1-Development of Nervous System

What are the initial 3 primary brain swellings in neural tube development and what parts do they give rise to?

1. Prosencephalon = forebrain 2. Mesencephalon = midbrain 3. Rhombencephalon = hindbrain

Basal plates within mesencephalon will form 2 columns.

1. Somatic efferent - motor output to extraocular mm. - CN3,4 2. general visceral efferent - motor output to ciliary ganglion of eye - CN3

What are the 5 secondary brain swellings & their adult derivatives that the 3 primary brain swellings differentiate into?

1. Telencephalon = cerebral hemisphere (eg. cortex) 2. Diencephalon = thalamus, hypothalamus, few more 3. Mesencephalon = midbrain 4. Metencephalon = pons, cerebellum 5. medulla (oblongata)

Alar plates of mesencephalon also form in 2 parts, however, neither of which resemble the previously seen 3 groups. What parts & what functions do they have?

1. superior (anterior) colliculus - visual relay 2. inferior (posterior) colliculus - auditory relay

Postganglionic neurons are located where?

PNS in ganglia

Function of pons and cerebellum?

Pons - serves as pathway for nerve fibers between spinal cord, cerebral cortices, cerebellar cortices Cerebellum - coordination center for posture & movement

Most regions of cord have segregation of dorsal and ventral neurons to form intermediolateral cell columns (intermediate horn) -- what levels have these?

T1-12, L1-L2, & S2-S4

What do thoracic and lumbar vs. sacral intermediolateral cell columns contain?

Thoracic and lumbar contain: visceral motor neurons for sympathetic div. Sacral contain: visceral motor neurons for parasympathetic div.

The thicker part of telencephalon buldges into neural canal to form ___.

basal ganglia.

Basal and alar plates are visible throughout the ___ and spinal cord, however, higher centers (cerebral hemisphere & cerebellum) show accentuation of ____ plates and regression of ____ plates.

brainstem; alar; basal

Dorsolateral parts of alar plates will grow out (rhombic lips) & encompass 4th ventricle, merging to form ___.

cerebellar plate

Rudiment of cerebellum is first recognizable as a pair of thickened ____. These plates are formed when ___ are compressed together By 2nd month, cranial portions of growing cerebellar plates meet across midline forming a single primordium that covers 4th ventricle. The fused plate formed ___ and 2 hemispheres will bulge laterally and ___.

cerebellar plates; rhombic lips; vermis; dorsally

___ is derived from both alar plates of metencephalon & adjacent rhombic lips.

cerebellum

Cerebral hemispheres first appear as bubble-like outgrowths of telencephalon. At 16 weeks, the growing hemispheres are oval and have expanded back to cover diencephalon. The thin roof & lateral walls of each hemisphere represent future ___. The thicker floor contains neuronal aggregations called ___, which give rise to basal ganglia. The growing hemispheres press against diencephalon walls leading to thalami neural tissue being continuous with floor of cerebral hemisphere. This former border is eventually crossed by a massive axon bundle called ___.

cerebral cortex; ganglionic eminences; internal capsule

___ is within 4th ventricle and attached to roof plate, it produces CSF.

choroid plexus

Diencephalon has alar plates & a roof plate. Roof plate will form __ of __ ventricle and will form ___ (aka epiphysis). What function also?

choroid plexus; 3rd; pineal body; Pineal body - modulates how light/dark impact the endocrine system & behavior.

parasympathetic corresponds to ___ region. sympathetic corresponds to ___ region.

craniosacral; thoracolumbar

Marginal layer around basal plates will enlarge to form ___. What function does this have?

crus cerebri (aka cerebral peduncles) - which like the pons, acts as a pathway for fibers between cerebral cortex, pons, & spinal cord.

Cerebral hemisphere growth is continuous through embryonic & fetal development & after birth. Cerebral hemispheres are initially smooth, but cerebral cortex folds into complex pattern of ___ (ridges) and ___ (grooves), serving to ___ SA until fully grown. Process begins in 4th month and by 6th month, several cerebral sulci form (eg. central sulcus). The pattern varies among individuals.

gyri; sulci; increase

Early diencephalon development occurs with a groove appearing within each alar plate called ___, which divides alar plate into large paired swelling representing thalamus and more ventral swelling representing hypothalamus.

hypothalamic sulcus

___ is transition zone between brain & spinal cord; it has posterior walls flipped out laterally, thus juxtaposing basal & alar plates. ___ remains posteriorly, formed by layer of epndymal cells covered in layer of ___ mater.

medulla; roof plate; pia

What does brain stem consists of?

