Chapter 6: Skeletal System

Types and Functions of Cartilage

Cartilage is a specialized connective tissue that provides support, flexibility, and strength to various structures in the body. There are three main types: hyaline cartilage, elastic cartilage, and fibrocartilage.

• Hyaline cartilage: Maintains the shape of a structure while allowing great flexibility.

• Fibrocartilage: Resists compression and provides great tensile strength.

• Elastic cartilage: Provides support with flexibility and resilience.

Locations of Cartilage Types in the Body

Functions of Skeleton and Bone Tissue

The skeleton and bone tissue perform several vital functions:

• Support: Provides a framework for the body.

• Protection: Shields vital organs (e.g., brain, heart).

• Movement: Acts as levers for muscles.

• Mineral storage: Stores calcium and phosphorus.

• Blood cell formation: Occurs in bone marrow (hematopoiesis).

• Triglyceride storage: Fat storage in yellow marrow.

• Hormone production: Osteocalcin regulates bone formation and influences metabolism.

Bone Structure and Cells

Bones are composed of compact and spongy bone, each with distinct structures and cell types.

• Osteons: Structural units of compact bone.

• Trabeculae: Lattice-like structures in spongy bone.

• Osteocytes: Mature bone cells that monitor and maintain bone matrix.

• Canaliculi: Tiny canals connecting osteocytes for nutrient exchange.

• Central canals: Channels in osteons containing blood vessels and nerves.

• Lacunae: Chambers containing osteocytes.

• Osteoblasts: Bone-forming cells that secrete bone matrix.

• Osteoclasts: Cells that resorb (break down) bone.

Bone Remodeling and Ossification

• Endochondral ossification: Bone develops by replacing hyaline cartilage.

• Intramembranous ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of the skull).

• Bone remodeling: Occurs primarily in the periosteum and endosteum.

Calcium Homeostasis and Hormones

Calcium levels in the blood are tightly regulated by hormones:

• Calcitonin: Lowers blood calcium levels.

• Parathyroid hormone (PTH): Raises blood calcium levels.

• Calcitriol: Active form of vitamin D, increases calcium absorption.

• Osteoprotegerin: Inhibits bone resorption.

Types of Bone Fractures

Bone Disorders

Chapter 7: Muscular System

Functions of Skeletal Muscle Tissue

Skeletal muscle tissue is essential for movement and other physiological functions.

• Movement: Enables locomotion and manipulation of the environment.

• Posture: Maintains body position.

• Joint stabilization: Stabilizes joints during movement.

• Heat generation: Produces heat as a byproduct of muscle activity.

Muscle Proteins and Their Functions

• Myosin: Makes up most of the thick filament; binds calcium ions.

• Actin: Makes up most of the thin filament.

• Troponin: Binds calcium ions; regulates muscle contraction.

• Tropomyosin: Blocks binding sites on the thin filament.

Muscle Contraction Mechanism

Muscle contraction is initiated by the release of calcium ions from the sarcoplasmic reticulum, which allows actin and myosin to interact.

• Steps of the cross bridge cycle:

  1. Cross bridge formation

  2. Power stroke

  3. Cross bridge detachment

  4. Cocking of the myosin head

• ATP generation: Occurs via aerobic (oxygen-dependent) and anaerobic (without oxygen) pathways.

Isometric vs. Isotonic Contractions

• Isometric contraction: Muscle does not change length; load is not moved.

• Isotonic contraction: Muscle changes length; load is moved.

Effects of Aerobic vs. Resistance Exercise

Types of Muscle Tissue

• Skeletal muscle: Voluntary, striated, attached to bones.

• Cardiac muscle: Involuntary, striated, found in the heart.

• Smooth muscle: Involuntary, non-striated, found in walls of hollow organs.

Chapter 8: Nervous System

Functions of the Nervous System

The nervous system is responsible for communication, integration, and control throughout the body.

• Sensory input: Detects changes inside and outside the body.

• Integration: Processes and interprets sensory input.

• Motor output: Responds by activating effector organs (muscles and glands).

Central and Peripheral Nervous Systems

• CNS (Central Nervous System): Brain and spinal cord; processes information and initiates responses.

• PNS (Peripheral Nervous System): Nerves outside the CNS; transmits signals to and from the CNS.

Neuroglia (Glial Cells)

• Ependymal cells: Line cerebrospinal fluid-filled CNS cavities.

• Schwann cells: Form myelin sheaths around PNS nerve fibers.

• Microglia: Defensive cells in the CNS; engulf microorganisms and debris.

• Satellite cells: Surround and support neuron cell bodies in the PNS.

Neuron Structure and Function

• Cell body (soma): Contains nucleus and major biosynthetic center.

• Dendrites: Receive information from other neurons.

• Axon: Generates and transmits nerve impulses.

Functional Classification of Neurons

• Motor neurons: Transmit impulses from CNS to muscles/glands.

• Sensory neurons: Transmit impulses from receptors to CNS.

• Interneurons: Association neurons; connect sensory and motor pathways.

Membrane Channels and Action Potentials

• Chemically gated channels: Open when neurotransmitter binds.

• Voltage-gated channels: Open/close in response to changes in membrane potential.

• Mechanically gated channels: Open in response to physical deformation.

• Leakage channels: Always open; allow ions to move down their gradient.

Action Potential Generation

• Transition from local graded potential to long-distance action potential occurs at the axon hillock.

• Nodes of Ranvier facilitate rapid conduction of action potentials via saltatory conduction.

Equations

• Nernst Equation:

• Ohm's Law (for membrane potential):

Summary Table: Neuron Types and Functions

Additional info: Some content and examples have been inferred and expanded for completeness and clarity.