Lecture 7.2: Descending Pathways Flashcards
What are the 3 Types of Movement?
1) Reflexes
2) Posture
3) Voluntary Movement
What type of movement do LMNs & Spinal Cord Circuits facilitate?
Reflexes
What type of movement do the Brain Stem & Spinal Cord facilitate?
Posture
What type of movement do the Cortex, Brain Stem & Spinal Cord facilitate?
Voluntary Movement
What Structures is the Motor Cortex comprised of? (2)
What is the Primary Motor Cortex?
- Encodes the Direction of Movement
- Somatopically Organised
- Motor Homunculus
- Head Laterally
- Feet Medially
What is the Role of the Corticospinal Tract?
Conscious control of skeletal muscles
What 3 tracts does the Corticospinal Tract split into? (3)
- Corticobulbar
- Lateral Corticospinal
- Anterior Corticospinal
What is the Corticobulbar part of the Corticospinal Tract responsible for?
Conscious control over eye and face muscles
What is the Lateral Corticospinal part of the Corticospinal Tract responsible for?
Conscious control over limb skeletal muscles
What is the Anterior Corticospinal part of the Corticospinal Tract responsible for?
Conscious control over axial skeletal muscles
What does the Corticospinal Tract descend via?
- Pyramids of the medulla
- 75-90% decussate – mainly distal musculature
- 10-25% don’t decussate – axial
What is the Origin of the Corticospinal Tract?
Primary Motor Cortex
What does the Corticospinal tract synapse onto?
The Ventral Horn
What are the 4 Brain Stem Motor Pathways (Extrapyramidal)?
- Rubrospinal Tract
- Tectospinal Tract
- Vestibulospinal Tract
- Reticulospinal Tract
What is the Role of the Rubrospinal Tract?
- Voluntary control of upper limb motor activity
- Lesions produce minimal effects, demonstrating
overlap
What is the Role of the Tectospinal Tract? (2)
- Orientation and positioning of the head for balance * Eye-head coordination
What is the Role of the Vestibulospinal Tract? (2)
- Head Balance
- Body Posture
- Involuntary
What is the Role of the Reticulospinal Tract? (2)
- Body Posture
- Muscle Tone
Where does the Rubrospinal Tract originate from?
Originates in the red nuclei of the brain stem
Is there full unilateral facial drooping in Bell’s Palsy or a Supranuclear Lesion of the Facial Nerve?
Bell’s Palsy
What is Motor Neurone Disease?
Degeneration of the motor cortex, spinal tracts, anterior horn grey matter & LMNs
What are the Clinical Features of Motor Neurone Disease? (5)
- Stiffness/weakness of the hands spreading distal to
proximal - Fasciculations
- Speech Difficulties
- Swallowing Difficulties
- Slow, Progressive Muscle Wasting – distal to
proximal
What are Fasciculations?
Visible, involuntary twitching of an individual muscle
What is Myasthenia Gravis?
- Disorder of the NMJs
- Autoimmune disease w Abs against acetylcholine
receptors
Clinical Features of Myasthenia Gravis
- Variable Muscle Weakness
- Fatiguability
Diagnostic Tests for Myasthenia Gravis (3)
- Antibodies
- EMG
- Edrophonium Test
Treatment of Myasthenia Gravis (2)
- Cholinesterase Inhibitors (symptomatic)
- Immunosuppression/Thymus Removal
