Control of Motor Function Flashcards
Define cortical initiation of motion
regulation of complex movements; rhythmic movements & central pattern generators
What are the direct activation (voluntary) pathways?
Corticospinal tract for non-head & corticobulbar pathway for head
Describe the corticospinal tract. Where do the axons decussate?
- for non-head
- (UMN) motor cortex (medial) → (LMN) spinal cord ventral horn
- decussate in the medulla at the pyramids
Define myotomse
areas of muscle are innervated by a particular spinal nerve root in a pattern analogous to sensory innervation in dermatomes. Thus, motor innervation maps to the motor homunculus in the cortex
Motor neurons innervate in ___ for head or ___ for non-head & go out through spinal nerves to appropriate myotomes
brainstem
spinal cord ventral motor neurons
Most of your motor control is in your
Hands
Describe the corticobulbar pathway
- for head
- Each side of the motor cortex innervates the motor nuclei on BOTH sides of the midline
- (UMN) motor cortex (lateral) → (LMN) brain stem, cranial nerve, motor nuclei
Face above eyebrows is ___ innervated; eyebrows & below are only___ innervated
bilaterally
contralaterally
What is the indirect activation (involuntary) pathway?
Extrapyramidal tract (nonhead)
Describe the extrapyramidal tract
- involved w/ posture & balance
- Upper motor neurons are in brainstem
- Axons travel down ipsilateral medial white matter on ventral side of spinal cord to innervate ventral lower motor neurons bilaterally
___ pathway can override the ___ pathway
direct activation
indirect
___ coordinates order of muscle contraction
Basal ganglia
5 Basal ganglia we need to remember
Caudate nucleus
Putamen
Globus pallidus
Amygdala
Substantia nigra
The subcortical nuclei of the basal ganglia are in
forebrain (deep cerebrum) & midbrain
___ controls timing of contractions as the motor act is executed to coordinate muscles across multiple joints: fine motor control in response to sensory input
Cerebellum
The cerebellum uses sensory input to modify movements according to ___
environment
The cerebellum acts in response to
Proprioceptive input
Define central pattern generators
Neural connections in local CNS that control fictive (rhythmic) movements w/o conscious command
- also called “black box” of neurons
___ can override reflex & say to stop chewing
Cortex
For walking, ___ & ___ input from the ground modifies stepping direction, speed & force
proprioceptive & mechanoreceptive
2 examples of central pattern generators. Where is there CPG located?
- Chewing cycle - CPG in brainstem at the Obex
- Walking - CPG in the spinal cord
Trauma to ___ or their axons causes loss of function
motor neurons
What happens if you have an upper motor neuron lesion?
- Spastic paralysis
- Moderate muscle atrophy
- exaggerated reflexes
What happens if you have a lower motor neuron lesion?
- Flaccid paralysis
- No movement (reflex or voluntary)
Position of a lesion within a tract determines
which side of the body will be affected
What is multiple sclerosis caused by? What happens? Can it be healed?
- Caused by autoimmune destruction of CNS myelin
- Starts w/ motor function loss, both corticospinal & extrapyramidal
- Somatosensory & autonomic involvement w/ progression
- Can’t be healed
What is amyotrophic lateral sclerosis (Lou Gehrig’s Disease)? Death is caused by what? ___% of cases are hertiable?
- Progressive upper & lower motor neuron degeneration in brain & spinal cord
- Loss of voluntary control, progressing to loss of autonomic motor control
- Death usually from respiratory failure
- Mostly sporadic, but 5-10% of cases are heritable
What causes parkinson’s disease? What does it result in?
- Degeneration of dopaminergic neurons in the substantia nigra
- Loss of motor function, characterized by tremors at rest
What does cerebellar ataxia result in? What are deficits caused by?
- Loss of coordination in movements (Loss of balance, coordination of eye & arm movements)
- “zombie walk”
- Intention tremors
- Deficits caused by a lesion are ipsilateral to site of lesion
What is Huntington’s Chorea caused by? What does it result in?
- Caused by mutations in HTT gene (autosomal dominant inheritance)
- Characterized by uncoordinated, jerky movements & spasms, often involuntary & appearing as restlessness
What is Tardive Dyskensia caused by? What does it result in?
- Caused by certain antipsychotic medications
- Characterized by repetitive, involuntary movements, especially the face (Ex: tongue movements, eye blinking)
Function of frontal lobe
Execute functions, thinking, planning, organizing, & problem solving, emotions & behavioral control, personality
Function of motor cortex
Movement
- Brodmann area 4
Function of sensory cortex
Sensation
Function of parietal lobe
Perception, making sense of the world, arithmetic, spelling
Function of occipital lobe
Vision
The primary motor cortex contains UMNs or LMNs for voluntary or involuntary movements
UMNs for voluntary movements
The brainstem in the CNS contains UMN for involuntary movements & LMN for head or non head voluntary movements
Head
The spinal cord contains UMNs or LMNs for head or non-head
LMNs for non-head
Which cranial nerve is the only one that doesn’t decussate?
CN XI
Function of the temporal lobe
Memory, understanding, & language
