Flashcards in Neuroanatomy Deck (499):
What is the peripheral cortex?
Folded, multilayered sheet of grey matter on the surface of the brain that is thrown into folds forming gyri and sulci
List the three types of cerebral cortex (telencephalon)
1. Paleocortex 2. Archicortex 3. Neocortex
Where is the hippocampus located?
Medial part on interior surface of temporal lobe
List the 3 main parts of the hippocampus
Uncus, fornix, dentate gyrus
Which cortex is known as the place where the 'interoceptive self' meets the 'exteroceptive self'?
Which part of the human cortex is strongly affected in Alzheimer's disease?
Which structures make up the limbic lobe?
Parahippocampal gyrus, septal area and cingulate gyrus
The entorhinal cortex and hippocampus are the mediators of what functions?
The limbic lobe is on the medial aspect of the brain and it's components encircle which structures?
Corpus callosum and diencephalon
List at least 3 functions of the hippocampus
1. Formation and retrieval of sptial memory 2. Processing and categorisation of new information 3. Differentially modulates aggression and rage 4. Modulates endocrine functions of the hypothalamus
Hippocampal lobectomy results in what outcomes?
Inability to form new memories but long-term memories and intellectual skills not affected
Stimulation of the pole of the hippocampus closest to the amygdala promotes ______ behaviour; activation of he pole nearest the septal area suppresses ______ behaviour
What is the septal area of the limbic lobe?
A relay nucleus of the hippocampus to the hypothalamus
List at least 3 functions of the septal area of the limbic lobe
Control of aggression and rage, regulation of endocrine functions, reward/pleasure centre (self-stimulation; drinking behaviours), regulates the discharge of hippocampal neurons during learning of new tasks/goal-directed behaviour
Which brain structure is also known as the brain's alarm system?
What are the 2 major functions of the amygdala?
1. Mediates adaptive responses 2. The most powerful regulator of the hypothalamus/endocrine functions
Which brain structure is the most powerful regulator of the hypothalamus/endocrine functions?
Which type of human cortex is comprised of 6 layers?
What is primary neocortex?
Main input from a particular modality (i.e., vision, touch on skin, sound waves) = one function. All information must go through thalamus, and these two areas are reciprocally connected.
What is secondary neocortex?
Limited to particular modality but may be limited to a speicifc feature of that modality (i.e., specific area of visual cortex dealing with colour)
What is association neocortex?
Area that gets inputs from a number of different modalities (e.g., visual and auditory like Wernicke's).
The majority of cells in the neocortex are whay types of cells?
Large excitatory pyramidal cells with very long axons (and most non-puramidal cells are inhibitory GABAergic)
All sensory input enters which layer of the neocortex?
Why is layer 4 of the neocortex also known as the striatal layer?
So many axons come into this layer and synapse that a dark stripe can be seen on sectioning
Different cortical areas interact with each other through cells located in which layers of neocortex?
II and III
Primary sensory cortex has high density of inputs into which layer of the neocortex?
Primary motor cortex has high density of inputs into which layer of the neocortex?
Pyramidal cells in layers V and VI
What is the name of the structure comprised of alternating columns of striate cortex receiving inputs from one eye and then the other?
Ocular dominance columns
What process results in amblyopia?
Visual deprivation involving one eye results in the non-deprived eye taking over the territories of the deprived eye
Within each ocular dominance column, there are ____ columns
____ sensicite regions are regulary spaces within each ocular dominance column
Commisural fibres originate in which layer of neocortex? What is their target?
III; contralateral cortex
Association fibres originate in which layer of neocortex? What is their target?
III; ipsilateral cortex
List the 5 major association bundles of cortical white matter
1. Uncinate fasisculus 2. Superior occipitofrontal fasisculus 3. Superior longitudinal (arcute) fasisculus 4. Inferior occipitofrontal fasisiculus 5. Cingulum
What is hydroencephalus?
Enlargement of the ventricles causing raised ICP
Areas of the skull where the dura is folded back onto itself results in the formation of which features?
Venous dural sinuses
What is the falx cerebri?
Large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres
What is the tentorium cerebelli?
An extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes
What is the diaphragm sellae?
flat piece of dura mater with a circular hole allowing the vertical passage of the pituitary stalk. It retains the pituitary gland beneath it in the fossa hypophyseos as it almost completely roofs the fossa hypophyseos of the sella turcica, a part of the sphenoid bone
List the venous sinuses of the brain
Sagittal (superior and inferior), straight sinus, cavernous sinus, transverse, petrosal and signmoid
Where does the falx cerebri attach to the anterior skull?
The falx cerebri attaches anteriorly at the crista galli in proximity to the cribriform plate and to the frontal and ethmoid sinuses
Where does the falx cerebri attach to the posterior skull?
Posteriorly, it is connected with the upper surface of the tentorium cerebelli
Which sinus is contained in the superior margin of the falx cerebri and overlies the longitudinal fissure of the brain?
What is the final dumping ground for all fluid leaving the skull?
The anterior meningeal artery is a branch of which other artery?
Internal carotid > ophthalmic artery > internal ethmoidal artery > anterior meningel artery
Where does the anterior meningeal artery enter the cranium?
Lateral part of cribriform plate, from the orbit
The middle meningeal artery is a branch of which other artery?
Maxillary artery (terminal branch of external carotid)
Where does the middle meningeal artery enter the cranium?
The posterior meningeal artery is a branch of which other artery?
Ascending pharyngeal artery
Where does the posterior meningeal artery enter the cranium?
Could be jugular foramen, foramen mangnum, hypoglossal canal (or all 3)
Which is the largest vessel supplying the dura region of the posterior fossa?
Posterior meningeal artery
Which major vessel that supplies the dura mater is epidural?
Why is the middle meningeal artery much more likley to cause haemorrhage than the anterior and posterior meningeal arteries? Why is this type of haemorrhage particularly dangerous?
Lies embedded within the skull bone directly behind the weak point between the temporal and parietal bones (pterygoid). Even a light blow to the side of the head can dissect the artery, causing an epidural bleed. This is dangerous because the patient may not know it is happening, which is why someone with a concussion should be advised to stay awake, so that their consciousness can be monitored. If they were to go to sleep and then develop so much bleeding that they become unconscious, they would never wake up and you would never know the difference
What structures are formed when the arachnoid mater skils from gyrus to gyrus and around the brainstem, leaving large spaces between the pia and arachnois mater?
Anatomically, how are the cerebral artery vessels separated from the neural environemnt? What is the advantage of this arrangement?
As they invaginate into the brain, they take the pia mater with them, which forms the barrier between the vessel and the brain. This helps to minimise passive diffusion of blood-born substances into the neural tissues
What is the purpsoe of tight junctions between endothelial cells in the BBB?
Prevent blood cells and large molecules from squeezing between cells and entering the neural microenvironment (i.e., physical barrier)
What are some of the mechanistic adaptations of the BBB?
Virtual absence of vesiscular transport across the membranes f vascular endothelial cells of the cerebral vessels
Unknown factors derived from _____ appear to play a role in maintaining the integrity of the blood brain, and blood retinal, barriers
Mechanistic adaptations of the BBB are maintained via what signals? What disrupts these signals?
Cell-cell signals; disrupted by inflammatory events
Astrocytes are located in the neural environment and define a _____ space
Which major artery do the vertebral arteries branch from? Where does this originally branch?
Subclavian; as it loops over the first rib
What region does the anterior spinal artery supply? What are some of the important structures in this region?
Anterior 2/3 spinal cord, and anterior medial brainstem below the open medulla. Important structures in this area of the brainstem include the pyramids (corticospinal tracs) and some of the medial lemniscus (some sensory) etc.
What region does the posterior spinal artery supply? What are some of the important structures in this region?
Posterior 1/3 of spinal cord, posterolateral midbrain. Important structures = dorsal column pathway
At what level do the vertebral arteries unit to form the basilar artery?
What do the paramedian branches of the basilar artery supply?
Pons adjacent to the midline (including corticospinal tracts)
What do the short circumferential branches of the basilar artery supply?
Supply more lateral regions of pons
What do the long circumferential branches of the basilar artery supply?
Perforate the brainstem and supply the region between the pontocerebellar fibres and the 4th ventricle
Which 3 branches of the basillar artery supply the pons and region between the pontocerebrallar fibres and 4th ventricle?
Paramedian branches (midline), short circumferential (lateral pons) and long circumferential (region betweeen pontocerebellar fibres and fourth ventricle)
What region is supplied by the posterior inferior cerebellar artery?
Most of the inferior surface of the cerebellum, lateral upper medulla including the inferior cerebellar peduncle
What regions are supplied by the anterior inferior cerebellar artery? What are the important structures in this area?
Anterior segment of inferior cerebellar surface,middle cerebellar peduncles and inferolateral parts of the pons' ponto-cerebellar fibres
What regions are supplied by the superior cerebellar artery? What important structures lie in this region?
Superior surface of the cerebellum, superior cerebellar peuncle; mainly efferent fibres of cerebellothalamic tract, cerebellorubral tract. Also has afferent tracts tectocerebellar etc.
What are the terminal branches of the basilar artery?
Posterior cerebral arteries (L and R)
What structures in the brainstem are supplied by the posterior cerebral arteries?
Most of cerebral peduncles and almost all of the tectum
Unilateral infarction of the posterior cererbral artery causes what visual field defect?
