Synapse Class notes
Synapse Class notes BIOH 313-001
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This 7 page Class Notes was uploaded by Rebeka Jones on Wednesday October 5, 2016. The Class Notes belongs to BIOH 313-001 at Montana State University taught by Noudoost, Behrad in Fall 2016. Since its upload, it has received 4 views. For similar materials see Neurophysiology in Cell Biology and Neuroscience at Montana State University.
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Date Created: 10/05/16
Synapses If you have a 0 on the loma question you can redo it by next exam. th In the 17 century they did not understand the brain until Camillo Golgi came up with the Golgi method. Then Santiago Ramon y Cajal used this method to study the organization of the nervous system. Eventually the Neuron Doctrine came about. It is the concept that the nervous system is made up of discrete individual cells. • The brain is made up of individual units that contain specialized features such as dendrites, a cell body, and an axon. These individual units are cells as understood from other tissues in the body, they differ in size, shape, and structure according to their location or functional specialization. • Nerve cells are connected by sites of contact and not cytoplasmic continuity. Although the axon can conduct in both directions, in tissue there is a preferred direction for transmission from cell to cell. A barrier to transmission exists at the site of contact between two neurons that may permit transmission. • If a contact is made between two cells, then that contact can be either excitatory or inhibitory, but will always be of the same type. Dale's law: Each nerve terminal releases a si ngle type [set] of transmitter(s) Electrical synapses are more common in the central nervous system than previously thought Thus rather than functioning as individual units, in some parts of the brain large ensembles of neurons may be active simultaneously to process neural information Electrical synapses are formed by gap junction that allow molecules to directly pass between neurons creating a cytoplasm-to-cytoplasm connection Furthermore, the phenomenon of co-transmission in which more than one neurotransmitter is releases from a single presynaptic terminal, contributes to the complexity of information transmission within the nervous system All of the green spots are where the neuron is receiving a synapse 2 The average neuron forms about 1000 synaptic connection and receives even more, perhaps as many as 10,000 connecting the Purkinje cell of the cerebellum receives up to 100,000 inputs The strength of both forms of synaptic transmission can be enhanced or diminished by cellular activity. This plasticity in nerve cells is crucial to memory and other higher brain functions *the strength of a synapse means memory – linking different stimuli to different events a cell receives information from different cells that have different weights…. that weight allows you to react in different ways. This is a small scale version about what is actually happening *Integration of information within network of neurons is the basis for our perceptions and actions If something changes in the way you identify someone your brain has to figure out a new way to identify (the means your network wants to be more flexibile). You then find a new way to identify that thing. By bringing in this new component and changing its weight you are able to identify again. 3 Axo-dentrict = intergrage information Axo-somatic = can inhibit the whole cell Axo-axonal = modgulate the reaction connected space 4 Electrical trassmssion allows the rapid and synchronous firing of interconnected cells Thus, a behavior controlled by a group of electrically coupled cells has an important adaptive advantage: It is triggered explosively in an all-or-none manner. Gila cells may play an active role in signialling the brain Gap junctions enhance communication *watch videos under lecture 7 5 Similarities between electrical and chemical synapses -they both need to generate action potential after all - both synapses can undergo plastic changes Differences between electrical and chemical synapses • Membrane distance – smaller in electrical • Membrane continuity – present in electrical • The method of transmission • The transmitted material • Synaptic delay • Direction of signal transmission – bi directional in electrical • All-or-none: every flow in electrical synapses causes some depolarization, but in chemical synapses either it does or does not. • Chemical synapses can be inhibitory; therefore, more complex behaviors may arise. • Chemical synapses can amplify the signal • Cell size matters for electrical synapses: Presynaptic cell needs to be bigger than postsynaptic cell, so after drop of current still enough voltage is generated in postsynaptic cell. • Electrical synapse transmits both depolarization and hyperpolarization 6 7
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