Skilled Performance and Motor Learning

Introduction to Motor Control

This section introduces the fundamental concepts of motor control, focusing on how the nervous system enables skilled movement. Understanding motor control is essential for comprehending how humans learn and perform complex motor tasks.

• Motor Control: The process by which complex neural networks produce movement through the activation and coordination of muscles and limbs.

• Mechanisms: Includes both reflexive/reactive and voluntary actions.

• Key Components:

  • Sensory (Afference): Input from sensory organs to the central nervous system (CNS).

  • Cortical Processing: Integration and interpretation of sensory information in the brain.

  • Motor/Action (Efference): Output from the CNS to muscles to produce movement.

  • Coordination: Harmonization of sensory input and motor output for smooth movement.

• Example: Returning a tennis ball involves visual processing (seeing the ball), planning (premotor cortex), motivation (amygdala, hypothalamus), and execution (motor cortex, cerebellum).

Course Overview

Perspectives in Human Motor Control

The study of motor control is multidisciplinary, integrating biological and behavioral perspectives. The information processing approach is central to understanding how the nervous system manages movement.

• Biological Perspective: Examines the physiological and anatomical basis of movement.

• Behavioral Perspective: Focuses on observable actions and learning processes.

• Multidisciplinary Interest: Fields such as engineering, psychology, neuroscience, and physical education contribute to motor control research.

Organization of the Nervous System

Central and Peripheral Components

The nervous system is divided into central and peripheral components, each with distinct structures and functions but closely interconnected.

• Central Nervous System (CNS): Consists of the brain and spinal cord. Responsible for processing information and issuing commands.

• Peripheral Nervous System (PNS): Composed of peripheral nerves and ganglia. Transmits information between the CNS and the rest of the body.

• Relationship: The CNS and PNS are separated anatomically but functionally interconnected.

Cellular Components of the Nervous System

Major Cell Types

The nervous system is primarily composed of two major cell types: neurons and glia.

• Neurons: Specialized cells responsible for transmitting electrical and chemical signals. The human brain contains approximately 100 billion neurons, forming about 100 trillion connections (synapses).

• Glia: Supportive cells that provide structural and metabolic support to neurons, maintain homeostasis, and form myelin.

Structure of a Neuron

Neurons have a characteristic structure that enables them to transmit signals efficiently.

• Dendrites: Branch-like extensions that receive signals from other neurons.

• Cell Body (Soma): Contains the nucleus and metabolic machinery.

• Axon: Long projection that transmits electrical impulses away from the cell body.

• Presynaptic Boutons: Terminal ends of the axon where neurotransmitters are released to communicate with other cells.

Functional Classification of Neurons

Neurons are classified based on their function within the nervous system.

• Sensory Neurons (Afferent): Transmit information from sensory receptors to the CNS. Cell bodies are located in the dorsal root ganglia, just outside the spinal column. Approximately 5 million in the human body.

• Motor Neurons (Efferent): Control muscle contraction by transmitting signals from the CNS to muscles. Cell bodies are located in the ventral horn of the spinal cord. There are several hundred thousand motor neurons in the CNS.

• Interneurons: Integrate information by receiving inputs from multiple sources and passing processed signals to various locations. They vastly outnumber sensory and motor neurons.

Central Nervous System (CNS) Organization

Main Regions of the CNS

The CNS is organized into several key regions, each with specialized functions.

• Spinal Cord: Transmits signals between the brain and the rest of the body; involved in reflexes.

• Brainstem: Includes the medulla (controls vital functions), pons (relay between regions), and midbrain (controls reflexive eye movements and sensory reflexes).

• Cerebellum: Coordinates movement and balance.

• Thalamus: Relay station for sensory and motor signals.

• Cerebral Hemispheres (Forebrain): Responsible for higher cognitive functions.

Structure of the Spinal Cord

The spinal cord is organized into gray and white matter, each with distinct roles.

• Gray Matter: Contains cell bodies. The dorsal horn processes sensory information, while the ventral horn contains motor neurons.

• White Matter: Composed of myelinated axons forming ascending and descending tracts. Organized into dorsal, lateral, and anterior columns.

Somatotopic Organization

The ventral horn of the spinal cord is organized so that different regions correspond to different muscle groups, reflecting the body's layout.

Brainstem

The brainstem is made up of the medulla, pons, and midbrain, each with specific functions:

• Medulla: Extension of the spinal cord; regulates life support systems.

• Pons: Connects higher brain regions, cerebellum, and spinal cord.

• Midbrain: Controls reflexive eye movements and processes auditory/visual reflexes.

Cerebral Cortex

The cerebral cortex is the outer layer of the brain, highly folded to maximize surface area and neuron density.

• Gyri: Raised folds or bumps.

• Sulci: Valleys between gyri.

• Fissures: Deep sulci.

Lobes of the Cerebral Cortex

The cortex is divided into four main lobes, each with specialized functions:

• Frontal Lobe: Movement, planning, reasoning.

• Parietal Lobe: Bodily sensation, spatial processing.

• Occipital Lobe: Visual processing.

• Temporal Lobe: Hearing, smell, taste, visual perception, speech (left hemisphere).

Functional Areas of the Cortex

• Primary Sensory Areas: Localize and identify sensory stimuli (e.g., primary somatosensory cortex).

• Primary Motor Areas: Trigger and execute movement commands (e.g., primary motor cortex).

• Association Areas: Integrate diverse information for perception, movement, and motivation.

Peripheral Nervous System (PNS)

Subdivisions of the PNS

The PNS is divided into somatic and autonomic systems, each serving different functions.

• Somatic Nervous System: Transmits information to and from the CNS about muscle and limb position and the external environment.

• Autonomic Nervous System: Regulates viscera, smooth muscle, and exocrine glands. Includes sympathetic and parasympathetic divisions.

Navigating the Nervous System

Directional Terms and Planes

Understanding anatomical terminology is essential for describing locations and directions in the nervous system.

• Dorsal vs. Ventral: Back vs. front.

• Superior vs. Inferior: Above vs. below.

• Anterior vs. Posterior: Front vs. back.

• Rostral vs. Caudal: Toward the nose vs. toward the tail.

• Medial vs. Lateral: Toward the midline vs. away from the midline.

• Distal vs. Proximal: Farther from vs. closer to the point of attachment.

• Ipsilateral vs. Contralateral: Same side vs. opposite side.

• Planes: Horizontal, coronal, and sagittal planes are used to describe sections of the brain and body.

Summary Table: Major Components of the Nervous System

Key Takeaways

• Most motor behaviors involve sensory, motor, and motivational systems.

• Neurons are the primary signaling cells; glia provide support.

• The CNS and PNS are anatomically distinct but functionally integrated.

• Understanding the structure and function of the nervous system is foundational for studying motor control and learning.

Additional info: Some explanations and definitions have been expanded for academic clarity and completeness.