Topic 3:4

Question 1

signalling between neurons vs neurons and skeletal muscles

Answer 1

AP in one neuron produces much smaller change in post synaptic RMP
neurons need to sum input
integrate both excitatory and inhibitory inputs to finally decide if there is enough net excitation to make AP production worthwhile

Question 2

divergence

Answer 2

branching of one neuron so as to innervate others

Question 3

convergence

Answer 3

innervation of a single cell by many cells

Question 4

PSP current

Answer 4

leaks
decreases in size with distance
use current from EPSP to produce an AP so message moves further along

Question 5

synaptic effectiveness

Answer 5

closer a synapse is to AP initiating zone (axon hillock) more effective the synaptic current will be in influencing the Post synaptic neuron to produce an AP

Question 6

EPSP vs IPSP current

Answer 6

most synapses on the cell body tend to be inhibitory synapses
synapses closer to axon hillock more likely to produce a post synaptic AP as the EPSP leaks less from the synapse when flowing to the nearby axon hillock

Question 7

spatial summation

Answer 7

spatially separated synapses generate EPSPs at about same time to five larger EPSP, so that despite leaking there is now a larger amount of current to reach the axon hillock and now raise the post synaptic cell’s axon hillock to threshold for an AP

Question 8

temporal summation

Answer 8

multiple stimuli applied in quick succession to same input synapse on post synaptic cell and all produce EPSP, producing a much larger post synaptic current that can now raise the post synaptic cell’s axon hillock to threshold for an AP

Question 9

why neurons integrate

Answer 9

they have pre synaptic inhibition if they believe that one source of info is unreliable and they have presynaptic facilitation if they believe that one source is very much more reliable

Question 10

synaptic transfer altered by altering presynaptic terminal depolarisation

Answer 10

size of terminal depolarisation determines the number of voltage gated Ca++ channels opening, and therefore the amount of Ca++ entering the cell
increasing the size of the depolarisation of the pre synaptic terminal increases the size of the post synaptic potential
increasing the duration of the presynaptic terminal increases the size of the post synaptic potential

Question 11

presynaptic inhibition and facilitation

Answer 11

allows selective modification of one input to the cell only rather than modifying the cell in total

Question 12

tetanic activity

Answer 12

high rates of stimulation
bursts of activity
can potentate or depress activity at a synapse, making information transfer more or less effective to subsequent pre synaptic inputs

Question 13

post tetanic depression

Answer 13

initial period of depression of the transfer of even normal activity across that synapse

Question 14

post tetanic potentiation

Answer 14

longer period when there is an enhancement or potentiation of the transfer of normal activity across the synapse

Question 15

LTP

Answer 15

increase in size of post synaptic response to presynaptic AP (for hours or days)

Question 16

Adaptation

Answer 16

in response to a maintained and unchanging presynaptic input, the number of post synaptic APs will decline with time
allows neurons to reset sensitivity so it can response to new or changed stimulus

Question 17

adaptation caused by

Answer 17

PSPs adapt in response to maintained constant pre synaptic input
axon hillock has ion channels that cause a decrease in number of APs produced for constant stimulus