Exam 3 Flashcards
What are the 3 regions of the brain?
Hindbrain
Forebrain
Midbrain
What are the components of the hindbrain?
Medulla
Pons
Cerebellum
What are the components of the midbrain?
substantia nigra
What are the components of the forebrain?
Cerebral cortex
Basal ganglia (striatum, globus pallidus, subthalamic nucleus)
Limbic system (hippocampus, amygdala)
Diencephalon (thalamus, hypothalamus)
What structures are associated with the forebrain?
“higher” structures
What are the functions of the medulla?
Autonomic functions (involuntary)
Controls: respiration, cardiac function, vasomotor responses, reflexes (coughing, etc)
What are the functions of the pons?
Acts as a “bridge” between the cerebellum and the forebrain
-relays signals from the forebrain to the cerebellum
What are the functions of the cerebellum?
“little brain”
Governs motor coordination for producing smooth movements
What is an important point to remember about cerebellum neurodegeneration?
Undergoes neurodegeneration in spinocerebellar ataxias
(causes disjointed or jerky movements “ataxias”)
*how we know if this area is damaged
What are the two parts of the substantia nigra?
SN pars compacta
SN pars reticulata
What is the function of the SN pars compacta?
Provides INPUT to the basal ganglia
*supplies dopamine to the striatum (goes wrong in Parkinson’s)
-Voluntary motor control and cognitive functions
What part of the midbrain is involved in the development of Parkinsons disease?
SN pars compacta
-The supply of dopamine by this area to the striatum gets interrupted
-This area undergoes neurodegeneration in Parkinsons
What is the function of the SN pars reticulata?
Output function
Relays signals from the basal ganglia to the thalamus
What is the function of the cortex (cerebrum)?
Processing and interpreting information
-decision making, higher level functions
What is the function of the basal ganglia?
Voluntary motor control
Some cognitive functions
What are the two parts of the limbic system?
Amygdala
Hippocampus
What is the function of the amygdala?
Emotions
What is the function of the hippocampus?
Memory
What are the two parts of the diencephalon?
Thalamus
Hypothalamus
What is the function of the thalamus?
“Relay station” to and from the cortex
What are the functions of the hypothalamus?
Controls involuntary functions
-Internal homeostasis
-Emotions
-Hormonal control
-Direct neural regulation
Which structures are associated with controlling involuntary functions?
Medulla
Hypothalamus
Which structures are associated with controlling voluntary functions?
SN pars compacta (movement with intention)
Basal ganglia
What is a cortico-thalamic loop?
The senses receive information about the environment and pass it through the thalamus to the cortex and then back
-This loop makes decisions about how to interpret and react to the incoming sensory information
*What area of the brain is schizophrenia associated with?
Frontal cortex
Which of the following brain structures is directly involved in controlling involuntary functions?
A. hypothalamus
B. thalamus
C. medulla oblongata
D. A, B, and C
E. A and C
E.
hypothalamus and medulla
What are the 3 functions of astrocytes?
-Provide neurons with growth factors + antioxidants
-Remove excess glutamate
–Support the blood-brain barrier
Why is it important for astrocytes to remove glutamate?
Too much glutamate leads to excess calcium which overwhelms mitochondria
-mitochondria spit out free radicals which leads to cell death
(too much glutamate is toxic)
What is the function of oligodendrocytes?
Produce myelin sheath that insulates axons
What are the 3 functions of microglia?
-Provide growth factors
-Clear debris through phagocytosis
-Neuroinflammation
What is an important point to remember about microglia’s function?
They are PRO-INFLAMMATORY
What is the overarching role of microglia that makes them easier to remember?
They are the “immune cells of the brain”
Which of the glial cells make up the blood-brain barrier?
Astrocytes
How does the blood-brain barrier act as a barrier?
Cells are held very tight together by tight junctions leaving no spaces between them
-this is what forms the barrier since it is too tight to cross
What triggers neurotransmission?
Electrical depolarization of the neuron
(influx of Na+)
At the beginning of an action potential, is the inside of the cell positive or negative?
Negative
-why it is below threshold to start
True or False: an action potential leading to neurotransmitter release will only occur when threshold is reached or passed
True
What causes repolarization?
Action potentials open to move K out of the cell
Cl- moves into cell
-this reestablishes the original negative charge
What is an afterpotential?
