everything Flashcards
what are the main negative and positive neurotransmitters?
GABA and Glutamate
what are bundles of axons called in the PNS and CNS?
PNS: nerves
CNS: Tracts
what is a unique characteristic on the DRG neurons
They are the only ones with circular cell bodies
CNS 5 main glia?
NG2 cells: discovered when using antigens to study NG2 which was linked with glia driven re-myelination these are oligodendrocyte precursors.
Ependymal cells: these line the fluid filled cavities of the brain. in the choroid plexuses (produce CSF).
Oligodendrocytes: CNS version of the schwann cells, but, these can myelinate several neurons.
Microglia: the macrophages of the brain, they exist in a ramified (dormant state) with large patrolling processes. upon the detection of a pathogen they undergo hyperplasia and enter an active state.
Astrocytes: the most abundant glia, these have a major role in regulating the BBB, removal of NT at synapses, gliotransmission (ATP, GLUTAMATE, usually driven by calcium conc increase.)
Microglia relation to aging brain and some diseases:
Microglia can enter an irreversible active state in which they can become neurotoxic and destructive contributing to neurodegeneration. this has been related to aging brains and some neurodegenerative diseases.
spine fluid cavities and blood vessels?
The spine has:
1 large ventral artery
2 small dorsal arteries
1 central fluid filled canal which is surrounded by stem cells.
What are the mininges?
These are protective layers that surround the brain.
Dura mater: thick outer layer attached to the skull
Arachnoid: thinner but tough layer attached to the duramater
Pia mater: thinner layer that covers the cortex into the grooves (gyri) aswell. this attached to the arachnoid by the denticulate ligament
What is the denticulate ligament?
this attaches the pia mater to the arachnoid.
Where is the CSF in the brain?
In the subarachnoid space inbetween the pia mater and the arachnoid. also in the ventricles of the brain.
What is the function of the CSF?
Buoyancy: the Brain almost floats in the CSF preventing the brain crushing its self under its own weight
Protection: the CSF acts a fluid buffer reducing damage to the brain when there are blows to the head. (When someone is knocked out the brain hits the side of the skull, CSF is suppose to prevent this.)
Homesostais: the ventricular system allows fro the spreading of things like neurendocrine molecules.
Waste removal: things like metabolites can be rapidly diffused into the CSF and then into the blood stream.
outline the ventricular system?
There are 2 lateral ventricles, one in each hemisphere.
These collect in the 3rd ventricles.
Csf flows via the Cerebral aqueduct into the 4th ventricle which lies between the cerebellum and the Brain stem.
CSF flows out into the sub-arachnoid space via the median aperture.
CSF is then reabsorbed into a large vein onto of the brain via arachnoid villi.
what are the 4 lobes of the brain?
front to back: frontal under side: temporal topside: parietal ocipital.
danger related to ventricular blockage?
a block of CSF flow through the median aperture can cause a build up of pressure in the brain. this is HYRDROCEPHALUS.
Lumbo sacral and cervical enlargement
enlargements ins spinal cord to facilitate larger supply (of nerves) to lower and upper limbs respectively
Lumbo sacral : T11- L1/2
Cervical : C3- T1/2
white vs grey matter
grey: largely contains the cell bodies of neurons
White matter contains long myelinated processes and fibers.
3 types of shape and size of neurons?
Unipolar: 1 short process, found in spinal ganglion
Bipolar: also found in the spinal ganglion, these can be seen to have 2 processes emerging from the same point and diverging or emerging from opposite sides of the cell. (axon and dendrite)
Multipolar: these are very large with multiple processes, axon or dendrite. these are stellate or pyramidal in shape.
What does the forebrain form?
Telencephalon: 2 cerebral hemispheres
Diencephalon: the thalamus and subthalamus, hypothalmus.
Role and site of pre-central and post central gyrus
theses are found on the lateral surface of the brain either side of the central sulci.
Precentral gyrus is the primary motor cortex thus controlling the motor output to the contralateral side of the body.
Post-central gyrus: primary sensory cortex: information form the contralateral sensory receptors. inputs from the thalamus have a maintained somatotopic map.,
what separates the central gyri?
the central sulcus
what separates the temporal and frontal lobes?
the sylvian fissure = lateral fissure
3 frontal lobe gyri (on lateral surface)
superior, middle, inferior frontal gyri
3 temporal gyri ( lateral surface)
superior( next to lateral fissure), middle and inferior temporal gyri.
