OCB03-2006 Flashcards
What makes up the hindbrain?
Pons
Cerebellum
Medulla
What is an alternative name for the midbrain?
Mesencephalon
What makes up the brainstem?
Midbrain and hindbrain
What is the diencephalon made up of?
Thalamus
Hypothalamus
What is the reticular formation responsible for and where is it found?
Arousal, cardiovascular and respiratory centres/roles
Found at level of medulla
Where is the raphe nucleus found?
Midline of brainstem
Where is the locus coeruleus nucleus found and what is its significance?
At level of pons in brainstem
Centre of noradrenergic pathways
What are the raphe and locus coeruleus nuclei mainly responsible for?
Mood
Sleep
Where is the substantia nigra found?
At level of midbrain, ventromedially
What is the function of the substantia nigra and its clinical importance?
Movement control
Loss of dopaminergic neurons => Parkinson’s disease
Where is the centre of all dopaminergic pathways?
Ventral tegmental area and substantia nigra
How does the dorsal surface of the brainstem differ at the level of the closed and open medulla?
Closed medulla = rounded
Open medulla = flaps/concave
Why is there a “closed” and “open” medulla?
Medulla becomes open when the central canal opens superiorly into the fourth ventricle
Describe the gracile fasciculi.
Ascending pathways for fine touch and conscious proprioception or vibration
Synapse at level of closed medulla with gracile nuclei
Dorsal and more medial than cuneate fasciculi
Describe the cuneate fasciculi.
Ascending pathways for fine touch and conscious proprioception or vibration
Synapse at level of closed medulla with cuneate fasciculi
Doral and more lateral than gracile fasciculi
Describe the medullary pyramids.
Contain axons of corticospinal tract (motor)
Main pathway in voluntary control of limbs
Ventral
Axons cross over at level of closed medulla = “decussation of pyramids”
What fills the central canal of the medulla?
CSF
Which cranial nerve nuclei are found at the level of the closed medulla?
Accessory nerve nuclei medially
Trigeminal nerve spinal nuclei laterally
What is the hole found dorsally at the level of the pons?
Cerebral aqueduct
What is the function of the axons running horizontally at the level of the pons?
Pontocerebellar fibres
Take motor info from pontine nuclei to cerebellum through basilar pons and middle cerebellar peduncle
Where do corticobulbar tracts originate and terminate?
Cortex to cranial nerve motor nuclei
What is the periaqueductal grey and why is it important?
Grey matter around the beginning of the cerebral aqueduct
Important in pain control
What is the importance of the superior and inferior colliculi?
Responsible for reflex eye movement (connected to extraocular muscles)
Superior colliculi = in response to visual stimuli
Inferior colliculi = in response to sound
What are the structures that indicate the position of the midbrain?
2 bumps = superior and inferior colliculi
What are the cerebral peduncles?
2 big blocks of white matter ventrolaterally at level of midbrain
Mainly descending axons
What is the position of the substantia nigra relative to the cerebral peduncles?
Medial
What gives the substantia nigra its name?
Neuromelanin
Is the substantia nigra grey or white matter?
Grey matter
Which part of the autonomic system has associations with cranial nerves?
Parasympathetic
What is the clinical significance of the brainstem housing cranial nerve nuclei?
Cranial nerve testing can be used to look at brainstem integrity
What is the function of the first cranial nerve?
Carries special sensory info responsible for olfaction/smell
Describe how information about smell reaches the brain.
Olfactory neurons present in olfactory epithelium and synapse within the olfactory bulbs
Second-order neurons extend through olfactory tract to olfactory cortex
What is the function of the second cranial nerve?
Vision
Where is the optic nerve?
Area between retina and optic chiasm
What cells does the optic nerve arise from?
Retinal ganglion cells which project axons back as optic nerve to the optic chiasm
Describe how visual information reaches the brain.
Optic nerve extends from retina to optic chiasm
Axons of nasal retinae decussate, temporal retinae axons stay ipsilateral at optic chiasm
Axons travel as optic tract to lateral geniculate nucleus
Most axons synapse in lateral geniculate nucleus of thalamus to travel to visual cortex
Why do only the nasal retinae axons decussate?
Allows formation of stereoscopic image
What will a lesion of one optic nerve cause?
Loss of sight from that eye
What will a lesion of one optic tract cause?
Loss of half the visual field in each eye
Where does the optic tract start?
Optic chiasm
What are the functions of the oculomotor nerve?
Somatomotor to 4 extraocular muscles
Parasympathetic to pupillary muscles (light reflex) and ciliary muscles (accommodation reflex)
Where does the parasympathetic aspect of C.III arise from?
Edinger-Westphal nucleus/accessory oculomotor nucleus
Which is the thickest cranial nerve?
