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.
Label the cranial nerves as they leave the brain
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glassopharangeal
Vagus
Accesory
Hypoglossal
What are the different sections of CN1?
Olfactory tract - first exit brain
Olfactory bulb - sit ontop of cribriform plate
Olfactory nerve - travel through the cribiform plate
What are the different parts of CN2?
Optic tract - first leaves brain, before chiasm
Optic nerve - after chiasm (closer to eyes)
Label the different foramina through which cranial nerves leave the skull
Cribiform plate
Optic canal
Foramen ovale
Internal acoustic meatus
Jugular foramen
Hypoglossal canal
Superior orbital fissure
Foramen rotundum
What is anosmia and what can cause it?
The full or partial loss of smell
Can be caused by injury to the cribiform plate.
What is the function of CNIII?
General somatic efferent - to extraocular muscles (levator palpebrae superiorib, inferior oblique, sup, mid and inf recti)
General visceral efferent - to pupillary constrictor muscles
Efferent limb of pupillarly light reflex
Pupillary constriction and lens accomodation
Through what foramen does CN3 leave the cranium?
The superior orbital fissure
Through which foramina does the optic nerve leave the cranium.
The optic canal
What is the function of CN4?
General somatic efferent - extraocular superior oblique muscle
Depress and abduct the eye.
How does CN4 leave the cranium?
Superior orbital fissure
What is the function of CN6?
General somatic efferent - lateral rectus muscle - eye abduction
How does CN6 leave the cranium?
Superior orbital fissure
What is the function of CN5?
Afferent limb of corneal reflex
Opthalmic - general somatic afferent - above lower eyelid
maxillary - general somatic afferent - lower eyelid to the upper lib
Mandibular - general somatic afferent - below upper lip, and special visceral efferent to muscles of mastication
What are the three different sensory nuclei of the trigeminal nerve?
Mesencephalic - proprioception
Principal - light touch and discrimination
Spinal - pain, temp and crude touch
How can wetest the motor function of the mandibular nerve?
Jaw jerk - tapping on chin
What provides the sensory innervation to different regions of the head/neck?
Green - CN v1 - opthalmic
Blue - CNV2 - maxillary
Red - CNV3 - mandibular
Purple - branches from cervical plexus
Organe - posterior rami of cervical spinal cord
How does the facial nerve exit the cranium?
Enters the internal acoustic meatus
Exit the stylomastoid foramen.
How do the divisions of the trigeminal nerve exit the cranium?
Ophthalmic - superior orbital fissure
Maxillary - foramen rotundum
Mandibular - foramen ovale
What is the role of CN7?
GSA - touch, pain and temp to skin behind ear
SVA - tase to anterior 2/3 of tongue
GVA - parasympathetic to lacrimal gland, submandibular and sublingual gland
SVE - muscle of facial expression and posterior auricular for ear wiggle
What are the different branches of the facial nerve?
Temporal branches
Zygomatic branches
Buccal branches
Marginal mandibular branches
Cervical branches
What is the function of the vestibulocochlear nerve?
Special somatic afferent fibres for hearing and muscle
Cochlear - auditory senses
Vestibular - balance and head position
Where does the vestibulocochlear nerve leave the cranium?
The internal acoustic meastus - does not leave skull just travels within
What is the role of the glassopharyngeal nerve?
GSA - sensation from posterior 1/4 tongue and pharynx
GSE - motor to stylopharyngeus and pharyngeal constrictors.
SVA - taste post 1/3 of the tongue
GVE - parasympathetic to parotid glands
SVE - motor to stylopharyngeus
How does the glassopharyngeal nerve leave the cranium?
The jugular foramen
What is the function of the vagus nerve?
SVE -Motor - to pharynx, soft palate muscles and larynx
GVE - Parasympathetic - smooth muscle of RT and GIT
GVA - sensory information from body viscera
SVA, - taste to root of tongue and epiglottis
GSA - skin around ear
What is the function of the accessory nerve?
GSE - trapezius and sternocleidomastoid
Note has a cranial root and a spinal root.
How does the accessory nerve leave the cranium?
Spinal accessory - leaves through the jugular foramen
What is the function of the hypoglossal nerve?
GSE - controlling tongue muscles
All extrinsic except palatoglossus
therefore - genioglossus, hypoglossues and styloglossus
Also innervates intrinsic muscles
What would be the consequence of a lesion to the hypoglossal nerve?
Tongue would deviate towards the affected side
Speech disturbances
What cranial nerves originate from the cerebrum?
CN1 - olfactory
CN2 - optic
What cranial nerves originate from the midbrain?
CN3 - oculomotor
CN4 - trochlear
What cranial nerves orignate from the pons?
CN5 - trigeminal
What cranial nerves orignate from the pontomedullary junction?
CN6 - abducens
CN7 - facial
CN8 - vestibulocochlear
What cranial nerves originate from the medulla?
CN10 - vagus
CN11 - accesory
CN12 - hypoglossal
Cn9 glassopharyngeal
What bone is labelled in image A?
Sphenoid
What is a functional consequence of occlusion of the posterior cerebral artery?
Problems with primary visual processing (primary visual cortex)
What is a functional consequence of occlusion of the middle cerebral artery?
Problems with speech production
Brocas area of frontal lobe
What type of haemorrhage is shown on this CT?
Epidural
Dura still adhere to brain
