Development of brain
Three to four-week embryo:
forebrain (prosencephalon)
midbrain (mesencephalon)
hindbrain (rhombencephalon)
Development of Brain
5-week embryo
telencephalon (cerebrum)
diencephalon (thalamus, hypothalamus & epithalamus)
mesencephalon (midbrain)
metencephalon (pons & cerebellum)
myelencephalon (medulla oblongata).
Forebrain
Midbrain
Hindbrain
Forebrain - Cerebrum & Diecephalon (3)
Midbrain & cebral aqueduct
Hindbrain - pons & cerebellum + medulla
Brain stem
consists of?
continuation of spinal cord
consists of medulla oblongato, pons & midbrain
second largest part of the brain.
posterior to brain stem
Cerebellum
Diencephalon
superior to brain stem
gives rise to thalamus, hypothalamus & epithalamus
largest part of brain
cerebrum
cranial meninges
dura mater - 2 layers (perieosteal & meningeal)
arachnoid mater
pia mater
(3) extensions of the dura mater separate parts of the brain:
1) falx cerebri - seperate the 2 cerebral hemispheres
2) falx cerebelli - seperate the 2 cerebellar hemispheres
3) tentorium cerebelli - seperate cerebrum from cerebellum
Extensions of the Dura Mater: Brain Blood Flow and the Blood-Brain Barrier
Brain receives approximately _____% of the total blood supply.
Internal __ & __ arteries carry blood to brain.
Internal _____veins return blood from the brain.
Blood-brain barrier (BBB) protects brain from?
20%
internal carotid & vertebral arteries - blood to brain
internal jugular veins return blood from brain
harmful substances.
Cerebrospinal Fluid (CSF)
clear, colourless fluid that protects CNS from chemical & physical injuries, absorbs shock, helps transport nutrients & wastes from blood & nervous tissue
circulates through cavities in brain (ventricles) & spinal cord (central canal) & in subarachnoid space
Ventricles
(3) & cerebral aqueduct
CSF-filled cavities within the brain.
1 lateral ventricles - in each hemisphere seperated byb septum pellucidum
third ventricle - along midline superior to hypothalamus
cerebral aqueduct - midbrain
fourth ventricle - between brain stem & cerebellum
CSF formation & circulation
formed in choroid plexuses of lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct (midbrain)→ 4rth ventricle → median aperture/lateral apertures (2) → subarachnoid space →central canal
Choroid plexus
networks of capillaries in the walls of the
ventricles.
Ventricles are lined by __ cells
ependymal
plasma is drawn from choroid plexuses through ependymal cells into ventricles to produce CSF
CSF is reabsorbed into blood by?
arachnoid villi - extensions of arachnoid that project into dural venous sinuses (sugerior sagittal sinnus)
Brain Stem (medulla, pons & midbrain) and Reticular Formation
Medulla Oblongata
continous with superior spinal cord
white matter tract contains all sensory & motor tracts between spinal cord & other parts of brain
white matter bulges on anterior - pyramids formed by large corticospinal tracts that pass from cerebrum to spinal cord
- common site of decussation of tracts - crossing over
Centers of the Medulla Oblongata
Vital centers:
cardiovascular
respiratory
also includes centers for vomiting, swallowing, sneezing, coughing and hiccupping.
houses 5 pairs of cranial nerves (VIII-XII)
portion of 3rd ventricle found here
Midbrain (mesencephalon)
Extends from the pons to the diencephalon.
Part of the ventricle found here- cerebral aqueduct - connects 3rd & 4rth ventricle
anterior part contains cerebral peduncles
posterior part - tectum
superior colliculli, inferior colliculi & substantia nigra
Cerebral Peduncles - paired bundles of axons in anterior part of midbrain
consists of?
Tectum
axons of the corticospinal, corticopontine and
corticobulbar tracts.
Tectum- situated posteriorly and contains 4 rounded elevations: 2
superior ones called superior colliculi and 2 inferior ones called inferior colliculi
Midbrain:
Substantia Nigra
large area with dark pigments. Help control subconscious muscle activities.
Loss of neurons here is associated with Parkinson disease.
Redc Nucleus of Midbrain
: Help control voluntary movements of the limbs
Midbrain contains cranial nerves....
III-IV
Reticular Formation
Extends from upper part of spinal cord, throughout brain stem & into
lower part of diencephalon.
Part of the reticular formation called the Reticular activating System (RAS) consists of?
consists of sensory axons that project to the cerebral cortex
S helps maintain consciousness.
Cerebellum
vermis
anterior & posterior lobes
flocculonodular lobe
cerebellar cortex
arbor vitae
2nd largest part of brain
central constricted area = vermis
anterior and posterior lobes control subconscious aspects of skeletal movement.
flocculonodular lobe - equilibrium & balance
cerebellar cortex - gray matter in form of parallel folds called folia
arbor vitae - tracts of white matter
Cerebellar peduncles
3 pairs - superior, middle & inferior
attach cerebellum to brain stem
functions: coordinate movements, regulate posture & balance
Thalamus
intermediate mass joins right & left sides of thalamus
(7) major nuclei: anterior, medial, lateral, ventral, intralaminar, midline, reticular
major relay station for most impulse reaching primary sensory areas
transmits info from cerebellum & basal nuclei to primary motor area
Hypothalamus
inferior to thalamus
consists of mammillary body, median eminence, infundibulum, and # of nuclei.
Functions of the Hypothalamus
Control of the ANS
production of hormones
regulation of emotion & behavioral patterns, eating & drinking, body temp, circadian rhythms
