Week 1 Labs Flashcards
Tracts
ascending and descending systems which connect the spinal cord and brainstem ot hte cerebrum
Cerebellar peduncles
three pairs of axon bundles that relay connections to and from the cerebellum
Three divisions of the brainstem
midbrain, pons, medulla
4-4-4 rule
4 cranial nerves emerge from each: medulla, pons, midbrain and higher
Cranial nerves arising from the medulla
Glossopharyngeal - IX
Vagus - X
Spinal Accessory - XI
Hypoglossal - XII
Cranial nerves arising from the pons
Trigeminal - V
Abducens - VI
Facial - VII
Vestibulocochlear - VIII
Cranial nerves arising from the midbrain or higher
Midbrain:
Ocular Motor - III
Trochlear - IV
Above:
Optic nerve - II
Only sensory modality where in-coming information bypasses thalamus and is carried directly to central cortical structures.
Smell
Where are the sensory/motor cell bodies of all the cranial nerves except I, II, XI?
Sensory - ganglia lying outside the CNS similar to the dorsal roots of spinal nerves
Motor - within the CNS collected into nuclei serving well-defined muscle groups
Role of cerebellum
- coordinating center for the control of movement by modulating the force, speed, and pattern of muscular contraction –> modulates upper motor neurons
- learning motor skills and detecting errors between intended/actual movements
Lower motor neurons
neurons whose axons directly synapse on muscle
Upper motor neurons
neurons whos axons synapse on lower motor neurons and are found in the motor cortices
T/F The cerebellum resides on major sensory and motor pathways.
F
Where does the cerebellum receive information from?
Cerebral cortex, spinal cord, and CN 8.
Three components of cerebellum
- cerebellar cortex
- deep cerebellar nuclei (pair)
- 3 cerebellar peduncles (pairs)
Functional part of the cerebellum that conducts neuronal calculations on in-coming signals
cerebellar cortex
The circuitry of the cerebellar cortex is the same throughout the cerebellum but is divided into functional units based on _______.
the anatomical source of their inputs and targets of their outputs
Three functional units of cerebellar cortex
- corticocerebellum (hemispheres)
- spinocerebellum (vermis and paravermis)
- vestibulocerebellum (flocculonodular lobe)
The spino and vestibulocerebellum receive input from the spinal cord and CN8 via ______.
inferior cerebellar peduncle
The corticocerebellum receives input by means of the ________.
middle cerebellar peduncle
The superior cerebellar peduncle carries ______ signals to the ________ and part of the ______ which projects to the _______.
output; midbrain; thalamus; motor cortices
Blood is supplied to the brain via which two major arteries?
Internal carotid and vertebral arteries.
The vertebral arteries form the ________.
Basilar artery
The Circle of Willis is supplied by which arteries?
Basilar artery and internal carotid artery
The Circle of Willis distributes blood to which principal vessels?
Anterior, middle, and posterior cerebral arteries (also includes posterior and anterior communicating arteries)
*also smaller arteries to the cerebellum, brainstem, and cerebrum
Cerebral veins drain into what structures?
Dural sinuses
In what major vessel does cerebral venous blood return to the heart?
jugular veins
Three brain membranes/meninges
dura, arachnoid, pia
Pia mater
thin layer that covers the contours of the brain –> encloses all but he largest blood vessels
Which structures lie in the subarachnoid space?
in addition to CFS, large cerebral blood vessels and their major branches
What structure produces CSF?
choroid plexus - specialized secretory epithelia located in each ventricle
What structure connects the lateral and third ventricles?
foramen of monro
What structure connects the 3rd and 4th ventricles?
cerebral aqueduct
How does CSF normally escape the ventricular system?
