Nervous Sytem VI Flashcards
What are the two categories of neurocrine receptors?
Ionotropic and metabotropic receptors
What are ionotropic receptors?
Ligand gated ion channels
- ligand binding to ionotropic receptors causing conformational change leading to opening of channel
- can be specific for ion or non-selective
What kind of postsynaptic response do ionotropic receptors mediate?
Fast (neurotransmitter)
What are metabotropic receptors
G-protein coupled receptors
- cytoplasmic tail of receptor linked to 3 part transducer protein (G-protein)
What kind of response to metabotropic receptors mediate?
Slower (neuromodulators)
What 2 g-protein mediated cell responses happen in result of ligand binding to metabotropic receptor?
- Interact directly with ion channels
- can lead to opening or closing
- Interaction with a membrane bound enzyme
- phospholipase C signal transduction pathway
- adenylyl cyclase signal transduction pathway
Can a neurocrine have slow and fast responses?
Same neurocrine can act as neurotransmitter or neuromodulator depending on receptor present on postsynaptic cell
Where are neurotransmitters released from?
Vesicles containing neurotransmitters accumulate in axon terminal
What is neurotransmitter synthesis?
Large peptide neurotransmitters are produced and packaged into vesicles at the soma and transported with fast axonal transport
Small ones are synthesized and packaged at axon terminal
How does neurotransmitter release happen?
Occurs via Ca2+ mediated exocytosis
High concentration of voltage gated calcium channels at pre-synaptic terminal
Termination of neurotransmitter activity?
- Nts return to axon terminals for reuse or transported into glial cells
- Enzymes inactivate nts
- Nts can diffuse out of synaptic cleft
What releases more neurotransmitter?
A stronger stimuli, increased AP firing leads to greater influx of Ca2+ and increased neurotransmitter release
What are 2 types of synaptic integration?
Convergence and divergence
What is convergence?
Presynaptic neurons converge on one or a small number of postsynaptic neurons
What is divergence?
Neurons can have branching axons that contact many different postsynaptic neurons
What is integration of synaptic signaling?
Input from multiple presynaptic neurons converging on a single postsynaptic cell is summated to determine the output
What is spatial summation?
Spatial= different locations
Occurs when the currents from multiple simultaneous graded potentials combine to create suprathreshold signal- create AP
Why can spatial summation be inhibitory?
Efflux of K+
One inhibitory and 2 excitatory neurons fire and sum is below threshold
What is temporal summation?
Two graded potential from one presynaptic neuron occur close together in time and sum and initiate AP
What is presynaptic modulation?
Excitatory or inhibitory neurons may synapse on synaptic terminals and augment communication between pre and postsynaptic cell
What is presynaptic inhibition?
Inhibits neurotransmitter release
What is presynaptic facilitation?
Increase neurotransmitter release
What is global presynaptic inhibition?
All targets cells don’t get stimulated and entire neuron is inhibited
What is selective presynaptic inhibition?
Inhibitory neuron synapses one one of neurons so inhibitions happens are one target and other are unaffected
What happens in postsynaptic modulation?
Strengthening or weakening of synapses due to changes in receptor expression on post synaptic
- changing structure, affinity or number of neurotransmitter receptors