The action potential dips below resting potential between repolarization and depolarization
(an overshoot of repolarization)
**part of the refractory period
How long do action potentials last?
0.2-0.5 msec
What is a refractory period?
The period after an action potential when a neuron will not fire again
(hyperpolarized phase)
True or False: The magnitude of an action potential will always be the same for a single neuron
True
*the height of the action potential spike on a graph of them will always be the same
What happens when we apply an excitatory neurotransmitter?
Action potentials occur more frequently
*depolarizing
What happens when we apply an inhibitory neurotransmitter?
Action potentials occur less frequently
*polarizing
Why is the current carried by a nerve fiber (bundle of axons) greater?
Summation
What are EPSP’s?
Excitatory postsynaptic potentials
*weak signals that do not clear the threshold
-induced by excitatory neurotransmitters
What are IPSP’s?
Inhibitory postsynaptic potentials
*these lower the polarity far below baseline so that it is harder to clear the threshold and produce an action potential
How does an excitatory neuron cause an Excitatory Postsynaptic Potential?
Allows Na+ ions to cross the membrane
How does an inhibitory neurotransmitter induce hyperpolarization?
Allows Cl- ions to cross the membrane
What is hyperpolarization?
When a cell is so negative that it is below the resting potential
True or False: an IPSP can decrease the magnitude of an EPSP
True
-because an IPSP makes it harder to reach the threshold
-even though EPSP’s do not reach the threshold, they still will lower and farther away from the threshold than normal
NOTE
Review lecture 1 slide 20
What are the 3 common amino acid neurotransmitters?
GABA*
Glycine
Glutamate*
*= focus in CNS
What are the 2 types of GABA receptors?
GABA (A)
GABA (B,C)
What type of receptor is GABA (A)?
Ion channel
What type of receptor is GABA (B)?
GPCR
What is GABA?
The major inhibitory neurotransmitter in the brain
-depresses neuronal excitability (by increasing Cl- influx)
What drugs interact with GABA?
CNS depressants
-Sedative hypnotics
-Anticonvulsants
-Anxiolytics
What kind of neurotransmitter is GABA?
Inhibitory
-hyperpolarizes the neuron
What conditions are affected by GABA?
Epilepsy
Spasticity
Addiction/Alcohol
*What is glycine?
Similar to GABA
*but acts in the spinal cord
What are the 3 Glutamate Receptors?
AMPA, NMDA (ion channel)
mGluR (GPCR)
What is glutamate?
EXCITATORY neurotransmitter in the brain
How can excess glutamate cause neuronal damage?
By allowing excessive Ca+ influx into the neuron
(overexcites the neuron, leads to cell death)
What disease states are associated with glutamate?
Epilepsy
Schizophrenia
Which neurotransmitter (GABA or Glutamate) is excitatory and which is inhibitory?
GABA: inhibitory
Glutamate: excitatory
What are the 4 common non-amino acid neurotransmitters?
-Acetylcholine
-Dopamine (DA)
-Norepinephrine
-Serotonin (5-HT)
What are the two types of acetylcholine receptors?
Nicotinic
Muscarinic
Where do acetylcholine receptors act?
Periphery
-basal forebrain
-pons
-cortex
-basal ganglia
*What are examples of drugs that target acetylcholine transmission?
Cholinesterase inhibitors
-Aricept (used in Alzheimer’s disease)
What disease states are associated with acetylcholine?
Cognitive function/decline
Nicotine dependence
Movement disorders
What are the two dopamine receptors?
D1-like (GS coupled)
D2-like (Gi coupled)
What are the functions of the D1-like receptor and the D2-receptor?
D1-like: increase cAMP
**Gs coupled
D2-like: decrease cAMP
**Gi coupled
Drugs that block dopamine transmission can lead to what?
They increase extracellular dopamine concentrations which can produce euphoria and lead to addiction
(ex: cocaine, amphetamine)
Excessive dopaminergic signaling can contribute to which disease state?
Schizophrenia
Loss of dopamine neurons in the SN is responsible for which disease state?
Parkinson’s disease
What drugs interact with the dopamine pathways?
Antipsychotics (D2 receptor antagonists)
D2/D3 and D1 receptor agonists used in Parkinson’s disease
What disease states are associated with dopamine transmission?
