biolpsy_12

Lecture Overview

• Biological Psychology 1 - Lecture 12: Motor system

• Instructor: Dr. Richárd Reichardt (reichardt.richard@ppk.elte.hu)

Reflexes: The Basic Units of Behavior

• Sir Charles Sherrington's Research

  • Conducted studies with spinal animals.

  • Proposed that reflexes are the basic units of behavior.

  • Reflexes are:

    • Simple

    • Unvarying

    • Unlearned responses to sensory stimuli (e.g., touch, pressure, pain).

Behaviorism

• Development of Behaviorism

  • Further elaborated on the idea of reflexes in behavior.

• Limitations

  • Complex movements cannot be fully explained by chaining reflexes.

  • Example: Quote "You hissed all my mystery lectures."

The Motor Plan

• Definition: A motor plan (or motor program) includes a complex set of commands to muscles established before behavior begins.

  • Feedback: Movement feedback informs and fine-tunes the motor program, while the basic sequence remains planned.

Movement Fundamentals

• Skeletal System

  • Basis of movement is skeletal structure.

  • Bones are moved via muscles.

  • Articulations (joints) define potential movements.

• Muscle Movement

  • Muscles contract, resulting in the movement of bones relative to each other.

  • Certain muscles (e.g., eyelids, diaphragm) do not pull on bones directly.

Muscle Contraction Mechanics

• Muscle Structure

  • Muscles consist of fibers containing myofibrils.

  • Myofibrils are composed of proteins within muscle cells.

• Neuronal Activation

  • Neurons release neurotransmitters, opening ion channels in muscle cells.

  • Changes in internal ion concentrations (e.g., Ca2+) lead to myofibril contraction.

Somatic Nervous System Involvement

• Muscle Innervation

  • Muscles are innervated by the somatic nervous system.

  • Spinal motor neurons' axons form these nerves, influencing muscle contraction at neuromuscular junctions.

Proprioception

• Muscle Spindle and Golgi Tendon Organs

  • Muscle Spindles: Sensory elements involved in muscle stretch reflex.

  • Golgi Tendon Organs: Sensory receptors in tendons.

  • Receptor Endings: Muscle spindle has primary and secondary sensory endings; gamma motor fibers maintain intrafusal fiber tension.

The Muscle Stretch Reflex

• Function: Muscle spindles signal motor neurons in the spinal cord to contract stretched muscles when detected.

• Neuroscience Discovery

  • This reflex was crucial in understanding neural coding based on action potential rates.

  • Nobel Prize: Sir Edgar Adrian and Sir Charles Sherrington were awarded for these findings in 1932.

Organization of the Motor System

• Hierarchy of Motor Control Systems:

  • Primary and nonprimary motor cortex

  • Cerebellum

  • Basal ganglia

• Innervation:

  • Head and neck muscles from brainstem nuclei.

  • Body muscles from spinal cord neurons.

Innervation Details

• Facial and Neck Muscle Innervation

  • Oculomotor and trochlear nuclei: External eye muscles.

  • Trigeminal nucleus: Jaw muscles.

  • Facial nucleus: Muscles of facial expression.

  • Hypoglossal nucleus: Tongue muscles.

  • Various nuclei associated with larynx, pharynx, and respiratory control.

The Pyramidal Tract

• Representation of Body in Motor Cortex

  • Organized in the primary motor cortex, reflects body areas (elbow, shoulder, hand, etc.).

  • Crucial for motor command executions.

Motor Cortices Functions

• Primary Motor Cortex: Generates motor commands.

• Supplementary Motor Area (SMA): Important for planning internally generated movements.

• Premotor Cortex: Involved in stimulus-guided movement; home of mirror neurons.

Mirror Neurons in Action

• Located in the premotor cortex.

  • Fire before a monkey performs a specific hand/arm movement.

  • Also activate when observing others perform the same actions.

  • Suggests roles in imitation and observational learning.

Extrapyramidal Motor Systems

• Basal Ganglia Role: Determines movement amplitude, direction, and initiation.

• Cerebellum Role: Develops neural programs for skilled, rapid movements.

Interactions Between Basal Ganglia and Cerebellum

• Functionality:

  • Basal ganglia and motor cortex collaborate to initiate/terminate movements.

  • Cerebellum and SMA ensure smooth ongoing activity during movements.

Treatments for Movement Disorders

• Parkinson's Disease: Treatable through deep brain stimulation targeting basal ganglia.

• Paralysis from Spinal Cord Injury: Various treatments in development, including:

  • Stem cell therapy

  • Epidural stimulation

  • Robotic exoskeletons.

Ending Note

• Thank you for your attention!

• This was the last class!