L06 Flashcards

1
Q

What is neurogenesis?

A

The production of new neurons.
- Neural progenitor cells produce neurons when they undergo asymmetrical cell division. Human neurogenesis largely stops four months after conception.
- There may be a little neurogenesis in some adult mammals, but this is controversial.

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2
Q

What is apoptosis?

A

A process of programmed cell death that occurs in multicellular organisms.
- Apoptosis is a highly regulated and controlled form of cell suicide that ensures a dying cell does not cause problems for its neighbors.
- Human neural progenitor cells undergo apoptosis 125 days after conception.

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3
Q

How does the brain develop from conception?

A

A hollow, enclosed neural tube forms during the first month of human development. The first cells are neural progenitor cells, and they initially only exhibit symmetrical cell division: each cell becomes two of the same type.
This period of symmetrical cell division ends and asymmetrical cell division starts 40 days after conception (in humans). Over the next 85 days, each time a neural progenitor cell divides, it produces one neural progenitor cell and either one neuron or one glial cell.
By day 125 after conception, there are over 100 billion neurons in the human brain. This is the most neurons we ever have. Many die before birth, seemingly because they can’t find a place in the network.

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4
Q

What is the midbrain and what are its 2 major parts?

A

A collection of nuclei that orchestrate complex reflexive behaviors, such as species typical responses to threat and pain, as well as orienting responses to sounds and lights.
Its 2 major parts are the tectum and the tegmentum.

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5
Q

What is the tectum and what is its function?

A

The tectum (“roof”) appear as two pairs of bumps on the dorsal surface of the midbrain.
The top 2 bumps are the superior colliculi. They are involved in orienting the animal to things seen in peripheral vision.
The bottom 2 bumps are the inferior colliculi. They are involved in orienting to unexpected sounds.

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6
Q

What is the tegmentum and what is its function?

A

The tegmentum includes several structures that coordinate and motivate complex species-typical movements. Some areas of the tegmentum process pain and orchestrate behavioural responses to threats.

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7
Q

What is the hypothalamus and what is its function?

A

The hypothalamus is a bilateral structure made up of several nuclei, which generally regulate autonomic nervous system activity.
They hypothalamus is critically involved in behaviors that directly relate to survival (i.e. the four F’s: feeding, fighting, fleeing and mating).
Different hypothalamic nuclei control body temperature, sleep-wake cycles, hunger, and social behavior, among other things.
One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system (release of hormones into the blood stream) via the pituitary gland.

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8
Q

What is a hormone?

A

A chemical substance that is released by an endocrine gland and that has effects on target cells in other organs.

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9
Q

What is an endocrine gland?

A

A gland that secretes chemical signals (hormones) into the bloodstream. Much of endocrine system is controlled by hormones produced by cells in hypothalamus

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10
Q

What is the thalamus?

A

A bilateral structure that is divided into several nuclei, many of which relay ascending sensory information to different regions of the cerebral cortex.
For example, visual information from the eye passes through the thalamic lateral geniculate nuclei, whereas sound information from the ear passes through the thalamic medial geniculate nuclei.
Many nuclei of the thalamus have widespread cortical projections.

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11
Q

Is the cerebral cortex made up of nuclei?

A

No (except in birds)

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12
Q

What is the cerebral cortex made of?

A

It is made of a multi-layered structure (typically 6 layers in mammals, 3 layers in reptiles). Neurons are interconnected between layers in a way that gives rise to cortical columns, which are thought to be partially distinct functional units.

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12
Q

What is the cerebral cortex made of?

A

It is made of a multi-layered structure (typically 6 layers in mammals, 3 layers in reptiles). Neurons are interconnected between layers in a way that gives rise to cortical columns, which are thought to be partially distinct functional units.

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13
Q

What is the largest site of neural integration in the CNS?

A

The cerebral cortex. It plays a key role in attention, perception, awareness, thought, memory, language, decision making, and consciousness.

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14
Q

The surface of the cerebral hemispheres is the cerebral cortex, which is highly convoluted with _____, _____, and _____.

A

sulci (small grooves), fissures (large/major grooves), gyri (ridges between sulci or fissures)
These convolutions increase the surface area of the cerebral cortex.

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15
Q

What is the outermost portion of the cerebral cortex called and why do we call it that?

A

The gray matter. We call it that because of the high concentration of cell bodies there, which makes it gray.

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16
Q

What does the white matter contain and where is it located?

A

It has a large concentration of myelinated axons. There are very few neurons in this area. It is located beneath the gray matter.

