Quiz 8 - Graded Potentials and Synaptic Communication

Question 1

Current

Answer 1

Flow of electrical forces (opening of ion channels)

Question 2

Voltage

Answer 2

Electrical potential difference (Ion concentration gradient)

Question 3

Ohm’s law

Answer 3

Current = Voltage/Resistance

Question 4

Resistance

Answer 4

Opposition of passage of electrical current (membranes)

Question 5

Action Potentials

Answer 5

Propagation of local depolarization via voltage gated ion channels

Question 6

Orthodromic conduction

Answer 6

Down one direction of axon

Question 7

Antidromic conduction

Answer 7

Back up the axon

Question 8

Nodes of Ranvier

Answer 8

Gaps in myelination, sites of depolarization, saltatory conduction

Question 9

Myelination

Answer 9

Speeds up axon conduction

Question 10

Graded Potentials

Answer 10

Aka Local Potential, Generator Potential, Receptor Potential

Membrane potentials that initiate small local events that in turn trigger an action potential

Question 11

What stimuli do graded potentials react to?

Answer 11

Sensory stimuli via receptor complex

Neurotransmitter signals from a synapse

Question 12

Which type of potential propagates?

Answer 12

Action potentials do via voltage-gated channels

Graded potentials do not, are local

Question 13

What is the amplitude of potentials?

Answer 13

APs - Larger, 100 mV

GPs - Smaller, 3-20 mV

Question 14

What is the duration of potentials?

Answer 14

APs - Shorter, 1-2 ms

GPs - Longer, ms-seconds, occur until summation triggers AP or stimulus ends

Question 15

What is the localization of potentials?

Answer 15

APs - cell-wide

GPs - Localized

Question 16

Which potentials have a refractory period?

Answer 16

APs - yes

GPs - no

Question 17

Which potentials are decremental?

Answer 17

Degrade with distance
APs - no
GPs - yes

Question 18

How do potentials spread?

Answer 18

APs - voltage gated channels

GPs - passive electrochemical

Question 19

What is summation?

Answer 19

Collective graded potentials together depolarize the membrane and trigger AP. Can be spatial or temporal.

Question 20

What is spatial summation?

Answer 20

Collective activity of multiple graded potentials generated by different pre-synaptic neurons.

Question 21

What is temporal summation?

Answer 21

Repeated activity of graded potentials from the same pre-synaptic neuron.

Question 22

Types of neurons

Answer 22

Unipolar
Bipolar
Pseudo-unipolar
Motor
Pyramidal
Purkinje

Question 23

What is a bouton and what does it do?

Answer 23

Pre-synaptic portion of synapse

Converts electrical signal (AP) into chemical signal (neurotransmitter)

Question 24

What is a dendrite and what does it do?

Answer 24

Post-synaptic portion of synapse

Converts chemical signal (neurotransmitter) into electrical signal (AP)

Question 25

How wide is a synaptic cleft?

Answer 25

20-40nm

Question 26

What are neurexins?

Answer 26

Specialized proteins that hold synapse together.

Originate from presynaptic neuron and bind to receptor on post synaptic neuron

Question 27

Is speed of transmission directly or inversely proportional with the number of neurons in a chain?

Answer 27

Inversely

Small latency but it is there

Question 28

What is the active zone?

Answer 28

Region of synaptic bouton that is rich in mitochondria and packed with neurotransmitter containing vesicles.

Question 29

How does the active zone work?

Answer 29

Action potential arrives causing Ca2+ channels to open
Ca2+ flows in
Ca2+ causes vesicles to fuse with membrane via SNARE proteins
Fusion may or may not be complete - Kiss and Run Hypothesis
Neurotransmitters released into synapse

Question 30

What are the two main SNARE proteins?

Answer 30

Synaptotagmin on the vesicle

Syntaxin on the membrane

Question 31

What is orthograde transport?

Answer 31

Movement of neurotransmitters from cell body to boutons

Moved in vesicles attached to kinesin proteins down microtubules

Question 32

What is retrograde transport?

Answer 32

Movement of vesicles from synapse to cell body

Attached to dynein proteins down microtubules

Question 33

What is fast transport?

Answer 33

Movement of vesicles down and back along microtubules

400 mm/day

Question 34

What is slow transport?

Answer 34

Movement through cytosol and via cell structural proteins
Not slow, but less constant (on/off)
1-10 mm/day

Question 35

What is the postsynaptic density?

Answer 35

Region of post synaptic synapse that is rich with ligand-gated ion channels and other effector proteins
Similar to active zone

Question 36

What is an EPSP?

Answer 36

Excitatory post synaptic potential
Causes excitatory effects in post-synaptic cell by either causing excitement (depolarization) or inhibiting inhibition (hyperpolarization)

Question 37

What is an IPSP?

Answer 37

Inhibitory post synaptic potential
Causes inhibitory effects in post-synaptic cell by either causing inhibition (hyperpolarization) or inhibiting excitation (depolarization)

Question 38

Does an inhibited neuron pass on information?

Answer 38

Yes, often a lack of signal is what causes a downstream effect.

Question 39

What is presynaptic inhibition?

Answer 39

Occurs at the axon of the pre-synaptic neuron.

Prevention of neurotransmitter vesicle release.

Question 40

What is post-synaptic inhibition?

Answer 40

Occurs at cell body of post-synaptic neuron.

Prevention of action potential by hyperpolarization or other means.