week 2 Flashcards
activation of c fibres gives off what pain?
dull aching pain
what pain is characterised by a high threshold and limited duration?
nociceptive pain - mediated by A delta and C fibres
what is chronic (maladadaptive pain)?
either evoked or spontaneous
A sustained sensory abnormality
comes with hyperalagesia and allodynia
after ebing scratched , what appears?
red reaction, wheal (white area) and flare
when u damage the skin what happens
free nerve endings activated by release of K ions and prostagandins . bRradykinin and 5 -HT is released and activates themand
Substance P and CGRP are also released and they activate mast cells that release histamine.
what does CGRP do?
dilation of blood vessels , more blood flowing to blood vessels and that makes the skin appear red.
consequence of substance P?
can result in oedema , tissue fluid buildup plasma extravasation and release of bradykinin
into the dorsal roots and bifurcate to where
one bracnch goes to dorsal columngracile nucleus-> internal acuate ….
and the little branch into dorsal horn
in the spinothalamic pathway , wherdoes the nerve cross over to from dorsal horn?
anterolateral funiculus
supraspinal system does what?
in build system to help modulate pain input.
gate control theory of pain ?
c fibres activated - projecting into dorsal horn of spinal cord, release glutamate to send of 2nd neuron.
when you rub your hand u activate the A beta pathways sends action potwntials to sensory cortex via DC -ML .
An inhibitory neuron is activated to decrease pain.
What happens when the BBB breaks down ?
Hypertension …
Agonist?
Activates a receptor , toproduces a functional response
Binds to receptor without activating it - blocking the action of the agonists ?
Antagonist
Examples of anaesthesia
Halothane isoflurane (gases - inhalation)
Propofol(IV)
Act on neurotransmitter receptors especially gaba a receptor
Drugs that cause sleep and reduce anxiety?
Sedatives
Anxiolytics
- Barbiturates
- Benzodiazepines
Examples of antipsychotic drugs ?
Typical - chloromazine
Atypical - Clozapine
Examples of anti depressants
Phenelzine - monoamine oxidase inhib
SSRIs - fluoxetine
Tricyclic antidepress - imipramine
Ketamine - rapid onset
Example of analgesic drugs
Opiates
Baclofen - gaba b receptor agonist
NSAIDs
Cognition enhancers
Galantamine - ACh E inhibitors
Improve memory
dopamine synthesising cells are located where and what makes it black?
Melanin
Substantia nigra
Diminished substantia nigra is seen in what disease?
Parkinson’s
Causes of Parkinson’s
Degeneration of the Nigrostriatal DA pathway
Aging
Genetic factors
- synuclein
Environmental factors
- herbicides , pesticides
Therapies aimed to enhance dopaminergic pathways ?
Boosts d
what does dura contain?
large blood vessels, have to consider with trauma to the head
what does the pia mater fuse with
fuses with the ependyma to form choroid plexus
what mater develops first?
pia mater - dy24
dura develops when?
day 45
arachnoid mater develops?
day 57
where does the CSF go?
4 ventricles and subarachnoid space , cisterns , sulci and central canal of SC
what does CSF do?
brain wont compress on the cranial nerves as it allows the brain to float
what is a ependyma ?
roof plate of the myelencephalon consists of a single layer of ependymal cells covered by pia mater .
it is the thin epithelium like lining of the brain and the central canal of the SC .
Ependyma is involved in the production of CSF .
why is there obstruction of the foramen magnum by the cerebellum in SB cystica?
A chiari maformation , is where the cerrebellum pushes down in the spinal canal. range of severity 1 to 4.
1 -headache , neck pain
2 - hydrocephalus and SBC (bag of cyst with nerves protruding out)
defect in mesoderm in type 1
defect in neuroectoderm in type 2
characteristics of chiari malformation type 2
a small post fossa and cranial vault
due to failure of fusion at the craniocervical junction
results in enlargement of the foramen magnum , stretching the fourth ventricle and aqueduct
also have lumbar myelomeningocoele and associated issues with this.
treatment includes decompression
what is insensate skin?
