Quiz 1: Neurodevelopment, Myelin Disorders, Synapses

Neurons are primarily organized as - or -. Information in the brain is based on - of - (- or -)

Sensory or Motor

Patterns of activity (temporal or spatial)

Name the mechanisms of disease from acute to subacute to chronic!

Vascular, trauma/mechanical, toxic/metabolic, infectious, autoimmune, demyelinating, neurodegenerative, congenital/genetic

Gastrulation produces what 3 germ layers? What is the significance?

Endoderm, Mesoderm, Ectoderm

• Ectoderm gives rise to Brain and PNS

List the two fates for ectodermal cells and how they come about!

1. Neuron (default or BMP inhibitor)

2. Epidermal cell (BMP)

When neurons are formed, they become the - -

Neural Plate

BMP is secreted by -, while inhibitors are secreted by the - -

ectoderm, organizer region

Neurodevelopment requires events to occur in specific - and -

spaces and times

How does the neural plate become the neural tube and how does it close?

Middle of plate has emergence of neural groove, edges fuse to create neural tube (neural crest left out). Tube closes in the middle, then anterior, then posterior

What does the neural crest end up forming?

PNS, meninges

List the two Neural Tube Defects and how they are caused!

• Types

• Mediated by what?

1. Anencephaly (failure of rostral/anterior closure)

2. Spina Bifida (failure of caudal/posterior closure)

• SB occulta (p arch), Meningocele (dura/arachnoid protrusion), Meningomyelocele (SC/NR protrusion)

• Folate

Meningomyelocele is often co-ocurring with -. List the types!

Arnold Chiari Malformation

• Type I: cerebellar tonsil herniates FM

• Type II: ct + vermis herniate FM, compresses ventricles

• Type III: compression of bstem

The 3 main regions of the brain formed by the neural tube are -, - , -.

• They are formed by a - gradient (less -, more -) secreted by cells near the - -

Forebrain, midbrain, hindbrain.

• Wnt (- anterior, + posterior) neural plate

What are the three primary vesicles? What do they differentiate into?

1. Prosencephalon (Diencephalon + Telencephalon)

2. Mesencephalon (Mesencephalon)

3. Rhombencephalon (Metencephalon + Myelencephalon)

What do the secondary vesicles each produce?

• Telencephalon: cerebral hemispheres; lateral ventricles

• Diencephalon: thalamus/hypothalamus/ retina; third ventricle

• Mesencephalon: midbrain; cerebral aqueduct

• Metencephalon: pons/cerebellum; part of fourth ventricle

• Myelencephalon: medulla; part of fourth ventricle and central canal

Inductive factors are secreted near neural plate. What do they form and what will that then become?

Alar plate: dorsal horn (s) of spinal cord

Basal plate: ventral horn (m) of spinal cord

Describe the sensory/motor structure in the pons and why?

Sensory lateral, motor medial due to flattening of fourth ventricle

Excitatory neurons derive from - - in - -, undergo - -, and migrate -

Inhibitory neurons derive from - - in - - -, and migrate -

radial glia in ventricular zone, asymmetric division, radially

radial glia in medial ganglionic eminence, tangentially

Neocortex is - layers and forms - -

6, inside out

Should have all neurons by roughly week -

20

What is polarization and how does it occur?

Formation of axon and dendrites, axon extends a growth cone

Synaptogenesis starts around week -, wraps up in late -. What comes next?

27, childhood. Synaptic Pruning

Describe the key differences between ASD and DS!

ASD: mPFC volume increase and more density of dendritic spines, decreased pruning, polygenic, aerobic activity helps

DS: trisomy 21, correlated with Alzheimers, increases in inhibitory neurons (GABA)

What are glia and some of their characteristics?

Most common cell type in the brain and support neurons, they are inexcitable, can divide, and lack axons

What are 4 main glial cells and what do they do?

Astrocytes: BBB support, neuromuscular coupling, synaptic transmission

Oligodendrocytes: myelin sheath (CNS), one for many

Schwann Cells: myelin sheath (PNS), many for one

Microglia: immune function for CNS

How is signal propagation impacted by demyelination?

Decreased length and velocity of signal

BBB and BNB both have - -.

• Peripheral nerves have what layers of protection?

• Which contains the BNB?

Tight junctions

• Epineurium (surrounds nerve), Perineurium (surrounds fascicle), Endoneurium (surrounds nerve fiber)

• Endoneurium

Which division of the nervous system’s myelin is conducive for regeneration?

Peripheral Nervous System

Describe Guillain Barre Syndrome

PNS disorder where T cells attack myelin. Ascending weakness, hypo/areflexia, pain/tingling. Preceded by respiratory/GI infection. Good prognosis due to Schwann cell regenerative capacity

Describe Multiple Sclerosis

CNS disorder where T cells attack myelin (leaves astrocyte scars). Relapsing-remitting pattern of neurological deficits (movement, vision), hyperreflexia.

Along with neurons, myelin can exhibit -

Plasticity

What are the equilibrium potentials for the three main ions for neuron AP?

Na+ (60), K+ (-90), Cl- (-70)

List the AP sequence!

RMP→stimulus→Depolarization→Repolarization→Hyperpolarization→RMP

What two types of signals summate to decide the direction of polarization?

EPSP and IPSPs

List synaptic transmission sequence!

AP propagates, opens vg Ca2+ channels, signal release of NT, binds on post-synaptic neuron

What are the differences between ionotropic and metabotropic receptors?

I: opens channel directly, faster effect

M: binds to receptor then activates g protein which signals second messenger to activate kinase for protein phosphorylation, longer lasting effect

The neuromuscular junction is - (-) and requires - for activation

ionotropic (nAch), Acetylcholine

Describe Myasthenia Gravis

Antibodies attack nicotinic Ach receptors at NMJ, progressive muscle weakness throughout the day

Describe Lambert-Eaton Syndrome

Antibodies attack presynaptic voltage gated Ca2+ channels, muscle weakness improves throughout the day

What are the differences between Glutamate and GABA?

Glutamate: excitatory NT, mainly projection/pyramidal neurons (80%)

GABA: inhibitory NT, mainly interneurons (20%)

What are the two types of ionotropic receptors for glutamate?

AMPA (general function), NMDA (plasticity)

• AMPA has Na+ in

• NMDA has Mg2+ blockage removed, Na+ and Ca2+ in (Ca inserts more AMPA)

How do strokes/schizophrenia relate to glutamate?

Strokes: glutamate release + slowed uptake, NMDA receptor overactivation leads to cell death (ca2+ influx)

Schizophrenia: NMDA antagonists mimic symptoms

What is the metabotropic glutamate receptor and what makes it unique?

MGluR, excitatory or inhibitory effect

What are the two receptors for GABA?

GABAa (ionotropic, Cl- in) and GABAb (metabotropic, K+ out)

How do seizures and anxiety relate to GABA?

Seizures: insufficient inhibition (low GABA)

Anxiety: reduced GABAa and GABA levels