Anatomy and phys lecture 14
Anatomy and phys lecture 14 PHCL2600
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This 4 page Class Notes was uploaded by Legacy Tanner on Tuesday October 6, 2015. The Class Notes belongs to PHCL2600 at University of Toledo taught by Williams,F in Fall 2015. Since its upload, it has received 17 views. For similar materials see Funct Anat and Pathophysiol I in Pharmaceutical Sciences at University of Toledo.
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Date Created: 10/06/15
Anatomy Lecture 14 Schwann Cells 0 Each Schwann cell produces part of the myelin sheath surrounding an axon A cell myelinates 1 segment of an axon 0 Cells wrap around PNS axons lnner portion is myelin sheath Outer portion is the neurolemma produces myelin sheath 0 Pic in phone Oligodendrocytes 0 Each oligodendrocyte cell forms myelin sheath around as many as 40 axons in the CNS 0 Cell bodies are small Myelination in CNS axons 0 Cell bodies of oligodendrocytes do not surround the axons No neurolemma found 0 Tip of processes is involved in forming the myelin sheath Synthesis of large amount of plasma membrane Unmyelinated axons in PNS o Unmyelinated axons are a bundle of axons that are wrapped very thinly by Schwann cells 0 Thinly wrapped around each axon rather than a thick wrapping around a bundle like we are used to seeing 0 Node of Ranvier 0 Periodic gaps in the myelin sheath Facilitates the rapid conduction of nerve impulses Electrical impulses hop from 1 node to another 000 On a myelinated axon the impules hops between each node to quickly transport message 0 Unmyelinated axon makes impules go through the entire axon no skipping because no myelin to make nodes Neurotransmission 0 Pic in phone on neurotransmission o Nerve impulse Production of action potential 0 Change in membrane potential 0 Flow of ions 0 Synaptic transmission Release of neurotransmitters at the synapse Electrical signals in neurons 0 Like muscle bers neurons are electrically excitable 0 They communicate with 1 another using 2 types of electrical signals Graded potentials Shortdistance communication Action potentials Communication over long distances within the body 0 Production of electrical signals in neurons depend on A variety of ion channels that open or close in response to speci c stimuli Because the lipid bilayer of the plasma membrane is a good insulator ions must flow through these channels The existence of a resting membrane potential RMP Type of ion channels 0 0 They are present in the plasma membrane Leak or passive nongated channels They randomly open and close Gated channels They open and close in response to a stimulus Ligandgated Mechanically gated Voltagegated Selective permeability of membranes Speci c ions cross the membrane in direction of concentration gradient higher to lower Leak or Passive channels 0 Permeability to ion is high 0 They alternate between open and close position 0 0 Present in all cells In neurons they are in dendrites cell bodies and axons Ligandgated channel 0 Binding of a ligand stimulates the channel Ligand neurotransmitter hormones and ions 0 In dendrites of sensory neurons 0 In dendrites and cell bodies of interneurons and motor neurons mainly concentrated of the synapse Mechanically gated channels 0 Mechanical stimulus vibration touch pressure and tissue stretching o In auditory receptors receptors in internal organs and skin receptors Voltagegated channels 0 Open in respond to a change in membrane potential mainly located along the neuronal axon 0 Generation and conduction of action potential in axons Present on unmyelinated axons Node of Ranvier myelinated axons and axon hillock 0 Examples Na K and Ca2 channels 0 Model for voltagegated Na channels 0 Example Na channel 0 Both activation and inactivation gates need to be open for ion to pass through 0 At rest the activation gate is closed and the inactivation gate is open 0 Voltagegated K channels has only a single gate 0 Pic in phone
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