Lecture 14 Synapse and Neurotransmitters (2) PDF

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102  PASSIVE TRANSPORT ASHRAF ALGENDY By: PROFESSOR MEDICAL PHYSIOLOGY Department: 12/11/2024...

Faculty of Medicine Academic Year: 2024-2025 Year: 1 Semester: 1 Module: Human Body Function (HBF) 102  PASSIVE TRANSPORT ASHRAF ALGENDY By: PROFESSOR MEDICAL PHYSIOLOGY Department: 12/11/2024 22  OBJECTIVES At the end of the lecture you will be able to: Clarify the concept of synapse. List different classification of synapse. Describe mechanism of synaptic transmission. 12/11/2024 HBF - 102 5  OBJECTIVES At the end of the lecture you will able to: List different types of autonomic neurotransmitters. List different autonomic sites that release acetyl choline. List different autonomic sites that release catecholamine. 12/11/2024 HBF - 102 6  AUTONOMIC NEUROTRANSMITTERS Human body functions Electrochemical Events (Phenomena)  Synapse It is a communication between a neuron and another structure Neuronal Neuroglandular Neuromuscular Axodendritic Axosomotic Axoaxonic  Synapse Neuronal Neuroglandular Neuromuscular Axodendritic Axosomotic Axoaxonic  1-Neuronal Axodendritic Axosomotic Axoaxonic Neuroglandular  Synapse Electrical Chemical Conjoined Mechanism of synaptic transmission Which of the following process that describe the release of chemical transmitter: 1-active transport that need Ca and docking proteins. 2-active transport that need pump and tow carriers. 3-passive transport that need pump and a channel. 4-passive transport that need carrier and calcium. 5-passive transport that need Ca and docking carrier. - Which of the following statement is true: 1-chemical synapse is the commonest type in human body. 2-chemical synapse is bidirectional pathway among neurons 3-conjoined synapse is the commonest type in human body. 4-electrical synapse is the commonest type in human body.. 5-electrical synapse is unidirectional pathway among neurons.  Autonomic Neurotransmitters Autonomic neurons Cholinergic Non-cholinergic Adrenergic neuron non-adrenergic neuron VIP, NO, Acetylcholine Morphine Noradrinaline GIP , Others ACETYLCHOLINE (VAGUSTOFF) Otto Loewi (1873-1961) Austrian scientist. 1921: discover chemical mediated signal of vagus nerve (Vagustoff) 1936 : Share Noel price with Henry Hallett Dale  Otto Loewi dream “The night before Easter Sunday of I awoke, turned on the light and jotted down a few notes on a tiny slip of thin paper. Then I fell asleep again. It occurred to me at 6.00 o’clock in the morning that during the night I had written down something important, but I was unable to decipher the scrawl. The next night, at 3.00 o’clock, the idea returned. It was the design of an experiment to determine whether or not the hypothesis of chemical transmission that I had uttered 17 years ago was correct. I got up immediately, went to the laboratory, and performed a simple experiment on a frog heart according to the nocturnal design. Henry Hallett Dale (1875-1968) British scientist. 1921: discover acetylcholine. 1936 : Share Noel price with Otto Loewi Structure of acetylcholine Synthesis Sites of release Cholinergic receptors Mechanisms of action Fate of acetylcholine  STRUCTURE Synthesis Sites of release Cholinergic receptors Mechanisms of action Fate of acetylcholine Structure of acetylcholine SYNTHESIS Sites of release Cholinergic receptors Mechanisms of action Fate of acetylcholine Structure of acetylcholine Synthesis SITES OF RELEASE Cholinergic receptors Mechanisms of action Fate of acetylcholine  Sites of release of acetylcholine We divide autonomic efferent neurons into: 1-Central neuron: it is a neuron that arise from CNS. 2-Peripheral neuron: it is a neuron that arise from autonomic motor ganglions.  Sites of release of acetylcholine All central neurons release acetylcholine All parasympathetic release acetylcholine All sympathetic postganglionic release noradrenaline except that supply eccrine sweat gland and blood vessel of skeletal muscle, release acetylcholine Sites of release  Sites of release of acetylcholine Preganglionic parasympathetic neurons Preganglionic sympathetic neurons Postganglionic parasympathetic neurons postganglionic sympathetic to eccrine sweat gland and blood vessels of skeletal muscle nerve to adrenal medulla Nerve to skeletal muscle Enumerate sites of release of acetylcholine in autonomic efferent system? List 5 autonomic neurotransmitters? Which of the following neurons can release noradrenaline: 1-postganglionic sympathetic that supply blood vessels of skeletal muscle. 