Synaptic Transmission

Question 1

Four Types of Neuronal Signaling

Answer 1

1. input signals
2. integration signals
3. conduction signals
4. output signals

Question 2

input signals are all dependent on ..

Answer 2

ligand-gated ion channels

Question 3

input signals?

Answer 3

signals received by dendrites or soma from the synapse of adjacent neuron

Question 4

input signals result in …

Answer 4

membrane potential changes → graded potential

Question 5

integration signals are all dependent on…

Answer 5

voltage-gated ion channels

Question 6

integration signals trigger ..

Answer 6

action potential

Question 7

integration occurs where in the neuron?

Answer 7

axon hillock

Question 8

What happens at the axon hillock during integration?

Answer 8

all input signals are summated

Question 9

when summated signal reaches threshold potential,

Answer 9

action potential is fired

Question 10

What is summation in neurons?

Answer 10

When multiple EPSPs combine to reach the threshold for an action potential

Question 11

temporal summation?

Answer 11

one neuron sends repeated signals close together in time

the second EPSP adds to the first before it decays.

Question 12

spatial summation?

Answer 12

multiple neurons release signals at the same time, and their EPSPs add together.

Question 13

which channels do AP conduction signals depend on?

Answer 13

voltage-gated ion channels (VGSCs).

Question 14

Where is the action potential conducted?

Answer 14

Down the axon to the terminal branches and synaptic terminals.

Question 15

AP is all or none response. what is it?

Answer 15

Once threshold is reached, the AP always fires fully

Question 16

strength of stimulus is proportional to what feature of AP?

Answer 16

frequency

Question 17

What affects conduction velocity?

Answer 17

VGSC density
Axon diameter
Myelination

Question 18

larger or smaller axons conduct faster?

Answer 18

larger axons

Question 19

why do larger axons conduct faster?

Answer 19

have less resistance and more surface area for ion channels (capacitance)

Question 20

role of myelin in conduction?

Answer 20

acts an insulator to speed up AP propagation.

Question 21

What forms myelin in the CNS?

Answer 21

Oligodendrocytes

Question 22

What are Nodes of Ranvier?

Answer 22

Gaps between myelin sheaths

Question 23

myelin sheaths composed of a mixture of …

Answer 23

fat and proteins

Question 24

T/F

myelin sheaths are in discontinuous segments

Answer 24

TRUE

Question 25

Nodes of Ranvier have

Answer 25

VGSCs needed for propagation

Question 26

How does AP travel in myelinated neurons?

Answer 26

By saltatory conduction

Question 27

saltatory conduction?

Answer 27

it “jumps” from node to node for faster signaling

Question 28

T/F myelin allows positive charges move

Answer 28

TRUEE

Question 29

unmyelinated ones will be mediated by

Answer 29

continuous aligning of VGSCs

Question 30

absent of myelin and continuous VGSCs leads to

Answer 30

no AP will be transferred

Question 31

two main types of synapses in the CNS?

Answer 31

electrical and chemical synapses

Question 32

What happens in an electrical synapse?

Answer 32

Ions pass directly through connexons between neurons

Question 33

is an electrical synapse rapid or slow?

Answer 33

rapid

Question 34

which one is major synapse in the body? chemical or electrical

Answer 34

chemical

Question 35

chemical synapse?

Answer 35

- neurons don't touch - NT diffuse across the synaptic cleft to activate receptors on the postsynaptic cell

Question 36

role of calcium in chemical synapses

Answer 36

Ca2+ triggers the fusion of the synaptic vesicles to the plasma membrane

Question 37

Where are neurotransmitters stored before release?

Answer 37

In synaptic vesicles in the presynaptic terminal

Question 38

What proteins mediate vesicle fusion?

Answer 38

SNARE proteins

Question 39

What triggers neurotransmitter release?

Answer 39

AP opens voltage-gated Ca²⁺ channels (VGCCs) → Ca²⁺ influx triggers vesicle fusion.

Question 40

T/F Each vesicle releases a fixed “packet” of the same amount of neurotransmitter

Answer 40

True; it is called quantal release

Question 41

Voltage-Gated Ca2+ channels (VGCCs) are found mainly in ...

Answer 41

pre-synaptic terminals of neurons

Question 42

graded potentials?

Answer 42

Small changes in membrane potential (MP) in response to signals

Question 43

What causes graded potentials?

Answer 43

from opening of ion channels on the target neuron in response of signal

Question 44

T/F graded potentials does not respond to change in potential

Answer 44

true; they response to signals like NT not changes in voltage

Question 45

T/F graded potentials can be either direct or indirect

Answer 45

TRUE ligand-gated and GPCR

Question 46

direction of GP vs AP

Answer 46

GP - depolarization or hyperpolarization AP - always depolarization first then repolarization

Question 47

amplitude of GP vs AP

Answer 47

GP - varies with stimulus AP - constant

Question 48

duration of GP vs AP

Answer 48

GP - varies with stimulus AP - constant

Question 49

summation of GP vs AP

Answer 49

GP can be summated AP cannot

Question 50

refractory period of GP vs AP

Answer 50

GP - no AP - yes

Question 51

conduction of GP vs AP

Answer 51

GP - decreases with distance AP - remains constant

Question 52

channels used for GP vs AP

Answer 52

GP - ligand-gated AP - voltage-gated

Question 53

depolarizing graded potential?

Answer 53

excitatory post-synaptic potentials (EPSPs)

Question 54

EPSPs move towards or away from the threshold potential?

Answer 54

move towards

Question 55

EPSPs are caused by

Answer 55

influx of Na+ and Ca2+

Question 56

Hyperpolarizing GP?

Answer 56

inhibitory post-synaptic potentials (IPSPs)

Question 57

IPSPs move towards or away from the threshold potential?

Answer 57

move away

Question 58

IPSPs are caused by

Answer 58

efflux of K+ or influx of Cl-

Question 59

T/F EPSPs and IPSPs decay over time unlike AP

Answer 59

TRUEE since the strength of the signal decreases with distance

Question 60

Amplitude and distance of GP are determined by

Answer 60

combined effect of multiple excitatory and inhibitory neuronal signals coming in

Question 61

The strength of GP will determine

Answer 61

whether to trigger AP or not

Question 62

AP triggering occurs at the axon hillock due to

Answer 62

high density of voltage-gated Na+ channels for rapid and large amplitude depolarization

Question 63

Lag time

Answer 63

The brief delay while NT diffuse across the synaptic cleft to bind receptors on the postsynaptic neuron

Question 64

↑ input stimulus leads to

Answer 64

↑ amplitude of the GP

Question 65

↑ amplitude of the GP

Answer 65

↑ frequency of AP

Question 66

↑ frequency of AP

Answer 66

↑ amount of NT release