Organisation of the Brainstem and cranial nerves Flashcards
what are the 3 categories of the brainstem function
- cranial nerve functions
- conduit functions
- integrative functions
what are the cranial nerve functions
- brainstem contains function centres that are associated with 11 of the 12 pairs of cranial nerves
- they have sensory and motor functions of the head are carried out by these nuclei
- parasymapthric output originates and special sensory input is processed in these and associated brainstem nuclei
describe what the conduit functions do
- it contains the ascending and descending pathways going to and from the spinal cord carrying sensorimotor information
describe what the integrative functions do
- respiratory and cardiovascular activities
- the maintenance of consciousness, sleep and arousal that occur via the reticular formation that runs throughout the length of the brainstem
what is the midbrain divided into
- superior colliculus
- inferior colliculus
- cerebral peduncle
what does the superior colliculus do
- controls eye movements and direction of visual attention
what does inferior colliculus do
- this is a component of the auditory pathway
what does the cerebral peduncle do
- fibre tracts descending from cortex to brainstem and spinal cord respectively
Describe the structure of pons
- the cerebellar peduncles attach the caudal pons to the cerebellum while throughout the floor of the 4th ventricle is found medially
- the superior cerebellar peduncle is in the rostral pons, is it a major output from cerebellum
- the middle cerebellar peduncle carriers afferent input from the pontine nuclei
- the inferior penduncle is the pathway for inferior olivary nucleus and other inputs to the cerebellum
- basal pons - this is the bridge for which the pons is named, it is composed of transverse and descending fibres and pontine nuclei
- the corticopontine fibres input to these nuclei
- they then send crossing projections to the contralateral cerebellar cortex - enter via the MCP
- CST axons continue thought the basal pons
describe the structure of the medulla
- medially the floor of the 4th ventricle continues at the rostral or open medulla until it closes and forms the central canal
- pyramid - the corticospinal tract in the medulla is compacted into two wedge shaped
- the pyramidal decussation makes the junction of the medulla with the spinal cord
- the olive is a bulge in the rostral medulla on the side of the pyramids containing the inferior olivary nucleus - this is an important projection nucleus to the cerebellum
what 2 midbrains
- rostral midbrain
- caudal midbrain
what does the rostral midbrain do
- it is a motor nucleus linked to cerebellar circuitry through the inferior olivary nucleus
- the substantial nitra is important in motor function and is part of the basal ganglia
- its compact part has dopmaingerigc neurones that degernate in Parkinson’s diseases
what does the caudal midbrain do
- a small group of cells of the pontine nuclei can be found here in the cerebral peduncle as well as corticospinal axons
- the corticopontine and cortiobulbar (to the Brainstem) fibres here
- cerebellar output fibres of the SCP cross travelling rostrally to the red nucleus and thalamus
what are the medial longitudinal fascicles do
- they connect the brainstem gaze centres and the vestibular system allows coordination of eye movements and maintenance of gaze with head movement
what is the periaqueductal gray involved in
- involved in descending pain control and regulation of autonomic functions
what are the two different types of pons
rostral pons and caudal pons
describe the rostral pons
- the superior cerebellar peduncle is prominent in the dorsal brainstem at this level
- the 4th ventricle is formed from the cerebral aqueduct with most caudal periquaeductal gray surrounding it ventrally
describe the caudal pons
- the cerebellum is attached physically here mainly by the middle cerebellar peduncles
- deep cerebellar nuclei contribute efferent axons to the SCP surrounded by the cerebellum at this level
- the 4 ventricle is wide
where is the widest part of the 4th ventricle
- the junction at the pons and medulla
what are the two medulla
- rostra medulla
- caudal medulla
describe the structure of the rostral medulla
- this is the part of the medulla that has the inferior olivary nucleus with crossing internal arcuate fibres entering into the inferior cerebellar peduncle
- at the upper part of it there is the 4th ventricle which cis more caudally forms the central canal
- the spinal nucleus of the trigeminal nerve receives pain and temperature information from the head
describe the structure of the caudal medulla
- extends from the pyramid decussation to the start of the 4th ventricle
- this part of the medulla includes - the dorsal column nuclei - this is made up of the nucleus gracilis and nucleus cuneatus
- from these axis of second order neurones cross as more internal arcuate fibres and then travel in the medial reminisces
- spinothalamic axons are laterally placed similar to their position in the spinal cord
what does the caudal medulla contain in it
- the dorsal column nuclei
- this is made up of the nucleus gracilis and nucleus cuneatus
where do cells using noradrenaline arise from
- locus cerulean in the rostral pons
where do cells using serotonin arise from
sermoning form the midline raphe nucleic
where do cell using acetylcholine arise from
midbrain and pons- lateral tegmenjtum and penculopontien nucleus and the forembrain
what is the midbrain functionally associated with
- auditory, visual and pupillary reflexed and with eye movement
- associated with input from cranial nerves II- IV and VIII
what is the pons functionally associated with
- functions are mastication, eye movement, facial expression, blinking and salivation and equilibrium and adutiton
- cranial nerves V- VII
- nerves VI and VIII joint he brainstem at the pontomedullary junction
where do nerves at the brainstem join
- nerves VI and VIII joint he brainstem at the pontomedullary junction
what is the medulla functionally associated with
- equlibrium and audition, deglutition, coughing, vomiting, salivation, tongue movement, respiratory and cardiovascular function
- cranial nerves VIII- XII
what do second order neurones receive input from
- they receive input from peripheral sensory neurones
where are the primary sensory ganglia found
- found in the peripheral sensory ganglia
what is the sulcus limitans
- this is formed because of the way the neural tube opens at the level of the 4th ventricle
- this is visible on transverse sections
where are the 2nd order sensory neurones found
- lateral to the sulcus limitans
what are the brainstem motor neurones
- they are medial to the sulcus limitans
what is most lateral
somatic sensory nucleic
what is most medial
somatic lower motor neurones
what nucleic is closest to the sulcus limitans
- visceral nuclei
-
what is the significance of brainstem organisation
- neurones with similar functions are brought into close proximity to reduce the amount of neural wiring needed
- if there is a lesion different functions are affected depending on whether the lesion is lateral or near the midline
describe the visual reflex
afferent arch - CNII
efferent arc - CNIII
- brainstem area - midbrain
describe the accommodation reflex
afferent arc - CNII
efferent arc - CNIII
brainstem area - midbrain
describe the doll’s eye reflex
Afferent arc - CN VIII
efferent arc - CNIII, IV, VI
brainstem area - Midbrain/pons
describe the jaw jerk reflex
Afferent arc - CN V3
efferent arc - CN V
brainstem area - pons
describe the blink reflex
Afferent arc - CN V1, CN VIII CNII
efferent arc - CN VII
brainstem area - pons
describe the gag reflex
Afferent arc - CNIX
efferent arc - CN X
brainstem area - medulla
what is the blood supply to the brain
- vertebral basilar posterior cerebral artery system
where do the vertebral arteries fuse
- they fuse to form the basilar this runs on the ventral surface of the pons
what do the PICA and AICA supply
- they supply parts of the brainstem and then run around to get to the cerebellum or other structures
where do vertebral and posterior inferior cerebellar arteries occlusion do
- they effect the medial and lateral medullary syndromes that are caused by occlusion