List the 3 stroke syndromes of the midbrain
Webers, Benedikt, Claude syndromes
What is Weber syndrome? What is the likley presentation
Midbrain stroke syndrome that involves the occulomotor nerve resultin in ipsilateral CNIII palsy and contralateral hemiplegia or hemiparesis
What is Benedikt syndrome? What is the likley presentation
Midbrain stroke syndrome that involves the occulomotor nerve and red nucleus. Results in an ipsilateral CNIII palsy and crossed hemitaxia and chorea
What is Claude syndrome? What is the likley presentation
Midbrain stroke syndrome where there is infarction to the dorsomedial aspect of the midbrain secondary to occlusion of small perforating branches of the posterior cerebral arteries. Infarction involved red nucleus, CNIII nucleus and superior cerebellar peduncle. Clinical picture includes ipsilateral CNIII nerve palsy and contralateral upper and lower limb ataxia
Which nerves traverse the lateral wall of the cavernous sinus, and which lies closes to the internal carotid artery?
1. CN III, IV, V1, V2; the nerve closes to the internal carotid is abducens (VI)
After winding around the ____ peduncles, the Pca crosses the gap between the brainstem and the _____ lobe, where is branches into the ______ and _____ PCA.
Cerebral; temporal lobe; lateral and medial PCA
The ACA winds laterally around the ___ ____ then passes medially towards the medial aspect of the _____ lobe
Optic chiasm; frontal
The medial cerebral artery enters the lateral _______
Which cortical territories are supplied by the anterior cerebral artery?
Superior parietal lobule, superior frontal gyrus,medial strip of the cortex from the frontal lobe bakc to the beginning of the occipital lobe, and basically all of the inner parietal lobes (extending up and over the ventricles)
Which cortical territories are supplied by the middle cerebral artery?
Inferior frontal gyrus, superior temporal gyrus, most of the temporal lbe, precentral and post central gyri, inferior parietal lobule, inferior parietal lobe
Which cortical territories are supplied by the posterior cerebral artery?
Occipital lobe, inferior temporal gyrus, inferior part of the temporal lobe
The deep cerebral structures of the brain are supplied by which vessels?
1. Perforating branches of the cerebral arteries on the base of the brain 2. Communicating arteries of the circle of willis
Which vessel supplies the hippocampus and amygdala?
Anterior choroidal artery (branch of internal carotid or sometimes the middle cerebral)
Which deep territories of the brain are supplied by the perforating branches of the anterior cerebral artery?
Anterior limb of the internal capsule, the inferior portions fo the head of the caudate and anterior globus pallidus
From which cerebral artery do the medial and lateral striate arteries originate?
What deep structures of the cortex do the lateral and medial striate branches of the medial cerebral ateries supply?
Internal capsule and reticular formation
What strcuctures are supplied by the anterior choroidal artery (branch of internal carotid)?
Choroid plexus of lateral and third ventricles, optic chiasm and tract, internal capsule, lateral geniculate body, globus pallidus, tail of caudate nucleus, hippocampus, amygdala, substantial nigra, red nucleus and crus cerebri
List the 3 main features of system of venous drainage of the brain. What is the purpose of this organisation?
1. A limited number of large veins that make contact with brain matter 2. Direct course of veins into venous dural sinuses 3. Dural sinuses separated from the brain surface by CSF in the subarachnoid space (helps prevent brain from overheating)
Describe the venous drainage of deep cortical structures
Composed of dural venous sinuses. Most prominent is the superior saggital sinus, which forms the confluence of sinuses where it meets the sinus that drains the deep structures. From here, 2 transverse sinuses bifurcate and travel laterally and inferiorly in a S-cruve that form the sigmoid sinuses, which then go on to form the jugular veins.
Describe the venous drainage of superficial cortical structures
Primarily composed of traditional veins inside the deep structures of the brain, which join behind the midbrain to form the vein of Galen (great cerebral vein). This vein merges with the inferior saggital sinus to form the straight sinus, which then joins the superficial venous system at the confluence of sinuses. Blood then collects into the transverse sinuses > sigmoid sinuses > jugular veins > SVC
What is the functional significance of the pyramids?
Contain descending fibres from motor cortex
What is the functional significance of the pons?
Contains fibres that cross the midline to enter the cerebellum
What is the functional significance of the cerebral peduncles?
Contains descending fibres from all over the cortex, which terminate in the brainstem (corticobulbar) or spinal cord (corticospinal)
What is the functional significance of the mamillary bodies?
Part of the hypothalamus
What is the functional significance of the occulomotor nerve?
Supplies motor fibres to 4 out 6 extra ocular muscles, and includes parasympathetic fibres to the iris and ciliary body
What is the functional significance of the facial nerve?
Innervates muscles of facial expression
What is the functional significance of the trigeminal nerve?
Sensory nerve to the face
What is the functional significance of the thalamus?
All fibres on their way to cerebral neocortex pass through the thalamus.
What is the functional significance of the optic tract?
Carries axons from both eyes, that encode information from the opposite visual hemifield
What is the functional significance of the pineal gland?
Endocrine gland that regulates our circadian rhythms by releasing melatonin
What is the functional significance of the trochlear nerve?
Fourth cranial nerve which provides motor innervation to the superior oblique muscle
What is the functional significance of the superior colliculus?
Receives a mapped input from the retina, which guides reflexes responses to stimuli of auditory (e.g. scary sound), somatosensory (e.g.,creepy crawlies on the skin), or visual (e.g. ducking to avoid a fast moving /dangerous object coming towards you unexpectedly) origin
What is the functional significance of the dorsal columns?
Carry pressure and fine touch fibres from the body surface (proprioception)
What is the functional significance of the middle cerebellar peduncle?
Comprises the major descending input from cortex to cerebellum: cortico-pontine > ponto-cerebellar fibres
The lateral horn of the spinal cord is only present at which spinal cord levels?
What are the 3 divisions of CN V?
V1: ophthalmic division V2: Maxillary division V3: Mandibular division
What are the main functions of V1 (CN V)?
Ophthalmic division: sensory to upper face and eye, anterior nasal cavity and some sinuses
What are the main functions of V2 (CN V)?
Maxillary division: sensory to the middle face, maxillary sinus and nasopharynx
What are the main functions of V3 (CN V)?
Mandibular division: sensory to the lower face, motor supply to msucles of mastication
What are the main functions of CN VII (facial)?
Motor to muscles of facial expression. Parasympathetic/secretomotor supply to lacrimal, sublingual and submandibular glands. Taste (special sense) to anterior 2/3 of tongue
What are the main functions of CV VIII?
Vestibulocochlear: special senses hearing (cochlear) and balance (vestibular apparatus)
What are the main functions of CN X?
Vagus - Visceromotos fibres (from dorsal motor nucleus of vagus - parasympathetic) to heart and bronchi, digestive tract as far as the left colic flexure. Sensory to external acoustic meatus and part of auricle. Carries motor fibres to striated muscles of larynx and pharynx (derived from nucleus ambigulous via cranial accessory nerve)
What are the main functions of CN XII?
Hypoglossal: motor fibres to the intrinsic muscles of the tongue (four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. They are the superior longitudinal muscle, the inferior longitudinal muscle, the vertical muscle, and the transverse muscle)
List the name of the nuclei, location and function of the occulomotor nerve
1. Motor nucleus at level of superior colliculus - controls SR, MR, IR and IO muscles of the eye. 2. Edinger Westphal nucleus at level of superior colliculus - controls ciliary and pupillary muscles
What ganglion serves the Edinger Westphal nucleus of the occulomotor nerve?
List the name of the nuclei, location and function of the trochelar nerve
Motor nucleus at level of inferior colliculus - controls the SO muscle
List the name of the nuclei, location and function of the trigeminal nerve
1. Motor nucleus at level of superior colliculus - pons: controls muscles of mastication, tensor vali palinitin, tensor tympani and anterior digastric 2. Principal V nucleus at the level of the pons: controls sensation (touch) to the face 3. Spinal V nucleus at the level of the medulla - upper spinal cord: controls sensation (pain and temperature) of the face 4. Mesencephalic nucleus at the level of the superior colliculus - upper pons: controls sensation (proprioception) of face
Which ganglion serves the Principal V and spinal V nuclei of the trigeminal nerve?
List the name of the nuclei, location and function of the abducens nerve
Motor nucleus at level of the pons - controls LR muscle of the eye
List the name of the nuclei, location and function of the facial nerve
1. Motor nucleus at lower pons - muscles of facial expression, stapedius, posterior digastric and stylohyoid 2. Super salivatory nucleus at lower pons - lacrimal, submandibular and sublingual glands 3. Solitary nucleus (taste) in medulla for taste to anterior 2/3 tongue 4. Spinal V nucleus in medulla - upper spinal cord for somatic sensation around the ear
Which ganglion serves the super salivatory nucleus of the facial nerve?
Pterygoipalatine and submandibular (parasympathetic)
Which ganglion serves the solitary nucleus and spinal V nucleus of the facial nerve?
List the name of the nuclei, location and function of the vestibulocochlear nerve
1. Superior, lateral, medial and inferior vestibular nuclei at the ponto-medullary junction for balance 2. Cochlear nucleu at the ponto-medullary junction for hearing
Which ganglion serves the vestibular nuclei of the vestibulocochlear nerve?
Which ganglion serves the cochelar nuclei of the vestibulocochlear nerve?
Spiral ganlgion (sensory)
Where are the rostral and caudal solitary nuclei of the glossopharyngeal nerve located, what ganglion are they served by, and what is the function of each?
Located within open and closed medulla and served by inferior ganglion of IX (in jugular foramen). Rostral is responsible for taste in the posterior 1/3 of tongue and caudal is responsible for baroreceptors and chemoreceptors (carotid)
List the 5 nuclei of the glossopharyngeal nerve
1. Solitary (rostral) 2. Solitary (caudal) 3. Spinal V 4. Nucleus ambigulous 5. Inferior salivary
Which ganglion serves the spinal V nucleus of the glossopharyngeal nerve?
