brainstem and cranial nerves Flashcards
what is between the forebrain (prosencephalon) and spinal cord
brainstem
3 parts of brainstem
medulla (myelencephalon), pons (metencephalon) (components of the rhombencephalon/hindbrain) midbrain (mesencephalon)
midbrain fucntion
processes, visual, auditory data. Maintains consciousness (also reflexive somatic motor responses
pons function
relays sensory information to cerebellum and thalamus
medulla function
relays sensory information to thalamus. Contains autonomic centres for regulation of visceral function (cardiovascular etc…)
brainstem functions
conduit, cranial nerves, integration centres, reticular formation
how does brainstem act as a conduit
long tracts to or from spinal cord pass through brainstem.
what are the cranial nerve functions in the brainstem
sensory/motor input and output for the head plus parasympathetic motor output. Cranial nerves carry special senses, brainstem coordinates reflexes involving them.
hpw does brainstem act as an integration centre
relays to cerebellum
what is the reticular formation
interconnected nuclei throughout the brainstem
what do the reticular formation mediate
Autonomic control of important respiratory/cardiovascular reflexes.
Somatic/autonomic modulation via descending pathways
Important in regulation of consciousness.
3 main landmarks of midbrain
superior colliculus
inferior colliculus
cerebral peduncle
what does the superior colliculus in the midbrain do
visual reflexes
what does the inferior colliculus in the midbrain do
auditory relay
what does the cerebral peduncle in the midbrain do
tracts descending from the cortex through the brainstem to the spinal cord (corticospinal)
what are the 3 cerebral peduncles of the pons
superior
middle
inferior
superior cerebral peduncle
main output path from the cerebellum to the midbrain.
middle cerebral peduncle
afferent input from pontine nucleus (motor activity)
inferior cerebral peduncle
inferior olivary nucleus to cerebellum (in medulla)
landmarks of pons
superior middle and inferior cerebral peduncles, 4th ventricle, basal pons
what is the basal pons
bridge of transverse and descending fibres
where is the 4th ventricle
medial pons and medulla
landmarks of medulla
4th ventricle, pyramids, olives
where does the inferior olivary nucleus project
cerebellum
what is in the dorsal part of the brainstem
cranial nerve nuclei
are motor cranial nerve nuclei medial or lateral in the brainstem
medial
are sensory cranial nerve nuclei medial or lateral in the brainstem
lateral
are mixed cranial nerve nuclei medial or lateral in the brainstem
middle
what is in the middle part of the brainstem
ascending and reticular formation
what is in the ventral part of the brainstem
descending motor pathways
are cranial nerves on the ventral or dorsal surface of the brainstem
ventral
where do CNs arise from
nuclei
which CNs are midbrain
1-4
which CNs are pons
5-8
which CNs are medulla
9-12
3 types motor nuclei
somatic, branchial, visceral
where do somatic motor nuclei project to
skeletal muscle
where do branchial motor nuclei project to
muscles derived from branchial arches (jaws, facial expression, larynx, pharynx, neck
where do visceral motor nuclei project to
origin to preganglionic fibres that contribute to the cranial parasympathetic outflow. These fibres end in peripheral ganglia. Postganglionic fibres arising in those ganglia (peripheral ganglia) supply the smooth muscles and glands.
somatic motor nuclei
3, 4, 6, 12
visceral motor nuclei
10 3
visceral sensory nuceli
nucleus of the solitary tract
somatic sensory nuclei
5, 8
what does the sulcus limitans separate
motor and sensory nuclei in the brainstem
Spinal Accessory
Enters cranial cavity via foramen magnum and exits via the jugular foramen. Motor neurons giving rise to accessory: separated fragment of the long column of nucleus ambiguus`
Vagus
Branchial motor innervation of palate, pharynx, larynx: arise from nucleus ambiguus.
Parasympathetic outflow: to heart and digestive system comes from dorsal motor nucleus of vagus
Afferents from lungs and gut: travel in vagus nerve mediating reflexes (swallowing, coughing). Visceral afferent information is processed in the nucleus of the solitary tract.
Glossopharyngeal
mainly sensory, but is parasympathetic secretormotor to parotid gland. Main function: detect taste of things behind mouth, secrete saliva into mouth. Has touch fibres, gag reflex.
Vestibulocochlear
conveys special senses of audition (hearing) in its cochlear portion and perception of self-motion, head position, spatial orientation. Nerve enters brainstem at junction of medulla and pons.
facial
motor supply to muscles of facial expression
Five somatic divisions: mainly branchial motor.
Parasympathetic secretormotor: superior petrosal nerve (nasal secretion and lacrimation).
Taste afferents: from the anterior 2/3 of the tongue (travel from chorda tympani) 🡪 via the geniculate ganglion to the rostral nucleus of the solitary tract.
Medial longitudinal Fasciculus (
tract that connects cranial nerve nuclei controlling eye movements
what does the medial longitudinal fasciculus signal to
vestibular system to keep the eyes balanced when the head moves
input to Medial longitudinal Fasciculus
vestibular nuclei.
what does Medial longitudinal Fasciculus become when it enters the spinal cord
medial vestibulospinal tract
what does the medial vestibulospinal tract do
acting on motor neurons in neck to coordinate reflex head and neck movements
Pupillary Light Reflex
Light: sensory input 🡪 axons of retinal ganglion cells in CNII.
Synapse in pretectal nucleus (midbrain).
Bilateral innervation of Edinger-Westphal nucleus (CNIII)
E-W nuclei send output to both ciliary ganglia which cause constriction of pupils via sphincter pupillae muscles.
reticular formation function
Core of interconnecting neurons. Integrates/filters inputs, modulates both high brain centres and lower spinal sensory and motor systems. Regulates consciousness.
what does lateral reticular formation do
afferent input from all sense
what does medial reticular formation do
efferent output to midbrain, cerebellum etc
what does midline reticular formation do
acilitatory or inhibitory (filtering pain inputs)
what does the reticular formation contain
modulatory systems that have a widespread output to hypothalamus, cortex and limbic system, as well as descending projections
what NTs do reticular activating systems use
monoamines and ACh
where does output from the reticular formation go
hypothalamus, cortex and limbic system, as well as descending projections
what NT does the Pepunculopontine nucleus use
ACh
what NT does the Substantia Nigra use
dopamine
what NT does the Ventral Tegmental Area use
dopamine
what NT does the Locus Coeruleus use
adrenaline
what NT does the Raphe Nucleiuse
serotonin
what does the substantia nigra control
movement initiation
what does the ventral tegmental area control
organising behaviours, attention, reward, motivation
what does the locus coeruleus control
ympathetic nervous system control centre (descending fibres activate preganglionic sympathetic, ascending activates CNS in fight or flight)
what does the raphe nucleus control
arousal, cognition, mood, pain perception
