Lecture 4

Question 1

The Action Potential in Five Proteins are:

Answer 1

You know the 2 proteins that set up the resting membrane potential:

Sodium-Potassium transporter (requires ATP; concentrates sodium and potassium outside and inside the cell, respectively)

Leak potassium channels (always open; sets up the resting membrane potential)

The action potential involves 3 other proteins: voltage-gated ion channels

Voltage-gated sodium channel (to initiate and propagate the action potential)

Voltage-gated potassium channel (to restore the resting membrane potential)

Voltage-gated calcium channel (located at the end of the axon, the axon terminal, and cause the release of neurotransmitter-containing vesicles)

Question 2

We know the DNA letters (the exact string of nucleic acids) do what

Answer 2

encode these proteins in numerous species

Question 3

A portion of the DNA that encodes the voltage-gated potassium channel: what letters encode it

Answer 3

AGA

Question 4

AGA encodes what

Answer 4

These 3 letters encode the amino acid arginine

Question 5

In genetics, apromoteris what

Answer 5

a region of DNA that initiates transcription of a particulargene. They indicate what kind of cells should read the gene and when.
Promotersare typically located just before the gene.

Question 6

what is A synapse

Answer 6

is a junction between the axon terminal of the sending neuron and a portion of the cell membrane of the receiving neuron

Question 7

Communication generally proceeds in one direction only, what is it (synaptic communication)

Answer 7

FROM the axon terminal TO the membrane of the other cell.

Question 8

A synapse is a junction between the axon terminal of the sending neuron and a portion of the cell membrane of the receiving neuron.

Communication generally proceeds in one direction only: FROM the axon terminal TO the membrane of the other cell.

This communication across the synapse is achieved how

Answer 8

by the release of a chemical from an axon terminal

Question 9

A synapse is a junction between the axon terminal of the sending neuron and a portion of the cell membrane of the receiving neuron.

Communication generally proceeds in one direction only: FROM the axon terminal TO the membrane of the other cell.

This communication across the synapse is achieved by the release of a chemical from an axon terminal. This chemical is called a what

Answer 9

neurotransmitter

Question 10

what kind of effect does a neurotransmitter have

Answer 10

can have a simple excitatory or inhibitory effect or a complex modulatory effect on the receiving neuron

Question 11

what are the main parts of the synapse

Answer 11

Presynaptic membrane
Synaptic vesicles

Synaptic cleft
Postsynaptic membrane

Question 12

what is the Presynaptic membrane

Answer 12

the membrane of the terminal button (the sending cell). This is where neurotransmitter is released from.

Question 13

what is the Synaptic vesicles

Answer 13

contain molecules of neurotransmitter. They attach to the presynaptic membrane and release neurotransmitter into the synaptic cleft

Question 14

what is the Synaptic cleft

Answer 14

is the space between the pre- and postsynaptic membranes. It is filled with an extracellular fluid.

Question 15

what is the Postsynaptic membrane

Answer 15

is the membrane of the receiving cell that is opposite the axon terminal

Question 16

what is Electron microscopy

Answer 16

allows us to see small anatomical structures (e.g. synaptic vesicles and details of cell organelles) using a special electron microscope.

Question 17

Neurotransmitters are what kind of molecules

Answer 17

signaling

Question 18

Signaling molecules that bind to protein receptors are called what

Answer 18

ligands

Question 19

Most cell signaling and cell communication occurs through what kind of interactions

Answer 19

ligand-receptor interactions.

Question 20

Receptors can either be located where

Answer 20

on the cell membrane (surface receptors) or somewhere inside the cell (intracellular receptors).

Question 21

Neurotransmitter receptors are generally what kind of receptors

Answer 21

surface receptors

Question 22

Postsynaptic receptors are located where

Answer 22

on the postsynaptic membrane

Question 23

Presynaptic receptors are located where

Answer 23

on the presynaptic membrane

Question 24

Extrasynaptic receptors are located where

Answer 24

somewhere outside of the synapse.