2 Gyri on caudal side of brain (lateral surface)
sub marginal gyrus
angular gyrus: this has been associated with reading and writing.
Role and site of cingulate gyrus?
this is found on the medial surface above the corpus callosum.
the cingulate gyrus is a key part of the limbic system, it relyas information from the thalamus and neocortex to the entorhinal cortex. thus this plays keys roles in behaviors and memory.
Role and site of corpus callosum
the corpus callosum can be found on the medial surface beneath the cingulate gyrus.
its is a large bundle of myelinated fibres and allows fror communication between the hemispheres
Role and site of paracentral lobule
this is found on the medial surface and is the continuation of the pre/post- central gyri.
Anterior represents the supplementary motor area, an area activated by thinking about a movement and contains motor maps for things like posture.
posterior: this is related to somatosensation for the distal limbs (below knee)
What separates the parietal and occipital lobes
the parieto-occipital sulcus, this is seen on the medial surface.
Role and site of calcarine sulcus
the calcarine sulcus is seen on the medial surface, this goes through the occipital lobe.
the primary visual area exists within the boundaries on the calcarine sulcus and the V2 (visual association) area is around V1. central vision enters at the posterior and peripheral at the anterior ends.2 primary processes out of V1, 1 goes to the parietal and leads to an understanding of ‘where’ and one goes to the occipital and gives an understanding of ‘what’ both may not be lesioned.
lesions to the calcarine sulcus can lead to what is called ‘cortical blindness’ the inability for basic processing of the visual stimuli means patients are blind. However, studies show that many patients can avoid obstacles and guess what an object is in front of them more often than chance would allow. this is thought be due to V2 still being intact to carry out the more complex analysis’s.
Role and site of fusiform gyrus
this is found on the medial surface below the parahippocampal gyrus and above the inferior temporal gyrus. exists in both hemispheres
Fusifrom gyrus has a key role in facial recognition. lesion to what is known as the fusifrom face area will result in Prosopagnosia, in which individuals can not recognise people based off their faces.
Role and site of uncus
this is found on the medial surface of the brain on the anterior end of the parahippocampal gyrus.
this contains some of the olfactory cortex,
in the case of tumours or hemorrhage a common issue involves in the uncus applying pressure on the 3rd cranial nerve.
Role and site of parahippocampal gyrus
this is found on the medial surface of the brain above the fusiform gyrus.
the parahippocampal gyrus is involved in the memory of enviroments, hence why it surround the hippocamus.
Role and site of wernickes area
the wernickes area can be found on the medial surface around the posterior end of the lateral fissure. it stretches cross both the parietal and temporal lobes.
this area plays a key role in the understanding of language and is found often on one hemisphere, this being the dominant hemisphere which is often the left hemisphere.
Role and site of brocas area
this is found on the medial surface above the lateral fissure in the frontal lobe.
this plays a key role in the formation , word selection, of language.
site of frontal eye field control
this is found in an area anterior to the pre-motor cortex, in the frontal lobe.
stimulating this area was found to cause both eyes to look to the side contralateral to the hemisphere of stimulation.
Role and site of Fornix
the fornix is another bundle of myelinated axons attached to the corpus callosum via the septum pellucidum. this is found ventral (under)to the corpus callosum, running over the 3rd ventricle
its function is not yet fully understood but its exists as part of the limbic system and lesion down the fornix, seen in split brain patients can cause to memory loss.
role of prefrontal cortex?
this is involved in cognition and personality.
Role and site of thalamus?
the thalamus exists beneath the corpus callosum, runs either side of the 3rd ventricle.
the thalamus acts as a primary relay and input station of peripheral information entering the cortex.
Role and site of insular cortex
the insular cortex is on the inside of the brain, under the cortex.
its has roles linked to conscieness and awareness of self.
What connects the wernickes and brocas areas?
they are connected by the arcuate fasciculus.
What connects the wernickes and brocas areas?
they are connected by the arcuate fasciculus.
what is SUMS?
