Neurological Development Flashcards
What is gastrulation?
- A phase early in embryonic develpoment in which a single layer blastula into a trilaminar or “three-layered” blastula.
What is developed during gastrulation, the body or the nervous system?
The body.
What are the 3 layers that are differentiated during gastrulation?
- Ectoderm
- Mesoderm
- Endoderm
What is formed by the ectoderm?
- Entire nervous system
- Skin of body
What is formed by the mesoderm?
- The connective tissue of the body
What is formed by the endoderm?
Lining of structures like the GI tract, pancreas, stomach, and other visceral structures.
What structure is formed on the blastula during the begining of gastrulation?
- Primitive streak
What neurulation?
- The formation of the neural tube
What developmental structure forms the CNS?
The neural tube.
What developmental structure forms the pNS?
The neural crest.
What is the first structure formed during neurulation?
- The neural plate.
What is the neural plate?
- A thickening of the ectoderm caused by cuboidal epithelial cells becoming columnar.
What 3 major structures are formed during neurulation?
- Neural tube
- Neural crest
- Epidermis
What structure covers the neural tube once it is created?
- The epidermis
What structure is formed on day 6 of development?
- The blastula
What event occurs at day 1 of development?
- Fertilization
What event occurs at day 6 of development?
- Implantation
When does the primitive streak begin development?
- 13 - 14 days into development
By what process is the primitive streak formed on the blastula?
- Invagination: Cells migrate underneath the outer cell layer , displacing the underlying cells until 3 germ layers are formed
What is the dorsal layer of the primitive streak?
- Ectoderm
What is the middle layer of the primitive streak?
- Mesoderm
What is the ventral layer of the primitive streak?
- Endoderm
Where is the primitive streak found on the blastula?
On the inside.
When does neurulation begin?
- Day 18 of development
How does the primitive streak thicken after the 3 layers have been formed?
Cells turn from cuboidal to columnar.
Which layer of the primitive streak becomes the neural plate?
The ectoderm
Why does the ectoderm invaginate into the endoderm and mesoderm?
Because the ectoderm divides at faster rates.
How is the neural tube formed by the neural plate?
- The plate continues invaginating into the ventral layers until the 2 lateral sides of the plate meet dorsally, closing off the neural plate into the neural tube.
When does the neural tube completely close?
At 28 days.
What does the excess ectoderm directly lateral to the neural tube pinched off during neural tube closure form?
The neural crest.
What is the inner layer of cells of the neural tube called?
The neural epithelium.
What does the neural epithelium form in the developed adult?
The ependyma/ ependymal layer
At which region does the neural tube close at 24 days?
The cervical region (the tube then continues to close up and down from the cervical region)
What is the small cleft on the lateral sides of the inside of the neural tube called?
- The sulcus limitans
What is the significance of the sulcus limitans?
Separates the developing gray matter of the nervous system into basal and alar sections.
What does the non- neural crest and neural tube ectoderm form?
The skin.
What structure forms the neurons and glia of the PNS?
The neural crest.
What structure forms the neurons and glia of the CNS?
The neural tube.
What are the lateral bumps of mesoderm called in the developing embryo?
- Somites
What causes the enlargement and sulci of different portions of the neural tube?
Areas of fast cell division, and areas of slower cell division.
Which portion of the neural tube has the fastest division?
- Rostral
When does the primary vesicle stage occur?
- 28 days of development
Which portion of the embryo forms the forebrain, midbrain, and hindbrain during the primary vesicle stage?
Forebrain: Prosencephalon
Midbrain: Mesencephalon
Hindbrain: Rhombencephalon
Why does the cervical flexure occur?
The nervous system is growing so fast that it bends in on itself.
During what stage of neurodevelopment does the cervical flexure occur?
Primary vesicle.
When does the secondary vesicle stage occur?
42 days/ 6 weeks.
What 2 structures are formed by the proencephalon during the secondary vesicle stage?
- Telencephalon (rostral portion)
- Diencephalon (caudal)
What structure is formed by the telencephalon?
The cerebral hemisphere
What structure is formed by the diencephalon?
The thalamus
What 2 structures does the rhombencephalon form during the secondary vesicle stage?
- Metencephalon
- Yelencephalon
What is formed by the metencephalon and yelencephalon?
- The brain stem
What 2 flexures are formed during the secondary vesicle stage?
- Cephalic flexure
- Pontine flexure
Why is the cervical flexure important?
- The brain begins for fold in upon itself, and changes the orientation of rostral, caudal, ventral, and dorsal.
(Ventral and dorsal are inferior and superior)
Why does the telencephalon fold in onto itself?
- It can’t grow outwards out of the skull
What direction does the telencephalon grow?
Posteriorly and laterally.
