Comprehensive Study Guide: Key Topics in Anatomy & Physiology (BIO 2111)

Homeostatic Regulation of Bone Remodeling

Overview of Bone Remodeling

Bone remodeling is a continuous process where mature bone tissue is removed (resorption) and new bone tissue is formed (ossification). This process is essential for maintaining bone strength and mineral homeostasis.

• Osteoclasts: Cells that break down bone matrix, releasing minerals into the blood.

• Osteoblasts: Cells that build new bone matrix.

• Hormonal Regulation: Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts; calcitonin lowers blood calcium by inhibiting osteoclasts.

• Mechanical Stress: Weight-bearing exercise stimulates bone formation.

Example: In response to low blood calcium, PTH is released, increasing osteoclast activity and calcium release from bone.

Spinal Cord Organization and Reflex Arc

Structure and Function of the Spinal Cord

The spinal cord is organized into gray and white matter and is responsible for transmitting neural signals and mediating reflexes.

• Gray Matter: Contains neuron cell bodies; organized into dorsal (sensory) and ventral (motor) horns.

• White Matter: Contains myelinated axons; organized into ascending (sensory) and descending (motor) tracts.

Reflex Arc

• Components: Receptor, sensory neuron, integration center, motor neuron, effector.

• Function: Provides rapid, involuntary responses to stimuli (e.g., knee-jerk reflex).

Protein and Muscle Filaments

Muscle Fiber Structure

Muscle contraction depends on the interaction of protein filaments within muscle fibers.

• Thick Filaments: Composed of myosin.

• Thin Filaments: Composed of actin, troponin, and tropomyosin.

• Sliding Filament Theory: Muscle contraction occurs when myosin heads bind to actin and pull the thin filaments toward the center of the sarcomere.

Equation:

$\text{Force} = \text{Cross-bridges formed} \times \text{Force per cross-bridge}$

Appendicular Skeleton and Locomotion (Joints)

Structure and Function

The appendicular skeleton includes the limbs and girdles, enabling movement through joints.

• Major Bones: Humerus, radius, ulna, femur, tibia, fibula, pelvic and pectoral girdles.

• Joints: Synovial joints (e.g., knee, shoulder) allow for a wide range of motion.

• Locomotion: Coordinated muscle and joint action produces movement.

Membrane Transport in Muscle and Neurons

Mechanisms of Membrane Transport

Muscle and neuron function depends on the movement of ions across cell membranes.

• Passive Transport: Diffusion and facilitated diffusion (e.g., sodium and potassium ions).

• Active Transport: Sodium-potassium pump maintains resting membrane potential.

Equation:

$3 \text{Na}^+ \text{ out} / 2 \text{K}^+ \text{ in}$ per ATP hydrolyzed

Connective Tissue in the Integumentary System

Types and Functions

The integumentary system contains various connective tissues that provide support and protection.

• Dermis: Dense irregular connective tissue with collagen and elastic fibers.

• Hypodermis: Adipose tissue for insulation and energy storage.

Bone and Nervous System Protection

Protective Structures

Bones and connective tissues protect vital nervous system structures.

• Skull: Protects the brain.

• Vertebral Column: Protects the spinal cord.

• Meninges: Connective tissue membranes surrounding the brain and spinal cord.

Myelin Formation and Neural Conduction in CNS vs PNS

Myelination and Signal Transmission

• CNS: Oligodendrocytes form myelin sheaths.

• PNS: Schwann cells form myelin sheaths.

• Saltatory Conduction: Action potentials jump between nodes of Ranvier, increasing conduction speed.

Thermoregulation by Body Systems

Maintaining Body Temperature

Multiple body systems work together to regulate internal temperature.

• Integumentary System: Sweat glands and blood vessels in the skin dissipate heat.

• Muscular System: Shivering generates heat.

• Nervous System: Hypothalamus acts as the body’s thermostat.

Epithelial Tissue in Cutaneous and Mucous Membranes

Types and Functions

• Cutaneous Membrane: Skin; composed of stratified squamous epithelium.

• Mucous Membranes: Line body cavities open to the exterior; contain various epithelial types (e.g., simple columnar in the gut).

Membrane Potentials in Muscular and Nervous Tissue

Resting and Action Potentials

• Resting Membrane Potential: Difference in charge across the membrane, typically -70 mV in neurons.

• Action Potential: Rapid depolarization and repolarization of the membrane, enabling signal transmission.

Equation:

$V_m = V_{in} - V_{out}$

Somatic Motor Control of Skeletal Muscle

Voluntary Muscle Control

• Somatic Nervous System: Controls voluntary movements via motor neurons.

• Neuromuscular Junction: Site where motor neuron communicates with muscle fiber using acetylcholine.

Autonomic Control of Smooth and Cardiac Muscle

Involuntary Muscle Regulation

• Autonomic Nervous System (ANS): Regulates involuntary activity in smooth and cardiac muscle.

• Sympathetic Division: Increases heart rate, dilates bronchioles, etc.

• Parasympathetic Division: Decreases heart rate, promotes digestion, etc.

Integumentary Receptors and Sensory Pathways

Sensory Reception in the Skin

• Mechanoreceptors: Detect touch, pressure, vibration (e.g., Meissner’s corpuscles, Pacinian corpuscles).

• Nociceptors: Detect pain.

• Thermoreceptors: Detect temperature changes.

Muscle and Bone Response to Exercise

Adaptations to Physical Activity

• Muscle: Hypertrophy (increase in fiber size), increased mitochondrial density, improved endurance.

• Bone: Increased bone density and strength due to mechanical loading.

Example: Weight-bearing exercise stimulates osteoblast activity, increasing bone mass.

System	Response to Exercise
Muscular	Hypertrophy, increased endurance
Skeletal	Increased bone density

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard Anatomy & Physiology curricula.