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Psych 314 > Chaper 2 Communication at Synapses > Flashcards

Chaper 2 Communication at Synapses Flashcards

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1
Q

Properties of Synapses [placeholder]

A

.

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2
Q

In the 1800s Ramon y Caljal showed that

A

a synapse sperates one neuron from another

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3
Q

Synapse

A

Seperates one neuron from another as well as links one neuron from another

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4
Q

In 1906 Sherrington inferred

A

inferred several properties of synapses through experiments on the reflex arc:

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5
Q

Delayed Transmission

A

speed of conduction through the reflex arc was slower than the known speed of conduction along an axon

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6
Q

Temporal Summation

A

Several impulses from one neuron over time produce a reflex

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7
Q

Spatial Summation

A

several synaptic inputs (impulses) originating from several neurons at the same time produce and (fire) a reflex

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8
Q

Presynaptic Neuron

A

the neuron that sends the message

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9
Q

Postsynaptic Neuron

A

the neuron that receives the neurotransmitter message

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10
Q

Postsynaptic Action Potentials [placeholder]

A

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11
Q

In 1960 Eccles confirmed Sherrington’s findings using microelectrodes to measure postsynaptic potentials, what did he find?

A
  • stimuli produced excitatory postsynaptic potentials (EPSPs), on membrane
  • repeated stimuli generated EPSPs sufficient to cross the threshold and produce an action potential
  • several stimuli at different locations also generated EPSPs sufficient to produce action potential
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12
Q

Postsynaptic Action Potentials [Info Dump]

A

Action potentials are always depolarizations.

  • Graded potentials are changes from rest (-70) that don’t produce an action potential - can be either excitatory (depolarization) or inhibitory (hyperpolarization)
  • These are called excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs)
  • An EPSP results from Na entering the cell (just like an action potential, but smaller).
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13
Q

Inhibitory Senses [placeholder]

A

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14
Q

Inhibitory Senses [Info Dump]

A
  • Sherrington: when flexor muscles of stimulated leg contracted, the extensor muscles relaxed, inferring an inhibitory synapse
  • Eccles: when flexor muscles contract, an interneuron in spinal cord generates hyperpolarizations, or inhibitory postsynaptic potentials (IPSPs), on extensor muscles of same leg
  • IPSPs increase negative charge on membrane, decreasing the probability of an action potential
  • It does so by opening the gates for K+ ions to leave the cell or for Cl- ions to enter the cell
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15
Q

Relationship Among EPSPs, IPSPs and Action Potential

A
  • Neurons may have thousands of synapses along their membranes, some generating EPSPs others IPSPs
  • A neuron has a periodic rate of firing (action potentials) even without synaptic input is a rate of the combined excitatory and inhibitory potentials
  • rate of firing is determined by the amount of ESPS or ISPS
  • The rate of firing is increases with EPSPs and decreases with IPSPs
  • But, any behavior is a function of many, many neurons
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16
Q

Chemical Events at the Synapse [placeholder]

A

.

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17
Q

Elliot (1905)

A
  • found that the hormone adrenaline (a chemical) applied to surface of heart, stomach and pupils mimics the sympathetic nervous system
  • suggested that synapses use chemicals to link neurons
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18
Q

When Otto Loewi stimulated the vagus nerve attached to frog’s heart, it decreased heart rate

A
  • collected fluid from around heart and transferred to another frog’s heart
  • second heart also slowed its rate
  • concluded that nerves send messages by releasing chemicals (neurotransmitters) at synapse
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19
Q

The sequence of the 6 chemical events of a synapse [placeholder]

A

.

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20
Q

Sequence 1

A

The neuron makes chemicals called neurotransmitters (NTs) and places them in little sacs called vessicles. Smaller ones are made in the terminal button and larger ones are made in the soma

21
Q

Sequence 2

A

The ones in the soma get carried down the axon to the TB

22
Q

Sequence 3

A

At the presynaptic TB, an action potential causes calcium to enter the cell, which causes the NT to be released from the TB into the synapse (or synaptic cleft)

23
Q

Sequence 4

A

The released NTs attach to receptors on the postsynaptic neuron and cause things to happen on that neuron

24
Q

Sequence 5

A

Then the NTs release from the receptors and sometimes are converted into inactive chemicals

25
Q

Sequence 6

A

As many of the NT molecules as possible are taken back into the presynaptic TB for recycling. This is called reuptake.

26
Q

Categories of Neurotransmitters [placeholder]

A

.