Intra-parietal sulcus, construction ability of the brain, right hand side.
cause of epidural hematoma
fracture of the temporal lobe can rupture meningeal arteries causing the release of blood into the epidural space ~(between skull and periosteal dura mater)
pyramidal vs inter neurons
pyramidal neurons are the most abundant and excitatory, use glutamate.
interneurons: everything else, bipolar cells, basket or stellate cells.
these have heteromorphic (varying ) structures and there processes are almost completely contains in the grey mater.
types of connections in the brain (4) example
: projection :efferent and afferent connections are motor going out or sensory coming in. these relate to projections going out (to terminate in thalamus, brain stem , spine) or into the cortex.
diffused: diffused projections are wide spread and non-specific. examples are that of the Noradrenaline release form the locus coerulus.
serotonin from the nucleus basilis: this is degenerated early on in AD.
association: these connect the inputs and the outputs of the system. for example the connection between wernickes and brocas area via the arcuate fasciculus.
or the connection between V1-V5 or to the inferotemporal lobe or the prefrontal cortex.
Commisural: connection between the hemispheres. corpus callosum.
changes in PV cells associated with schitzophrenia
PV cells are parvalbumin cells.
these are a small inhibitory neuron found throughout the cortex. a genetic mutation in the ERBb4 receptor in schizophrenia. The mutations prevent its role in the growth and migration of these neurons.
In addition other inhibitory interneurons like the BASKET and CHANDELIER neurons have reduced synapses and numbers.
overall there is a reduced inhibitory function in the brain.
resulting in increase cortical excitation and gamma wave release.
what is the risk of an unbalanced function of interneurons and pyramidal neurons?
a 25% reduction of interneurons in mice was shown to cause several issues involving epileptic seizures.
What is wallerian degeneration?
this is the result on a lesion of a neuron.
the central end will degenerate up to other first node of ranvier, whilst the peripheral end will degenerate all the way
in the end there is only fragments of axon that are surrounded by fatty deposit, forming due to the breakdown of myelin.
the axons are then reabsorbed.
what are the main vessels in the circle of willis (draw)
the basilar artery (lying over the pons) will split froming the posterior cerebral arteries.
ahead: over the mid brain is the actual circle of willis
at the most anterior end are the anterior cerebral arteries.
the anterior cerebral arteries are connected to eachother by the anterior communicating arteries.
the anterior cerebral arteries and the middle cerebral arteries are fed by the internal carotid arteries.
the anterior end and the posterior end of the circle are connected by the posterior communicating arteries.
what is the main area that the anterior cerebral arteries feed?
the anterior cerebral arteries will cover most of the medial surface of the cortex. they are key in supplying the motor cortex and thus occlusion can lead to a loss of motor function.
What does the middle cerebral artery feed?
the middle cerebral artery runs along the lateral fissure having a key role in the perfusion of the brocas area. hence occlusion can cause a loss of speech.
bifurcations after leaving the fissure feed the basal ganglia. (via lenticulostriate arteries)
what does the posterior cerebral artery feed?
the posterior cerebral artery runs along the calcarine sulcus (medial occipital cortex) and thus occlusion can result in cortical blindness. also covers alot of the inferior and middle temporal lobe.
what are the ganglionic and cortical systems and what are the main arteries feeding them.
the 3 cerebral arteris branch off to feed 2 major vacualr systems.
The ganglionic system feeds the thalami and the corpura striata. there are 6 groups:
The antero-medial: formed of the anterior cerebral arteries and the anterior communicating artery.
The postero-medial: formed of the posterior cerebral artery and the posterior communicating artery.
antero lateral: this is the middle cerebrals alone (one for each hemisphere)
postero lateral: just the posterior cerebral arteries (one for each hemisphere.
there is also the cortical system: this ramifies(splits) in the pia mater to supply the cortex and the subadjacent areas.
these can be long, penetrating into the subadjacent area a with little inter-communication, these will from there own circuits.
short: concentrated perfusion the middle zone of grey matter.
occlusions in these areas will result in the ‘softening’ (degen) of mal-nourished areas. in addition the poorly nourished areas between these systems are seen to soften with age.