Schizophrenia
Parkinson’s disease
Addiction
Depression
ADHD
Where does dopamine transmission occur?
Midbrain
-substantia nigra
-pars compacta
-ventral tegmental area (reward + addiction)
What are the receptors for norepinephrine?
a1, a2 (GPCR)
What are the drug targets of norepinephrine?
a- and B- adrenergic receptors
norepinephrine transporter (NET)
Norepinephrine transporter (NET) inhibitors are used to treat what disease state?
Depression
Where does norepinephrine transmission occur?
Pons
What disease states are associated with norepinephrine transmission?
-Memory
-Depression
-Addiction
-Pain
What are the 2 serotonin receptors?
5-HT3
5-HT1,2
Where does serotonin transmission occur?
Midbrain
Pons
**raphe nuclei in these areas produce serotonin
*What is the function of raphe nuclei?
Give rise to 5-HT axons
What drugs interact with 5-HT receptors?
5-HT2A antagonists (atypical antipsychotics)
SERT uptake inhibitors (depression)
5-HT2A agonists (hallucinogenic, ex: LSD)
What disease states are associated with serotonin transmission?
-Depression
-Mood disorders/anxiety
-Schizophrenia
What is multiple sclerosis (MS)?
An immune-mediated (inflammatory) disorder involving destruction of the myelin sheath surrounding neuronal axons
What are some areas in the body that are affected by MS?
-Optic nerve (vision)
-Corticospinal tract (fatigue)
-Cerebellum (walking problems)
-Sensory pathways (pain)
-Vestibular pathways (dizziness)
For an environmental insult to cause MS, what age must exposure occur AFTER?
15
How can viral or bacterial infections increase the risk of MS?
By activating autoreactive immune cells
-leads to an autoimmune response in genetically susceptible individuals
What specific virus may be involved in the development of MS?
Epstein-Barr Virus (EBV)
How can Epstein-Barr Virus (EBV) cause MS?
Sequence similarities between EBV and self-peptides can result in activation of autoreactive T or B cells
**molecular mimicry
Which antigen is responsible for the molecular mimicry of Epstein-Barr Virus in MS?
Epstein-Barr nuclear antigen (EBNA)
(resembles myelin basic protein, antigens recognize the host’s myelin basic protein)
**leads to myelin sheath destruction
How does MS demonstrate a gene-environment interaction?
Patients with a particular HLA phenotype have increased risk of developing MS when they also have anti-EBNA antibodies
The first time that an inflammatory demyelinating episode surpasses the clinical threshold is known as what?
CIS
Clinically Isolated Syndrome
After the CIS, if more inflammatory demyelinating episodes that surpass the clinical threshold occur what are these known as?
RRMS
Relapsing Remitting MS
When there are no more inflammatory demyelinating episodes but the underlying MS disease continues to progress this is called what?
SPMS
Secondary Progressive MS
**inflammatory part is less present but damage and symptoms continue
What % of MS cases are Relapsing-Remitting MS (RRMS)?
85%
What % of MS cases are Primary progressive MS (PPMS)?
15%
What is Primary Progressive MS (PPMS)?
Resembles SPMS
-mean age of onset is later (40)
True or False:
If a patient has Relapsing-Remitting MS (RRMS) they will never have Primary Progressive MS (PPMS)
True
NOTE
See lecture 2 sides 7+8
How is the overall clinical presentation of MS in a patient determined?
A combination of the underlying degeneration (uniform/progressive) AND the host’s immune reaction to it (intermittent/variable)
What are the 2 phases of MS?
Autoimmune
Degenerative
Which phase of MS is the disease trigger?
UNCLEAR
What is the function of dendritic cells?
Present CNS antigens
What is the pathophysiology of MS?
Dendritic cells present CNS antigens and activate T-cells
B and T cells proliferate and infiltrate the CNS using a4-integrin-mediated binding to penetrate the BBB
B cells mature to plasma cells after encountering an antigen, release antibodies
T cells interact with target ligands on MHC molecules, activate, and results in cytokine release and macrophage stimulation
This causes myelin sheath damage
What cells do T cells engage with in the MS autoimmune response?
Oligodendrocytes
*destroy these human cells
-antibodies trigger complement activation and cause pore formation and cell damage
-macrophages are recruited and release toxic agents
How do macrophages harm the myelin sheath?
