Notes on Introduction to the Human Body and Homeostasis

Anatomy vs Physiology

  • Anatomy and physiology are often grouped together but are very different fields of study.
    • Anatomy: the structure and organization of body parts.
    • Physiology: the function and processes of those parts.
    • They are related but distinct disciplines that complement each other in understanding the human body.

Medical Terminology

  • Medical terminology uses word roots, prefixes, and suffixes to construct terms related to the body.
  • Knowing the meanings of roots, prefixes, and suffixes helps you understand new terms more quickly.
  • Examples of common components (not exhaustively listed):
    • Roots: cardio- (heart), neuro- (nerve), derm- (skin), gastr- (stomach)
    • Prefixes: hypo- (below/ deficient), hyper- (above/ excess)
    • Suffixes: -itis (inflammation), -ology (study of), -logy (the study of)

Homeostasis Overview

  • Homeostasis is the interaction of all body regulatory processes to maintain stability in the internal environment.
  • It is vital for organism survival.
  • It is a dynamic equilibrium: the system maintains stability through continual adjustments.
  • A set point is the reference value around which a regulated variable fluctuates.

What needs to be kept at equilibrium?

  • Temperature
  • Blood pressure
  • Blood pH
  • Blood glucose
  • Body fluid volume & composition

How is Homeostasis Regulated?

  • Autoregulation (Intrinsic Regulation): A tissue, organ, or system automatically adjusts its activities to maintain function without external input.
  • Extrinsic Regulation: Nervous & endocrine systems regulate or adjust other body systems to maintain homeostasis.

Stressors

  • A STRESSOR is a stimulus that disrupts homeostasis.

  • External Stresses:

    • Extremes of temperature
    • Hypoxia (low oxygen availability)
    • Loud noise
    • Smells
    • Skin contact

  • Internal Stresses:

    • Low blood glucose
    • Low blood pH
    • Pain
    • Psychological stress
    • Poisoning
    • Infection

Nervous vs Endocrine Regulation of Homeostasis

  • The nervous system and endocrine system regulate homeostasis differently. There are 4 major differences:

  • Type of signal used

    • Nervous system: uses electrical impulses along neurons and synaptic neurotransmitters for signaling.
    • Endocrine system: uses chemical hormones released into the bloodstream.

  • Specificity of response

    • Nervous system: highly specific, targeting particular organs or tissues.
    • Endocrine system: often widespread, affecting multiple tissues and organs.

  • Time needed to see effect

    • Nervous system: rapid responses, typically milliseconds to seconds.
    • Endocrine system: slower responses, ranging from seconds to minutes, hours, or longer.

  • Length of effect

    • Nervous system: effects are usually brief and cease when the stimulus ends.
    • Endocrine system: effects tend to be longer-lasting due to hormone circulation and metabolism.

Connections and Practical Relevance (Contextual Notes)

  • Homeostasis relies on the integration of both local (autoregulation) and body-wide (extrinsic) regulatory mechanisms.
  • Stressors can originate externally (environmental factors) or internally (metabolic or psychological states), requiring coordinated responses from both the nervous and endocrine systems.
  • Maintaining the listed regulated variables (temperature, BP, pH, glucose, fluid balance) is essential for stable cellular function and overall health.
  • Understanding terminology helps in deciphering clinical terms and classifications related to homeostatic processes and disorders.