Fundamentals of Neuroscience: Final Lectures 20-24 Flashcards
1
Q
Motor control: Red muscle fibers are large numbers of ________ and ________, slow to contract and can sustain contraction. Antigravity muscles of the leg and torso.
A
mitochondria and enzymes
2
Q
White muscle fibers are ______ (fast or slow) fibers. They have fewer __________ and contract and fatigue _________. These are the arm muscles.
A
Fast fibers, have fewer mitochondria and contract and fatigue rapidly.
3
Q
In regards to white muscle fibers, FR fibers are
A
White fibers with moderate strength and fast contractions.
4
Q
In regards to white muscle fibers, FF muscle fibers are
A
The fastest, strongest white fibers, but rapidly fatiguing.
5
Q
Each motor unit (the motor neuron and all the muscle fibers it innervates) contains muscle fibers of ___________. (multiple type/single type)
A
Only a single type.
6
Q
A single action potential triggers variable contractions. (True/False)
A
True
7
Q
Repeated trains of AP’s lead to different rates of fatigue. (True/False)
A
True
8
Q
Varying the amount of activity of muscles can change muscle fibers. There are two terms for this; _______ and ________.
A
Hypertrophy and Atrophy.
9
Q
Crossed-innervation is
A
When nerve input is switched, i.e; there is a switch in muscle phenotype, which can be induced simply by changing the activity in the motor neuron.
10
Q
Muscle Fiber Structure: When are muscle fibers formed?
A
Early in fetal development via the fusion of muscle precursor cells.
11
Q
Each muscle cell has more than one nucleus. (True/False)
A
True.
12
Q
Muscle fibers are enclosed by an excitable cell membrane called the
A
sarcolemma.
13
Q
Within the muscle fiber are a number of cylindrical structures called _________, which contract.
A
myofibrils
14
Q
What are the steps of muscle excitation/contraction coupling?
A
- Alpha motor neurons release ACh
- ACh produces large EPSP in muscle fibers.
- EPSP evokes muscle action potential.
- Action potential triggers Ca2+ release.
- Fiber contracts.
- Ca2+ reuptake
- Fiber consequently relaxes.
15
Q
Myofibrils are divided into segments or disks by _______ lines.
A
Z lines
16
Q
What is a sarcomere?
A
Two Z lines and a myofibril
17
Q
A series of bristles anchored to Z lines are called
A
Thin filaments
18
Q
Thick filaments exist where?
A
Between and among thin filaments.
19
Q
Where does muscle contraction occur?
A
Muscle contraction occurs when the thin filaments slide along the thick filaments, bringing adjacent Z lines towards one another.
20
Q
Steps in Excitation-Contraction Coupling: Sliding-Filament Assay Model
A
Binding of Ca2+ causes myosin (thick filament protein) to bind to actin (thin filament protein)
The Myosin “heads” pivot, causing the filaments to slide.
ATP unlocks this interaction.
Repetition of process “walks” myosin heads along filament.
21
Q
Death does not cause stiffening of the muscles. (True/False)
A
False. Death DOES cause stiffening of the muscles.
22
Q
Deep within the skeleton muscles are specialized structures known as ______.
A
spindles
23
Q
Spindles serve what purpose?
A
Sensory feedback from muscle spindles = Stretch receptor
The spindles and their associated Ia axons are specialized for the detection of changes in muscle length (stretch) and are examples of proprioceptors (“body sense”).
24
Q
The stretch reflex is regarded as an ______________.
A
Antigravity feedback loop.
25
A weight is placed on a muscle, the muscle spindles are stretched. This leads to depolarizaiton of the Ia axon endings due to the opening of mechanosensitive ion channels. As a result, increased action potential discharge of the Ia axons synaptically depolarizes the alpha motor neurons.
This causes the muscle to contract, thereby shortening it.
This system is known as the
Stretch Reflex
26
Example of a Stretch Reflex:
Knee-jerk reflex.
Muscle pulled -> Tendency to pull back.
Discharge of Ia sensory axons is closely related to the length of the muscle. I.e; As the muscle is stretched, the discharge rate goes up.
As the muscle is shortened and returns back, the discharge rate goes down.
