Podcast
Questions and Answers
The main anatomical pathways are primarily responsible for what?
The main anatomical pathways are primarily responsible for what?
- Sensory perception
- Voluntary movements (correct)
- Involuntary reflexes
- Autonomic functions
What is the primary role of the motor pathways?
What is the primary role of the motor pathways?
- Processing visual information from the eyes
- Maintaining the body's homeostasis through hormonal control
- Controlling balance, posture and voluntary movements (correct)
- Regulating sensory input from the skin
What is the effect of UMNs on LMNs?
What is the effect of UMNs on LMNs?
- UMNs are controlled by LMNs.
- UMNs and LMNs operate independently.
- UMNs inhibit the function of LMNs.
- UMNs control the function of LMNs. (correct)
Which of the following best describes the role of lower motor neurons (LMNs)?
Which of the following best describes the role of lower motor neurons (LMNs)?
Damage to the anterior horn of the spinal cord would directly affect which type of neuron?
Damage to the anterior horn of the spinal cord would directly affect which type of neuron?
Skeletal muscles of the head and neck are innervated by which of the following?
Skeletal muscles of the head and neck are innervated by which of the following?
Where are the cell bodies of lower motor neurons (LMN) that innervate the trunk and limbs located?
Where are the cell bodies of lower motor neurons (LMN) that innervate the trunk and limbs located?
Distal limb muscles are typically innervated by LMNs located where in the spinal cord?
Distal limb muscles are typically innervated by LMNs located where in the spinal cord?
Proximal limb and trunk muscles are innervated by LMNs located in what region of the anterior horn?
Proximal limb and trunk muscles are innervated by LMNs located in what region of the anterior horn?
Which of the following cranial nerves is NOT involved in innervating muscles of the head and neck?
Which of the following cranial nerves is NOT involved in innervating muscles of the head and neck?
The Nucleus Ambiguus (a common nucleus) is associated with what cranial nerves?
The Nucleus Ambiguus (a common nucleus) is associated with what cranial nerves?
Which of the following structures directly regulates LMN activity through posture and muscle tone control?
Which of the following structures directly regulates LMN activity through posture and muscle tone control?
Which of the following brain regions is primarily involved in the planning, supervision, and regulation of movement?
Which of the following brain regions is primarily involved in the planning, supervision, and regulation of movement?
What is the primary role of the cerebellum in motor control?
What is the primary role of the cerebellum in motor control?
Where do upper motor neurons (UMNs) originate?
Where do upper motor neurons (UMNs) originate?
The pyramidal pathways primarily originate from which area of the brain?
The pyramidal pathways primarily originate from which area of the brain?
Which of the following is an example of a non-pyramidal upper motor neuron pathway?
Which of the following is an example of a non-pyramidal upper motor neuron pathway?
What is the general function of the tectospinal tract?
What is the general function of the tectospinal tract?
The rubrospinal tract, originating from the red nucleus, primarily influences what?
The rubrospinal tract, originating from the red nucleus, primarily influences what?
The lateral corticospinal tract primarily controls which of the following?
The lateral corticospinal tract primarily controls which of the following?
Where does the corticospinal tract decussate (cross over)?
Where does the corticospinal tract decussate (cross over)?
Which motor deficit would likely result from a lesion in the lateral corticospinal tract?
Which motor deficit would likely result from a lesion in the lateral corticospinal tract?
The anterior corticospinal tract primarily innervates which muscles?
The anterior corticospinal tract primarily innervates which muscles?
What distinguishes the anterior corticospinal tract from the lateral corticospinal tract?
What distinguishes the anterior corticospinal tract from the lateral corticospinal tract?
In the spinal cord, where are the motor pathway neurons for the lower limbs typically located in relation to the upper limbs?
In the spinal cord, where are the motor pathway neurons for the lower limbs typically located in relation to the upper limbs?
Flashcards
Role of motor pathways?
Role of motor pathways?
Neurons that descend from the cortex to control voluntary movements, balance, and posture.
UMN and LMN?
UMN and LMN?
The motor pathway consists of two sets of neurons: Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN). UMNs control the function of LMNs, which directly innervate skeletal muscles.
Lower motor neurons innervate?
Lower motor neurons innervate?
Skeletal muscles of the head and neck are innervated by cranial motor nerves, while those of the trunk and limbs are innervated by spinal motor nerves.
Location of LMN cell bodies?
Location of LMN cell bodies?
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LMN regulation?
LMN regulation?
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Upper Motor Neurons (UMN)
Upper Motor Neurons (UMN)
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Non-Pyramidal Pathways
Non-Pyramidal Pathways
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Lateral Cortico-Spinal Pathway (LCSP)
Lateral Cortico-Spinal Pathway (LCSP)
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Anterior Cortico-Spinal Pathway (ACSP)
Anterior Cortico-Spinal Pathway (ACSP)
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Somatotopic Organisation
Somatotopic Organisation
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Decussation of ACSP?
Decussation of ACSP?