Question 25

Neurotransmitter receptors can also be classified as what

Answer 25

ionotropic receptors or metabotropic receptors

Question 26

Neurotransmitter receptors can also be classified as ionotropic receptors what are these

Answer 26

ion channels

Question 27

Neurotransmitter receptors can also be classified as metabotropic receptors what are these

Answer 27

protein receptors that can open ion channels through an intracellular signaling cascade

Question 28

what are the 4 main Communication Between Neurons

Answer 28

Ligand Binding site Postsynaptic Receptor Ligand-gated ion channel

Question 29

what do Ligand do

Answer 29

General term for a signaling molecule (chemical) that binds to the binding site of a receptor. Neurotransmitters are ligands.

Question 30

what is the Binding site

Answer 30

Location on a receptor protein to which a ligand binds

Question 31

what is Postsynaptic Receptor

Answer 31

Receptor protein in postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter

Question 32

what are Ligand-gated ion channel

Answer 32

A receptor that is an ion channel. Also known as an ionotropic receptor. The ion channel opens when the ligand (e.g., the neurotransmitter) binds to it.

Question 33

Neurotransmitter signaling in the synapse is kept brief by two mechanisms which are...

Answer 33

reuptake and enzymatic deactivation

Question 34

what is Reuptake

Answer 34

Reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating postsynaptic potential

Question 35

what is Enzymatic deactivation

Answer 35

Destruction of a neurotransmitter by enzyme after its release For example, destruction of acetylcholine by acetylcholinesterase

Question 36

what is Postsynaptic potential

Answer 36

Alterations in the membrane potential of a postsynaptic neuron, produced by neurotransmitter release into the synapse and receptor activation.

Question 37

Postsynaptic potentials can either be ...

Answer 37

excitatory (often due to an influx of positive sodium ions) or inhibitory (often due to an influx of negative chloride ions).

Question 38

what is Excitatory postsynaptic potential (EPSP)

Answer 38

Excitatory depolarization of postsynaptic membrane caused by neurotransmitter binding to a postsynaptic receptor protein

Question 39

Excitatory postsynaptic potential (EPSP) are mediated how

Answer 39

by receptor proteins that open ion channels permeable to sodium. (Making the membrane more permeable to sodium will push the membrane potential towards +40 mV.)

Question 40

what is Neural integration

Answer 40

If only a couple EPSPs occur at one time, the influx of sodium ions will likely not cause an action potential. The depolarizing effect of the incoming sodium ions will be counteracted by an increase in the outflow of potassium ions through the leak channels. Really anytime positive sodium ions come in, the likelihood that positive potassium ions will leave increases. Thus to trigger an action potential, many EPSPs have to occur at nearly the same time. Sodium ions have to come in at a faster rate that potassium ions can leave in order to depolarize the membrane to the threshold of activation. And, this depolarization has to reach the beginning of the axon (the axon hillock) where voltage-gated sodium channels are congregated and can trigger an action potential.

Question 41

what is Inhibitory postsynaptic potential (IPSP)

Answer 41

Inhibitory hyperpolarization of postsynaptic caused by neurotransmitter binding to a postsynaptic receptor protein.

Question 42

IPSPs are mediated how

Answer 42

by receptor proteins that open ion channels permeable to chloride. (Making the membrane more permeable to chloride will push the membrane potential towards -80 mV.)

Question 43

The interaction of the excitatory and inhibitory synapses on a particular neuron is called what

Answer 43

neural integration

Question 44

When EPSPs and IPSPs occur at the same time what happens

Answer 44

the influx of negatively charged chloride ions diminish the impact of the positively charged sodium ions. IPSPs decrease the likelihood that the cell will fire.

Question 45

what are the 3 main points of Communication Between Neurons:Postsynaptic Potentials

Answer 45

Postsynaptic potentials can be either depolarizing (excitatory) or hyperpolarizing (inhibitory) What determines the direction of the postsynaptic potential (EPSP vs IPSP) is not neurotransmitter, but rather the receptor Some serotonin receptors cause EPSPs and others cause IPSPs. It is up to the postsynaptic cell to determine how it wants to respond the signaling molecule.

