neuro Flashcards
Neural development
Notochord induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
Neutral plate gives rise to nueral tube and neural crest cells
Notochord becomes nucleus pulposus of intervertebral disc in adults
Alar plate (dorsal): sensory; regulated by TGF B (including BMP)
Basal plate (ventral): motor; regulated by SHH
Regional specification of developing brain
Telencephalon is the 1st part
Diencephalon is the 2nd
The rest are arracnged alphabetically: mesencephalon, metenncephalon, myelencephalon (Ms are in alphabetical order)
Midbrain and cerebral aqueduct- mesen cephalon
Meten myelencephalon
Central and peripheral nervous systems origins
Neuroepithelia in neural tube- CNS neurons, ependymal cells (inner lining of ventricles, make CSF) oligodenderocytes, astrocytes
Neural crest- PNS Schwall cells, glia, melanocytes, adrenal medulla
Mesoderm- Microglia (like Macrophagees)
Neural tube defects
increased aFP
increased achE
spinabifida occulta- lower vertebral levels, dura intact, with tuft of hair
Meningocele- meninges under skin
Myelomeningocele- plus CNS parts
Myeloschisis- no skin, SHIT we see spina cord
Anencephaly- polyhydramnios
holoprosencephaly
embryonic forebrain does not separate into 2 cerebral hemispheres during weeks 5-6
SHH gene is fucked up
other midline defects
Pituitary dysfunction (diabetes insipitus)
Parau syndrome trisomy 13
Lissencephaly
failure of neuronal migration - smooth brain, microcephaly ventriculomegaly
Posterior fossa malformation
Chiari 1 malformation- tonsils go in foramen magnum, usually asymptomatic in , headackes, with spinal cavitations
Chiari 2 malformation- vermis and tonsils –> aqueductal stenosis–> non communicating hydrocephalus
lumbosacaral meningoseel, more severe
Dndy Walker- agenesis of cerebellar virmis–> cystic enlargement 4th ventricle
Syringomyelia
cystic cavity (syrinx) within central canal of sp cord.
The fibers crossing at anterior white commissure (spinothalamic tract) are typically damaged first. Cape like bilateral loss of pain and temp sensation in upper extremities (fine touch preserved
Chiari 1 malformation association, Cervica> Throaci>lumbar
tongue development
1st and 2nd pharyngeal arches form anterior 2/3 (thus sensation via CN V3 taste via CN7)
3rd and 4th pharyngeal arches form posterior 1/3 (thus sensation and taste mainly via CN9 (glosopharyngeal) extreme posterior via CN X
Motor innervation is via CN 12 (hypoglossal) to hypoglossal retracts and depresses tongue), genioglossus (protrudes tongue), and styloglossus (draus sides of tongue upward to create a trough for swallowing
Motor innervation is via CNX to palatoglossus elevates posterior tongue during swallowing)
The Genie comes oudt of the lamp in style
Nissl stain and neurons
Nissl stains RER in cell bodies and dendrites
RER not present in axon
Neuron markers- neurofilament protein, synaptophysin
Astrocytes
Most common glial cell type in CNS
Physical support, repair, extracellular K buffer, removal of excess NTs, component of BBB, Glycogen fuel reserve buffer, Reactive gliosis in response to neural injury
Neuroectroderm
GFAP
Microglia
Phagocytic scavenger cells of CNS (mesodermal, monocyte)
Activation in response to tissue damage–> release of inflammatory mediators (NO, glutamate) Not readily discernible by Nissl stain
HIV infection microglia fuse to form multinucleated giant cells in CNS seen in HIV Associsates dementia
ependymal cells
ciliated simple columnar glial cells line ventricles
cilia beat CSF
microvilli CSF absorption, specialized ependymal cells (choroid plexus) produce CSF
Myelin
increased conduction velocity of signals transmitted–> saltatory conduction of AP at the nodes of Ranvier, where there are high concentration of Na channel
in CNS (including CN2) myelein is synthesized by Oligodendrocytes- in PNS myelin is synthesized by Schwann cells
Wraps and insulates axons, oligodendrocytes myelinate multiple parts of the axon
Schwann cells
Promote axonal regeneration, derived from neural crest
Each shwann cell myelinates only 1 PNS axon, injured in guillein Barre syndrome
Oligodendrocytes
myelinate axons of neurons in CNS each oligodendrocyte can myelinate many axons
Predominant type of glial cell in white matetr
Neuroectoderm , fried egg appearance histologically injured in MS, PMLm leukodystrophy
Sensory receptors
Free nerve endings (A delta plane is fast, but a taxC is Slow)- all skin, epidermis, some viscera, pain and temp
A delta- fast myelinated fibers
C slow- unmyelinated