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17
Q

What is the name of the fissure that separates the 2 hemispheres?

A

The longitudinal fissure

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18
Q

What is the name of the fissure that separates the frontal from the temporal lobe?

A

The lateral fissure

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19
Q

What structure provides a good landmark separating the rostral and caudal divisions of the cerebral hemispheres?

A

The central sulcus

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20
Q

What is the corpus callosum and what is its function?

A

A large band of axons that connects corresponding parts of association cortex of the left and right hemispheres. Although the two cerebral hemispheres perform somewhat different functions, perceptions and memories are unified by the corpus callosum.

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21
Q

What are the 4 lobes of the cerebral cortex?

A
  1. The frontal lobe
  2. The parietal lobe
  3. The occipital lobe
    4.The temporal lobe
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22
Q

What does the frontal lobe control?

A

Movement

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23
Q

What does the parietal lobe process?

A

Touch information

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24
Q

What does the occipital lobe process?

A

Visual information

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25
Q

What does the temporal lobe process?

A

Auditory information

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26
Q

Where are taste and smell processed?

A

Near the junction of the frontal, parietal, and temporal lobes inside the lateral fissure.
Taste is processed in the insular cortex. Smell in the piriform cortex.

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27
Q

What does the primary motor cortex in the frontal lobe contain?

A

The motor neurons that synapse in the spinal cord.

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28
Q

Where does touch information first enter the cerebral cortex?

A

In the somatosensory cortex in the parietal lobe.
Different regions of the somatosensory cortex receive information from different parts of the body (ex: feet, hands, fingers).

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29
Q

Where does visual information first enter the cerebral cortex?

A

In the primary visual cortex in the occipital lobe

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30
Q

Where does the auditory information first enter the cerebral cortex?

A

In the primary auditory cortex in the temporal lobe

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31
Q

Where does gustatory information first enter the cerebral cortex?

A

In the insular cortex hidden in the lateral fissure

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32
Q

Where do each primary sensory areas of the cortex send information to?

A

The sensory association cortex

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33
Q

What is it that takes place in the sensory association cortex?

A

Perception takes place there and memories are stored there.
Regions of the sensory association cortex located closest to the primary sensory areas receive information from only one sensory system

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34
Q

What did the basal ganglia use to be called?

A

The primitive “reptilian” brain. It is now clear that reptiles and birds have other components of the cerebrum than the basal ganglia.

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35
Q

The basal ganglia and limbic system are often referred to as _____ _____, since they sit beneath the cerebral cortex.

A

subcortical structures

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36
Q

What is the basal ganglia and its function?

A

The basal ganglia are a collection of nuclei in the forebrain. As a circuit, they regulate intentional movements, motivation, reinforcement learning, and habits.
Inputs to the basal ganglia come from all over the forebrain, especially from the frontal lobe of the cerebral cortex.
Some of its outputs descend to midbrain and hindbrain nuclei that regulate movement.
It also has outputs that ascend to thalamus and cerebral cortex which regulate sensory processing and decision making.

37
Q

What is associated with basal ganglia disfunction?

A

Many neurological disorders.
For example, Parkinson’s disease relates to the loss of dopamine signaling in the basal ganglia.

38
Q

What is the limbic system and what does it regulate?

A

The limbic system is comprised of several distinct, interconnected structures, including the hippocampus, amygdala, and cingulate cortex.
(Some parts of the cerebral cortex, thalamus, and hypothalamus that connect to these structures are also considered to be part of the limbic system.)
It regulates emotions and episodic memories.

39
Q

What is the cingulate cortex and its function?

A

A large area that overlies the corpus callosum.
Cingulate means encircling. This region interconnects many limbic areas of the brain.

40
Q

Where are the hippocampus and the amygdala?

A

In the temporal lobe of the cerebral cortex. They each contain several distinct nuclei.

41
Q

What is the function of the hippocampus?

A

The hippocampus is critical for explicit memory formation.

42
Q

What is the function of the amygdala?

A

The amygdala is critical for feeling and recognizing emotions, particularly fear.

43
Q

What is also part of the limbic system that we don’t talk about?

A

The mammillary bodies, septum, and fornix are also part of the limbic system.

44
Q

What are the 5 principal structures of the forebrain?

A

The cerebral cortex, the basal ganglia, the limbic system, the thalamus, and the hypothalamus

45
Q

What are receptor proteins?

