Week 1 Flashcards
Where in the most rostral portions of developing neural tube are the sensory nuclei located relative to the motor nuclei?
less dorsally and more laterally
Name the four structures divided by the internal capsule.
- caudate nucleus anteriorly
- putamen laterally
- globus pallidus laterally
- thalamus most medially
The inferior colliculus is specialized for what special sense?
auditory
What is neuromelanin? Where is it classically found? In whom is it typically lacking?
- a product of catecholamine metabolism
- found in the substantia nigra
- diminished levels in those with Parkingon’s
What are the two types of astrocytes? Where is each most concentrated?
- fibrous (white mater)
- protoplasmic (grey mater)
Schwann cells are derived from what embryonic tissue?
neural crest cells
Microglia are derived from what embryonic tissue?
mesoderm
Which carrier proteins are used for anterograde and retrograde transport within neurons?
- anterograde: kinesin
- retrograde: dynein
GFAP can be used to stain what cell type?
astrocytes
Astrocytes are derived from what embryonic tissue?
radial glial cells
List the functions of astrocytes.
- contribute to BBB
- insulation of synapses
- sequestration of NTs
- pH balance
- electrolyte balance
Oligodendrocytes can myelinate how many cells?
more than one
The blood brain barrier is a combination of what two things?
- astrocytic foot processes
- extremely tight junctions between endothelial cells
Blood vessels run in which layer of the meninges?
arachnoid
What is the function of CSF?
- cushion the brain
- remove waste products
- carry hormones and other signaling molecules
What cell population secretes CSF?
choroid plexus cells
Choroid plexus cells are a specialized form of what other cell population?
ependymal cells
Describe the path of CSF fluid.
- lateral ventricle
- third ventricle
- cerebral aqueduct
- fourth ventricle
- subarachnoid space
- arachnoid granulations
- venous drainage
Describe the architecture of the spinocerebellar pathway from the arm.
- primary neuron located in the DRG
- secondary neuron located in accessory cuneate nucleus of medulla
- projects to the ipsilateral cerebellum
Describe the architecture of the spinocerebellar pathway from the leg.
- primary neuron located in the DRG
- secondary neuron located in Clarke’s column
- projects to the ipsilateral cerebellum
What is the physiologic importance of Clarke’s column?
it is the location of secondary neurons in the spinocerebellar pathway from the leg for unconscious proprioception
What is the physiologic importance of the accessory cuneate nucleus in the medulla?
it is the location of secondary neurons in the spinocerebellar pathway from the arm for unconscious proprioception
The ALS and DC/ML system project to what area in the thalamus?
the ventral posterior lateral nucleus
Which somatosensory pathway decussates at the vertebral level into which it projects?
the ALS
What information is carried by the spinocerebellar pathway? The DC/ML? The ALS?
- spinocerebellar: unconscious proprioception
- DC/ML: discriminative touch, vibration, conscious proprioception
- ALS: pain, temperature
The corticospinal tract is organized with which fibers more laterally?
those from more distal locations (leg)
The spinothalamic tract is organized with which fibers more laterally?
those from more distal locations (leg)
The dorsal columns are organized with which fibers more laterally?
those from more proximal locations (arm)
The periaqueductal gray mater receives input from what brain structure?
the cerebral cortex
What are adjuvant analgesics?
those with indications other than pain management but with analgesic properties in select circumstances (e.g. gabapentin)
What is Lissauer’s tract?
a tract composed of projections from first order neurons in the ALS on their way to synapse in the dorsal horn a few vertebral levels higher
A(delta) and C sensory afferents are part of which somatosensory pathway?
the ALS
What is the gate control theory of pain?
the idea that low threshold, large diameter afferent mechanoreceptor input can modulate the intensity of incoming small-diameter, nociceptive inputs
Within the dorsal root of the spinal nerve, A(beta) fibers are located where in relationship to A(delta) and C fibers?
larger A(beta) fibers are located posteriorly and medially
What is secondary hyperalgesia?
pain sensitization due to central mechanisms, rather than peripheral ones
What is primary hyperalgesia?
pain sensitization due to the release of inflammatory mediators as a consequence of the nociceptive axon reflex
What is the nociceptive axon reflex?
the mechanism for peripheral pain sensitization
What are the three endogenous opioid peptides?
