unit 2: CNS Flashcards
STUDY
development of the human CNS:
4 weeks:
6 weeks:
11 weeks:
birth:
4 weeks:
- anterior neural tube - > fore, mid and hindbrain
- spinal cord
6 weeks:
- Hindbrain -> Medulla oblongata, Cerebellum, Pons
- Forebrain -> Diencephalon, Cerebrum
- spinal cord
11 weeks:
- Growth of cerebrum rapid
Birth:
- Cerebrum cover most of other brain region
what is the reason why we believe the spinal cord to be hollow?
because the central canal is hollow and filled with cerebrospinal fluid
what are the meninges layers?
inner layer: PIA MATER
middle layer: ARACHNOID MEMBRANE
dura matter: DURA MATER
TRUE OR FALSE?
between the meninges layer there is free space
false, its filled with cerebrospinal fluid
Protection and support for CNS (brain, spinal cord)
Bony cage: cranium, vertebrae
3 Layers of connective tissue - meninges
Fluid between layers - cerebrospinal fluid
dura mater is?
outer most layer, how to remember? its something tough and DURAble which is something that is usually located on the outside
true or false?
the arachnoid space is very vascularized?
true
how to remember the arachnoid layer of the meninges
arachnophobia is being scared of spiders and the arachnoid space looks like a spider web
true or false?
the PIA MATER is flat
false, it the brain flat, no? and the inner most layer surrounds the brain so it needs to follow the brains groves as well
(it follows all the groves around the brain)
what do you call a broken blood vessel underneath the dura and coming into the arachnoid area
subdural hematoma
common in elderly
Evolutionary trend in nervous system
nerve net, nerve cord, primitive brain
Ventricles
hollow (CSF-filled) central canal
- 2 lateral, 2 descending into spinal cord
what cells determine the composition of the CSF?
ependymal cells
_______ cells create barrier between compartments
ependymal cells
each ventricle has ___________ ___________
choroid plexus
the choroid plexus produces _______
CSF (cerebrospinal fluid)
purpose of arachnoid villi
helps with the removal of CSF from the subarachnoid space via the dural sinus
the dural sinus allows _______ to get out of the CNS
CSF
what does intestinal fluid, plasma and CSF have in common
all are in the CNS
plasma vs CSF
- what has higher K+, Ca2+, HCO3-, glucose, pH
- higher Na+
- very low protein and no blood cells
- plasma
- none of them they have similar Na+
- CSF
how many times is CSF removed and replaced and why?
4x a day
cleans out metabolites and toxins
- together the choroid plexuses produce how much CSF fluid a day?
- how man choroid plexuses are there
- 500 ml a day
- there are three
- lateral ventricle choroid plexus
- third ventricle choroid plexus
- fourth ventricle choroid plexus
explain the process of removing CSF from the brain (choroid plexuses).
- near the 4th ventricle the CSF can leave via some opening and enter subarachnoid space
- its past the inner most layer and is now in the middle of the meninges. CSF travels around the space and can leave the space via the ARACHNOID VILLI.
- these villi allow the CSF to travel to the outer most layer, the dura mater and CSF is able to leave via the dura sinus (venous)
what is another name for DURAL SINUS
superior sagittal sinus
circulation of CNS:
________ –> ________ –> ___________ –> __________ or ________ –> __________ –> ___________.
lateral ventricles (2) –> third ventricle –> fourth ventricle –> central canal of spinal cord or subarachnoid space –> superior sagittal sinus (dural sinus) via arachnoid villi –> venous return to heart.
true or false?
- the ventricles within the CNS that contain CSF are very narrow and if they get further narrowed it can result in pressure build up and press on brain tissue
- what are some examples of added pressure?
- true
- bleeds, tumours, anything causing added pressure
difference between hydrocephalic vs a normal brain
with hydrocephalic,
- ventricles become huge because of fluid build up
- brain becomes compressed
2 functions of CSF
- Chemical protection - maintains extracellular environment for neuron’s (cleans out metabolites + toxins)
- Physical protection
- protects the brain from hitting the cranium/skull, allows CNS tissues to float which relieves pressure on blood vessels + nerves attached to the CNS
Special features of cerebral vasculature
tight junctions: so that there is great control over what can and can- not enter (selectively permeable barrier)
Astrocyte foot processes: secrete paracrine signals to en- sure the cells remain tightly joined.