Neuroanatomy Flashcards
Regions of the brain from caudal to rostral
. Brainstem (medulla, pons, and midbrain) and cerebellum
. Diencephalon
. Telencephalon
What regions make up cerebrum?
Telencephalon and diencephalon
What is considered the axial structure of CNS?
. Spinal cord and brainstem
. Receive and send info from/to periphery through peripheral organs (nerves)
What is considered Supra-axial part of CNS?
. Cerebrum and cerebellum
. Communicate w/ periphery only through axial CNS (besides olfaction)
Spinal cord functions
. Receives primary sensory inputs from receptors in skin, skeletal m. And tendons, and from receptors on thoracic, abdominal and pelvic viscera, sensory input may have spinal reflexes, conveyed higher on neuraxis, or both
. Contains ascending(project to rostral structure) and descending (to spinal motor neurons) fibers
. Contains somatic motor neurons and visceral motor neurons that innervate skeletal and smooth mm.
Ventral (ant.) median fissure
. Ant. Spinal a. Courses here
Ventrolateral sulcus
. 2 of them
. Ventral rootless attach here
Dorsolateral sulcus
. 2 of them
. Dorsal rootlets attach here
. Post. Spinal aa. Located just medial to these
Dorsal (post.) median sulcus
. Less conspicuous than ventral median fissure
Dorsointermediate sulcus
. 2 of them
. Seen only at servical and upper thoracic spinal levels (C1-T6)
. Fasciculus gracilis is med. to this sulcus
. Fasciculus cuneatus is lat. to sulcus
Basic development of spinal cord
. Alar plate gives rise to sensory area of dorsal horn ( receives general somatic and visceral afferent from central process of DRG neurons)
. Neurons give rise to axons of several long ascending sensory pathways
. Basal plate gives rise to motor neurons of ventral horn, axons exit spinal cord to be ventral roots (general somatic and visceral efferent)
Gray matter in pineal cord
. Dorsal and ventral horns and intermediate one where horns meet
. Shaped as an H
Laminae I-VI are from ___
Dorsal horn
Laminae VII from ___
Intermediate gray matter
Laminae VIII and IX from ___
. Ventral horn
. VIII is interneurons
. IX is alpha motor neurons
Lamina X comes from ___
. Midline area of gray matter around central canal
Dorsal horn
. Sensory horn of spinal cords bc it receives DRG neurons
. Substantia gelatinosa (Lamina II) is most distinct structure
. Laminae III and IV are located below the substantia gelatinosa and groups as nucleus proprius
. Laminae V and VI form base of posterior horn
Intermediate zone
. Extends from area of central canal to lat. edge of spinal gray
. Varies in shape at different levels of cord
. Characteristic of lamina VII at thoracic and upper lumber levels and have posterior thoracic nucleus (dorsal nucleus of Clarke) and lateral horn that contains nuclei assoc. w/ GVA or GVE
Ventral horn
. Motor horn
. Alpha motor neurons are GSE and form ventral roots of spinal n. To then directly innervate skeletal m.
. Lamina IX has alpha motor neurons but also gamma motor neurons that innervate muscle spindles
. Large motor neurons are organized into 2 general but overlapping patterns: cells innervating prox. Muscle are med. and cell innervating distal mm. Are progressively lat. 4
Regions of white matter
. Posterior funiculus
. Lateral funiculus
. Anterior funiculus
. Each is composed of individual tracts/fascicule
. Part of anterior white commissary and posterolateral tract (Lissauer’s tract)
Posterior funiculus
. Btw post. Median sulus and median edge of post. Horn
. Contains only ascending tracts (epicritic touch and conscious proprioception)
. Above T6 has gracilis and cuneatus fasciculi (both together referred to as posterior columns)
. Below T6 is just fasciculus gracilis
Lateral funiculus
. Located btw posterolateral and ventrolateral sulci
. Contains both ascending and descending tracts
. Dorsal to ventral: dorsal spinocerebellar tract, lat. corticospinal tract, rubrospinal tract, ventral spinocerebellar tract, anterolat. System
Dorsal spinocerebellar tract (DSCT)
. Carries unconscious proprioception to cerebellum
Lateral corticospinal tract (LCST)
. One of the important descending tracts from motor cortices to influence spinal motor neurons to make movement
Rubrospinal tract (RST)
. Descending tract for parallel processing info from motor cortex to spinal motor neurons
. Located just ventral to LCST
Ventral spinocerebellar tract (VSCT)
. Carries unconscious proprioception to cerebellum
Anterolateral system (ALS)
. Carries pain and temp to sensory subcortical and cortical areas
Anterior funiculus
. Located btw anterolat. Sulcus and ventromed. Fissure
. Contains both ascending and descending but is primarily descending
. From lat. to med.: part of ALS, reticulospinal (RST) and vestibulospinal (VST) tracts (descending in charge of controlling involuntary movement), ant. Cortocospinal (ACST) tract
Anterior white commissure
. Located on ant. Midline btw central canal and ventral median fissure
Posterolateral tract (tract of Lissauer)
. Small bundle of lightly myelinated and unmyelinated fibers capping the posterior horn
Cavity of spinal cord
. Central canal
. Caudal continuation of ventricular system of the brain
. Continuous w/ the 4th ventricle
Spinal nerves
. Formbed by junction of the post. And ant. Roots of spinal nn.
