Human Physiology – Study Notes
(For ANM Admission – Biology)
Purpose – To give you a quick yet comprehensive refresher on the key concepts of human physiology, with a focus on the body systems most relevant to nursing and mid‑wifery practice.
1. Simple Explanation
Human physiology is the science that explains how the human body works. It covers the structure and function of the major organ systems, the interactions between them, and how the body maintains homeostasis (a stable internal environment) despite external changes.
Homeostasis
Goal: Keep variables (temperature, pH, glucose, etc.) within a narrow range.
Mechanisms: Negative feedback loops, hormonal regulation, neural control, and behavioral adjustments.
2. Key Points – By Body System
| System | Main Function | Key Organs | Important Concepts |
|---|---|---|---|
| Circulatory | Transport oxygen, nutrients, hormones; remove waste | Heart, blood vessels, blood | Cardiac cycle, blood pressure, oxygen‑hemoglobin dissociation |
| Respiratory | Gas exchange (O₂ ↔ CO₂) | Lungs, trachea, bronchi | Alveolar ventilation, V/Q matching, respiratory rate control |
| Digestive | Break down food, absorb nutrients | Mouth, stomach, small/large intestine | Enzymatic digestion, absorption sites, peristalsis |
| Excretory | Remove metabolic waste | Kidneys, ureters, bladder | Glomerular filtration, tubular reabsorption/secretion, urine concentration |
| Endocrine | Coordinate body functions via hormones | Pituitary, thyroid, adrenal, pancreas | Hormone synthesis, secretion, target cell receptors, negative feedback |
| Reproductive | Produce offspring | Ovaries/testes, uterus, external genitalia | Menstrual cycle, fertilization, pregnancy physiology |
| Nervous | Control & integration | Brain, spinal cord, peripheral nerves | Reflex arcs, neurotransmission, autonomic nervous system (sympathetic/parasympathetic) |
| Integumentary | Protect, regulate temperature, sense | Skin, hair, nails | Skin layers, sweat glands, thermoregulation |
Quick Highlights
| System | 2‑Word Summary | Clinical Relevance |
|---|---|---|
| Circulatory | Blood transport | CHF, hypertension |
| Respiratory | Gas exchange | Asthma, COPD |
| Digestive | Nutrient absorption | GI bleeding, malnutrition |
| Excretory | Waste removal | Kidney failure, dehydration |
| Endocrine | Hormonal balance | Diabetes, thyroid disorders |
| Reproductive | Pregnancy | ANC, labor management |
| Nervous | Control center | Seizures, pain management |
| Integumentary | Barrier | Burns, skin infections |
3. Worked Example – Calculating Oxygen Consumption (VO₂)
Scenario:
A 30‑year‑old woman (weight 60 kg) is resting in the clinic. She presents with mild shortness of breath. Her pulse is 78 bpm and her peripheral oxygen saturation (SpO₂) is 96 %.
Goal: Estimate her resting VO₂ (ml O₂ min⁻¹) and check if it is within normal range (~3.5 ml kg⁻¹ min⁻¹).
Step‑by‑Step
-
Find Resting VO₂ per kg
Normal resting VO₂ ≈ 3.5 ml kg⁻¹ min⁻¹. -
Calculate Total Resting VO₂
[ \text{VO₂ (total)} = 3.5 \times 60 = 210 \text{ ml min⁻¹} ] -
Use the Fick Equation (optional for deeper understanding)
[ \text{VO₂} = Q \times (CaO₂ - CvO₂) ] Where:- ( Q ) = cardiac output (L min⁻¹)
- ( CaO₂ ) = arterial oxygen content (ml O₂ L⁻¹)
- ( CvO₂ ) = venous oxygen content
Assuming cardiac output 5 L min⁻¹ and oxygen extraction 25 %:
[ \text{VO₂} = 5 \times (0.25 \times 150) = 187.5 \text{ ml min⁻¹} ] (Close to our estimated 210 ml min⁻¹; slight variation due to assumptions.) -
Interpretation
- 210 ml min⁻¹ is within the normal resting range for a healthy adult.
- If her VO₂ were > 250 ml min⁻¹, it might indicate increased metabolic demand or cardiac compromise.
-
Clinical Take‑away
- Normal VO₂ → likely no cardiac/respiratory pathology.
- Mild dyspnea may be due to anxiety or deconditioning.
- Monitor pulse, SpO₂, and perform a brief physical exam.
4. Quick Revision Summary
- Homeostasis is maintained by negative feedback loops (e.g., insulin‑glucose, thyroid hormone‑TRH).
- Circulatory System: Heart (4 chambers), arterial‑venous pressure, oxygen‑hemoglobin curve.
- Respiratory System: Alveolar ventilation, V/Q ratio, CO₂ removal, pH regulation (respiratory vs. renal).
- Digestive System: Enzymes (pepsin, trypsin, lipase), nutrient absorption sites (jejunum, ileum).
- Excretory System: Glomerular filtration rate, tubular reabsorption (Na⁺,