Physiology: Key Concepts in Human Biology

Posted on Jan 28, 2025 in Biology

Hypothesis: A prediction or guess about something that is going to happen. Example: How the amount of makeup affects skin clarity. Scientific Method: Observation, ask a question, hypothesis, experiment (dependent and independent variables), data collection, conclusion. Passive Transport: No ATP needed; movement of substances across a concentration gradient (e.g., osmosis). Active Transport: Requires ATP; moves substances from low to high concentration. Hypertonic: Higher concentration of solutes. Hypotonic: Lower concentration of solutes. Isotonic: Two solutions with equal solute concentrations. Solvent: Liquid that contains dissolved solutes. Solute: Substance dissolved in a solution. Ionic Bonds: Charged atoms become charged by gaining or losing electrons (e.g., NaCl, NaBr). Covalent Bonds: Atoms share pairs of electrons (e.g., H2O and CO2). Polarity: Ability to separate charges; polar substances attract other polar substances. Biomolecules: Lipids, carbohydrates, proteins, nucleotides. Van der Waals Forces: Weak attractive forces between H+ and other H+. Steroid Hormones: Fat-loving (lipophilic); can diffuse in water. Peptide Hormones: Water-loving (lipophobic); cannot cross the membrane (e.g., insulin, glucagon). Amine Hormones: Amino acid derivatives (e.g., adrenaline). Homeostasis: Maintenance of a stable internal environment. Push-Pull Control: Metabolic regulation allowing enzymes to catalyze forward and reverse reactions.

Brain Waves

  • Beta: Awake, normal consciousness
  • SMR: Calm, awake
  • Alpha: Relaxed, calm, not thinking
  • Theta: Deep relaxation, meditation
  • Delta: Deep, dreamless sleep

Transcription: Making an RNA copy. Translation: Process of translating the sequence of RNA. DNA Base Pairing: A-T, T-A, G-C, C-G. mRNA Base Pairing: A-U, T-A, C-G, G-C. tRNA Base Pairing: A-U, U-A

Blood Flow

  1. Superior Vena Cava
  2. Inferior Vena Cava
  3. Tricuspid Valve
  4. Pulmonary Valve
  5. Pulmonary Artery
  6. Pulmonary Vein
  7. Bicuspid Valve
  8. Aortic Valve
  9. Aorta

Blood Pressure: Normal: less than 120 (systolic) and less than 80 (diastolic). Elevated: 120-129 and less than 80. High Blood Pressure: 130-139 and 80-89.


Stroke Volume

Amount of blood pumped by one ventricle during contraction. Calculation: EDV – ESV = Stroke Volume. Depends on: Contractility: Force of heart contraction (more force, more blood ejected). Preload: End-diastolic volume; degree of stretch of myocytes at the end of ventricular diastole. Afterload: Resistance the ventricle must overcome to eject blood. Left ventricle pressure must be greater than systemic pressure; right ventricle pressure must exceed pulmonary pressure to open the pulmonary valve.

Lung Volumes

  • Tidal Volume (TV): Volume of gas inspired or expired in an unforced respiratory cycle.
  • Inspiratory Reserve Volume (IRV): Additional volume above tidal volume.
  • Expiratory Reserve Volume (ERV): Forcefully exhaled volume after a normal expiration.
  • Residual Volume (RV): Volume of air in the respiratory system after maximal exhalation.

Cardiac Cycle

  1. Atrial and Ventricular Diastole: Atria and ventricles relax; atria fill with blood from veins. As ventricles relax, AV valves open, and blood flows from atria to ventricles.
  2. Completion of Ventricular Filling: Atrial Systole: Blood enters ventricles while atria relax.
  3. Early Ventricular Contraction (First Heart Sound): Atria are contracting; depolarization moves to the AV node. AV valves close, preventing blood backflow into the atria, creating the first heart sound.
  4. The Heart Pumps: Ventricular Ejection: As ventricles contract, semilunar valves open, pushing blood into the arteries. AV valves close, and atria continue to fill.
  5. Ventricular Relaxation and Second Heart Sound: Ventricles begin to repolarize and relax.

PV Loop

  1. Mitral Valve Opens
  2. Diastolic Filling
  3. Mitral Valve Closes
  4. Isovolumetric Contraction
  5. Aortic Valve Opens
  6. Ejection
  7. Aortic Valve Closes
  8. Isovolumetric Relaxation
  9. Stroke Volume

Relationship between Volume and Pressure: When volume increases, pressure decreases (assuming other factors remain constant).

Wiggers Diagram

  1. Atrial Contraction
  2. Mitral and Tricuspid Valve Closure
  3. Aortic Valve Opens
  4. Ejection of Blood from Ventricles
  5. Aortic Valve Closure (Second Heart Sound)
  6. Opening of AV Valves
  7. Isovolumic Contraction
  8. Isovolumic Relaxation

Heart Sounds: S1: Mitral valve closing. S2: Aortic valve closing. S3: Blood flows against ventricle during diastole. S4: Blood flows against ventricle during atrial contraction.