This condition, called insensate skin, means that you may not feel pain, touch, or respond to heat or cold on the area of skin below the level of your lesion.
when does alar and basal plate form?
week 5-6
when do dorsal and ventral horns form?
week 8-9
how and where do the primary brain vesicles form?
the brain vesicles arise from the neural tube . once the tube has formed and closed , the anterior portion expands quicker than the posterior forming the brain vesicles
then they differentiate to give secondary brain vesicles
the remainder of the neural tube becomes the spinal cord.
what is an epithlialto mesenchymal transition ?
epithelial cells lose their adhesive properties
become migratory(more mesenchymal)
process involved in; neural tube formation, wound healing and initiation of metastasis .
characterised by Cadherin expression :
- epithelial cells express high high E-cadherin
- mesenchymal cells express high N-cadherin
what are the two main flexures ?
The cephalic flexure is the first, it pushes the forebrain in a ventral direction. It bends in the midbrain region
Then a second flexure occurs at the junction of the metencephalon and the spinal cord – cervical flexure
what is the lens of the eye made of?
The cells of the lens are epithelial. These epithelial cells are the progenitors for the lens fibres.
Lens fibres are long thin transparent cells which lie underneath the epithelium
The lens has a high protein content - crystallins
when does eye developmet begin?
day 22 as a pair of shallow grooves (optic vesicles)
what are optic vesicles ?
Optic vesicles are in contact with surface ectoderm and induce changes necessary for lens formation
what happens to placodes
Placode cells become columnar and invaginate
how is the choroid fissure formed?
grooves arise on the ventral surface of the optic cup forming the choroidal fissure
blood supply to the developing eye?
A branch of the opthalmic artery - the hyaloid artery passes along the choroidal fissure to supply the lens and developing retina.
what is the optic cup?
Bilaminar structure
Outer layer forms the pigmented layer of the retina
Inner layer forms the nervous layer of the retina
Space between layers disappears as axons grow from the optic nerve
how is the retina formed?
The retina is formed by two layers of the optic cup.
The outer layer forms the pigmented layer of the retina
The inner (sometimes called neural) layer proliferates to form the rods and cones and the cell bodies of neurons.
what gives rise to the ciliary body and iris ?
at the rim of the optic cup , both layers of the retina give rise to ciliary body and iris ?
what does the ciliary body produce?
aqueous humour
what is the lens derived from’?
surface ectoderm.
how does the lens develop?
cells of the lens vesicle elongate anteriorly to form long lens fibres.
they arrange in a laminar pattern to form a transparent lens.
what are the steps to optic nerve development ?
- optic cup connected to brain by optic stalk
- hyaloid vessels in choroid fissure - inner and outer layers fuse. cavity of the stalk disappears
- inner layer cells provide a network of neuroglia that support the optic nerve fibres - optic stalk becomes optic nerve
- hyaloid artery and vein become central artery and vein of the retina.
formation of the eyeball?
The mesenchyme around the optic cup condenses to form the layers of the eyeball, the choroid and sclera.
what becomes the anterior chamber of the eye?
Spaces that develop in the mesenchyme between the cornea and lens
what forms the vitreous body - posterior chamber?
Fibrous tissue with a gelatinous substance fills the gap between the lens and the retina,
formation of the eyelids?
Folds of ectoderm with mesenchyme between them that grow over the cornea.
Fuse and enclose a conjunctival sac anterior to the cornea.
Inner layer of ectoderm becomes the conjunctiva and over the iris, it fuses with the cornea.
Lacrimal glands form as ectodermal buds from the upper conjunctival sac into the surrounding mesoderm.
when do the eyelids seperate again?
Eyelids separate again between the 5th and 7th month in utero.
what is the key regulatory molecule for eye development?
PAX6 – key regulatory molecule
Expressed in anterior neural plate before neurulation begins
what is SHH responsible for?
SHH – signalling molecule responsible for eye field separation
SHH upregulates PAX 2 in optic stalks and restricts PAX 6 to the optic cup and lens
eye abnormalities?
