B&B High Yield Flashcards
In which type of brainscan is bone colored white, blood–white, CSF–black, and brain–gray?
Computed tomography (CT)
In which type of brainscan is CSF colored black, gray matter colored gray, and white matter colored white, and is faithful to physiologic neuroanatomy?
MRI, T1 sequence
In which type of brainscan is CSF colored white, gray matter colored gray, and white matter colored black, and often used for neuropathology?
MRI, T2 sequence
Type of hematoma that is present above dura mater between skull sutures, has an arterial blood supply and thus progresses rapidly, may be characterized by a lucid interval, and may appear as a biconvex lens on imaging?
Epidural hematoma
Type of hematoma that occurs below the dura mater, proceeds slower due to its venous blood supply, is characterized by headache and confusion, and appears as a crescent on imaging?
Subdural hematoma
Transcription factor essential for anterior neuronal structure development?
Otx2
A gradient of what molecule reinforces the development of the anterior-posterior axis?
Wnt gradient (lowest at rostral end)
What is the function of FGF in the anterior telencephalon?
Promotes Pax6 expression, and represses Emx2 expression. Both are TFs
What chemical gradient is responsible for patterning of the telencephalon?
The Pax6/Emx2 counter-gradient produces an anterior/posterior pattern
Which gene is responsible for coding of anterior/posterior segment identity in rhombomeres?
Hox code (no segmental identity when Hox is absent)
What is the mechanism for ventral patterning of the neural tube?
Notocord induces floor plate formation, which produces Sonic Hedge Hog
What is the mechanism for dorsal patterning of the neural tube?
Ectoderm induces roof plate formation, which produces BMPs
How is neuronal identity determined?
Neural cells are multipotent, and receive external stimuli which induce a specific cell fate.
What is the direction for migration of newly generated cortical neurons?
Inside-out (new cells go to outer layer)
What type of protein is essential for neuronal migration in the cortex?
Tubulin (defects can result in lissencephaly and double cortex syndromes)
Which axoplasmic transport system transports organelles, vesicles, and membranes using kinesin as a motor protein?
Anterograde (toward synapse), fast
Which axoplasmic transport system transports cytoskeleton using bulk flow?
Anterograde (toward synapse), slow
Which axoplasmic transport system transports trophic factors, signaling molecules, and endosomes, and uses dynein as a motor protein?
Retrograde (toward cell body), fast
Which glial cell is involved in the inflammatory response in the CNS and serve as macrocytes?
Microglia
Which glial cell often surrounds neuronal cell bodies and acts to metabolically support or modulate their activity?
Astrocytes
Which glial cell insulates many CNS axons using myelin?
Oligodendrocytes
Which glial cell insulates one PNS axon using myelin?
Schwann cells
What disorder is characterized by demyelination of peripheral nerve stemming from a dominant protein mutation?
Charcot-Marie-Tooth, mutation in PMP22 (peripheral myelin protein 22)
What syndrome affects presynaptic Ca channels?
Lambert Eaton myasthenic syndrome
What toxins impair vesicle fusion at the presynaptic terminal?
Botulinum and tetanus toxin
Which side of a dorsal root do large diameter, myelinated sensory fibers enter the spinal cord?
Medial division
Which side of the dorsal root do small diameter, unmyelinated sensory fibers enter the spinal cord?
Lateral division
What type of sensation is carried in the DCMLS pathway?
Proprioception, fine touch, vibration, pressure, 2-point discrimination
Which tract carries fibers from T6 and below? Which tract carries fibers from T5 and above?
Fasciculus gracilis, travels medially. Fasciculus cuneatus, travels laterally
A lesion of the dorsal columns can result in what kind of ataxia? What test is used to distinguish this?
Results in sensory ataxis, which a Romberg test is used. A positive Romberg sign is if the patient sways with eyes closed.
What type of sensation is carried in the spinothalamic tract?
Pain and temperature sensations
After ascending in Lissauer’s tract, where to primary sensory neurons of pain and temperature synapse?
Synapse in substantia gelatinosa with second neurons, which cross the midline at that level at the ventral white commissure.
What is the role of Clark’s nucleus?
Ia and Ib fibers synapse here with secondary neurons that ascend ipsilaterally in the dorsal spinocerebellar tract and traverse the inferior cerebellar peduncle.
What is the role of the cuneocerebellar tract?
Arises from the external cuneate nucleus and carries proprioceptive input from the upper limb to the cerebellum via the ICP
What spinal cord levels do preganglionic sympathetic neurons exit?
T1-L2
What is infantile bladder and what kind of lesion causes it?
Infantile bladder is uncontrolled complete emptying of the bladder. Caused by lesions above the pontine micturition center.
What is spastic bladder and what kind of lesion causes it?
Spastic bladder is frequent emptying of the bladder after incomplete filling. Caused by lesions in the spinal cord above the sacral cord.
What is atonic bladder and what kind of lesion causes it?
Atonic bladder is complete filling of bladder and urine dribbling. Caused by a lesion to the sacral cord.
What kind of sensation are muscle spindles activated by?
Stretching of surrounding muscle fibers causes activation of stretch-activated ion channels.
What is the role of gamma motor neurons?
Innervate muscle spindles and causes contraction in response to a change in muscle length, so that muscle spindles can detect changes
Explain the myotactic stretch reflex.
Involves largest fibers (Ia and alpha MN) and no interneurons. Opposes muscle stretching by activating stretched muscle and inhibiting antagonist muscle.
