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
Positive lenses move the focal point:
forward, towards the lens (convex)
Negative lenses move the focal point:
backwards (away from the lens, concave)
What is presbyopia?
Loss of lens elasticity causes farsightedness
Disruption of the order of the organization of the lens cell fibers or aggregation of the proteins within them can destroy transparency of the cell is:
cataract formation
What are the symptoms of cataracts?
hazy vision, poor night vision, glare and faded colors
What are the risk factors for cataracts?
Aging, diabetes, sunlight and smoking
What is the leading cause of blindness worldwide?
Cataracts
What is glaucoma?
Group os diseases that damage the eye’s optic nerve and can result in vision loss.
What are the risk factors for glaucoma?
Hypertension, abnormal optic nerve anatomy, elevated intraocular pressure (IOP) (from poor drainage of aqueous humor), thin cornea
What are the symptoms of glaucoma?
Loss of peripheral visual fields, permanent
True or False: The retina is part of the CNS.
True, the retina is a thin neural tissue that lines the back of the eye.
How many cellular layers does the retina have?
Three nuclear layers, 2 plexiform layers (synaptic) and 1 fiber layer
What kinds of neurons are found in the retina?
Photoreceptors Horizontal cells Bipolar cells Amacrine cells Ganglion cells
What kinds of glia are found in the retina?
Muller glia (radial)
Microglia
Astrocytes
What is the vertical information flow in the retina?
Photoreceptors –> bipolar cells –> ganglion cells (cells on the vertical path release glutamate)
What is horizontal information flow in the retina?
Horizontal cells and amacrine cells (cells on horizontal path release mostly GABA or glycine
What are the two types of Photoreceptors in the mammalian retina?
Rod and cone cells
Phototransduction is the conversion of light into __1__ and starts in the __2__.
- bioelectric signal
2. outer segment part of rod/cone cells
What is the neurotransmitter released by rod and cone cells?
Glutamate
In darkness, rods and cones are:
depolarized, near -40 mV, glutamate is released continuously
When stimulated by light, what happens to photoreceptors?
Respond with graded hyperpolarizations (not APs). The hyperpolarizations then spreads passively to the synapse where it reduces the release of the NT glutamate.
Phototransduction begins when:
a pigment molecule absorbs a photon. Active rhodopsin initiates a series of biochemical reactions (the phototransduction cascade) that lead to a reduction in cGMP levels.
What is 11-cis-retinal?
a light-absorbing chromophore
What is rhodopsin?
a visual pigment protein
Restoration of retinal occurs largely in the retinal pigment epithelium in a process known as:
the visual cycle
In photoisomerization, 11-cis-retinal is converted into:
all-trans retinal
The ____ is essential for maintaining the light sensitivity in rod photoreceptors.
pigment epithelium
What is the fovea?
Small depression at the center of the macula, has the highest spatial acuity in the eye. Populated by cone cells (while rods populate periphery)
What is the proportion of rod cells to bipolar cells?
Many rod cells converge on 1 bipolar cell, high sensitivity but low resolution
What is the proportion of cone cells to bipolar cells?
1:1, low sensitivity, high resolution
Rod cells provide vision in __1__ light, while cone cells provide vision in __2__ light.
- dim
2. bright
Rod-only vision is:
scotopic
Cone-only vision is:
Photopic (color)
Rod and cone vision together is:
Mesotopic
Do spinal nerves enter and exit the cranial cavity?
No, they all attach to the spinal cord
Can cranial nerves have more than one nucleus?
Yes
CN I is
olfactory nerve, SVA
CN II is
optic nerve, SSA
CN III is
oculomotor nerve, GSE + GVE
CN IV is
trochlear nerve, GSE
CN V is
trigeminal nerve, GSA + SVE
CN VI is
abducens nerve, GSE
CN VII is
Facial nerve, GSA + GVA + SVA + SVE + GVE
CN VIII is
vestibulocochlear nerve, SSA
CN IX is
glossopharyngeal nerve, GSA + GVA + SVA + SVE + GVE
CN X is
vagus nerve, GSA + GVA + SVA + SVE + GVE
CN XI is
accessory nerve, SVE
CN XII is
hypoglossal nerve, GSE
What is the difference between general and special nerves?
General nerve - impulse can be carried by spinal or cranial nerve
Special nerve - impulse can ONLY be carried by a cranial nerve
Some Say Marry Money But My Brother Says Big Brains Matter More
I - sensory II - sensory III - motor IV - motor V - both VI - motor VII - both VIII - sensory IX - both X - both XI - motor XII - motor
What are the motor cranial nerves?
3, 4, 6, 11, 12
What cranial nerves will have multiple nuclei, and more complicated pathways?
5, 7, 9, 10
What is the sensory part of trigeminal?
Sensory from face, sinuses, teeth
What is the motor part of trigeminal?
Motor to muscles of mastication
What is the parasympathetic portion of the facial nerve?
“secretomotor” - submandibular, sublingual and lacrimal glands
What is the sensory portion of the facial nerve?
Taste for anterior 2/3 of tongue and soft palate
The superior cervical ganglion contains:
all the synapses for the major sympathetic fibers going to the head
Postsynaptic sympathetic fibers will then wrap around blood vessels, ie ____ to get into the cranial cavity.
internal carotid artery
What are the four preganglionic PS fibers in the cranium?
