Voluntary Movement Flashcards
What are the 3 types of movement?
- Involuntary actions - reflexes
- Semi-automatic actions e.g. CPGs in breathing
- Voluntary actions
Describe features of voluntary actions
- Self-initiated
- Purposeful: goal directed
- Learned
- Improved with practice
- Adaptable
Describe features of semi-automatic actions
- ‘Voluntary’; but you don’t have to think about them
- Often, they are repeated movement sequences
- Appear stereotyped but are very adaptable
What are some examples of semi-automatic actions?
Walking, breathing, chewing
What are central pattern generators (CPGs)?
Neuronal circuits that produce rhythmic motor actions in the absense of sensory input
What drives semi-automatic actions?
- May be driven by CPGs
- CPGs are specific to the the action they initiate/maintain
Which components are involved in voluntary movement that are not involved in reflexes?
- Recruitment and influences from subcortical areas (thalamus, basal ganglia)
- Also higher processing in cortical areas
What is the motor homunculus?
Map of brain areas dedicated to motor processing for different parts of the body
Where is the primary motor cortex located?
Precentral gyrus (motor neurons here)
What effect(s) can injury/lesion to the spinal cord have on sensory and motor functions?
- Can affect ability to perceive sensory information or to initiate voluntary movement
What is the corticobulbar pathway?
Descending pathway that innervates several cranial nerves
Which 4 cranial nerves does the corticobulbar pathway directly innervate?
Corticobulbar pathway directly innervates the nuclei of the following cranial nerves:
- Trigeminal (V)
- Facial (VII)
- Vagus (X)
- Hypoglossal (XII)
What does CN V3 innervate?
Muscles of mastication
What does CN VII innervate?
Muscles of facial expression
What does CN X innervate?
Soft palate, pharynx, larynx
What does CN XII innervate?
Extrinsic muscles of the tongue
Describe the corticobulbar pathway
- Neurons project from motor cortex through the internal capsule of the brain and down through the brainstem
- Activates lower motor neurons in the brainstem
- Lower motor neurons target motor nuclei for CN V, CN VII, CN X and CN XII.
- These cranial nerves innervate specific muscle groups resulting in contraction
- Innervate muscle groups on both sides of the body
What is the corticospinal pathway?
Descending pathway that innervates spinal nerves
Describe the corticospinal pathway
- Upper motor neurons descend axons down through the internal capsule of the brain and down through the brainstem
- As they progress down, at the level of the medulla, 85% of these axons cross over to the opposite side of the body
- This is called pyramidal decussation
- Motor pathways typically innervate opposite side of body
What can damage to descending pathways cause?
Paralysis or palsy
Nature of palsy depends on location of lesion
Describe the effects of damage to lower motor neurons
- Nerve injury e.g. polio
Inability to initiate any type of muscle contraction - Won’t be able to initiate reflex responses or voluntary responses
Describe the effects of damage to upper motor neurons
- Corticospinal tract, corticobulbar tract
- Doesn’t impact upon ability to generate reflex response as this occurs at spinal level
What does damage to the insular cortex affect?
Emotion, perception and motor control
Describe Bell’s Palsy
- Unilateral event
- Dysfunction of CN VII
- Unsure of underlying causes; may be an inflammatory response
- Dissipates within 2 weeks on its own
- No treatment required
