Neuro Flashcards
What are the main structural divisions of the brain?
Forebrain- prosencephalon (telencephalon (cerebrum) and diencephalon (thalamus and its regions))
Midbrain- mesencephalon (tectum, tegmentum, cerebral peduncles)
Hindbrain- rhombencephalon (metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata))
What comprises the brainstem?
Mesencephalon, pons, medulla oblongata +/- diencephalon
What is the most caudal part of the brain and what are it’s margins?
Medulla oblongata.
Caudal margin= spinal cord
Rostral margin= prominent transverse ridge of the pons
Where can the piriform lobes be found?
Ventral aspect of cerebral hemispheres
The superficial origins of all cranial nerves (except for which one?) are visible on the ventral surface of the brain.
Trochlear nerve (CN IV)
The roof of the skull is the ________
The bones of the brain case include ___________
The membranous fold arising from the midline of the skull roof is the __________
The cerebellum and cerebrum are separated by what?
Calvaria
Frontal, parietal, occipital, temporal, sphenoid and ethmoid
Falx cerebri
Tentorium osseum and tentorium cerebelli
The optic canal lies immediately rostral to what?
The optic chiasm
Describe the position of the pituitary gland.
It lies in the hypophyseal fossa which lies caudal to the optic chiasm on the ventral aspect of the brain
Where can the cochlea and the vestibular apparatus be found?
Housed within the petrous temporal bone
What comprises the ventricular system?
Paired lateral ventricles (one within each cerebral hemisphere)
Third ventricle
Mesencephalic aqueduct
Fourth ventricle
What is the reticular formation? What does it do?
Region of mixed grey and white matter from the medulla oblongata to the thalamus
Modulates HR, BP and resp and protective reflexes (eg. Vomiting) and arousal
Which animals have lissencephalic telencephalons?
Rodents, rabbits, birds
Describe the following 2 landmarks:
Cruciate sulcus
Lateral rhinal sulcus
Cruciate sulcus- transverse groove between frontal and parietal lobes
Lateral rhinal sulcus- separates the rhinencephalon from main part of cerebral hemispheres
What are the three types of cerebral cortex and where do they occur?
Paleocortex- olfactory lobe
Archeocortex- medial aspect of each hemisphere dorsal to the corpus callosum
Neocortex- frontal, parietal, occipital and temporal lobes
What is a choroid plexus?
Tangled networks of blood vessels, Pia and ependyma protruding into the ventricles. It is responsible for the production of cerebrospinal fluid (ultrafiltration of blood plasma)
Describe the flow of CSF. How is it absorbed?
Flow is in a caudal direction through brain’s ventricular system. It leaves the brain via the lateral apertures under the cerebellum which take the csf into the subarachnoid space.
Absorbed by the arachnoid villi as well as by lymphatics around the origins of the cranial and spinal nerves, and veins around the brain and within the meninges.
What are the three layers of meninges from external layer to internal? Between which layers is the epidural space?
Which layer encloses the spinal roots as they leave the spinal cord?
Dura mater, arachnoid mater, Pia mater
Epidural space is external to dura mater and contains fat and vertebral venous plexi
Dura mater encloses spinal roots
What are the leptomeninges?
Arachnoid mater and Pia mater
In which areas is the dura mater folded to form a double membrane?
Falx cerebri (ethmoid bone to osseous tentorium) Tentorium cerebelli (petrosal crest to osseous tentorium) Diaphragma sella (dorsum sella to caudal chinois process of sphenoid bone near optic canal area)
Briefly describe the vascular supply and drainage of the spinal cord.
Supply:
- longitudinal arteries (2 dorsolateral and the ventral spinal artery)
- radicular arteries
- collateral circulation
Drainage:
-internal vertebral venous plexus (on floor of vertebral canal)
Briefly list the main arterial supply to the brain.
- left and right internal carotid
- basilar (continuation of ventral spinal artery)
- > circle of Willis
- rostral cerebral artery (rostromedial half of cerebral hemispheres)
- middle cerebral artery (lateral part and rostral brain stem)
- caudal cerebral artery (caudomedial part)
- rostral and caudal cerebellar arteries
- rostral, middle and caudal meningeal arteries
What is responsible for connecting each lateral ventricle to the centrally located third ventricle?
Interventricular foramina
Where do the lateral apertures of the fourth ventricle occur?
Between the fourth ventricle and subarachnoid space at the level of CNVIII
Describe the two clinically important CSF cisterns.
- Cerebellomedullary cistern (lies between caudal cerebellum and medulla oblongata)
- Lumbar cistern ((caudal end of spinal cord -L7)
List the arrangement of cranial nerves.
Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Auditory (vestibulocochlear) Glossopharyngeal Vagus Accessory Hypoglossal
In regards to the cranial nerves, no nerve is purely sensory but some nerves are purely motor. True or false?
False! No nerve is purely motor but some nerves are purely sensory (I, II, VIII)
Which cranial nerves exit together through the internal acoustic meatus? Why is this important clinically?
