L11 & 12: Neurobiology V & VI

Question 1

neuron signal information by

Answer 1

graded potentials and action potentials

Question 2

graded potentials

Answer 2

are membrane potential changes of variable amplitude and duration that are conducted decremental.

Question 3

graded potentials have no

Answer 3

threshold or refractory period

Question 4

___ is required to initiate action potentials

Answer 4

summation of graded potentials

Question 5

action potential

Answer 5

rapid change in the membrane potential during which the membrane rapidly depolarizes and repolarizes

Question 6

action potentials provide

Answer 6

long-distance transmission of information through the nervous system

Question 7

action potentials occur in

Answer 7

excitable membranes (neuronal and muscle cells) because there membranes contain many voltage-gated Na+ and K+ channels

Question 8

depolarization of excitable membranes triggers an action potential only when

Answer 8

the membrane potential exceeds a threshold potential

Question 9

regardless of the size of the stimulus, if the membrane reaches threshold,

Answer 9

the action potential generated is always the same size

Question 10

a membrane is refractory

Answer 10

for a brief time following an action potential

Question 11

action potential propagation is faster in

Answer 11

myelinated axons

Question 12

a synapse

Answer 12

a structure that permits a neuron to pass an electrical or chemical signal to another cell

Question 13

two types of synapses

Answer 13

electrical and chemical synapses

Question 14

electrical synapses

Answer 14

pass electrical signals directly from cell-to-cell through gap junctions

Question 15

chemical synapses

Answer 15

the vast majority of synapses, use neurotransmitters to pass information to the target cell

Question 16

all gap junctions channels consists of a pair of

Answer 16

hemichannels

Question 17

one hemichannel is in ____, and the other in ____

Answer 17

the presynaptic, the postsynaptic cell

Question 18

these hemichannels make ___

Answer 18

contact in the gap between the two cell membranes, forming a continuous bridge between the cytoplasm of the two cells

Question 19

the pore of the hemichannel has a diameter of

Answer 19

1.5 nm

Question 20

the pore size permits small intracellular metabolites to pass

Answer 20

directly between the cytoplasm of the two cells

Question 21

each hemichannel is called

Answer 21

connexon

Question 22

connexon is made up of

Answer 22

six identical protein subunits, called connexins

Question 23

electrical synapses occur

Answer 23

mainly in neurons of the CNS

Question 24

information by electrical synapses can flow

Answer 24

in both direction

Question 25

electrical synapses are also found in

Answer 25

glial cells, cardiac and smooth muscle, in non excitable cells that use electrical signals, such as the pancreatic beta cell

Question 26

the primary advantage of electrical synapses is

Answer 26

the rapid conduction of signals from cell to cell that synchronies activity within a network of cells

Question 27

neurotransmitters must cross

Answer 27

the synaptic cleft, 10 to 20 nm extracellular space that separates neurons

Question 28

the physical separation of presynaptic and postsynaptic cells results in

Answer 28

one-way conduction along multi-neuronal pathways

Question 29

aonx of the presynaptic neuron ends in a slight swelling

Answer 29

axon terminal

Question 30

within the presynaptic active zone

Answer 30

synaptic vesicles contain neurotransmitter

Question 31

post-synaptic density (PSD)

Answer 31

protein-dense region in the postsynaptic membrane in close apposition to the presynaptic active zone

Question 32

post synaptic density ensures that

Answer 32

receptor are in close proximity to presynaptic neurotransmitter release sites

Question 33

neurotransmitter release step 1:

Answer 33

action potential reaches the terminal of the presynaptic membrane

Question 34

neurotransmitter release step 2:

Answer 34

terminals possess voltage-gated Ca2+ channels, in addition to Na+ and K+ channel; depolarization during action potential opens Ca2+ channels allowing Ca2+ to flow into the axon terminal

Question 35

neurotransmitter release step 3:

Answer 35

Ca2+ activate processes that lead to the fusion of docked vesicles with the synaptic terminal membrane

Question 36

neurotransmitter release step 4:

Answer 36

Ca2+ binds to synaptotagmin proteins associated with SNARE proteins; SNAREs anchor vesicles to the plasma membrane and undergo Ca2+ dependent conformational changes to stimulate vesicle fusion with the plasma membrane

Question 37

__ proteins associated with SNARE proteins

Answer 37

synaptotagmin

Question 38

synaptotagmin proteins associated with

Answer 38

SNARE proteins

Question 39

unbound neurotransmitters are removed from the synaptic cleft in

Answer 39

three ways: diffusion, enzymatic transformation, or reuptake

Question 40

in myelinated axons, action potentials are regenerated at

Answer 40

the Nodes of Ranvier in saltatory conduction