This is a feedback loop with monosynpatic transmission to motor neuron.
27
Many inputs to motor neurons are mediated by ____________________.
spinal interneurons
28
Contraction of one muscle set is accompanied by the relaxation of an antagonistic muscle. This type of inhibition is called
Reciprocal inhibition
29
When withdrawing a limb from an adverse or aversive stimulus, your body uses a
flexor reflex.
30
The flexor reflex requires an excitatory input. (True/False)
True.
31
Describe the circuitry of the flexor reflex.
An aversive stimulus activates interneurons in several different spinal segments. These cells eventually excite the motor neurons that control ALL OF THE flexor muscles of the affected limb.
32
What is the crossed-extensor reflex?
The crossed-extensor reflex is the activation of extensor muscles and inhibition of flexors on opposite sides during flexor reflex.
The purpose of this is to compensate for the extra load imposed by limb withdrawal.
33
Spinal Control of Motor Units:
What are the circuits that give rise to rhythmic motor activity?
Central Pattern Generators
34
What are some examples of central pattern generators?
Spinal motor programs for walking (stride)
Circuitry for walking resides in the spinal cord, the rhythmic activity in spinal interneurons.
Coordination between the two depends on multiple mechanisms.
35
Rhythmic activity in a spinal interneuron: In the resting state, the channels are ______.
Glutamate causes the NMDA receptors to open, depolarize and allows a ________ influx.
_______ activated K+ channels open. The K+ efflux, hyperpolarization. The hyperpolarization allows ______ to enter and clog the NMDA channel, arresting the flow of ________.
As ___________ falls, the K+ channels close, resetting the membrane for another oscillation.
closed, Ca2+, Ca2+,Mg2+, Ca2+, Ca2+
36
Possible circuit for rhythmic alternating activity:
A steady input excites two interneurons that connect to the motor neurons
controlling the flexors and extensors, respectively.
* The interneurons respond by bursts of outputs. The activity of these
interneurons alternates because they inhibit each other via interneurons.
* Activity in one interneuron strongly inhibits the other, and vice versa.
* The movements of the opposite limb could be coordinated so that flexion
on one side is accompanied by extension on the other.
37
The Brain is a product of two mutually interacting factors: __________ and ______________
Heredity/Gene/Genetics and Environment/Life experience/Epigenetics
38
A diagnosable disorder of thought, mood, or behavior that causes distress or impaired function is called a
mental illness
39
Two prior beliefs about mental illness include: _______ and _______
Disorders of the body and disorders of the mind
40
Current belief in regards to mental illness:
Most disorders of mood, thought, and behavior have biological explanations.
41
An adaptive response to threatening situations. This can be innate and species-specific, while others may be learned.
Fear
42
This disorder is caused by inappropriate expressions of fear and is the most common of psychiatric disorders.
Anxiety disorders
43
Fear evoked by a threatening stimulus is known as a _________.
stressor
44
The hallmark of anxiety is the occurrence of an inappropriate stress response either when a stressor is not present or when it is not immediately threatening. (True/False)
True
45
List common symptoms of a stress response:
Avoidance behavior
Increased vigilance and arousal
Activation of the sympathetic division of the autonomic nervous system
Release of cortisol from the adrenal glands
46
Humoral response: Hypothalamic Pituitary-Adrenal (HPA) Axis includes
The Hypothalamus corticotropin-releasing hormone (CRH)
Anterior pituitary: Adrenocorticotropic hormone (ACTH)
Adrenal Cortex: Cortisol (A glucocorticoid)
47
Both the _______ and ______ regulate the HPA Axis.
Amygdala and Hippocampus
48
The Amygdala ________ (activates/deactivates) the HPA axis.
activates
49
The hippocampus ________ (activates/deactivates) the HPA axis.
Deactivates
50
Describe the Push-Pull Regulation of the HPA Axis.
The Amygdala activation stimulates the HPA system and the stress response.
The Hippocampal activation suppresses the HPA System.
The Hippocampus has glucocorticoid receptors that are sensitive to circulating cortisol, feedback regulation of the HPA axis in preventing excessive cortisol release.
