upper motor system

Movements: Simple reflexes characterized by brief muscle activation, including examples like: - Eyeblink - Hiccup - Finger twitch
Acts: More complex, sequential movements, such as: - Honking your car horn - Writing your name - Playing lead guitar
Motor Plan/Motor Program: A predefined set of muscle commands established before the action occurs. - Important Note: Most of the brain's activities are motoric in nature, involving: - Preparation to move - Execution of movement - Corrections to movements as needed.

Descending Pathways: Classified into motor and descending (efferent) pathways, visually represented in red in diagrams.   - Pyramidal Tracts:     - Lateral corticospinal tract     - Anterior corticospinal tract   - Extrapyramidal tracts: Include:     - Rubrospinal tract
    - Reticulospinal tracts
    - Olivospinal tract
    - Vestibulospinal tract
Anatomical Regions: - Sacral - Lumbar - Thoracic - Cervical
Pyramidal Tract (PT): Initiates voluntary movements.
Extrapyramidal Tract (EPT): Involved in involuntary reflexes and movements.

Skeletal System and Muscles: Responsible for powering movement.
Spinal Cord: Controls skeletal muscles directly.
Brainstem: Integrates motor commands received from the cortex.
Primary Motor Cortex: Initiates commands for action.
Nonprimary Motor Cortex: Engages in cortical processing for more complex interactions.
Cerebellum and Basal Ganglia: Provide fine-tuning of motor commands and movements.

Descending Systems: - Upper Motor Neurons: Located in the Motor Cortex; responsible for planning, initiating, and directing voluntary movements. - Brainstem Centers: Facilitate basic movements and manage postural control. - Non-Motor Areas: Support overall coordination but do not initiate movement. - Corticospinal Tract: Connects motor areas and lower motor neurons, integrating with the basal ganglia and spinal interneurons for movement coordination. - Cerebellum: Involved in the timing, coordination, and precision of movements.

Motor Pathways: - Lateral White Matter: Involves: - Axons from motor cortex facilitating skilled movement. - Distal muscles involved in skilled movements. - Medial White Matter: Involves: - Axons from brainstem affecting posture and balance. - Axial and proximal limb muscles.
Key Points About Muscle Control: - Local circuit neurons in the intermediate zone of the spinal cord are arranged topographically, with: - Medial controlling axial muscles. - Lateral controlling distal limb muscles.

Pyramidal Systems: - Components: Include the motor cortex, basal ganglia, cerebellum, thalamus, descending to brainstem and spinal cord. - Functionality: Involved in the direct control of voluntary movements. Damage here results in muscle weakness, especially for limbs.
Extrapyramidal Systems: - Components: Include brainstem paths (e.g., rubrospinal, reticulospinal) and spinal cord connections. - Functionality: Involve involuntary control of reflexes and finer modulation of movement. Damage leads to movement control impairment.

Key Areas:   - Frontal Lobe
  - Parietal Lobe
  - Occipital Lobe
  - Temporal Lobe
Key Features: - Central Sulcus: Divides the frontal and parietal lobes. - Cingulate Gyrus and Sulcus: Median aspects of the frontal lobe, playing roles in emotion and cognition.

Key Regions: - Premotor Cortex and Supplementary Motor Cortex: - Involved in planning and executing voluntary movements. - Activity in these areas relates significantly to complex finger movement sequences.
Homunculus Representation: - Derived from the work of Wilder Penfield during the 1930s, illustrates which parts of the motor cortex correspond to various body regions: - Example of areas represented include shoulders, arms, legs, and head.

Layer 5 Neurons: - Comprise upper motor neurons and include special types such as Betz cells responsible for fine motor control.
Corticospinal Pathway: - Initiates voluntary movements connected primarily through the corticobulbar (upper face) and corticospinal tracts (limbs).

Pyramidal Tract: - Consists of axons from various motor areas, leading through structures like the internal capsule and cerebral peduncle, terminating in specific brainstem nuclei.
Corticobulbar and Corticospinal Projections: - Control muscles of the face, head, neck (corticobulbar) and torso, limbs (corticospinal).
Decussation: - Occurs primarily at the medullary pyramids, where 90% of fibers of the lateral corticospinal tract cross to the opposite side for control, while 10% of fibers remain in the ventral corticospinal tract.

Lower Motor Neuron Lesions: - Cause total ipsilateral loss of facial expression due to damage to facial nuclei.
Leisoning Primary Motor Cortex: - Results in contralateral loss but can see partial compensation due to collateral projections from the cingulate cortex.

Lateral Corticospinal Tract: 90% decussates at medullary pyramids.
Ventral Corticospinal Tract: 10% of fibers remain on the same side, controlling proximal limb muscles.

Purpose: - Controls involuntary reflexes and modulates overall movement for coordination.
Indirect Pathways Include: - Colliculospinal, Reticulospinal, and Vestibulospinal tracts involved in posture, balance, and locomotion.

Brainstem Functions: - Balance, posture, gaze fixation, and reflex controls affecting neck muscles. - Influences axial and proximal limb muscles.
Pathways Include: - Vestibulospinal for posture/balance and orienting movements, and reticulospinal for muscle control during postural adjustments.

Symptoms Include: - Loss of cortical suppression of reflexes, presenting a Babinski sign indicating loss of descending control over reflex arcs. - Normal findings in infants (developing reflex control).

Pyramidal Pathways: Facilitating voluntary movements via the corticospinal and corticobulbar tracts to motor neurons in the spinal cord or brainstem.
Extrapyramidal System: Governs involuntary reflexes and modulated movement tendencies, with pathways targeting spinal reflexes, locomotion, and posture control, integrated with CNS structures like the basal ganglia and cerebellum.