-
layers of median eminence
- third ventricle
- ependymal layer: tanycytes (astrocytes)
- internal layer: axons of hypothalamohypophyseal tract from paraventricular, median supraoptic tracts
- external layer: nerve terminals of neurosecretory neurons
- perivascular layer: tissue into which hypophyseal hormones are released before entering hypophyseal portal system (superior hypophyseal artery, branch of posterior communicating)
-
hypophyseal portal system
- superior hypophyseal artery: supplies primary capillary network in pituitary stalk, median eminence
- long hypophyseal portal veins: connect it to secondary capillary network within adenohypophysis
-
intermediate lobe of pituitary
- pars intermedia
- colloid follicles
- produce POMC (ACTH precursor)
-
ddx short stature
- normal height variation
- pituitary dwarfism
- in utero effects
- emotional deprivation
- chronic disease
- drug effects e.g. asthma
- malnutrition
-
in utero growth effects
- largely independent of fetal and maternal hormones
- O2/nutrient supply from placenta
- intrauterine infections
- toxins
- genetic factors
- IGF1/2
- influence on later growth, metabolism
-
growth mechanisms by phase
- in utero and infancy: in utero conditions
- childhood: GH
- puberty: GH, sex hormones
-
average height difference adult male and female
12.6cm
-
ddx acromegaly
- 1. pituitary tumour
- 2. hypothalamus tumour
- 3. small cell lung ca
-
GH workup
- 1. igf1
- 2 gh suppression test
-
embryonic establishment of CNS
- week 3: gastrulation forming trilaminar disc
- week 4: neurulation - differentiation of ectoderm to form neural plate; embryonic folding and neural folding to form neural tube
- neural tube: CNS and brain
- neural crest (peripheries): PNS
-
neural tube defects
- failure of neuropore to close during neural folding
- day 26: closure anterior neuropore (anencephaly, encephalocele)
- day 28: closure posterior neuropore (spina bifida)
-
RDI folate
- 400 micrograms per day
- more if: clomifene, carbemazepine, DM1, obese, fam hx NTD
-
long term potentiation
- model for associative conditioning aka learning and memory
- summation of EPSP overtime to reach threshold for LTP causing insertion of more AMPA receptors and splitting or membranes, formation of new synapses
- increased excitatory response for same stimulus
-
GBS
- AI demyelination usually following infection
- rapidly ascending symmetrical weakness in CST and CBT
- dx by antibody testing
- tx IV Ig
-
ALS
most commonly LMN degeneration
-
factors affecting resting tone
- muscle structure and tissue properties
- tonic activity in stretch reflex arc
- incomplete relaxation
-
neurogenic atrophy
- aka denervation atrophy, seen in LMN
- successive renervation of larger groups of muscle fibres as LMNs degenerate
- eventual death and atrophy of myocytes by proteolysis
-
tectospinal tract
- superior colliculus
- directs rapid orientation towards moving objects (tracking)
-
reticulospinal tract
- reticular formation
- consciousness and successful locomotion
-
vestibulospinal tract
- vestibular nuclei
- head position and acceleration
-
dopamine pathways
- nigrostriatal: substantia nigra to striatum for disinhibitory modulation (reduced in Parkinsons)
- mesolimbic: ventral tegmental area to nucleus accumbens (pleasure pathway thought to be overactive in psychosis)
- mesocortical: ventral tegmental area to prefrontal cortex (executive functioning)
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