What are terminal arteries?
terminal arteries are used to refer to the large arteries like the cerebral arteries. these have poor perfusion areas due to limitted anastomotic branches. (blood vessel that connects 2 vessels.
primary site of anuerysms and treatment?
these can commonly occur on the basilar artery and the subsequent loss of blood into the CSF can cause death.
commonly a balloon of blood on the vessel will appear first that can be clipped, this often causes bursting its self. alternatively a contraption that busts the balloon and then plugs the hole is used.
what are the anterior choroid arteries?
this is a thin artery that is fed by the internal carotid artery.
it travels to the choroid plexus in the lateral ventricle and also feeds deep brain areas like the globus pallidus and putamen on the way.
however due to being a thin vessel supplied by a high pressure large vessel this is at risk of rupture.
what is the role of the limbic cortex?
integration of taste and smell, decision making, assessing risk and reward
What are the intracranial venous sinuses
these are veins found in the cranial cavity from the folds of the dura. most of the eventually collect in the internal jugular vein
site and role of the superior and inferior coliculi
the coliculi can be found on the posterior (back) side of the mid brain. they exist dorsal (above) the 4th ventricle as 4 bumps.
the 2 most dorsal bumps are the superior colliculi. these are involved in the association of eye motor movement in response to visual stimuli.
the 2 most ventral,smaller, bumps, are the inferior colliculi and they are related to associated motor movement in response t visual stimuli.
what are the cerebellar peduncles? (afferent and efferent tracts.)
the 3 cerebellar peduncles can be seen on the inferior lateral surface of the cerebellum and they connect the cerebellum to the pons.
looking at the inferior lateral surface of the brain you can only see the large middle peduncle, the inferior (lower) and superior (higher) peduncles can be seen by looking at the posterior surface of the pons, they are situated around the floor of the 4th ventricle.
superior peduncle: Afferent- anterior spinocerebelar tract
Efferent: dentato and dentatorubro thalamic tract
middle: this only contains 1 tract and that is the afferent pontocerebellar tract (feedback information from the cortex.
inferior : afferent: posterior spinocerebellar tract,olivocerebellar tract, vestibulocerebellar tract.
Efferent: cerebrocerebellar, cerellovesitbular and cerebellar olivary tracts
outline the layers of the cortex what is the general role of the cortex?
the cortex has a role of processing and integrating data of multiple modalities to achieve an understanding of the stimuli. this allows for us to come up with the best response to said stimuli.
the majority of the cortex is NEOCORTEX. This has 6 core layers:
I: this is sparsely populated by neurons. did contain horizontal neurons but these are almost non-existent in adults.
II: this layer is densely populated with small neurons.
III: this is the outer pyramidal layer and has medium sized pyramidal neurons. these are excitation multi polar neurons. they have a apical dendrite projecting to layer 1 and a basal axon projecting to layer 6 where it the projects laterally.
IV: this is full of small neurons. these tend to be inter neurons like stellate and granule cells. these can be both inhibitory and excitation. ( This is the main afferent input layer)
V : this is full of large pyramidal neurons. this is the main efferent output layer of the cortex and is the origination site of the corticospinal tract and the corticostriatal tract.
VI: thisis full of polymorphic neurons. this is commonly populated by fusiform neurons that project to the thalamus. (hence site of corticothalamic tract)
the main layer will vary throughout the cortex based on function (Motor, Sensory, Association cortex.)
exceptions to the 6 layer rule are the olfactory cortex and the cortical part of the limbic system.
What are the mammillary bodies?
These are found directly attached to the hypothamus and can be seen below the 3rd ventricle on the inferior surface of the brain.
they are involves in the PAPEZ circuit and damage due to them ,by thiamine (Vitamin B1) deficiency or lesion, has been related to anterograde amnesia. ( cannot form memories)
outline the lateral view structure and general function of the cerebellum
in general the cerebellum is though to play a key part in the coordination of complex movements and the correction of movement aswell as stabilty.
On the superior lateral surface a central part of the cerebellum is the VERMIS, this is flanked by the PARAVERMIS.
on the inferior lateral surface there is the several observable structure. still down the center is the vermis but at the base of the vermis is the NODULE.
to either side of the nodule is the FLOCULUS
at the very base of the cerebellum are the CEREBELLAR TONSILS
The surface can be seperated into 3 lobes, the anterior, posterior and flocullonodular (floculus and nodule)
layer structure of cerebellum
The cerebellum consists of many folds to allow the immense storage of nerve cell bodies. a cross sectional view shows 4 distinct layers ( 3 grey matter 1 white matter.
Molecular layer: the outermost layer consist of parallel
fibres (longitudinal communication) and inhibitory inter neurons, stellate and basket cells.
