Synaptic Transmission

Question 1

types of synapses

Answer 1

• electrical

- chemical

Question 2

electrical synapse

Answer 2

gap junctions

• direct cell to cell contact
• cytoplasmic continuity
• conduct electrical signals very rapidly (no delay)
• 2-4 nm gap
• 2 way conductance
• diameter on the protein pores = 1.5 nm
• –> only ions/small molecules can pass

Question 3

electrical synapse location

Answer 3

• immature neurons
• glacial cells to neurons
• cardiac muscle
• smooth muscle

Question 4

chemical synapse

Answer 4

• synaptic cleft (10-20 nm gap) between 2 neurons
• AP in presynaptic neuron stimulates neurotransmitter release
• NT release across cleft (.2 msec delay) to bind to receptors on postsynaptic cleft
• one way flow
• amount of NT can be modified
• number of receptors for NT can be modified

Question 5

level of excitability of a postsynaptic cellar any moment depends on:

Answer 5

1. the number of synapses active at one time
2. number the are excitatory
3. number that are inhibitory

Question 6

complexity altered by:

Answer 6

1. number of neurons

2. number of synapses

Question 7

plasticity

Answer 7

constantly making new synapses, basis for learning

Question 8

excitatory postsynaptic potentials (EPSPs)

Answer 8

depolarizing graded potentials

- neuron more likely to generate action potential

Question 9

NT’s that generate EPSPs

Answer 9

• Ach
• glutamate
• NE

Question 10

EPSPs caused by:

Answer 10

Na+ flows in

Question 11

inhibitory postsynaptic neuron (IPSPs)

Answer 11

hyper polarizing graded potenitals

- less likely to generate action potential

Question 12

NT’s that generate IPSPs

Answer 12

• GABA

- glycine

Question 13

IPSPs caused by:

Answer 13

• Cl- flow in
• K+ flow out
• • most will K+ channels, Cl- doesn’t have much of an effect by itself

Question 14

NT removal options

Answer 14

1. diffuse away (glutamate)
2. reuptake (serotonin)
3. degradation by an enzyme (AchE –> degrade Ach)

Question 15

summation

Answer 15

local potentials are small: need about 20 EPSPs to reach voltage (.5 mV)

Question 16

temporal summation

Answer 16

multiple inputs in rapid success ion from one synapse

Question 17

spatial summation

Answer 17

input from multiple different synapses arriving at the same time

Question 18

convergence

Answer 18

many different presynaptic neurons can affect a single postsynaptic cell

Question 19

divergence

Answer 19

a single presynaptic neuron that can affect many postsynaptic cells

Question 20

presynaptic facilitation

Answer 20

increased number of Ca+ channels open on presynaptic neuron, increasing the quanta of NT released, increase the postsynaptic response

Question 21

presynaptic inhabitation

Answer 21

decreased number of Ca+ channels open in presynaptic neuron, decreasing the quanta of NT released, decreasing the postsynaptic response (decreasing local potential)

Question 22

desensitization

Answer 22

with persistent stimulus, receptor fails to respond (tolerance to drugs)

Question 23

neuromodulation

Answer 23

modify the postsynaptic cells response to a specific NT (amplifying or dampening its effectiveness)

Question 24

Ligand-gated ion channels

Answer 24

• ionotropic
• cellular response = local potential
• rapid response

Question 25

ionotropic

Answer 25

receptor forms ion channel

Question 26

G-protein coupled receptors

Answer 26

- metabotropic - cellular response = activation of second messenger cascade - slower response - change in gene transcription, enzyme activity, etc.

Question 27

metabotropic

Answer 27

change "metabolism"

Question 28

metabotropic receptors

Answer 28

- usually small molecules, co-released with NT - bind to receptors on pre- or postsynaptic membrane - activate 2nd messenger signaling cascades --> have longer term effects - ex: NTs, neuropeptides, nitric oxides, ATP

Question 29

neuromodulators

Answer 29

- alter synthesis, release, uptake or metabolism of NT at the presynaptic cell - increase or decrease the effectiveness of a NT at the postsynaptic cell - are associated with longer term effects

Question 30

Botulism Toxin mechanism of action

Answer 30

- prevents exocytosis of synaptic vesicles --> no NT released - specific for excitatory neurons

Question 31

Botulims Toxin consequence

Answer 31

- decrease in muscle contraction | - can paralyze respiratory muscles (fatale)

Question 32

dystonia

Answer 32

too much muscle contraction

Question 33

sarin (nerve gas) mechanism of action

Answer 33

- inhibits AchE | - increases Ach in synapse

Question 34

sarin consequence

Answer 34

- uncontrolled muscle contraction - desenitization --> paralysis - respiratory arrest --> most common death

Question 35

SSRI

Answer 35

selective serotonin reuptance inhibitor

Question 36

Paxil (SSRI) mechanism of action

Answer 36

- prevents reuptake | - increases serotonin

Question 37

Paxil consequence

Answer 37

- build up of serotonin in synaptic cleft | - stabilizes mood

Question 38

xanax, valium, ethanol mechanism of action

Answer 38

1. stimulate GABA-R | 2. block Glut-R

Question 39

xanax, valium, ethanol consequence

Answer 39

1. decrease anxiety and increase sleep (GABA-R) | 2. decrease mental processing (learning) and decrease sensory / motor (Glut-R)