an introduction to neurotransmitter system
TRANSCRIPT
Madan BaralB. Pharmacy 3rd Semester
Roll-8
• Identify neurotransmitters• Understand the physiology of neurotransmission• Classify neurotransmitters• Biosynthesis• Major neurotransmitter systems : simple anatomy
and functions
• Neurotransmitters are endogenous chemicals which transmit signals from a neuron to a target cell across a synapse.
• Ramón y Cajal (1852–1934) discovered a 20 to 40 nm gap between neurons, known today as the synaptic cleft.
• In 1921, German pharmacologist Otto Loewi (1873–1961) confirmed that neurons can communicate by releasing chemicals.
• Otto Loewi is accredited with discovering acetylcholine (Ach)-the first known neurotransmitter
• However, some neurons communicate via electrical synapses
How do we identify if a compound is a neurotransmitter?
Chemical can be classified as a neurotransmitter if it meets the following conditions:1.There are precursors or synthesis enzymes located in the presynaptic side of the synapse2.It is available in sufficient quantity in the presynaptic neuron to affect the postsynaptic neuron.3.There are postsynaptic receptors and the chemical is able to bind to them.4.A biochemical mechanism for inactivation is present.
1. Small Molecule transmitters Mono Amines
• Acetylcholine• Serotonin• Histamine
Catecholamines• Dopamine• Norepinephrine• Epinephrine
Amino acids• Glutamate• Gamma-amino butyric acid (GABA)• Glycine
2. Large Molecule TransmittersNeuropeptides
•Substance P and Other Tachykinins•Opoid Peptides
3. Other Chemical Transmitters• Cannabinoids• Gases (NO)
Neurotransmitter Source Site of Synthesis
Acetylcholine Choline CNS, parasympathetic nerves
Serotonin Tryptophan CNS, chromaffin cells of the gut, enteric cells
GABA Glutamate CNS
Histamine Histidine hypothalamus
Epinephrine Tyrosine adrenal medulla, some CNS cells
Norepinephrine Tyrosine CNS, sympathetic nerves
Dopamine Tyrosine CNS
Nitric oxide Arginine CNS, gastrointestinal tract
C.CATECHOLAIMNES
• Cholinergic • Dopaminergic• Noradrenergic• Serotonergic
Functions• In PNS
– Induces skeletal muscle contraction
• In CNS– Arousal and reward– Enhancement of
sensory perceptions when we wake and in sustaining attention
Functions• Behavior and cognition• Voluntary movement• Motivation, punishment
and reward• Mood, attention, working
memory, and learning
Functions• Affects amygdala, where
attention and responses are controlled
• Increasing heart rate, triggering the release of glucose from energy stores
• Increasing blood flow to skeletal muscle
• Increases the brain's oxygen supply
Functions• Mood• Cognition• Sleep• Memory Processing
• Schizophrenia• Parkinson’s Disease• Alzheimer’s Disease• Dementia• Bipolar Disorder• Depression• Sleep Disorder
• Neurotransmitters are the wonder chemicals of human body.
• URL1-http://en.wikipedia.org/Neurotransmitters• Barren et al. (2005), Ganong’s Review of Medical Physiology (23rd
Ed.), Elsevier, pp 223-297