Amygdala ---> + [HPA] - <--- Hippocampus
51
Treatments for Anxiety Disorders include: __________ and ___________
Psychotherapy and Anxiolytic medications
52
This treatment increases the exposure of patients to stimuli that produce anxiety, consequently reinforcing the notion that they are not dangerous.
Psychotherapy.
53
These forms of medication are considered (anxiety attenuators), altering chemical synaptic transmission.
Anxiolytic medications
54
New drugs target CRH receptors for ________.
Anxiety disorders
55
Affective Disorders include:
Disorders of Mood
Recurrent Depression
Major Depression
56
Describe Bipolar disorder while distinguishing the two types.
Bipolar disorder or manic-depressive disorder consists of repeated episodes of mania, or mixed episodes of mania and depression
Type 1: Manic episodes with or without major depression
Type II: Hypomania, a milder form of mania, always associated with episodes of major depression.
57
The monoamine hypothesis postulates that
Depression is a consequence of a deficit in a diffuse modulatory system.
Treatment focuses on central serotonergic and/or noradrenergic synapses.
58
Other treatments for Affective Disorders:
Psychotherapy and Electroconvulsive therapy (ECT) : Localized electrical stimulation
59
Electroconvulsive therapy (ECT) affects ________.
Affects the temporal lobe. The mechanism it provides for relieving depression is unknown.
It DOES provide quick relief of depression and mania.
However, it can cause loss of prior memories or impair storage of new information.
60
Other Treatments for Affective Disorders:
Antidepressants
61
List and describe types of antidepressants.
MAO Inhibitors which reduce the enzymatic degradation of serotonin and norepinephrine.
Tricyclics which block the reuptake of both norepinephrine and serotonin by transporters.
Serotonin selective reuptake inhibitors (SSRIs) such as fluoxetine, which act only on serotonin terminals
NE-selective reuptake inhibitors
Ketamine also used to treat.
62
When severe depression fails to respond to other treatments, this may be implanted deep within the brain as treatment:
Electrode. It is implanted into a region of the anterior cingulate cortex
63
Electrical stimulation in electrodes are used to decrease activity in brain circuits that are chronically overactive. The benefit is
immediate relief from depression.
64
The first step in wiring the nervous system is ________.
Neurogenesis
65
The majority of neurons are born before birth. These are created at a rate of ___________ neurons per minute.
250,000
66
Once a neuron reaches _______, it will never divide again
neuronal fate
67
All the neurons that you are born with are all you will have in a lifetime. (True/False)
True.
68
What are the three stages for the development of the neuronal structure?
Cell proliferation, cell migration, and cell differentiation.
69
Adult Neurogenesis: The Subventricular Zone (SVZ) is the zone that.....
The zone that forms the lining of the lateral ventricles.
The SVZ is the site where neuroblasts are formed, which migrate via the rostral migratory stream (RMS) to the olfactory bulb.
70
Adult Neurogenesis: The Subgranular zone (SGZ) is the zone that forms part of...
The zone that forms part of the dentate gyrus of the hippocampus area.
71
The Genesis of Neurons: Cell Proliferation
What cells give rise to neurons and astrocytes?
Radial glial cells/neural progenitors
72
The Genesis of Neurons: Cell Proliferation
After symmetrical cell division in terms of neural cell proliferation in the genesis of neurons, what happens?
After symmetrical cell division, daughters remain in the ventricular
zone to divide again. After asymmetrical cell division, the daughter
cell farthest away from the ventricle ceases division and migrates
away.
73
In cell migration, pyramidal cells and astrocytes migrate vertically from ventricular zone by moving along thin radial glial fibers.
Do the inhibitory interneurons and oligodendroglia generate here?
No, they generate from a different site and migrate laterally.
74
The first neuron cells to arrive become layer VI, followed by V, IV, and so on on. This is referred to as ________ _____.
inside out
75
A cell takes the appearance and characteristics of a neuron after reaching its destination, but programming occurs much earlier. This is called _________
Cell differentiation
76
In terms of cell differentiation, what occurs first? Astrocyte differentiation or neuronal differentiation?
Neuronal. Then astrocyte differentiation. Lastly, Oligodendrocytes are the last cells to differentiate.
