kinesiology 4460

Skeletal Muscles

• Functions: Movement, protection, stability, posture, support, and heat production
• Aggregate muscle action: Muscles often work in groups to perform joint actions

Muscle Nomenclature

• Naming criteria: Visual appearance, anatomical position, and function
• Visual appearance: Shape (e.g., deltoid, rhomboid), size (e.g., gluteus maximus, teres minor)
• Anatomical position: Location (e.g., rectus femoris, palmaris longus), point of attachment (e.g., coracobrachialis, extensor hallucis longus)
• Function: Action (e.g., erector spinae, supinator), combinations (e.g., pronator quadratus, adductor magnus)

Shapes of Muscles and Fiber Arrangement

• Impact on force and range: Cross-sectional diameter and muscle length affect force production and range of motion
• Fiber arrangement types: Parallel (greater range of motion), pennate (higher force production)
• Examples: Brachialis (parallel), sartorius (parallel), orbicularis oris (parallel), biceps femoris (unipennate), rectus femoris (bipennate), deltoid (multipennate)

Muscle Properties

• Tissue properties: Irritability, contractility, extensibility, and elasticity
• Irritability: Responds to stimuli
• Contractility: Produces tension
• Extensibility: Stretches beyond resting length
• Elasticity: Returns to original length after stretching

Muscle Terminology

• Intrinsic vs. extrinsic muscles: Intrinsic muscles are located within a body region, while extrinsic muscles span across different body regions
• Muscle actions: Action, joint actions, and aggregate muscle action
• Action: Result of muscle contraction
• Joint actions: Movements such as flexion, extension, etc.
• Aggregate muscle action: Multiple muscles working together

Muscle Innervation and Amplitude

• Innervation: Nerve supply to muscles
• Amplitude: Range of muscle length from fully stretched to contracted

Muscle Structure and Tendons

• Gaster: Muscle belly containing contractile fibers
• Tendons: Connect muscles to bones
• Aponeurosis: Flattened tendon, binds and connects muscles
• Fascia: Connective tissue organizing muscles
• Retinaculum: Holds tendons in place

Origin and Insertion

• Origin: Proximal attachment, less moveable
• Insertion: Distal attachment, more moveable

Contraction Mechanics

• Muscles contract towards the center
• Stabilization affects which bone moves during contraction

Muscle Contraction Types

• Isometric: Muscle length doesn't change
• Isotonic: Muscle changes length
• Concentric: Muscle shortens
• Eccentric: Muscle lengthens

Roles in Movement

• Agonist: Primary mover
• Antagonist: Opposes agonist
• Synergists: Assist agonist
• Helping synergists: Assist and control movement
• True synergists: Prevent unwanted actions
• Stabilizers: Maintain stability
• Neutralizers: Counteract unwanted movements
• Force couples: Create rotational movements

Neural Control of Movement

• Levels: Cerebral cortex, basal ganglia, cerebellum, brainstem, and spinal cord
• Cerebral cortex: Decision-making
• Basal ganglia: Movement sequencing
• Cerebellum: Timing and refinement
• Brainstem: Balance and wakefulness
• Spinal cord: Reflexes and pathways

Proprioception and Kinesthesis

• Proprioceptors: Provide body position information
• Kinesthesis: Awareness of body movements
• Proprioceptors types: Muscle spindles, Golgi tendon organs, and cutaneous proprioceptors

Principles Affecting Force Production

• Neural control and motor units: Motor unit, all-or-none principle, and force production
• Motor unit: Single neuron and its fibers
• All-or-none principle: Full contraction or none
• Force production: Recruitment and frequency, length-tension relationship, and velocity-force relationship
• Elastic energy and stretch-shorten cycle: Elastic energy, reciprocal inhibition, and active and passive insufficiency