lecture 9: synaptic molecular anatomy Flashcards
how are memories stored in the brain
- physical traits of memories in the brain are formed by strengthening the connection between particular neurons
- memories arent static structures they go through encoding, consolidation, reconsolidation and retrieval
- neurons are connected by trillions of synapses, each synapse can be individually regulated
postsynaptic density
- region where all the receptors for the neurotransmitters are located
- two nerve cells are independent but communicate by releasing neurotransmitters
what is the effect of adding more receptors
more response to the released neurotransmitter = stronger connections between the neurons
process of laying down memories for a long time
over the long term how we maintain the physical trace of the memory in the brain is by altering gene expression
- release of neurotransmitter
- activation of postsynaptic receptors
- trafficking of receptors to the PSD
- local translation of new proteins
- altered gene expression
similarities between chemical and electrical synapse
- both contain mitochondria
electrical synapses
- electrical current flows from one neuron to the next at specialized sites = gap junctions
- ionic current passes in both directions
- small metabolites and second messengers can pass through gap junctions (but not proteins or nucleic acids)
- very fast
- synchronizing:
–> sensory motor neuron escape reflexes
–> hormone secreting cells of the hypothalamus
role of the hypothalamus
- receives input from the CNS and PNS and funnels these to the pituitary
role of the pituitary gland
major communication ‘hub’ between the brain and other organs, way of communicating is by the release of hormones
gap junction features (how its made and where its located)
- neurites of two cells connected by a gap junction
- gap junction channels bridge the cytoplasm of the two cells, ions and small molecules can pass in both directions through these channels
- six connexin subunits comprise one connexon, two connexons comprise one gap junction channel, and many gap junction channels comprise one gap junction
neurite
any projection from the cell body of a neuron
summary of formation of gap junctions
connexin –> connexon –> gap junction
chemical synapses
- most synaptic transmission in the CNS occurs at chemical synapses via the release of neurotransmitter
–> stimulatory (glutamate)
–> inhibitory (GABA) - contains astrocytes which have all kinds of roles in synaptic transmission
list of astrocyte roles in synaptic transmission
- buffering role
- take up glutamate
- release molecules which can communicate and regulate the function of the neuron
small synaptic vesicles (SSV) overview
- 50nm diameter
- electron lucent (clear)
- membrane bound
- contain classical neurotransmitters (glutamate, GABA, glycine ….)
Large dense core vesicles (LDCV) overview
- 100nm diameter
- electron dense (dark)
- membrane bound
- contain catecholamines, neurotrophins, neuropeptides and peptide hormones
primary locations of LDCVs
- peripheral nervous system
–> sympathetic neurons - hypothalamus
- neurosecretory cells
- neuroendocrine cells
neurosecretory cells
neurons that secrete their products into the pituitary portal vessels
neuroendocrine cells
cells which receive neuronal input and release hormones into the blood stream
LDCV role as minor players in the CNS
- comprising 1-2% of vesicles
- release peptides and neuromodulators
- slow release bc they aren’t at the active site
- can occur outside of active zones
- act on G protein coupled receptors or tyrosine kinase receptors
- effects may be presynaptic or postsynaptic
eg: local diffusion to active synaptic partners (synchronising or enhancing/modulating)
synthesis pathway
- synthesis and modification of neuropeptides: RER and golgi apparatus
- packaging : pro-peptide and modifying enzymes
- axonal transport
- cleavage of pro peptide
- release
–> slow recycling
–> synthesis pathway is different to SSVs
local translation of new proteins
the process by which proteins are synthesized directly at the site where they are needed within a cell
