Chapter 1: Introduction to Physiology Vocabulary

Chapter 1: Introduction to Physiology

Physiology

• Physiology is the study of the function of the body.

• Subdivisions are based on organ systems (e.g., renal or cardiovascular physiology).

• Often focuses on the cellular and molecular level.

• The body's abilities depend on chemical reactions in individual cells.

Anatomy and Physiology

• Anatomy and physiology are inseparable.

• Function always reflects structure.

• What a structure can do depends on its specific form.

• Principle of Complementarity: Structure and function are complementary.

Levels of Structural Organization

• Chemical Level:

  • Atoms, molecules, organelles

• Cellular Level:

  • Cells

• Tissue Level:

  • Groups of similar cells

• Organ Level:

  • Contains two or more types of tissues

• Organ System Level:

  • Organs that work closely together

• Organismal Level:

  • All organ systems

Organ Systems of the Human Body and Their Integration

• Circulatory System:

  • Organs: Heart, blood vessels, blood

  • Function: Transport of materials between all cells of the body

• Digestive System:

  • Organs: Stomach, intestine, liver, pancreas

  • Function: Conversion of food into particles that can be transported into the body; elimination of some wastes

• Endocrine System:

  • Organs: Thyroid gland, adrenal gland

  • Function: Coordination of body function through synthesis and release of regulatory molecules

• Immune System:

  • Organs: Thymus, spleen, lymph nodes

  • Function: Defense against foreign invaders

• Integumentary System:

  • Organs: Skin

  • Function: Protection from external environment

• Musculoskeletal System:

  • Organs: Skeletal muscles, bone

  • Function: Support, movement

• Nervous System:

  • Organs: Brain, spinal cord

  • Function: Coordination of body function through electrical signals and release of regulatory molecules

• Reproductive System:

  • Organs: Ovaries and uterus, testes

  • Function: Perpetuation of the species

• Respiratory System:

  • Organs: Lungs, airways

  • Function: Exchange of oxygen and carbon dioxide between the internal and external environments

• Urinary System:

  • Organs: Kidneys, bladder

  • Function: Maintenance of water and solutes in the internal environment; waste removal

Themes in Physiology

1. Structure and function are closely related.

2. Living organisms need energy.

3. Information flow coordinates body function.

4. Homeostasis maintains internal stability.

Structure and Function

• Molecular interactions involve proteins.

  • Enzymes: speed up chemical reactions.

  • Signal molecules and receptor proteins: bind signal molecules; also act as pumps, filters, motors, and transporters.

  • Interactions influence cell structure and mechanical properties of cells and tissues

• Compartmentation: Allows cells and tissues to specialize and isolate functions.

Living Organisms Need Energy

• Processes which require energy: growth, reproduction, movement, and homeostasis.

• Energy is used to transport molecules across membranes and to create movement.

Information Flow Coordinates Body Functions

• Includes:

  • Translation of the genetic code into proteins for cell structure.

  • Cell to cell communication

• Information flow occurs as chemical or electrical signals.

• Membranes are selectively permeable.

Homeostasis

• Homeostasis: Maintenance of relatively stable internal conditions despite continuous changes in environment

• A dynamic state of equilibrium.

• Maintained by contributions of all organ systems.

• Nervous and endocrine systems accomplish communication via nerve impulses and hormones.

Homeostasis - Components

• Receptor: Receives the stimulus.

• Control center: Processes the signal and sends instructions.

• Effector: Carries out instructions.

Local vs. Reflex Control

• Local Control: Cells in the vicinity of the change initiate the response.

• Reflex Control: Cells at a distant site control the response.

  • Brain evaluates the change and initiates a response.

Negative Feedback

• Response reduces or shuts off original stimulus.

• Variable changes in opposite direction of initial change.

• Examples:

  • Regulation of body temperature (a nervous system mechanism).

  • Regulation of blood glucose by insulin (an endocrine system mechanism).

Negative Feedback: Control of Body Temperature

• Normal temperature disturbed.

• Receptors: Temperature sensors in skin and hypothalamus.

• Control Center: Thermoregulatory center in brain.

• Effectors:

  • Sweat glands in skin increase secretion.

  • Blood vessels in skin dilate.

• Response: Increased heat loss, body temperature drops.

• Normal temperature restored.

• The thermoregulatory center keeps body temperature fluctuating within an acceptable range, usually between 36.7 and 37.2 °C.

Positive Feedback

• Response enhances or exaggerates original stimulus.

• May exhibit a cascade or amplifying effect.

• Usually controls infrequent events that do not require continuous adjustment.

• Examples:

  • Enhancement of labor contractions by oxytocin.

  • Platelet plug formation and blood clotting.

Positive Feedback: Blood Clotting

• Damage to cells in the blood vessel wall releases chemicals that begin the process of blood clotting.

• As clotting continues, each step releases chemicals that further accelerate the process.

• This escalating process is a positive feedback loop that ends with the formation of a blood clot, which patches the vessel wall and stops the bleeding.

Positive Feedback: Labor Contractions

• Baby drops lower in uterus to initiate labor.

• Baby pushes against cervix.

• Cervical stretch stimulates oxytocin release.

• Oxytocin causes uterine contractions.

• Delivery of baby stops the cycle.

Homeostatic Imbalance

• Disturbance of homeostasis.

• Increases risk of disease.

• Contributes to changes associated with aging.

• Control systems less efficient.

• If negative feedback mechanisms overwhelmed.

• Destructive positive feedback mechanisms may take over (e.g., heart failure).

Roles of Organ Systems in Homeostatic Regulation