The release of toxic agents and phagocytosis
Do action potentials travel faster or lower in myelinated regions of axons?
Faster
-due to the insulating effects of myelin
What happens to action potentials in the Node of Ranvier?
Action potentials slow down
-current density builds up
(note: this is a zone of demyelination)
Voltage-gated Na+ channels in the node of Ranvier are used to do what to action potentials?
Essential for replenishing action potentials
How does demyelination affect the propagation speed of action potentials?
Slows them down
How does remyelination occur?
Recruits OPCs (oligodendrocyte precursor cells) to the lesion
These turn into myelin-producing oligodendrocytes
Why does remyelination typically fail in MS?
Lack of OPCs or failure of OPCs to differentiate
What is astrogliosis?
Invasion and propagation of astrocytes that results in irreversible gliotic plaque formation or scars
What cells are activated by demyelination?
Microglia
Astrocytes
What is the function of microglia and astrocytes in remyelination?
Release pro-migratory factors and mitogens
-These recruit OPCs (oligodendrocyte precursors) to the lesion and stimulate their proliferation
What is the key step in remyelination that often fails in MS?
OPC differentiation
What are the 2 pathways that demyelinated axons can take?
Remyelination
Degradation
What is the function of immunomodulatory therapies in MS?
Interfere with T or B cell activation, proliferation, and binding to the BBB
What is the function of rescue strategies in MS?
Remyelination
What contrast agent is used to visualize MS brain lesions?
Gadolinium
What is Guillain-Barre Syndrome?
Acute, inflammatory neuropathy
-Starts as weakness in distal muscles and lower extremities and can progress to total paralysis with death from respiratory failure in days
-Caused by an autoimmune attack on peripheral nerves resulting in demyelination
What are the 3 categories of MS treatment?
- Treatment of Acute Attacks
- Disease-Modifying Therapies (DMTs)
- Symptomatic Therapies
What is the goal of disease-modifying therapies with MS?
-Reduce relapse rates
-Slow progression of disability
Are disease-modifying MS therapies used to treat relapsing or progressive forms of the disease more?
Relapsing
What are the 4 first-line agents for MS?
Interferon B1a (Avonex, Rebif)
Interferon B1b (Betaseron, Extavia)
Glatiramer Acetate (Copaxone)
Fingolimod (Gilenya)
What are the 2 second-line agents for MS?
Natalizumab (Tysabri)
Mitoxantrone (Novantrone)
What are the 3 new drugs for MS?
Teriflunomide (Aubagio)
Dimethyl fumarate (Tecfidera)
Cladribine (Mylinax)
What are the medications used for treatment of acute MS attacks?
Methylprednisolone
Prednisone
Adrenocorticotropic hormone (ACTH)
What are the 2 corticosteroids used for acute MS attacks?
Methylprednisolone
Prednisone
How do corticosteroids work for treatment of acute MS attacks?
Up-regulate anti-inflammatory genes
Down-regulate pro-inflammatory genes
Alleviate edema in demyelinated areas
Where do Interferon B1a and B1b work?
Periphery
BBB
What is the function of Interferon B1a and B1b in the periphery?
Inhibit autoreactive lymphocytes
(T cells, dendritic cells)
What is the function of Interferon B1a and B1b in the BBB?
Inhibit BBB penetration by decreasing matrix metalloproteinase (MMP)
What reduces the efficacy of Interferon B1a and B1b?
neutralizing antibodies
What is the MOA of Glatiramer acetate?
Synthetic polypeptide
Mimics antigenic properties of myelin basic protein
**Modulates antigen-presenting cells (dendritic cells) which leads to decreased T cell activation
What is the MOA of Fingolimod?
Sphingosine-1-phosphate (S1P) receptor agonist
-stimulates oligodendrocyte survival (remyelination)
[CNS]
-interferes with lymphocyte movement out of lymphoid organs
[Periphery]
What is an important side effect to note with Fingolimod?
-Progressive multifocal leukoencephalopathy (PML)
[potentially lethal brain infection]
What are considerations to make when deciding which first-line MS treatment to use?
Fingolimod is superior to interferon beta
*BUT Fingolimod has more side effects associated with it
What is the MOA of Natalizumab?
