Physiology
Learning Objectives
By the end of this section, you should be able to:
- Explain how the human body maintains homeostasis across all major organ systems
- Describe the cellular basis of physiological function including membrane transport and energy production
- Identify the key roles of blood and body fluids in sustaining life processes
- Summarize cardiovascular, respiratory, and renal system functions and their clinical significance
- Connect endocrine and nervous system regulation to whole-body physiology
- Apply physiological principles to interpret common clinical scenarios encountered on the USMLE Step 1
- Distinguish normal physiological parameters from pathological deviations in major organ systems
Quick Answer
Physiology is the scientific study of how living organisms function. In medicine, physiology forms the backbone of clinical reasoning — you cannot understand why a drug works, why a disease causes specific symptoms, or how to interpret a lab result without a solid grasp of normal function. This section covers the full arc of human physiology: from the cell membrane to integrated organ systems. Mastery here directly translates to better performance on USMLE Step 1 and stronger clinical reasoning in clerkships and beyond.
Topics at a Glance
| Topic | Core Concept | Clinical Relevance |
|---|---|---|
| Introduction to Physiology | Definition, branches, and key concepts of physiology | Foundation for all clinical reasoning |
| General Physiology | Cellular structure, homeostasis, energy production | Basis for pharmacology and pathology |
| Blood and Body Fluids | Blood composition, fluid compartments, body fluid regulation | Anemia, dehydration, IV fluid management |
| Cardiovascular System | Heart anatomy, cardiac cycle, blood pressure regulation | Hypertension, heart failure, arrhythmias |
| Respiratory System | Gas exchange, lung mechanics, acid-base | COPD, asthma, respiratory failure |
| Renal System | Filtration, reabsorption, electrolyte balance | AKI, CKD, electrolyte disorders |
| Gastrointestinal System | Digestion, absorption, gut motility | Malabsorption, IBD, liver disease |
| Endocrine System | Hormonal regulation, feedback loops | Diabetes, thyroid disorders, adrenal disease |
| Reproductive System | Gonadal function, menstrual cycle, fertility | Hormonal contraception, infertility, PCOS |
| Neurophysiology | Nerve transmission, synaptic function, CNS | Seizures, neuropathies, neuromuscular disease |
| Muscle Physiology | Contraction mechanism, fiber types, fatigue | Myopathies, exercise physiology |
Key Terms
| Term | Definition | Related Concept |
|---|---|---|
| Homeostasis | The body's ability to maintain a stable internal environment despite external changes | Negative feedback, thermoregulation |
| Negative feedback | A regulatory mechanism where the output of a process reduces the stimulus that caused it | Homeostasis, endocrine regulation |
| Action potential | A rapid, transient change in membrane potential that propagates nerve and muscle signals | Neurophysiology, muscle contraction |
| Cardiac output | Volume of blood the heart pumps per minute (heart rate × stroke volume) | Cardiovascular physiology, shock |
| Glomerular filtration rate (GFR) | The rate at which blood is filtered by the kidneys; marker of renal function | Renal physiology, CKD staging |
| Tidal volume | The volume of air inhaled or exhaled in a single normal breath | Respiratory physiology, ventilation |
| Hematocrit | The percentage of blood volume occupied by red blood cells | Blood composition, anemia diagnosis |
| Osmolarity | The concentration of dissolved particles in a solution, measured in mOsm/L | Fluid compartments, renal regulation |
Related Topics
Prerequisites: Basic biochemistry, cell biology, human anatomy
Related Topics: Pharmacology (drug mechanisms rely on physiological targets), Pathology (disease = disrupted physiology), Biochemistry (metabolic pathways underpin energy production)
Next Topics: Pharmacology, Pathology, Clinical Medicine rotations
This page is for educational purposes. Always verify with current clinical guidelines.