Ionotropic receptors

Question 1

Direct receptors

Answer 1

• ligand gated ion channels
• NMDA, non-NMDA
• ionotropic

Question 2

Indirect receptors

Answer 2

GPCR

- metabotropic

Question 3

EPSP

Answer 3

• depolarisation

- Na influx

Question 4

IPSP

Answer 4

• hyperpolarisation

- cl influx

Question 5

excitatory synaptic transmission

Answer 5

• glutamate
• NMDA
• AMPA, Kainate
• 1 metabotropic

Question 6

spinal reflex is composed of

Answer 6

both EPSPs and IPSPs

Question 7

NMDA channels

Answer 7

• permeable to Na, K, Ca
• lowest permeability to Ca
• blocked by ECF Mg / APV
• activated by glutamate

Question 8

non-NMDA

Answer 8

• P to Na/K
• opened by Glu
• Na influx
• K efflux

Question 9

with 0 Mg, Vm is negative

Answer 9

• channel opening downwards
• inward current (negative)
• XS na influx (compared to K efflux)
• DF high on Na

Question 10

with 0Mg, Vm is positive

Answer 10

• channel opening upwards
• current Is outwards (positive)
• XS K efflux compared to Na influx
• large DF on K

Question 11

At 0mV

Answer 11

• no visible activity
• zero current
• current reversal potential (Erev)
• channel equally P to Na/K
• Nain = Kout

Question 12

The presence of Mg

Answer 12

• channel opening unaffected at +60
• increasingly negative potential, channel openings briefer
• increased amount of block by Mg
• ## open channel block is increased at a negative Vm- voltage dependent block

Question 13

the drug APV

Answer 13

has no effect on the NMDA channel at negative Vm

• channel already blocked. by Mg
• has an effect at more positive Vms where Mg isn’t blocking the channel
• only non-NMDA C contribute to the EPSP current at negative Vm

Question 14

what is the importance of NMDA r modulation?

Answer 14

• only non-NMDA channels contribute to EPSP following single stimulation
• repeated synaptic activation - summation of EPSPs (increased depol)
• Mg block of NMDA channels is partly relieved due to repeated activation
• Vm sufficiently positive so Mg os repelled from channels
  -now NMDA channels contribute to EPSP
• ## Ca entrance

Question 15

Ca influx leads to…

Answer 15

• enzyme activation
• release of retrograde factor from Post SN - autocrine
• enhances release of Glu from pre SN
• enhanced synaptic function during subsequent stimulation
• synaptic plasticity
• basis for memory

Question 16

inhibitory synapses

Answer 16

• IPSP
• hyperpol
• Glycine (SC), GABAa (brain)
• inotropic/ can be metabotropic

Question 17

are permeable to

Answer 17

• chloride ions
• Cl influx
• outward current generated (positive)
• hyperpolarisation
• greater outward current during more positive voltages (larger DF on Cl)
• ## Ecl= -70mV