Lecture 220-229

Comple at 27th day
Goes cranial to caudal

1. Meningocele: only CSF protrudes through the defect
2. Meningomyelocele: spinal cord and meninges are included in the cystic sac that protrudes. MOST COMMON TYPE OF SPINA BIFIDA.

Arnold-Chiari malformation characterized by compressed and elongated cerebellum and medulla that have been pulled into the foramen magnum.

It is caused by defectvie secondary neurulation and is also known as "tethered cord syndrome."

Myeloschisis is Rachischisis
-Wost type of spina bifida
-Never from neural tube, no protective fluid filleed sac, no sensory or motor control of lumbar or sacral regions, spine is open to the air

-Encephalocele (brain hernia). Meninges protrude with or without brain

--Anencephaly (without brain): brain does not develop --> most common cause of miscarriages

Rhombencephalon becomes
-Metencephalon: cerebellum and pons
-Myelencephalon: medulla

The CEPHALIC flexure is important because it is tthe only one that remains n the adult. Responsible for the vertical orientation of the brainstem and the spinal cord.

Lateral ventricles: telencephalon
3rd ventricle: diencephalon
aquduct: mesencephalon
4th: hindbrain

(whole brain)
Issues with midline structures: cyclops babies

When it is partially or entirely missing

1. Neuroepithelium
2. Mantle layer
3. Marginal layer

1. Neuroepithelium: neuroblasts
2. Mantle layer: Alar plate: sensory, Basal plate: motor
3. Marginal layer: white matter tracts

Except microglia that come from mesoderm

The sulcus limitans

4th month of life

Because 4th ventricle pushed the sensory alar plates down and laterally

black

An issue with neuronal PROLIFERATION
-microcephaly or macrocephaly

neuronal migration

All synanpses occur in GRAY matter

8C
12T
5L
1Co

Spinal segments are located above their corresponding vertebra and are named based on where their roots come out of

anterolateral pathways that carry the information for pain and temperature

Fibers that are IA are going to have the LOWEST thresholds, meaning that they are the MOST sensitive and will conduct the information the fastest.

Lamina of Rexed are the divisions of the lamina of the gray matter found in the spinal cord. They are numbered I-X.

Pain fibers: I, II (V for gate modulation)
Sensory: III, IV, V

Lamina I: marginal zone
Lamina II: substantia gelatinosa.

Medially:
-interneurons that coordinate reflexes
-Clarke's nucleus dorsalis that relays proprioception to the cerebellum in the dorsal spinocerebellar tract

Lateral division containts
-intermediolateral cell column: preganglionic sympathetic cells
-sacral parasympathetic nucleus: parasympathetic cells

Lamina IX is MOTOR.
-Medial: trunk
-Lateral: limb

Within the lateral motor pools of lamina IX:
-Medial is more proximal: (shoulder will be more medial and hand will be more lateral)
-vENtral: extENsor, dorsal: flexor

1. somatic
2. visceral motor
3. sympathetic
4. Parasympathetic

FASICULUS PROPRIUS = PROPRIOSPINAL TRACT
-Surrounds gray matter
-Short ascending and descending fibers from propriospinal neruons that connect different spinal segments
-involved in intersegmental spinal reflexes that involve many groups, eg. withdrawal reflex

Adelta and C root fibers carrying pain and temperature

1. Spino-olvariy
2. Spinocervical
3. Spinocerebellar (dorsal)
4. Spinocerebellar (ventral)
5. Anterolateral system (pain and temp)

1. Lateral corticospinal
2. Rubrospinal
3. Raphespinal and hypothalamospinal
4. Medullary reticulospinal

1. tectospinal
2. ventral corticospinal
3. lateral vestibulospinal
4. medial vestibulospinal
5. pontine reticulospinal
6. interstitiospinal

Above T6.
C1-T5 have ggracilis

The ones found in cervical and lumbosacral enlargements.
C8-L2: Clarke's nucleus dorsalis
T1-L3: large lateral horns

exteroceptors: cutaneous receptors
proprioceptors: muscle and joint
interoceptors: visceral

-DORSAL SPINALCEREBELLAR TRACT carries SENSORY information from the LOWER BODY.

Best friend:
CUNEOCEREBELLAR TRACT that carries sensory information from UPPER BODY.

VENTRAL SPINOCEREBELLAR TRACT carries MOTOR information from LOWER LIMB.
Bestt friend:
ROSTRAL SPINOCEREBELLAR tract that carries MOTOR information from the upper limb.

Ventral spinocerebellar tract.

1. LATERAL CORTICOSPINAL TRACT
2. RUBROSPINAL TRACT

Synapse in lateral intermediate zone and venttral horn to innervate distal LIMB muscles that control FINE SKILLED MOVEMENTS

1. Hypothalamic tract
2. Solitariospinal tract

The Raphespinal tract is a descending motor tract that is involved in inhibiting pain.