Meissners corpuscle- large myelinated fibers, adapt quickly, Glabrous (hairless skin)- Dynamic, fine/light touch, position sense, low frequency vibration
Pacinian corpuscles- large, myelinated fibers; adapt quickly, deep skin layers, ligaments, joints, High frequency vibration, pressure (DEEP meissners)
Merkel discs- large myelinated fibers- adapt slowly, finger tips and superficial skin, Pressure, deep static touch (shapes edges, position sense- (Merkel has a K in it with lots of edges and bends)
Ruffini corpuscles- Dendritic endings with capsule, adapt slowly, finger tips joints- pressure, slippage of ocjects along surface of skin, joint angle change
Peripheral nerve
Endoneurium- thin, supportive connective tissue that ensheathes and supports individual myelinated nerve fibers
Perineurium- blood nerve Permeability barrier, surrounds a fascicle of nerve fibers
Epineurium- dense connective tissue that surrounds entire nerve, fascicles and blood vessels
Endo, Peri Epi (outer)
Chromatolysis
Reaction of neuronal cell body to axonal injury. Changes reflect increased protein synthesis in effort to repair the damaged axon, Characterized by:
round cellular swelling, displacement of nucleuys to periphery, dispersion of nissl substance throughout cytoplasm
Wallerian degeneration- disintegration of the axon and myelin sheal distal to site of axonal injury with macrophages removing debris
Proximal to the injury, the axon retracts, and the cell body sprouts new protrusion that grow toward other neurons for potential reinnervation, serves as prep for axonal regeneration and functional recobery
Neurotransmitter sites of synthesis and diseases
Acetylcholine- Basal nucleus of meynert (decreased in alzheimers, huntington, and increased in parkinson)
Dopamine- Ventral tegmentum, SNc- decreased in Depression and parkinsons, increased in schizophrenia and huntington
GABA- Nucleus accumbens- decreased in anxiety and huntington
NE- Locus Ceruleus in pons
Sir Raphe (serotonin - raphe nuclues)
No 4 Loko for me (norepi - locus ceruleus)
Aggumbens, the c’s kinda look like g’s (GABA - accumbens)
Ace the test like a nerd (Ach - basal nucleus of Meynert)
Meninges
Dura- thick outer closest to skull, derived from mesoderm
Arachnoid mater-middle layer contains web like connections, derived from neural crest
Pia mater- thin fibrous inner layer also from neural crest
CSF Flows in the subarachnoid space located between arachnoid and pia mater, epidural space- between dura and skull, middle meningeal artery injueyr
BBB
Prevents circulating blood substances (bacteria, drugs) from reaching the cSF/CNS formed by 3 structures
Tight junctions between nonfenestrated endothelium, basement membrane and astrocyte foot processes
Glucose and AAs cross slowly by carrier-mediated transport mechanisms
Non polar/ lipid soluble substances cross rapidly via diffusion
Area postrema in medulla, OVLT (osmoreceptors in Posterior pituitaray) no BBB, infarct or neoplasm destroys endothelial cell tight junctions –> vasogenic edema Hyper osmolar agent (mannitol)can disrupt of medication permeability
Vomiting center
coordinated by nucleus tractus solitarius in the medulla, which recieves info from the chemoreceptor trigger zone (CTZ, located within area postrema in 4th ventricle, GIT (via vagus nerve ), vestibular system and CNS
CTZ receives 5 major receptors- Muscarinic (M1), dopamine (D2), histamine (H1), Serotonin 5HT3, Neurokinin NK1 receptors
5HT3, D2 and NK1 antagonists used to treat chemotherapy- induced vomiting
H1 and M1 antagonist treat motion sickness; H1 antagonist treat hyperemesis gravidarum
sleep physiology
Sleep cycle is regulated by circadian rhythm, which is driven by suprachiasmatic nucleu of the hypothalamus
Circadian rhythm controls nocturnal release of ACTH, prolactin, melatonin, NE SCN–> NE release–> pineal gland–> increased melatonin
SCN regulated by Light
2 stages- rapid and non rapin REM
Alcohol, benzos, and barbiturates– decreased REM sleep and N 3 sleep ne also decreases REM sleep
Benzos are useful for night terrors and sleepwalking by N3 decrease and decrease REM sleep
Sleep stages
Awake open eyes- Alert, active mental concentration, Beta (highest frequency, lowest amplitude),
Awake, eyes closed- Alpha waves
Non REM sleep -
N1- light sleep- Theta waves
N2- deep sleep when bruxism (twoth grinding occurs, Sleep spindles and K complexes
N3- Deepest non REM sleep, slow wave sleep, sleepwalking, night terrors, bedwetting occur wee and flee in N3. Delta lowest freq, highest amp
