PSY1003 WEEK 2 PART 2 Flashcards
how wide is synaptic cleft
20-40nm
what are the two main types of NT
large (all neuropeptides) and small (synthesised in terminal button, packaged, released)
give examples of amino acid NTs
GABA, glutamate
what are monoamine NT and provide 2 examples
synthesised from single amino acids, present in small neuron groups with soma in brain stem eg: epinephrine, dopamine
what is an axodendritic synapse
joins onto dendrite
what is an axosomatic synapse
joins onto cell body
what 2 release-related proteins have been identified by research
synaptotagmin (vesicle membrane protein acting as calcium sensory in docking)
syntaxin and SNAP-25 (plasma membrane protein involved in fusion)
what is an axo-axonal synapse
one terminal button joins onto another
describe process of neurotransmitter release
- an AP (depolarisation wave) reaches resynaptic element opening Ca2+ channels
- cause vesicles to bind to presynaptic membrane and release NT into synaptic cleft by exocytosis
- vesicle membrane recovered by endocytosis “pinching off”
how long does it take to move from AP to secretion
<200 us
how long does diffusion across a synapse take
1-2ms
what are ionotropic receptors
directly associated with ion channel, NT binds to receptor to directly open channel which then open/close straight away
what are metabotropic receptors
indirectly associated with ion channel, biochemical cascade links receptor to ion channel, takes longer and effects are longer-lasting
give a type of metabotropic receptor
autoreceptors = binds to own neuron NT, located on PREsynaptic rather than post, monitor NT release so prevent over/under release
what are gap junctions
narrow spaces between adjacent cells and bridged by “connexins” (tubular protein channels) which allow electrical signals and small molecules to pass between cells, quicker than chemical synapse
what are ligands
molecule that binds to another
eg: NT on receptor
define temporal summation
EPSPs received at same point on receptive membrane can be added up if impulses are received in close temporal succession
define spatial summation
EPSPs received at same time on different points of receptive membrane to produce greater EPSP
what does it mean when NT either depolarises or hyperpolarises receptive membrane
either decrease resting membrane potential (-70 to -65) or increase resting membrane potential (-70 to -80)
what are excitatory NT
entry of positively charged ions leads to postsynaptic depolarisation, EPSP making cell more likely to fire AP eg: glutamate
what are inhibitory NT
entry of negatively charged ions leads to postsynaptic hyperpolarisation, IPSP, making cell less likely to fire
why is an AP response graded
EPSP and IPSP amplitude is proportional to intensity of signals that elicit them so results in a graded response
define all or nothing response
if sum of depolarisations and hyperpolarisations reaching axon initial segment at any time is enough to depolarise membrane to excitation threshold, then generates an AP
what is integration
combining individual signals (graded EPSP and IPSP) by multipolar neurons into an overall signal
name some of the ways in which NT can be inactivated
- reuptake
- diffusion
- glial cells
- enzyme breakdowns
what are the 4 ways in which drugs can interfer with an NT
- causing NT release eg: amphetamine
- mimic actions ‘agonists’ eg: barbituates
- blocking NT action eg: ketamine
- blocking NT reuptake eg: cocaine
how does fluoxetine drugs work
blocks 5-HT reuptake to treat depression