Superior ganglion of IX (in jugular foramen)
Which ganglion serves the inferior salivatory nucleus of the glossopharyngeal nerve?
Where is the spinal V nuclei of the glossopharyngeal nerve located and what is it's function?
Medulla - upper spinal cord, responsible for somatic sensation behind auricle of ear
Where is the nucleus ambiguous of the glossopharyngeal nerve located and what is it's function?
Open and closed medulla - responsible for branchiomeric muscles of the pharynx and larynx
Where is the inferior salivatory nucleus of the glossopharyngeal nerve located and what is it's function?
Open medulla and responsible for action of parotid gland
List the name of the nuclei, location and function of the vagus nerve
1. Dorsal motor nucleus of X in open medulla - thoracic and abdominal organs (visceral afferent) 2. Spinal V nucleus in medulla - upper spinal cord for somatic sensation to external ear, external auditory canal, external surface of tympanic membrane 3. Solitary nucleus in open and closed medualla for taste (epiglottis); pharynx, larynx, trachea, esophagus, thoracic and abdominal viscera (visceral afferent)
Which ganglion serves the dorsal motor nucleus of X (vagus)?
Walls of viscera (parasympathetic)
Which ganglion serves the Spinal V nucleus of the vagus nerve?
Superior ganglion of X (in jugular foramen)
Which ganglion serves the solitary nucleus of the vagus nerve?
Inferior ganglion of X (in jugular foramen)
List the name of the nuclei, location and function of the accessory nerve (cranial)
Nucleus ambiguous in open and closed medulla - responsible for intrinsic muscles of the larynx
List the name of the nuclei, location and function of the hypoglossal nerve
XII motor nucleus in open and closed medulla - responsible for muscles of the tongue except that palatoglossus
The hypoglossal nerve is responsible for all muscles of the tongue EXCEPT for which one?
What are the main functions of the medulla?
contains theÊcardiac,Êrespiratory,ÊvomitingÊandÊvasomotorÊcenters and therefore deals with the autonomic functions ofbreathing,Êheart rateÊandÊblood pressure
What are the open and closed parts of the medulla?
Superior part is openÊwhere the dorsal surface is formed by theÊfourth ventricle (creates the caudal half of the rhomboid fossa (floor of the 4th ventricle). The inferior part is closed, where the fourth ventricle has narrowed and surrounds part of theÊcentral canal.
Describe the location of the tectum
On the dorsal surface of the midbrain
Which CNs exit from the midbrain?
III (occulomotor) and IV (trochlear). Note that the trochlear nerve is the only nerve to exit dorsally from the brainstem
Which CNs exit from the pons?
V (trigeminal), VI (abducens) and VII (facial)
Which CNs exit from the medulla?
VIII (vestibulocochlear), IX (glossopharyngeal), X (vagus) and XII (hypoglossal)
What is the clivus, and what brain structure is it closely related with?
part of theÊcraniumÊat the skull base, a shallow depression behind theÊdorsum sell¾Êthat slopes obliquely backward. The pons sits on the clivus.
What is the sella turcica, and what brain structure is it closely related with?
a depression in the sphenoid bone, containing the pituitary gland
What is the optic groove (chiasmatic groove), and what brain structure is it closely related with?
Ridge on the superior body of the sphenoid that forms the anterior border of a narrow, transverse groove, theÊchiasmatic groove, above and behind which lies theÊoptic chiasmaÊof cranial nerve 2 (the optic nerve)
Consider CNI: What is the site of nerve attachment and the site of exit from the skull?
Olfactory bulb; cribiform plate
Consider CNII: What is the site of nerve attachment and the site of exit from the skull?
Lateral geniculate nucleus (thalamus) and midbrain; optic canal
Consider CNIII: What is the site of nerve attachment and the site of exit from the skull?
Interpeduncular fossa; superior orbital fissure
Consider CNIV: What is the site of nerve attachment and the site of exit from the skull?
Midbrain tectum inferior to inferior colliculus; superior orbital fissure
Consider CNV: What is the site of nerve attachment and the site of exit from the skull?
Lateral margin of the mid-pons; V1 exits at superior orbital fissure, V2 exits at foramen rotundum and V3 exits at foramen ovale
Consider CNVI: What is the site of nerve attachment and the site of exit from the skull?
Medial edge of pontomedullary sulcus; superior orbital fissure
Consider CNVII: What is the site of nerve attachment and the site of exit from the skull?
Lateral edge of pontomedullary sulcus; internal acoustic meatus
Consider CNVIII: What is the site of nerve attachment and the site of exit from the skull?
Lateral edge of pontomedullary sulcus (lateral to CN VII); internal acoustic meatus
Consider CNIX: What is the site of nerve attachment and the site of exit from the skull?
Lateral to the olive of the medulla; jugular foramen
Consider CNX: What is the site of nerve attachment and the site of exit from the skull?
Lateral to the olive of the medulla; jugular foramen
Consider CNXI: What is the site of nerve attachment and the site of exit from the skull?
Lateral surface of the upper vercial spinal cord; jugular foramen
Consider CNXII: What is the site of nerve attachment and the site of exit from the skull?
Between pyramid and olive of medulla; hypoglossa canal
Which 3 CNs exit the skull through the superior orbital fissure?
III, IV and V1
Which 2 CNs exit the skull thorugh the interal acoustic meatus?
VII and VIII
Which 3 CNs exit the skull through the jugular foramen?
IX, X, XI
Describe where the first, second and third order neurons of themedial lemniscal pathway (dorsal column system) arise and synapse
First-order neurons reside in dorsal root ganglia and send their axons through theÊfasciculusÊgracilis andÊcuneatous. The first-order axons make contact with second order neurons at the gracilis and cuneate nuclei in the lowerÊ(closed) medulla. The second-order neurons send their axons to theÊthalamus. The third order neurons arise from thalamus to the postcentral gyrus
Fibres from which other nerve join with the dorsal column system information is it travels upwards as the medial lemniscus?
Fibres from the trigeminal nerve
Describe where the first, second and third order neurons of the spinothalamic pathways arise and synapse
First order have cell bodies in dorsal root ganglion and synapses in dorsal root of spinal cord on the ipsilateral side. Second order neurons cross the cord and send fibres upward to synpase in the thalamus. Third order neurons are sent up to the somatosensory cortex in the post-central gyrus
What information do the spinocerebellar tracts convey?
information to the cerebellum about length and tension of muscle fibers (i.e., unconscious proprioceptive sensation)
The dorsal spinocerebellar tracts carries information from which receptor types?
Muscle spindles and golgi tendon organs (i.e., information about skeletal muscle and joint proprioception)
Briefly describe the dorsal spinocerebellar tract
Proprioceptive information is taken to the spinal cord via dorsal root gangliaÊ(first order neurons). Central processes travel through theÊdorsal horn, where they synapse with second order neurons ofÊClarke's nucleus. Fibres from Clarke's Nucleus convey information in the spinal cord in the peripheral region of theÊfuniculus posteriorÊipsilaterally. The fibers continue to course through the medulla oblongataÊand theÊponsÊof theÊbrainstem, at which point they pass through theÊinferior cerebellar peduncleÊand into the cerebellum. This tract involves twoÊneuronsÊand ends up on the same side of the body
What information do the dorsal spinocerebellar and cuneocerebellar tracts relay?
Both relay proprioceptive information, but the former is more concerned with forearm, trunk and lower limb, which cuneate is concerned with the arm
Vry briefly describe the ventral spinocerebellar tract
The ventral spinocerebellar tract will cross to the opposite side of the body first in the spinal cord as part of theÊanterior white commissureÊand then cross again to end in the cerebellum (referred to as a "double cross")
CSF is produced by the ____ lexuses, located in the ___ and ___ ventricles
Choroid, lateral and fourth
The anterior choroidal artery is a branch of the ____ artery, and enters the ____ horn of the lateral ventricle
Internal carotid, inferior horn
The anterior choroidal artery supplies the optic tract as far as which structure?
Dorsal lateral geniculate nulceus
The plexuses of each lateral ventricle are continuous with each other via which structure?
Intraventricular foramen (of Munro)
From the 4th ventricle, most CSF leaves the ventricular system via which 2 foramen? Where does the CSF then flow?
Luschka (lateral) and Magendie (medial). CSF then enters the subarachnoid cisterns that surround the cerebellum
List the 4 places that CSF flows after entering the cerebello-medullary cistern
1. Down and around the spinal cord 2. Anteriorly and up into the pontine and interpeduncular cisterns 3. Upwards and backwards around the cerebellum and into a cistern posterior to the midbrain 4. Around the tentorium cerebelli into the subarachnoid space of the middle and anterior cranial fossa
Briefly describe how the CSF is resorbed into the venous system
Arachnoid granulations (outpuchings of arachnoid meninges) pass through small openings in fibrous dura later and endothelial linin of superior sagittal sinus. CSF is pumped up towards this sinus under hydrostatic pressure, where is diffuses through the granulations into the venous blood
What are tracts?
Bundles of axons of neurons in the CNS (white matter)
What name are given to bundles of axons that connect the anterior part with the posterior part of the brain?
What name are given to bundles of axons that connect right and left sides of the brain?
Give an example of a white matter commissure in the brain
What are neurological receptors?
Biological transducers - convert one type of energy to another (i.e., mechanical stimulus to Aps)
Motor neurons exit the spinal cord _____, whilst sensory informatio is taken into the ___ horn
The ventral and dorsal root of the spinal cord combine to form the spinal _____, which then divides into an anterior and posterior _____
The anterior ramus of a spinal nerve innervates structures in which part of the body?
