The Nervous System (MFEL 3010) PDF

Trondheim – Gjøvik – Ålesund The nervous system MFEL 3010 By OpenStax - https://cnx.org/contents/[email protected]:fEI3C8Ot@10/Preface, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30147907 The nervous system Two main parts: 1. Central nervous system (brain...

Trondheim – Gjøvik – Ålesund The nervous system MFEL 3010 By OpenStax - https://cnx.org/contents/[email protected]:fEI3C8Ot@10/Preface, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30147907 The nervous system Two main parts: 1. Central nervous system (brain and spinal cord) the CPU 2. Peripheral nervous system (spinal nerves with branches, and nervous mesh in internal organs the input and output system By The original uploader was Fuzzform at English Wikipedia - File:NSdiagram.png, GFDL, https://commons.wikimedia.org/w/index.php?curid=22092840 Functional unit: Neuron (nerve cell)  Functional unit: Neuron (nerve cell) > 100 billon nerve cells in the human body. Each nerve cell consists of a cell body and various branches. Main branch is called the axon, and is the functional unit of a nerve fiber. 6  Functional unit: Neuron (nerve cell) Cell body – metabolism Axon – main conductor Dendrites - input By Dhp1080, svg adaptation by Actam - Image:Neuron.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4293768 7  Nerve cell bodies are collected in: Nuclei – inside the central nervous system Ganglia – outside the nervous system 8 Main function: Conduction Creative Commons Attribution 4.0 License - Access for free at https://humanbiomedia.org/  Repolarization: Depolarization: Sodium channels open Potassium channels open. Creative Commons Attribution 4.0 License - Access for free at https://humanbiomedia.org/ Glia cells (support cells): In peripheral nerves In the CNS  Myelin sheath 14 Myelin sheath Made by glia cells Insulation – fatty sheaths AP jumps from node to node increasing signal conduction By Neuron_with_oligodendrocyte_and_myelin_sheath.svg: *Complete_neuron_cell_diagram_en.svg: LadyofHatsderivative work: Andrew c (talk) - Neuron_with_oligodendrocyte_and_myelin_sheath.svg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10888009 CC BY 4.0 - http://docjana.com/saltatory-conduction/ Multiple sclerosis: Loss of myelin Multiple sclerosis: progression Connection between nerve cells Synapses:  Synapses: Synapses are the contact areas where information is transmitted from one nerve cell to another or from a nerve cell to a muscle or gland cell The synaptic gap is too wide for the action potential to cross. Transmission by signal molecules; transmitters that diffuse across the gap, binds to post synaptic receptors and triggers either depolarization or increases polarization in the post synaptic cell, by interfering with either Na+ or K+ channels 20  Synapses: Many different transmitters – specific Transmitters A single presynaptic pulse may be too weak receptors trigger (exitatory) to trigger threshold in post synaptic cell OR inhibit (inhibitory) new action potentials in post synaptic cell. 21 Transmitter removed from synapse by: Enzymatic degradation Reuptake in presynaptic cell  https://docjana.com/neuro-muscular-junction/ 23  Drugs External drugs can: – Mimic the action of transmitters Binding to receptors and stimulate depolarization or inhibit – E.G. Nicotine, Morphine – Increase the level of transmitters Reuptake inhibition – E.g. SSRI - antidepressants Degradation inhibition – E.g. Nerve gas – Block the release of transmitters – Eg. Botulism – Block the action of transmitters Binding to receptors without stimulation, but blocking the binding site – E.g. Atropine, betablockers 24