1. Fundamentals of Human Biology and Physiology
To understand health and medicine, we first need to look at how the body
functions at a fundamental level. Human physiology is structured in hierarchical
layers:
* **Cellular Level:** The basic unit of life. Cells utilize oxygen and nutrients to
create adenosine triphosphate (ATP)—the body's energy currency—via cellular
respiration.
* **Tissue Level:** Groupings of similar cells working together (e.g., epithelial,
connective, muscle, and nervous tissue).
* **Organ & System Level:** Complex groups of tissues performing dedicated
functions.
### Major Body Systems
1. **Cardiovascular System:** Circulates oxygen, nutrients, and hormones while
removing metabolic waste. Powered by the heart, which pumps blood through a
network of arteries, capillaries, and veins.
2. **Respiratory System:** Facilitates gas exchange (O_2 in, CO_2 out) through
the lungs, relying on pressure differentials created by the diaphragm.
3. **Nervous System:** The body's command center, split into the **Central
Nervous System (CNS)** (brain and spinal cord) and the **Peripheral Nervous
System (PNS)**. It uses electrochemical signals to process stimuli and
coordinate responses.
4. **Endocrine System:** Regulates long-term body processes (metabolism,
growth, sleep, stress) using hormones released directly into the bloodstream by
glands like the thyroid, adrenal, and pancreas.
5. **Digestive System:** Breaks down food mechanically and chemically to
absorb macronutrients (carbohydrates, proteins, fats) and micronutrients
(vitamins, minerals).
6. **Immune System:** A defense network of cells (leukocytes, T-cells, B-cells),
tissues, and organs that identifies and neutralizes pathogens.
## 2. Disease Mechanisms and Pathology
Pathology is the study of disease—specifically, how normal physiological
processes break down. Diseases generally fall into a few primary categories:
### Infectious Diseases
Caused by external organisms invading the host:
* **Bacteria:** Single-celled prokaryotes (e.g., *Staphylococcus*,
*Streptococcus*). Many are harmless or beneficial, but pathogenic strains
produce toxins or destroy tissue.
* **Viruses:** Non-living genetic code (DNA or RNA) wrapped in protein that
hijacks host cell machinery to replicate (e.g., Influenza, SARS-CoV-2).
* **Fungi & Parasites:** Eukaryotic organisms ranging from microscopic yeast
to multi-cellular worms.
### Non-Communicable & Chronic Diseases
* **Cardiovascular Disease (CVD):** Atherosclerosis (buildup of fatty plaques in
arteries) restricts blood flow, leading to hypertension, heart attacks, or strokes.
* **Cancer:** Uncontrolled cell division caused by genetic mutations. Cancerous
To understand health and medicine, we first need to look at how the body
functions at a fundamental level. Human physiology is structured in hierarchical
layers:
* **Cellular Level:** The basic unit of life. Cells utilize oxygen and nutrients to
create adenosine triphosphate (ATP)—the body's energy currency—via cellular
respiration.
* **Tissue Level:** Groupings of similar cells working together (e.g., epithelial,
connective, muscle, and nervous tissue).
* **Organ & System Level:** Complex groups of tissues performing dedicated
functions.
### Major Body Systems
1. **Cardiovascular System:** Circulates oxygen, nutrients, and hormones while
removing metabolic waste. Powered by the heart, which pumps blood through a
network of arteries, capillaries, and veins.
2. **Respiratory System:** Facilitates gas exchange (O_2 in, CO_2 out) through
the lungs, relying on pressure differentials created by the diaphragm.
3. **Nervous System:** The body's command center, split into the **Central
Nervous System (CNS)** (brain and spinal cord) and the **Peripheral Nervous
System (PNS)**. It uses electrochemical signals to process stimuli and
coordinate responses.
4. **Endocrine System:** Regulates long-term body processes (metabolism,
growth, sleep, stress) using hormones released directly into the bloodstream by
glands like the thyroid, adrenal, and pancreas.
5. **Digestive System:** Breaks down food mechanically and chemically to
absorb macronutrients (carbohydrates, proteins, fats) and micronutrients
(vitamins, minerals).
6. **Immune System:** A defense network of cells (leukocytes, T-cells, B-cells),
tissues, and organs that identifies and neutralizes pathogens.
## 2. Disease Mechanisms and Pathology
Pathology is the study of disease—specifically, how normal physiological
processes break down. Diseases generally fall into a few primary categories:
### Infectious Diseases
Caused by external organisms invading the host:
* **Bacteria:** Single-celled prokaryotes (e.g., *Staphylococcus*,
*Streptococcus*). Many are harmless or beneficial, but pathogenic strains
produce toxins or destroy tissue.
* **Viruses:** Non-living genetic code (DNA or RNA) wrapped in protein that
hijacks host cell machinery to replicate (e.g., Influenza, SARS-CoV-2).
* **Fungi & Parasites:** Eukaryotic organisms ranging from microscopic yeast
to multi-cellular worms.
### Non-Communicable & Chronic Diseases
* **Cardiovascular Disease (CVD):** Atherosclerosis (buildup of fatty plaques in
arteries) restricts blood flow, leading to hypertension, heart attacks, or strokes.
* **Cancer:** Uncontrolled cell division caused by genetic mutations. Cancerous
