BIO10004 Week 5.1 Nerves PDF

Nerves Dr Greg Davis Martini Chapter 12 Copyright notice  Learning objectives and reading At the end of this lecture you should be able to: 1. Describe the anatomical and functional divisions of the nervous system. 2. Sketch and label the structure of a typical neuron, describ...

Nerves Dr Greg Davis Martini Chapter 12 Copyright notice  Learning objectives and reading At the end of this lecture you should be able to: 1. Describe the anatomical and functional divisions of the nervous system. 2. Sketch and label the structure of a typical neuron, describe the functions of each component. 3. Classify neurons according to their structure and function. 4. Describe the locations and functions of neuroglia in the nervous system. 5. Describe the events involved in the generation and propagation of an action potential and the factors involved in propagation speed of an action potentials. Briefly identify the mechanisms involved in synaptic activity. 6. Explain how the resting membrane potential is created and maintained. Reading guide (textbook): Sections: 12-1 to 12-5, 12-6 (p. 462 - 464) Figures: 12-1 to 12-4, 12-8, 12-12, 12-13, 12-15 Questions: 1, 4, 6, 9, (12, 16, 17) Nervous system overview Components of the nervous system Central Nervous System (CNS) – Brain and spinal cord Peripheral nervous system (PNS) – Afferent division (inputs) – Efferent division (outputs) Somatic Autonomic – Enteric (inputs and outputs from the gut)  Neurons Specialised cells – Long lived – High metabolic rate – Cannot divide (missing centrioles) Structure – Cell body – Dendrites, axons and telodendria – Axon terminals Neurons  Neuroglia The other type of neural tissue – These separate and protect neurons – Different structures and names in the CNS/PNS – CNS Maintain the Blood brain barrier Repair damaged neural tissue 3D framework Guide neuron development Provide myelin sheath (insulation) – PNS Myelin sheath Regulation of environment Neuroglia  Membrane resting potential Difference of ionic composition of ECF versus cytosol Recall active process of Na+/K+ pump Membrane permeability differs for ions Maintenance of the membrane creates the potential Passive ion channels allow movement of ions Membrane resting state  Altering the membrane potential In areas of the neuron dendrites and soma – Activation leads to changes in the membrane – Give rise to a local or graded potential Stimulation Graded potential Membrane states  The excitation potential In areas of the neuron beyond the axon hillock – Depolarisation leads to action potentials – These have several phases – Threshold is the point of no return – Different mechanisms drive each phase – All action potentials are the same size – Action potentials move differently in myelinated axons Phases Action potentials  Synapses These are connections between neurons Found at the end of the axon Most are chemical synapses – Neurotransmitter is released into synaptic cleft that activates membrane on the other side – Post-synaptic cell can be neuron, muscle or gland  Neurotransmitters Cholinergic – Acetyl Choline (ACh) Biogenic amines – Nor-epinephrene (Noradrenaline) – Dopamine, Serotonin Amino acids – GABA Neuropeptides – Opioids Dissolved gases – Nitric oxide, Carbon monoxide  Summary Neural system overview – CNS/PNS and more Neurons Neuroglia Membrane potential – Graded potentials – Depolarisation and hyperpolarisation – Action potentials Synapses Neurotransmitters