*2nd line
Monoclonal antibody specific for a4 integrin*
a4-integrin pairs with B1-integrin to produce “very late antigen” (VLA-4)
Inhibiting VLA-4 binding to its ligand (VCAM-1 on CNS vascular endothelium) interferes with B and T cell movement across the BBB into the CNS
(interferes with binding of B and T cells to the BBB and makes it difficult to cross)
What are some side effects to be aware of with Natalizumab?
Progressive multifocal leukoencephalopathy (PML)
Induces neutralizing antibody development which can cause allergic reactions
What is the MOA of Mitoxantrone?
*2nd line
Anthracenedione with CYTOTOXIC ACTIVITY
-reduces lymphocyte numbers by causing DNA strand breaks via intercalation
-Delays DNA repair via inhibition of topoisomerase II
When should Mitoxantrone be considered for use?
Secondary Progressive MS (SPMS)
**first cytotoxic drug approved for this
Also can be used for induction therapy and then replaced with 1st-line agent
Where does Mitoxantrone act?
Periphery
What is the MOA of Teriflunomide?
New agent
Cytotoxic agent
-Inhibits proliferation of peripheral lymphocytes (B and T)
Where does Teriflunomide act?
Periphery
What is the MOA of Dimethyl fumarate, Diroximel fumarate, and Monomethyl fumarate?
New Agents
Metabolized in the GI tract
-Activate Nrf2-mediated cellular antioxidant responses and anti-inflammatory pathways
-Promote remyelination
-Suppress activated T cells and dendritic cells in periphery
What is the active form:
Dimethyl fumarate Diroximel fumarate
Monomethyl fumarate
Monomethyl ester
Where do Dimethyl fumarate, Diroximel fumarate, and Monomethyl fumarate act?
Periphery
and
CNS
What side effect is a concern with Dimethyl fumarate, Diroximel fumarate, and Monomethyl fumarate?
Progressive multifocal leukoencephalopathy (PML)
Where does the Nrf2 antioxidant response pathway occur?
In astrocytes
What antioxidant degrades Nrf2?
Keap1
How does the Nrf2 pathway work?
Normally, Nrf2 is continually targeted for destruction by Keap1
When a cell is exposed to toxins or undergoes oxidative stress, Keap1 is covalently modified and cannot degrade Nrf2
Nf2 accumulates and enters the nucleus where it activates gene transcription regulated by the antioxidant response element (ARE)
These genes are involved in glutathione biosynthesis and detoxification
*Anti-oxidant and Anti-inflammatory
What is the MOA of Siponimod, Ozanimod, and Ponesimod?
New drugs
sphingosine-1-phosphate (S1P) receptor agonists
***Same as fingolimod
-oligodendrocyte survival
-remyelination
-interfere with lymphocyte movement out of lymphoid organs
When do we use Siponimod, Ozanimod, and Ponesimod?
Relapsing Remitting MS (RRMS)
Secondary progressive MS (SPMS)*
What is the MOA of Cladribine?
new drug
*Cytotoxic prodrug
Taken up into cells by purine nucleoside transporters
Damages DNA and interferes with DNA metabolism
-results in cell death and lymphocyte depletion
What was the original use of Cladribine?
Chemotherapeutic agent used for leukemia
What is an important point to remember about the Cladribine structure?
Prodrug
What is Rituximab approved to treat?
Non-Hodgkin lymphomas
Rheumatoid arthritis
What MS patients should we consider using Rituximab in?
Primary Progressive MS patients
*effective in some
also for Relapsing Remitting MS (RRMS)
What is the MOA of Ocrelizumab?
new drug
Monoclonal antibody that targets CD20 (marker on mature B cells)
*only targets mature B cells, good because we still need B cells
What is the name of the antisense oligonucleotide in clinical trials for MS?
ATL1102
What is the MOA of ATL1102?
Antisense oligonucleotide that targets VLA-4
*predicted to have the same outcome as natalizumab
(oligonucleotides recognize mRNA and prevent production of protein from them)
Which of the following drugs is (are) active in both the periphery and the CNS?
a. dimethyl fumarate
b. natalizumab
c. rituximab
d. teriflunomide
e. none of the above
A. Dimethyl fumarate
What are 2important diagnostic criteria for MS?
Dissemination in Time (DIT)
Dissemination in Space (DIS)