Brainstem 4 Flashcards
[…] results from a problem with a UMN whereas […] results from a problem with a LMN.
Spastic Paresis (weakness)
Paralysis
What are the 3 hierarchical control levels of the CNS and what structures of the brain are in each?
Neural motor pathways can be sub divided into what 2 pathways?
Note: pyramidal also includes corticobulbar pathway
What is the corticobulbar pathway?
Carries information to motor neurons of the cranial nerve nuclei, rather than the spinal cord. These nerves control the muscles of the face and neck.
What layer of the cerebral cortex contains neurons that give rise to corticospinal axons?
5th
- Most axons of the corticospinal tract that convey motor information originate from areas what # areas of the brain?
- Where do the remaining axons originate from?
When picturing a homunculus and the motor cortex, where are the following chunks of motor information?
- Foot to knee
- Thigh to hand
- Face
For cranial nerves 3 - 12, do the UMNs that synapse with these LMNs project ipsilaterally, contralaterally, or both?
All cranial nerves are LMNs. All CNs except for CN 7 have UMNs that project to both the left and right respective nuclei. Ex: the UMN in the corticnuclear tract that synapses with the oculomotor nucleus in the midbrain projects to both the left and right oculomotor nuclei to synapse with both the left and right CN 3.
CN 7 is an exception. The facial nucleus in the pons controls motor movements of muscles of facial expression. The areas of this nucleus that innervate upper facial muscles receive innervation from both left and right UMNs, whereas the areas of this nucleus that innervate lower facial muscles receive innervation from only the ipsilateral UMN.
- What is the extrapyramidal system?
- Where are these tracts found?
- What neurons do they synapse with?
- Are these tracts modulated? If so, how?
- Neural network that is part of motor system that control involuntary reflexes and movements and modulates movement (coordination)
- Reticular formation in pons and medulla
- Neurons in spinal cord involved in reflexes, locomotion, complex movement and posture
- Modulated by parts of CNS
Rubrospinal Tract
- Where does this originate?
- Where does it receive input from?
- What is its function in humans?
- Red nucleus in midbrain
- Area of motor cortex that contributes to corticospinal tract (areas 4 and 6)
- Backup to corticospinal tract, function largely reduced in humans
Vestibulospinal tract
- Where does this tract originate?
- What is its function? (2)
- Lateral or medial vestibular nuclei
- Lateral
- Maintain upright and balanced posture by facilitating extensor motor neurons of legs
- Medial
- Keeps head balanced on shoulders as body moves
Tectospinal Tract
- Where does this originate?
- What does it do?
Pontine reticulospinal tract
- Where does this originate?
- What does it do?
Medullary reticulospinal tract
- Where does this originate?
- What does it do?
Tectospinal
- Superior colliculus
- Keep head balanced as turn it to respond to sensory stimuli
Pontine
- Reticular formation in pons
- Enhance antigravity reflex of spinal cord
Medullary
- Medullary reticular formation
- Liberates antigravity muscles from reflex control (opposes pontine RST)
We have a loop of neurological connections where information cycles from the cortex through the basal ganglia and thalamus and then back to the cortex. What is the function of this loop?
The selection and initiation of willed movements
We have a loop of neurological connections from the motor cortex, somatosensory cortex and parietal cortex that project to the pontine nuclei (striations) which in turn then project to the cerebellum. What is the purpose of this loop?
Once the signal is received by the cerebellum, the cerebellum sends information back to the primary motor cortex on movement direction, timing and force.
The cerebellum is an important site for […].
Motor learning - allows us to correct future movements based on knowledge of how previous movements have gone.
Ex: in a tennis match, an oponnent hits the ball a certain way. The brain signals a response but we fail to return the ball. The next time that same circumstance arises, the cerebellum can try to correct the way the body moves to achieve the desired outcome.
What are the symptoms of UMN lesion? (4)
- Spastic paresis (twitchy but weak muscles)
- Babinski sign (toes fan upward)
- Hyperreflexia
- Hypertonia
What are the symptoms of LMN lesion (5)?
- Flaccid paralysis
- No babinski sign
- Hyporeflexia
- Fasciulations
- Hypotonia
CN 3
CN 4
Left Trigeminal nerve (Mandibular, V3)
Lesion on right Vagus
True or False: The babinski sign is not seen with UMN damage.
False - it is seen (toes fan upward)