mesencephalon (midbrain), metencephalon derivative: pons, myelencephalon (medulla oblongata)

All ganglia are derived from what?

neural crest cells

What is differentiation of neurons in mantle layer of spinal cord into 4 plates/columns?

pair of dorsal/alar plates & pair of ventral/basal plates; -dorsal/alar become association neurons in dorsal horns that receive synapses from afferent (incoming) fibers from sensory neurons of dorsal root ganglia -ventral/basal become somatic motor neurons in ventral horn and innervate voluntary muscles

Metencephalon contains same six groups within alar/basal plates, but additionally gives rise to ___ & ___.

pons & cerebellum

Basal plates will also organize themselves to form:

red nucleus (nucleus ruber) & substantia nigra

Association neurons may synapse with motor neurons on same (ipsilateral) or opposite (contralateral) side of cord forming a ___?

reflex arc, or it may also ascend to the brain.

Hindbrain is split into 8 ___, which give rise to ___ nuclei of CNs. The ___ nuclei of CNs are derived from ectodermal placodes & neural crest cells.

rhombomeres; motor; sensory

Embryology

the study of 9-month journey from single cell to a baby, looks at molecular, cellular, and structural factors contributing to formation of an organism.

Outgoing (efferent) motor neuron fibers exit via ___ roots.

ventral

Lumen of neural tube enlarges to form ____?

ventricles - interconnected chambers where CSF is produced

How is the nervous system organized?

Nervous System < (1) CNS (2) PNS < (2a) ANS < (2b) SNS < (2ai) Sympathetic (2aii) Parasympathetic (2bi) Sensory/afferent (2bii) Motor/efferent

Metencephalon (pons) alar/basal differentiation?

Basal plate: 1. somatic efferent - innervate lateral rectus m. of eye - CN6 2. special visceral efferent - innervate face muscles (CN7) & mastication muscles (CN5) 3. general visceral efferent - autonomic output to salivary & lacrimal glands - CN7 Alar plate: 4. general visceral afferent - autonomic input from soft palate & pharynx - CN7 5. special visceral afferent - taste - CN7 6. somatic afferent - general sensation from face, tongue, extraocular mm. - CN5,6,7 7. pontine nuclei - involved in transmitting info between cerebral & cerebellar cortex

____ plate develops into 3 motor columns. ____ develops into 4 sensory columns.

Basal; alar

What sections are the cranial nerves associated with?

CN1 - cerebral cortex CN2 - diencephalon CN3-12 - brainstem -CN3 - midbrain -CN4-12 - hindbrain (pons & medulla)

All 12 CN except ___ & ___ have nuclei located in brain stem (in basal & alar columns).

CN1 - olfactory & CN2 - optic

All preganglionic neurons are located where?

CNS

Myelencephalon (medulla) basal/alar differentiation?

From basal plate: 1. somatic efferent - innervate skeletal mm. of tongue - CN12 2. special visceral efferent - innervate pharyngeal arch mm. of larynx & pharynx - CN9,10,11 3. general visceral efferent - autonomic output - CN9,10 From alar plate: 4. general visceral afferent - autnomic input - CN9,10 5. special visceral afferent - taste - CN9,10 6. somatic afferent - general sensation from face (CN5), external ear, auditory meatus, eardrum (CN9,10) 7. Olivary nucleus - function: cerebellar input

The basal and alar cranial nerve nuclei of brainstem organize into 6-7 columns corresponding for 6 functions (3 motor, 3 sensory). What are they, their functions, and what CN they correspond to?

From basal plates: 1. somatic efferent - innervate extrinsic ocular mm. & tongue mm. - CN3,4,6,12 2. special visceral efferent - innervate striated mm. derived from pharyngeal arches as well as trapezius & sternocleidomastoid mm. (not from arches) - CN5,7,9,10,11 3. general visceral efferent - serve parasympathetic pathways - CN3,9,10 From alar plates: 4. general visceral afferent - receive impulses from sensory receptors in walls of thoracic, abd, & pelvic viscera - CN10 5. special visceral afferent - special senses (eg. taste, smell, vision, hearing, equilibrium) - CN7,9,8 6. somatic afferent - general sensation (eg. touch, temp, pain) over head/neck, oral & nasal mucosa, & pharynx - CN5,7,9

Each CN contains specific modalities and 10/12 CNs come from brain stem. Summarize the modalities in brainstem various nuclei of CNs.

Medulla - contains all 6 modalities Pons - contains all 6 modalities Midbrain - contains only somatic efferent & general visceral efferent