7938707
Descripción
Fichas por Margaret-Estefani Conde Paredes, actualizado hace más de 1 año
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Creado por Margaret-Estefani Conde Paredes
hace más de 7 años
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| Pregunta | Respuesta |
| Where are there more transmitters? in the CNS or PNS? | In the CNS (brain and spinal cord). The brain receives sensory information from the outside world though peripheral sensory neurones, processes it, stores it and then produces responses. - It is remarkable that the main outputs of the brain are the autonomic nervous system and motor activation-in humans the motor control of speech and expressions makes us the unique individuals we all are. |
| What are the features of transmitters? | - they are always AGONISTS and the direction of effect and the duration of action of the transmitters are determined by their receptors |
| What are the features of receptors? | - produce fast actions (directly gating ion channels; msec onset and offset) or have slow effects (indirect links to ion channels and enzymes via G proteins; secs to mins) - subsequent intracellular changes initiate changes in activity of neurones that are more subtle than those produced by fast receptor events. |
| What does neural excitation involve? and inhibition? | - depolarization of the membrane - inhibition is produced by hyperpolarisation |
| What are the drugs that produce the most selective effects on CNS? | - drugs acting on receptors -but drugs acting to alter release or breakdown of transmitters can be very useful |
| What is GLUTAMATE? | - the main excitatory transmitter in the CNS -most neurones use glutame to transfer information from place to place in the brain |
| How many receptors does glutamate has? | - AMPA and NMDA receptors (ionotropic) on POSTSYNAPTIC sites - a fast presynaptic excitatory kainite receptors -and a number of slow METABOTROPIC receptors (G-protein) |
| How are ,the fast synaptic excitations mediated by glutamate seen throughout the CNS, activated? | They are activated though the AMPA receptor that directly opens Na channels. |
| Whys is NMDA receptor of considerable interest? | - it has been implicated in development of visual systems, epilepsy, pain transmission, memory and cell death -2 agonists are needed and the channel is both ligand-and voltage-gated; all other known channels are either one or the other - |
| , | - glycine is requred for activation of the complex in addition to the glutamate (ligand-gaing) -the channel is plugges by physiological levels of magnesium- this is removed by depolarization of the membrane (voltaged-gating) |
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