. Each nerve contains GSA and GVA from DRG, and GSE and GVE from motor neurons in ventral horn
Brainstem region locations
. Spinal cord is continuous w/ medulla (spino-medullary junction)
. Medulla is continuous w/ pons (Ponto-medullary junction)
. Pons is continous w/ midbrain
. Midbrain is continous w/ diencephalon (mesencephalic-diencephalic junction)
Brainstem regions from dorsal to ventral
. Tectum: dorsal to ventricular cavity
. Ventricular cavity: 4th ventricle (medulla/pons)/mesencephalic aqueduct (midbrain)
. Tegmentum: ventral to ventricular cavity
. Appended structure: most ventral area, occupied by white matter fibers connecting brainstem to other area of CNS
Gray and white matter distribution in brainstem
. Gray matter is divided into clusters or neurons (nuclei) hat are sparse w/in white matter
. Gray matter includes nuclei proper and nuclei assoc. w/ cranial n.
Nuclei proper
. Host neurons in charge of specific functions (relay stations from ascending and descending pathways)
. Mostly involved in circuits w/ CNS w/ no projections to the PNS
Nucleus associated w/ cranial nerves
. Either receive sensory inputs from afferents or are site of origin (where body of motor neuron is) of efferent directed to smooth do skeletal mm. Of head and neck
. Projections to/from nuclei are not always w/in CNS and can become part of PNS
. Found w/in tegmentum and are close to the ventricle
. Sensory nuclei more later. Compared w/ motor
. Visceral nuclei are in mid position compared to somatic
Alar and basal plates in brainstem
. Alar plates shift more lateral compared to the basal plates
Structures present in ventral surface of medulla
. 2 pyramids
. Pyramidal decussation
. 2 olives
. Hypoglossal, accessory, vagus, and glossopharyngeal nn.
Pyramid in medulla
. Located on either side of ventral median fissure
. Represent the corticospinal tracts
Pyramidal decussation
. Occurs at spinomedullary junction
. Majority of fibers in corticospinal tract decussate to enter contralateral spinal cord
Olive in the medulla
. Large, oval swellings lat. to the pyramids on both sides
. Represent the inf. Olivary complexes
Location of CN XII in medulla
. Exits medulla btw olive and pyramid in postolivary sulcus
Location of CN XI in medulla
. Exits medulla lat. to olive in postolivary sulcus
. Occupy caudal portion of postolivary sulcus
. Only the cranial portion is in medulla, not spinal portion
CN X location in medulla
. Exits in postolivary sulcus
. Rootlets interposed btw CN IX ands XI
CN IX location in medulla
. Exits in postolivary sulcus
. Rostral portion of postolivary sulcus
Dorsal surface anatomy of caudal/closed medulla
. . Central canal of spinal cord persists
. Fasciculus gracilis and fasciculus cuneatus begin to synapse on nucleus gracilis and nucleus cuneatus
. Small protrusions on dorsal surface (gracile tubercle and cuneatus tubercle) mark site of nuclei
Dorsal surface anatomy of rostral/open medulla
. Central canal opens into space o the diamond-shaped 4th ventricle
. Junction of central canal and 4th ventricle is the obex
. Dorsal surface of medulla forms floor of 4th ventricle (rhomboid fossa)
. Several protrusions and grooves made by underlying nuclei and tracts in medulla evident in rhomboid fossa
Internal anatomy of medulla
. Contains nuclei proper, nuclei of cranial nn., and ascending/descending tracts
. From caudal to rostral: spinomedullary junction (transition from spinal cord to medulla), caudal medulla (caudal to obex), and rostral medulla (rostral to obex)
What makes up nuclei proper?