Root compression!
The signs are absent or decreased deep tendon reflexes and paresthesia

Common injury is caused by L5/S1 prolapse

Complete transection of the spinal cord caused by transverse myelitis or trauma

BELOW level of the lesion!!!

-Ipsilateral loss of touch
-Ipsilateral UMN signs at and below lesionlevel
-Contralateral loss of temperature, 1 or 2 levels below injury

Symptoms: bilateral band of analgesia and thermanesthesia
-Caused by ttrauma

A. Extensor plantar response (Babinski sign) on the right side.

Know this bc it is a spinal cord injury it must be IPSILATERAL.

Babinski sing is result of damage to corticospinal tract.

LMN injuries are the result of ROOT compressions.

motor learning

pain and temperature to the face

-Crossed lateral corticospinal tract
-Uncrossed ventral corticospinal tract

Olivocerebellar fibers. The fibers are involved in motor learning: how you lear to ride a bike.
-olivocerebellar fibers decussate through the opposite inferior cerebellar peduncle and synapse as climbing fibers inthe cerebellar cortex

1. Spinal tract of the trigeminal nerve with pain and temp info from the face (which descends, synapses at the spinal nucleus, 2nd axon forms trigeminothalamic tract, synapses at VPM and sends info to postcentral gyrus)
2. Nucleus of the Spinal tract

1. Medial magnocellular reticular area: modulates pain
2. Lateral parvocellular reticular area: for simple reflexes (eye movements, eating)

Relay station between the cerebral cortex and opposite cerebellar cortex

Longitudinal:
1. Corticospinal
2. Corticobulbar
3. Corticopontine

Transverse fiber: Pontocerebellar fibers

They synapse BILATERALLY on lower motor neurons in the motor nuclei of cranial nerves.

Coricopontine fibers are THE ONLY ONES that terminate in the pons. Synapse at pontine nuclei, where PONTOCEREBELLAR fibers decussate to contralateral side and enter the cerebellum through the middle cerebellar peduncle

1. Tectum (roof) -> only the midbrain has a tectum
2. Tegmentum (floor)
3. Substantia nigra
4. Crus cerebri

1. Superior colliculus, superior brachium
2. Inferior colliculus, inferior brachium
3. Periaqueductal gray

Reflex center for SSSaccadic eye movements

-visual refelexes: pupillary light
-accommodation
-saccadic and smooth pursuit eye movements

PPPPeriaqueductal gray - PPPPain control

1. Mesencephalic nucleus of the trigeminal nerve: cell bodies of 1st order pseudounipolar neurons carrying proprioceptive information about muscles of mastication
2. Rubrospinal tract: originates from red nucleus

-corticospinal tract
-corticobulbar tract
-corticopontine tract

all of these will continue down to the pons.

CN I-IV: Midbrain and above
V-VIII: Pons and pontomedullary junction
IX-XII: Medulla

IV

1. Sensory ganglia of cranial nerves (eg trigeminal ganglion)
2. EXCEPTION: Mesencephalic nucleus that has cell bodies which are receiving proprioceptive information about the muscles of mastication

Cell BODIES of 2nd order sensory neurons

Cell bodies of lower montor neurons

Contralateral facial paralysis.

You would get ipsilateral facial paralysis if it was a LMN lesion in the brian stem or cranial nerves

Somatic - SOMITES!!!!
-III, IV, VI, XII
-III, Superior Colliculus
-IV, Inferior Colliculus
-VI, midpons
-XII, medulla

-V
-VII
-IX
-X
-XI

-VII
-IX
-X

Nucleus ambiguus

III: Edinger Westphal nucleus
VII: Superior salivatory nucleus
IX: Inferior salivatory nucleus
X: vagal trigone

RIGHT internal capsule
-LEFT face
-Tongue away from the lesion side, so pointing to LEFT
-Uuvula towards the lesion, so RIGHT
-Ipsilateral weakness of sterno and trap so they will be weak on the right

IPSILATERAL cranial nerve deficits
CONTRALATERAL hemiplegia

CROSSED SYMPTOMS

-Contralateral hemparesis
-Ipsilateral flaccid paralysis of the tongue: tongue deviates TOWARDS lesion side

What is the Medial Medullary syndrome caused by?

-Contralateral loss of pain and temperature from the body
-Ipsilateral loss of pain and temperature from the face
-Difficulty swallowing (dysphagia), hoarseness (dysphonia), difficulty breathing (dyspnea)
-Ipsilateral loss of gag reflex


Could also see: ipsilateral horner's syndrome, nystagmus, nausea, ipsilateral loss of taste.

What is LATERAL medullary syndrome caused by?