Anterolateral wall of the body
The dorsal ramus of a spinal nerve innervates structures in which part of the body?
Back of the body
Dorsal columns of the spinal column are also known what what other name?
Which is the only white matter column that sends ONLY ascending tracts?
Dorsal columns (funiliculi)
Which ascending tracts of the spinal cord are most modern/advanced? What sort of information do they carry?
Dorsal columns. More heavily myelinated than anterolateral tracts, so carries faster information > very fine touch, proprioception, vibration and position and is highly specialised (rather than crude temperature, pain, etc. in anterolateral tracts)
List 4 types of receptors that transmit information regarding fine touch, proprioception, pressures, vibrations into the ascending dorsal tract
Meissner receptors, Pacinian receptors, goldi tendon organs and muscle spindles
The dorsal root ganglion contains which neural structure?
Cell body of first order neuron (first in chain of sensory system)
Within the dorsal column, sensations from the lower body are located ____, while caudal structures are added in ____
If there is a lesion impinging on the medial part of dorsal tract of the spinal cord, sensations from which structures will be lost? What if the lesion were affecting the lateral part of the dorsal tract only?
Those from the lower limbs (as lowest structures are carried most medially). If the lesion were in the lateral part of the dorsal tract, upper limb sensation would be lost.
All sensory fibres from the lower limb that enter the dorsal column (up to level of C6) make a special medial ascending bundle called ____?
All sensory fibres from the upper limb, abdomen and thorax that enter the dorsal column make a special lateral ascending bundle called _____?
If a section of the spinal cord is viewed from the level of L1, comment on which dorsal column bundles will be seen
Only 1 fasisculus gracillis on each side (no fasisculis cutaneous at this point because it only carries sensation from the upper limbs)
The dorsal columns are made up of the ____ processes of which neurons?
Central processes of first order neurons whose cell bodies lie in the dorsal root ganglion (and whose peripheral processes bring sensory information into the spinal cord)
Dorsal columns carry sensory information from which side of the body?
The same side as the column (i.e., information does not cross)
What is the name of the bundle of fibres connecting medulla with cerebellum?
Inferior cerebellar peduncle
The fibres from the dorsal columns terminate in which nuclei?
Nucleus gracillis and nucleus cuneatous/cuneate in lower medulla
The cell bodies present in the nucleus cuneatous and gracillis are what sort of neurons?
Second order (first order was in dorsal root ganglion)
Describe the trajectory of axons from the cell bodies of second order neurons in the nucleus graccilis and cuneatous
Cross to contralateral side at level of nuclei (in lower medulla) and move upward
What is the name given to the fibres from the nucleus gracillis and cuneatous that cross in the lower medulla before moving upward?
Internal arcuate fibres
What is the name given to the ascending group of second order neurons of the nucleus graccilis and cuneatous, after they have decussated in the lower medulla?
Medial lemniscus (there is a right and left - and each carries sensory information from the opposite side of the body)
The dorsal column medial lemniscus system is comprised of which structures?
Fasisculus graccilis and cuneatous, nuclei gracillis and cuneatous, internal arcuate fibres and right/left medial lemnisci
What is the name given to axons/fibres in the CNS that form a circular bundle? What if they form a flattened bundle?
Where do the second order neurons of the medial lemniscus system (dorsal ascending system) terminate?
In the thalamus
If sections of the brainstem are taken, comment on where the medial lemnisci will be seen and why
Upper medulla and passing through pons and midbrain. Will not be seen in lower medulla, as this is where the fibres from the second order neurons are decussating before forming the ascending medial lemnisci (right and left)
VPL nucleus receives what sort of information?
Most of the sensation from most of the body (touch, pain ,temperature, position)
VPM nucleus receives what sort of information?
Sensation from taste fibres and head/neck fibres
The second-order neurons in the medial lemnisci reach the thalamus and terminate in which nucleus?
VPL (ventroposterolateral): second order neurons terminate and third order neurons originate here
In which nucleus do the third order neurons of the dorsal ascending system originate?
VPL of the thalamus
Which nuclei are present on the lateral sides of the thalami?
Which arc-shaped nucleus stretches over the thalami and connects to the lentiform nucleus?
Between the thalamus and lentiform nucleus is which white matter bundle?
In between the right and left thalami is which fluid-filled cavity?
Third order neurons from the dorsal column sensory system originate from VPN of the thalamus and travel upward through which structure? What happens to these fibres once they pass through the capsule?
Posterior limb of internal capsule. After passing through, fibres radiate outward to cerebral cortex (corona radiata) and eventually connect to cortex in post central gyrus (sensory cortex)
From which structure does the corona radiata originate?
Posterior limb of the internal capsule
What are the receptors in the skin for pain and temperature?
Free nerve endings for pain and thernal receptors for temperature sense
The pain pathway has which 2 distinct fibre types carrying information to the CNS?
A delta (sharp/fast pain) and C fibre (dull, diffuse pain) pathways
The thermal sensory pathway follows the same pattern as which other pathway?
What is the stimulus for fast pain?
Mechanical or thermal pain (usually from the skin)
What is the stimulus for slow pain?
Mechanical or thermal pain, and chemical pain (can be from skin or deeper structures)
Which chemical substances originate from tissue damage and can stimulate the nerve endings for pain?
5-HT, histamine, bradykinin, acids (and potassium from injured cells)
Which 2 chemical substances cannot cause pain, but can reduce the threshold for pain if present in tissue?
Substance P and prostaglandins
The first order neurons for the pain (and temperature) pathway have their cell bodies in which location?
Dorsal root ganglion
First order neurons in the pain pathway terminate in which location?
In the substantia gelatinosa in the dorsal grey horn of the spinal cord
Describe the origin and pathway of second order neurons in the pain (and temp) pathway (anterolateral pathway)
Originate in the substantia gelatinosa in the dorsal horn of the spinal cord and cross to the contralateral side at the same level of the spinal cord.
As sensory pain/temp fibres enter the spinal cord, they give off which branches to form which tract?
Ascending and descending branches, which form their own local vertical tract (dorsolateral tract of Lissauer) within the spinal cord
The dorsolateral tract of Lissauer is made up of what structures?
Ascending and decending branches of first order neuron central prcesses as they enter into the spinal cord
Cell bodies of the second order neurons fom the pain/temp (anterolateral) pathway exist where?
Within the dorsal horn of the spinal cord (at the level of entry) in the substantial gelatinosa
The lateral part of the lateral spinothalamic tract carries pain and temperature information from the ____ lower part of the body, and the medial part of the tract carries information from the _____ part of the body.
Describe the path that the second order neurons of the pain/thermal pathway take
Originate in substantial gelatinosa and decussate the spinal cord the the level of entry before ascending as the lateral spinothalamic tract.
Compare and contrast the information carried by the lateral spinothalamic and anterior spinothalamic tracts
Lateral carries pain and temperature information, anterior carries information about crude touch
The tectum is part of which brain strcture?
What is the name of the swellings on the posterior midbrain?
Superior and inferior colliculus (= tectum)
The tectum of the midbrain is made up of which 2 strucutres?
Superior and inferior colliculus
Which 3 ascending spinal pathways fuse together in the medulla and then run anatomically as a single bundle up to the thalamus? What is the name of the bundle?
Lateral and anterior spinothalamic tracts and spinotectal tract. Form the spinal lemniscus
What is the spinotectal pathway responsible for?
The medial lemniscus is formed from the ____ tract, whilst the spinal lemniscus is formed from the _____
edial formed form dorsal column system, spinal lemniscus is formed from the anterolateral tract (combination fo anterior and lateral spinothalamic tracts and spinotectal traact)
Where do the anterior and lateral spinothalamic tracts and spinotectal tracts terminate? (after they have fused to form the spinal lemniscus in the medulla)
Anterior and lateral spinothalamic tracts terminate in the VPL nucleus of the thalamus, whilst the spinotectal tract terminates in the superior tectum/colliculus (note that slow/diffuse pain fibres also terminate in the internal thalamic lamina)
Compare and contrast where the fast vs slow pain second order neurons from the pain pathway terminate
Fast pain all terminate in VPL nucleus of the thalamus. Slow/diffuse/dull pain fibres terminate in the VPL as well as the internal.intra lemina nuclei of the thalamus
Slow pain fibres intensely stimulate the _____ _____ before terminating the the VPL nucleus and internal lamina nucleus of the thalamus
What is the reticular formation?
Mixture of grey and white matter entending throughout the brainstem
What is the main function of the reticular formation?
Main switch of the brain: keeps all cerebral cortex active during the day but decreases activity night so no longer has ability to stimulate cortex - regulates sleep/wake cycles
The reticular formation has heavy connections with which nuclei of the thalamus?
Internal lamina nucleus/intra lamina nucleus
All ascending sensory pathways give collaterals to which structure of the brainstem?
What is the clinical significance of ascending slow pain fibres stimulating the reticular formation and intra laminal nucleus of the thalamus?
Painful stimuli from slow fibres irritates reticular formation to keep the CNS on and active to eliminate the source of pain (i.e., can't sleep)
Compare the information passed on to the cortex from sharp pain vs slow/dull pain fibres after passing through their respective nuclei in the thalamus
Fast pain fibres from the VPL nucleus provide the cortex with information about the characteristic and location of the pain. Slow/dull pain fibres from the intra lamina nucleus alert the whole cortex to the pain in general
What is the insula?
A portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes)
Describe the passageway of the pain pathway after travelling through the thalamus
Pass through poterior limb of internal capsule and fan out to postcentral gyrus
Some pain fibres are connected with which nucleus, which is responsible for the emotional response to pain?
The cingulate gyrus is concerned with what information?