Purkinkje layer:these are inhibitory (GABAergic) neurons will large process to the fourth layer. these are the primary output of the cerebellum (go to deep nuclei). large dendritic tree in the molecular layer is weakly excitated by glutamatergic synapses with parallel fibres.
Granule layer: this consists of excitatory granule neurons. these synapse with 1 prukinje cell after excitation by mossyfibres.
white matter layer: apart form the movement of processes this does have climbing fibres. these travel up the layers and excite the purkinje cells at the dendrites and soma. (these arise from the inferior olive in the medulla)
Golgi cells also exist that inhibit the granules cells to keep the signalling of purkinje fibres short and meaningful.
outline functional areas of the cerebellum with relation to functional loops
There are 3 main functional areas of the cerebellum and each is associated to a specific functional loop.
Spinocerebellum: this is the vermis and the paravermis.
input from the IPSILATERAL spine influences the spinocerebellum.
this is relayed to the deep brain nuclei by (spinocerebellar tract (anterior ,superior peduncle, posterior, inferior peduncle)
the deep brain stimuli relay this to the reticular formation, red nucelei and the vestibular nuclei, who in turn relay it to the spine, this is to control trunk stability.
(Spinocerebellar tract from spine originates in the Ipsilateral CLARKES COLUMN)
The deep nuclei also relay this to the thalamus and then onto the cortex. this information is fed back to the spine after analysis in the cortex, this is for corrections of movement. ( key for walking gait)
Vestibulocerebellum: this is the floculus and the nodule and paravermis
the vesitbulocrebellum receives inputs from the vestibular nuclei ( via the vestibular- cerebellar tract through the inferior peduncle)
the vestibulo cerbellum sends information back to the vestibular nuclei (via the fastigial nucleus or the cerebello-vestibular tract via the inferior peduncle) and to the reticular formation. this information is relayed (via reticulo spinal or vestibulospinal tracts)to the spinal nuclei to control trunk stability and influence anti-gravity muscles.
cerebrocerebellum: this is most of the posterior cerebellum.
the cerebellum send information to the dentate nucleus via the dentatorubrothalamic tract through the superior peduncle.
the dentate nucleus relays this to the ventral anterior or ventral lateral thalamus and then that onto the motor cortex.
the cortex can then feedback this information to cerebellum via the pontine nuclei ( relay info back to cerebrocerebellum via the pontocerebello tract through the middle peduncle) (intention tremor)
or
relay back to the spinal cord. via the cortical spinal tract.
this is all to streamline cortical output.
Where does Clarkes column begin and end?
the clarkes column begins at L2/3 and finsihes beside T1.
Do the vestibulospinal and reticulospinal tracts deccusate.
the reticulospinal tract decussates but the vesitbulospinal tract does NOT.
Which vestiblar nuclei connections are used by the vestibulocerebellum?
the vestibular nuclei can give feedback to the spine to control trunk stability.
The vestibulo spinal also aims to influence head and eye movements via the vestibular nuclei’s communication with cranial nerve III,IV and VI (oculor motor, trochlear, abducens)
How is an ipsilateral intention tremor caused?
this results from the a lesion in the cerebrocerbellar loop (pontocerebellar tract)
Ventral anterior and ventral lateral thalamus projections
these are part of the ventral lateral complex of the thalamus. VL project to the premotor and primary motor cortex and VA to th supplementary motor cortex, they are used by the spinocerrebellar loop of cerebellum.
difference between VA nuclei and VL nuclei, is VA is mainly innervated by the globus palidus, whilst VL involves most of the basal nuclei including the substantia nigra.
3 sections of the brainstem
medulla, pons, midbrain
What are the primary ascending and descending tracts in the brain stem?
Ascending: spinocerebellar, dorsal column medial lemniscus, anterolateral system, spinothalmic
Descending: cortico spinal
What is the site and role of the olives?
the olives can be seen either side of the pyramids on the anterior surface of the muddulla.
