Lecture 22 Flashcards
__ neurons in the sleep cycle
thalamocortical
the control of sleep and wakefulness depends on the __ modulation of the __ and the __
brainstem; thalamus and cortex
hypothalamus provides modulatory input to the __, which then acts on the __ (__ connections)
brainstem; thalamus; cortex
thalamocortical neurons exist in two states
asleep (bursting/oscillatory) and awake (tonically active)
the tonically active state occurs when the thalamocortical neurons are __
depolarized
tonically active state: information is transmitted to the cortex in a __ fashion - __
asynchronous; encoding peripheral stimuli
bursting/oscillatory state: activity between __ and __ becomes __ (as in the sleep state)
thalamus and cortex; synchronous
modulation of the thalamocortical loops generates eeg __
signatures of sleep
henry head experiment
he cut his own radial nerve to determine the extent of the regenerative capabilities of the PNS, and the area of insensitivity decreases (regeneration)
henry head results
after 6-13 weeks, return of general sensitivity (protophathic abilities); epicritic abilities (fine motor, pin prick, 2 point dicsrimination, light touch) returned more slowly (>2 years
what do the henry head results suggest?
a difference in recuperative abilities of different dorsal root ganglion and spinal motor neurons (some recovered quickly, some did not)
acute axonal degeneration: (3)
axonal skeleton disintegrates, axonal membrane breaks apart (blebbing/swelling), myelin sheath breaks apart
acute axonal degeneration occurs rapidly (axons breaks apart in a day, sheath is degraded within 2-3 days) in __, and slowly (axons take days, myelin sheath takes months) in __
the PNS; the CNS
acute axonal degeneration is caused by local increases in __ that occur __, and activate __ which begin axon fragmentation
Ca; after injury; proteases (Calpain)
severing the axon prevents __
trafficking
in an injured axon, __ can no longer make it to the __ portion of the axon. and axon can no longer maintain appropriate levels of __ so __ get overwhelmed and ER releases __
NMNAT2; distal; Ca; mitochondria; internal Ca stores
Ca activates __ pathways
death
repair and regenration: in the PNS, schwann cells __ (2), and macrophages are __ cells that __
do the initial clean-up and recruit macrophages; immune; take several days to clean up the debris
both schwann cells and macrophages secrete molecules essential for __
successful regeneration
schwann cells secrete signaling molecules (__ 3) into the __ to guide regeneration
laminin, fibronectin, collagens; extracellular matrix
regenerating axons express __ which mediate recognition of the matrix and mediate __ and facilitate __
integrins; intracellular signaling; growth
integrins are a family of receptor molecules found on __ that bind to __ such as laminin
growth cones; cell adhesion molecules
integrins work alongside other receptors such as cadherins, which are a family of __ found on the surface of __
calcium-dependent cell adhesion molecules; growth cones or cells over which they grow
the extracellular matrix, defined by the __, provides a conduit for the regenerating axon
schwann cell processes
Wallerian degeneration
macrophages eating myelin sheath slowly
in response to schwann cell actions, regenerating peripheral neurons change __ and __ to accommodate regrowth
gene expression; protein trafficking
in response to schwann cell actions, __ and __ change back to growth state
actin and microtubule cytoskeleton
regenerative properties of schwann cells are so strong they can be used to repair the __
CNS
axons from a crushed optic nerve can travel through a __ to reach targets in the brain
peripheral nerve graft
axon guidance is mediated by __ and __
chemoattraction and chemorepulsion
__ guide the growing axon and rely on __ (molecular cues) to direct the growing axons to the right direction
growth cones; axon guidance molecules
growth cones are dependent on __
receptors and concentration gradients of molecular cues
after denervation, original NMJ synpatic sites __
remain (in the absence of the synapse itself) for weeks
synaptic sites and nearby schwann cells secrete __ (__ 2) near the site of the __
guidance cues (neurotropins (NGF, etc.) and target adhesion molecules); denervated motor end plate
__ (2) signaling is necessary to recapitulate target recognitions and synaptogenesis
tropic and trophic
there is imprecision in re-innervation: __ (much of which is eventually eliminated)
polyneuronal innervation
activity-dependent processes: __
polyneuronal innervation
also need activity-dependent refinement to eliminate __
aberrant synapses
once synaptic connections are established, neurons become dependent on their targets for their __ (2) = __
survival; continued growth and differentiation; trophic interaction
trophic interaction is controlled by __ = molecules provided by target cells that regulate __ and __ of nearby cells
neurotrophic factors; growth differentiation and survival
if there is a surplus of neurons born, __
fewer make connections
neurons that fail to __ are eliminated
connect with appropriate targets
NGF is an important
neurotropin
the ability for the brain to repair itself is __, the damaged brain does not produce __
limited; large numbers of new neurons
3 barriers to CNS repair
neuronal death, glia cells actively inhibit axon growth, few neural stem cells with limited abilities for growth and differentiation
glial cells actively __ in the CNS
inhibit axon regeneration
brain injury causes __ of glial precursors
local proliferation
glial scar is when __
glia infiltrate the site of injury and persist
regeneration is blocked for 3 reasons
glia scar is a physical barrier, astrocytes and oligodendrocytes secrete molecules that inhibit axon growth, and ECM lacks developmental adhesion molecules
molecules that inhibit axon growth (secreted by astrocytes or oligos)
epherins, semphorins, slit, and NogoA
in the adult brain, neurogenesis occurs __
in select areas
2 areas with high levels of neurogenesis in adult brain
olfactory bulb and hippocampus
new nerve cells are primarily __
interneurons
progeny of neuronal stem cells - close to the surface of the __
lateral ventricle (subventricular zone)
most new nerve cells __
die before they are integrated