. Reticular formation
. Inf. Olivary complex
. Nucleus gracilis
. Nucleus cuneatus
Ascending tracts pathway to medulla
. Originate from spinal cord gray matter (anterolat. System, post. And ant. Spino-cerebellar tracts) and from sensory neurons assoc. w/ DRG (facliculus gracilis and cuneatus) continue into medulla
Descending tracts pathway to medulla
. Originate from cerebral cortex (corticospinal), midbrain (rubrospinal and tectospinal) and pons (reticulospinal and vestibulospinal)
.traverse medulla en route to spinal cord
. Medulla contributes additional fibers to the last 2 fiber tracts
. Corticospinal tract traverse medulla ventrally (appended structures) forming the pyramids
Spinomedullary junction
. Still has central canal, dorsomedian sulcus and ventromedian fissure
. Rostrally has decussation of pyramids
. Gray matter enlarges and new nuclei appear
. Substantia gelatinosa becomes spinal trigeminal nucleus
. Lissauer’s tract becomes spinal trigeminal tract (lat. to spinal trigeminal nucleus)
. Fasciculus cuneatus/gracilis end and their respective nuclei begin dorsal to central canal
. ALS fibers continue as spinal lemiscus
. Dorsal and ventral spinocerebellat tracts stillthere in ventrolat. Position w/in tegmentum
. Can see caudal extent of reticular formation
What occurs at decussation of the pyramids?
. Majority of fibers decussate here to become lat. corticospinal tracts in lat. funiculi of spinal cord
. Descending fibers from cerebral cortex destined to terminate in contralateral ventral horn of spinal cord
Hypothalamic-autonomic tract (HAT)
. Descending pathway from hypothalamus to brainstem autonomic nuclei
. Located in same general area as spinal lemniscus in lat. medullary tegmentum
Caudal medulla
Rostral to spinomedullary junction, caudal to obex
. Central canal does not open to 4th ventricle yet
. Spinal trigeminal nucleus and tract still seen
. Nucleus gracilis/cuneatus both seen
. Most faciculus gracilis is already terminated in nucleus, but some fasciculus cuneatus is still there dorsal to it’s nucleus
. Mid-lat. tegmentum has 3 ascending spinal lemniscus, post. And ant. Spinocerebellar tracts
. Med. lemnischi on top of pyramids ventral o central canal separated by ventromed. Fissure
. Core of tegmentus: reticular formation, internal arcuate fibers
Internal arcuat fibers
. Arise from neurons in nucleus gracilis and cuneatus
. Fibers course ventromed. Direction through medullary tegmentum
. Cross the midline to form contralateral medial lemniscus
Rostral/open medulla
. Central canal enlarges so 4th ventricle seen
. Pyramids, med. lemniscus, spinal lemniscus, ant. And post. Spinocerebellar tracts, and spinal trigeminal nucleus and tracts still there
. Reticular formation has central core of tegmentum
. Inf. Olives lat. to med. lemnischi and dorsal to pyramids
. Many nuclei at inf. Border of 4th ventricle
. Dorsolat. Aspect of medullary tegmentum represented by inf. Cerebrellar peduncles (restiform bodies)
. Med. and dorsal longitudinal fasciculus/le exist
Nuclei in rostral medulla from medial to lateral
. Hypoglossal nucleus . Dorsal motor nucleus of vagus . Nucleus of solitary tract and solitary tract . Vestibular nuclei . Cochlear nuclei . Nucleus ambiguous
Hypoglossal nucleus
. Fairly large, round shaped nucleus
. Hosts motor neurons that give rise to GSE component of CN XII
Dorsal motor nucleus of the vagus
. Immediately lat. to hypoglossal nucleus
. Gives rise to GVE component of CN X
Nucleus of solitary tract and solitary tract
.lat. to dorsal motor nucleus of vagus
. Pale staining w/ fiber tract (tract of solitary nucleus) running right through center
. Giving this nucleus a “bull’s eye” appearance
. Receives visceral afferent (GVA and SVA) info from CNS VII, IX, and X
Vestibular nuclei
. 4 different nuclei: sup., inf., med., lat.)