A

A protein that is sensitive to and capable of communicating some signal. We will talk most about receptors that are activated by neurotransmitters. We will also talk about receptors that are activated by light, touch, small, taste, etc.
Receptor are either ionotropic or metabotropic.

46
Q

What is a ionotropic receptor?

A

A receptor protein that is an ion channel. The properties of the pore of the ion channel (the hole) determine if it will produce EPSPs or IPSPs (i.e., if it lets in sodium or chloride ions). The direct effect of ionotropic receptor activation is always an immediate change in the permeability of the membrane to specific ions (i.e., whatever ions pass through the receptor).

47
Q

What is a metabotropic receptor?

A

A receptor protein that is not an ion channel. These receptors typically trigger an intracellular signaling cascade that involves g proteins, which can produce a variety of cellular effects such as a change in gene expression or the opening/closing of g protein-gated ion channels. The effects of metabotropic receptor signaling can be quite large, but they are often delayed (because they rely on signaling cascades and diffusion).

48
Q

All g protein-coupled receptors (GPCRs) are _____ receptors.

A

metabotropic

49
Q

What is the main excitatory neurotransmitter?

A

Glutamate.
It is excitatory because all ionotropic glutamate receptors let sodium in.

50
Q

What is the main inhibitory neurotransmitter?

A

GABA.
It is inhibitory because all ionotropic GABA receptors let chloride in.

51
Q

What are the 4 main modulators?

A

Dopamine, norepinephrine, acetylcholine, and serotonin.

52
Q

What receptors do neuromodulators primarily act on?

A

Neuromodulators act on metabotropic receptors and tend to exert more of a modulatory influence on postsynaptic cell activity (rather than causing fast EPSPs or IPSPs like with glutamate and GABA).

53
Q

More than 99% of neurons release one of 2 neurotransmitters. What are they?

A

Glutamate and GABA

54
Q

What do glutamate agonists cause?

A

They often cause seizures and excitotoxicity.

55
Q

What are examples of glutamate antagonists?

A

Dissociative anesthetics (ketamine, PCP)

56
Q

What do ionotropic glutamate receptors induce?

A

Excitatory post-synaptic currents
(EPSCs) and membrane depolarization, perhaps an action potential.

57
Q

What are examples of glutamate agonists?

A

Kainic acid and NMDA

58
Q

What do ionotropic GABA receptors induce?

A

Inhibitory post-synaptic currents (IPSCs)
and membrane hyperpolarization.

59
Q

What do GABA antagonists often cause?

A

Seizures

60
Q

What are examples of GABA agonists?

A

Anesthetics, anticonvulsants, muscle relaxants, sleeping pills, anti-anxiety pills (alcohol, barbiturates, benzodiazepines)

61
Q

In addition to glutamate or GABA, many neurons also co-release _____ and/or _____.

A

neuromodulators, neuropeptides

62
Q

Why do we distinguish neuromodulators from conventional neurotransmitters?

A

Because neuromodulators:
1.Don’t typically produce simple
excitatory or inhibitory effects in the CNS
2. Most of their receptors are G-protein
coupled receptors, not ion channels
3. Often diffuse short distances outside
of the synapse and can influence the activity of neighboring neurons.

63
Q

How do we also call norepinephrine?

A

Noradrenaline

64
Q

How do we also call adrenaline?

A

Epinephrine

65
Q

What do we consider when classifying a neurotransmitter?

A
  1. What type of molecule is it? Is it a modified amino acid? A peptide? Something else?
  2. How and where is the neurotransmitter made?
    Is it made by enzymes locally in the axon terminal? Or is it made back in the cell body by translating RNA?
  3. How does it get released? Is it packaged into vesicles? If so, what kind of vesicles?
  4. What kind of receptor proteins does it bind to? Both ionotropic and metabotropic receptors? Or only metabotropic receptors?
  5. How does it get cleared away after it is released?
    Is it constrained to the synaptic cleft, or can it diffuse freely? Can it be taken back up by the axon terminal and reused?
66
Q

What are the main conventional neurotransmitters?

A

Glutamate, GABA, dopamine, serotonin, norepinephrine, acetylcholine

67
Q

By using the neurotransmitter classification, how can we qualify conventional neurotransmitters?