77
What are the first cells to differentiate?
Neuronal cells
78
What are the second cells to differentiate? (Second in terms of procession)
Astrocytes
79
What are the last cells to differentiate?
Oligodendrocytes
80
The chemical markers on growing axons are matched with a complementary chemical marker on their target to establish precise connections. This is referred to as
Chemoaffinity hypothesis
81
In terms of the chemoaffinity hypothesis or Axon Growth Guidance, what are the two chemical cues?
Chemoattractant (e.g., netrin)
and
Chemorepellent (e.g., slit)
82
Establishing Retinotopy in Frog Retinotectal Projection: What is ephrin?
Ephrin is one kind of repulsive signal for temporal retinal axons. They are secreted in a gradient across tectum, with the highest levels found on posterior tectal cells.
83
How does ephrin function as a repulsive signal?
Ephrin interacts with a receptor called EPH on the growing axon. By binding, it inhibits further axonal growth.
84
Cells and Synapses are continuously rearranged and reconfigured or undergoing apoptosis to facilitate what?
Efficient connections between input neurons and target neurons. At first, there may be a large number of input neurons for very few target neurons in the initial state.
Following the completion of important trophic factors (apoptosis), fewer input neurons exist to connect to the original few target neurons.
This process is constantly occurring to establish proper resource management and efficiency.
85
Activity-Dependent Synaptic Rearrangement is when...
synaptic rearrangement occurs which is a change from one pattern to another. The final step in address selection.
An example of this is two presynaptic neurons wiring to a target cell, where after, the two presynaptic neurons have changed how many neuronal connections they have with the target cell (and in what pattern)
86
Synaptic Segregation: Within the LGN, axons from the two eyes _________ into the eye specific domains. Silencing retinal activity with TTX (__________) prevents this process.
Segregate, tetrodotoxin
87
Ganglion cells are _______ active during fetal development.
spontaneously
88
Are ganglion cells spontaneously active during fetal development? Yes/No
Yes
89
Process of synaptic stabilization:
Only retinal terminals that are active at the same time as their postsynaptic LGN target neurons, ARE retained.
90
Plasticity and Hebbian Modification
91
Segregation of Retinal Inputs to the LGN: In the visual cortex, inputs from the LGN neurons serving the two eyes are segregated into ocular dominance columns.
Monocular deprivation: Open-eye columns ________ in width while closed-eye columns ________, Can be reversed.
Expand, shrink
92
Monocular deprivation is ______ dependent and ________ dependent.
Activity dependent and experience dependent.
93
What is the critical period?
A period or specific time when developmental fate is influenced by the environment.
94
In the visual cortex, there is experience-dependent plasticity.
There are two rules for synaptic modification:
Fire together; wire together
Fire out sync; lose their link
95
Describe the process of of voltage-dependent NMDA channels:
Glutamate binds to the NMDA receptor and the pore opens.
At resting membrane potentials however, the channel becomes clogged by Mg2_+ ions referred to as "magnesium block".
The Mg2+ ions pop out of the pore ONLY when the membrane is depolarized, which usually follows the activation of AMPA channels.
This means that the NMDA channel is both voltage dependent AND transmitter gated. Meaning BOTH glutamate AND depolarization must coincide before the NMDA channel will pass current.
96
What receptor is both voltage AND transmitter gated?
NMDA receptor
97
What ion clogs the pore of an NMDA channel until the membrane is depolarized AND activated by a transmitter?
Mg2+
98
Long-Term Synaptic Potentiation (LTP) Hypothesis states:
NMDA receptors serve as Hebbian detectors of simultaneous presynaptic and postsynaptic activity.
99
Strong NMDA receptor activation ---> _____________ of synaptic transmission.
Strengthening of synaptic transmission.
100
What is long-term synaptic depression? (LTD)
Neurons firing out of sync.
The synaptic plasticity mechanism is opposite of LTP. This means it weakly activates NMDA receptors. There is a loss of synaptic AMPA receptors and a loss of synapses.
This is a mechanism of consequence of monocular deprivation.
With fewer AMPA receptors, synapses lose influence over
responses of cortical neurons.
