Neuroscience 2 Flashcards
What is the difference between slow and fast axonal transport?
Fast axonal transport is (1) of enzymes AND peptide precursors, and (2) occurs on doublet microtubules. Slow axonal transport typically involves enzymes (or just “other small molecules”) and is perhaps more diffusion-based?
What are ionotropic channels?
Ligand-gated ion channels, ions flow directly in with the ligand opens the channel.
What are metabotropic channels?
Typically GPCRs, a GPCR bound to a ligand sets off a chain of events that results in a neighboring or nearby ion channel opening.
What is the effect of sarin gas at the NT level?
Sarin gas is an AChesterase inhibitor, whose exposure results in tonic clonic seizures and death.
What is the problem causing myasthenia gravis?
It is an autoimmune disorder where one’s own body attacks its ACh receptors, resulting in progressive muscle weakness
To what does a NMDA receptor respond?
Glutamate
What is a siezure?
Abnormal excessive and synchronous electrical discharges of brain neuronal network
What is an aura?
A brief and simple seizure that usually precedes a larger seizure, can also be accompanied by smell, taste or visual aura
Does a simple partial seizure involve LOC?
No, no impaired consciousness or LOC
If a person stares off, what kind of seizure might this be?
A complex partial seizure, involves impaired consciousness or LOC
True or False: Generalized seizures can be convulsive or non-convulsive.
True
The types of seizures are:
- Generalized: A. Convulsive or B. Nonconvulsive
2. Partial (Focal): A. Simple or B. Partial –> both can be secondary generalized
What are the types of epileptic syndromes?
- Idiopathic - presumed genetic etiology
- Secondary/symptomatic - most common - known or suspected disorder of CNS
- Cryptogenic - unknown cause
Define “epilepsy”
Disease of the brain characterized by enduring predisposition to generate epileptic seizures
What is the most common MOI of epileptic channelopathies?
Most common is autosomal dominant, then de novo mutations
What are the most common channelopathies leading to epilepsy?
Na+
What is GEFS+?
Generalized epilepsy with febrile seizure plus
What is SMEI?
Severe myoclonic epilepsy of infancy
SMEI is aka:
Dravet’s Syndrome
SMEI involves what effects on neurons?
Loss of inhibitory fx of GABAergic cortical interneurons –> result in seizures
Loss of inhibitory fx of GABAergic Purkinje cells –> result in ataxia
What is the treatment for SMEI?
Tiagabine –> to decrease reuptake of GABA
Benzodiazepines –> increase in response of post-synaptic GABA receptors
What is the clinical manifestation of SMEI in the 1st year?
Seizures associated with elevated body temp
Progressively prolonged and cluster seizures
Status Epilepticus
What are the clinical manifestations of SMEI in the 2nd year?
Psychomotor delay
Ataxia
Cognitive impairment
What kind of mutation is associated with GEFS+?
Gain of function mutation, found in SCN1B
What is the unifies hypothesis for Nav1.1 genetic epilepsies?
febrile seizures, GEFS+ and SMEI are components of a single spectrum (Na+ channels)
Epilepsies of K+ channels involve __1__ of function mechanism, whereas epilepsies of Ca++ channels involve __2__ of function mechanisms.
- Loss
2. Gain
K+ channels can be found mostly in cells with:
M current
T-type Ca++ channels can be found mostly in __1__ cells and can have spontaneous burst firing properties. Cl- channels maintain the Cl- gradient that is needed for __2__.
- thalamic
2. GABAergic synapse hyperpolarization
What are the two main goals of antiepileptic drugs (AEDs)?
- decrease the hyperexcitability of neurons (Na+ channel blockers)
- increase the inhibitory fx of neurons (GABAergic medication)
What is the next step for a patient that has failed 2 AEDs?
Surgery, if the seizure onset zone can be identified.
What are the modifiable risk factors for stroke?
Smoking Diabetes A-fib Hyperlipidemia Hypertension Carotid Stenosis
What are the major arteries associated with stroke?
- Left MCA
- Right MCA
- Posterior cerebral artery
- Basilar artery
- Lacunar syndrome
What are the subtypes of stroke?
Ischemic stroke - great majority of strokes
Hemmorhagic stroke - only 20%
What are the symptoms of a Left MCA stroke? Name 4 things:
- Aphasia (expressive or receptive)…often mistake for confusion
- Right hemiparesis, face = hand > arm > leg
- Anterior division: left head and eye deviation
- Posterior division: Visual field deficit, aphasia
What are the symptoms of a R MCA stroke?
- Left hemiparesis, face = hand > arm > leg
- Neglect: doesn’t acknowledge left visual space or denies own body parts
- Anterior division: right head and eye deviation
- Posterior division: Visual field deficit, neglect
What are the symptoms of a Posterior Cerebral Artery stroke?
- Visual field deficit or cortical blindness if bilateral
2. May have hemiparesis: complete loss of sensation of the contralateral face, arm, trunk and leg
What are the symptoms of a basilar artery stroke?
- Altered consciousness or coma
- Often bilateral signs
- CN signs and “crossed” signs
- -ex. right facial weakness and left arm/leg weakness
- -ex. loss of pin sensation on left face and right arm/leg
- -oculomotor palsy, nystagmus, palate or tongue weakness
What is the common presentation of a lacunar stroke?
- Pure motor hemiplagia - internal capsule, face = arm = leg
- Pure sensory hypaesthesia - thalamus, face = arm = leg
- Dysarthria clumsy hand syndrome - pons
- Ataxic hemiparesis
What is tPA?
Tissue Plasminogen Activator
Neglect (hemi-inattention) usually indicates:
right hemispheric stroke
True or False: Patients usually look towards the lesion (frontal eye fields).