Question 46

Postsynaptic potentials can be what

Answer 46

either depolarizing (excitatory) or hyperpolarizing (inhibitory)

Question 47

What determines the direction of the postsynaptic potential (EPSP vs IPSP) is not neurotransmitter but...

Answer 47

rather the receptor

Question 48

Some serotonin receptors cause EPSPs and others cause IPSPs what determines how it wants to respond

Answer 48

It is up to the postsynaptic cell to determine how it wants to respond the signaling molecule.

Question 49

what is an Ionotropic Receptor | and what does it do

Answer 49

A neurotransmitter receptor that is an ion channel. The properties of the pore of the ion channel (the hole) will determine if it causes EPSPs or IPSPs (i.e., if it lets sodium or chloride ions through).

Question 50

what is Metabotropic receptor | and what does it do

Answer 50

Neurotransmitter receptor that triggers an intracellular signaling cascade that often involves g proteins. The signaling cascade can lead to ion channel opening or other cellular effects.

Question 51

what is G protein-gated ion channel | and what does it do

Answer 51

G proteins are a family of intracellular proteins that are involved in intracellular signaling cascades. Some ion channels are gated by g proteins.

Question 52

regarding Metabotropic Receptors | G-protein signaling cascades can affect multiple downstream processes, including;

Answer 52

opening g protein-gated ion channels changes in gene transcription secretion of substances from the cell really anything the cell wants.

Question 53

When the dendrites of a sensory neuron are stimulated by a noxious stimulus (such as contact with a hot object), what happens

Answer 53

it sends messages down the axon to terminal buttons located in spinal cord. The sensory neuron will activate an interneuron, which in turn will active a motor neuron and cause a withdrawal reflex

Question 54

When the dendrites of a sensory neuron are stimulated by a noxious stimulus (such as contact with a hot object), it sends messages down the axon to terminal buttons located in spinal cord. The sensory neuron will activate an interneuron, which in turn will active a motor neuron and cause a withdrawal reflex however what might also happen

Answer 54

However, a neuron deep in the brain may have other plans. For example, a cortical neuron could send an action potential down the spinal cord to excite an inhibitory interneuron, which is a neuron that generally causes IPSCs in downstream neurons. This interneuron would induce IPSCs in the motor neuron and block (counteract) the withdrawal reflex This circuit provides an example of a contest between two competing tendencies: to drop the casserole and to hold onto it

Question 55

An inhibitory neuron is a neuron that does what

Answer 55

reliably causes IPSCs in downstream neurons (i.e., it reduces the spiking activity of downstream neurons).

Question 56

An inhibitory neuron is a neuron that reliably causes IPSCs in downstream neurons (i.e., it reduces the spiking activity of downstream neurons). Keep in mind that the net result of inhibitory neuron activity may ...

Answer 56

not be to inhibit an animal’s behaviour.

Question 57

Sometimes, inhibitory neuron activity can cause a movement. This is often the case if...

Answer 57

the inhibitory neuron has synaptic connections on other inhibitory neurons. Inhibition of inhibitory neurons can make a behaviour more likely to occur.

Question 58

An inhibitory neuron is a neuron that reliably causes IPSCs in downstream neurons (i.e., it reduces the spiking activity of downstream neurons). Keep in mind that the net result of inhibitory neuron activity may not be to inhibit an animal’s behaviour. Sometimes, inhibitory neuron activity can cause a movement. This is often the case if the inhibitory neuron has synaptic connections on other inhibitory neurons. Inhibition of inhibitory neurons can make a behaviour more likely to occur. what is The big picture

Answer 58

For every neuron trying to change behaviour in one way, there are probably other neurons trying to do the opposite. Both groups of neurons are often regulated by inhibitory neurons. And in turn the inhibitory neurons themselves may be regulated by other inhibitory neurons. It is not uncommon to find long chains of inhibitory neurons in a row, which can make it really hard to determine which ones are trying to cause or prevent a behaviour. The take home point is that: Neural excitation is not the same thing as behavioural excitation. Neural inhibition is not the same thing as behavioural inhibition.

