Phase 1 Neuro Flashcards
5 vesicles of neural tube and what they become
From initial prosencephalon:
Telencephalon - cerebral hemispheres
Dienchephalon - thalamus
From initial mesencephalon -> midbrain
From initial rhomboencephalon
Metencephalon -> Pons and Cerebellum
Myelencephalon -> Medulla oblongata
In neural tube, what is ventral and what is dorsal in terms of sensory and motor?
Ventral - basal plate: Motor
Doral - alar plate: Sensory
The neural tube sometimes doesn’t close. What are the consequences cranially and caudally?
Cranially - anencephaly
Caudally - spina bifida
What are the types of spina bifida?
Oculta - Missing vertebral arch. no herniation of meninges/spinal chord. May have a patch of hair or dimple as only sign
Meningocoele - meninges (but not nerves), herniate.
Myelomeningocoele - spinal chord AND meninges herniate. Neurological signs present - e.g. paralysis below site/urinary/bowel incontinence.
Describe initiation of development of nervous system in utero
Notochord signals
Ectoderm starts to fold at cervical region and folding continues both ways
If problems, raised maternal alpha foetoprotein + USS
What is hydrocephalus?
Accumulation of CSF in brain because blockage
Neural crest cells migration - disorders?
Hirschsprung’s Disease (Aganglionic megacolon). Constipation.
DiGeorge
Thyroid problems, Thymus hence immune problems, Cardiac problems, Cleft palate
“CATCH-22”
Cardiac abnormality (commonly interrupted aortic arch, truncus arteriosus and tetralogy of Fallot) Abnormal facies Thymic aplasia Cleft palate Hypocalcemia/hypoparathyroidism
Layers of brain meninges: Outer to inner. Start from outside and cover SCALP.
Skin Connective tissue Aponeurosis Loose connective tissue Pericranium
Skull
Periosteal dura mater (flush with bone)
Meningeal dura mater (flush with ^ except certain parts where dural venous sinuses are)
Arachnoid mater (flush with ^, potential space only).
Subarachnoid space (with CSF)
Pia mater (tender mother) - flush with the brain. Chemical barrier.
Where do the dural venous sinuses drain?
Internal Jugular Vein
Ventricular system. Go.
CSF produced in chorioid plexuses. Mostly lateral ventricles -> Third Ventricle (squashed b/w thalami) -> cerebral aqueduct -> 4th ventricle -> Spinal canal.
Blockage anywhere causes proximal swelling. Hydrocephalus.
Purposes of CSF
Fluid buffer
Glucose
Cushioning
What pertinent anatomical landmark of the temporal lobe is important in ICP?
Uncus
Herniates and squashes breathy bits
Important nuclei in basal ganglia
Caudate (side of the lateral ventricle) and Lentiform (kind of triangular thing). Outer edge is the putamen, and inner is the globus pallidus.
Between the lentiform and thalamus is the internal capsule.
AMINO ACIDS
neurotransmitters
AMINO ACIDS
glutamate, GABA, glycine
BIOGENIC AMINES
neurotransmitters
BIOGENIC AMINES
acetylcholine, noradrenalin dopamine, serotonin (5-HT), histamine,
Peptide neurotransmitters
dynorphin, enkephalins, substance P, somatostatin cholecystokinin neuropeptide Y
Excitatory neurotransmitters
excitatory amino acids
– mainly glutamate
– majorexcitatoryneurotransmitter
• over 70% of all CNS synapses are glutamatergic • presentthroughouttheCNS
Inhibit neurotransmitters
• inhibitory amino acids – GABA
– Glycine
Why are NMDA receptors important for Long term potentiation
Glutamate receptors have an important role in learning and memory
– Activation of NMDA receptors (and mGluRs) can up-regulate AMPA receptors – Strong, high frequency stimulation causes long term potentiation (LTP)
– Ca2+ entry through NMDA receptors important for induction of LTP
GABA
Glycine
Mostly where
GABA brain
Glycine brainstem/spinal chord
alzheimers
Degeneration of cholinergic neurones in the nucleus basalis is associated with Alzheimer’s disease
What are the dopamine pathways in the brain and what are they involved with?
Mesocortical (mood)
Mesolimbic (Schizophrenia when too much dopa here, Amphetamines also increase dopamine and cause similar effects)
Nigrostriatal - Movement. Too little dopamine here causes Parkinson’s. Extra-pyramidal SEs also here.
Tuberoinfundibular - lactation (increased on risperidone)
Where, in the brain, is Noradrenaline made?