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Primary motor cortex
Primary motor cortex
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Study Notes
Clinical Neuroanatomy of Motor Disorders: Motor Pathways
- Voluntary movements are mediated by anatomical pathways
- Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN) play different roles
Motor Pathways
- Motor pathways facilitate voluntary movement, balance, and posture via control of skeletal muscles
- A motor pathway consists of 2 sets of neurons: LMNs and UMNs
- UMNs control the function of LMNs
- LMNs directly innervate skeletal muscles as the "final common pathway"
Lower Motor Neurons
- Cranial motor nerves innervate the skeletal muscles of the head and neck
- Spinal motor nerves innervate the trunk and limbs
Location of LMN in the Spinal Cord
- Cell bodies of LMNs for spinally innervated muscles are in the anterior horn of the spinal cord
- Distal limb muscle LMNs are located laterally
- Proximal limb and trunk muscle LMNs are located medially
Arrangement of LMN of Cranial Nerves in Brainstem
- LMNs for muscles innervated by cranial nerves reside in motor nuclei of respective cranial nerves within the brainstem
- Oculomotor Nucleus (CN III) controls extraocular muscles
- Trochlear Nucleus (CN IV) controls extraocular muscles
- Trigeminal Motor Nucleus (CN V) controls muscles of mastication
- Abducens Nucleus (CN VI) controls extraocular muscles
- Facial Motor Nucleus (CN VII) controls facial muscles
- Nucleus Ambiguus (CN IX & X) controls pharynx/larynx
- Hypoglossal Nucleus (CN XII) controls tongue muscles
Regulation of LMN
- Supraspinal centers control LMNs
- The brainstem and cerebral cortex provide direct control
- The basal ganglia are for planning, supervision, and regulation
- Cerebellum are for coordination
- UMNs coordinate these supraspinal centers' influence on LMNs
Upper Motor Neurons
- UMNs originate from supraspinal centers
- Multiple UMNs converge to innervate LMNs
- These UMNs form motor pathways
- UMNs originate in the primary motor cortex
- UMNs originate in brainstem nuclei
- Primary motor cortex gives rise to Pyramidal pathways
- Some brainstem nuclei give rise to Non-Pyramidal pathways
Motor Pathways – UMN – Non Pyramidal / extrapyramidal
- Non-Pyramidal pathways from upper motor neurons start from:
- Red Nucleus gives rise to Rubrospinal tract responsible for upper limb flexors and overall precision
- Vestibular Nucleus gives rise to Vestibulospinal tract for posture and balance
- Reticular Nucleus gives rise to Reticulospinal tract which influences lower motor posture, balance, and extensor tone
- Tectal Nucleus gives rise to Tectospinal tract which from the superior colliculus, controls head and eye movements
Loss of Cortical Inhibition on Non-Pyramidal Pwys
- Decorticate posture is due to lesions above the midbrain
- Decerebrate posture is due to lesions in the lower midbrain/upper pons
Motor Pathways – UMN – Pyramidal
- UMNs synapse in the brainstem, forming corticobulbar tracts, or in the spinal cord below, forming corticospinal tracts
- 80% of fibers cross at the midline
- Trunk and proximal muscles get supply from anterior cortical spinal pathway
- Supplies upper and lower limbs
Lateral Cortico-Spinal Pathway (LCSP)
- LCSP controls distal limb muscles and fine motor movement
- Passes through the corona radiata --> posterior limb of internal capsule --> cerebral peduncle --> anterior pons --> medullary pyramid
- At the lower end of the pyramid Axons decussate and run into the lateral white column of the spinal cord
- UL descends to the cervical region
- LL muscle descend to the lumbosacral spine and synapse with LMN
Lateral Cortico-Spinal Pathway (LCSP) - Lesions
- Lesions can disrupt descending fibers from the primary motor cortex
- Damages spinal fibers
Anterior Cortico-Spinal Pathway (ACSP)
- ACSP innervates axial and proximal limb muscles
- Passes through corona radiata → posterior limb of internal capsule → cerebral peduncle → anterior pons → medullary pyramid before descending into the anterior white column without decussating.
Termination of Anterior and Lateral CST
- Lateral Corticospinal Tract (CST) synapses with LMN to distal muscles
- Anterior CST passes into the anterior white column
Anterior Cortico-Spinal Pathway - Lesions
- Motor deficits result from unilateral ACST
- This causes motor weakness on one side and contralateral issues
Location of Motor Pathways in Spinal Cord
- Descending tracts include: Ventral white commissure, Lateral reticulospinal tract, Lateral corticospinal tract, Rubrospinal tract, Medial reticulospinal tract, Ventral corticospinal tract, Vestibulospinal tract, and Tectospinal tract
Somatotopic Organization of Lateral Corticospinal Pathway in Spinal Cord
- Motor pathway neurons are arranged somatotopically
- LL is located more peripherally and the Upper limb UMNs are located more centrally
- Central lesions lead to sacral sparing, less LL muscle involvement
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