Exocytosis Regulated Secretion Ca2+ triggered Vesicle Neurotransmitter Release · 1952- Katz- used a microelectrode to record from the neuromuscular junction- which is where motor nerves stimulate voluntary muscles. When the nerve isn't stimulated- he observed small fluctuations across the membrane of the muscle fibre- Always the same size or multiple of thar size · neurotransmitters are released in packets. . when an action potential arrives at the junction- around 100 packets are released at once. · Voltage gated calcium channels open- which trigger vesicles to fuse w/ the membrane. Golgi apparatus Neurotransmitters First neurotransmitter- acetylcholine . Otto Loewi 1921- Acetyl Choline (Ach) - main neurotransmitter- is secreted by many nerves in the autonomic NS · Synthesised from 2 common chemicals- Acetate & Choline. · After release - Ach is broken down by the enzyme Acetylcholinesterase. Receptors Neurotransmitters · 2 main types of cholinergic receptor- nicotinic & Muscarinic · Acetylcholine · Peptides · Amino Acids - Opioids - Gamma Amino Butyric Acid (GABA) - Vasopressin . These 2 receptors are named after 2 substances which bind to those receptor subtypes. - Glutamate - Oxytocin · Monoamines - Substance P Nicotine binds to nicotinic- but not to muscarinic receptors Catecholaminos Etc. Synaptic · Dopamine · Noradrenaline (Norepinephrine) · This isn't a complete list! . Muscarinic receptors are named after Muscarine. Transmissiotylcholine binds to both receptor types. - Indoleamine: Serotonin (5 Hydroxytryptamine, 5HT) Nicotinic Receptors n · Nicotinic receptors are at the neuromuscular junctions- found in small numbers in the CNS . They're ionotropic receptors (directly coupled to an ion channel) Muscarinic Receptors · These receptors in the parasympathetic nervous system are . At the Neuromuscular junction- nicotinRemoval of the neuro EPSRaisindd B&Ps receptors allow positively charged sodium ions into the cell Neurotransmitters bind When this type of receptor is activated one unit of a protein open ion channels the removed from the synaattached to the receptor breaks away inside the cell. This effect may be to depolarise of hyperpolarise the cell. Breakdown by enzymesactivates a separate ion channel elsewhere in the membrane. membrane potential becomes more ne most common type of ACh receptor in the CNS. In other the cell is hyperpolarised and less likely to fire: an · This depolarises the cell- producing an excitatory effect. A neurotransmitter, Neurotransmitter receptor site Neurotransmitter attaches to receptor the ligand, is required to open the ion channel . Acetylcholine Metabotropic receptors the alpha-subunit acti . Monoamine oxidase brengibitony Post Synaptic Potential or IPSP Channel closed Extracellular fluid enzyme, which in turn produces a secondary messenger If the membrane potential becomes less negative, the Stages of Synaptic Trarwhich opens an ion channel ACh Na* -Ca ?- a * concentration gradient cell is more likely to fire: An Excitatory Post-Synaptic which mediated the effect Loewi studied opened a channel Potential or EPSP. anfowine positively charged potassiumvions to leave the cen "At the neuromuscular junctiona single postsynaptic This hyperpolarises the cell, producing an inhibit ory effect. Neurotpotentialcan trigger an action potential. At synapses re-uptan the ONS numerous