True
Crossed signs usually indicate:
Brainstem involvement
Vertical nystagmus is _____ until proven otherwise.
brainstem ischemia
What is the inclusion criteria for thrombolytic therapy?
< 80 yo Acute ischemic stroke Onset < 3 hours CT normal, or indicates early infarction NIHSS < 24 Absence of exclusionary criteria Informed consent
What are the major exclusionary factors for tPA?
Hemorrhagic stroke or very large infarction
Abnormal coagulation profile
What are some stroke prevention activities?
- Control of modifiable risk factors
- Antihypertensive and cholesterol-lowering medications
- Antiplatelet meds
- Anticoaguants
- Carotid Endartectomy
What properties distinguish microglia from astrocytes and oligodendrocytes?
Small size and hematopoetic origin
Which of the following is not an example of nerve cell morphology?
Bipolar - Astrocyte - Amacrine - Pyramidal - Purkinje
Astrocytes are a type of glial cell morphology.
True or False: Interneurons are both inhibitory and excitatory?
True
What are Hox genes involved in?
Hox genes are involved in anterior-posterior planning (Shh, Gli and BMPs are involved in DV patterning)
What is the role of Shh during neuronal development?
Shh is highly expressed in floor plate and notochord and thus allow dorsal (motor) fate of neurons.
True or False: In the presence of excess neurotrophins, neurons degenerate.
True. Neurons proliferate in the presence of neurotrophins and degenerate in the absence of neurotrophins. Neurotrophins are produced and secreted by target cells, and p75 receptor has high affinity for all unprocessed neurotrophins.
Which of the following is a characteristic of potassium channels?
Low voltage - high voltage - inactivate quickly
All of the above. Most cells have multiple types of potassium channels.
Patch clamp technique does?
Allows users to record microscopic current through a single membrane channel
What contributes to the hypothesis that neurotransmitter release is quantal at least in the case for ACh in the NMJ?
- The endplate potential (EPP) is produced by the simultaneous release of many individual discrete packets (quanta) of ACh, each producing a mini-EPP.
What contributes to the hypothesis that neurotransmitter release is quantal at least in the case for ACh in the NMJ?
A vesicle’s ACh content corresponds to the amount of ACh that must be applied to mimic a single MEPP.
What contributes to the hypothesis that neurotransmitter release is quantal at least in the case for ACh in the NMJ?
Scanning electron microscopy shows synaptic vesicle fusion with the presynaptic membrane in stimulated frog NMJ preparations. At the frog NMJ, evidence for quantal release was obtained using morphological and statistical analysis of EPP amplitudes (evoked in low Ca2+ solution). A quanta refers to a single vesicle containing 10,000 molecules of ACh, which produces a MEPP. MEPPs have a fixed size and occur in integer multiples of the mean amplitude of EPPs. The summation of many MEPPs is responsible for EPP.
What contributes to the hypothesis that neurotransmitter release is quantal at least in the case for ACh in the NMJ?
The fixed size of MEPPs is consistent with quantal release. For example, release of 1,2,3,4 quanta corresponds to increasingly larger MEPPs.
What describes the time constant of a neuron?
The time and space constants represent passive properties of a neuron. The electrical equivalent circuit utilizes the concept that a membrane has both capacitive and resistive properties in parallel
What is dopamine?
Dopamine is a catecholamine, a small molecule neurotransmitter. Its precursor is Tyr.
How is GABA formed?
Decarboxylation of glutamate
Generalized epilepsy with febrile seizures involves what channels?
Na channels
True or False: NMDA receptors display similar kinetics to AMPA receptors.
FALSE. AMPA receptors display rapid kinetics relative to NMDA receptors, and they differ in not being permeable to calcium ions.
How is GABA inhibitory?
GABA acts on a chloride channel, which, when activated, permits this ion to enter the cell, making it more negative (hyperpolarizing it).
What is this: a graded, fast potential lasting from several milliseconds to seconds, resulting from a chemical transmitter binding to a receptor to produce either an EPSP, depending on a single class of channels for sodium and potassium, or an IPSP, depending on a chloride or potassium channel.
An Increased-conductance PSP
What is a decreased-conductance PSP mediated by?
Chemical transmitter or intracellular messenger to produce a graded, slow potential lasting seconds to minutes. This response is related to a closure of sodium, potassium or chloride channels.
How do receptor potentials form?
From fast, graded potential of a sensory stimulus that involves a single class of channels for both sodium and potassium.
What is the rate-limiting step in the synthesis of serotonin?
tryptophan hydroxylase, one of the enzymes.
What are the functions of dopamine?
- coordination of body movement
- motivation
- reward, reinforcement
- emotional behavior
What are the functions of norepi?
CNS: sleep, wakefulness, attention, feeding behavior
PNS: sympathetic motor system
What are the functions of serotonin?
Regulation of sleep, eating, wakefulness and arousal
What is the most powerful focusing element of the eye?
Cornea
What is involved in visual accomodation?
The contraction of the ciliary muscles reduce the tension of the zonule fibers, allowing the natural lens elasticity to thicken the lens, increasing its curvature. Increased lens curvature shortens the focal length bringing near objects into focus in the back of the eye.
What is visual accommodation?
The change in optical power of the eye allowing the point of focus of the eye to be changed from distant to near objects.
The emmetropic eye is in sharp focus for:
distant objects
What is myopia?
Nearsightedness, cornea is too curved or eyeball is too long. Myopic eyes are unable to attain a sharply focused image unless optical compensation is provided as through negative powered spectacle lenses.
Where is light focused in myopia?
In front of the retina
Where is light focused in hypermetropia?
Light focused behind the retina
What disorders prevent light entering the eye from focusing on the retina?
Refractive disorders: myopia, hypermetropia
What is hypermetropia?
Farsightedness, cornel surface not curved enough or too short