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