2-preganglionic sympathetic that supply lacrimal glands. 3-postganglionic sympathetic that supply eccrine sweat glands. 4-postganglionic sympathetic that supply apocrine sweat glands. 5-preganglionic sympathetic that supply salivary glands. Which of the following postganglionic neuron can releases acetylcholine: 1-post ganglionic sympathetic that supply apocrine sweat gland. 2.Postganglionic sympathetic that supply eccrine sweat gland 3-postganglionic sympathetic that supply gastrointestinal tract. 4-postganglionic sympathetic that supply cardiovascular system 5-postganglionic sympathetic that supply erector pile muscle. Structure of acetylcholine Synthesis Sites of release Cholinergic receptors Mechanisms of action Fate of acetylcholine  Cholinergic receptor It is a receptor that binds and responds to acetylcholine. It has tow types: Nicotinic receptor and muscarinic receptor.  Cholinergic receptor Presynaptic receptor is located on the terminal of presynaptic neuron. E.g..: M2 receptor.(autoinhibition ) Postsynaptic receptor is located on dendrites, cell body or axon of postsynaptic neuron. N.B.: when acetylcholine binds with presynaptic M2 receptor, it inhibits excess release of acetylcholine AUTOINHIBITION Mechanisms of Action N.B.: when acetylcholine binds with presynaptic M2 receptor, it inhibits excess release of acetylcholine AUTOINHIBITION  Cholinergic receptors Nicotinic Muscarinic M1 M3 M5 Nn NM M2 M4 Cholinergic receptor Smooth CNS CNS Heart CNS muscle Structure of acetylcholine Synthesis Sites of release Cholinergic receptors Mechanisms of action Fate of acetylcholine  Fate of acetylcholine As acetyl choline is released and perform its physiological action, it is rapidly hydrolysed to choline and acetic acid by: True(specific) cholinesterase, it present at every site release acetylcholine Pseudo(nonspecific) cholinesterase, it present in plasma and at the tissues  Fate of acetylcholine Breakdown of acetylcholine is essential to prevent its generalised effect which is fatal. Can you predict what is happen if we block cholinesterase enzymes all over the body. CATECHOLAMINES Structure of catecholamine Synthesis Sites of release Adrenergic receptors Mechanisms of action Fate of catecholamine  STRUCTURE Synthesis Sites of release Adrenergic receptors Mechanisms of action Fate of catecholamine CATECHOL DOPAMINE NORADRENALINE ADRENALINE Structure of acetylcholine SYNTHESIS Sites of release Adrenergic receptors Mechanisms of action Fate of catecholamine In the liver: Phenylalanine is converted into Tyrosine  Inside adrenergic neuron: Tyrosine is converted into noradrenaline(norepinephrine. In adrenal medulla: Noradrenaline(norepinephrine) is converted into adrenaline(epinephrine) Structure of acetylcholine Synthesis SITES OF RELEASE Adrenergic receptors Mechanisms of action Fate of catecholamine Sites of release of catecholamine  Sites of release of noradrenaline All postganglionic sympathetic except that supply eccrine sweat gland and blood vessels of skeletal muscle Adrenal medulla Some neurons inside CNS.  Sites of release of adrenaline Adrenal medulla Some neurons inside CNS. Structure of catecholamine Synthesis Sites of release Adrenergic receptors Mechanisms of action Fate of catecholamine  Adrenergic receptor It is a receptor that binds and responds to adrenaline and noradrenaline. It has tow types: alpha receptor and beta receptor.  Adrenergic receptors Presynaptic receptor is located on the terminal of presynaptic neuron. E.g..: alpha 2 receptor.(autoinhibition ) Postsynaptic receptor is located on dendrites, cell body or axon of postsynaptic neuron.  Adrenergic receptors Alpha Beta 1 2 3 1 2 Cholinergic receptor Adipose tissues bronchioles heart  Alpha RECEPTORS Alpha 1 Alpha 2 when noradrenaline binds with presynaptic alpha 2 receptor, it inhibits excess release of its release. AUTOINHIBITION NEGATIVE FEEDBACK INHIBITION Structure of catecholamine Synthesis Sites of release Adrenergic receptors Mechanisms of action Fate of catecholamine  Fate of catecholamine Active reuptake : the main mechanism Oxidation by MonoAmine Oxidase(MAO) Methylation by catechol-ortho-methyl transferase (COMT)