- arachnoid granulations into dural sinuses
2. three apertures in the walls of the fourth ventricle into the subarachnoid space
Epidural hematomas are between what layers?
dura and skull
Subdural hematomas are between what layers?
arachnoid and dura
Arachnoid hematomas are between what layers?
pia and arachnoid
Four major brain lobes
Parietal
Frontal
Temporal
Occipital
Lateral sulcus/Sylvian fissure divides
temporal lobe from the frontal and parietal lobes
Falx cerebri
vertically oriented, midline sheet of dura that separates the brain into two hemispheres
Tentorium cerebelli
two horizontal sheets of dura that originate from the lateral dura; forms the posterior compartment and separates the cerebellum from the rest of the cerebrum
Superior and inferior sagittal sinus
major venous drainages of the brain; superior also has connections with the arachnoid via the arachnoid granulations
Arachnoid mater
middle meningeal layer; delicate, translucent membrane that encloses the entire CNS including the spine
Subarachnoid space
contains CSF; has large pockets known as cisterns
3 cisterns
Cisterna magna
Superior cistern
Interpeduncular cistern
Telencephalon
major portion of the brain specimen covered with sulci and gyri that increase surface area; contains basal ganglia which have motor and cognitive functiosn
Thalamus
large mass consisting of many individual nuclei and is the route by which ascending information reaches the cerebral cortex
Third ventricle geometry
between two thalami; floor is the hypothalamus
Epithalamus
consists of the pineal gland and the posterior commissure
Subthalamus
transitional region between thalamus and midbrain
Pons
contains nuclei for input into the cerebellum as well as brainstem nuclei
Cerebellum
important for balance, coordination, and planning and executing movements
Medulla
contains multiple cranial nerve nuclei and part of the reticular formation
Components of the lateral ventricle
frontal horn, body, occipital horn, temporal horn
Two important apertures
Midline (Foramen of Magendie)
Lateral (Foramen of Luschka)
Longitudinal fissure
midline fissure separates the right and left hemisphere
Corpus callosum
joins the two hemispheres together: rostrum, genu, body, splenium
Frontal lobe
contains the prefrontal cortex –> personality, decision-making, future planning, and other complex concepts;
caudal part –>motor cortex-eye movements, motor memory, and the motor output of speech
Parietal lobe
posterior to central sulcus –> sensory processing and integration + primary somatosensory cortex + integrations of spatial, visual, and auditory
Pre-occipital notch
small sulcus that separates the temporal and parietal lobes from the occipital lobe
Temporal lobe
found ventral to the Sylvian fissure –> memory, language, smell, audition, visual object/facial recognition
Insular lobe
deep plane of cortex that runs parallel to outer cerebral cortex –> primitive (e.g. taste)
Orbitofrontal cortex
above the orbits –> one of three major divisions of prefrontal cortex –> novel decisions + linked to limbic system
Infundibulum
pituitary stalk –> protuberance behind optic chiasm (connects hypothalamus to pituitary)
Mammillary bodies
two small bumps posterior to infundibulum –> memory
Uncus
most medial part of temporal lobe –> herniation from intracrainal pressure (accompanied by CN3 palsy)
Segments of the corpus callosum
Rostrum, Genu, Body, Splenium
Anterior commissure
“white dot” –> connects medial regions of the temporal lobes (uncus’)
Calcarine fissure
in medial occipital lobe –> cortex on upper/lower banks = primary visual cortex
Cingulate gyrus
cortical area important for memory consolidation
Massa intermedia (interthalamic adhesion)
midline within the third ventricle connecting the two thalami
Hypothalamic sulcus
divides the hypothalamus and epithalamus from the thalamus and subthalamus
Pineal gland
region of the epithalamus –> under splenium –> produces melatonin
Posterior commissure
region of the epithalamus –> between pineal gland and anterior portion of cerebral aqueduct –> axons that connect the midbrain nuclei –> pupillary reflex to light
Primary motor cortex
anterior to central sulcus –> movement
Supplementary/premotor cortex
anterior to primary motor cortex –> modulate and plan movements –> movement quality
Frontal eye fields
Brodmann area 8 anterior to premotor cortex –> produces fast eye movements (saccades)
Prefrontal cortex
- lateral = plan formation
2. orbitofrontal = plans based on ethics and morals (ventral)
Broca’s area
ventral frontal cortex –> speech production (language tends to be in the left brain)
Primary somatosensory cortex
posterior to central sulcus –> sensory information from thalamus
Somatosensory and visual association cortex
Posterior to primary somatosensory cortex –> synthesize visual and somatosensory information
Supramarginal gyrus
important for language comprehension and processing
Angular gyrus
language comprehension
Visual association cortex
superior and inferior to the primary visual cortex around the calcarine fissure –> refining the neural representation of visual scenes
Superior temporal gyrus
first gyrus ventral to Sylvian fissure –> auditory processing
Middle and inferior temporal gyri
ventral to superior temporal gyrus –> visual association areas –> refine “what” an object is
Fusiform/inferior temporal gyrus/cortex
multiple gyri between inferior temporal gyrus and parahippocampal gyrus on ventral temporal lobe –> visual association
Parahippocampal gyrus
ventromedial temporal lobe –> memory formation and storage
Wernicke’s area
posterior superior temporal gyrus –> language comprehension
Heschl’s gyrus
primary auditory cortex
Oculomotor nerve (CN3)
exits brainstem from interpeduncular cistern –> controls six extraocular muscles, levator palpebrae, and parasympathetic control of pupil
What is a CN consequence of uncal herniation and how does this present?