Rem Sleep- toss of motor tone, increased brain O2 use, increased AcH, dreaming, nightmares and erection, memory processing function, Paramedian pontine reticular formation/ conjugate gaze center), every 90 minutes and duration increases throught night, Betaelderly decreased, and N3, depression increases
At night BATS Drink Blood
Hypothalamus
Maintains homeostasis by regulating the hormones
Thirst and and water balance, controlling adenohypophysis (anterior pituitary), and neurohypophysis (posterior pituitary) release of hormones produced in the hypothalamus, and regulating Hunger, Autonomic nervous system, Temperature and sexual urges
Inputs (areas not protected by BBB, OVLT (senses changes in osmolarity), area postrema (found in dorsal medulla, respinds to emetics)
Lateral nucleus
Hunger- destruction–> anorexia, FTT stimulated by ghrelin, inhibited by leptin
Lateral injury makes you lean
Ventromedial nucleus
Satiety, Destruction– hyperphagia, Stimulated by leptin
Ventromedial injury makes you very massive
Anterior nucleus
Cooling parasympathetic, AC- Anterior Cooling
Posterior nucleus
Heating sympathetic- Heating controlled by Posterior nucleus - Hot pot
Suprachiasmatic nucelus
Circadian rhythm- SCN is a Sun censing nucleus
Supraoptic and paraventricular nuclei
Synthesize ADH and oxytocin
SAD POX- supraoptid ADH, Paraventricular- oxytocin
ADH and oxytocin are carried by neurophysins down axons to posterior pituitary, where these hormones are stored and released
Pre optic nucelus
thermoregulation, sexual behavior, releases GnRH
Failure of GnRH -producing neurons to migrate from olfactory Pit- Kallmann syndrome
Thalamus
major relay for all ascending sensory information except olfaction
VPL (Ventral Postero-Lateral nucelus)
from spinothalamic and dorsal columns/medial leminsuc
Vibration, Pain, pressure, Proprioception, Light touch, temperature
goes to 1’ somatosensory cortex
Ventral posterMedial nucleus
Trigeminal and gustatory pathway, Face sensation, tast
1’ somatosensory cortex, Makeup goes on the face
Lateral geniculate nucleus
CN 2, optic chiasm, optic tract- to 1’ visual cortex (calcarine sulcus)
Vision
Lateral for light
Medial geniculate nucleus
Superior Olive and inferior colliculus of testum
Hearing
Auditory cortex of temporal lobe
Medial– music
Ventral lateral nucleus
Cerebellum, basal ganglia
Motor
Motor cortex
Limbic system
Collection of neural structure involved in emotion, long term memory, olfaction, behavior modulation, ANS function
Hippocampus, amygdala, mammry anterior thalalamuc
Thalamic nuclei, cingulate gyrus, entorihnal cortex
Feeding Fleeing Fighting, Feeling Fucking
Dopaminergic path
drugs (anipsychotics) and movement disorders, parkinson)
Mesocortical negative symptoms, antipsychotics have limited effect
Mesolimbic positive symptoms
Nigrostriatal- extrapyramidal symptoms, dopainergeic
Tuberoinfundibular- prolactin libido
Cerebellum
movement, coordination and balance
Input from contralateral cortex via middle cerebellar peduncle, ipsilateral proprioceptive information via inferior cerebellar peduncle from spinal cord
Output- the only output of cerebellar cortex is the purkinje cells, always inhibitory–> deep nuclei of cerebellum–> contralateral cortex via superior cerebellar peduncle
Deep nuclei (lateral -> medial) Dentate, Emboliform Globose, Fastigial
Lateral lesions- affect voluntary movements of extremities, fall toward injured side
Medial lesions- tuncal ataxia, wide gate, nystagmus, head tilting, bilateral issues proximal structures
basal ganglia
important in voluntary movements and adjusting posture
Receives cortical input, provides negative feedback to cortex to modulate movement
Striatum= putamen + Caudate (cognitive) Lentiform= putamen + globus pallidus
Direct (excitatory) pathway- SNc input to the striatum via the nigostriatal dopaminergic pathway releases GABA, which inhibits GABA release from the GPi, disinhibiting the Thalamus via GPi (increased motion) D1 Receptor (DIRECT)
The Indirect (inhibitory) pathway- SNc input to the striatum via the nigrostriatal dopaminergic pathway releases GABA that disinhibits STN via GPe inhibition, and STN Stimulates GPi to inhibit the thalamus (decreases motion)
Dopamine binds D1, stimulating the excitatory pathway, and to D2 inhibiting pathway–> increased motion
Cerebral perfusion
Relies on tight auto-regulation
Primarily driven by PcO2
Therapuetic hyperventilation–> decreased PcO2–> vasoconstriction–> decreased cerebral blood flow decreases ICP
increased CO2 –> vasodilation
decreased blood pressure or increased ICP–> decreased cerebral perfusion pressure