27
Q

Amino acids

A

which contain an amine group (examples = glutamate, GABA)

28
Q

Peptides

A

long chains of amino acids, including polypeptides and proteins (ex = endorphins)

29
Q

Acetylcholine

A

similar to amino acids but a little different structurally (Ach)

30
Q

Monoamines

A

nonacidic neurotransmitters containing an amine group (serotonin, dopamine, norepinephrine, epinephrine) =

31
Q

Purines

A

category of chemical including adenosine and several of its derivatives (ATP, adenosine)

32
Q

Gases

A

nitric oxide and maybe others

33
Q

Synthesis of Neurotransmitters [Info Dump]

How do neurotransmitters combine?

A
  • Neurons synthesize neurotransmitters from substances in the diet. Ex:

—> Actycholine is synthesized from choline which is abundant in cauliflower, milk, and beef

—> Tryptophan, a precursor to serotonin which is important in the brain, increases after meal rich in protein (turkey, soy)

  • Smaller neurotransmitters (like Ach) are synthesized in presynaptic terminals, close to release point, larger ones (like peptides) are made in the soma and transported down the axon.
34
Q

Transport and Release of Neurotransmitters cont. [placeholder]

A

.

35
Q

Release and Diffusion

A
  • When the AP reaches the end of an axon, the depolarization opens voltage dependent calcium channels and Ca flows into the TB
  • This causes the release of neurotransmitter through membrane (exocytosis, lasting 1-2 ms)
  • Diffuses across the synapse (a very tiny distance) in about 10 µs (microseconds)
  • Usually two or even three transmitters are released from each neuron
  • They then attach to postsynaptic receptors
36
Q

Activation of Receptors

A
  • The meaning of a NT depends on its receptor…Ach may excite one neuron, inhibit a 2nd and have no effect on another
37
Q

Ionotropic effects

A

Definition

When the NT attaches to a receptor and immediately opens some type of ion gate

Function

  • quick start (10 ms)
  • Immediately opens gates for ions; e.g., acetylcholine
  • Most abundant: glutamate (excitatory), GABA (inhibitory)
  • Ionotropic synapses are used for quick events like visual stimulation, muscle movements, etc.
38
Q

Metabotropic effects

A

Definition

When the NT hits the receptor and initiates a sequence of reactions that are slower and longer lasting than ionotropic effects.

Function

  • late start (30 ms)
  • NT attaching to a metabotropic receptor activates a G-protein inside membrane
  • G-Protein is called the “second messenger” (NT is the first messenger), which communicates with the rest of the cell to do things:
  • opens or closes ion channels, changes protein production, or activates chromosomes in cell
39
Q

Neuromodulators

A
  • these neurotransmitters are mainly peptides
  • chemicals released in small quantities that diffuse farther away in the extracellular fluid than neurotransmitters
  • Often bind with metabotropic receptors
40
Q

Hormones

A
  • chemicals released in larger quantities in blood stream
  • Also travel farther
  • Often bind with metabotropic receptors

Epinephrine, norepinephrine, insulin, oxytocin and some others serve both as neurotransmitters and hormones

41
Q

Inactivation and Reuptake [placeholder and def]

A

Normal functioning neurotransmitters cause a EPSP or IPSP for limited time and then are inactivated or taken back

42
Q

Inactivation

A
  • some neurotransmitters are broken down by an enzyme
  • Ex: Acetylcholine is broken down by Acetylcholinesterase (Ache)
  • If not enough Ache is present, Ach can linger at the synapse and continue to excite it. Some drugs work by blocking Ache to cause this to happen
43
Q

Reuptake

A
  • some neurotransmitters detach from the receptor and are taken back up by the presynaptic cell through special membrane proteins called transporters
  • Ex: serotonin and the catecholamines
  • Again, if the reuptake is blocked, the effects of these NTs are prolonged. SSRIs work this way (selective serotonin reuptake inhibitors)
44
Q

Synapses And Drug Effects [placeholder and def]

A
  • Neurotransmitters act on receptors to mediate behavior such as learning, anxiety, and depression
  • All drugs that affect behavior act on synaptic receptors
45
Q

agonist

A

a drug that mimics or increases the effects of a neurotransmitter

46
Q

antagonist

A

a drug that blocks or takes away from the effects of the neurotransmitter

47
Q

affinity

A

ability of a drug to bind a receptor – like a lock and key

48
Q

efficacy

A

the degree to which the drug activates the receptor once bound

49
Q

Synapses and Personality [Info Dump]

A

Drugs, e.g., tranquilizers, antidepressants, affect people differently

—> drugs affect behavior through several kinds of receptors

—> people vary in number of each kind of receptors, e.g., dopamine D1, D2, D3, D4 and D5

  • D2 receptor related to alcohol consumption, recreational drug use, overeating and habitual gambling
  • Research on alternative form of D4 receptor mixed:

—> related to being impulsive, exploratory and quick-tempered

—> related to schizophrenia

—> no link to personality

Psych 314 (11 decks)

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