Emotion (and emotional response to pain)
Some slow pain fibres travel to which part fo the cortex, which is responsible for autonomic responses to pain?
Explain why slow pain is diffuse and difficult to localise, while fast pain is easily located
When fast pain fibres enter the spinal cord (from A delta fibres which are myelinated), they synapse immediately with second order neuron before decussating and travelling straight up the lateral spinothalamic tract to the brain. On the other hand, slow pain fibres (C fibres, non myelinated) enter the spinal cord and then synapse with many, many neurons before decussating. In this way, the cortex finds it much more difficult to localise where the dull pain started/came from.
Which NTs are produced by pain nerve endings to stimulate second order neurons in the substantia gelatinos of the spinal cord?
Glutamate and substance P
Explain why massaging/stimulating areas of skin that are not painful can decrease the pain of another area of the body
Gate control theory: some sensory neurons have the ability to give off APs to collateral connector neurons that are connected with the second order neurons of the pain pathway and ican release NTs that inhibit them
What substances are released by the descending analgesia system in the spinal cord to reduce pain?
Enkephalins and endorphins (morphine-like)
Comment generally on areas where fibres from the descending analgesic fibres come from
Periventricular area, periaqueductal area and other midline nuclei in the brainstem
Spinocerebellar pathways carry information from the right side of the body to which side of the cerebellum?
Right - i.e., the spinocerebellar pathways are the only acending pathways that carry ipsilateral information
What are the 2 main spinocerebellar pathways?
1. Dorsal spinocerebellar pathway (cuneocerebellar pathway included) 2.
Describe the dorsal spinocerebellar pathway
Fibres enter dorsal horn spinal cord and terminate in Clark's nucleus, giving rise to second order neurons which turn laterally and enter the white matter lateral column on the ipsilateral side before ascending. They enter the ipsilateral cerebellar cortex via the inferior cerebellar peduncles
Information from which 3 receptor types contributes to the dorsal spinocerebellar pathway?
Goldi tendon organs, muscle spindles and pressure receptors
The cell bodies of the second order neurons of the dorsal spinocerebellar pathway make which vertical nucleus in the spinal cord?
Dorsolateral nucleus of clarke (Clark's nucleus)
The pons is connected to the cerebellum via what strcutures?
Middle cerebellar peduncles
The midbrain is connected to the cerebellum via what strcutures?
Superior cerebellar peduncles
What are peduncles?
Bundles of white matter which connect the brain stem with the cerebellum
The cell bodies of the first order neurons in the dorsal spinocerebellar system exist in which spinal levels. What about Clark's nucleus? What is the significance of this arrangement?
Dorsal root ganglion from C8 to S3. Clark's nucleus extends from C8 to L3 (not to lower lumbar and sacral levels). Therefore fibres which enter through lower levels must first ascend upwards to connect with Clarks nucleus
Clark's nucleus receives information from which parts of the body? What about the accessory cuneate nucleus?
Trunk and lower limb; upper limb sensory
What is the cuneocerebellar pathway?
Counter-part of dorsal spinocerebellar pathway but providing informationf rom the upper limbs via the accessory cutaneous nucleus
What is the most significant difference between the dorsal spinocerebellar pathway and the anterior spinocerebellar pathway?
Second order neurons cross the spinal cord to the contralateral side before ascending
Describe the anterior/ventral spinocerebellar pathway
Enter dorsal spinal cord and synapse, giving rise to second order neurons which decussate at the level of entry to the spinal cord and then ascend. Enter the superior cerebellar peduncle on contralateral side, and then they turn back and re-decussate across the cerebellum so they end up back on the ipsilateral side.
Briefly describe the spinotectal pathway
Enters spinal cord and second order neuron decussates before ascending to the tectum (also joins with anterior and lateral spinothalamic pathways at the level of the medulla)
Briefly describe the spino-olivary pathway
Enters spinal cord second order neuron decussates before ascending to the olive of medulla and then through the inferior cerebellar peduncles into the cerebellum
What sort of information is carried by the spino-olivary pathway?
Prioprioception, touch, pressure and sense of position (movement and posture)
Briefly describe the spino-reticular pathway
Enters spinal cord and ascends directly upward to the reticular formation
What name is given to the cortex located in the precentral gyrus?
Primary motor cortex = M1
What functions is the pre-motor area responsible for?
Planning the motor activity (programming) - i.e., where the body is located in space and what program must be executed to complete a particular movement (therefore all proprioceptive information passes to this area) - basically decides which neurons in the primary motor area need to be stimulated to carry out the movement
What is the supplementary motor area responsible for?
Bilateral primitive movement planning, such as primitive movement of hips and axial skeleton
Why is the primary motor cortex unable to function without the pre-motor area?
Because the pre-motor area decides what program must be carried out and stimuluates specific neurons in the primary area as required. I.e., the primary area cannot make decisions and needs the input from the pre-motor area, which has made the plan
Which area in the pre-motor cortex is responsible for programming patterns and neurons in the primary motor area for meaningful speech
Describe, in terms of neuroanatomy, why a baby can make sounds but not meaningful words
Speech area (Broca's area) of pre-motor cortex is not functional yet
Suppose a patient has had a stroke, and knows what he wants to say but cannot make meaningful words. What part of the area is liklely to have damaged?
Speech area (Broca's area) of pre-motor cortex (i.e., nothing is wrong with the neurons in the primary motor cortex that work the required muscles, but damage to the pre-motor area means that no program can be given to the primary area)
Describe the difference in outcome if the primary motor cortex was stimulated, vs if the pre-motor area was stimulated
Primary motor area would elicit random movements of some muscles, but stimulation of the pre-motor area would result in whole patterns of pre-programmed movement
Above Broca's area is which part of the pre-motor area concerned with eye movement?
Frontal eye field
What is the purpose of the frontal eye field in the pre-motor area?
Plan how eyes should be deviated and to what degree (stimulation on one side of the field will result in conjugate eye movement toward the opposite side)
Explain why a tumour in the pre-motor area may cause the eyes to deviate toward the contralateral side (i.e., away from the tumour) initially, but then cause the eyes to swing back toward the tumour after some time
Tumour irritating front eye field in pre-motor side causes neurons to overperform/hyperfunction. At a point where the tumour actually destroys the eye field, it is unable to program the eyes to look toward the contralateral side. However, the eye field on the other side (not affected by the tumour) is now unbalanced, so the eyes deviate toward the tumour
List the areas of the motor homunculus, from lateral to medial (within the primary motor cortex)
Pharynx, tongue, facial expression etc (speech - large area), head and neck, hand (large area), shoulder through to foot (most medially)
Describe the important areas in the pre-motor cortex, from most lateral
Brocas area, frontal eye fields, neck movement, hand movement
Where do the fibres of the descending corticospinal tracts found?
30% from primary motor area, 30% from supplementary + pre-motor area and 40% from sensory cortex (post central gyrus)
The cerebral motor cortex contains how many layers of neurons?
In which layer of the cerebral cortex are the cell bodies of the neurons that contribute to the corticospinal tracts?
What is the name of the large neuronal cell bodies that are present ONLY in the primary motor cortex? What is special about these neurons?
Cells of Batz: very large cells with very thick and heavily myelinated descending axons
Cells of Batz directly stimulate which motor neurons?
Alpha lower motor neurons
All decending fibres in the corticospinal region pass firstly through the _____ ____, and then converge in the ________
Corona radiata; posterior limb of internal capsule
Explain why a small lesion or infarct near/on the posterior limb of the internal capsule can destroy so much motor activity in the cerebrum and even lead to hemiplegia
Due to arrangement of motor fibres being so compact - i.e., lots of information in a small space as they pass through the posterior limb of the internal capsule. This posterior limb is supplied only by 1 small artery, which can commonly become blocked in old age > many fibres destroyed > equivalent of destroying all cerebral cortex > all motor movements on the contralateral side become impaired > hemiplegia (note that sensory information travelling upward would also be affected, so sensation on the contralateral side would also be impaired)
Describe the passage of the corticospinal tract fibes after passing through the internal capsule until they reach the midbrain
Pass through midbrain and converge on central 3/5ths of crus cerebri. Pass through pons and are scattered/dispersed (due to density of pontine nuclei and corticopontine/corticocerebellar fibres). Once they have reached the medulla, the re-converge to pass through the pyramids
Which structures lie beneath the cerebral adqueduct and are known to be implicated in Parkinson's disease?
What is the name given to the area of the midbrain that lies between the substantia nigra and the tectum?
What is the name given to the area of the midbrain between the substantia nigra and cerebral peduncles, where the corticospinal tracts pass thorugh?
How many segments of the crus cerebri are there? Through which sections do the corticospinal tracts pass through?
5; tracts pass thorugh central 3/5ths
What is the name given to the white matter fibres connecting the brainstem to the cerebrum?
What are pontine nuclei and what are they responsible for?
Groups of grey matter/cell bodies surround by white matter in the pons. Special fibres from the cortex terminate on these nuclei (corticopontine fibres), and from here, fibres travel through medial cerebellar peduncle into the cerebellum to give constant updates about body position
Explain why a small lesion near the corticospinal tracts as they pass throught he internal capsule is worse than a small lesion affecting the motor fibres in the pons
Because the tract is densely packed in the cerebrum but all the fibres become scattered in the pons
The pyramids of the medulla are made from what stuctures?
Fibres from coricospinal motor tracts
Describe the passage of the corticospinal tract once they have passed through the pyramids of the medulla
At the lower end of the pyramid, 90% of fibres cross and continue to descend in the contralateral side of the spinal cord (pyramidal decussation) while 10% remain on the ipsilateral side. The fibres that have crossed continue to descend through the spinal cord as the lateral corticospinal tracts, whilst the uncrossed 10% of fibres from each side run to form the anterior corticospinal tract. The lateral tracts continue down and synapse onto motor neurons in the lateral ventral horn (or via interneurons). The anterior tract fibres decussate in the spinal cord and synapse onto medial ventral horn.
