Review Objectives 5-2 (Part 1)

Homeostasis

The process by which the body maintains a stable internal environment despite changes in external conditions.

Necessity of Homeostasis

Ensures internal conditions remain conducive to cellular processes, preventing impaired function or cell death.

Physiological Variables

Homeostasis is relevant to many variables, including body temperature, blood glucose levels, and pH levels.

Nervous System

One of the two control systems that maintain homeostasis, using rapid electrical signals to communicate with target organs.

Endocrine System

The second control system that maintains homeostasis, releasing hormones into the bloodstream for slower, longer-lasting responses.

Walter Bradford Cannon

The scientist who coined the term "homeostasis" in the 1920s.

Major Homeostatically Regulated Variables

Include body temperature, blood glucose levels, blood pressure, and various electrolytes.

Electrolytes

Substances that dissociate into ions in water, essential for physiological functions like nerve impulse transmission.

Sodium (Na⁺)

A positively charged electrolyte important for fluid balance and nerve function.

Potassium (K⁺)

A positively charged electrolyte crucial for cell membrane potential and muscle contractions.

Calcium (Ca²⁺)

A positively charged electrolyte important for muscle contraction and neurotransmitter release.

Chloride (Cl⁻)

A negatively charged electrolyte that helps maintain osmotic pressure and acid-base balance.

Negative Feedback

A regulatory mechanism where a change in a variable triggers a response that counteracts the initial fluctuation.

Set Point

The desired value of a physiological variable that the body aims to maintain.

Effector(s)

Organs or cells that execute the response to correct deviations from the set point.

Thermoreceptors

Sensors that detect changes in body temperature and communicate with the hypothalamus.

Hypothalamus

The controller that acts as the body's thermostat, regulating body temperature.

Positive Feedback

A mechanism that amplifies a change in a variable, driving processes to completion, such as labor contractions.

Oxytocin

A peptide hormone released during labor that enhances uterine contractions.

Osteoblasts

Bone-forming cells that synthesize and secrete the organic components of the bone matrix.

Osteoclasts

Bone-resorbing cells that break down bone matrix, releasing calcium into the bloodstream.

Osteocytes

Mature bone cells that maintain the bone matrix and communicate with other bone cells.

Trabeculae

The structural units of spongy bone, providing lightweight support and shock absorption.

Endosteum

A thin membrane lining the inner surfaces of bones, involved in bone growth and remodeling.

Bone Remodeling

The ongoing replacement of old bone tissue by new bone tissue, involving osteoclasts and osteoblasts.

Medullary Cavity

The central cavity within long bones that contains bone marrow.

Epiphyseal Growth Plate

A hyaline cartilage structure that allows for longitudinal bone growth in juveniles.

Hydroxyapatite

A crystalline mineral salt that provides compressive strength and hardness to bone.

Collagen Fibers

Provide tensile strength to bone, allowing it to resist stretching and twisting forces.

Emergent Property

The combination of compressive and tensile strength in bone creates a strong and resilient material.

Steel-Reinforced Concrete Analogy

Bone's structure, with collagen fibers and hydroxyapatite, is similar to concrete reinforced with steel for strength.

Bone Composition Comparison

An authentic human femur may show differences in mineral density and collagen content compared to a modern femur.