6.1 Central Nervous System Flashcards
Describe embryonic developemnt of the brain
starts as neural tube
- then develops pockets that expand, starts to wrap and get lobes
- then get secondary brain vesicles (telencephalon, diencephalon, mesencephalon, metencephalon and Myelencephalon_
- then develop into adult brain structures
What happens in brain development at week 5
2 major flexures form, cause telencephalon and diencephalon to angle toward brain stem
what happens to brain development at week 13
Cerebral hemispheres develop & grow posterolaterally (black arrows) to enclose diencephalon & rostral brain stem
what happens to brain development at birth
shows adult pattern of structures and convulutions
*lots of dumps and grooves to ince SA
What are the regions of the adult brain
- Cerebral hemispheres (has all the bumps and gorrvs)
- Diencephalon (middle part)
- Brain stem (midbrain, pons, and medulla) (brain stem)
- Cerebellum
Orientation words for brain
superior = dorsal
inferior = ventral
anterior = rostral
posterior - caudal
What are the five paired lobes of the cerebrum?
frontal, parietal, occipital, temporal
- have a bonus cortex deep to temporal lobe called Gyri of insula
*looks like boxing glove, thumb = temporal lobe
What are gyri, sulci and fissues
Gyri: Ridges (sticks up)
Sulci: shallow grooves
Fisue: deep groove
what separates teh precentral and postcentral gyrus
central sulcus
What separates the temporal from frontal and parietal lobes?
- lateral sulcus/sylvian fissue
*can pull this back to see insular
what separates the cerebrum from cerebellum
transverse cerebral fissure
what separates left and right hemispheres
longituinal fissue
what separates parietal and occipital lobes
- parieto-occipital sulcus
what separates the primary visual cortex
calcarine sulcus
What protects the brain?
- SCALP
- bone (skull)
- Blood brian barrier
- Membranes (meninges)
- Watery cushion (cerebrospinal fluid)
what are the layers of the scalp?
S: Skin
C: Connective tissue (dense)
A: Aponeurotic layer
L: Loose connective tissue
P: pericranium
What is the blood brain barrier?
- helps maintain a stable environment for brain (doesnt like change, needs stable environment (nervous tissue)
- physically separates neurons from certain bloodborne substances
- Acts as a metabolic barrier (Circulating catecholamines are inactivated by MAO in endothelial cells)
• Surrounds majority of brain tissue -> Absent in some areas (e.g. vomiting centre = area postrema & pituitary)
How do brain capillaries compare to most other capillaries?
- both have endothelial cells (simple squamous), pericytes (help support), and basement membrane
- brain cap have Astrocyte feet (wrap around capillaries to help insulate and alter permeability)
*form tight junctions
- these tight junctions between endothelial (epithelial) cells are keey in BBB -> excluse molecules except those that are lipid soluble from rbain tissue
what are the different transport routes in the blood brian barrier
- paracellular aqueous pathway
- transcellular lipophilic pathway
- transport proteins
- efflux pumps (extrude drugs)
- Receptor mediated transcytosis
- adsorptive transcytosis
- cell mediated transcytosis
What is the role of the meninges
* membranes
Cover & protect CNS
- Form partitions in skull
- Protect blood vessels & enclose dural venous sinuses
- Contain cerebrospinal fluid (CSF)
what are the layers of the meninges
Dura mater (hard mother )
– Arachnoid mater (spider mother)
– Pia mater (soft mother -> think pliable)
*dura = most superficial, pia = deep
desribe dura metter
*most durable
- two fused layers of fibrous connective tissue (dense regular)
- has periosteal and meningeal layers
*meningeal layer projects down into the longitudiional fissue
- has epidural space above and subdural space below
*both potential spaces, want it to be fused but could separate and has potential to create space -> intracranial bleed
What is Dura Mater Septa
two fused layers of meningeal dura metter
- Dural septa limits excessive movement of brain
- has flax cerebri (mid sag, occipital and cerebellum), tentorium cerebelli (transverse progections) Falx cerebelli (sep left and right cerebellum hemispheres)
What is arachnoid matter?
- middle later with weblike extensions
- separated from dura metter by subdural space (potential space)
subdural arachnoid space = real space w/ CSF and blood vessels
- Arachnoid villi protude into superior sagittal sinus to reabsorb CSF
^allows body to get rid of CSF thats circulating, can calcify as get older
What is Pia matter?
- layer of delicate vascularized connective tissue that clings tightly to brain
*follow bumps and groves
What is CSF
cerebrospinal fluid
- Functions
- give buoyancy to brain
- protects CNS from blows & trauma (think egg in jar of water, only some protection)
- nourishes brain and carries chemical signals
- clears wastes
*lined w/ ependymal cells, wastes and unnecessary solutes are absorbed and getfiltrate with glucose, O2, vitamins and ions (Ca, Cl, Mg etc)
describe the blood filtrate by coroid plexus
Location: ventricles + subarachnoid space
– Produces ~500mL/day
– Constant volume (~125-150ml)
*junk in holes are chorid plexus, helps make CSF
describe the ventricles of the brain
“holes”
- connects to one another and to central canal of psinal chord (tiny hole runs down spinal)
- contains cerebrospinal fluid (CSF)
- lined by ependymal cells
pathway of CSF
What are the ventricesl fo the brain
- Lateral
- lateral so not on midline
- starts at temporal lobes, loop up and around to midline looks like ram horm
- have 2 of them but o not call 1 and 2 bc they are equal
*After lat ventricle CSF goes thru interventricular formaen, that connects lateral and 3rd ven
- 3rd ventricle
- on midline
- looks like bird, head is the ventricle
*CSF goes down cerebral aquaduct, connects 3rd to 4th ventricle
- 4th ventricle
- separates ponds and medulla from cerebrellum
*CSF can then go down central canal, exit through med or lateral apetures (ends up in sub arachnoid space) OR central canal of spinal column
what do subarachnoid villi do
move CSF into dural venous sinuses
Describe the dural venous sinsues
- start with superior sagital sinus (msot superficial margin on falx cerebri) or inferior sagittal sinus
- inferior -> straight sinus *then joins superior sagittal sinus
- both go down transverse sinus (2x -> no longer midline, travel transversely in superficial margin )
- then does to sigmoid sinus (x2)
- sigmoid becomes interanl jugular vein (vein otuside the skull)
*LOOK AT HER VIDEO ON THIS FIGURE PUTS IT ALL TOGETHER
