Biomedical Engineering I Unit 2 Review: Fundamentals of Human Physiology

Key Concepts and Terminology

• Homeostasis maintains stable internal environment despite external changes
• Negative feedback loops restore deviations back to set point
• Positive feedback loops amplify changes leading to new state
• Cells are basic structural and functional units of living organisms
• Tissues are groups of cells with similar structure and function working together
• Organs are composed of multiple tissue types performing specific functions
• Organ systems consist of multiple organs collaborating to carry out complex tasks
• Physiology studies how living systems function at molecular, cellular, and organismal levels

Homeostasis and Feedback Systems

• Homeostasis dynamically regulates internal conditions (temperature, pH, glucose levels)
• Negative feedback systems detect deviations from set point and initiate corrective actions
  • Thermoregulation maintains core body temperature around 37°C (98.6°F)
  • Blood glucose regulation keeps levels within normal range of 70-110 mg/dL
• Positive feedback systems amplify initial stimulus leading to rapid physiological changes
  • Oxytocin release during childbirth stimulates uterine contractions, further increasing oxytocin levels
• Feedback loops involve receptors, control centers, and effectors
• Disruption of homeostatic mechanisms can lead to disease states (diabetes, hypertension)

Cell Structure and Function

• Cells contain organelles with specialized functions
  • Nucleus houses genetic material (DNA) and controls cellular activities
  • Mitochondria generate ATP through cellular respiration
  • Endoplasmic reticulum synthesizes and transports proteins and lipids
  • Golgi apparatus modifies, packages, and distributes proteins and lipids
• Plasma membrane separates cell interior from external environment
  • Selectively permeable, regulating transport of molecules in and out of cell
  • Membrane proteins serve as receptors, channels, and enzymes
• Cytoskeleton provides structural support and enables cell movement
• Cells communicate through chemical signaling (hormones, neurotransmitters) and direct contact (gap junctions)

Tissue Types and Organization

• Epithelial tissue covers body surfaces and lines cavities
  • Simple epithelia have single layer of cells (squamous, cuboidal, columnar)
  • Stratified epithelia have multiple cell layers (keratinized in skin)
• Connective tissue supports and connects other tissues
  • Loose connective tissue (adipose, areolar) has abundant extracellular matrix
  • Dense connective tissue (tendons, ligaments) has high collagen content
  • Specialized connective tissues include cartilage, bone, and blood
• Muscle tissue enables movement and force generation
  • Skeletal muscle attaches to bones and is under voluntary control
  • Smooth muscle lines hollow organs and is involuntarily controlled
  • Cardiac muscle forms heart wall and has unique contraction properties
• Nervous tissue transmits electrical signals for communication and control
  • Neurons are specialized cells that conduct action potentials
  • Glial cells support and protect neurons (astrocytes, oligodendrocytes, Schwann cells)

Major Organ Systems Overview

• Integumentary system (skin, hair, nails) provides barrier protection and thermoregulation
• Skeletal system supports body structure, enables movement, and produces blood cells
• Muscular system generates force for movement, maintains posture, and produces heat
• Nervous system processes sensory information, controls body functions, and enables cognition
• Endocrine system secretes hormones for long-distance communication and regulation
• Cardiovascular system transports oxygen, nutrients, and waste products throughout body
• Lymphatic system returns interstitial fluid to blood and plays role in immune defense
• Respiratory system exchanges gases between air and blood in lungs
• Digestive system breaks down food, absorbs nutrients, and eliminates waste
• Urinary system filters blood, regulates fluid and electrolyte balance, and excretes urine
• Reproductive system produces gametes and enables sexual reproduction

Physiological Processes and Mechanisms

• Membrane transport moves molecules across cell membranes
  • Passive transport (diffusion, osmosis) occurs down concentration gradient without energy input
  • Active transport (pumps, cotransport) moves molecules against concentration gradient using ATP
• Signal transduction converts extracellular signals into intracellular responses
  • Receptor binding triggers cascades of enzymatic reactions and second messengers (cAMP, calcium)
  • Phosphorylation and dephosphorylation regulate protein activity
• Action potentials are electrical signals that propagate along neuron membranes
  • Depolarization opens voltage-gated sodium channels, causing rapid influx of sodium ions
  • Repolarization involves potassium efflux and sodium channel inactivation
• Synaptic transmission communicates signals between neurons
  • Neurotransmitters released from presynaptic neuron bind to postsynaptic receptors
  • Excitatory neurotransmitters (glutamate) depolarize postsynaptic membrane; inhibitory neurotransmitters (GABA) hyperpolarize it
• Muscle contraction generates force through sliding filament mechanism
  • Myosin heads bind to actin filaments and pull them toward center of sarcomere
  • Calcium release from sarcoplasmic reticulum triggers contraction; reuptake causes relaxation

Clinical Applications and Relevance

• Understanding physiology is essential for diagnosing and treating diseases
• Electrophysiology techniques (EKG, EEG) monitor electrical activity of heart and brain
• Imaging modalities (X-ray, CT, MRI) visualize anatomical structures and physiological processes
• Drug development targets specific receptors, enzymes, or signaling pathways to modulate physiology
  • Beta-blockers reduce heart rate and blood pressure by blocking adrenergic receptors
  • Statins lower cholesterol levels by inhibiting HMG-CoA reductase enzyme
• Gene therapy aims to correct genetic defects by introducing functional genes into cells
• Tissue engineering creates biological substitutes to replace damaged or diseased tissues
  • Scaffolds provide structural support for cell growth and differentiation
  • Stem cells have potential to regenerate various tissue types

Challenges and Future Directions

• Complexity of biological systems makes it challenging to understand and manipulate physiology
• Interplay between genetic, environmental, and lifestyle factors influences health and disease
• Personalized medicine tailors treatments based on individual genetic and physiological profiles
• Systems biology integrates data from multiple levels (genes, proteins, cells, organs) to model complex physiological processes
• Computational modeling and simulation help predict physiological responses and guide experimental design
• Organ-on-a-chip technologies recapitulate human physiology in vitro for drug testing and disease modeling
• Advances in genome editing (CRISPR-Cas9) enable precise modification of genetic sequences
• Ethical considerations arise when manipulating human physiology and applying new technologies