CN VII and VIII exit together. Therefore may bothe be affected by otitis externa
Describe the innervation of the pharynx and larynx.
Pharynx:
- sensory CN IX
- motor CN IX and X
Larynx
- sensory CN X and XI
- motor CN X and XI
Which cranial nerves have meningeal coverings which extend out into the periphery?
I, II and VIII
a) Anosmia (lack of smell) can be a sign of dysfunction of which nerve?
b) strabismus (lateral/medial rotation of the dorsal aspect of the eye)
c) balance problems
a) CN I
b) CN IV and CN VI
c) CN VIII
Which cranial nerves may the following signs of dysfunction be associated with?
a) dysphagia and respiratory noise
b) visual and PLR deficits
c) dropped jaw and facial sensory deficits
d) paralysis and deviation of the tongue
a) IX and X
b) II
c) V
d) XII
Which cranial nerves may the following signs of dysfunction be associated with?
a) facial muscle paralysis, decreased lacrimation and taste
b) atrophy/ dysfunction of trapezius, brachio- and sterno-cephalicus
c) PLR deficits and strabismus
a) VII
b) XI
c) III
The sympathetic division of the autonomic nervous system arises from which spinal nerves?
C8 to L3/4
What are the three major ganglia called through which the sympathetic and vagus pass through?
Cervicothoracic (only sympathetic)
Middle cervical
Cranial cervical
Where can the hypogastric nerves be found? What do they supply?
Distal to the caudal mesenteric ganglion. Structures of the pelvis
Where does parasympathetic supply to the head arise?
From the parasympathetic nuclei of cranial nerves III, VII and IX
What does the parasympathetic nucleus of CN III in the mesencephalon supply? (This is called the Edinger-Westphal nucleus) Where does it run?
Supplies the iris and ciliary body.
Travels to the eye via the orbital fissure
What does the parasympathetic nucleus of CN VII and IX supply?
Salivary glands
What are two roles of the parasympathetic nucleus of CN X?
Innervates the pharynx and larynx
Innervates the thorax and abdomen
Touch, pressure and proprioception respond to purely mechanical stimulation and is transmitted in which part of the spinal cord along which tract?
Dorsal funiculus
Fasciculus gracilis and fasciculus cuneatus
Pinprick pain, heat and cold are transmitted in which part of the spinal cord and along which tract? What about deep pain?
Lateral funiculus along the spinothalamic tract
Deep pain: diffusely. Sent to the ascending reticular formation in the brain stem
What is sensory and motor ataxia?
Sensory ataxia= incoordination of motor coordination due to lack of proprioceptive input
Motor ataxia= incoordination of motor action due to lack of UMN input
What are some LMN deficit signs as opposed to UMN deficit signs?
LMN: flaccid paralysis, hyporeflexia, atonia, neurogenic atrophy to specific muscles
UMN: extensor rigidity, hyper-reflexia, general hypertonia, mild generalised disuse atrophy
Name the 5 spinal cord motor tracts that we learnt about and specify where each one originates.
- Corticospinal (motor cortex of cerebrum)- only pyramidal one
- Rubrospinal (red nucleus of the midbrain)
- Vestibulospinal (vestibular nuclei)
- Tectospinal (tectum)
Which tract is found entirely within the spinal cord?
What does it do?
Propriospinal tract
Has ascending and descending fibres for reflex activity within and between spinal cord segments
(Surrounds grey matter)
The fasciculus gracious conveys proprioceptive information to the brain from _______ whereas the fasciculus cuneatus conveys proprioceptive information to the brain from ________
Gracilis: from body caudal to T8
Cuneatus: from body cranial to T8
What is the main tract responsible for carrying pain and temperature sensibility? Does it have ipsi- or contra- lateral projection?
Lateral spinothalamic tract in the ventral part of the lateral funiculus
Both ipsi and contralateral projection
Which pathways are involved in conveying proprioceptive info for posture and adjustment of posture after movement? Do these pathways have contralateral or ipsilateral projection?
- dorsal and ventral spinocerebellar (caudal 1/2 of body)
- cranial spinocerebellar (cranial 1/2 of body)
- spinovestibular (head and neck junction)
- dorsolateral fasciculus
All have ipsilateral projection
What is the major extrapyramidal tract and a major voluntary motor pathway in animals?
Rubrospinal tract
What is the lateral (medullary) reticulospinal tract?
Extrapyramidal tract from the reticular formation of the medulla oblongata.
It is facilitatory to the contralateral proximal flexors. It suppresses standing and other antigravity activities
What is the lateral vestibulospinal tract?
Originates from the lateral vestibular nuclei of the medulla oblongata. It facilitates ipsilateral extensor and inhibits ipsilateral flexors
Always active
What is the medial vestibulospinal tract responsible for?
What about the medial longitudinal fasciculus?
Maintaining balance with head movements
Coordinates trunk movements with head and neck movements
Where does the ventral (pontine) respticulospinal tract originate? What does it do?
Reticular formation of the pons
Maintains standing posture (facilitatory to ipsilateral LMNs of prox extensor muscles)
the eyeball consists of three tunic layers. What are they and what are they comprised of?
