Bones, Nerves, and Skeletal Muscle

Bones, Nerves, and Skeletal Muscle

Basic Anatomical Parts

• Anatomy of the Bone

• Anatomy of the Nerve

• Anatomy of the Skeletal Muscle

Integrated, Physiological Roles

• Joints: The interaction between bones and muscles

• Neuromuscular Control: Interaction between nerve and muscle

Musculoskeletal Health and Disease

• Overview of health professionals' roles concerning bones, nerves, and skeletal muscle

Outline of Learning Objectives

• LO1: Explain the basic anatomy of bones, nerves, and skeletal muscle.

• LO2: Describe the functions of bones, nerves, and skeletal muscle.

• LO3: Identify common diseases related to these systems.

• LO4: Recognize kinesiology professionals focused on these anatomical structures.

Development and Functionality

• The development of bones, nerves, and muscles occurs against the resistance of amniotic fluid before birth.

• These anatomical structures operate in synchrony:

  • Bone: Serves as anchor points for muscles.

  • Muscles: Depend on nerves for movement control.

• Maturation and exercise contribute to the development of these systems.

Measuring Skeletomuscular Function

• Muscular Strength: The maximum force a muscle can exert in a single effort.

• Muscular Endurance: The ability to perform submaximal efforts repeatedly without excessive fatigue.

• Both are crucial health-related components of fitness essential for daily function.

Resistance Training

• Resistance training is essential beyond aesthetics; it promotes skeletal, muscular, and neuromuscular health.

• Maintaining a healthy muscular system requires intentional lifestyle choices.

Basic Anatomical Parts of Each System

• Understanding the anatomical parts enhances comprehension of their significance for overall health and human movement.

Functions of Bone

• The human skeleton consists of 206 bones that serve several functions:

  • Support and Protection: Provides structural integrity to body and organs.

  • Framework: Maintains body shape.

  • Stability: Works in conjunction with joints, tendons, ligaments, cartilage, and connective tissue.

  • Bone Marrow Encapsulation: Protects the site of red blood cell production.

  • Mineral Reservoir: Stores calcium and phosphorus.

Bone Cells

• Osteocytes: Bone cells defined by:

  • “osteo” = bone

  • “cyte” = cell

• Types of bone cells through roles:

  • Osteoblasts: Cells responsible for bone formation.

  • Osteoclasts: Cells that resorb or break down bone.

• Bone undergoes continuous remodeling; adult skeleton completely replaced approximately every decade.

Bone Growth and Strength

• The recycling of bone (building new, removing old/damaged) is critical for growth and strength.

• Bone Density: Influenced by weight-bearing exercise which correlates with bone strength.

• Muscle health is interlinked with bone health due to the muscle pull on bones.

Trabecular and Cortical Bone

• Trabecular Bone (also known as spongy or cancellous bone):

  • Located at the ends of long bones.

  • Contains bone marrow and is vital for blood cell production.

• Cortical Bone (compact bone):

  • Found in the pelvis, ribs, skull, and vertebrae.

  • Generally stronger and denser than trabecular bone.

Bone Lining and Attachments

• Periosteum: A fibrous membrane covering bones, containing blood vessels, nerves, and lymphatics; attachment site for tendons and ligaments.

  • Tendons: Connect muscles to bones.

  • Ligaments: Connect bones to other bones.

• Articular Cartilage: Smooth surfaces on bones to reduce friction during movement.

Motor Control and the Nervous System

• Motor Control: Ability of muscles to:

  • Perform complex movements.

  • Adjust force for various activities.

• Role of the Nervous System: Essential for movement, with nerves initiating and relaying muscle movement via electrical signals from the brain or spinal cord.

Central and Peripheral Nervous System

• Central Nervous System (CNS): Comprises the brain and spinal cord.

• Peripheral Nervous System (PNS): Involves all nerves outside the CNS, with divisions:

  • Efferent Signals: Signals from CNS to tissues (motor functions).

  • Afferent Signals: Sensory information sent to CNS.

Efferent (Motor) Division

• Somatic Nervous System: Responsible for voluntary movements.

• Autonomic Nervous System: Controls involuntary functions; can either:

  • Slow down (Parasympathetic: “brake” for relaxation and restoration).

  • Speed up (Sympathetic: “gas pedal” for fight or flight response).

Afferent Nerves

• The Afferent Nervous System relays sensory information back to the CNS:

  • Includes senses like touch, smell, sight, and sound which are crucial for survival and proprioception.

The Neuron: Foundational Nerve Cell

• Neuron: Basic nerve unit primarily responsible for skeletal muscle control.

Anatomy of a Neuron

• Somatic Neuron: Characterized by:

  • Dendrites: Receive input from surroundings.

  • Axon: Transmits impulses to muscle fibers as electrical signals.