- dynorphin
- enkephalin
- endorphin
Failed low-back-surgery syndrome is an example of what sort of pain?
mixed
The nociceptive axon reflex is mediated by what NT?
glutamate
What are TRPV1 receptor channels? On which fibers are they found?
- found on C fibers
- change their sensitivity to pH in response to changes in temperature
- an example of functional convergence
What is the difference between the cuneate and gracilis fasciculi?
the cuneate carries fibers from the arm while the gracilis carries those from the leg
The ventral posterior lateral nucleus of the thalamus is important for what reason?
it is the location of tertiary sensory neurons in both the ALS and DC/ML system
What is the importance of the substantia gelatinosa?
it is the location of some secondary neurons in the ALS
What are wide dynamic range neurons in the dorsal horn?
- situated in lamina 3-5
- part of the ALS
- receive collaterals from the DC/ML system
- serve as a point of convergence between ALS and DC/ML
Which type of pain is proportional to the intensity of nociceptive stimulus?
nociceptive pain
What is allodynia?
a painful response to a normally non-painful stimulus
What is the nociceptive axon reflex?
a process of peripheral nociceptive sensitization in which C and A(delta) fibers have efferent effects that evoke an inflammatory response
Name four things capable of stimulating the periaqueductal gray mater?
- stress
- placebo
- comfort
- exercise
What name is given to upper motor neuron projections in the forebrain, midbrain, pons, medulla, and spinal cord?
- posterior limb of internal capsule
- cerebral peduncle
- corticospinal fibers
- pyramids
- lateral corticospinal tract
Describe the architecture of the DC/ML pathway..
- primary neuron in the DRG
- posterior/medial fibers of spinal root
- cuneate/gracile fasciculi
- cuneate/gracile nuclei of the medulla
- medial lemniscus
- contralateral VPL of thalamus
- posterior limb of internal capsule
- somatosensory cortex
Where are the cuneate and gracile nuclei located?
in the medulla
Describe the architecture of the ALS pathway.
- DRG
- anterior/lateral fibers of spinal root
- Lissauer’s tract
- dorsal horn/substantia gelatinosa
- anterior white commissure
- contralateral spinothalamic tract
- VPL of thalamus
- posterior limb of internal capsule
- somatosensory cortex
Describe the architecture of the corticospinal pathway system.
- primary motor cortex
- posterior limb of internal capsule (forebrain)
- cerebral peduncle (midbrain)
- corticospinal fibers (pons)
- pyramids (medulla)
- contralateral corticospinal tract
- ventral horn
- effector muscle
What are the deep sensations?
- proprioception
- deep muscle pain
- vibration
Stimulus intensity is usually encoded by what characteristic of the neural code?
frequency of action potentials
What is contrast enhancement?
the parallel processing of cells with different thresholds refines acuity
What is adaptation?
a decrease in neural response to a maintained stimulus
The best example of “pattern theory” is what sensation?
- color perception
- the pattern of whole neuronal populations forms the basis for perception
Every instance of convergence is also an opportunity for what?
modification and processing
What is surround inhibition?
central signals are facilitated while simultaneously inhibiting eccentric signals in order to sharpen the contrast between them
Two individuals may have a different perception of the same sensory input based on what?
varying experience, knowledge, and previous associations
What is template matching?
a method of percept construction whereby every object, event, or stimulus is compared to some previously stored pattern or template
What is stereognosis?
the mental perception of three-dimensionality
Cutaneous tactile receptors are all innervated by what class of sensory afferent fibers?
A(beta)
Hair follicle endings are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta) fibers
- hair displacement
- thin skin
Ruffini endings are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta) fibers
- pressure on skin in a specific direction (elongated receptive fields)
- dermis of thin skin
Krause corpuscles are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta) fibers
- light touch
- lips, tongue, genitals
Pacinian corpuscles are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta) fibers
- deep pressure and vibration
- deep dermis of thin skin
Meissner corpuscles are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta) fibers
- vibration
- dermis of glabrous skin (fingers/face)
Merkel cells are innervated by ___ fibers, function to sense ___, and are located where?
- A(beta)
- pressure on skin
- epidermis of glabrous skin
The face and fingers are mostly innervated by what cutaneous receptors?
