Unit 14: External Brain Flashcards
What are the different histological classifications of the cerebral cortex?
Neocortex - makes up majority
Allocortex - more variable layering
Mesocortex - transition between neo and allo
What are the arrangements of the neocortex?
Arranged in six layers
Different in cell type and density
What is the following brain areas?
Note just posterior to all highlighted regions is the central sulcus
The light blue is the primary motor cortex
The dark blue is the supplementary motor area
The purple is the premotor area
What is the purpose of the parietal association area?
Aspects of attention and perceptual awareness
What is the purpose of the frontal lobe association areas?
Complex processes like planning, impulse control and self awareness
What are the different types of afferent cranial nerve fibres?
GSA - general somatic - sensory info from skin, skeletal muscle and joints
GVA - general visceral - sensory from visceral
SSA - special somatic afferent - sensory from ectodermal retina, cochlear and vestibular apparatus
SVA - special visceral - sensory info from endondermal nose and tongue
What are the different types of cranial nerve efferent fibres?
GSE - general somatic - motor to skeletal muscle
GVE - general visceral - secretomotor function to smooth muscles and glands
SVE - special visceral - motor to skeleral muscle of the pharyngeal arches
What is the role of CN1 (olfactory nerve)?
Specialised visceral afferent fibres for sense of smell
How does the olfactory nerve exit the skull?
Passes through cirbiform plate of ethmoid bone
Olfactory bulb sits deep to it, nerves project through
What is the role of the optic nerve?
Special somatic afferent fibres for vision
Afferent limb for pupillary light reflex
What is meant by neuralation?
The formation of the neural tube and its development into the spinal cord and the brain.
What is the process of neural tube formation?
Beings at day 18.
Embryonic disk has a cranial and cuadal end.
Notochord causes dorsal ectoderm to thicken forming a neural plate, The plate will start to fold forming a neural fold and a neural groove, continues to fold in on itself, forms a neural tube as two folds connect/fuse in the midlines and groove becomes an enclosed circle (the tube). Just before this fusion migratory nerual crest cells are released that acts as progentior cells to contribute to the development of structures throughout the body such as the cardia septa, the meningies and the sympathetic chain ganglia.
What is meant by the cranial and caudal neuropore?
Opening of the neural tube at the cranial and caudal end before formation is complete.
Communicate with the amnion.
When does the cranial neuropore form?
What happens next?
Day 25
Closes spontaneously
Followed by formation of primary brain vesilces
What are the primary brain vesicles?
Form after day 25 when the cranial neurpore closes
Prosencephalon - forebrain
Mesencephalon - midbrain
Rhombencephalon - hindbrain
Note cuadal neuropore is still open
What are the secondary brain vesicles?
Forebrain - develops into telencephalon and diencephalon
Midbrain - remains as mesencephalon
Hindbrain - develops into the metencephalon and the myelencephalon.
When does the caudal neural pore close?
Day 27
After the formation of the secondary brain vesicles.
What do the secondary brain vesicles become?
The telencephalon - becomes the cerebral cortex and he corpus striatum
The diencephalon becomes the thalamus and the hypothalamus
The mesencephalon - becomes the midbrain
The metelencephalon - becomes the cerbellum and the pons
The myelencephalon becomes the medulla.
What can cause different neural tube defects?
Failure of neural tube to close properly
Congenital - part of syndomres, chromosomal disorders, environmental exposure, folic acid deficiency/antagonists.
What is anencephaly?
Failure of cranial neural pore to spontaneously close
Brain fails to develop
Is incompatible with life.
High alpha-fetoprotein levels and polyhydramnios during pregnancy.
What is spina bifida?
The failure of the neural tube to close spontaneously close at the caudal end.
Results in failure or the vertebrae overlying the defect to form properly with vertebral arch remaining open.
What is open spina bifida occulta?
An asymptomatic defect caused by failure of the two halves of the vertebral halves to fuse at midline
Often small tuft of hair over site of defect
Spinal cord is not affected
Alpha-fetoprotein is normal
What is spina bifida with menigocele?
When meninges protrude through the gap between the two halves of the vertebral arches
Without protrusion of spinal cord
Defect is covered by skin
What is spina bifida with myelomenigocele?
When the spinal cord and menigeas protrude through the defect in the vertebrae.
Skin covers the defect
Alpha feto-protein levels increased
Associated with hydrocephalus and Chiari tube malformation.
