Foundations of Human Physiology

HUMAN BIOSCIENCES A: FOUNDATIONS OF HUMAN PHYSIOLOGY

ANATOMY AND PHYSIOLOGY

  • Definition:

    • Human anatomy: The scientific study of the body’s structures.

    • Human physiology: The scientific study of the body’s function.

  • Subdivisions of Anatomy:

    • Gross anatomy: Study of larger structures visible without magnification.

    • Microscopic anatomy: Study of structures visible with a microscope or other magnification devices.

  • Physiology:

    • Physiologists study the chemistry and physics of structures and their functions through laboratory experiments.

    • Structure and function are closely related; understanding structures aids in understanding function.

ORGANIZATION OF THE BODY

  • Levels of Organization:

    • Chemical level: Simplest building blocks of matter (atoms, molecules).

    • Cellular level: Cells are the smallest independently functioning units of living organisms.

    • Most physiological functions initiated/performed at the cellular level.

    • Tissue level: A group of similar cells working together to perform specific functions.

    • Organ level: Distinct structures performing specific physiological functions.

    • Organ system level: Groups of organs working together to perform major functions.

    • Organism level: A living being that can perform all physiological functions independently.

CELLS

  • Characteristics:

    • Basic biological units of the human body.

    • Structure and functions vary depending on the cell type.

  • Common Features of Cells:

    • Cell (plasma) membrane: Protective barrier regulating entry and exit of substances.

    • Nucleus: Control center that stores genetic instructions for protein manufacture.

    • Cytosol: Jelly-like substance providing a medium for biochemical reactions.

CELL STRUCTURE

  • Cell Membrane:

    • Composed of two layers of phospholipids (lipid bilayer).

    • Functions to separate the cell's inner contents from the external environment.

  • Membrane Proteins:

    • Facilitate material passage, cell recognition, receptor functions, and stability/contribute to fluidity.

CELL TRANSPORT

  • Overview:

    • Cell membrane is selectively permeable.

    • Movement across membrane:

    • Passive transport: Does not require energy.

    • Active transport: Requires energy (ATP).

  • Concentration:

    • Defined as the number of solute particles in a given space (e.g., ions, gas molecules).

  • Concentration Gradients:

    • Substances move from areas of higher concentration to lower concentration until evenly distributed.

    • Diffusion: Movement down concentration gradients (passive transport).

PASSIVE TRANSPORT

  • Simple Diffusion:

    • No energy required for small, lipid-soluble molecules (e.g., O2, CO2).

  • Facilitated Diffusion:

    • No energy required; molecules too large or poorly lipid-soluble aided by channels/carriers (e.g., glucose, sodium channels).

ACTIVE TRANSPORT

  • Requires ATP to move substances against their concentration gradient (e.g., sodium-potassium pump).

  • Examples:

    • Important for nervous system function: Na+ and K+ transported against their gradients.

TRANSPORT SUMMARY

  • Overview of transport mechanisms:

    • Simple diffusion: Passive, no energy required.

    • Facilitated diffusion: Passive, no energy required; helper proteins.

    • Active transport: Energy required, substances moved against concentration gradient.

TRANSPORT USING VESICLES

  • Active transport using vesicles allows the transportation of large materials.

    • Endocytosis: "Bringing into the cell" (e.g., phagocytosis, pinocytosis).

    • Exocytosis: "Taking out of the cell"; vesicles fuse with cell membrane.

OSMOSIS

  • Example of passive transport, referring to the diffusion of water through a semi-permeable membrane.

  • Water movement is essential for maintaining cellular environment, requiring equilibrium in solute concentrations.

CLINICAL SIGNIFICANCE OF OSMOSIS

  • Isotonic Solutions: Same concentration of solutes inside and outside the cell; no net water movement.

  • Hypertonic Solutions: Higher concentration of solutes outside the cell; water moves out of the cell, potentially causing cell shrinkage.

