Central Nervous System- Spinal Cord Flashcards
central nervous system
brain and spinal cord
embryonic development
- neural plate forms from ectoderm
- plate invaginates to form neural groove and folds
- neural fold migrates to form neural crest
- neural groove becomes neural tube
- neural tube will form neural structures day 22
week 5 of embryonic development
two major flexures form and cause telencephalon and dienccephalon to angle toward brain stem
week 13 of embryonic development
cerebral hemispheres develop and grow posterolaterally to enclose diencephalon and rostral brain stem
week 26 of embryonic development
growing cerebral hemispheres begin to crease
birth of development
brain has developed an adult structure
defects of developing fetus caused by?
maternal exposure to teratogens
genetic mutations
types of defects in embryonic development
anencephaly
cerebral palsy
spina bifida
anencephaly
neural folds fail to fuse (no tube)
cerebrum never develops
fatal
cerebral palsy
infection, damage, or lack of oxygen to fetus causes brain damage
poor control of muscles, seizures, mental disability, deafness
3:1000 births
spina bifida
incomplete closure of neural tube because lamina/spinous process is missing from vertebrae
folic acid deficiency
where does spinal cord develop from?
posterior neural tube
basal plate
gives rise to ventral motor neurons
axons to synapses in muscles
alar plate
gives rise to dorsal interneurons
connection with dorsal root ganglia
neural crest cells
find and form dorsal root ganglion
axons that bring in sensory infromation
what does tube becomes in brain?
central canal and ventricles
ventricles
hollow chambers filled with CSF
continuous with one another and central canal of spinal cord
connected to subarachnoid space
ependymal cells
line cavities and ventricles to circulate CSF
types of ventricles
2 lateral ventricles
3rd ventricle in diencephalon
4th ventricle in hindbrain
central canal in spinal cord
functions of CSF
buoyancy to CNS organs -97% weight reduction
protects CNS from trauma/blows
nourishes brain
carries chemical signals
composition of CSF
watery solution
more specialized extracellular fluid
less proteins
different ionic concentration than plasma
150 mL replaced every 8 hours
choroid plexuses
produces CSF at constant rate
cluster of capillaries enclosed by pia mater and ependymal cells
ependymal cells use ion pumps to control composition of CSF, remove wastes and help cleanse CSF
tight junctions
blood-brain barrier
helps maintain stable envirnment for brain
tight junctions between capillary endothelia cells
astrocyte feet
separates neurons from some bloodborne substances
function of blood brain barrier
- selective barrier
- allow glucose, essential amino acids with facilitated diffusion
- toxins, wastes, and certain drugs excluded
- fat soluble substances can pass (O2, CO2, fats, alcohol, nicotine, anesthetics)
two areas where blood brain barrier is absent
vomiting center
hypothalamus
3 meninges covering CNS
dura mater
arachonoid mater
pia mater
spinal cord
extends from foramen magnum to 1st/2nd lumbar vertebrae
two way communication with brain
reflex center
protected by bones, meninges, CSF
epidural space
fatty tissue between vertebrae and dura mater
anesthetic injected or CSF taken out
dorsal half of spinal cord
sensory roots and ganglia
ventral half of spinal cord
motor root
how many spinal nerves are present on spinal cord
31 pairs
gray matter
cell bodies of neurons
located on internal part of spinal cord
dorsal horn
interneurons
ventral horn
somatic motor neuron cell bodies
axons form from ventral root
largest ventral horns
cervical and lumbar
more muscles to control in this area
lateral horn
autonomic motor neurons for visceral organs
sends axons out ventral root
dorsal root ganglion
cell bodies of dorsal root bringing sensory information in afferent nerves
spinal nerve
fusion of dorsal and ventral roots
paresthesia- loss of sensation or abnormal sensations, where is injury?
dorsal root
regulates sensory information
paralysis- loss of motor function, where is injury?
ventral root
regulates motor neurons for somatic system
flaccid paralysis
severe damage to ventral root or ventral horn cells
impulses do not reach muscles, no voluntary/involuntary control
muscle atrophy
spastic paralysis
upper motor neurons of primary cortex are damaged but spinal motor neurons remain intact
muscles not subject to voluntary control but remain healthy longer
neurons in brain damaged
transection
cross sectioning of spinal cord
total motor and sensory loss inferior to cut
paraplegia
transection between T1 and L1
lose leg control
quadriplegia
transection in cervical region
lose control of arms and legs
spinal shock
transient loss of function following an injury
all reflex activity caudal to lesion is depressed
function can return 2-48 hours after injury
poliomyelitis
destruction of ventral horn motor neurons by poliovirus
muscle atrophy
death due to paralysis of respiratory muscles
amyotrophic lateral sclerosis ALS
lou gehrig’s disease
progressive destruction of ventral horn motor neurons and fibers of pyramidal tract
loss of ability to speak, swallow, and breathe
5 years then death
glutamate excitotoxicity or attack of immune system
