EXSS3062 Week 3 Lecture 1

Slide 1: Introduction

• Course: EXSS3062 – Motor Control & Learning (MC3)

• Topic: Acquiring Information – Sensory Proprioception

• Definition: Proprioception plays a key role in coordinating, guiding, and adjusting movement to produce skilled performance.

• Quote: “The experience of our world, our reality, comes from sensation!” – Prof. Stephen Cobley

Slide 2: Acknowledgment of Country

• Acknowledges the traditional custodians of the land where the University of Sydney stands.

• Respects and honors Indigenous people who continue to care for the land.

• Artwork: Yanhambabirra Burambabirra Yalbailinya by Luke Penrith.

Slide 3: Copyright Notice

• Material is protected under the Copyright Act 1968.

• Only for use by University of Sydney students.

Slide 4: Assessment 1 – Lecture Quiz (Week 3)

• Availability: Quiz opens after the lecture, closes before the Week 4 lecture.

• Format: 3 multiple-choice questions (MCQs) on Motor Control & 3 on Motor Learning.

• Attempts: Two allowed; highest score recorded.

• Weighting: 5% of the total mark, contributing to 30 points across quizzes.

Slide 5: Key Learning Objectives

1. Explain how movement control depends on sensory afferent information integrated with efferent activity.

2. Identify sources of sensory afferent input:

• Golgi Tendon Organs (GTOs)

• Joint Receptors

• Efference Copy

Slide 6: Sensory Input & Motor Control

• Sensory (Afferent) Systems: Provide feedback on body movement.

• Efferent Motor System: Sends commands for movement execution.

• Proprioception Components: Includes muscle spindles, GTOs, joint receptors, cutaneous receptors, vestibular apparatus, vision, and efference copy.

Slide 7-10: Golgi Tendon Organs (GTOs)

• Function: Detects muscle tension/force.

• Location: Between muscle fibers and tendons.

• Modality: Proprioception.

• Mechanism:

• Muscle force increases → GTOs increase neural discharge.

• Provides feedback to regulate muscle force and prevent excessive tension.

• Protective Role: Prevents muscle/tendon overstrain by triggering inhibitory reflex.

Slide 11-12: GTO Reflex

• Function: Signals CNS about muscle contraction/stretching.

• Prevents Injury: Stops excessive muscle tension from damaging muscles, tendons, and joints.

• Video Links: Demonstrations of GTO reflex action.

Slide 13-14: Joint Receptors

• Location: Synovial joints.

• Function: Detects mechanical deformation within capsules and ligaments.

• Firing Mechanism: Previously thought to fire only at extreme movement; now shown to fire throughout motion range.

• Primary Roles:

1. Awareness of joint position.

2. Protection from excessive flexion/extension.

Slide 15-16: Types of Joint Receptors

1. Golgi-Mazzoni Corpuscles: Detects velocity/acceleration. (fast adapting)

2. Pacinian Corpuscles: Signals movement onset/termination. (fast adapting)

3. Ruffini Endings: Active in both motion and rest; detects speed. (slow adapting)

4. Golgi-type Endings: Respond to ligament stretch; active in extreme positions. (slow adapting)

Free nerve endings: located in joint capsule and connective tissue. Activated by mechanical or chemical irritation. (slow adapting)

Slide 17-18: Joint Receptor Activation

• Joint receptors signal continuously but are more active at extreme positions.

• Swelling increases receptor sensitivity, influencing movement coordination.

• No position exists where all joint receptors are silent.

Slide 19-20: Efference Copy

• Definition: Internal copy of a motor command, used for movement prediction and adaptation.

• Function:

• Prepares sensory systems for upcoming movements.

• Compares expected vs. actual movement outcomes.

• Helps modify motor actions based on feedback.

• Proprioception Contribution: Provides feedforward sensory input to refine movement.

Slide 21-22: Feedforward & Feedback Control

• Efference Copy Mechanism:

1. Motor cortex sends movement command.

2. Efference copy informs the cerebellum of expected movement.

3. CNS compares expected vs. actual sensory feedback.

• Learning Aspect: Internal models improve with practice.

Slide 23-24: Evidence of Efference Copy

• Self-initiated vs. External Stimuli:

• Example: Tickle sensation reduced when self-initiated due to prediction.

• Perception Adjustments:

• Phantom Limb Phenomenon: Brain maintains efference copy for missing limbs.

• Sense of Effort: Perceived weight increases over time due to muscle fatigue.

Slide 25: Efference Copy & Motor Control

• Key Function: Compares predicted vs. actual sensory outcomes.

• Results: Adjustments in movement execution based on mismatches.

Slide 26: Lecture Summary

• Sensory Neural Activity: Essential for motor control.

• GTOs: Monitor muscle force and prevent overstrain.

• Joint Receptors: Provide position sense and protect joints.

• Efference Copy: Enables predictive control and movement adaptation.

Slide 27: Sensory Receptor Overview table