CNS cells, sensory receptors, Nts, vomiting Flashcards
What does Nissl staining stain?
RER
Where is the RER not present (what will not be stained on Nissl staining)?
Axons
What is the astrocyte marker?
GFAP
What is the most common glial cell type in the CNS?
Astrocytes
What are the functions of the astrocyte?
- Physical support
- Repair
- Removal of excess NTs
- Component of BBB
- Glycogen fuel reserve buffer
- Reactive gliosis in response to neural injury
What are astrocytes derived from?
Neuroectoderm
What is the function of microglial cells?
- Phagocytic scavenger cells of the CNS
- Activate in response to tissue damage and release inflammatory mediators (nitric oxide, glutamate)
What are microglial cells derived from?
Mesoderm
What cells fuse to form multinucleated giant cells in the CNS in HIV-associated dementia?
Microglia
What kind of cells are ependymal cells?
Ciliated simple columnar glial cells
What the ependymal cells line?
Ventricles and central canal of spinal cord
What are ependymal cells derived from?
Neuroectoderm
What structure produces CSF?
Chroroid plexus
What is the predominant type of glial cell in white matter?
Oligodendrocyte
What structure covers the individual myelinated nerve fibres?
Endoneurium
What does the perineurium cover?
A fasicle of nerve fibres
What does the epineurium cover?
Entire nerve (fasicles and blood vessels)
What are Nissl bodies?
Collections of RER
What cranial nerves have their myelin synthesised by oligodendrocytes and what CNs have it doen by Schwann cells?
- Oligodendrocytes: CNI and II
- Schwann cells: CN III - XII
What is the Schwann cell marker?
S-100
C fibres are myelinated or unmyelinated?
They are unmyelinated and therefore slow
Free nerve endings sense what?
Pain and temperature
Where can free nerve endings not be found?
- Cartilage
- Eye lenses
What receptors are large, myelinated and adapt quickly?
- Meissner corpuscles
- Pacinian corpuscles
Where are Meissner corpuscles located?
Glabrous (hairless) skin
What receptors are large, myelinated and adapt slowly?
- Merkel discs
- Ruffini corpuscles (intertwined among collagen fiber bundles)
What do Meissner corpuscles sense?
- Fine/light touch
- Skin indentation
- Position sense
- Low frequency vibration
What do Pacinian corpuscles sense?
- Pressure
- High frequency vibration
What do Merkel discs sense?
- Pressure
- Deep static touch (e.g. shapes, edges)
What do Ruffini corpuscles sense?
- Stretch
- Joint angle change
Where are Pacinian corpuscles found?
- Deep skin layers
- Ligaments
- Joints
Where are Merkel discs found?
- Finger tips
- Superficial skin
Where are Ruffini corpuscles found?
- Finger tips
- Joints
What is chromatolysis due to (what is it in reaction to)?
Response of neuronal cell body to axonal injury
What are arachnoid and pia mater derived from?
Neural crest
What is the dura mater derived from?
Mesoderm
Where is the CSF located?
Subarachnoid space (between pia and arachnoid mater)
What substances are able to cross the BBB rapidly?
Nonpolar/lipid-soluble substances
What are the 4 structures which form the BBB?
- Tight junctions between nonfenestrated cpaillary endothelial cells
- BM
- Astrocyte foot processes
- Pericytes
What is chromatolysis characterised by?
- Round cellular swelling
- Displacement of the nucleus to the periphery
- Dispersion of Nissl substances (RER) throughout cytoplasm
What is Wallerian degeneration?
Disintigration of the axon and myelin sheath distal to the site of axonal injury with macrophages removing debris
When the axon is damaged what happens to the axon proximally?
The axon retracts and the cell body spouts new protrosions that grow toward other neurons for potential reinnervation
- Serves as a preperation for axonal regeneration and functional recovery
What NTs are downregulated and upregulated in anxiety?
- NE upregulated
- GABA and serotonin downregulated
What NTs are downregulated in depression?
- NE
- Serotonin
- Dopamine
What NT is upregulated in schizophrenia?
Dopamine
What NT is downregulated in Alzheimer’s disease?
Ach
What Nts are downregulated and uregulated in Huntingtons?
- Dopamine upregulated
- GABA and Ach downregulated
What Nts are downregulated and uregulated in Parkinsons?
- Ach upregulated
- Serotonin and Dopamine downregulated
What organs allow molecules in blood to affect brain function?
Circumventricular organs with fenestrated capillaries - they lack a BBB
Where are the circumventricular organs located?
- Around the third and fourth ventricles
How can hyperosmolar agents (e.g. mannitol) affect the BBB?
Disrupt it allowing for increased permeability of medications
How can neoplasms and infarctation cause vasogenic oedema?
Destroys endothelial tight junctions
What are some of the key Circumventriculat organs (CVOs)
- Area postrema (CTZ)
- OVLT (organum vasculosum lamina terminalis)
- Subfornical organ (SFO)
- Median Eminence of Hypothalamus
Where is the CTZ located?
The area postrema which is at the caudal end of the 4th ventricle
What area do chemo agents affect?
CTZ (in area postrema)
- Sends signals to vomiting centre in medulla
What area of the brain senses osmolarity of the blood?
What area of the brain senses osmolarity of the blood?
OVLT (organum vasculosum lamina terminalis)
- Anterior wall of 3rd ventricle
What structure releases hormones into vascular system to regulate the pituitary?
Median eminence of hypothalamus
What nucleus in the medulla is the vomiting centre coordinated by?
Nucleus tractus solitarius (receives info from CTZ, CNX, vestibular system, CNS)
The CTZ and adjacent vomiting centre nuclei receive input from what 5 major receptors?
- Muscarinic (M1)
- Dopamine (D2)
- Histamine (H1)
- Serotonin (5-HT3)
- Neurokinin (NK-1)
Anatgonists to what receptors are used to treat chemotherapy-induced vomiting?
- 5-HT3 - ondanestron
- D2
- NK-1 - aprepitant
Anatgonists to what receptors are used to treat motion sickness-induced vomiting?
- H1
- M1
Anatgonists to what receptors are used to treat hyperemesis gravidum (vomiting in pregnancy)?
- H1 antagonist