Meissner corpuscles and Merkel cells
Which cutaneous tactile receptor has elongated receptive fields?
Ruffini endings
Free nerve endings detect what sorts of sensory stimulus?
mechanical, thermal, or noxious
Muscle spindles detect what information about muscles?
length and rate of change in length
Muscle spindles have what two types of intrafusal fibers?
bag and chain
What are annulospiral afferents?
primary (Ia) muscle spindle afferents
Ia and II muscle spindle afferents innervate what portions of the muscle spindle?
Ia innervate the equatorial region while II innervate the juxtaequatorial region of chain fibers
Muscle spindles have what two types of efferent innervation?
dynamic and static gamma fibers
Dynamic efferents innervate what part of the muscle spindle? What do static gamma efferents innervate?
- bag fibers
- chain fibers
What information do Golgi Tendon organs detect?
the amount of tension exerted at the myotendinous junction
How do GTO’s receive afferent innervation?
Ib afferents are woven into the collagen fibers of GTOs and are pinched when the collagen fibers are stretched
What is anencephaly?
failure of the neural tube to close rostrally during development
Name the primary neural crest cell derivatives.
- dorsal root ganglia
- ANS ganglia
- chromaffin cells of adrenal medulla
- pia and arachnoid
- Schwann cells
- melanocytes
- thyroid C cells
What are the three layers of the neural tube?
- ventricular (inner)
- intermediate/mantle
- marginal (outer)
Mitosis occurs in what layer of the neural tube?
the ventricular layer
What is interkinetic nuclear migration?
the process of cellular division and differentiation in the neural tube
Neurons are derived from what kind of cells proliferating in the ventricular layer of the neural tube?
neuroepithelial
What is the prosencephalon?
the forebrain
What is the mesencephalon?
the midbrain
What is the rhombencephalon?
the hindbrain
What is the telencephalon? What does it give rise to?
- a division of the prosencephalon
- cerebral cortex, basal ganglia, hippocampus
What is the diencephalon? What does it give rise to?
- a division of the prosencephalon
- thalamus and hypothalamus
The mesencephalon gives rise to what adult brain structures?
the midbrain
What is the metencephalon? What does it give rise to?
- a division of the rhombencephalon
- cerebellum and pons
What is the myelencephalon? What does it give rise to?
- a division of the rhombencephalon
- the medulla
Describe the embryonic vesicles that give rise to the adult brain structures.
- prosencephalon (telencephalon: cerebral cortex, hippocampus, basal ganglia + diencephalon: hypothalamus, thalamus)
- mesencephalon: midbrain
- rhombencephalon (metencephalon: cerebellum, pons + myelencephalon: medulla)
What are the alar and basal plates?
terms for the developing dorsal and ventral regions of the nervous system
What happens to the three layers of the neural tube as neuronal proliferation ends?
- the ventricular layer becomes the ependymal layer
- the mantle (aka intermediate) zone becomes the grey mater
Name the neurotropins that belong to the NGF-family.
- NGF
- BDNF, NT-4/5
- NT-3
The NGF-family of neurotropins bind and share what receptors?
- bind Trk receptors
- share the p75 coreceptor
Name the GDNF-family of neurotropins.
- GDNF
- neurtarin
- Artemin
The GDNF-family of neurotropins bind and share what receptors?
- share the RET receptor
- utilize GFRa coreceptors (1, 2, 3)
NGF supports what cell populations?
- sympathetic
- nociceptive
- cholinergic basal forebrain
GDNF neurotropins support what cell populations?
kidney and enteric NS
BDNF supports what cell populations?
- cortical
- cranial ganglion
- alpha MNs
- vestibular sensory
- peripheral sensory
NT-3 supports what cell populations?
- proprioceptive sensory
- gamma motor neurons
- cranial ganglion
- corticospinal neurons
The action of neurotropins is dependent on what cellular process?
retrograde transport
What is the neurotrophic hypothesis?
target tissues produce limited amounts of neurotrophin so the target area supports only a select number of neurons
Parkinson’s affects what cell population?
dopaminergic neurons in the substantia nigra
Alzheimer’s affects what cell population?
cholinergic neurons in the basal forebrain
