PSY1003 WEEK 2 PART 2

Question 1

how wide is synaptic cleft

Answer 1

20-40nm

Question 2

what are the two main types of NT

Answer 2

large (all neuropeptides) and small (synthesised in terminal button, packaged, released)

Question 3

give examples of amino acid NTs

Answer 3

GABA, glutamate

Question 4

what are monoamine NT and provide 2 examples

Answer 4

synthesised from single amino acids, present in small neuron groups with soma in brain stem eg: epinephrine, dopamine

Question 5

what is an axodendritic synapse

Answer 5

joins onto dendrite

Question 6

what is an axosomatic synapse

Answer 6

joins onto cell body

Question 7

what 2 release-related proteins have been identified by research

Answer 7

synaptotagmin (vesicle membrane protein acting as calcium sensory in docking)
syntaxin and SNAP-25 (plasma membrane protein involved in fusion)

Question 7

what is an axo-axonal synapse

Answer 7

one terminal button joins onto another

Question 8

describe process of neurotransmitter release

Answer 8

1. an AP (depolarisation wave) reaches resynaptic element opening Ca2+ channels
2. cause vesicles to bind to presynaptic membrane and release NT into synaptic cleft by exocytosis
3. vesicle membrane recovered by endocytosis “pinching off”

Question 9

how long does it take to move from AP to secretion

Answer 9

<200 us

Question 10

how long does diffusion across a synapse take

Answer 10

1-2ms

Question 11

what are ionotropic receptors

Answer 11

directly associated with ion channel, NT binds to receptor to directly open channel which then open/close straight away

Question 12

what are metabotropic receptors

Answer 12

indirectly associated with ion channel, biochemical cascade links receptor to ion channel, takes longer and effects are longer-lasting

Question 13

give a type of metabotropic receptor

Answer 13

autoreceptors = binds to own neuron NT, located on PREsynaptic rather than post, monitor NT release so prevent over/under release

Question 14

what are gap junctions

Answer 14

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

Question 15

what are ligands

Answer 15

molecule that binds to another
eg: NT on receptor

Question 16

define temporal summation

Answer 16

EPSPs received at same point on receptive membrane can be added up if impulses are received in close temporal succession

Question 17

define spatial summation

Answer 17

EPSPs received at same time on different points of receptive membrane to produce greater EPSP

Question 18

what does it mean when NT either depolarises or hyperpolarises receptive membrane

Answer 18

either decrease resting membrane potential (-70 to -65) or increase resting membrane potential (-70 to -80)

Question 19

what are excitatory NT

Answer 19

entry of positively charged ions leads to postsynaptic depolarisation, EPSP making cell more likely to fire AP eg: glutamate

Question 20

what are inhibitory NT

Answer 20

entry of negatively charged ions leads to postsynaptic hyperpolarisation, IPSP, making cell less likely to fire

Question 21

why is an AP response graded

Answer 21

EPSP and IPSP amplitude is proportional to intensity of signals that elicit them so results in a graded response

Question 22

define all or nothing response

Answer 22

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

Question 23

what is integration

Answer 23

combining individual signals (graded EPSP and IPSP) by multipolar neurons into an overall signal

Question 24

name some of the ways in which NT can be inactivated

Answer 24

1. reuptake
2. diffusion
3. glial cells
4. enzyme breakdowns

Question 25

what are the 4 ways in which drugs can interfer with an NT

Answer 25

1. causing NT release eg: amphetamine
2. mimic actions ‘agonists’ eg: barbituates
3. blocking NT action eg: ketamine
4. blocking NT reuptake eg: cocaine

Question 26

how does fluoxetine drugs work

Answer 26

blocks 5-HT reuptake to treat depression