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
Outline the 9 layers of the retina and the cell type associated with each
- Pigmented layer: Vitamin A and melatonin
- Layers of rods and cones
- Outer nuclear layer: cell body of rods and cones
- Outer plexiform layer: horizontal cells
- Inner nuclear layer: bipolar cells
- Inner plexiform layer: amacrine cells
- Ganglionic layer
- Layer of optic nerve fibres
- Inner limiting membrane
Outline the process of phototransduction
- Light focuses on retina
- Conformational change in 11-cis retinal to all-trans retinal, causing it to move away from opsin, which activates rhodopsin
- Activated rhodopsin activates transducin which activates cGMP phosphodiesterase
- Which degrades cGMP, resulting in closure of cationic channels in rod cell membrane
- Causing hyperpolarisation of cell, which results in glutamate release
What is the difference between felt stigma and enacted stigma?
- Felt stigma: change in self-identify categorised by shame, guilt and withdrawal
- Enacted stigma results from societal reactions and may be caused by direct mistreatment (direct enacted) or by rules, systems or procedures (indirect enacted)
What is perception? Identify two types of processing
- Knowledge based and partly learned
- Inferential so we receive the whole person not half
- Categorical meaning we categorise what we mean
- Relational meaning size depends on context
- Adaptive meaning significant things are perceived better than insignificant
- Bottom up processing: comparing features of a stimuli with sets of features existing in the brain
- Top-down processing: people see what they expect to see
Identify which layers of the LGN receive signals from the temporal side of the retina and which receive signals from the nasal side
- Temporal: 2, 3 and 5
- Nasal: 1, 4 and 6
Identify which layers of the LGN receive signals are called magnocellular layers (and why) and which layers are called parvocellular (and why)
- Magnocellular: 1 and 2, large Y cells which are rapidly conducting and conduct black and white
- Parvocellular: 3, 4, 5 and 6 medium sized X cells which transmit colour and accurate spatial information
Describe how different regions of the basilar membrane differ in response to different frequency of sound
- Near round window, basilar fibres are short and stiff and vibrate better at high frequency
- Near helicotrema, basilar fibres are long and loose and vibrate better at low frequency
Describe Webber’s test including the tuning fork used, the procedure and the results
- 512 Hz tuning fork is placed on centre of forehead
- Ask the patient if they can hear it, and if it sounds the same on both sides
- Conductive hearing loss: Sound hear loudest in affected side
- Sensorineural hearing loss: Sound heart loudest in unaffected side
Describe Rinne’s test including the tuning fork used, the procedure and the results
- 512 Hz tuning fork is placed on mastoid process
- Ask the patient if they can hear it and ask them to tell you when they no longer hear it
- When they no longer hear it place the tuning fork near the ear
- Conductive hearing loss: Bone conduction is greater than air conduction (cannot hear tuning fork over ear) Rinne’s negative
- Sensorineural hearing loss: Air conduction is greater than bone conduction, Rinne’s positive, this is a normal finding
Describe the pathways from the two cochlear nuclei. What is the role of the superior olivary nucleus?
- Dorsal cochlear nuclei: Via dorsal acoustic stria to contralateral lateral lemniscus which terminates in contralateral inferior colliculus
- Ventral cochlear nuclei: Via trapezoid body to superior olivary nucleus, and from here via ipsilateral and contralateral lemniscus to contralateral inferior colliculus
- Superior olivary nucleus detects which direction sound is coming from by comparing intensities (lateral SON) and time lag (medial SON)
Describe the structure of the static labyrinth, what it detects and what its function is
- Composed of utricle and saccule and their maculae
- Maculae are horizontal in utricle and vertical and saccule
- Macula composed of supporting cell invested by hair cells which invest into a gelatinous matrix which contains otoconia
- Movement of otoconia causes hair cells to bend in direction of kinocilium with opening of cation channels allowing influx of potassium-rich endolymph
- Threshold is exceeded and an action potential is generated in the vestibular nerve
- Detects linear acceleration in horizontal and vertical planes
- Activates extensor antigravity muscles via the lateral vestibulospinal tract
Describe the structure of the kinetic labyrinth, what it detects and what its function is
- Composed of three semicircular canals and their cristae
- Cristae composed of supporting cells invested by hair cells which invest into a gelatinous matrix called the cupula
- Movement of the head pushes the cupula against the stationary endolymph
- This causes hair cells to bend in direction of kinocilium with opening of cation channels allowing influx of potassium-rich endolymph
- Threshold is exceeded and an action potential is generated in the vestibular nerve
- Detects angular acceleration of the head
- Activates the vestibulo-ocular reflex, activation of the ipsilateral oculomotor and contralateral abducens nuclei
- To cause eye movements that are equal and opposite the movement of the head to keep the gazed fixed
Describe the symptoms of BPPV, how it is diagnosed and how it is treated
- Vertigo lasting seconds to minutes which is precipitated by head movement
- Diagnosed using Hallpike manoeuvre
- Treated using Epley manoeuvre
Describe the symptoms of Meniere’s disease, how it is diagnosed and how it is treated
- Vertigo last minutes to hours
- Classically associated with low frequency sensorineural hearing loss, feeling of fullness in affected ear, loss of balance, tinnitus and vomiting
- Treated using a low-salt diet, betahistine, cinnarizine (H1 agonist, an antiemetic drug) and chemical labyrinthectomy using gentamicin
Describe the process of language development including developmental milestones
- Children discriminate sounds that correspond to phonemes (the sound produced by each letter)
- At 1 children begin to speak
- At 1-2 children speak about people, animals and body parts
- At 1.5-2.5 they begin acquiring phrases and using sentences
- Critical period for language development is between 4 and 12
Outline Piaget’s theory of cognitive development
- Sensorimotor, 0-2, trial and error, experimentation
- Preoperational, 2-7, imagination and memory
- Concrete operational, 7-12, logical thought
- Formal operation, 12-18, abstract thought
Describe the innervation of the hypoglossal and facial nerves and the lesions associated with them
- Hypoglossal nerve is contralaterally innervated resulting in deviation of tongue to affected side (unilateral lesion) or global wasting (bilateral lesion)
- Upper part of facial nerve is bilaterally innervated and lower part is contralaterally innervated. Unilateral upper motor neuron lesion causes sparing of muscles above eyes, but lower motor neuron does not (Bell’s palsy)
Outline the pathology of ischaemic stroke and reperfusion injury
- Reduced blood flow results in anaerobic respiration
- Which causes results in acidosis due to accumulation of lactate
- Failure of energy-dependent pumps results in calcium influx via glutamate channels resulting in activation of destructive enzymes and destruction of organelles
- When blood flow returns there is activation of oxygen-free radical systems
Outline the pathology of a TIA, and three clinical features of a TIA in the anterior and posterior circulation
- Ischaemia without infarction
- Anterior: Amaurosis fugax, hemiparesis, aphasia
- Posterior: Diplopia, vertigo, vomiting
Outline the pathology, investigations, clinical features and treatment of a cerebral infarction
- Typically caused by infarction in internal capsule
- MRI shows ischaemic penumbra around site of lesion
- Features include contralateral hemiparesis, and aphasia lasting over 24 hours or to death
Identify four signs of a brainstem infarction
- Lateral medullary syndrome (Wallenberg’s syndrome) presenting with acute vertigo and cerebellar signs
- Coma
- Locked in syndrome
- Pseudobulbar palsy
What is lacunar infarction?
- Symptomless infarction associated with hypertension
- Small infarcts seen on MRI
What is hypertensive encephalopathy?
- Cerebral oedema causing headaches, nausea and vomiting
- MRI shows oedematous white matter