Describe the location of the pyramidal decussation of the corticospinal tract
Junction of medulla and spinal cord
Describe the resultant effects on the motor system if there is a lesion above vs a lesions below the pyramidal decussion
Lesions above the decussation result in contralateral motor dysfunction, while lesions below the decussation produce motor deficits on the ipsilateral side (as the lesion is occuring after the decussation has occurred)
The fibres from the anterior corticospinal tract are concerned with what types of movements? Where does this information originate from in the cortex?
Primitive movements of the trunk/axial skeleton. Information comes from supplementary motor area
The fibres from the lateral corticospinal tract are concerned with what types of movements?
Skilled and voluntary movements (especially fine movements in the hands)
Compare the points of decussation for the anterior vs lateral corticospinal tracts
Lateral tract decussates in the pyramidal decussation (90% of fibres), and anterior (remaining 10%) decussate at the level of the spinal cord for which they are needed
List all of the areas that the corticospinal tract sends collateral information to on its descending pathway through the brain and brainstem
Feeds back to cortex, to basal ganglia (lentiform nucleus), red nucleus, vestibular nuclei and olivary nuclei
What is a lower motor neuron?
Neurons coming out of CNS (brainstem or spinal cord) and connecting to NMJs
What is an upper motor neuron?
Group of all neurons that originate at high cortical level and decend to lower motor neurons (directly or indirectly) to moderate the activity of the LMN
List the types of neurons that leave the CNS
Preganglionic parasympathetic, preganglionic sympathetic and lower motor neurons (connecting to NMJs)
What is the name given to the tract that sends descending fibres to stimulate lower motor neurons of the brainstem?
Corticonuclear fibres are synonymous with which other tract?
Those corticonuclear fibres that are specifically connected with lower motor neurons in medulla are called ____?
The superior and inferior colliculi are specifically concerned with which reflexes?
Superficial = Visual reflexes; Inferior = Auditory reflexes
Lower motor neurons receive input from which descending tracts?
Corticospinal (or corticonuclear in the brainstem), tectospinalÉ
Fibres that decending from the red nucleus and cross before descending on the contralateral side are part of what tract?
List the 5 descending tracts that originate from subcortical areas
Tectospinal, reticulospinal, rubrospinal, vestibulospinal, olivospinal tracts
What is the name of the nuclei present at the junction between the medulla and the pons?
Vestibular nuclear complex
Decending tracts that take information to cranial nerve LMNs come from the _______tract, whilst tracts that take information to the spinal nerves are carried in the _____ tract
Corticonuclear tract; corticospinal tract
What is meant by the pyramidal tracts? Which fibres are included?
Any descending tracts which pass through pyramids of medulla = corticospinal (also called pyramidal tracts) and sometimes the corticonuclear tracts are also included (because origin is the same)
Extensor musles are also known by what other name?
Which pathway (and assistant pathway) is responsible for providing input to the extensor muscles?
Vestibulospinal (and assisted by pontine reticulospinal)
Which pathway is an assisting pathway to the vestibulo spinal pathway? Which nucleus do these fibres come from?
Ponto-reticulospinal (from pontine nucleus in reticular formation)
Which pathway (and assistant pathway) is responsible for providing input to the flexor muscles?
Rubrospinal and assisted by medullary reticulospinal
Describe the vestibulospinal and ponto-reticulo spinal tracts
Begin at vestibular nuclear system and pontine reticular nuclei and decend UNCROSSED to spinal cord anterior white matter to control extensor/anti-gravity muscles
Describe the rubrospinal tract
Begin in red nucleus, cross in the brainstem and descend to the lateral white matter of the spinal cord to control the flexor muscles
What are the 2 main functions of the rubrospinal tract?
1. Enhances flexor tone; 2. Acts an accessory pathway from the cortex to spinal neurons (corticorubral fibres)
Which tract is assistant to the rubrospinal tract in controling flexor muscle tone?
Medullary-reticulospinal tract (from medullary reticular nuclei)
Sympathetic fibres originate in the ____ part of the hypothalamus, whilst parasympathetic fibres originate in the ____ part
Sympathetic fibres from the posterior part of the hypothalamus descend down the spinal tract and stimulate pre-ganglionic sympathetic neurons in which spinal levels?
If there is any interruption to the thoracic sympathetic outflow from fibres suppying T1 and T2, what is the resultant pathology? Why?
Horner's syndrome - because T1 and T2 have some sympathetic supply to head and neck. So if there is damage, there will be ptosis, anhydrosis (lack of sweating), constriction of pupil and other symptoms of Horner's
Parasympathetic outflow is from which cranial nerves?
3, 7, 9 and 10 (III, VII, IX and X)
Comment on where there is/is no parasympathetic outflow from the spinal cord
CN III, VII, IX and X. No parasympathetic outflow from cervical, thoracic or lumbar regions. S2-S4 have parasympathetic outflow (i.e., cranial sacral outflow)
Which fibres of a muscle are connected to Golgi tendons?
Alpha motor neurons connect the anterior horn of the spinal cord with which muscle fibres?
Alpha motor neurons release which neurotransmitter at the NMJ?
Cholinergic fibres (NT is ACh)
What sort of receptors are present at the NMJ and allow binding of the NT released by alpha motor neurons?
Nicotinic receptors (for ACh)
Nicotinic receptors at the NMJ are coupled with what sort of channels?
Very briefly describe the interactino between alpha motor neurons and muscle contraction
AP travels along alpha motor neuron and releases ACh into the NMJ. This binds to nicotinic receptors which are coupled to cationic channels. This causes depolarisation, and AP travels along surface of extrafusal muscle fibres and into T tubules, then they stimulate release of calcium in the cell, which leads to actin-myosin interaction (calcium bids to toponin, which moves toposiosin away so that actin and myosin can interact and contract the muscle)
The sensitivity of muscle contraction is dependent on what?
Muscle spindles (degree of stretch sensed by afferent neurons and relayed to spinal cord)
What will be the result of stimulating muscle spindles?
Stimulates increase in AP traffic in sensory stretch receptor afferents toward the spinal cord > stimulates alpha motor neurons in spinal cord > causes extrafusal muscle fibres to contract
Gamma motor neurons give motor supply to what part of the muscle?
Alpha motor neurons supply ______ muscle fibres, whilst gamma motor neurons supply ______ muscle fibres
If a gamma motor neuron is stimulated, what will be the result?
Contraction of muscle spindles > not enough to contract whole muscle but enough to produce stretch at the end of muscle spindles > more APs thrown toward spinal cord > leads to stimulation of alpha motor neuron > leads to contraction of extrafusal muscle > increased muscle tone
What sort of fibres take stretch information from muscle spindles toward the spinal cord?
Describe the pathway of a deep tendon reflex
Hammer hits tendon > produces brisk, transient stretch on whole muscle > extrafusal fibres stretched > stretches intrafusal fibres > stretch receptors increase information (APs) travelling through Ia fibres to spinal cord/CNS > transient overstimulation of alpha motor neurons > produces increased transient AP traffic to NMJ of the same muscle which was stretched > slightly increase NMJ at a very short time > transient contraction/reflex/jerk
Why is the terminology 'deep tendon reflex' a misnomer?
Because the hitting of the tendon does not target deep golgi tendon organs, but the stretch of the whole muscle
List the 5 things that can be tested in a stretch reflex
1. Intrafusal stretch receptors working 2. Sensory afferent Ia fibres working 3. Integration in spinal cord working 4. Alpha motor neuron transmission working 5. NMJ at the muscle working (i.e., in a particular spinal cord level, that input and output are working)
When are golgi tendon organs stimulated?
When there is too much tension on the muscle and it threatens the integrity of the locomotor system
Explain how golgi tendon organs are responsible for maintaining the integrity of the locomotor system
When there is undue tension on a muscle/tendon (to the point where stress would cause damage), golgi tendon organs (receptors) are stimulated > send APs to spinal cord via Ib fibres > stimulate interneurons in the spinal cord > interneurons release inhibitory NT which act on alpha motor neurons > alpha motor neuron inhibited > muscle relaxes > this is the golgi tendon reflex
Explain the difference between muscle stretch reflex and golgi tendon reflex
Stretch reflex (stimulus = stretch, response = contraction); Golgi tendon reflex (stimulus = tension, response = relaxation). When a muscle spindle is stimulated, the end result is contraction of the muscle. When a goldi tendon organ is stimulated, the end result is relaxation of the muscle (due to inhibition)
Which spinal nerve supplies the biceps?
Presume there has been a LMN lesion affecting the biceps. After 3 months, comment on the changes seen in the muscle
1. Mass is lost (due to lack of trophic action due to lack of ACh released at NMJ) 2. Power is totally lost 3. Tone reduced = flaccid (gamma motor neurons denervated, resulting in relaxation of msucle spindles > no signal to spinal cord or alpha motor neuron action) 4. Related tendon reflexes are lost (because muscle stretch cannot stimulate the motor reflex) 5. Babinski reflex should be normal (plantar flexion)
Explain why there is more atrophy of muscles in a LMN lesions compared with an UMN lesion
Because in LMN, there is loss of mass due to loss of ACh release at the NMJ, which causes lack of tonicity and muscle atrophy (complete termination of trophic action). In an UMN lesion, the UMN loses inhibitory control of the LMNs, leading to over-firing of the LMN and tonicity of the muscle. There is still atrophy due to lack of use, but not as marked as the atrophy due to neuro degeneration (i.e., there is disuse atrophy but not denervation atrophy)
Which 2 factors lead to atrophy of muscle?