CN3 compression –> oculomotor nerve palsy (down and out) + ptosis + dilated pupil
Colliculi
two pairs of bumps on the dorsal surface of midbrain –> along with CN4
Superior colliculus
involved in reflexive head and eye movements in response to stimuli –> receives ascending auditory and somatosensory + retina
Inferior colliculus
obligatory relay nucleus in audition –> sends axons to thalamus//primary auditory cotex and to the superior colliculus
What is the only nerve to emerge from the dorsal surface of the brainstem?
CN4/Trochlear –> caudal to inferior colliculus –> long and tortuous course around cerebral peduncle to posterior region of cavernous sinus –> prone to damage
Divisions of the pons
pontinetegmentum (inner) and the basis pontis (outer)
What nerve emerges from the lateral pons?
CN5/Trigeminal –> exits pons and pierces middle cerebellar penduncle at right angle
Components of the vestibulocerebellum
regulates postural muscles and stability of gaze
- flocculus– tongue-like lateral appendages
- nodulus - internal part of the vermis in the fourth ventricle
Spinocerebellum
modulates movements of large distal muscles –> paravermis
axial muscles –> vermis
Tonsils
bulges of paravermis –> herniation through the foramen magnum can be caused by intracranial pressure
Cerebellar peduncles
- superior = dive into brainstem and form roof of rostral half of 4th ventricle –> mostly output
- middle = input from motor cortex
- inferior = input/output from brainstem and cord
Pyramids
two elevations extending entire length of medulla –> contains axons from the motor cortex/UMN that will terminate with spinal cord for voluntary movement
Inferior Olives
elevations on medulla lateral to pyramids –> major input to the cerebellum
Lenticulostriate arteries
small penetrating branches of the MCA that supply the putamen, globus pallidus, and internal capsule –> sensitive to blood pressure changes and can cause hemorrhagic stroke (no collateral circulation can cause paresis easily)
Posterior inferior cerebellar artery
first major branch of vertebral arteries and supplies choroid plexus, inferior surface of cerebellum, and lateral medulla
Anterior inferior cerebellar arteries
branches of the basilar that supply the anterior/inferior portion of cerebellum and lateral pons
Caudal arteries of the basilar
- superior cerebellar = superior and dorsal cerebellum
- posterior cerebral = rostral supply to occiptal lobe (runs above tentorium cerebelli)
* both supply lateral midbrain
Thalamoperferators
small vessels from tip of basilar and beginning of posterior cerebral arteries that enter the brain via the interpeduncular fossa and supply thalamus/subthalamus
Great Vein of Galen/Great Cerebral Vein
found under splenium –> main draining area of internal cerebrum –> drains into straight sinus
Where do superficial cerebral veins drain into?
superior and inferior sagittal sinuses
The merging of what vessels creates the straight sinus?
inferior sagittal sinus + Great Vein of Galen
Where does the straight sinus drain into?
confluens of sinuses
What vessels arise from the confluens of sinuses?