Anatomy of the Skeletal Muscle

• Each of the body's over 600 muscles:

  • Has a name based on origin, insertion, action, or shape.

  • Origin: Starting point of the muscle.

  • Insertion: Endpoint of the muscle.

Whole Muscle Structure

• Describes the entirety of a muscle:

  • Composed of muscle fibers, connective tissue, nerve supply, and blood vessels.

Parts of Whole Muscle

• Muscle Fiber: Individual muscle cell made from smaller contractile proteins.

• Muscle fibers grouped into fascicles; fascicles collectively form the whole muscle.

  • Connective Tissues:

  • Endomysium: Covers muscle fibers.

  • Perimysium: Encases fascicles.

  • Epimysium: Surrounds the entire muscle.

Inside the Muscle Fiber

• Sarcoplasm: The fluid within the muscle fiber containing:

  • Glycogen

  • Enzymes

  • Mitochondria

  • Sarcoplasmic reticulum (stores Ca^{2+})

  • Myofibrils

Myofibrils

• Myofibrils: Composed of contractile fibers (myo = muscle, fibrils = fibers). Focus on:

  • Contractile Proteins:

  • Actin

  • Myosin

  • Regulatory Proteins:

  • Troponin

  • Tropomyosin

Contractile Mechanism

• Whole muscle contraction results from synchronized action of small protein molecules in sarcomeres.

The Sarcomere: Functional Unit of Skeletal Muscle

• Made of numerous sarcomeres running end-to-end.

  • Sarcomeres in series for length.

  • Sarcomeres in parallel for thickness.

Integrated, Physiological Roles of Bone, Nerve, and Muscle

• Joints function as a confluence of muscles pulling bones for movement, supported by additional structures:

  • Tendons: Connect muscle to bone.

  • Ligaments: Connect bone to bone.

  • Articular Cartilage: Facilitates smooth movement.

Neuromuscular Control

• Action Potential: Electrical signal transmitted down a neuron's axon causing muscle fiber activation originating from the CNS.

• Signals propagate rapidly between efferent nervous system and somatic neurons to stimulate muscle fibers.

Neuromuscular Junction

• Neuronal axons connect with multiple muscle fibers facilitating synchronized responses through a connection point called the neuromuscular junction.

Motor Unit

• Defined as the motor neuron and the group of muscle fibers it connects.

• Each motor unit controls a specific muscle fiber type; force varies based on motor unit recruitment.

Neurotransmitter Mechanism

• The electrical action potential at the neuron's terminal converts to a chemical signal (neurotransmitter).

  • Acetylcholine is released for skeletal muscle communication, initiating depolarization leading to muscle contraction.

Excitation-Contraction Coupling

• Involves transfer of electrical signaling from neuron to muscle, termed excitation, resulting in muscular contraction through myofibril action.

  • Myosin acts on actin filaments through crossbridges creating powerstrokes.

Sliding Filament Theory

• Muscle contraction involves the sliding of interactively positioned actin and myosin across each other within sarcomeres:

  • Concentric Action: Sarcomeres shorten under tension.

  • Eccentric Action: Sarcomeres lengthen under tension.

Muscle Fiber Differentiation

• Distinct qualities among muscle fibers include:

  • Speed of Contraction:

  • Slow (Type I)

  • Fast (Type IIa)

  • Very Fast (Type IIx)

  • Oxidative Capacity: Measure of ability for fibers to produce ATP with oxygen for sustained performance.

Endurance vs. Power in Muscle Fibers

• Different motor units engage based on performance task demands:

  • Type I: High resistance to fatigue, suitable for endurance tasks.

  • Type IIa: Intermediate qualities; adaptive based on usage.

  • Type IIx: Quick, high force production suitable for power tasks.

Musculoskeletal Health and Disease

• Importance of muscle health linked to several chronic conditions:

  • Osteoporosis: Condition marked by low bone mineral density, increased fracture risk.

  • Osteoarthritis: Degenerative joint disease resulting in pain and mobility restrictions; preventive through muscle strengthening.

  • Type II Diabetes: Metabolic disease affecting glucose regulation; physical activity facilitates glucose uptake by muscle.

Role of Kinesiology Professionals

• Professionals in kinesiology are deeply involved in understanding the anatomy and functionality of bones, nerves, and muscles for rehabilitation and training:

  • Therapists: Assist recovery and retain muscle health in movements affecting daily life (e.g., after strokes, aging, surgeries).

  • Athletic Trainers: Knowledge necessary for managing sports injuries, enhancing recovery through evidence-based practice.

  • Physical Educators: Develop plans suited to various age groups and skill levels to promote health.

  • Personal Trainers: Focus on optimizing musculoskeletal health through tailored fitness programs addressing imbalances and pain.

Conclusion

• Overall, comprehension of anatomy is crucial for understanding bodily function; all systems are interconnected and collectively studied in kinesiology for both health and performance purposes.