-Contralateral hemiplegia
-Contralateral lower facial paralysis
-Ipsilateral oculomotor nerve palsy (diplopia)

-An upper motor neuron lesion
-Stroke in the internal capsule

-caudally: line between the posterior commissure and mammillary bodies
-rostrally: interventricluar foramen of Monro, lamina terminalis and optic chiasm
-medially: divided in half by 3rd ventricle
-laterally: optic tract and internal capsule
-Its superior surface forms the floor of the lateral ventricles

-habenular nuclei: seen very well in sagittal cross section just anterior of the posterior commissure
-pineal gland

It is part of of the VISCERAL MOTOR PATHWAY
-how emotions and smell influence visceral functions

What is the passageway? (starting from septal area?)

-In children: antigonadotrophic function delaying the onset of puberty
-In adults: regulates circadian rhythms

Eye, retinohypothalamic tract, suprachiasmatic nucleus (SCN), Lateral horn, Superior Cervical Ganglion, Pineal Gland

Biological nucleus

Sympathetic activity increases at NIGHT, stimulates MELATONIN production, which depresses the sleep (puts you to sleep).

Remember that light inhibits the pathway

1. Relay center
2. MAJOR INTEGRATION CENTER as well!!! decides what information should reach the cortex.

1. Lateral
2. Medial
3. Anterior

They are divided by the INTERNAL MEDULLARY LAMINA

Ventral Anterior (VA)
Ventral Lateral (VL)

VPL, VPM

1. affective behavior
2. MEMORY and integration of somatic and visceral activities

It is a relay station for the limbic system

GLOBUS PALLIDUS

Dentate nucleus

Medinal geniculate nucleus (MGN)
Lateral geniculate nucleus (LGN)

cortical arousal and sleep

Their synaptic oscillations need to be in sync or pulsating at the SAME rate

Receives inputs from the motor cortex and projects to cuadate and puttamen to conrol MOTOR MECHANISMS

Reticular nucleus

Receives information from reticular formation and ascending pain pathways.

What does it do to the other nuclei in the thalamus?

-Contralateral himesensory loss in head and body
-Dysesthesia (unpleasant feeling by something that shouldn'tt heart)
Intractable thalamic pain
-Emotional instability

What is it caused by?

helps
-initiate and control movement

1. Infundibullum (pituitary stalk)
2. Tuber Cinerum

periventricular zone, medial and lateral zones

1. preoptic
2. anterior chiamsatic
3. middle tuberal
4. posterior mammillary

think of the drawing where you can see the optic chiasm cross with the mammilllary bodies.

1. Medial forebrain bundle
2. Stria terminalis and ventral amydalofugal pathway
3. Fornix
4. Mammillothalamic tract

1. Homeostasis
2. Motivated behavior: hunger, thirst, sex
3. Circadian rhythms via the suprachiasmatic nucleus

FORNIX

The stria terminalis and the amygdalofugal pathway

Allocortex is the oldes part of the brain it is further subdivided into
-paleocortes: olfactory, limbic
-Archicortex= hippocampal cortex

What is the allocortex involved in?

macro-osmic: paleocortex/olfactory
micro-osmic: huge areas devoted to vision.

Mammals (and us) have micro-osmic brains

Layer I is the youngest/newest and is on the outside.

Molecular layer, not known

External granular layer, local output

External pyramidal, collosal output layer

Internal granular, THALAMIC INPUT RECEIVING LAYER

Internal pyramidal, CORTICAL OUTPUT layer

Multiform layer. Thalamic reciprocal projection layer.
Sends main output to the thalamus

Stellate

granular = stellate

They are giant pyramidal cells found in precentral gyrus motor cortex, area 4 and are scattereed in Layer V

Layers
IV (mainly)
VI (remember that it is the reciprocal thalamic layer)
I (barely)

What are these thalamic inputs important for?

CORTICAL outpu
-layers II, III

Layere V is output but SUBCORTICAL

Heschl's gyrus areas 41 and 42

In the Parietal lobe
Remember that the SENSORY post-central gyrus is ALSO found in the parietal lobe

Brodmann's area 4 is the premotor cortex found in the frontal lobe

-delayed gratification
-executive decisions
-motivations

they made the motor map present in the brain apparent in humans

Spatial relationships

going to striatum or caudate + putamen
Important for the generation of motion

motor learning

It is going to superio and inferior colliculi.
It is imortant for body orientation and the control of eye movement.

NOOOO
but they can ultimately do so by going through the brainstem

The 2 layers are clearly divided in layer 4.
If they were to be divided in the other layers what would you have

Language in temporal lobe
Speech in frontal lobe

Frontal lobe

non-fluent aphasia: can understand but can't produce language

Fluent aphasia.
Can't understand but can produce sentences

YES, because information will go to the left side of the brain where speech is found.

Most commonly found in layer IV, also seen in layers II and I