Trigeminal nerve (C.V)
What is the function of the trochlear nerve?
Innervate superior oblique muscle
To depress and laterally move eyeball
What gives the trochlear nerve its name?
Innervates the superior oblique muscle which has a tendon running through a small ligamentous “pulley” called the trochlear
What is the function of the abducens nerve?
Innervates lateral rectus
To abduct the eyeball (move laterally)
If both eyes are looking to the left, which nerves will be acting on each eye?
Left eye will be abducting => abducens (C.VI)
Right eye will be adducting => oculomotor (C.III)
What are the general functions of the trigeminal nerve?
Somatosensory from almost all head and neck
Motor to muscles of mastication
Describe the parts of the trigeminal nucleus responsible for different sensory information.
Spinal nucleus = pain or temperature
Principal/chief nucleus = fine touch and conscious proprioception
Mesencephalic nucleus = unconscious proprioception
What sensory info is the spinal nucleus responsible for?
Pain and temperature
What sensory info is the principal/chief nucleus responsible for?
Fine touch and conscious proprioception
What sensory info is the mesencephalic nucleus responsible for?
Unconscious proprioception
What is the path of information from the trigeminal nucleus to the somatosensory cortex?
Travels up to synapse at the ventral postero-medial nucleus of the thalamus
What do each of the trigeminal branches supply (generally)?
Ophthalmic/V1 = forehead and upper parts of orbit
Maxillary/V2 = inferior parts of orbits and cheeks
Mandibular/V3 = lower jaw and tongue
What are the general functions of the facial nerve?
Somatosensory to eardrum and skin of external auditory meatus
Special sensory = taste to anterior 2/3 tongue, palate
Motor to muscles of facial expression
Parasympathetic to all salivary glands except parotid, lacrimal glands
What is another term for muscles of facial expression?
Mimetic muscles
What causes Bell’s palsy?
Lesion of lower motor neuron of facial nerve (after leaving motor nucleus)
What is Bell’s palsy?
Lesion of lower motor neuron of facial nerve
Causing paralysis of one side of the face
What is another term for Bell’s palsy?
Peripheral facial palsy
What is central facial palsy caused by?
Lesion of upper motor neuron of facial nerve (corticobulbar tract)
What is central facial palsy?
Lesion of upper motor neuron of facial nerve
Causing paralysis of lower part of half the face
What is another name for central facial palsy?
Corticobulbar palsy
Why does an upper facial motor neuron lesion only paralyse the lower part of half the face?
Facial nerve is paired so won’t affect other side of face
Upper parts of face receive info from both hemispheres so allows for compensation
What are the functions of the vestibulocochlear nerve?
Vestibular branch monitors balance, position, movement
Cochlear branch monitors hearing
Where does the cochlear branch of C.VIII arise from?
Organ of Corti
Where does the vestibulocochlear nerve enter the brainstem?
Pontine angle (junction of pons, medulla and cerebellum)
What are the functions of the glossopharyngeal nerve?
Special sensory = taste to posterior 1/3 tongue
Sensory to posterior 1/3 tongue and oropharynx
Motor to muscles of upper pharynx
Parasympathetic to parotid gland
Visceral sensory in measuring blood pCO2 and pH via carotid body
What are the functions of the vagus nerve?
Somatosensory to mucous membranes of laryngopharynx, larynx, upper trachea
Visceral sensory to trachea, lungs, carotid sinus, abdominal veins, gut
Somatic motor to lower pharynx and upper oesophageal muscles
Parasympathetic to cardiac muscles, smooth muscle of GI tract, trachea and bronchi
Where does the spinal accessory nerve arise?
C1 to C4/5
What are the functions of the accessory nerve?
Innervates muscles associated with head and shoulder movement
Sternocleidomastoid = turning and depressing head
Trapezius = shrugging
What is the function of the hypoglossal nerve?
Somatomotor to intrinsic muscles and most extrinsic muscles of tongue
How does the hypoglossal nerve arise?
As a series of rootlets from the medulla
What are the two special nuclear groups in the brainstem formed by more than one cranial nerve?
Nucleus ambiguus
Nucleus tractus solitarius
What cranial nerves contribute to the nucleus ambiguus and what is the function of this nucleus?
Glossopharyngeal and vagus nerves
Motor supply to larynx, pharynx and upper oesophagus
Important in reflexes like swallowing, vomiting, phonation and coughing
What cranial nerves contribute to the nucleus tractus solitarius and what is the function of this nucleus?
Facial, glossopharyngeal and vagus nerves
Visceral sensory supply from tongue, carotid sinus, GI tract, trachea and bronchi
Important in taste, chemoreception, gut distention and blood pressure monitoring
Which special nucleus can be referred to the “main chemoreceptive centre of the brain”?
Nucleus tractus solitarius