3, 7, 9, 10
The four PS ganglia in the head are associated with branches of:
trigeminal
The temporal retina detects:
nasal visual fields
The nasal retina detects:
temporal visual fields
What is the monoclear temporal crescent?
the edge of the left or right visual hemifield that is not covered by the other eye, makes a crescent moon shape
What visual field test is good for diagnosing macular degeneration?
Amsler grid
An arcuate defect can be indicative of what conditions?
Retinal or optic nerve problem
What is an altitudinal visual field split?
Horizontal
What is a hemianopia visual field split?
Vertical
What is a congruous visual field defect?
Same defect in both eyes
Pathologic processes including the retina may produce:
general or focal VF defects
An altitudinal defect makes you think of what diagnosis?
Ischemic optic neuropathy
Loss of an entire VF of one eye makes you think of what diagnosis?
optic neuritis
What is Willebrand’s knee?
Nasal retinal fibers wrap through the chiasm, go up the opposite optic nerve for about 4 mm and then turn around
“Pie in the sky” visual defect is associated with what diagnosis?
Junctional syndrome, issue at Willebrand’s knee
The location of a lesion producing bitemporal hemianopia is:
Center of the optic chiasm
Bitemporal hemianopia makes you think of what diagnosis?
Pituitary adenoma, need MRI
The further up the optic tract the lesion, the more ____ the VF defects.
incongruous
A pituitary adenoma may produce bitemporal hemianopia or:
inferior chiasmal syndrome, a superior bitemporal quadrianopsia (pressure on chiasm from below)
What is one diagnosis never seen in practice?
Sectoranopia associated with a lateral geniculate lesion
Lesions in the optic radiation are associated with what condition?
Controlateral Homonymous quadrantanopia, ie in Meyer’s loop, can be congruous or incongruous depending on where the lesion is.
Field defects associated with parietal optic radiations are more _____ than those associated with temporal lobe optic radiations.
congruous
High congruity of the VF defect of homonymous hemianopia/quadrantanopia is associated with what location?
Lesions of the Calcarine cortex
Macular sparing is common but not exclusive of:
occipital lobe lesions
Monoclear temporal crescent spared also common in occipital lobe lesions
Retrochiasmal VF defects are almost always:
homonymous
Slits and UNC 5 netrins are what kind of axon guidance signals?
diffusible repellant
Differential innervation of ganglionic neurons must occur at the level of:
synapse formation
Adhesive factors in the developing CNS include:
protocadherins
cadherins
Inductive factors in the developing CNS include:
SynCAM
Ephrin B
Neurexin
Neuroligin
Neurexin is where in the synapse?
Presynaptic
Neurogilin is where in the synapse?
Postsynaptic
Protocadherins form what in neurons?
A kind of thumb print based on what kind of protocadherin expression is occurring
In synaptogenesis (birth to…), target cells release:
trophic factors
What is NGF?
Nerve growth factor, a member of the neurotrophin family
What occurs in the absence of NGF?
Neuronal death
Increased NGF gas what effect?
Survival of excess neurons
Trk ad p75, neurotrophin receptors, activate:
intracellular signaling cascades
Trk has affinity for:
specific, cleaved neurotrophins
Trk has what outcomes?
Cell survival, neurite outgrowth, nerve differentiaion, plasticity
p75 has what affinities?
All uncleaved neurotrophins
p75 has what outcomes?
cell death, cell survival, neurite growth
The uncinate fasciculus tract is where in the brain?
Frontal to temporal (connects reward and punishment centers?)
Frontal to temporal and occipital tracts is defined by what fasciculus?
Superior longitudinal fasciculus, connects Broca’s to Wernicke’s and auditory
The Superior longitudinal fasciculus is also known as:
the arcuate
What is the cingulum?
White matter tract directly above corpus collosum, connects part of limbic system
What makes up the limbic system?
- Cingulate gyrus
- Parahippocampal gyrus
- Uncus
- Subcallosal gyrus
The fasciculus connecting occipital to temporal lobes is:
the inferior longitudinal fasciculus
A major target output of V1 is:
V2, the next cortical processing stage
What do CO stains look like in V1 and V2?
V1 - CO stains are blobs
V2 - CO stains are stripes
Area MT is heavily dominated by:
motion processing cells
Lesions in MT lead to:
profound deficits in motion perception
Where is the MT area found?
V5, MT = medial temporal area
_____ contains oriented cells that seem concerned with motion and depth visual processing.
Thick strip of V2
The thick strip of V2 is also the M (magno) dominated V2 pathway into the parietal cortex known as the:
WHERE pathway
V2 embodies the anatomical and functional compartments for:
- distinct visual pathways
- color
- motion and depth processing
Thin V2 think stripes contain color selective cells and receive input from:
V1 CO blobs.
V2 interstripes contain oriented cells that also seem concerned with:
curvature
The hippocampus is the source of what visual areas?
Highest visual areas
The overall organization of visual pathways seems to be divided into two major streams:
- dorsal/parietal
2. ventral/temporal
Bilateral lesion of the ______ leads to a behavioral deficit in a task that requires the discrimination of objects.
temporal lobe, “WHAT”
Bilateral lesion of the parietal lobe leads to a behavioral deficit in a task that requires the:
discrimination of locations/landmarks, “WHERE”
hemispatial neglect
The WHERE visual pathway starts in V1 and goes to…?
V2–>MT–> parietal lobe (dorsal, spatial vision pathway)
The WHAT visual pathway starts in V1 and goes to…?
V2–>V4 –> temporal lobe (ventral, object recognition pathway)
What and Where pathways also include other brain functions, for example:
auditory