Watershed zones
Cortical border zones occur between anterior and middle cerebral and posterio and middle cerebral arteries
internal border zones between the superficial and deep vascular territories of the middle cerebral artery
proximal and lower extremity weakness
higher order vision if PCA.MCA
Dural venous sinuses
large venous channels that run through the periosteal and meningeal layers of the dura mater, drain blood from cerebral veins and receive CSF from arachnoid granulations, empty into internal jugular vein
Venous sinus thromboembolism
increased ICP – can lead to venous hemorrhage, associated with hypercoagulable states (pregnancyOCP use, factor V leidin)
Path of ventricular CSF to venous system
Foramen of Megendie and Foramina Luschka go to subarachnoud space, where its reabsorbed by arachnoid granulationsin venous sinus to internal jugular vein
CNs and where they come from
4CN are above pons (1 2 3 4)
4 CN ext at the pons (5 6 7 8 )
4 are in medulla (9 10 11 12)
4 nuclei are medial (3 4 6 12
CN 5 exits via Standing Room Only (superior orbital fissure, Rotdundum, Ovale
Vagal nuclei
Nucleus Tractus Solitarius (Visceral Sensory information (taste baroreceptors, gut distention (7 9 10)
Nucleus aMbiguous- Motor innervation of pharynx, larynx, upper esophagus, swallowing palate elevation 9 10 11
Dorsal motor nucleus- Sends autonomics (parasympathetic fibers heart lungs upper GI) 10
Cranial nerve reflexes
Corneal reflex- V1 opthalmic (nasociliary branch)–> Bilateral 7 of temporal branch)
Lacrimation- V1 –> 7
Jaw jerk V3 –> V3
Pupillary- 2 –> 3
Gag 9-> 10
Cough 10-> 10
Mastication muscles
3 muscles close the jaw- Masseter, teMporalis, Mediall pterygoid
1 opens- Lateral pterygoid
Lateral lowers
all are innervated by V3
Spinal nerves
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
Nerves C1-C7 exit above the vertebrae
C8 belowC7 and above T1
All aother below
Spinal cord- lower extent
in adults, spinal cord ends at lower border of L1-L2 vertebrae
Subarachnoid Space extends to lower S2
Lumbar punbtuire L3-L4 L4-L5
Needle passes thru skin, fascia and fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, duramater, arachnoid, Subarachnoid
Spinal cord and associated tracts
Legs (lumbosacral) are lateral in lateral corticospinal, spinothalamic tracts, thoracic spinal cord has intermediate column
Dorsal columns are organized with hands at sides and legs inside
Ascending dorsal columns- fasiculus gracilis and cuneteus (lower and upper body with pressure, vibration, fine touch, proprioception)
Ascending lateral spinothalamic tract (pain and temperature, Sacral on out, cervical medial). Anterior spinothalamic tract (crude touch, pressure)
DESCENDING
Anterior corticospinal tract- voluntary motor
Lateral corticospinal tract (voluntary motor sacral on out cervical in middle)
Ascending Dorsal column
Pressure vibration, fine touch, proprioception
1st order neurons: sensory nerve ending–> bypasses pseudounipolar cell body in dorsal root ganglia–> enters spinal cord–> ascends ipsilateral in dorsal columns
Synapse 1: Nucleus gracilis and cuneatus in the ipsilateral medulla
2nd order neuron: Decussates in medulla–> Ascends contralaterally as the medial lemniscus
VPL and the thalamus–> sensory cortex
Spinothalamic tract
Function: Lateral pain and temperature
Anterior: Crude touch, pressure
1st order neuron: sensory nerve ending (A delta and C fibers–> bypasses pseudounipolar cell body in dorsal root ganglion –> enters spinal cord
1st synapse: ipsilateral gray matter (spinal cord)
2nd order neuron: decussates in spinal cord as the anterior white commisure –> ascends contralaterally
ends at VPL and sensory Cortex
Lateral corticospinal tract
Descending tract
Volunary movement of contralateral limbs
Upper motor nuerun: cell body in 1’ motor cortex–> descends ipsilaterally through posterior limb of interal capsule and cerebral peduncle, most fibers decussate at caudal medulla (pyrimidal decussation)–> descends contralaterally
Cell body of anterior horn (spinal cord)
LMN leaves spinal
NMJ mesucle fibers
Primitive reflects
CNS reflex that are present in infants but disappear in 1st year
Moro reflex- hang on for life reflex- abduct/ extend arms when startled, and then draw together
Rooting reflex- movement of head toward side of cheek or mouth, nipple seeking
Sucking reflex
Palmar reflex- curling of fingers
Plantar reflex- dorsiflextion of large toe and fanning with plantar stimulation, Babinski is when its present in adulthood
Galant reflex- spine
