neuro important Flashcards
what does the arterial system of the brain originate from ?
internal carotid - anterior portion = 80%
vertebral arteries - posterior portion = 20%
where are berry aneurysms most likely to form?
the junctions/connections between branches in the circle of Willis
roughly what area of the brain does the anterior cerebral artery supply
anterior and middle portion of brain
roughly what area of the brain does the middle cerebral artery supply?
lateral sides of brain
roughly what area of the brain does the posterior cerebral artery supply ?
posterior portion of brain - occipital and some of temporal lobe
what would be the effect of a lesion of the ACA
loss of contralateral motor and sensory functions of lower limbs
what would be the effect of a lesion of the MCA
contralateral motor and sensory functions of upper limbs and face (+ Broca’s aphagia)
what would be the effect of a lesion of the PCA
Vision (leads to opposing side homonymous hemianopia with Macular sparing)
what structures are found in the cavernous sinus
(O TOM CAT) Oculomotor Trochlea Opthalmic Maxilliary Carotid (internal) Abducens (Trochlea)
what is cranial nerve 1 and what is its function
olfactory
smell
what is the pathway of CN I
olfactory epithelium -> olfactory bulb -> olfactory tract -> primary olfactory cortex (+ limbic system)
what type of fibre is CN I (olfactory)
sensory
what is CNII and what is it’s function
Optic
vision and sensory fibre for the pupillary light reflex and accommodation reflex
what type of fibre is CN II (Optic)
sensory
what is CN III and what is its function
Oculomotor
eye movement, pupillary light reflex and accommodation reflex
what type of fibre is CN III (oculomotor)
somatic motor
Oculomotor nucleus -> extraocular muscles except LR6SO4
autonomic motor/parasympathetic
Edinger-Westphal Nucleus -> ciliary ganglion -> ciliary muscles + sphincter pupillae
what is CN IV and what is its function
Trochlear
eye movement - superior oblique
what is the pathway of CN IV
Posterior Midbrain -> exits posteriorly -> loops round anteriorly -> SOF -> SO
what type of fibre is CN IV
motor
what is cranial nerve V and what are its branches
Trigeminal
opthalmic, maxillary, mandibular
describe the pathway of CN V
4 Nuclei along brainstem -> Trigeminal ganglion (Meckel’s cave) -> 3 branches
what kind of fibres make up CN V
Both
motor (muscles of mastication)
somatic sensory (pain, touch, temp, proprioception)
what are the functions of the V1-opthalmic branch of CNV
Somatic sensory: upper face, eyelids, lacrimal gland, and Ethmoid sinus
Autonomic sensory: sensory fibres for corneal reflex
what are the functions of the V2-maxillary branch of CNV
Somatic sensory: maxillary portion of face, upper teeth and lips, and nasopharynx
what are the functions of the V3- mandibular branch of CNV
Somatic sensory: mandibular region of the face, ant anterior 2/3 of the tongue, lower teeth and lips, external ear
Somatic motor: muscles of mastication, Tensor tympani, tensor veli palatini, Mylohyoid, Ant. Belly of DIgastric
what is CN VI and what are its functions
Abducens
eye movement - lateral rectus
describe the pathway of CN VI
Nucleus in pons anterior to facial colliculus -> exits through ponto-medullary junction -> SOF -> LR
what kind of fibres make up CN VI
motor
what is CN VII and what are its functions
facial
Sensory function: taste anterior 2/3 tongue, somatic sensation of external and middle ear
Motor function: Stylohyoid, Stapedius, post. Belly of Digastric, Muscles of facial expression
Autonomic motor function: motor - corneal reflex, lacrimal gland, Nasal gland, sublingual and submandibular salivary glands
what kind of fibres are in CN VII
sensory
motor
parasympathetic
what is CN VIII and what are its functions
vestibulocochlear
sound, balance
describe the pathway of CN VIII
Organ of corti/Vestibular system -> Vestibular ganglion, spiral ganglion-> CN VIII -> IAM -> into ponto-medullary junction lateral to 6 and 7
