CSB332 Lecture 1 Notes

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University of Toronto St. George
Cell and Systems Biology
Francis Bambico

CSB332 Lecture 1 Slide 2 - Synapse is something that interconnects two objects Slide 3 - Santiago Ramon y Cajal (Spanish neuroscientist) is known for the formulation of the neuron doctrine o Fundamental tenant of neuroscience o The nervous system is not a syncytium (e.g., not composed of one mesh of cytoplasm interconnect with each other) o The nervous system is composed of discrete neurons that are interrupted by clefts or spaces, which are called the synaptic clefts o Based on light microscopic observations of the structure and the types of neurons o Made use of Golgi state, which involves the reaction of two chemicals (potassium dichromate and silver nitrate) will incorporate in all of the neurons and glial cells when applied to a neural tissue  Only some subpopulations of neurons are able to be stained where the reaction takes place, so he was able to see the structure of the neurons • Purkinje cells are abundant in the cerebellum Slide 5 - There are different synapses based on where the pre-synaptic neuron synapses with the post-synaptic neuron o Axosomatic synapse = axon of pre-synaptic neuron + cell body of post-synaptic neuron o Axodendritic synapse = axon of pre-synaptic neuron + shaft or spine of dendrite of post-synaptic neuron Slide 6 - You can observe the structure of the synapse by using a light microscope or a fluorescent microscope, but it can only resolve objects that are between 1 µm and 100 nm o The distance between the pre-synaptic neuron and the post-synaptic neuron (e.g., the synaptic cleft) is about 20 to 40 nm - You need to use an electron microscope to examine subcellular that compose the synapse (e.g., ion channels, receptors, enzymes, and proteins that are embedded in the plasma membrane) up to 10 nm o The wavelength of the electron beam is 100,000 times shorter than the wavelength of visible light o Disadvantage  Cannot view living cells (e.g., dehydrated, chemically treated, application of heavy metals that are electron dense) Additional slide 1 - Type I synapse o Excitatory synapse  Release glutamate (an excitatory neurotransmitter) o When examined under an electron microscope  Round synaptic vesicles containing glutamate or excitatory neurotransmitters  Postsynaptic density is wider  Prominent presynaptic dense projections • Proteins that are involved in exocytosis  Synaptic cleft is wider, about 20 nm  Active zone is larger and thicker • Contain the readily releasable pool of synaptic vesicles • This is where exocytosis or neurotransmitter release takes place o Also called asymmetrical synapse  Postsynaptic density is much thicker than presynaptic density - Type II synapse o Inhibitory synapse  Release GABA (an inhibitory neurotransmitter) o Found in axosomatic regions and axodendritic regions o Flattened synaptic vesicles o Modest basement membrane o Active zone is compartmentalized Slide 7 - Neuropeptides are encapsulated by larger vesicles than the vesicles for neurotransmitters Slide 9 - The synapse is the fundamental unit of behaviour - Different regions of the brain control different functions - More complex behaviours are produced by interconnections of different brain structures o Motor control of language is controlled by Broca's area o Understanding of speech is controlled by Wernicke’s area Slide 10 - MRI o Most commonly used brain imaging method to visualize the brain o Based on the application of a strong magnetic field o Electric current in a clockwise manner produces an electromagnetic field o Electromagnetic field will align hydrogen protons in an antiparallel or a parallel direction  Produces a strong net longitudinal field vector o RF pulses disturbs the precession of the protons  Some of the protons will randomly become disoriented  Produces a horizontal or transverse field vector o T2 relaxation time is the time for the transverse field vector to dissipate or relax upon withdrawal of the RF  The time for the protons that are aligned transversely to revert to the longitudinal axis o T1 relaxation time is the time for the long
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