Characteristics of Life and Cellular Processes

Defining Features of Living Organisms

• Cellular Composition: All living organisms are made up of cells, the smallest units capable of life functions.

• Metabolism: The sum of all chemical processes that occur within a living organism.

  • Anabolism: Building larger molecules from smaller ones.

  • Catabolism: Breaking down larger molecules into smaller ones.

• Growth: Increase in cell size or number due to anabolism exceeding catabolism.

• Excretion: Removal of waste products generated by metabolic processes.

• Responsiveness: Ability to sense and react to environmental changes (stimuli).

• Movement: Internal movement within cells and external movement of the organism.

• Reproduction: Production of new cells for growth or creating offspring.

Levels of Organization in the Human Body

Major Structural Levels

• Chemical Level: Atoms and molecules, including phospholipids and proteins.

• Cellular Level: Molecules combine to form cells, the basic unit of life.

• Tissue Level: Similar cells and their extracellular matrix form tissues (e.g., epithelial tissue).

• Organ Level: Tissues combine to form organs (e.g., stomach, lungs).

• Organ System Level: Organs work together in systems (e.g., digestive system).

• Organism Level: All organ systems working together to make a complete human.

Types of Anatomy and Physiology

Branches of Anatomy

• Systemic Anatomy: Focuses on individual organ systems (e.g., cardiovascular system).

• Regional Anatomy: Examines specific regions (e.g., head, abdomen).

• Surface Anatomy: Studies external features and markings.

• Gross Anatomy: Structures visible to the naked eye.

• Microscopic Anatomy: Uses microscopes to study structures.

  • Histology: Study of tissues.

  • Cytology: Study of cells.

Branches of Physiology

• Neurophysiology: Studies the brain and nervous system.

• Cardiovascular Physiology: Focuses on the heart and blood vessels.

• Other Specializations: May include cellular processes or specific tissues.

Organ Systems of the Human Body

Major Organ Systems and Their Components

• Integumentary System: Skin, hair, nails; protects the body, produces vitamin D, retains water, regulates temperature.

• Skeletal System: Bones and joints; supports and protects organs, facilitates movement, produces blood cells, stores calcium.

• Muscular System: Skeletal, smooth, and cardiac muscles; enables movement, controls body openings, generates heat.

• Nervous System: Brain, spinal cord, nerves; regulates body functions, transmits nerve impulses.

• Endocrine System: Glands (thyroid, pancreas); secretes hormones to regulate body functions.

• Cardiovascular System: Heart, blood vessels; transports oxygen, nutrients, and removes wastes.

• Lymphatic System: Lymph nodes, vessels; supports immunity, returns tissue fluid to blood.

• Respiratory System: Lungs, airways; delivers oxygen, removes carbon dioxide, maintains acid-base balance.

• Digestive System: Stomach, intestines; digests food, absorbs nutrients, eliminates waste.

• Urinary System: Kidneys, bladder; removes waste, regulates water and electrolyte balance.

• Reproductive System: Organs for reproduction in males and females.

Anatomical Position and Directional Terms

Standard Anatomical Position

• Standing upright

• Feet shoulder-width apart

• Arms at the side

• Head facing forward

• Palms facing forward

Major Directional Terms

• Anterior/Posterior: Front/back of the body

• Superior/Inferior: Toward the head/toward the tail

• Proximal/Distal: Closest to/farthest from the point of origin

• Medial/Lateral: Closer to/farther from the midline

• Superficial/Deep: Closer to/farther from the surface

Body Regions and Planes

Major Anatomical Regions

• Axial Region: Head, neck, trunk (thoracic, abdominal, pelvic)

• Appendicular Region: Upper and lower limbs

Body Planes

• Sagittal Plane: Divides body into right and left sections

  • Midsagittal: Equal right and left halves

  • Parasagittal: Unequal right and left sections

• Frontal (Coronal) Plane: Divides body into anterior (front) and posterior (back) sections

• Transverse (Horizontal) Plane: Divides body into superior (upper) and inferior (lower) parts

Body Cavities and Membranes

Major Body Cavities

• Anterior (Ventral) Body Cavity:

  • Thoracic Cavity: Above the diaphragm

    • Pleural Cavities: Surround each lung

    • Mediastinum: Contains heart, blood vessels, trachea, esophagus

    • Pericardial Cavity: Surrounds the heart

  • Abdominopelvic Cavity: Below the diaphragm

    • Abdominal Cavity: Digestive organs

    • Pelvic Cavity: Reproductive organs, bladder, large intestine

• Posterior (Dorsal) Body Cavity:

  • Cranial Cavity: Brain

  • Vertebral (Spinal) Cavity: Spinal cord

Serous Membranes

• Thin tissues lining internal cavities, providing a smooth, frictionless surface.

• Consist of parietal (lines cavity walls) and visceral (covers organs) layers.

• Filled with serous fluid to reduce friction.

Types of Serous Membranes

Homeostasis and Feedback Mechanisms

Principle of Homeostasis

• Maintaining stable internal conditions despite external changes.

• Involves regulating variables like temperature, blood pressure, and blood sugar.

Feedback Loops

• Negative Feedback: Opposes initial stimulus to return variable to normal range.

  • Example: Body temperature regulation—sweating cools the body when temperature rises.

  • Function: Promotes stability by negating changes.

• Positive Feedback: Amplifies initial stimulus.

  • Example: Blood clotting—chemicals amplify the process until clotting is complete.

  • Function: Causes rapid changes, useful in processes needing a definitive outcome.

Components of a Feedback Loop

• Regulated Variable: The variable maintained within a certain range (e.g., temperature).

• Receptor: Detects changes in the regulated variable.

• Control Center: Receives information and determines the response.

• Effector: Carries out the response to restore balance.

• Normal Range: The range within which the variable should be maintained.

Structure and Function Relationship

• The shape and structure of a body part are designed for its specific function (principle of complementarity).

• Example: Thin structure of lung tissue allows for rapid gas exchange.

Gradients in Physiology

Types of Gradients

• Temperature Gradient: Difference in temperature between two areas.

• Concentration Gradient: Difference in concentration of a substance between two areas.

• Pressure Gradient: Difference in pressure between two areas.

• Gradients drive many physiological processes (e.g., diffusion, blood flow).

Cell Communication and Homeostasis

• Cells communicate to coordinate functions and maintain homeostasis.

• Electrical Signals: Transmitted directly between neighboring cells (e.g., nerve to muscle cell).

• Chemical Messengers: Hormones and neurotransmitters released into the surrounding fluid or bloodstream.

• Coordination: Ensures efficient functioning of body systems.

• Homeostasis: Maintains stable internal conditions by adjusting physiological processes.