- Outer fibrous tunic
- collagenous tissue
- sclera and cornea which meet at the limbus - Vascular tunic (uvea)
- choroid, ciliary body and iris - Retina
- pigmented epithelial layer
- neuroepithelial layer
How does the cornea receive its nutrients? What provides sensory perception to it?
Via lacrimal fluid and aqueous fluid of anterior chamber
Opthalmic branch of CNV
What is the choroid? What does it do? Is it vascular or avascular?
Part of the vascular tunic that lines the sclera from the optic nerve almost to the limbus.
Provides nutrients for outer layers of retina.
It has a vascular and avascular part. Blood vessels are found in the pigmented part of it. It also has an avascular tapetum lucidum dorsally which is reflective/iridescent
What is the ciliary body? What is its role?
Thickening of choroid dorsally. It provides an anchoring point for zonular fibres which suspend the lens. It also produces aqueous humour
The iris is under both parasympathetic and sympathetic supply. Explain this further.
Smooth muscle sphincter responsible for pupillary constriction is under PS supply. the radial muscle responsible for dilation is under sympathetic supply
What are the cells (from outer to inner) comprising the neuroepithelial layer of the retina?
Photoreceptor cells (rods and cones) (Horizontal cells) Bipolar cells (Amacrine cells) Ganglion cells (light hits these first)
What are the roles of rods and cones?
Rods- night vision
cones- colour vision
Which cells of the neuroepithelial layer of the retina feed into the optic nerve?
The ganglion cells
What do horizantal and amacrine cells do?
Horizontal: modify transmission between bipolar and photoreceptor cells
Amacrine: modify transmission between bipolar and ganglion cells
what is the eye lens comprised of? Where does it get its nutrients from?
Epithelial cells and lens fibres
Aqueous and vitreous humour
Where does the aqueous humour drain? Where is it produced?
Into venous sinuses at iridocorneal angle
Cells of ciliary body
Describe the periorbita fascia of the eye
fibrous fascial sheath which blends medially and dorsally with periosteum. Inserts in eyelids and surrounds eyeball and extrinsic muscles of the eye. It also contains smooth muscle which helps to keep the eyeball slightly protruded under normal sympathetic tone
What is the puncta lacrimalia?
Minute slits on the upper and lower lids adjacent to the lacrimal caruncle. They are the openings to the canaliculi leading too nasolacrimal duct.
Lacrimal sceretions consist of 3 layers. What are they?
- outermost lipid layer
- aqueous layer form
- inner mucoid layer
What is the vascular supply of the eye?
External opthalmic artery (from maxillary)
Internal opthalmic artery (supplies CNII)
Venous drainage is via several vorticose veins emerging through sclera
Which nerve innervates the auricular muscles of the pinna?
CNVII
What is the external acoustic meatus?
Canal running from narrow part of auricular cartilage to tympanic membrane
Describe the tympanic membrane?
Thin complete membrane separating external acoustic meatus from middle ear. Fibrous tissue. Attached to osseous tympanic ring. Covered laterally by epidermis and medically by mucosa
The tympanic (middle ear) cavity is connected to the inner ear by…?
The vestibular and cochlear windows
What are the auditory ossicles? What muscles are they associated with?
Malleus, incus and stapes.
Stapedius muscle and tensor tympanum muscle (they act to dampen transmission)
What components comprise the bony and membranous labyrinths of the inner ear?
Bony: vestibule, semicircular canals, cochlea
Membranous: urticaria/ saccule, semicircular ducts, cochlear duct
Which plexus is responsible for control of gut secretion? Which is responsible for control of gut motility?
Submucosal
Myenteric
What layers make up the eyelids?
Skin
Musculofibrous layer (with orbicularis oculi and tarsal glands)
Conjunctiva ( lines posterior surface of eyelids -palpebral- and reflects onto sclera-bulbar)
What is the nerve supply to the eye?
CNII- light perception
CNIII- motor to dorsal, medial and ventral recti; ventral oblique and lavatory palpebrae superioris. PS innervation to iris and ciliary body
CNIV- dorsal oblique
CNV- sensory to eyeball, eyelids and conjunctiva
CNVI- lateral rectus, retractor bulbi
CNVII- motor to orbicularis oculi, lacrimal gland
Sympathetic innervation- periorbita, pupillary dilation (radial m.), eyelids open, and retraction of third eyelid
What is the vestibular system and how does it work (briefly)?
=organ responsible for sensing body position
Movement of cilia towards or away from static kinocilium results on depolarisation or hyperpolarization of hair cell, and excitation or inhibition of firing of neutron at base of hair cell
Describe where the utricle and saccule are located and how they are positioned.
Utricle- base of semi-circular canals. Oriented in horizontal plane
Saccule- ventral to utricle, connected to endolymphatic duct. Oriented in vertical plane
What are maculae?
Sensory hair cells in saccule and utricle which sense static position. They project into the otolithic membrane.
In the semicircular ducts, hair cells are located on (a)… and project into (b)…
a. Crista
b. Cupula