1. Trophic action (denervation) 2. Disuse
Maintenance of tone of a muscle is primary dependent on acitivty of?
Gamma motor neuron
Explain why there is muscle rigitidy in a UMN lesion
UMN lesion = over-firing of LMN > over firing of gamma motor neurons > muscle spindle becomes stretched > give more sensory input to spinal cord > excessive stimulation of alpha motor neurons (i.e., alpha motor neurons are overstimulated by stretch reflex but also via disinhibition of gamma motor neurons)
Explain why there is hyperreflexia in UMN lesions
UMN inhibitory control is lose > gamma and motor neurons over-fire > hammer tap will cause excessive overfiring and excessive stimualtion of alph amotor neurons > produce a lot of ACh and reflex becomes exaggerated
Describe the location of the exit point of CN III (occulomotor) in the brainstem
At the level of the superior colliculus in the front of the midbrain, on the medial side of cerebral peduncle and moves anteriorly
Describe the location of the exit point of CN IV (trochlear) in the brainstem
At the level of the inferior colliculus in the midbrain at the back (this is the only spinal/cranial nerve exiting dorsally) and wraps around to cerebral peduncle more laterally than CN III
Which is the only cranial nerve which exists from the back of the CNS?
CN IV (trochlear)
The pineal gland is located at the back of which ventricle?
CN V (trigeminal) exits the brainstem at what location?
Anterolateral side of the pons
Describe the exit of cranial nerves in the pontine medullary sulcus from medial to lateral
Most medial is CN VI, then VII more laterally and CN VIII
Which cranial nerves exit the brainstem at the inferior cerebellar peduncle (from superior to inferior)
CN IX, X and XI (cranial part of XI)
Where does CN XII exit the brainstem?
In the medulla between the pyramid and olive
What sort of fibres are attached to the cell bodies of neurons in the anterior grey horn of the spinal cord?
General somatic efferents
What sort of fibres are attached to the cell bodies of neurons in the posterior grey horn of the spinal cord?
General somatic afferents
What sort of fibres are attached to the cell bodies of neurons in the transverse grey horn of the spinal cord?
General visceral efferents and general visceral afferents (sensory fibres are more posterior)
Generally speaking, compare the locations of sensory vs motor nuclei in the brainstem
Sensory are more lateral and motor are more medial (results from opening of spinal cord around the central canal to form the 4th ventricle)
Describe the location of the trigeminal sensory ganglion
Posterior-most part of middle cranial fossa at the tip of the temporal bone
Describe the pathway of the sensory root of the trigeminal ganglion
Lateral part of mid-pons > enters CNS at anterilateral part of mid-pontine area
The motor root of the trigeminal nerve is responsible for which functions?
Muscles of mastication (NOT connected with ganglion)
Where does the motor root of the trigeminal nerve exit the skull? Which other structure exits at this point?
Foramen ovale with the mandibular division of the trigeminal nerve (that has originated from the trigeminal ganglion)
Which is the largest cranial nerve?
Where are the trigeminal nuclei located and what are they called?
Midbrain (mesencephalic nucleus), pons (prinicpal sensory pontine nucleus) and floor of medulla to upper spinal cord (spinal nucleus of V)
What are the names of the fibres coming from the trigminal sensory root and projecting to spinal nucleus of the trigeminal nerve?
Trigeminal spinal tract
Fibres from the trigeminal nuclei end up in what structure? What are these ascending fibres called?
Ventro-postero medial nucleus of thalamus; trigeminal lemniscus (or trigeminothalamic tract)
List the 6 components of the trigeminal system
1. Divisions 2. Ganglion 3. Motor and sensory root 4. Tracts (especially spinal) 5. Nuclei 6. lemnisci
Describe the pathway of the trigeminal lemniscus after travelling through the VPM nucleus of the thalamus
Ascend through posterior limb of internal capsule and end up in posterior central gyrus
General somatic afferents of the trigeminl system carry what sorts of information?
Fine touch (and 2 point discrimination), pain, temperature and proprioception
General somatic afferents of the trigeminl system supply which structures?
Half of head, full face, cranial cavity (anterior and medial cranial fossa), eye, nose and paranasal sinuses, oral cavity, anterior 2/3 tongue and external ear
What is very unique about the myelination of the sensory root of the trigeminal system? What is significant about this?
For about 7mm, the part of the trigeminal root connected with the pons, the myelination is provided by oligodendrocytes (which are usually only present within the CNS). Significance is that diseases which affect myelination in CNS can also effect the sensory root of the trigeminal system.
The external ear is supplied by which 4 nerves?
V, VII, IX, X
What motor supply is the trigeminal nerve responsible for?
Muscles of mastication (temporalis, masseter, lateral and medial pterygoids), tensor tympani (pulls ear drum medially), tensor vali palatini, myelohyoid and anterior belly of digastric muscle
What % of CO goes to CNS?
Vertebral arteries take orogin from which major blood vessel?
Which 2 major systems are responsible for delivering blood to the brain?
Vertebral arteries (basillar/posterior system) and internal carotid arteries (anterior system)
Vertebral arteries travel through which foramina?
Foramina of transverse processes of cervical vertebrae
Describe the pathway of the vertebral arteries supplying the brain, from their origin
Originate from subclavian system, travel upwards and medially and pass through foramina of cervical vertebrae transverse processes. Enter cranial cavity through foramen magnum > must pierce dura mater and arachnoid mater to end up in subarachnoid space. R and L meet at ponto medullary junction to become basilar artery, which travels upward before giving off terminal posterior cerebral arteries at the top of the brainstem (just above level of 3rd cranial nerve region)
All major arteries supplying the brain (carotid system, vertebral system and circle of willis) are present in which area?
Subarachnoid space (and floating in CSF)
Where do the R and L vertebral arteries meet?
Ponto-medullary junction (i.e., after they have entered through foramen magnum)
Once the R and L vertebral arteries meet at the ponto-medullary junction, they move upwards as which large artery?
The basilar artery divides into which terminal branches at the top of the brainstem?
R and L posterior cerebral arteries (PCAs)
The right and left posterior cerebral arteries supply which areas of the brain?
Midbrain, posterior part of cerebral hemispheres
Where does the anterior spinal artery originate?
In front of the medulla from the contributary branches of the R and L vertebral arteries. Moves inferio-medially and combine to form anterior spinal artery which descends in the anterior medial fissure of the spinal cord
What is the origin of the posterior inferior cerebellar artery?
How much of the spinal cord is supplied by the anterior spinal artery?
Anterior 2/3 of the spinal cord
If anterior spinal artery is blocked, what will be the result?
Loses blood supply and undergoes infarction to the anterior 2/3 of the spinal cord at that level
Which arteries carry blood toward the spinal cord to reinforce the anterior spinal artery?
Segmental arteries move medially toward the spinal cord and divide into which divisions?
Anterior reticular artery (reinforce blood flow in anterior spinal artery) and Posterior reticular artery (reinforce blood flow in 2 posterior spinal arteries)
What is the origin of the posterior spinal arteries?
Vertebral artery (either directly or indirectly from posterior inferior cerebellar arteries)
List 3 major arteries that give segmental arteries to reinforce the blood in the spinal arterial system
1. Deep cervical arteries 2. Intercostal arteries 3. Lumbar arteries
What is the most important artery that provides a segmental artery to reinforce the spinal arteries?
Direct supply from aorta > great medullary artery of ADAM niewicz
Which 2 levels of the spinal cord is the weakest area of blood supply in the territory of anterior spinal artery? Why is this clinically significant?
T4 and L1 (this is because main reinforcing arteries are located just below these points). This is clinically significant because these areas are most likley to develop infarction with reduced blood flow to the anterior spinal artery
Which levels of the spinal cord is the weakest area of blood supply in the territory of the posterior spinal arteries?
T1, 2 and 3
What areas are supplied by the posterior inferior cerebellar artery?
Cerebellum and lateral part of medulla
Which artery may originate from beginning of basillar artery or from the vertebral artery in other people?
Anterior inferior cerebellar artery
What areas are supplied by the anterior inferior cerebellar artery?
Lateral part of pons as well as under side of cerebellum
Which long artery may originate from the basilar artery or from the anterior inferior cerebellar artery in others, and goes to supply the inner ear?
Which 2 nerves accompany the labyrinthine artery?
Facial nerve and vestibulocochlear nerve (through internal acoustic meatus to supply inner ear)
Which arteries originate from the basilar artery just below the level of the occulomotor cranial nerve exit?
Superior cerebellar artery
What structures are supplied by the superior cerebellar artery?
Some midbrain and superior cerebellum
The internal carotid artery enters through the ____ canal, moves forward and then turns upward to exit through the foramen ______, reaching the ____ cranial fossa
Carotid; foramen lacerum; medial
Which dural venous sinus is located in the middle cranial fossa? Which important structure runs through this sinus?
Cavernous sinus; internal carotid artery
Describe the pathway of the internal carotid artery, from it's origin
Originates at common carotid artery (where the division of internal and external carotid arteries occurs at the carotid sinus). Moves upward, enters into carotid canal, moves forward (anterior part of carotid canal opens into the foramen lacerum) and arteries moved through the foramen lacerum, then upwards, pierces the dura mater and enters the cavernous sinus. Then moves upward from here (medial to the anterior clenoid process) and then pierces mater again and comes into subarachnoid space
Which branch of the internal carotid artery passes into the orbital cavity through the optic canal?
Which important branch of the ophthalmic artery supplies the retina?