101
With fewer AMPA receptors, synapses __________ influence over
responses of ________ neurons.
lose, cortical
102
Why does the critical period end?
When axon growth ceases: due to change in the extracellular matrix or myelination.
When synaptic transmission matures: Properties of NMDA receptors change during the course of critical period.
When cortical activation is constrained: The Activity may be filtered by successive synaptic relays that no longer activate NMDA receptors
103
In terrms of learning and memory, what does "Hebb" refer to?
Memory results from synaptic modifications.
104
Learning and memory are done in two stages: ______ and _______
Acquisition of short term memory
Consolidation of long term memory.
105
Describe memory formating:
Sensory experience --> Memory Acquisition ---> Short-term memory--> Memory consolidation ---> Long-term memory
106
What is acquisition in terms of memory formation?
ACQUISITION of a Short-term memory
Physical modification of a brain caused by incoming sensory information.
The modifying of synaptic transmission between neurons.
107
What is consolidation in terms of memory formation?
CONSOLIDATION of long term memory
Requires new gene expression and protein synthesis
108
What is the tri-synaptic circuit of the hippocampus?
Entorhinal cortex to Dentate Gyrus
Dentate Gyrus to CA3 (Mossy fiber) synapses
CA3 to CA1 (Schaffer collateral) synapses
109
According to Bliss and Lomo, 1973, brief, high-frequency electrical stimulation (tetanus) of excitatory pathways produces...
LTP (Long-term Potentiation)
110
LTP's can be induced by a ______
a brief tetanus
111
LTP's (Long-term potentiation) induced in CA1 of awake animals can last ______________.
many weeks, possibly even a lifetime
112
Mechanisms of LTP in CA1:
Glutamate
receptors mediate
excitatory synaptic
transmission.
NMDA and AMPA
* Ca2+ signals when
presynaptic and
postsynaptic
elements are active
at the same time
113
Mechanisms of LTP in CA1 continued: The rise in [Ca2+]i activates two
protein kinases:
protein kinase C
and calcium-calmodulin-dependent
protein kinase II/CaMKII
114
BCM theory: Synapses undergo synaptic weakening when they are ________
active. At the same time, the postsynaptic cell is only weakly depolarized by other inputs.
115
Homosynaptic long-term depression (LTD): Tetanic stimulation of the Schaffer collaterals at low frequencies (1-5Hz) produce ___________
synaptic weakening
116
Bidirectional plasticity is governed by two simple rules:
Synapses during strong depolarization of the postsynaptic neuron causes _________.
Synapses during weak depolarization of postsynaptic neuron causes __________.
LTP; LTD
Or
Long-term potentiation; Long-term depression
117
How Ca2+ Can Trigger Both LTP and LTD in
the Hippocampus / bidirectional?
When the postsynaptic cell is
weakly depolarized by other
inputs: active synapses
undergo LTD instead of LTP:
different level of NMDA
receptor activation
* AMPA receptors are
dephosphorylated and/or
internalized.
118
Morris experimented with inhibitory avoidance. This was the first evidence in
NMDA-receptor-dependent processes.
119
In terms of memory consolidation, ____________ is insufficient as long-term memory consolidation mechanism.
Phosphorylation
120
Why is phosphorylation not a sufficient mechanism for long-term memory consolidation?
Protein molecules themselves are not permanent. Phosphorylation of a protein is not permanent.
121
What other mechanisms are needed for long-term consolidation?
Protein kinases
Protein synthesis
Epigenetics
122
_________ synthesis is required for formation of long-term memory.
Protein synthesis
123
EEG stands for
Electroencephalogram
124
What does an EEG do?
It is a non-invasive way to record brain waves using electrodes on the scalp with low-resistance connection, connected to banks of amplifiers and recording devices.
125
EEG Rhythms
High-frequency, low-amplitude rhythms are associated with
* Low-frequency, high-amplitude rhythms are associated with
alertness and waking, or the dreaming stages of sleep.
non dreaming sleep states, certain drugged states, or the
pathological condition of coma
126
Deep sleep in terms of EEG Rhythms:
________ synchrony, _______ EEG amplitude.
High, high
