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Psychology 375 > Chapter 5 - Neuronal Communication > Flashcards

Chapter 5 - Neuronal Communication Flashcards

1
Q

What did Otto Loewi discover in 1936?

A
  • Won the Nobel Prize by discovering the first neurotransmitter acetylcholine (ACh)
  • Did it through an experiment done with frog hearts that were held in different jars connected by a tube. One heart was stimulated, and it was recorded that the other heart also became stimulated, even though it wasn’t directly stimulated. This was due to the spread of ACh between the two connected jars filled with water.
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2
Q

What effect does ACh have on humans?

A
  • Activates skeletal muscles in the somatic nervous system
  • Excites or inhibits internal organs in the ANS
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3
Q

What’s the effect of norepinephrine in humans?

A
  • Increases the heart rate in humans
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4
Q

Chemical synapse vs. Electrical synapse?

A
  • Chemical - Junction at which messenger molecules are released when stimulated by an action potential
  • Electrical - Specialized connections between neurons that facilitate direct ionic and small metabolite communication (not really a pre-post synapse)
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5
Q

What are gap junctions involved in?

A
  • Found in electrical synapses
  • Area of contact between adjacent cells formed by hemichannels composed of connexin proteins
  • Allows for no delay in response
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6
Q

What are some of the major differences between chemical and electrical synapses?

A
  • Chemical synapses are asymmetrical while electrical synapses are symmetrical
  • Chemical: unidirectional; electrical: bidirectional
  • Chemical synapses have a synaptic cleft while electrical synapses are interconnected via gap junctions
  • Chemical synapses use transduction (chemical signal into an electrical signal via change in membrane potential)
  • Chemical synapses are much more common than electrical synapses
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7
Q

What are some advantages of chemical synapses?

A
  • Very flexible as they can change structures (functional strengthening)
  • Synaptic plasticity, which is very important for learning and memory
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8
Q

What are some advantages of electrical synapses?

A
  • Instantaneous signal transfer, which allows for synchronization between huge populations of neurons
  • Must note they are static, not plastic
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9
Q

What are the roles of some structures such as microtubules, synaptic vesicles, and storage granules during synaptic transmission?

A
  • Microtubules - Transport structure that carries substances to the axon terminal (like train tracks, especially for big protein neurotransmitters)
  • Synaptic vesicles - Holds neurotransmitters and takes them to the presynaptic membrane for exocytosis
  • Storage granule - Large compartment that holds synaptic vesicles
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10
Q

What does anterograde synaptic transmission refer to?

A
  • Synaptic transmission where neurotransmitters are released from the presynaptic side to the postsynaptic neuron
  • This is in contrast to retrograde synaptic transmission which is bidirectional
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11
Q

What are the five steps of anterograde synaptic transmission?

A

1) Synthesis of neurotransmitters made from precursor modules
2) Packaging and storage - neurotransmitters moved into vesicles and wait for action potentials
3) Release - NTs released through the membrane via exocytosis
4) Receptor action - transmitter enters synaptic cleft and binds to a receptor
5) Inactivation - the transmitter either diffuses away, is enzymatically degraded, is taken into the neuron terminal or is taken up by an astrocyte

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12
Q

What are the 7 different types of synapses?

A

1) Dendrodentritic
2) Axodendritic (the one we focus on the most)
3) Axoextracellular (axon terminal > extracellular fluid)
4) Axosomatic (axon terminal > cell body)
5) Axosynaptic (axon terminal > axon terminal)
6) Axoaxonic
7) Axosecretory (axon terminal > tiny blood vessel)

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13
Q

What are connexins?

A
  • Found in electrical synapses
  • Protein subunits that form the hemichannels forming gap junctions
  • Require 6 connexins to form a hemichannel called a connexon
  • Need two connexons to form a gap junction, meaning you need 12 connexins to form a full gap junction
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14
Q

How do inhibitory and excitatory synapses differ in morphology?

A
  • Inhibitory: less NT receptors; smaller active zone; flatter vesicles; narrower synaptic cleft
  • Excitatory: Larger active zone; more NT receptors; rounder vesicles; wider synaptic cleft
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15
Q

Why are there more inhibitory synapses found near the cell body than excitatory synapses?