Central retinal artery
What is the origin of the central retinal artery?
Internal carotid artery > ophthalmic artery > central retinal artery
Name one of the signs of anterior carotdi circulation failure
Blindness in one eye due to occlusion of central retinal artery
Which 2 branches of the internal carotid artery travel backward from the internal carotid artery after it has entered the subarachnoid space?
Posterior communicating artery and anterior choroidal artery
Which arterry forms a connection between the the carotid system and vertebral basillar systems?
Posterior communicating artery
What is supplied by the anterior choroidal artery?
Supply choroid plexus of lateral ventricle
What are the 2 terminal arteries of the internal carotid artery?
After giving off posterior communicating artery, ophthalmic artery and anterior choroidal artery, internal carotid artery divides into 2 terminal branches: lateral terminal branch = middle cerebral artery; and anterior terminal branch = anterior cerebral artery
The anterior communicating artery forms a connection between which vessels?
R and L anterior cerebral arteries
Which structures border the circle of willis?
R and L internal carotid arteries, anterior communicating artery, posterior communicating arteries, posterior cerebral arteries
Which structure of the arachnoid mater anchors it to the pia matter?
Connective tissue reticuli
Which cranial meningeal layer is highly vascular?
Name the 2 layers of the dura mater
Periosteal layer and meningeal layer
What is clinically relevant about the periosteal layer of dura mater?
Periosteal layer can become pathologically separated from the skull bone. Meningeal vessels run through this area (between periosteal and meningeal dura meter), and so haemorrhage can occur.
The periosteal layer of the dura mater is tightly connected to the skull bone except for at which normal anatomical structures?
Venous dural sinuses
Within which 2 layers of the meninges do the meningeal arteries and veins run?
Between the meningeal and periosteal layers of the dura mater
Why does an epidural haemorrhage appear as a 'lens' shape on CT?
Because the ligaments between the sutures in the skull will stop the bleed from pogressing part that point (due to tension), so bleed appears long and thin, with distinct end points at the sutures
Describe the appearance of a subdural haemorrhage on CT
Crescent shape (tracks around the skull between dura and arachnoid mater, with little resistance and little pressure = even distribution)
Rupture of bridging/cerebral veins as they approach the dural sinuses causes what sort of haemorrhage?
Bleeding of meningeal arteries and veins causes what sort of haemorrhage?
What is an aneurysm?
Abnormal, irreversible dilation of arterial wall
Why is subarachnoid haemorrhage so diffuse and widespread?
Because the space is full of CSF, so blood can move easily and throughout entire space
Which form of haemorrhage will result in apperance of RBCs in a LP sample?
Which basal ganglia strucutres are considered to be in the clinical slassification?
Caudate nucleus, lentiform nucleus (putamen + globus pallidus), substantia nigra and subthalami
The globus pallidus is divided into which 2 parts?
1. Globus pallidus interna (medial) 2. Globus pallidus externa (lateral)
Which 3 structures make up the corpus striatum?
Caudate nucleus, putamen and globus pallidus (lentiform nucleus)
Which structures make up the striatum/neostriatum
Caudate nucleus plus only the putamen part of the lentiform nucleus
What are the corticonuclear fibres?
Fibres originating in the cortex that serve motor neurons which are present in the brain stem
The cerebellum is embryonically derived from which structure?
Mesencephalon portion of rhomboncephalon (part of the hindbrain)
Which lobe of the cerebellum is most primitive? What is the functional significance of this?
Flocculonodular - most primitive functions - balance of head and eyes
What is the main function of the anterior lobe of the cerebellum?
What is the main function of the posterior lobe of the cerebellum?
Coordination of movement
What is the name given to the longitudinal depression on the posterior surface of the cerebellum?
Cerebellum controlls functions on the ______ side of the body
The area just lateral to the vermis of the cerebellum is given what name?
Intermediate zone or para-vermal area
What is significant about the vermis and paravermal area of the cerebellum?
They are topographically mapped with the head and neck in the centre and the trunk and limbs are represented more . The trunk and axial body is represented in the actual vermis, whilst the limbs extend into the paravermal area. This is significant because if there is a lesion in the centre of the vermis, the motor control in the trunk will be affected (ataxia od axial muscles) but limbs will be spared
The brainstem is related posteriorly to the ____ and ____ ventricle of the brain
Cerebellum; fourth ventricle
The pons rests on which strucure of the occipital bone?
The brainstem is continuous rostralling with the cerebral ____ and _____
Peducles; forebrain (thalamus)
How long is the brainstem?
The trigeminal system information converges on which 3 nuclei?
Spinal trigenimal, principal trigeminal and mesencephalic nuclei
Auditory fibres from the cochlear nerve synapse in the ___ nucleus, which then projects to the opposite )____ ____
Cochlear; inferior colliculus
In which part of the brainstem is the auditory field spatially mapped?
In the inferior colliculi (opposite side to cochelar nerve providing input)
Discuss visual field mapping in the superior colliculus and which layers receive which input
Direct retinal projects to superior colliculus are mapped onto the superficial layers of the superior colliculus. Deeper layers get somatosensory as well as auditory inputs from the inferior colliculus.
What is the purpose of auditory and visual field mapping?
Coordinates eye movements and head/neck movements to accommodate reflex-like responses to external events
Which nucleus is known as the 'gatekeeper' of cardiovscular and cardiorespiratory control?
Where is the solitary nucleus located?
What information is mapped onto the solotary nucleus?
Nerves carrying afferent info (chemoreceptors) about internal environemnt (taste VII, IX; blood chemistry IX and X, gut sensations X)
The solitary nucleus + reticular formation + periaqueductal grey influence what feelings?
Wellbeing, satisfaction, attention and sleep cycles
Circuits in the dorsolateral open medulla regulate what functions?
Cardiovascular control - through HR and arteriolar paripheral resistance (note there are also cells in this area that regulate sympathetic activity in the lateral horn neurons)
What features can be seen on a cross section at the pyramidal decussation?
Crossing of pyramidal fibres, spinal trigeminal nucleus. Dorsal columns still look like the do in the spinal cord, but the nucleus gracillis can now be seen
Where are the medul lary cardiovasular and repiratory control centres located?
What features can be seen on a cross section at the closed medulla?
Axons of neurons coming from the nucleus gracilis and cuneatus sweep ventrally and medially as the internal arcuate fibres - they cross the midline and form the medial lemniscus. Can now see the inferior olivary nucleus and the spinal trigeminal nucleus which appeared in the pyramidal decussation is still visible
What features can be seen on a cross section at the open medulla?
All dorsal column system migrated into medial lemnicus by this point - nothing remains dorsal to the central canal, which open to form the 4th ventricle. Can now see inferior cerebralle peduncles and can still see the inferior olivary nucleus, which arose at the lower level of the closed medulla
Where do the inferior cerebela peduncles takes fibres from?
Dorsal cerebellar and nuneo-cerebellar tracts and from the C/L inferior olivary nucleus to the cerebellum
What is the cerebromedullary bottleneck? Why is it clinically significant?
Many fibres in the pons squeezed into a small space - this is vulnerable due to the way the blood supply is arranged. A lesions in the basillar artery can interrupt supply to almost the entire pons
How is 'locked in syndrome' diagnosed?
Presence of eye movements
Where do the axons from pointine cells go?
Cross the midline and enter the C/L cerebellum via the middle cerebellar meduncle
What features can be seen on a cross section at the pons?
Fibres of the superior cerebellar peduncles can be seen dorsolateral to the 4thventricle
What features can be seen on a cross section at inferior colliculus?
Substantial bigra and cerebral penduncles prominent ventrally. Main feature is the crossing of the superior cerebellar peduncles centrally. The cerebral aqueduct can now also be seen (and the superior cerebellar penuncles are still visible)
Which CN features prominently in the inerpeduncular fossa of the inferior colliculus?
What features can be seen on a cross section at the superior colliculus?
Superior cerebral peduncles have crossed and enter the red nucleus at this level. Fibres of CN III cross thorugh the red nucleus and SCP fibres.
The cerebral peduncles are seen ventrallly in the midbrain and are separated by the ______
Which structures of the ventral midbrain contain all of the descending tracts that originate in the cerebral cortex?
The cerebral peduncles
List at least 4 of the regulatory functions of the reticular formation
1. Respiratory and cardiovascular control 2. Arousal and sleep-wake cycle 3. Control of gait 4. Autonomic
Explain briefly how the reticular formation has a greater range of influence and can effect hundreds of thousands of neurons
Transmitter released into extracellular space, not confined to post-cynaptic cleft > therefore more diffuse
List the 3 distinct groups of cells in the reticular formation and comment on their fucntions
1. Median/raphe - seratonergic 2. Paramedial: magnocellular (upper) and gigantocellular (lower) - motor 3. Lateral: parvocellular - sensory
Describe the inputs and outputs of the solitary nulceus and tract that function as respiratory control
Inputs from CNs carrying information from chemoreceptors (VII, IX and X), also from carotid body (IX) and arotic arch (X); outputs to reticular formation, hypothelamus, thalamus (taste - cortex), parasympathetic and sympathetic nuclei
The respiratory control centre of the brainstem (solitary N and tract) integrates activity of the dorsal respiratory nucleus to influence which respiratory function?
The cventral respiratory nucleus (dorsal to the nucleus ambiguous) regulates which function of respiration?
Which nucleus is the pacemaker of respiration? Where does it get it's input from and what functions does this regulate?
uParabrachial nucleus > input from amygdala and periaqueductal grey matter > increased breathin rate in anxiety states (including fear and pain
Circuit through DMNX (parasympathetics) have what effect on heart rate? What is the name of this response?
Slows heart rate = barovagal response