Anatomy W6 - Corticospinal&Corticonuclear Tracts Flashcards
Describe the corticospinal tract.
Where axons from the motor cortex travel through the corona radiata and converge in the internal capsule.
Once passing through the internal capsule they make their way through the brainstem to the lower medulla then desiccate.
Describe the corticonuclear tract.
Where axons from the motor cortex travel to their specific cranial nerve motor nuclei in the brainstem on the same side and on the opposite side.
Describe the course of the fibres within the corticospinal tract.
They cross over (at lower medulla) and supply muscles of the opposite side only!
Describe the course of the fibres within the corticonuclear tract.
They supply both muscles on the same side and muscles on the opposite side (cross over at level of the nucleus.)
Most muscles receive innervation from both sides of the brain.
Exceptions hypoglossal and the fibres of the facial nerve that supply the muscles of the lower face
Between what 2 structures is the internal capsule located?
What tracts pass through here?
The lentiform nucleus - which is a basal ganglia composed of grey matter
The thalamus
What vessels supply the internal capsuel?
The lentiguide striae arteries that come off of the middle cerebral artery which comes off the ICA.
Describe the symptoms a patient with a stroke affecting the internal capsule would present with.
Paralysed lower face - facial nerve
Paralysed tongue - hypoglossal nerve
paralysed upper and lower limb
Extra ocular muscles = unaffected
Muscles of mastication = unaffected
Muscles of pharynx and larynx = unaffected
Describe why damage to the internal capsule causes a paralysed face, tongue and upper and lower limb but the muscles of the eye (extra ocular), mastication and the pharynx and larynx are unaffected.
Muscles in the face such as the extra-ocular muscles and the muscles of the pharynx and larynx are innervated by motor nuclei on both the left and right side of the brainstem
= these muscles still function as if one side is damaged they still have innervation from the other side.
However
The facial nerve (supplying the lower muscles of the face) and the hypoglossal nerve only receive innervation from the nuclei on the opposite side of the brain stem (NOT BOTH SIDES)
= if that side is damaged the muscles lose their function.
What are basal ganglia?
Areas of grey matter which coordinate and smooth out muscle contractions.
Works with the cerebellum
Name the 4 basal ganglia.
Subthalamus
The lentiform nucleus
Substancia nigra
Caudate nucleus
What is the corpus callosum?
C shaped fibres that connect the left and right cerebral hemisphere
What motor nuclei are present in the midbrain?
The oculomotor nuclei (3)
The Trochlear nuclei (4)
What motor nuclei are present in the pons?
The facial nucleus (7)
The trigeminal nuclei (5)
The abducents nuclei (6)
What motor nuclei are present in the medulla?
The hypoglossal nuclei (12)
The nucleus ambiguus (9, 10, 11)
What do the facial, trigeminal and ambiguus nuclei all have in common?
They are all situated further away from the midline of the brainstem since the muscles supplied by these nuclei are formed from pharyngal arches.