A
  • Acts as a safety mechanism
  • For an action potential to be triggered, the excitatory synapses need to overcome the inhibitory synapses near the cell body
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16
Q

What’s the active zone?

A
  • The space along the presynaptic membrane where exocytosis occurs
17
Q

T/F: Multiple NTs may influence a single synapse.

A
  • TRUE
  • Also, each NT may interact with a variety of receptors
18
Q

What are the 4 criteria for identifying a neurotransmitter?

A

1) Transmitter must be synthesized or present in neuron
2) When released, transmitter must produce a response in target cell
3) Same receptor action must be obtained when transmitter is experimentally placed on te receptor
4) There must be a mechanism for removal after the transmitter work is done.

19
Q

What are the different classes of neurotransmitters?

A
  • Small-molecule transmitters
  • Peptide transmitters
  • Lipid transmitters
  • Gaseous transmitters
  • Ion transmitters
20
Q

What are common characteristics of small-molecule NTs?

A
  • Class of quick-acting NTs
  • Synthesized from dietary nutrients and packaged ready for use in axon terminals
  • Once released, are quickly replaced at presynaptic membrane
21
Q

What are some small-molecule NTs to remember?

A
  • Acetylcholine (ACh), Dopamine (DA), Serotonin (5-HT)
    Acetylcholine is in a class of its own
  • Dopamine and serotonin are both made from amines (amino acid precursors with an NH group attached)
22
Q

What are the four major activating systems?

A
  • Cholinergic system
  • Dopaminergic system
  • Noradrenergic system
  • Serotonergic system
23
Q

What’s the main purpose of the cholinergic system?

A
  • Active in maintaining attention and waking EEG pattern
  • Thought to play a role in memory by maintaining neuron excitability
  • Death of these neurons thought to be related to Alzheimer disease
24
Q

What major nuclei are considered the source of ACh in the brain?

A
  • The basal forebrain nuclei and the midbrain nuclei
25
Q

What’s the function of dopamine?

A
  • Synthesized from tyrosine
  • Involved in coordinating movement, attention, learning, motivation, and reward processing
  • Implicated in Parkinson disease
26
Q

What’s the main cause of Parkinson disease?

A
  • Degeneration of neurons in the substantia nigra (appears black in scans)
  • Symptoms appear when DA levels have been reduced to less than 10% of normal levels in the basal ganglia
27
Q

What are the two major pathways for the dopaminergic system?

A

1) Nigrostriatal pathway - active in maintaining normal motor behaviour. Loss of DA is related to muscle rigidity and dyskinesia in Parkinson disease.
2) Mesolimbic pathway - causes repetition of behaviours, and the system most affected by addictions

28
Q

What do increasingly high and increasingly low dopamine levels appear to be related to?

A
  • High dopamine - those with schizophrenia
  • Low dopamine - those with ADHD
29
Q

What are some characteristics of serotonin (5-HT)?

A
  • Synthesized from the amino acid tryptophan
  • Major role in regulating waking activity, mood and aggression, appetite, sleep, memory, respiration, pain perception
30
Q

T/F: The serotonergic system is involved in maintaining the waking EEG pattern.

A
  • TRUE
31
Q

What mental disorders are lower levels of serotonin linked to?

A
  • Depression and OCD
32
Q

What may arise from abnormalities in the brainstem 5-HT neurons?

A
  • Potentially sleep apnea and Sudden Infant Death Syndrome (SIDS)
33
Q

What are some common characteristics of GABA and glutamate?

A
  • Part of the amino acid group of small-molecule neurotransmitters.
  • Considered the “work horses” of the brain
  • Glutamate = main excitatory NT
  • GABA = main inhibitory NT
34
Q

What are the two classes of neurotransmitter receptors?

A
  • Ionotropic receptor - embedded membrane protein that acts as both a binding site for NT and a pore that regulates ion flow
  • Metabotropic receptor - embedded membrane protein with a binding site for an NT (no pore, not a channel). Often linked to a G-protein which is composed of three sub-units
35
Q

How do G-proteins work in metabotropic receptors?

A
  • Made up of three subunits
  • When NT attaches to receptor, alpha component will break off from protein and attach to an ion channel hich will open
  • These second messengers can also initiate intracellular signalling cascades, resulting in the addition of additional neurotransmitter receptors.

Psychology 375 (11 decks)

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