A
  1. Mostly amino acid derivatives
  2. Synthesized locally in axon terminals. The necessary enzymes and raw ingredients (generally single amino acids) float around freely in the axon terminal. After a neurotransmitter is made, it gets packaged into vesicles by transporter proteins, which are on the membranes of synaptic vesicles.
  3. They are usually secreted from small synaptic vesicles that dock very close to the site of
    Ca2+ entry in the axon terminal
  4. They generally activate ionotropic AND metabotropic receptors. They usually bind receptors directly across the synapse.
  5. They are typically recaptured after secretion and reused
68
Q

By using the neurotransmitter classification, how can we qualify neuropeptides?

A
  1. Short strings of amino acids (~ 10-30 amino acids)
  2. Synthesized in the cell soma, transported down the axon while undergoing additional processing, and released just once
  3. Usually secreted from large dense core vesicles that dock a ways back from the site of Ca2+ entry in the axon terminal
  4. ONLY activate metabotropic receptors
  5. No synaptic recycling occurs of either the neuropeptides or their immediate precursors.
    + May diffuse long distances and exert action at a distance (non-synaptic communication)
69
Q

What are some of the main neuropeptides?

A

Oxytocin, vasopressin, enkephalin, prolactin, NPY, ghrelin, CRH (there are >70).

70
Q

By using the neurotransmitter classification, how can we qualify lipid-based signaling molecules?

A

2-5. They are synthesized and released on demand, as needed (details are murky).
3. They are secreted in a non-vesicular manner, typically from postsynaptic neurons
4. ONLY activate metabotropic receptors, typically located on the presynaptic axon terminal

71
Q

All classical (conventional) neurotransmitters get manufactured in _____ _____.

A

axon terminals

72
Q

What are examples of monoamines?

A

Serotonin, dopamine, and norepinephrine.
They have a very similar chemical and three-dimensional structure.

73
Q

How do we call the protein that packages all of the monoamines into synaptic vesicles?

A

The vesicular monoamine transporter (VMAT)

74
Q

What are examples of catecholamines, a category within monoamines?

A

Dopamine and norepinephrine

75
Q

What is an example of an indolamine, a category within monoamines?

A

Serotonin

76
Q

Each of the monoamines have their own _____ _____ _____ (SERT, DAT, NET), which traffic the neurotransmitter from the synapse back into the axon terminal.

A

reuptake transporter protein

77
Q

How does acetylcholine act in the CNS?

A

Acetylcholine primarily acts as a neuromodulator, often at axoaxonic synapses.

78
Q

How does acetylcholine act in the PNS?

A

Acetylcholine is released by motor neurons at the neuromuscular junction, where it activates the fast excitatory ionotropic receptors on muscle cells that cause muscle contraction.

79
Q

Motor neurons generally release _____ as their main neurotransmitter.

A

acetylcholine

80
Q

Sensory neurons generally release _____ as their main neurotransmitter.

A

glutamate

81
Q

What does much of our knowledge of drugs and neurotransmitter signaling come from?

A

Studying the venom of different species which interfere with neurotransmitter signaling.
Many of them interfere with neurotransmitter signaling at the neuromuscular junction, which can cause paralysis (no movement) or spasms (excessive muscle contraction).

82
Q

What does one of the toxin in the black widow spider venom cause?

A

A massive release of neurotransmitter vesicles, particularly those that contain acetylcholine. This causes muscle cramps, pain, and nausea.
One bite from this spider can kill you.

83
Q

What produces botulinum toxin (botox) and what happens when it is injected?

A

Botox is produced by bacteria that grow in improperly canned food. It is an acetylcholine system antagonist, because it prevents the release acetylcholine causing muscle paralysis.

84
Q

What is neostigmine?

A

A drug that inhibits the activity of acetylcholinesterase, which is the enzyme that breaks down acetylcholine in the synaptic cleft. Neostigmine causes acetylcholine to hang around in the synapses for a longer period of time.

85
Q

What is Myasthenia Gravis?

A

A hereditary autoimmune disorder in which the person’s own immune system attacks their healthy acetylcholine receptors. People with this disorder become noticeably weaker and weaker over time (fatigability).

86
Q

Neostigmine is a drug that is used to help patients that have what disease?

A

Myasthenia Gravis. We don’t yet have a good way to give these people back their functional acetylcholine receptors, but with drugs like Neostigmine, we can make the released acetylcholine stay around for longer periods of time.

87
Q

What is a drug?

A

An exogenous chemical that at relatively low doses significantly alters the function of certain cells.

88
Q

What is psychopharmacology?

A

The study of effects of drugs on the nervous system and behavior

89
Q

What is a site of action?

A

The location at which molecules of a drug interact with molecules located on or in cells of body, affecting some biochemical processes of these cells