Question 59

Synapses can form between axon terminals and …

Answer 59

dendrites (dendritic shafts) dendritic spines the soma (cell body) other axon terminals

Question 60

what are the 2 Axoaxonic Synapses

Answer 60

Presynaptic inhibition and Presynaptic facilitation

Question 61

what is Presynaptic facilitation

Answer 61

The purpose of an axoaxonic synapse can be to increases the amount of neurotransmitter released by the second neuron when it has an action potential. It depolarizes the axon terminal of that neuron, so when an action potential comes more calcium channels open.

Question 62

what is Presynaptic inhibition

Answer 62

The purpose of an axoaxonic synapse can be to reduce the amount of neurotransmitter released by the second neuron when it has an action potential. It hyperpolarizes the axon terminal of that neuron so its calcium channels may not open at all or for very long when an action potential arrives.

Question 63

what is an Autoreceptor

Answer 63

Receptor located on the presynaptic neuron, the neuron that is releasing the neuro-transmitter

Question 64

Autoreceptors are gated by what

Answer 64

the neurotransmitter that the cell releases

Question 65

Autoreceptors are generally metabotropic and inhibitory. They are a main source of ....

Answer 65

presynaptic inhibition

Question 66

where are Post-synaptic | receptors located

Answer 66

Post-synaptic | receptor: receptor located on the receiving neuron, the one that is not releasing the neurotransmitter

Question 67

Cells are sensitive to certain molecules because why

Answer 67

of what they represent, the information they convey. These are called signaling molecules and they trigger a cellular response (beyond digestion).

Question 68

Most signaling molecules fit into two broad categories which are

Answer 68

``` Amino acids (including proteins and amino acid derivatives) Lipids (including fats and steroids) ```

Question 69

When signaling molecules are released into the circulatory system (the bloodstream) they are called what

Answer 69

hormones

Question 70

When signaling molecules are released into the circulatory system (the bloodstream) they are called hormones. The same substance released in the brain would be called what

Answer 70

a neurotransmitter

Question 71

what are the The Principal Neurotransmitters

Answer 71

Conventional neurotransmitters Neuropeptides Lipid-based signaling molecules

Question 72

what are Conventional neurotransmitters

Answer 72

mostly amino acid derivatives The main players: glutamate, GABA, dopamine, serotonin, norepinephrine, acetylcholine are synthesized locally in axon terminals are usually secreted from small synaptic vesicles (SSVs) that dock very close to the site of Ca2+ entry in the axon terminal generally activate ionotropic and metabotropic receptors  are typically recaptured after secretion  usually bind receptors directly across the synapse. Even when neurotransmitters diffuse, they only act over distances of tens to hundreds of micrometers

Question 73

what are Neuropeptides

Answer 73

short string of amino acids (i.e., a protein formed with only ~ 10-30 amino acids) Examples from the list of >70: oxytocin, vasopressin, enkephalin, prolactin, NPY, ghrelin, CRH are synthesized in the cell soma, transported down the axon while undergoing additional processing, and released just once. are usually secreted from large dense core vesicles (LDCV) that dock a ways back from the site of Ca2+ entry in the axon terminal only activate metabotropic receptors (neuropeptides do not activate ionotropic receptors) no synaptic re-use occurs of either the neuropeptides or their immediate precursors. may diffuse long distances and exert action at a distance (non-synaptic communication)

Question 74

what are Lipid-based signaling molecules

Answer 74

(e.g., the cannabinoids anandamide and arachidonoylglycerol) are synthesized and released on demand (as needed) are secreted in an unknown, non-vesicular manner typically from postsynaptic neurons activate metabotropic receptors typically located on the presynaptic axon terminal