Unit 1 Content

stages of neural development in utero

pre-embryonic, embryonic, fetal

how long is pre-embryonic stage

conception to 14 days

how long is embryonic stage

15 days to end of 8th week

how long is fetal stage

9th week to birth

key points of pre-embryonic stage

fertilization, zygote creation, cellular division, migration, differentiation

blastocyst

result of cellular division

describe migration in pre-embryonic stage

blastocyst attaches to lining of uterus

when does differentiaton in pre-embryonic stage start

2nd week, after migration

describe differentiation in pre-embryonic stage

creation of bilaminar disc, then becomes trilaminar disc

what are the layers of bilaminar disc

epiblast and hypoblast

which of the layers of bilaminar disc is most superficial

epiblast

describe gastrulation

differentiation of trilaminar disc

what are the layers of trilaminar disc

ectoderm, mesoderm, endoderm

significance of ectoderm

development of nervous system and skin

significance of mesoderm

development of muscles, connective tissue, blood vessels, skeleton, kidneys, reproductive system

significance of endoderm

development of GI tract, endocrine glands, lungs, liver, other internal organs

describe neurulation

process of forming neural tube

when does neurulation take place

3rd to 4th week, after gastrulation

describe primary neurulation

neural groove forms in neural plate, edges fuse to form neural tube, cranial end becomes brain, caudal end becomes spinal cord, neural crest cells form at edges of neural plate

what happens at cranial end of neural tube

cranial neuropore closes, expands and differentiates into brain

what happens at caudal end of neural tube

caudal neuropore develops into spinal cord

describe secondary neurulation

completes development of spinal cord at caudal end

describe a somite

paired segmental block of embryonic tissue that develops along neural tube

significance of somite

development of vertebrae, ribs, skeletal muscles, dermis of skin; each segment associated with a spinal nerve

how does neural tube defect develop

lack of folate (B vitamin)

describe spina bifida

neural tube defect involving incomplete development/closure of structures surrounding spinal cord

describe anencephaly

neural tube defect involving partial or complete absence of brain tissue

significance of neural crest cells

migrate throughout developing embryo for formation of peripheral nervous system

describe the sulcus limitans

longitudinal groove within neural tube that separates alar and basal plates

list 3 layers of early spinal cord development

marginal, mantle, ependymal

which of 3 layers of early spinal cord development is most superficial

marginal

which of 3 layers of early spinal cord development is most deep

ependymal

significance of marginal layer

becomes white matter of spinal cord, contains axons and nerve fibers that become ascending/descending tracts

significance of ascending tracts

carry sensory information to brain

significance of descending tracts

carry motor information from brain

significance of mantle layer

becomes gray matter, contains neural cell bodies

list 2 regions of mantle layer

alar plate, basal plate

where is alar plate

dorsal part of mantle later, visually sharper

where is basal plate

ventral part of mantle layer, visually more rounded

significance of alar plate

develops into dorsal horn for sensory function

significance of basal plate

develops into ventral horn for motor function

significance of ependymal layer

lines central canal to transport cerebrospinal fluid

significances of fetal stage

continues growth and maturation of nervous system, neurons continue to differentiate and form connections, axons begin to myelinate

what does central nervous system consist of

brain and spinal cord

what does peripheral nervous system consist of

12 cranial nerves, 31 spinal nerves

function of brain

receive and process sensory information, plans and initiates motor responses, regulate body systems, analyze and store memories

function of spinal cord

conduct signals to and from brain and controls certain reflexes

2 types of neurons in peripheral nervous system

motor and sensory

function of motor neurons

transmit information from central nervous system to muscles and glands

function of sensory neuron

transmit information from sensory receptors to central nervous system

2 systems of motor neurons

autonomic nervous system, somatic nervous system

function of autonomic nervous system

regulate involuntary functions of body in smooth muscles, cardiac muscles, glands

function of somatic nervous system

control voluntary movement in skeletal muscles, sensation, proprioception

2 parts of autonomic nervous system

sympathetic nervous system and parasympathetic nervous system

sympathetic nervous system mnemomic

fight or flight

parasympathetic nervous system mnemonic

rest and digest

what is nervous system made up of

billions of neurons

describe a neuron

basic functional cell of nervous system

parts of neuron

dendrite, cell body, axon

function of dendrite

receive information

function of cell body

process and integrate information

function of axon

send information

describe a fascicle

bundle of axons

describe a nerve

bundle of fascicles

list types of nerves

sensory, motor, mixed

describe sensory nerves

aka afferent, carry sensory information toward central nervous system

describe motor nerve

carry motor information away from central nervous system

describe mixed nerve

carry information to and from central nervous system

what type of nerve are most peripheral nerves

mixed nerve

how does information travel between brain and spinal cord

ascending and descending tracts

ascending/descending tracts can be found where in spinal cord

white matter as bundles of axnos

describe a funiculus

regions of white matter made of multiple tracts

describe the pathway of motor information

nerve signals from motor cortex travel through descending tract of spinal cord to body

describe pathway of sensory information

afferent fibers of sensory neurons travel through ascending tract of spinal cord to sensory cortex

does sensory information travel ventrally or dorsally

dorsally

does motor information travel ventrally or dorsally

ventrally

describe a spinal nerve

joining of dorsal and ventral roots

location of spinal nerves

at intervertebral foramen, between inferior/superior notches of adjacent vertebrae

where to find dorsal root

nerves entering spinal cord from dorsal end

where to find ventral root from ventral end

nerves exiting spinal cord from

describe a ganglion

group of cell bodies of sensory neurons

describe a ramus

contain both sensory and motor nerves, spinal nerves splits into two rami

describe a dorsal ramus

supply intrinsic back muscles and skin of posterior trunk

describe a ventral ramus

supply anterolateral trunk and limbs

significance of ventral ramus

form major nerves plexuses

key takeaway of spinal nerves

roots are either sensory or motor never both, spinal nerves and rami are always mixed

how many cervical spinal nerves are there

8

how many thoracic spinal nerves are there

12

how many lumbar spinal nerves are there

5

how many sacral spinal nerves are there

5

how many coccygeal spinal nerves are there

1

describe a myotome

group of muscles supplied by single spinal nerve

clinical significance of myotomes

testing specific movements help assess function of spinal nerve

function of spinal nerve plexus

create more pathways for signals to reach multiple muscle fibers from single nerve root

describe a dermatome

a region of skin corresponding to a spinal nerve

describe a herniated disc

intervertebral disc material pushes through tear and push on spinal nerve root

significance of herniated disc

spinal nerve root compressed affects sensation/movement associated with spinal nerve root

how many pairs of cranial nerves do we have

12

what is cranial nerve I

olfactory

what is cranial nerve II

optic