two transverse sinuses
What neurons are in the intermediolateral cell column?
lateral horn in T1-L2 segments –> preganglionic sympathetics
In what tract do Clarke’s nucleus axons ascned the spinal cord
dorsal spinocerebellar tract –> nuclei between T1-L2 –> proprioceptive input to cerebellum
Where are neurons that act as central pattern generators for locomotion found?
intermediate zone of lumbosacral enlargements
Which nerves are classified by roman numerals?
dorsal roots of muscular nerves are classified by conduction vessels via roman numerals
Which nerves are classified alphabetically?
dorsal roots of cutaneous nerves are classified by fiber diameter alphabetically
Where do Ia and Ib fibers arise?
muscle spindles and golgi tendon organs
Where do II fibers arise?
muscle spindles
What do A-beta fibers innervate?
skin mechanoreceptors
What do A-delta fibers respond to?
sharp pain/cold (free nerve endings)
What do C-fibers respond to?
dull pain/warmth (free nerve endings)
What 3 kinds of axons can exit the spinal cord in a ventral root?
- axons of alpha or LMN for extrafusal muscle fibers
- gamma motor neurons for intrafusal fibers (spindles and golgi)
- preganglionic autonomics (T-L2 and S2-S4)
Role of Renshaw cells
recurrent inhibition limits the firing of alpha motor neurons –> feedback inhibition/sensitivity of alpha motor neurons
Clinical consequence of blocking Renshaw cells
e.g. tetanus –> sustained contractions and spasms of axial and limb muscles
2 lateral system motor tracts
- corticospinal = internal capsule –> decussation of pyramids –> contralateral skilled limb movement
- rubrospinal = red nucleus –> cross below red nucleus –> parallel to corticospinal –> contralateral upper limb flexion
2 medial system motor tracts
reticulospinal and vestibulospinal tracts –> postural control (bilateral)
Which reflex utilizes C5-C6?
biceps brachii
Which reflex utilizes C7-C8?
triceps brachii
Which reflex utilizes L3-L4?
quadriceps/patellar
Which reflex utilizes S1-S2?
gastroc-soleus/ankle jerk
What kind of lesions result in an ipsilateral flaccid paralysis at the level of the lesion?
LMN
What kind of lesions result in an ipsilateral or contralateral spastic paralysis below the level of the lesion?
UMN
Horner’s syndrome
lesion of descending hypothalamic axons between hypothalamus and preganglionic sympathetics in cord –> miosis, ptosis, anhidrosis ipsilaterally (also orthostatic hypotension)
3 P’s of tabes dorsalis
- parasthesia
- pain - hypersensitivity of small diameter axons
- polyuria - loss of large diameter sensory neurons that mediate bladder fullness
A unilateral lesion of the crossed axons of the spinothalamic tract in the spinal cord or brainstem results in a loss of pain and temperature where?
contralateral and below the lesion
If the spinothalamic tract is lesioned in the spinal cord, where is the loss of temperature and pain?
contralateral and begins 1-2 segments below the level of the lesion
Where does the dorsal spinocerebellar tract arise?
Clarke’s nucleus from T1-L2 –> carries proprioceptive input from stretch/golgi in lower limb and lower trunk
Where do 2nd order axons from clarke’s nucleus extend?
they enter the dorsal spinocerebellar track and enter cerebellum via inferior peduncle
Where does the cuneocerebellar tract arise?
primary upper limb spindles/golgi synapse in the external cuneate nucleus (brainstem) and secondary axons form the cuneocerebellar tract that run into the cerebellum via the inferior peduncle
The dorsal roots that synapse in the superficial layers of the dorsal horn are mainly those carrying ___________.
Pain and temperature
Where are primary cell bodies of the corticospinal tract?
contralateral motor cortex
Where are primary cell bodies of the rubrospinal tract?
red nucleus in midbrain
Where are primary cell bodies of the lateral vestibulospinal tract?
ipsilateral lateral vestibular nucleus in medulla
Where are primary cell bodies of the reticulospinal tract?
pons and medulla