They contain the superior and inferior olivary nuclei.
inferior: though to be related to the olivio-cerrebellar system and is related to the motor learning function of the cerebellum. climbing fibers arise from here.
superior: this is thought to be part of the pons and has a role in the perception of auditory stimuli.
outline the anterior surface structure of the brain stem?
at the base of the brain stem is the mudulla. down the center are a thick rod which represents the pyramids, containing descending spinal tracts. (cortico spinal decussates at the base)
either side of the pyramids are the olives.
above this is the pons. the 2 cerebral peduncles can be seen branching out of the top.
between the cerebral peduncles and below the 3rd ventricle are the mammilary bodies, which are attached to the hypothalamus which cannot be seen.
outline the posterior surface of the brain stem
on the posterior surface although not visible the 2 gracilus fasciculus run up the center of the medulla and the 2 fsciculus cuneatus run adjacent to these up the mudulla. they will synapse with their nuclei.
above the mudulla is the pons. the floor of the fourth ventricle is visible with the superior and inferior cerebellar peduncles adjacent to it. adjacent to these peduncles is the large middle cerebellar peduncle.#
above the fourth ventricle on the mid brain the 4 bumps representing the 2 superior and 2 inferior coliculi are observable.
where does the spinal cord terminate?
the neonatal spinal cord terminates at L1/L2
what is the filum terminalae
this is an extension of the pia at the caudal end of the spinal cord. this connects the caudal end of the spinal cord to the coccyx.
breakdown of spinal vertebrae? (segments numbers)
there are 31 vertebrae in total, top to bottom-
Cervical-8 Thoracic-12 Lumbar-5 sacral-5 coccyx-1
outline the main land marks on cross-sectional view of the spine?
the spine grey matter has a butterfly like shape, with a smaller dorsal horn and larger ventral horn on either side.
grey matter is surrounded by white matter.
there 2 paired smaller dorsal arteries and 1 larger ventral artery.
what is the change in white matter levels as you travel from caudal (bottom) to rostral (top) spinal cord? why?
the white matter levels increases as you travel from the caudal to the rostral end. this is because all the processes from lower ganglia are also travelling through this section of the spinal cord.
(grey matter is larger in the cervical and lumbar sections)
What are the segmental arteries?
these are arteries deviating from the vertebral basilar system. they feed the spinal arteries and the 2 dorsal arteries and the ventral artery of the spine.
how many spinal nerves are there?
31 pairs, 1 pair for each vertebrae.
Which vertebrae contribute to the sympathetic and parasymapthetic NS?
the sympathetic nervous system is associated with T1-L2
the parasympathetic is associated with S2-S4 (also in brainstem)
What is the substantia gelatinosa
the substantia gelatinosa represents the first and second laminae of the spinal grey matter, they contain most of the secondary afferent mediating nociceptive signalling.
Whats the difference between alpha and gamma motor neurons?
alpha innervate the extrafusal (muscle contracting fibres)
the Gamma innervate the intrafusal fibres, found in muscle spindles.
what is the consequence of a lower spinal cord neuron lesion?
a lower spinal cord lesion results in neuron death and a flacid paralysis which will result in muscle wasting.
outline the stretch muscle reflex
the stretching of the muscle is detected by the intrafusal fibres in the muscle spindle. this send a signal via the Ia afferent to the dorsal horn of the significant vertebra. the
the Ia afferent synapses on the alpha motor neuron for the flexor muscle to contract it. the Ia afferent will also synapse on an inhibitory interneuron that in turn inhibits the motor neuron associated with the flexors extensor muscle to relax it. this causes movement of the arm away from the stimuli.
What is the consequence of a an upper (brain stem or brain) motor lesion?
this results in the death of the axon.; here we get spastic paralysis (constant contraction) this results in limited muscle wasting.
which artery feeds the corticospinal tract
the basilar artery
where does the corticospinal tract decussate?
at the base of the pyramids in the medulla.
What is locked in syndrome
this is a state of complete loss of voluntary movement. a state of conscious paralysis.
this can result from the rupturing of the basilar artery.
What are the folds of the cerebellum called?
folia
draw a diagram of a transectional view of the brain stem at the level of the superior coliculi
check with drawn diagram
which lamina are the motor neurons found
lamina IX
which spinal tract controls voluntary movement?
the corticospinal tract or the corticobulbar tracts. contain info from motor cortex pyramidal neurons.
what is a nucleus?
this is a group of neuronal cell bodies
outline the spinothalamic tract?
the spinal thalamic tract confers information on pain and temperature. it is part of the anterolateral system.
