Potentials and Synapses

Question 1

What is a non gated channel?

Answer 1

A leaky channel; it doesn’t need to be opened; it is not an ion channel

Question 2

What is a ligand gated channel?

Answer 2

Channel that needs a chemical messenger to open

Question 3

What is a phosphorylation gated channel?

Answer 3

Channel that requires ATP to open

Question 4

What is a voltage gated channel?

Answer 4

Channel that requires a change in membrane potential to open

Question 5

What is a mechanically gated channel?

Answer 5

Channel that needs to be physically opened

Question 6

What is resting membrane potential (mV)?
Why is this?

Answer 6

-70mV
Results from many (permeable) non gated K channels and Na/K pumps sending 3 Na out and 2 K in

Question 7

What is depolarization?

Answer 7

Membrane potential is more positive than RMP

Question 8

What is hyperpolarization?

Answer 8

Membrane potential is more negative than RMP

Question 9

What is a receptor or generator potential?

Answer 9

Graded local signal that occurs at the input zone of the first cell in a sensory pathway

Question 10

What is a synaptic potential?

Answer 10

Graded local signal that occurs in the input zone of a postsynaptic neuron

Question 11

After a mechanical, electric, or chemical stimulus occurs in the input zone of a neuron, what happens first?

Answer 11

Na gated ion channels of the input area open, changing the voltage of the membrane

Question 12

Once Na gated ion channels of the input area have opened, what does the influx of Na cause?

Answer 12

Voltage gated ion channels will open and a receptor or synaptic potential is generated

Question 13

What is required for an action potential to be conducted?

Answer 13

Receptor potential must reach the spike initiation zone of the neuron and depolarize it to threshold (-40mV)

Question 14

At threshold, what channels are activated and in which order do they open?

Answer 14

Na and K voltage gated ion channels are activated at the same time. Na voltage gated channels open first, then K voltage gated channels open.

Question 15

What is happening during the rising phase and overshoot of an action potential?

Answer 15

Na enters and depolarizes the membrane

Question 16

What is happening during the falling phase and undershoot of an action potential?

Answer 16

K exits and hyperpolarizes the cell membrane
Absolute and relative refractory periods

Question 17

What is the absolute refractory period?

Answer 17

Time during an action potential when it is impossible to initiate another action potential (falling phase)
Voltage gated Na channels go to resting state (close and lock)

Question 18

What is the relative refractory period?

Answer 18

Time during an action potential when the threshold required to create another action potential is elevated (undershoot)
Voltage gated K channels cause hyperpolarizion until they close back up, Na channels are able to open now

Question 19

What is resting membrane potential determined by?

Answer 19

Non gated ion channels which distribute major ions across the membrane (ie. Na/K pump)

Question 20

What is the ion distribution in the motor neuron at rest?

Answer 20

Na and Cl in extracellular fluid
K and organic anions in intracellular fluid

Question 21

What determines resting membrane ion permeability?

Answer 21

Number of non gated ion channels in the membrane

Question 22

What is the function of the Na/K pump?

Answer 22

The Na/K pump moves the ions against their concentration gradient keeping Na out and K in. It send 3 Na out and 2 K in the cell.

Question 23

What are the types of synaptic transmission?

Answer 23

Electric and chemical

Question 24

What is electric synaptic transmission?

Answer 24

Direct ionic transfer though gap junctions

Question 25

What is chemical synaptic transmission?

Answer 25

Neurotransmitter release into the synaptic cleft; neurotransmitter receptors gate ion channels directly or indirectly

Question 26

When an action potential reaches the terminal end of the membrane, what does depolarization cause?

Answer 26

Voltage gated Ca channels open. Influx of Ca allow synaptic vesicles to dock into active zones of presynaptic membrane.

Question 27

Once synaptic vesicles dock into active zones, what happens?

Answer 27

Active zones release neurotransmitters into synaptic cleft by exocytosis.

Question 28

After neurotransmitters are released into the synaptic cleft, what happens?

Answer 28

Postsynaptic membrane takes the neurotransmitters by endocytosis. Synaptic vesicles in presynaptic cell are restored.

Question 29

What is the excitatory postsynaptic potential?

Answer 29

The product of an individual excitatory synapse

Question 30

What is the inhibitory postsynaptic potential?

Answer 30

The product of an individual inhibitory synapse

Question 31

What is the synaptic potential?

Answer 31

The graded sum of the excitatory (EPSP) and inhibitory (IPSP) inputs on the postsynaptic membrane

Question 32

What is temporal summation?

Answer 32

Consecutive synaptic potentials at the same site are added together in the postsynaptic cell.

Question 33

What is spatial summation?

Answer 33

The inputs of many presynaptic neurons acting at different sites on the postsynaptic neuron are added together.

Question 34

A neurotransmitter is excitatory if:

Answer 34

their receptors gate positive ions into the intracellular fluid

Question 35

A neurotransmitter is inhibitory if:

Answer 35

their receptors gate negative ions in the intracellular fluid

Question 36

Where are metabotropic receptors and what do they do?

Answer 36

They’re found in the presynaptic membrane; they function in inhibiting further neurotransmitter release or stimulating neurotransmitter synthesis.

Question 37

What is an asymmetrical/axodendritic synapse?

Answer 37

It’s excitatory releasing from an axon terminal to a dendrite

Question 38

What is a symmetrical/axosomatic synapse?

Answer 38

It’s inhibitory releasing from an axon terminal to a postsynaptic soma

Question 39

What do axoaxonic synapses do?

Answer 39

Modulate the amount of neurotransmitter released

Question 40

What are neuroactive peptides?

Answer 40

Neuromodulators found in the entire CNS but also in other functional systems such as the endocrine, digestive, immune etc.

Question 41

What occurs at transmitter (ligant) gated ion channels (ionotropic)?

Answer 41

The neurotransmitter binds to the receptor and causes the ion channel to open
directly.

Question 42

What occurs at second messenger coupled receptors (metabotropic/ tyrosine kinases)?

Answer 42

The neurotransmitter binds to the receptor which activates a second messenger cascade which in turn opens, closes or modulates ion channels.