University:
Kentucky State University
Course:
BIO 303 | Human Physiology
Academic year:

2024
Views:

468

Pages:

13
Author:

embohescay9l

Neuron types and Neurotransmitters 1 Objectives Understand synaptic transmission  List types of sensory neurons  Classify neurotransmitters  Explain the mechanism of neurotransmission  Judge the types of receptors for the neurotrasmitters  2 Functional Unit (Neuron) 3 Transmission of Receptor Information to the Brain ➢The larger the nerve fiber diameter the faster the rate of transmission of the signal ➢Velocity of transmission can be as fast as 120 m/sec or as slow as 0.5 m/sec ➢Nerve fiber classification ➢type A - myelinated fibers of varying sizes, generally fast transmission speed ➢subdivided into a, b, g, d type B- partially myelinated neurons (3-14m/sec speed) ➢type C - unmyelinated fibers, small with slow transmission speed 4 Types of Nerve Fiber -Myelinated fibers – Type A (types I, II and III) -A α -Aβ -Aγ -Aδ -Umyelinated FibersType C (type IV) 5 Neuron Classification 6 Structural Classification of Neurons 7 Neurotransmitters ❖Chemical substances that function as synaptic transmitters 1. Small molecules which act as rapidly acting transmitters ❖acetylcholine, norepinephrine, dopamine, serotonin, GABA, glycine, glutamate, NO 2. Neuropeptides (Neuromodulators) ❖more potent than small molecule transmitters, cause more prolonged actions ❖endorphins, enkephalins, VIP, ect. ❖hypothalamic releasing hormones ❖TRH, LHRH, ect. ❖pituitary peptides ❖ACTH, prolactin, vasopressin, ect. 8 Neurotransmitters 9 10 Comparison between Small Molecules and Neuropeptides Neurotramsmitters (NT) ❖Small molecules NT are rapidly acting as compared to slowly acting neuropepides ❖Neuron has only one NT but may have one or more NP ❖Small molecules NT are have short lived action compared to prolonged time of action for neuropeptides ❖Small molecules NT are excreted in larger amounts compared to smaller quantities of neuropeptide ❖Small molecules NT vesicles are recycled but neuropeptide ones are not ❖Neuropeptides are co-secreted with small molecules NT ❖Neuropeptides are synthesized at the soma while small molecules could be formed at the presynaptic terminals 11 Removal of Neurotransmitter ❖Diffusion ❖move down concentration gradient ❖Enzymatic degradation ❖Acetylcholinesterase for (Ach), peptidases for neuropeptides ❖Uptake by neurons or glia cells ❖neurotransmitter transporters ❖Prozac = serotonin reuptake inhibitor 12 ▪ Transmitter Inactivation: reuptake and enzymatic breakdown Reuptake by transporters (glial cells) Enzymatic breakdown Neurotransmitter can be recycled in presynaptic terminal or can be broken down by enzymes within the cell 13

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