neuro: neural conduction and synaptic transmission

Question 1

describe the active process that establishes resting membrane potential

Answer 1

sodium potassium ATPase pump
2 P in and 3 Na out
so high level of K+ inside cell and Na+ outside the cell
requires energy supplied by ATP

Question 2

inside the neutron is ____ -ve charged than outside the neuron at __mv

Answer 2

more

-70

Question 3

describe the passive process that establishes resting membrane potential

Answer 3

at resting, K+ channels open and Na+ channels closed (so membrane isn’t depolarised)
K+ flow down chemical gradient and produce electric current leading to membrane potential
makes inside more negative and separates the charges between inside and out (electrostatic pressure)
eventually system will reach equilibrium
chemical gradient = electrical gradient

Question 4

resting state =

Answer 4

when no action potentials are being fired

Question 5

resting membrane potential arises because the ions are __________ across a membrane

Answer 5

unevenly distributed

Question 6

_______ is when a membrane is made less negative

_______ is when a membrane is made more negative

Answer 6

depolarisation

hyperpolarisation

Question 7

describe how an action potential is generated

Answer 7

resting potential = -70mv
becomes depolarised to reach threshold of -65mv
as soon as threshold is reached Na+ channels open and Na+ flow inside neuron causes increase in potential from -65mv to +30mv
Na+ channels then close and K+ channels open
causing repolarisation (restores resting potential) and even hyperpolarisation (more negative than resting P)

Question 8

how is the balance of ions restored after hyperpolarisation to return to resting state so another action potential can be generated?

Answer 8

sodium potassium ATPase pump

active process

Question 9

give the features of an action potential

Answer 9

unidirectional
all or none responses - must reach threshold to fire
propagation along axon by the passive flow of charge
saltatory conduction

Question 10

what is saltatory conduction and how does it speed up action potentials?

Answer 10

transmission of action potentials in myelinated axons
signals jump from 1 node of Ranvier to the next
this increases the speed of axonal conduction

oligodendrocytes wrap their processes around axons of certain neutrons and insulate parts

Question 11

describe the process of neurotransmitter release

Answer 11

NT is synthesised and stored in vesicles
vesicles cluster near synapes along presynaptic membrane
AP reaches presynaptic terminal causing Ca2+ channels to open
this causes vesicles to bind to presynaptic membrane and release NT into synaptic cleft
process of EXOCYTOSIS

Question 12

process of endocytosis during neurotransmitter release?

Answer 12

after exocytosis, vesicle membrane is recovered

bits of presynaptic membrane are ‘pinched off’

Question 13

lots of NT release related proteins have been identified. name 3

Answer 13

synaptotagmin - acts as calcium sensor
syntoxin
SNAP-25
both involved in fusion of vesicles

Question 14

what are the different types of postsynaptic elements?

Answer 14

dendrite, cell body, terminal button

Question 15

a dendritic post synaptic element is called an?

Answer 15

axodendritic synapse

Question 16

a cell body postsynaptic element is called an?

Answer 16

axosomatic synapse (cell body = soma)

Question 17

a terminal button postsynaptic element is called an?

Answer 17

axo axonal synapse

Question 18

what are the 2 different types of receptors on postsynaptic membranes?

Answer 18

ionotropic and metabotropic

Question 19

what is the difference between ionotropic and metabotropic receptors?

Answer 19

ionotropic receptors are directly associated with ion channel whereas metabotropic are indirectly associated

ionotropic have subunits (5 usually) but metabotropic have no subunits

Question 20

how do metabotropic indirectly work?

Answer 20

biochemical cascade that links the receptor to the ion channel

Question 21

what affects the likelihood of action potentials?

Answer 21

influx of Na+ into postsynaptic membrane/ entry of +ve ions → causes depolarisation → threshold reached → `EPSPs (excitatory) → potential from -70 to -67 → increases likelihood of firing → action potential propagated

influx of K+/ entry of -ve ions → causes hyperpolarisation → no threshold reached → IPSPs (inhibitory) → potential; from -70 to -72 → decreases likelihood → no action potential propagated

Question 22

weak signals = ___ postsynaptic potentials

strong signals = ____ postsynaptic potentials

Answer 22

small

large

Question 23

threshold of excitation = ___mv

Answer 23

-65

generates action potential

Question 24

explain integration of postsynaptic potentials

Answer 24

each multipolar adds together all the graded excitatory and inhibitory potentials and decides to fire or not on the basis of their sum

Question 25

what is spatial summation?

Answer 25

lots of potentials from DIFFERENT parts of membrane fire SIMULTANEOUSLY

Question 26

what is temporal summation?

Answer 26

potentials from the SAME synapse produced in rapid SUCCESSION

Question 27

how are neurotransmitters inactivated

Answer 27

removed from synaptic cleft by:
reuptake by active transport, diffusion, glial cells, enzyme breakdown

breakdown products can also be actively transported back into presynaptic
resynthesis can occur after breakdown by enzymes in pre synapse