week 4 Flashcards
T or F: the CNS is our most understood organ system
false – least understood*
T of F: the CNS is mostly composed of neurons
false – 75-90% glial cells
5 types of glial cells
- astrocytes
- ependymal cells
- microglia
- oligodendrocytes
- schwann cells (PNS)
T or F: glial cells are excitable
false – non-excitable
role of astrocytes? (8)
- mop up neurotransmitters from synaptic cleft (ex. glutamate; high amounts = toxic!)
- maintain electrolyte composition of interstitial fluid (esp K+)
- protect neurons from toxins + oxidative stress
- contribute to glutamine synthesis + glycogen storage
- aid development of connections bw nervous and non-nervous tissue (esp baby neurons)
- direct development of special capillaries that contribute to BBB
- communicate to neurons through chem messengers
- possibly modulate synaptic activity
role of microglia? (3)
- work with astrocytes to protect neurons from toxins
- protect CNS via phagocytosis
- protects CNS from oxidative stress
what are the physical supports of the CNS?
- bones (cranium and vertebral column)
- meninges (dura mater, arachnoid matter, pia mater)
where is the sub-arachnoid space? what is its function?
where: between AM and PM
function: shock absorber
what is reticular formation? what do athletes wear to protect the RF?
- RF: loose nerve cells at brainstem that connect brain + behaviour
- athletes wear mouth guards to protect the RF because violent shaking of the jaw causes disruption of the RF.
what is CSF secreted by? what are its functions (2)
- CSF secreted by ependymal cells of choroid plexus (circulates thru ventricles to subarachnoid space and is reabsorbed by arachnoid villi).
- functions: 1) cushion, 2) maintain stable interstitial fluid environment
T or F: ventricles are all connected
true!
{CSF made in choroid plexus and then flows thru lateral ventricles –> third ventricle –> cerebral aqueduct –> fourth ventricle –> central canal –> subarachnoid space… eventually drains into sinuses or veins via villi}
what is a spinal tap?
lumbar puncture to collect CSF (this region has no spinal cord proper, so do here to avoid damage)
what do we mean when we say the CSF is recycled 3 times/day?
that it’s like a cleansing system, ie dead cells/tissues get dumped back into general circulation
why does CNS account for 2% of total body weight yet receive 15% of blood supply?
- brain uses 20% oxygen and 50% of glucose and cannot story glycogen, therefore depends on blood flow for energy
what is the blood-brain barrier? what is it made of?
- physical barrier that exists between the blood and CSF
- made of capillaries which are the actual site of exchange between blood and interstitial fluid
parkinson’s disease is a lack of dopamine resulting in muscle issues, twitching, repetitive movements. why can’t we just inject dopamine?
due to BBB, injecting dopamine will not reach brain. need to inject L-dopa, which DOES cross BBB! converts to dopamine once inside.
diff bw a typical capillary vs brain capillary?
brain capillaries contain tight junctions while typical capillaries have pores
CNS: cluster of neurons = ___ and clusters of myelinated axons = ___.
PNS: cluster of neurons = ___ and clusters of myelinated axons = ___.
CNS: nuclei, tracts
PNS: ganglia, nerves
is grey matter on the outside or inside? white matter?
brain: grey outside, white inside.
spinal cord: grey inside, white outside.
how many pairs of spinal nerves do we have? name them
31…
C1-C8 Cervical
T1-T12 Thoracic
L1-L5 Lumbar
S1-S5 Saccral
C0 Coccygeal
what is a dermatome? what are they useful for?
- sensory region of skin, served by a spinal nerve.
- useful for locating areas of damage.
in the spinal cord, grey matter is divided into functional halves. what are these halves/their functions?
dorsal (facing back) half: sensory functions
ventral (facing stomach) half: motor functions
describe afferent and efferent fibers in the spinal cord
AFFERENT: 1) originate in periphery as sensory receptors. 2) terminate in dorsal horn (cell bodies located in dorsal root ganglia).
EFFERENT: 1) originate in ventral horn. 2) travel to periphery and form synapses with skeletal muscles (their cell bodies are in the spinal cord).
what is referred pain? why does this happen?
- activation of nociceptors in viscera produces pain that has been “referred” to the body surface.
- occurs because second-order neurons that receive input from visceral afferents also receive input from somatic afferents.