C-fibres from the periphery enter the IPSILATERAL side of the spinal cord and rise 1-2 segments before synapsing on a secondary interneuron in layer 2 (part of substantia gelatinosa)
the interneuron will decusate to the contralateral side via the anterior white commisure.
the processes will rise via the spinothalamic tract that travels up in the lateral column.
this will go up through the brain stem and eventually synapse with the ventral post lateral thalamic nuclei where the signal is relayed to the primary sensory cortex. this is a 3 neuron pathway.
role and site of periaqueductal grey?
the periaqueductal greay can be seen at the top of the brain step (transectional view).
this is involved in acting via descending tracts on nocicpetion via the use of endogenous opioids. activity is observed in placebo)
also innervates the raphe nuclei to use there 5HT tracts to influence the superficial dorsal horn
beginning of gracilus and cuneatus fasiculus
the gracilus fasciculus transmits info from the lower limbs and is ever present.
The cuneatus fasciculus transmits info from the upper limbs and is first seen at the thoracic 6 segment.
where are most c-fibre found?
mostly found to terminate in the 2nd layer of the spinal grey matter.
where are most A delta fibres found?
mostly found in the laminae 1 of the spinal grey matter.
what is allodynia?
this is when non-painful stimuli cause pain. often follows recovery to a traumatic injury and touch/mechanoreceptors activate nociception.
major cause in individuals that cant feel pain?
nocieptors nerve ending in the periphery are activated by a large concentration of NAv1.7 CHANNELS.
genetic mutations show offspring without this and thus nociceptive signalling is not initiated. this can lead to major problems with joints. Mutation in SCN9A gene
What is syringo myelia?
this usually occurs in the cervical region as it is the most mobile. there is the developement of a syrinx (fluid cavity)
damage here results in the loss of feeling from the upper limbs. (damage to spinothalamic tracts
What is a ventrolateral cordotomy and what is it used for?
this is commonly used in the case of cervical tumours. the spinothalamic tract can be lesion to prevent nociceptive signalling from pressured areas and thus reduce pain.
pain returns due to other signalling pathways and regeneration.
outline the dorsal column medial lemniscus pathway?
This is influenced with proprioception and fine touch.
A beta fibres come from skin and synapse on secondary afferents. depending on the level these will travel up the spine in the fasciculus gracilus or cuneatus. this occurs on the side ipsilteral to the stimulus
this will travel up to the base of the muddula passed the decussation of the pyramids and then once in the upper closed muddula they will synapse with their significant nuclei (gracile or cuneatus)
the nuceli will project to the medial lemniscus ( gracile to the left and cuneatus to the right)
the medial lemniscus will deccusate to the contralateral side and rise up through the brain stem. at the level of the pons they will appear flattened.
eventually the medial lemniscus will synapse with the thalamic nuclei which then projects to the primary sensory cortex.
outline the cortico spinal tract?
this is involved with the control of voluntary movement.
it will eventually break into two tracts the anterior and lateral cortico spinal tracts, these are for postural adjustment and skilled movements respectively.
this arises in layer V of the primary motor cortex.
tracts will travel as one sole cortico spinal tract down the posterior limb of the internal capsule.
once at the top on the brain stem the tract will continue this ipsilateral flow via the crus cerebri, and then breaking into multiple fascicles at the level of the pons
at the level of the open muddula the coticospinal tract has entered the pyramids and will travel down to their base where the tracts decussate. it is the lateral tract that deccusates, mean while the anterior tract continues on the ipsilateral side.
after this point the both tracts travel down the spine. the lateral will synapse with motor neurons on the contralateral side whilst the anterior will synapse with motor neurons on both sides.
What is the babinski sign?
this is a sign that can be seen in individuals with upper spinal lesions.
stroking the underside of the foot results in the toe pointing down rather than up. (this is also seen in babies due to incomplete spinal myelination)
what do c-fibres and A beta fibres confer?