Where does the diencephalon end up becoming embedded?
Within the telencephalon
When is the peak of neuron cell division?
3 months.
When do sulci and gyri begin forming in the brain?
At 6 months to increase surface area. (Occurs through invagination)
When does neuron cell division decline dramatically?
- At 6 months.
What is responsible for the growth of the brain beyond 6 months forming the sulci and gyri?
- The proliferation of glial cells
- The enlargement of neurons
When does glial division slow down?
- 2 years of development
Do glial or neurons continue to divide throughout life?
Only glial
How do cells grow in relation to the sulcus limitans?
Outword, and diagonally.
What cell layer forms gray matter?
- The mantle layer
What cell layer forms white matter?
- The marginal layer
Which layer is mostly axons?
- The marginal layer
What horn is formed by alar cells? Is the horn sensory or motor?
The dorsal horn; sensory
What horn is formed by basal cells? Is the horn sensory or motor?
The ventral horn; motor
How is the spinal cord organized during 3 months development medially to laterally?
- The neural epithelial layer
- The mantle zone
- The marginal zone
Cells migrate laterally
What 2 types of cells may the neural epithelials cells differentiate into? (The specific names)
- Neuroblast (neuron)
- Spongioblast (glial cell)
What is formed by collections of neurons in the periphery?
Ganglions
What are somites?
Bumps of mesoderm that the neural tube grows into
What is the source of the cells that grow into dorsal root ganglions?
Neural crest cells
What 3 characteristics are possessed by each somite?
- Sclerotome
- Dermatome
- Myotome
What are the 2 parts of each myotome/ spinal nerve?
- Epaxial division (dorsal rami)
- Hypaxial division (ventral rami)
What are the myotomes called cranial to the cerivcal portions?
Occipital.
What muscles are innervated by the occipital myotomes? By which nerve?
- Muscles of the tongue
- Innervated by the hypoglossal nerve
What myotomes are found rostrally to the occipital myotomes?
The preotic myotomes
What muscles are supplied by the preotic myotomes, and by which nerves?
- The extraocular muscles of the eyeball
- III, IV, and VI cranial nerves
What is another name for the occipital somites?
- Postotic somites
What senses are innervated by the otic somites?
- Balance and equilibrium
- Hearing
What are the pharyngeal/ branchial arches?
- Mesodermal outpouchings to the left and right sides of the developing pharynx.
When do the pharyngeal arches form?
- The 4th week of development
What cranial nerve is developed by the mandibular arch (I)?
- V
What muscles are innervated by the mandibular arch?
- The muscles of mastication
- Anterior belly of digastric
- Tensor tympani
- Myohyoid
- Tensory veli palatini
What cranial nerve develops from the Hyoid arch (II)?
- VII
What 4 muscles are innervated by the hyoid arch?
- Facial expression muscles
- Posterior belly of digastric
- Stapedius
- Stylohyoideus
What cranial nerve develops from the 3rd pharyngeal arch?
- CN IX (glossopharengeal)
What muscle is supplies by the 3rd pharyngeal arch?
- Stylopharyngeus
What cranial nerve develops from the 4th pharyngeal arch?
- X (superior laryngeal branch)
What muscle is innervated by the 4th pharyngeal arch?
- Cricothyroid muscle
What cranial nerves develop from the 5th and 6th cranial arches?
- X (recurrent laryngeal branch)
- XI (cranial accessory)
What muscles are innervated by the 5th and 6th pharyngeal arches?
- Muscles of pharynx and larynx (except stylopharyngeus)
- Palate muscles (except Tenso vali palantini)
What 3 structures are somatically innervated above the cervical region?
- Eyes
- Ears
- Tongue
What arch innervates the stylopharyngeus?
- Arch III/ Cranial nerve IX
What arch innervates the muscles of mastication?
- Arch I (mandibular arch)
What arch innervates the muscles of pharynx and larynx (except the stylopharyngeus)?
Arches V and VI.
What arch innervates the anterior belly of the digastric muscle?
- Arch I (mandibular arch)
What arch innervates the posterior belly of the digastric muscle?
- Arch II (hyoid arch)
What arch innervates the cricothyroid muscle?
- Arch IV
What arch innervates the palate muscles (except the Tensor veli palantini)?
- Arches V and VI
What arch innervates the stapedius?
- Arch II (Hyoid)
What arch innervates the muscles of facial expression?
- Arch II (Hyoid)
What arch innervates the mylohyoid?
- Arch I (Mandibular)
What arch innervates the Tensor Veli Palatini?
- Arch I (Mandibular)
What arch innervates the stylohyoideus?
- Arch 2 (hyoid)
What arch innervates the Tensor Tympani?
- Arch I (Mandibular)