Explain the GTO reflex.
Involves Ib fibers and interneurons. Inhibits contraction of muscle by activating antagonist muscle and weakening contracted muscle.
Explain the withdrawal reflex.
Causes ipsilateral flexion and contralateral extension using A-delta fibers (sharp pain) and interneurons.
Describe Amyotrophic Lateral Sclerosis (ALS)
Idiopathic progressive loss of motor neurons (motor neuron disease) that results in atrophy of denervated muscles and hypertrophy of muscles with collateral sprouted innervation. Upper motor neuron findings are present. Begins in bulbar muscles, arms, or legs.
Describe Spinal Muscular Atrophy (SMA)
Progressive loss of motor neurons caused by the loss of the SMN1 gene. Different types ranging in severity.
What is a fibrillation?
The spontaneous firing of individual muscle fibers that are likely denervated. Seen on EMG.
What is a fasciculation?
Muscle twitching noticeable grossly, can be a result of an entire motor unit firing (collateral neuron sprouting)
Describe botulinum toxin’s effects.
Cleaveage of SNAP-25 (vesicle fusion) interferes with vesicle fusion and causes weakness of facial and limb muscles
Describe the effect of organophophorous gases?
Irreversibly bind acetylcholine esterase so that ACh continues to overactivate nicotinic receptors. Results in paralysing inactivation of sodium channel
How does pancuronium act as a paralytic?
Competitive inhibition of ACh receptor, preventing muscle activation potential
Describe Lambert-Eaton syndrome
Autoantibodies against P/Q channels in the pre-synaptic cell. Weakness at rest, may improve with exercise (repetitive depolarization)
Describe Myasthenia Gravis
Autoantibodies against ACh receptors or Musk on the post-synaptic cell, which can cause inflammation and destruction of the motor end-plate. Ocular muscle weakness is common
What is the significance of safety factor?
Under normal physiologic conditions, endplate potential generated by ACh vesicle release always generates a voltage well above the -50 mV threshold
What percent of immediate store vesicles are released at the presynaptic membrane each action potential? What is this percent dependent on?
20%. Amount of Ca influx into the cell
What is a compound muscle action potential?
The sum of the voltage of all NMJ action potentials within a particular muscle.
What is the utility of repetitive stimulation in diagnostic testing?
Successively stimulating a muscle should produce identical CMAPs under physiological conditions. Defects in the NMJ will produce differential CMAPs.
How are physostigimine, neostigmine, and pyridostigmine used as treatments?
These transiently inhibit AChE to increase muscle stimulation, useful for impaired post-synaptic function
How does succinylcholine act as a paralytic?
Acts as a depolarizer of the NMJ and keeps AChR open for much longer than normal
What is ionotropic transmission?
Synapse involving a ligand-gated ion channel. Has direct, fast action for generating post-synaptic potentials
What is metabotropic transmission?
Synapse involving a G-protein coupled receptor, a G-protein effector, a 2nd messenger. May modulate APs and act slower and more sustained
Name typical excitatory neurotransmitters.
Glutamate, acetylcholine, serotonin, histamine, catecholamines
Name typical inhibitory neurotransmitters.
Gamma-aminobutyric acid (GABA), glycine
Characterize glutamate as a neurotransmitter
Involved in learning and memory, excitatory function, interacts with iono- and metabotropic receptors
Characterize NMDA receptors
An ionotropic glutamate receptor that requires a glycine co-agonist to open its Ca ion channel. Ca influx is slower and more sustained (long-term changes w/o desensitization)
Characterize AMPA receptors
An ionotropic glutamate receptor that mediates fast synaptic transmission in the CNS
Characterize GABA as a neurotransmitter
Main inhibitory transmitter in the brain, has three GABA receptors
Characterize GABA A receptors
principal mediators of fast synaptic inhibition in the brain, ionotropic receptor
Characterize GABA B receptors
produce slow, long lasting inhibitory currents, metabotropic receptor, can be pre and post-synaptic
Characterize nicotinic ACh receptors
Ionotropic receptor, gates cations such as sodium and potassium
Characterize muscarinic ACh receptors
Metabotropic receptor, pre and post-synaptic modulatory activity
What are examples of inflammatory myopathies?
Dermatomyositis, polymyositis, and inclusion body myositis
What are examples of congential myopathies?
Nemaline, centronuclear, central core, and minicore myopathy
What proteins are implicated in nemaline myopathy?
Thin filaments of muscle contraction: nebulin and actin
Describe Duchenne muscular dystrophy
Early onset, X-linked, progressive proximal muscle weakness with pseudohypertrophy. Advanced disease involves wheelchair use, scoliosis, respiratory insufficiency, cardiomyopathy, and death.
What is Gowers and what does it demonstrate?
Unusual means of standing from a supine position, which demonstrates proximal muscle weakness
What is Trendelenburg sign and what does it demonstrate?
Excessive hip swing, from proximal muscle weakness. Brought out by climbing stairs
How does Becker muscular dystrophy differ from DMD?
Generally a later onset with variable severity and lifespan
Describe the dystrophin gene?
Largest gene locus, deletions are common and may result in frameshifts, which terminate the gene product (DMD). It functions to anchor the sarcolemma protein complex to contractile machinery.
Describe Facioscapulohumeral dystrophy
Weakness in face, scapula, biceps, shows dominant inheritance and is common in young adults. Involves deletion of repeat elements on chromosome 4qter (end of long arm)