Congenital cataracts: genetic causes, rubella infection between 4-7 weeks of gestation
Microphtalmia: Eye is too small – results from genetic abnormalities / intrauterine infections / foetal alcohol syndrome
Anophtalmia: absence of eye – genetic/infection
Cyclopia (single eye)- failure of the prosencephalon to divide the orbits of the eye
Mutations in SHH
what does the CNS originate from?
ectoderm
when does the neural folds approach each other to fuse the neural tube ?
close by d 28
what controls folding?
hinge points
Neural crest cells migrate to give rise to?
Ganglia, Schwann cells, Adrenal Medulla, Melanocytes
what is SB and anencaphaly caused by?
failure of Neural tube to clse
in the SC what does the basal plate contain?
contains motor neurons
in the SC what does the alar plate contain?
contains sensory neurons
in the SC what does the roof and floor plate do?
connect the two sides - alar and basal
what is the motor nuclei?
is the basal plate inside the cord
what is the sensory cell bodies ?
spinal ganglia from neural crest cells outside the cord
what week does the brain have 3 vesicles ? and what are the three vesicles?
prosencephalon
mesencephalon
rhombencephalon
week 3
what week does the brain have 5 vesicles ? and what are the 5 vesicles?
Telencephalon,
diencephalon,
mesencephalon, metencephalon, myelencephalon
week 5
By the end of development, the ectoderm gives rise to?
the central nervous system
the peripheral nervous system
the sensory epithelium of the ear, nose and eye
the epidermis, hair and nails
the subcutaneous, mammary and pituitary gland
the enamel of teeth
what causes the neural plate to form?
Appearance of the notochord and mesoderm induces the overlying ectoderm to thicken and form the neural plate
what is the initial event in the process of neurulation ?
cells of the plate make up the neuroectoderm and this is the initial event in the process of neurulation
where do glial cells come from?
glia blasts are formed from neuropithelial layer in the mantle and marginal layers .
what do protoplasmic astrocytes and fibrillar atrocytes do?
they are between blood bessels and neurons and support metabolic functions
what do oligodendroglial cells do?
forms myelin sheaths around axons in the marginal layers
microglial cells from vascular mesenchymal are what?
phagocytic cells
Which molecule is instrumental in causing induction of the neural plate?
Upregulation of FGF, inhibition of BMP-4
chordin and noffin expressed
neural plate switched from E-cadherin to N-cadherin expression.
Which of the following brain vesicles does the thalamus arise from?
Diencephalon Mesencephalon Metenchephalon Myelencephalon Telencephalon
Diencephalon
Which structure separates the alar and basal plates of the spinal cord?
sulcus limitans
The dorsal roots of all spinal nerves contain which of the following?
sensory neuronal processes
what do motorneurons synapse on and what transmitter do they use
synapse on skeletal muscle fibres at the neuromuscular junction , they are cholinergic neurons so they use acetyl choline as a transmitter
what does the transverse process articulate with
costal facet of the rib
what does the superior articular facet articulate with
with the inferior articular facet of vertebrae above
what are the characteristic features of the cervical vertbra
- Foramen transversarium
- Bifid dorsal spine
- Small body
- Large vertebral canal
characteristics of lumar vertebra
Large body • Small vertebral canal • Small transverse process without facets • Orientation of articular facets
what is a reflex?
an involuntary stereotyped response to a stimulus
what are tendon jerks
reflex muscle contractions produced by muscle stretch
what is holmes-adie syndrome?
when tendon jerk reflexes are absent
stocking glove pattern of sensory loss is characteristic of …
polyneuropathies
tendon jerk reflex is modulated by what?
activity in descending systems
what would happen to muscle tone in conditions such as stroke , SCI basal ganglia disorder?
spasticity which is accompanied by exaggerated tendon jerk reflexes (hyperreflexia)
methods of non invasive brain stimulation
transcranial electrical stimulation and transcranial magnetic stimulation
A disorder in which of the main dopaminergic pathways in the CNS is implicated in schizophrenia?
mesolimbic/ mesocortical
