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PSYC 211 > L04 > Flashcards

L04 Flashcards

1
Q

What is a promoter?

A

A region of DNA that initiates transcription of a particular gene. They indicate what kind of cells should read the gene and when.

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2
Q

How many genes does the human genome have for voltage-gated potassium channels?

A

40, each cell can choose to express one or any combination of them to optimize cell function.

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3
Q

When did voltage-gated potassium channels appear in history?

A

Over a billion years ago

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4
Q

Have voltage-gated potassium channels changed since their apparition?

A

A little, but not really. Most of their gene variants have been conserved for hundreds of millions of years, meaning they haven’t changed much in that time - since the evolution of the nervous system in bilateral creatures.

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5
Q

What is an astrocyte?

A

A glial cell that provides physical support and cleans up debris in the brain through phagocytosis. They control the chemical composition of the surrounding environment and help nourish neurons.

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6
Q

What is a microglia?

A

It is the smallest of the glial cells. They provide an immune system for the brain and protect the brain from invading microorganisms.

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7
Q

What is a oligodendrocyte?

A

A glial cell that produce the myelin sheath, which encapsulates axons. The sheath is not continuous; it is a series of segments.

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8
Q

How do oligodendrocytes form myelin sheath?

A

During development of the CNS, oligodendrocytes form processes shaped like canoe paddles. Each of those processes then wraps itself many times around a segment of an axon and, while doing so, produces layers of myelin that make up part of the axon’s myelin sheath. A single oligodendrocyte forms many myelin sheaths segments on adjacent axons.

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9
Q

What is the only place where a myelinated axon comes into contact with extracellular fluid?

A

At the node of Ranvier, where the axon is naked

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10
Q

What is saltatory conduction?

A

The conduction of action potentials by myelinated axons.

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11
Q

What is a synapse?

A

A junction between the axon terminal of the sending neuron and the cell membrane of the receiving neuron.

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12
Q

How is the communication across the synapse achieved?

A

By the release of neurotransmitters from an axon terminal

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13
Q

What are the possible effects of neurotransmitters?

A

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

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14
Q

What are synaptic vesicles?

A

They are vesicles that contain neurotransmitters. They attach to the presynaptic membrane and release neurotransmitter into the synaptic cleft.

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15
Q

What is the presynaptic membrane?

A

The membrane of the terminal button (the sending cell). This is where neurotransmitters are released from.

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16
Q

What is the synaptic cleft?

A

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

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17
Q

What is the postsynaptic membrane?

A

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

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18
Q

What does electron microscopy allow us to see?

A

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

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19
Q

What is an example of a microscope used with electron microscopy?

A

A transmission electron microscope

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20
Q

What are ligands?

A

Signaling molecules that bind to the binding site of a protein receptor. Neurotransmitters are ligands.

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21
Q

Most cell signaling and cell communication occurs through _____ interactions.

A

ligand-receptor

22
Q

What are the 2 categories of neurotransmitter receptors?

A
  1. Ionotropic receptors
  2. Metabotropic receptors
23
Q

What are ionotropic receptors?

A

A neurotransmitter receptor that is an ion channel. It opens when the ligand (neurotransmitter) binds to it. The properties of the pore of the ion channel (the hole) will determine if it causes EPSPs or IPSPs (i.e., if it lets in sodium or chloride ions). Also called ligand-gated ion channels

24
Q

What are metabotropic receptors?

A

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

25
Q

Where can receptors be located?

A

On the cell membrane (surface receptors) or inside the cell (intracellular pool of receptors)

26
Q

Where are neurotransmitter receptors generally located?

A

On the cell membrane. They are surface receptors.

27
Q

Where are postsynaptic receptors located?

A

On the postsynaptic membrane

28
Q

Where are presynaptic receptors located?

A

On the presynaptic membrane

29
Q

Where are extrasynaptic receptors located?

A

Somewhere near but outside the synapse

30
Q

What is a binding site?

A

The location on a receptor protein to which a ligand binds

31
Q

What is a postsynaptic receptor?

A

A receptor protein in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter

32
Q

What is enzymatic deactivation?

A

The destruction of a neurotransmitter by an enzyme after its release (ex: the destruction of acetylcholine by acetylcholinesterase)

33
Q

What is reuptake?

A

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

34
Q

What are two mechanisms that allow the neurotransmitter signaling to be kept brief in the synapse?

A

Enzymatic deactivation and reuptake

35
Q

What is postsynaptic potential?

A

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

36
Q

Postsynaptic potentials can either be _____ or _____.

A

excitatory/depolarizing (influx of positive sodium ions depolarize the cell), inhibitory/hyperpolarizing (influx of negative chloride ions hyperpolarize the cell)

37
Q

What is depolarization?

A

When the membrane potential of a cell becomes less negative than it normally is at rest (An acute influx of positive ions such as Na+ through a receptor protein ion channel can depolarize a neuron from -60 to -50 mV.)

38
Q

What is hyperpolarization?

A

When the membrane potential of a cell becomes more negative than it normally is at rest.
(An acute influx of negative ions such as Cl- through a receptor protein ion channel can hyperpolarize a neuron from -60 to -70 mV.)

39
Q

What does EPSP mean?

A

Excitatory PostSynaptic Potential (EPSP)

40
Q

What is an excitatory postsynaptic potential (EPSP)?

A

The excitatory depolarization of the postsynaptic membrane typically caused by a neurotransmitter binding to a postsynaptic ionotropic receptor that lets in positively charged sodium ions.

41
Q

What are EPSPs mediated by?

A

They are mediated by receptor proteins that open ion channels permeable to sodium (Making the membrane more permeable to sodium will depolarize the cell)

42
Q

If only a couple EPSPs occur at one time, will the influx of sodium cause an action potential?

A

Probably not. The depolarizing effect of the incoming sodium ions will just be counteracted by an increase in the outflow of potassium ions through the leak channels.

43
Q

What is needed to trigger an action potential?

A

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. This depolarization also has to reach the beginning of the axon (the axon hillock) where voltage-gated sodium channels are congregated and can trigger an action potential.

44
Q

What does IPSP mean?

A

Inhibitory PostSynaptic Potential

45
Q

What is an inhibitory postsynaptic potential (IPSP)?

A

The inhibitory hyperpolarization of the postsynaptic membrane typically caused by a neurotransmitter binding to a postsynaptic ionotropic receptor that lets in negatively charged chloride ions.

46
Q

What are IPSPs mediated by?

A

They are mediated by receptor proteins that open ion channels permeable to chloride. (Making the membrane more permeable to chloride will hyperpolarize the cell.)

47
Q

What is neural integration?

A

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

48
Q

What happens when EPSPs and IPSPs occur at the same time?

A

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.

49
Q

What determines the direction of the postsynaptic potential (EPSP vs IPSP)?

A

The receptor (not the neurotransmitter)

50
Q

What are neuroglias (Glial cells)

A

Glia are found all around neurons and even physically encapsulate some parts of them. They help traffic nutrients and maintain molecular (ionic) stability in the extracellular space. They support many functions of the nervous system. It is estimated that glia cells outnumber neurons in the brain somewhere between 2:1 and 5:1.

51
Q

Do myelinated areas have ion channels?

A

In myelinated areas there are almost no ion channels, and those that are there are of no consequence because there is no extracellular fluid outside the membrane.

PSYC 211 (8 decks)

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