Lecture 8: Brain stem Flashcards
What are the structures special to the midbrain, placement and their function
- Tectum: roof of midbrain made of
a) sup colliculus (nuclei with visual pathway (automatic startle response)
b) inf colliculus (auditory system, processing sound) . - Crus cerebri/Basis peduncli: ventral part which brings fibres from the motor cortex to the body
- Substantia nigra just behind it
What is the structure and function of the Tegmentum
Just behind the pyramids, pons and crus cerebri, tegmentum runs throughout the brianstem to the spinal cord.
It contains a lot of tracts and nuclei which bring sensory info to the brain
What are the structures special to the pons, placement and their function
Ventrally is the Pars Basilaris.
It contains pontine nuclei involved in motor control, signalling from the motor cortex to the cerebellum, as well as motor cortex to lmn.
What are the structures special to the medulla, placement and their function
Pyramids on the ventral surface.
The corticospinal tract runs through this (cortex to spinal cord)
What is the steps of passage for the Corticospinal and Corticobulbar spinal tracts and what is their job
Job: Motor control; corticobulbar= face, corticospinal= body
As they travel down these two pathways are separate, Nerves for F, A, T and L (medial to lateral) in homuncular regions all the way
- Both start at the motor cortex in
- Travel through Posterior limb of internal capsule
- Crus cerebri
- Pars Basilaris: bundles of fibres. Corticobulbar tract passes through then synapses with cranial nerves -> facial nerves
- CS tract fibres continue and form the pyramids in medulla
6a) 80% of fibres will decussate in pyramids to form Lateral corticospinal tract (distal muscles)
b) 20 % will continue before decussating at the spinal segmental level for Anterior corticospinal tract (axial muscles)
7. Synapse with LMN
What is the steps of passage for the Dorsal column- medial lemniscus and Spinothalamic tract and what is their job
Job: Sensory info.
DC= fine touch, vibration, proprioception
ST= pain, temperature, itch
1a) DC fibres decussate into tegmentum after synapsing with the dorsal nuclei in the medulla
b) fibres for ST have already decussated in the spinal cord
2a) . DC Fibres pass through tegmentum ventrally, dorsally then laterally up to the thalamus, then cortex
b) ST fibres continue up the tegmentum mostly laterally, adjacent to dc fibres.
What are 3 nuclei found in the tegmentum and what fibres/info do they receive
Medulla:
1) Inferior olive from each side send fibres that decussate before entering Inferior cerebellar peduncle–>cerebellum
Midbrain
2) Red nuclei (ventrally) receives
a) fibres that come out of the superior cerebellar peduncle from cerebellum and
b) fibres from cortex
II). It then sends fibres down to synapse with the inferior olive + rubrospinal tract into spinal cord for unconscious control of upper limbs
3) Periaquaductal grey: group of nuclei involved in pain modulation -
II) sends fibres down to other nuclei in the brainstem (reticular formation -rn) –>
III) then synapse with lam 2 spinal cord
Where are the cranial nerve nuclei 3-12 located in the brainstem
Midbrain: 3-4
Pons: 5-8
Medulla: 9-12
What is the Reticular formation, where is it and what is its function/ associated functions
Intricate system of loosely clustered nuclei (anatomically difficult to find) that extends through middle of tegmentum in all 3 regions.
Job: It is a major integration and relay centre between brain and Spinal cord for coordination of
- reticulospinal tract-(Sleep consciousness, arousal, somatic motor control)
- raphe nuclei (pain modulation)
- GI, resp and cvs function
What are the steps of passage for the Corticopontine tract
- Fibres from the cerebral cortex be in the crus cerebri
- synapse with the pontine nuclei on ipsilateral side
- Fibres from pontine nuclei come out, cross over to the opposite side and then synapse with the cerebellum at the middle cerebellar peduncle
