CNS 2 Flashcards
the brain is protected from injury by…
- the skull
- the meninges
- the blood brain barrier
- the cerebrospinal fluid
the 3 layers of membranous connective tissue, the meninges provide what?
support + protection
what are the 3 layers the meninges is composed of?
- dura mater
- arachnoid layer
- pia mater
what are the main functions of the meninges?
- protecting brain + spinal cord from mechanical injury
- providing blood supply to skull + to hemispheres
- providing space for flow of cerebrospinal fluid
what is the blood brain barrier (BBB)?
highly selective semi-permeable membrane barrier that separates circulating blood from brain and extracellular fluid in CNS
what does the BBB tightly regulate?
movement of molecules, ions + cells between blood and CNS
what does the BBB prevent?
large molecules, immune cells, + disease-causing organisms e.g. bacteria + viruses from passing from blood stream into CNS
the BBB is a tightly packed layer of cells that…
line blood vessels in brain + spinal cord
the BBB is composed of 3 cellular elements of the brain microvasculature
what are they?
- endothelial cells
- astrocytes (astroglia)
- pericytes
endothelial cells
= thin layer of cells that line interior surface of all blood vessels
astrocytes (astoglia)
tightly encircle endothelial cells + = critical for induction + maintenance of tight junction barrier (TJs)
what do TJs between the cerebral endothelial cells form?
diffusion barrier which selectively excludes most blood-borne substances from entering the brain
pericytes
= mural cells of microcirculation that wrap round endothelial cells that line capillaries
pericytes help endothelial cells to differentiate, multiply, form vascular branches + survive apoptotic signals
neurological disorders linked to BBB
extrinsic factors?
- multiple sclerosis: autoimmune, infectious, traumatic initiation
- meningitis: bacterial + viral
- encephalitis: herpes, HIV
neurological disorders linked to BBB
intrinsic factors - acute?
- ischemia/hypoxia
- traumatic brain injury
neurological disorders linked to BBB
intrinsic factors - chronic?
- small vessel disease
- amyloid angiopathy (disease of blood vessels)
what is the ventricular system?
set of structures containing cerebrospinal fluid in brain
is continuous with central canal of spinal cord
what is the CSF produced by?
modified ependymal cells of choroid plexus
the CSF has 4 main purposes
what are they?
- buoyancy - supports brain against gravity
- protection - protects brain from striking cranium when head jalted
- chemical stability
- waste removal - removes waste in absence of lymphatic system
the brain and CSF are similar density
what does this make the brain do?
float in neutral buoyancy suspended in CSF
without oxygen and important nutrients, what would happen to brain cells?
damaged/ die in few mins
the brain relies on 2 sets of major arteries for its blood supply
what are they?
- internal carotid arteries (supply anterior brain)
- vertebral arteries (supply brainstem + posterior brain)
what does cerebrovascular refer to?
blood flow in brain
what do cerebrovascular diseases include (CVDs)?
all disorders in which area of brain = temporarily / permanently affected by ischemia/ bleeding
what are the 4 most common CVDs?
- stroke - part of brain damaged by lack of blood supply/bleeding into brain from burst blood vessel
- transient ischemic attack - temp fall in blood supply to one part of brain
- subarachnoid hemorrhage - type of stroke where blood leaks out brains vessels onto surface of brain
- vascular dementia - persistent impairment in mental ability resulting from stroke / other prob with blood circulation to brain