Locus ceruleus
Linked to wakefulness
Amphetamines increase NA (+Dopa), hence inc wakefulness
Mickey mouse midbrain anatomy
Head ventral
Chin Dorsal
Eyes - red nuclei
Nose - oculomotor nuclei + edinger westphal
Ears - cerebral peduncles (motor connection from brain to below)
Eyebrows - Substantia nigra - dopaminergic neurons involved in motor co-ordination
Tears - medial lemiscus (imp. in spinothalamic tract) Afferent fibres (sensation)
Mouth - cerebral aqueduct
Strawberry around mouth - periaqueductal grey - micturition and pain regulation
Chin - superior calliculus - reflexes
Why give Carbidopa with L-DOPA?
AbL-DOPA -> Dopamine by Aromatic Amino Acid Decarboxylase (AACD)
Dopamine causes GI side effects such as Nausea and Anorexia
To prevent SE, inhibitor of AACD, Carbidopa given.
L-DOPA cross BBB, Carbidopa doesn’t, so once in brain environment AACD can convert it and dopamine can exert the intended therapeutic effect.
What cranial nerve important in diplopia / abduction?
Abducens
Same side lesions - i.e. no decussation
What cranial nerves sensitive to injury by raised ICP?
Abducens
Oculomotor
Shingles, what cranial nerve can be affected?
Herpes zoster
Trigeminal
bridging vein leak leads to what type of haemorrhage
sub dural
crus cerebri other name
cerebral peduncle
mickey mouse’s ears
connects cerebral cortex to brainstem
Which part of the brainstem lies at the level of the tentorium cerebelli?
The midbrain sits in the ‘tentorial notch’ and can be compressed if the uncus of the temporal lobe herniates into the posterior fossa.
Cushing’s Reflex
Cushing’s reflex, consisting of hypertension, bradycardia, and respiratory irregularity, which is a feature of medullary compressio
A tumour at the level of the interventricular foramen might lead to dilatation of which structures?
Lateral ventricles
The lateral ventricles drain to the interventricular foramen before entering the third ventricle.
What are the 7 different modalities of sensation?
Pain Temp Pressure Stretch Vibration Joint position sense 2-point discrimination
What leads to an action potential of sensation?
Mechanical manipulation of a receptor
Produces a generator potential
What influences your perception of the strength of a stimulus?
FREQUENCY of action potentials
Analogue signal made into binary
Why does conscious feeling of clothes go away after a while?
Adaptation of the pressure receptors - they are phasic I.e. Rapidly adapting.
These means that after a while they adjust and stop firing so frequently. They are sensitive to change - meaning removing the stimulus will also be felt.
How is it possible that damage may occur at c6 level, but dermatome appears intact?
May have overlapping receptive field with c5 dermatome
This is why dermatomal boundaries are difficult to delineate
Lateral inhibition
1st order neurone sends signal to its 2nd order, as well as an excitatory signal to an inhibitory neurone - which inhibits the 2nd order neurone of the adjacent 1st order neurone, stopping its signal from propagating.
Summarise the dorsal column pathway
Pathway for light touch, 2-point discrimination, joint perception, vibration
Primary afferents enter at spinal level, cell body in DRG, and ascend to medulla, where they synapse with secondary. Second order neurone decussates and ascends along medial lemniscus of contralateral side, and synapses with 3o neurone at thalamus. From thalamus 3o relays signal to corresponding part on homunculus.
Lower limb afferents travel medially in fasciculus gracilis, whilst cervical and thoracic travel laterally in fasciculus cuneatus
Summarise the spinothalamic tract
Primitive. Crude touch, temperature, pain
Primary afferent cell body in DRG, synapses with secondary in dorsal horn.
Secondary neurone decussates at same level and ascends in spinothalamic tract of opposite side (near ventral horn).
Synapses to 3o neurone at thalamus, which then conveys to appropriate region of cerebral cortex according to homunculus.
Lower limb represented lateral to thoracic and cervical.
Why does rubbing make pain better?
C fibres carry pain
A fibres transmit mechanical pressure
A fibre synapses with enkephalinergic interneurones at the dorsal horn, which inhibits the 2o neurone of the c fibre, terminating its signal.
Briefly describe the descending control of pain
Periaqueductal grey (receiving input from hippocampus and cerebral cortex), sends signal to nucleus Raphe magnus which activates enkephalinergic neurones that inhibit the 2o neurones (which receive input from c fibres).
Funiculi are….
Subdivisions of spinal chord
Dorsal - have dorsal columns, sensory
Ventral - cortcospinal , motor
Lateral - has spinothalamic tract, sensory
What inputs make up your balance?
Vision
Proprioception
Vestibular system
Two needed to stay balanced
Pacinian corpuscle
Ruffini endings
Meissner corpuscles
Pc Rapidly adapting mechanoreceptor
Vibration
Ruf shearing stress
Meissner corpuscles rapidly adapting delicate touch like reading braille
Internuclear ophthalmoplegia can be caused by damage to which pathway?
The Medial longitudinal fasciculus helps to yoke eye movements together (and integrate input from the vestibular system