what is cranial nerve IX and what are its functions
glossopharyngeal
Sensory: Pharynx, soft palate, external ear, posterior 1/3 of tongue, carotid sinus and body
Motor: stylopharyngeus
Parasympathetic: parotid gland
what is the origin of CN IX
3 nuclei in medulla
what fibres does CN IX carry
both motor and sensory + parasympathetic
what is CN X and what are its functions
vagus
Sensory: aortic arch, thoracic viscera, larynx, Abdominal Viscera, External ear and epiglottis (taste)
Motor: muscles of soft palate (swallowing), pharyngeal muscles (swallowing), and Laryngeal muscles (speech)
Parasympathetic: Thoracic viscera, GI tract
what is the origin of CN X
medulla
what fibres does CN X carry
both motor and sensory + parasympathetic
what is CN XI and what are its functions
accessory nerve
Cranial: accessory to CN X in innervating the Pharyngeal muscles
Spinal: sternocleidomastoid, trapezius
what is the origin of CN XI
Cranial component: medulla; Spinal component: C1-C5
what type of fibres does CN XI carry
motor
describe the pathway of CN XI
Spinal component the brain via the Foramen Magnum -> meets up with the cranial component -> exits via the Jugular Foramen
what is CN XII and what are its functions
hypoglossal
muscles of tongue
what kind of fibres does CN XII carry
motor
what is the origin of CN XII
hypoglossal nucleus – medulla
what does the spinal trigeminal nucleus do
Receives sensory innervation from the face (CN V, VII, IX and X)
what is the nucleus ambiguus
Motor nucleus for muscles of the pharynx and Larynx (CN IX, X and XI)
what is the solitary tract nucleus
Taste nucleus (CN VII, IX and X)
describe the anatomy of the outer eye
Sclera (white part of eye)
Cornea (first point of refraction)
describe the anatomy of the middle eye
Iris: contains the sphincter pupillae, dilator pupillae
Choroid
Ciliary body: ciliary muscles and suspensory ligaments
lens
describe the anatomy of the inner eye
Retina: detect light
Outer pigmented layer: contains melnin
Inner neural layer – photoreceptors, light transduction, vit A storage
action of lateral rectus
abduction
action of medial rectus
adduction
action of superior rectus
elevation, adduction and intorsion
action of inferior rectus
Depression, Abduction and extorsion
action of superior oblique
Intorsion, abduction, depression
action of inferior oblique
Extorsion, abduction, Elevation
what are the 2 synergistic pairs of eye muscles
SR + IO
IR + SO
what is the effect of a CN III palsy
Depression and abduction of eye (down and out)
Eye lid drooped down
what is the effect of a CN VI palsy
cant laterally rotate (abduct) eye
what is the effect of a CN IV palsy
eye extorted - appears slightly elevated
what parts of the ear are fluid or air filled
External ear (air-filled) Middle ear (air-filled) Inner ear (fluid-filled)
what are the aspects of the external ear
auricle, external acoustic meatus, tympanic membrane
what is the function of the auricle
directs sound into the external acoustic meatus
what is the function of the external acoustic meatus
Transmits sound into the tympanic membrane
Contains cerumen: prevents pathogens and insects from reaching the tympanic membrane
what is the function of the tympanic membrane
Vibrates in response to sound -> transmits vibrations to ossicles
Separates external ear from middle ear
Attaches onto the Malleus bone
what are the components of the middle ear
ossicles, muscles (stapedius, tensor tympani), eustachian tube, oval window
describe the direction of vibrations through the ossicles
Malleus -> Incus -> Stapes -> Oval window -> inner ear
what does the stapedius do
dampens the stapes to prevent excess vibration in response to loud sound
what does tensor tympani do
tenses the tympanic membrane to prevent excessive vibrations -> dampens loud sounds
what does the eustachian tube do