. Receives special sensory afferent (SSA) from Scarpa’s ganglion assoc. w/ vestibular component of CN VIII
. Complex of nuclei at border btw medulla and pons
. Only med. and inf. Nuclei present in rostral medulla
Cochlear nuclei
. 2 nuclei: dorsal and ventral
. Recessive SSA from ganglion of corti assoc. w/ acoustic division of CN VIII
. Located dorsolat. To And ventrolat. To inf. Cerebellar peduncle respectively
Nucleus ambiguous
. Located dorsal to inf. Olivary complex, med. to spinal lemniscus, and ventral to spinal trigeminal nucleus
. Very difficult to see in myelin stained sections
. Nucleus gives. Rise to special visceral efferent (SVE) Enron’s that contribute to CNS IX, X, and XI
Medial longitudinal fasciculus (MLF)
. Located immediately ventral to hypoglossal nucleus along midline of medullary tegmentum
Dorsal longitudinal fascicule (DLF)
. Just dorsal to hypoglossal nucleus
. Looks like eyebrow above hypoglossal nucleus
Ventral surface anatomy of pons
. Basilar pons: numerous fiber tracts and some nuclei that function in motor system
. Vestibulocochlear n. (2): enter pons at lat. aspect of pontomedullary junction at pronto cerebellar angle
. Facial n. (2): enters/exit med. to CN VIII
. Abducens n. (2): exits at pontomedullary junction lat. to midline
. CN V: enters/exits lat. aspect of pons by coursing through middle cerebellar peduncle
Basilar sulcus
. Shallow groove in midline of basilar pons that carries basilar a.
Dorsal surface anatomy of pons
. Visible when cerebellum is removed
. Corresponds to sup. Triangle of rhomboid fossa
. Most dorsal aspect (tectum) defines floor of 4th ventricle
. Several protrusions and grooves made by underlying nuclei/tracts in pons evident in fossa
. Facial colliculi prominent in caudal pons and represent fibers of CN VII looping over CN VI nucleus
Internal anatomy of pons
. Most ventral aspect is basilar pons
. Has pontine tegmentum that hosts nuclei assoc. w/ CNS
. Rostral continuation of reticular formation and many ascending and descending pathways
. Major ascending pathways: med. lemniscus, spinal lemniscus, ant. Spinocerebellar tract)
. Descending pathways: many tracts originated from cortex or subcortical structures and directed to brainstem and spinal cord (corticospinal tract, corticobulbar tract, rubrospinal tract, and med. longitudinal fasciculus)
Basilar pons
. Contains some proper nuclei of pons (pontine nuclei, sup. Olivary nuclei)
. Contains massive bundle of fibers that course in several directions
. Most oriented horizontally (from side to side) and continue posterolat. In middle cerebellar peduncle
. Has corticospinal, corticobulbar, and corticopontine fibers
. Transverse pontine fibers (Pontocerebellar) course lat. and end forming the middle cerebellar peduncle, some pontine nuclei can be detected in transverse fibers
Regions of pons
. Caudal pons
. Mid pons
. Rostral pons
Caudal pons location and landmarks
. Rostral to pontomedullary junction by facial motor neurons
. 4th ventricle: anatomical boundary btw pons, ventral to pons and cerebellum, dorsal to cavity
. Most cerebellar deep nuclei can be identified dorsal to 4th ventricle
. Region ventral to ventricle is tegmental subdivision, most ventral aspect of pons occupied by basilar pons
. Border btw basilar pons and ventral tegmentum from med. to lat. has med., spinal, and lat. lemnischi
. Lat. to lat. lemniscus is ant. Spinocerebellar tract
. Has core of tegmentum
How are fibers of medial lemniscus organized?
. In a bundle
. Mediolaterally oriented while in medulla they were dorsomedially oriented
Core of tegmentum on caudal pons
. Reticular formation, DLF and MLF white matter structures seen on both side of midline ventral to 4th ventricle
. Ventral to facial motor nucleus is sup. Olivary nucleus
. Dorsal closer to inf. 4th ventricle border has nucleus from cranial nn.
Nuclei from cranial nerves in caudal pons
. Abducens nucleus: med. in dorsal pontine tegmentum w/ GSE, some nerve fibers seen
. Facial motor nucleus: ventrolat., gives rise to SVE of CN VII, nerve fibers seen
. Spinal trigeminal nucleus and tract: lat. in pontine tegmentum, med. to middle cerebellar peduncle and lat. to facial n. Fibers, give off GSA from face
. Vestibular nuclei: 2 of 4 (sup., lat.) present and receive SSA neurons assoc. w/ CN VIII
Pathway of facial n. Fibers in caudal pons
. Axons leave nucleus and travel dorsomedially
. Loop around abducens nucleus to form genu of facial n.
. Axons exit pons at cerebellopontine angle, med. to CN VIII
Midpons location and landmarks
. CN V exits pons
. Corticospinal tract, corticobulbar tract, coerticopontine tract, transverse pontocerebellar fibers, med., spinal., and lateral lemniscus, MLF and DLF, and middle cerebellar peduncles still seen in this section
. Nuclei proper can still be seen
. Lat. to 4th ventricle has sup. Cerebellar peduncles and Ant. Spinocerebellar tract is post. To them
. Nuclei form CNS housed here
Pathway of fibers in an. Spinocerebellar tract in mid pons
. Fibers travel through sup. Cerebellar peduncle to reach cerebellum