Last Minute Shit I dont know Flashcards
Which protein initiates expression of primitive steak?
- Nodal
Which protein initiates expression of primitive node??
- HNF-3B
Explain how laterality of the primitive streak occurs
- Serotonin upregulates FGF in left side of streak
- Serotonin is inhibited in right side of steak by MAO
- FGF and LEFTY-2 upregulated PITX2 which establishes left sidedness
What causes ventralising of mesoderm?
- BMP4
What causes dorsalising of mesoderm?
- Antagonism of BMP4
- By expression of Brachyury (T) gene
Outline molecular regulation of invagination
- FGF downregulates E-cadherin
Outline molecular regulation of neurulation
- FGF upregulates chordin and noggin
- Which inhibits BMP
Outline molecular regulation of neural crest cells
- Intermediate levels of BMP
- Upregulates PAX3, SNAIL, FOXD3 which causes neural crest specification
- SLUG promotes neural crest migration
Outline molecular regulation of ventrolateral patterning of nervous system
- Dorsal region: Ectoderm secretes BMP4 which expresses TGF proteins which activates PAX3 and PAX7
- Ventral region: Notochord secretes SHH which activates NKX2.2 and NKX6.1
Outline anteroposterior patterning of nervous system
- Hindbrain: Retinoic acid shifts HOX gene expression anteriorly causing cranial rhombomeres to differentiate into caudal types
- Forebrain/Midbrain: Anterior neural ridge and rhombencephalic isthmus induce LIM1 (prechordal plate) and OTX2 (neural plate) which resulting in expression of FOXG1 (forebrain) and engrailed genes (midbrain)
Explain how the threshold for activation of nociceptors is lowered
- Injured C fibres liberate substance P
- Substance P binds to mast cells and causes histamine release
- Histamine receptors develop on nerve terminals
- Histamine binds to histamine receptors and causes release of arachidonic acid
- The enzyme COX converts arachidonic acid to prostaglandins
- Prostaglandin causes sensitisation of nociceptors
- Manifested as allodynia and hyperalgesia
Outline the lateral pain pathway
- Spinothalamic pathway
- First order neurons from dorsal root ganglion to laminae 1,2 and 4
- Second order neurons from spinal lamina decussate and pass in anterior and lateral fasciculus, which converge as spinal lemniscus, and terminate on VPN
- Third order neurons from VPN to relevant part of somatosensory cortex in postcentral gyrus
Outline the medial pain pathway
- Spinoreticulothalamic pathway
- First order neurons from dorsal root ganglion to laminae 5-7
- Second order neurons from spinal lamina terminate on intralaminar nucleus of thalamus
- Third order neurons from intralaminar nucleus of thalamus to anterior cingulate gyrus
- Which is responsible for affective component of pain
Outline the axon reflex
- Noxious stimulus is transduced
- Axons send impulses in antidromic direction to nociceptive nerve endings
- Which releases substance P which binds to mast cells and causes release of histamine
- Which causes vasodilation (flare) and oedema (wheal)
Outline supraspinal nociception
- Raphespinal tract descends from magnus raphe nucleus
- It terminates on posterior tract of lissauer and terminates on inhibitory internuncials resulting in synaptic inhibition
- MRN is stimulated by periaqueductal grey, which is disinhibited during pain by beta-endorphins
Outline wind-up phenomenon
- Sustained activation of neurones in spinothalamic and spinoreticular tracts by glutamate activating NMDA receptors.
- Repetitive activation of NMDA glutamate receptors
- Gene transcription resulting in additional NMDA receptors on dendrites
- Non-serotonergic neurons acting on magnus raphe nucleus
Outline process of X-rays
- X-ray beams are collimated to appropriate areas
- X-ray beams are attenuated to different degrees by different tissues
- Bone attenuates X-ray beams most, it is exposed to few rays so remains white
- Air attenuates X-ray beams least, it is exposed to most rays so appears black
Outline process of MRI
- Protons in water act as magnet
- Patient placed in magnetic field which aligns magnets
- Radio waves are passed through patient which deflect and emit small radio waves
- Which produce a signal which is passed to a computer to create an image
Outline process of withdrawal syndrome
- Super activation of adenylyl cyclase
- Increase in cAMP and protein kinase A
- Causing phosphorylation of neurotransmitter transporters, which increases neurotransmitter release
Outline the process of drug tolerance
- Activation of intracellular kinases e.g. mitogen-activated protein kinase
- Which phosphorylates and desensitises opioid receptors
Identify 3 drugs that effect pupillary diameter and their mechanism of action
- Phenylephrine: Mydriasis due to a1 agonism
- Tropicamide: Mydriasis due to M3 antagonism
- Pilocarpine: Miosis due to M3 agonism
Identify 3 refractive errors, and the type of lens used to correct each
- Hyperopia, farsightedness due to too short an eyeball, corrected using convex lenses which converge light rays
- Myopia, shortsightedness due to too long an eyeball, corrected using concave lenses which diverge light rays
- Astigmatism, curvature of cornea is different in two different planes so light rays do not come to a focal point, corrected using both a spherical (converges light rays to a focal point) and cylindrical lens (converges light to a focal line)
What is strabismus, what is its cause and how is it treated?
- Misalignment of the two eyes in one or more co-ordinates
- Caused by an abnormal set of the fusion mechanism, one eye focuses satisfactorily while the other does not
- Vision therapy, including eye exercises, or surgert
What is amblyopia and how is it treated?
- Reduction in visual acuity cause which can lead to blindness
- Caused by failure of the two overlapping images from each eye to be sent to the brain, resulting in the visual image being suppressed in one eye
- Patching the non-amblyopic eye with an eye patch, vision therapy