Tube: connects middle ear to nasopharynx and equalises pressure either side of the tympanic membrane -> Empties middle ear secretions into nasopharynx
what does the oval window do
transfers mechanical vibrations from the middle ear into fluid filled vibrations in the inner ear
what are the components of the inner ear
semi-circular canals, vestibule, cochlea
function of semi-circular canals
Detects changes in dynamic equilibrium
role of vestibule
Utricle and saccule
Detects changes in static equilibrium
components of cochlea
Scala vestibuli
Scala media/Cochlear duct- Organ of Corti
Scala tympani
what is the function of the basal ganglia
Execution of smooth movements – aka. Fine tunes movement plan
Stimulates desirable movement
Inhibits undesirable movement
Modulates movement
what makes up the striatum
caudate nucleus + putamen
what makes up the lentiform nucleus
globus pallidus + putamen
what are the 2 parts of the substantia nigra
Pars Reticularis (SNr) Pars Compacta (SNc)
what is the direct pathway of the basal ganglia
Stimulates desirable movement
what is the indirect pathway of the basal ganglia
Inhibits undesirable movement
what is the nigrostriatal pathway of the basal ganglia
Modulates both direct and indirect pathways => movement amplification
what causes Parkinson’s disease
hypokinetic
inactive substantia nigra compacta
overactivity of indirect pathway, underactivity of direct pathway
what causes huntingtons
hyperkinetic
destruction of cells of the indirect pathway, indirect pathway inhibition, decreased movement inhibition
what are the ascending tracts
DCML
Spinothalamic
spinocerebellar
what does the DCML convey
fine touch, proprioception, vibration
what does the spinothalamic tract convey
crude touch, pain, temperature
what does the spinocerebellar tract convey
unconscious proprioception
what are the descending tracts
corticospinal
corticobulbar
extra pyramidal tracts
what is the corticospinal tract involved in
conscious muscle movement
what is the corticobulbar tract involved in
voluntary movement of face and neck muscles
what are the extra pyramidal tracts involved with
coordination, posture and muscle tone
what do ascending tracts carry
sensory information towards the brain (4 orders of neuron)
what do descending tracts carry
motor information towards the muscles (2 orders of neuron)
describe the pathway of the DCML
- Travels via the ipsilateral side to the nucleus
1. 1st - Dorsal root ganglion, enters posterior column
and ascends
2. SYNAPSE to 2nd.
3. Decussate at medulla
4. SYNAPSE to 3rd in Thalamus
5. Primary somatosensory cortex to 4th.
what does the anterior vs lateral spinothalamic tract convey
Anterior: crude touch and pressure.
Lateral: pain and temperature
describe the pathway of the spinothalamic tract
- 1st - Dorsal root ganglion, enter spinal cord and ascend together
ipsilaterally for 1-2 segments. - SYNAPSE. 2nd order decussate across anterior white commissure
- Split into anterior and lateral.
- Ascend on contralateral spinal cord.
- DOES NOT decussate at medulla. - SYNAPSE in Thalamus to 3rd order.
- Fibres travel to primary somatosensory cortex. - Synapse to 4th order which carry messages to various points in the
cortex.
describe the pathway of the spinocerebellar tract
- First order: dorsal root ganglion into the spinal cord.
- Synapse to a second order neuron.
- Splits and either crosses the spinal cord and goes up the
ventral tract CONTRALATERALLY. Or doesn’t cross and
ascends up the dorsal tract ipsilaterally. - Dorsal into inferior cerebellar peduncle.
- Ventral into superior. Decussates within the cerebellum.
- BOTH END UP IPSILATERAL.
describe the route of the corticospinal tracts
anterior and lateral tracts. 10% stay ipsilateral, 90% decussate at medulla. Supplies musculature of the body
describe the route of the corticobulbar tracts
neurones terminate on the motor nuclei of the cranial nerves
what are the 4 extra pyramidal tracts
vestibulospinal, reticulospinal, tectospinal and rubrospinal