C-fibres confer pain
A beta confer touch
what is the anterolateral system?
the antero lateral system consists of the anterior and lateral column. it works to both signal pain via the spinothalamic tarct and to modulate the nociceptive signalling via smaller tracts.
what is the somatotopic organisation of the tracts
the ascending tracts can be broken down into groups of nerves based on where they arise from.
i. e the cuneatus most central from thoracic and then cervical
gracilus: most cental from sacral and then lumbar
lateral corticospinal tract and spinothalamic can be seperated into cervical most central and sacral least
what vessel supplies the spinothalamic tract?
the large ventral spinal artery
What vessels supplies the dorsal column?
the 2 paired small dorsal arteries.
which vessels supply the cotico spinal tracts ? (in the spine)
the lateral is fed by the paired dorsal arteries and the anterior is fed by the large ventral artery.
somatotopic arrangement of cortico spinal tract in posterior limb of internal capsule
it can be seen that there are specific subgroups on the tract that are for the arm, trunk and legs
Name and number all 12 cranial nerves (also give general function (Motor, sensory both)
I- olfactory- sensory II-optic-sensory III-oculomotor- motor IV-Trochlear- motor V-Trigeminal- Both VI- Abducens- Motor VII-Facial- Both VIII- vestibulocochlear- Sensory IX-Glossopharyngeal- Both X-Vagal- Both XI-Spinal accessory- motor XII- Hyperglossal- motor
what are the crus cerebri
cerebellar peduncles
what are the changes observed in the position of motor and sensory nuclei seen between the closed muddulla and the mid brain?
The sensory nuclei exist in what is known as the alar plate and motor nuclei in the basal plate.
as you ascend through the brainstem the alar plate rotates to more lateral positions from a more posterior position. when the 4th ventricle begins to narrow in the cerebral aqueduct in the upper pons the alar plate rotates back to this posterior position.
Draw a diagram of the positions of the cranial nerves in the brain stem
check with diagram
Which cranial nerves contribute to the nucleus solitarius?
the caudal part seen at the level of the open muddulla this is mainly the vagus and glossopharyngeal nerve gastointestinal and repiratiory changes
The rostral part in the lower pons is mainly the glossopharyngeal and facial nerves. (taste)
which cranial nerves contribute to the nucleus ambiguous? what is the function
seen at the level of the open muddula, this is formed of the glossopharyngeal and vagal nerves.
motor control of larynx, pharynx and upper oesophagus to control swallowing.
lesion results in nasal speech.
which cranial nerves are involved in the spinal trigeminal sulcus
the spinal trigeminal, this is seen in the closed mudulla and is the trigeminal, vagal, glossopharyngeal and facial nerves.`
What is the artery of adamkowitz
this is the largest segmental artery feeding the lumbar and sacral region.
occlusion of the artery can result in a loss of lower motor control.
What is lateral mudullary syndrome?
the lesion or rupturing of the Posterior-inferior- cerebral artery results in the loss of contralateral trunk sensation and loss of ipsilateral cranial nerve function.
sensations of pain and temperature are severely reduced.
what is the role of the nucleus ambiguous
this supplies the muscles of the larynx an pharynx via the glossopharyngeal and vagal nerves.
What are the 3 branches of the trigeminal nerve (significance of 3)
opthalmic, mandibular, maxillary
What information do the trigeminal tracts carry?
this is the main sensory nerve and caries both pain, temperature, fine touch. (pontine/chief trigeminal
the c-fibres mediating the pain and temperature signalling signals the thalamus by the trigeminothalamic tract. (spinal trigeminal
A beta fibres signal he fine touch by the trigeminal lemniscus.
also carries motor efferents to the muscles driving mastication.these exist in the mandibular branch.(tirgeminal motor)
mescenphalic trigeminal will send info to trigeminal motor forjaw reflex and send info on proprioception.
What are the function of the facial nerve and which brain stem nuclei mediate them?
This will activate the lacrimal glands, submandibular and sublingual glands (submandibular and pterygopalatine ganglion), this is the part of the facial nerve in the superior salivary nucleus
the facial motor nuclei loops around the abducens nucleus and will go on to activate the facial muscles for expressions. the cortical activate is via the cerebrobulbar tract
facial nerve also receives somatosensory taste from tthe anterior 2/3rd s of the tongue and projects to the nucleus solitarius. this relays info onto the amygdala and and hypothalamus (arousal) and th ventral post lateral thalamic nuclei which wil relay the info to the tatse cortex on the insula cortex.
result of upper and lower facial motor lesion have varying effects, why?
an upper motor lesion in the cortex will result in the paralysis of the contralateral lower face. the upper face is bilaterally innervated so doesn’t get paralysed
the lower motor lesion of the facial motor projection results in ipsilateral paralysis of the whole face