  • Hypotonic Solutions: Lower concentration of solutes outside the cell; water moves into the cell, risking cell swelling and bursting.

ORGANELLES

  • Membrane-enclosed structures in cells, performing unique functions vital for cell health.

    • Organelles make up around half the total cell volume.

DNA & PROTEINS

  • DNA: Blueprint for cell structure and physiology, containing genetic instructions to build proteins.

  • Protein Synthesis:

    • Two stages: Transcription in the nucleus and Translation in the cytoplasm.

    • mRNA carries the genetic code for protein synthesis.

CELLULAR DIFFERENTIATION

  • Process by which unspecialized cells become specialized to perform distinct functions.

  • Stages of differentiation lead to unique cell types (e.g., red blood cells vs. neurons).

STEM CELLS

  • Unspecialized cells capable of dividing and differentiating into various cell types.

  • Types: Embryonic, fetal, and adult stem cells, each serving different roles in development and tissue repair.

SPECIALIZATION

  • Cell specialization alters size, shape, metabolic activity, and function, governed by gene activation relevant to cell type.

STEM CELL RESEARCH

  • Aims to utilize stem cells for regenerative therapies while navigating ethical considerations surrounding embryonic stem cell use.

COMMUNICATION

  • Cells maintain vital interactions with their environment via complex signaling mechanisms.

  • Chemical Signaling: Involves signaling molecules that diffuse through extracellular space to target cells, eliciting responses.

TYPES OF TISSUES

  • Divided into four categories:

    • Epithelial Tissue: Covers surfaces, exhibits polarity, and regulates substance passage.

    • Connective Tissue: Includes diverse cell types within a matrix, supporting body structure and connection.

    • Muscle Tissue: Excitable and contractile, facilitating movement.

    • Nervous Tissue: Enables communication via signals between neurons and supports cell functions.

HOMEOSTASIS

  • The state of steady internal conditions maintained by living organisms, crucial for normal function, including temperature and pH balance.

  • Set Point: Physiological value where a normal range fluctuates, monitored via negative feedback systems.

  • Feedback Mechanisms:

    • Negative Feedback: Reverses deviations from set points (e.g., temperature regulation).

    • Positive Feedback: Intensifies physiological changes (e.g., childbirth).

ORGANIC MOLECULES

  • Carbohydrates: Sugars and starches vital for energy and structural components.

  • Lipids: Essential for energy storage, cellular structures (e.g., phospholipids), and hormone production.

  • Proteins: Composed of amino acids, crucial for structure, function, regulation, and enzyme activity in cells.

ORGANELLE

  • Lysosome (Clean up crew ): An organelle that digests unwanted cellular materials and helps in recycling components.

  • Mitochondria: Known as the powerhouse of the cell, mitochondria generate ATP through cellular respiration, providing energy necessary for cellular activities.

  • Smooth Endoplasmic Reticulum (ER): A membrane-bound organelle involved in lipid synthesis and detoxification processes in the cell. ( Rough ER: A membrane-bound organelle studded with ribosomes, responsible for protein synthesis and processing.

  • Mitchochondria: Double-membraned organelles known as the "powerhouses of the cell" because they generate ATP through oxidative phosphorylation and regulate cellular metabolism.

  • Golgi Apparatus: A membrane-bound structure that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles. Lysosomes: Membrane-bound organelles containing enzymes that break down waste materials and cellular debris, playing a key role in cellular digestion and recycling.

  • Ribosome: The molecular machines responsible for synthesizing proteins by translating messenger RNA (mRNA) into polypeptide chains.

  • Rough endopasmic reticulum(RER): A type of endoplasmic reticulum studded with ribosomes, responsible for the synthesis of proteins that are either secreted from the cell or sent to an organelle.

Negative feedback: A regulatory mechanism in which a system's output acts to reduce or dampen the processes leading to the output of that system, thus helping to maintain homeostasis within the cell.