Neurosciences 18+19
HC 2
Chapter 18
The cerebral cortex and brainstem are part of the upper motor neuron complex which
influence the lower motor neuron circuitry, leading to movement. The cerebral cortex hence
plans and initiates movement – more specifically, the primary motor cortex and the
premotor cortex, both adherent to the frontal lobe. The primary motor cortex resides in the
precentral gyrus, whereas the premotor cortex lies anterior to this. The initiation of
movement in turn is based on input from the thalamus, which relays information from the
basal ganglia and cerebellum. Output it via the pyramidal cells to the spinal cord and
brainstem.
Efferent motor output runs from the cortex, through the capsula interna and pedunculus
cerebri, to the pons, where inferiorly the decussation lies and so where there is a crossing to
the right side of the spinal cord if the motor output originated from the left side. Vital
sensibility detected by afferent sensory neurons experience decussation at the level of the
spinal cord where they entered. So, a sting in your right arm crosses in your spinal cord to
the left side, to notify the sensory cortex of your left hemisphere. Gnostic sensibility
detected by afferent sensory neurons cross at the same level as motor neurons, so just
inferior to the pons.
The basal ganglia contain motor nuclei that modulate movements of the body. There still
are various functionally distinct groups:
- Striatum: this is the input zone of the basal ganglia, as many neurons from various
brain regions end up here, along the corticostriatal pathway.
o Caudate nucleus
Multimodal association cortices
Frontal: motor areas that control eye movements
o Putamen: receives info from
Parietal: primary and secondary somatosensory cortices
Occipital: visual cortices
Temporal: visual cortices + auditory association areas
Frontal: premotor and primary motor cortices
- Pallidum: main sources of output from the basal ganglia, which end up in various
regions of the brain.
o Globus pallidus
o Substantia nigra
For Parkinson’s patients, deep brain stimulation helps gain back control over motor
movements of their limbs. This occurs in the output regions, to stimulating the pallidum.
So, the overall functions of the basal ganglia are hypothesized to be: initiation of
movements; scaling of movements; sequencing of movements; focused selection and
inhibition of competing motor programs.
Chapter 19
The cerebellum, like the basal ganglia, modify the activity patterns of upper motor neurons.
Anatomically, it exists of a laminated layer of grey matter surrounding nuclei buried deep in
HC 2
Chapter 18
The cerebral cortex and brainstem are part of the upper motor neuron complex which
influence the lower motor neuron circuitry, leading to movement. The cerebral cortex hence
plans and initiates movement – more specifically, the primary motor cortex and the
premotor cortex, both adherent to the frontal lobe. The primary motor cortex resides in the
precentral gyrus, whereas the premotor cortex lies anterior to this. The initiation of
movement in turn is based on input from the thalamus, which relays information from the
basal ganglia and cerebellum. Output it via the pyramidal cells to the spinal cord and
brainstem.
Efferent motor output runs from the cortex, through the capsula interna and pedunculus
cerebri, to the pons, where inferiorly the decussation lies and so where there is a crossing to
the right side of the spinal cord if the motor output originated from the left side. Vital
sensibility detected by afferent sensory neurons experience decussation at the level of the
spinal cord where they entered. So, a sting in your right arm crosses in your spinal cord to
the left side, to notify the sensory cortex of your left hemisphere. Gnostic sensibility
detected by afferent sensory neurons cross at the same level as motor neurons, so just
inferior to the pons.
The basal ganglia contain motor nuclei that modulate movements of the body. There still
are various functionally distinct groups:
- Striatum: this is the input zone of the basal ganglia, as many neurons from various
brain regions end up here, along the corticostriatal pathway.
o Caudate nucleus
Multimodal association cortices
Frontal: motor areas that control eye movements
o Putamen: receives info from
Parietal: primary and secondary somatosensory cortices
Occipital: visual cortices
Temporal: visual cortices + auditory association areas
Frontal: premotor and primary motor cortices
- Pallidum: main sources of output from the basal ganglia, which end up in various
regions of the brain.
o Globus pallidus
o Substantia nigra
For Parkinson’s patients, deep brain stimulation helps gain back control over motor
movements of their limbs. This occurs in the output regions, to stimulating the pallidum.
So, the overall functions of the basal ganglia are hypothesized to be: initiation of
movements; scaling of movements; sequencing of movements; focused selection and
inhibition of competing motor programs.
Chapter 19
The cerebellum, like the basal ganglia, modify the activity patterns of upper motor neurons.
Anatomically, it exists of a laminated layer of grey matter surrounding nuclei buried deep in
