central nervous system (CNS) Brain and spinal cord Peripheral nervous system (PNS) Neurons outside the CNS Sensory division Afferent fibers transmit impulses from receptors to CNS Motor division Efferent fibers transmit impulses from CNS to effector organs

4 Relationship between motor and sensory fibers of the PNS and the CNS

5 Autonomic Nervous System
Sympathetic Fight or flight, stress Excitatory effects elicited by norepinephrine activating beta receptors Inhibitory effects elicited by activation of alpha receptors

6 Parasympathetic Rest and digest
Digestive system activated, heart rate inhibited, blood vessels dilated Vagus nerve primarily responsible for activating parasympathetic responses

7 Fig. 8.39

8 Autonomic Neurotransmission
Two neurons Presynaptic and postsynaptic Presynaptic from the brain to autonomic ganglia Acetylcholine released from prenaptic neuron across synapse to activate postsynaptic neuron Postsynaptic neurons release norepinephrine (sympathetic) or acetylcholine (parasympathic) at the effector organ

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10 The Synapse Fig. 8.13

11 Neurotransmitters --packaged in synaptic vesicles.
Nerve endings of the ANS secrete: Acetylcholine (ACh)--Cholinergic neuron Parasympathetic effector Norepinephrine (NE)--Adrenergic neuron Sympathetic effector

12 If stimulatory, Na+ channels will open
Neurotransmitters diffuse across the synaptic cleft and bind to receptor on the post-synaptic membrane This can cause membrane channels (Na+, K+, or Cl-) to open or close depending on the neurotransmitter If stimulatory, Na+ channels will open If inhibitory, K+ or Cl- channels will open Cell becomes more negative, hyperpolarized

13 Catecholamines Norepinephrine and epinephrine
Norepinephrine primarily neurotransmitter Epinephrine primarily hormone Primarily concerned with sympathetic transmission Released at synaptic cleft and bind to alpha or beta receptors

14 Acetylcholine Responsible for all parasympathetic neurotransmission
Binds to mucarinic receptors at the end organ

15 Ganglionic transmission
Transmits both parasympathetic and sympathetic preganglionic signals to nicotinic receptors (Nn) All ganglionic transmission is cholinergic (acetylcholine) Drugs that block ganglionic transmission block either parasympathetic or sympathetic depending on which is active This is a paradox many have a problem grasping

16 Fig. 8.39

17 Neuromuscular transmission
Somatic motor neurons release acetylcholine at neuromuscular junction Acetycholine diffuses across synapse and binds to muscular nicotinic receptors (Nm) causing sodium influx

18 The Neuromuscular Junction

19 Central Neurotransmission
Acetylcholine the primary neurotransmitter in the brain Works by interaction with muscarinic receptors

20 Neurotransmitter degradation
Neurotransmitters which fail to bind to a post-synaptic receptor are degraded by enzymes (acetylcholinersterase) Taken up into the presynapse and recycled Diffuse out of the synapse

21 Receptors 2 types of cholinergic receptors: Nicotinic Muscarinic
Preganglionic sympathetic and parasympathetic (Nn) Also neuromuscular somatic motor (Nm) Muscarinic parasympathetic 2 types of adrenergic receptors: Alpha Generally inhibitory Beta Generally excitatory

22 Neurotransmission Enhancers
Receptor agonists Compound which bind to the receptor and activate Can be cholinergic or adrenergic Agents which induce neurotransmitter release Stimulate release of neurotransmitter in absence of signal (or reduced signal) Inhibitors of neurotransmitter degradation Inhibit acetylcholinersterase

23 Neurotransmission Inhibitors
Presynaptic nerve blockerss Receptor antagonists Bind to receptor and prevent activation Ganglion blockers

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