Introduction to the neurone L3

Question 1

why is a graded response important>

Answer 1

if only gNa and gk are present

the cell either does not fire or fires very rapidly…

2 extremes - not good. need more gradual

Question 2

in a neurone cel body is there a graded AP response to injected current

Answer 2

yep

Question 3

what does the A current do in APs

Answer 3

the A current serves to space out the action potentials in the spike train.

Question 4

when does bursting occur

Answer 4

depolarisation activates low threshold calcium cahnnels

Question 5

can yo upicture cortical pyramidal cell bursting and thlamic relay bursting?

Answer 5

Question 6

different calcium cahnnels i nneurones

Answer 6

Question 7

what mediates repolarisation of the membrane after Ca2+ mediated burst firing

Answer 7

Action potential firing is also modulated by Ca2+-activated K+ channels. These open when Ca2+ enters through voltage-gated Ca2+ channels, and contribute an outward K+ current which opposes the depolarization and hyperpolarizes the cell.

Question 8

describe spike frequency adaptation

Answer 8

irnore hand writing

Question 9

howdo olfactory receptors cope with prolongued stimulation

Answer 9

Question 10

describe divergence

Answer 10

Each IA afferent will synapse with a number of motor neurons: a process known as divergence.

Question 11

descibe convergence

is it necessary inthe reflex?

Answer 11

Similarly, each motor neuron will receive synaptic inputs from a number of IA afferents: a process known as convergence.

Question 12

describe supralinear response summation

Answer 12

Question 13

describe response occusion

Answer 13

Question 14

Inhibitory interneurons can be deployed within the spinal cord in two functionally distinct ways.

what are they

Answer 14

feedforward and feedback inhibition

Question 15

describe feedforward inhibition

Answer 15

In feedforward inhibition, the pathway to the antagonist is inhibited when the agonist pathway is stimulated. This inhibits extensor muscles when flexors are stimulated.

Question 16

descibe feedback inhibiton

Answer 16

In feedback inhibition the excited cell contacts an inhibitory interneuron via recurrent axon collaterals to inhibit its own firing and that of its synergists. An example is provided by the Renshaw cell of the spinal cord, which stabilises motor neuron firing.

Question 17

repeated stimulaion of a synapse - what happens?

Answer 17

vescile depletion

synaptic depression ensues, representing a depletion of the readily-releasable vesicle pool.

Question 18

After the cessation of tetanic stimulation, once the synapse has recovered from depression, the post-synaptic response is transiently _______, reflecting the actions of Ca2+ on vesicle priming. This post-tetanic potentiation can persist for some minutes after repeated stimulation.

Answer 18

After the cessation of tetanic stimulation, once the synapse has recovered from depression, the post-synaptic response is transiently enhanced, reflecting the actions of Ca2+ on vesicle priming. This post-tetanic potentiation can persist for some minutes after repeated stimulation.

Question 19

describe long term potentiation

Answer 19

However, if both weak and strong inputs are tetanically stimulated together, then the EPSPs evoked by both inputs persistently increase, corresponding to associative long-term potentiation.

Question 20

label LTP diagram

Answer 20

Question 21

whats hebbs law:

Answer 21

This potentiation (LTP) obeys Hebb’s law, which states that an input is strengthened when it plays a role in firing the target cell: exactly what is required for learning.

Question 22

for LTP - t or F

Only when the postsynaptic cell is allowed to depolarise during presynaptic stimulation does long term potentiation take place.

Answer 22

T

Question 23

hebbian behaviour arises from the rpoperties of which receptor?

Answer 23

the NMDA receptor

Question 24

NMDA ca2+ admittance when depolarised

Answer 24

Question 25

LTP may underlie learning

Answer 25

memory

Question 26

In many central neurons, excitatory inputs are often located ....where?......., which are believed to isolate the postsynaptic machinery both electrically and chemically from events elsewhere within the cell. The high neck resistance of many spines will, however, somewhat attenuate the excitatory current which flows into the dendrite.

Answer 26

In many central neurons, excitatory inputs are often located on dendritic spines, which are believed to isolate the postsynaptic machinery both electrically and chemically from events elsewhere within the cell. The high neck resistance of many spines will, however, somewhat attenuate the excitatory current which flows into the dendrite.

Question 27

the necks of dendrites have a high or low resistance?

Answer 27

high resistance

Question 28

how might spine morphological changes underlie memory and LTP?

Answer 28

Changes in the spine shape and biochemistry may underlie learning and memory. Immature small spines undergo cytoskeletal changes upon potentiation which lead to rapid spine enlargement followed by enlargement of the post-synaptic density upon consolidation. altering resistance to flow - ect spines may get bigger too!

Question 29

can potentiation also occur presynapticaly?

Answer 29

yes! in area CA3 of the hippocampus, LTP does not appear to require the special properties of the NMDA receptor. Instead, potentiation is believed to take place presynaptically, and involve the activation of adenylyl cyclase and protein kinase A subsequent to calcium entry via R-type calcium channels.

Question 30

describe LTD long term depression

Answer 30

If, instead, pyramidal cells in CA1 are stimulated at low frequencies which fail to make the target cells fire, a long-term depression of synaptic strength can result. The first directly antagonises LTP by activation of protein phosphatases following entry of calcium through NMDA receptor channels more modest than that required to evoke LTP. NMDA receptor-dependent LTD appears to be a widespread feature of synapses within the neocortex. The second is initiated by metabotropic glutamate receptors acting via protein kinase C; it does not directly reverse LTP, but many of the details are still poorly understood; mGluR-dependent LTD may be especially important for motor learning in the cerebellum.

Question 31

fat

Answer 31

mamba