lecture 9 Flashcards
meninges
-thin membrane located between bone and nervous tissue
3 layers : Dura, arachnoid (weblike) and Pia
Help stabilize nervous tissue and protect it against bones
subarachnoid space
below arachnoid, filled with CSF
meningitis
infection of CSF of subarachnoid space, leads to seizures and loss of consciousness
extensions of the dura mater that seperate part of the brain
falx cerebri, falx cerebelli, tentorium cerebelli
falx cerebri
seperates two sides (hemispheres) of cerebrum
falx cerebelli
fold of dura mater at back of head
tentorium cerebelli
seperates cerebrum (top part) from cerebelum and brain stem
cerebrospinal fluid (CSF)
secreted and contained within the ventricles, sub-arachnoid space (between pia and arachnoid) and central canal in spinal cord
CSF manufactured by the
choroid plexus : made up of capillaries and ependymal cells
ependymal cells
pump Na+ and other solutes into ventricles→concentration gradient→ draws plasma into ventrices by osmosis
flow of CSF
starts in lateral ventricles→ interventricular foramina of Munro →third ventricle→ cerebral aqueduct→fourth ventricle→ median aperture→central canal→ drains from superior sagittal sinus
when there is a back up of CSF, pressure increases in the ventricles which compress brain blood vessels and leads to damage of them
villus
(arachnoid villus)
protrusions of arachnoid mater
arachnoid villus : go through dura mater into sagital sinus
function of CSF
mechanical protection of the brain
- shock absorbtion, buoyancy
- chemical protection of the brain
- contributes to extracellular environment of neurons (high in Na and low in K)
- transport of metabolites, waste products out of the CNS into the venous circulation
what is the only substrate metabolized by the brain
- glucose
- no brain glycogen storage so we need continuous blood supply
- if we reduce blood supply to the brain, then ion pumps will fail and ion membrane gradients decrease on outside
blood supply/ drainage to the brain
→supplied by the internal carotid arteries and the vertebral arteries
→drained by the internal jugular veins
blood brain barrier
final layer of protection of brain, nourishment to brain
formed by : endothelial cells connected by tight junctions
tight junctions controlled by Astrocytes, control what comes in/out and at what rate
tight junction allows brain to selectively import nutrients and energy, while simultaneously excluding neurotoxic substances
plasma membrane
selectively permeable to lipid soluble molecules (Eg. 02, C02, fatty acids, steroids, alcohol, nicotine, some drugs) -can pass through membrane without resistance
some solutes cannot pass through plasma membrane eg. sodium, potassium, glucose, amino acids
facilitated diffusion
- movement of large or charged particles (eg. glucose, amino acids) across membrane
- carrier proteins : binding of target substance initiates change and allows passage of molecule
function of BBB
- maintaining stable neural environment against fluctuations in content of circulating blood (hormones, ions or NT’s)
- chemical protection of the brain
- some areas of CNS where the BBB is “leaky”
concussion
type of tramatic brain injury caused by a bump, blow or jolt to the head, or hit to the body that causes the head and brain to move rapidly back and forth
-creates chemical changes in the brain and sometimes stretching and damaging of brain cells
changes at the neuron during concussion
- stretching of axon
- depolarization
- K+ flux out and Ca+ flux into neuron
- Na/K ATPase pump tries to maintain conc. gradient (requires ATP)
- increased glycolysis to produce ATP →lactate acumulation
- metabolite buildup causes axon sweling
- decreased function
long term
tau proteins stabilize axons
- repeated concussions= increased tau
- buildup of tau overtime is toxic to axon
- leads to neuronal dysfunction and cell death
response to exercise and cold pressor test
exercise : increased HR in concussed people, lower stroke volume so need to compensate with increased HR
cold pressor test : SNS not as activated in concussed individuals
