Notes, summaries, assignments, exams, and problems for Biology

Week 1: The Heart

Purpose of the Cardiovascular System

To provide adequate blood flow to all tissues/organs according to immediate needs.

Heart Contractions

• Systole: Periods of contraction
• Diastole: Periods of relaxation

Note: The atria contract simultaneously, followed by simultaneous ventricular contraction.

Blood Vessels

• Arteries: Carry blood away from the heart.
• Veins: Carry blood towards the heart.

Intrinsic Conduction System

1. Sinoatrial (SA) Node (Pacemaker): Generates impulses in the right atrial wall. Depolarizes 80-100 times per minute, modified by the autonomic nervous system to approximately 75 times per minute.
2. Atrioventricular (AV) Node: Impulses pause here for 0.1 seconds, allowing the atria to complete contraction. Generates impulses 40-60

Cells are open systems – they exchange both matter and energy with their environment.

Cellular Open Systems: Examples of Exchange

• In: Water, oxygen, nutrients, solar energy (in plants)
• Out: Carbon dioxide, waste, thermal energy, kinetic energy

Cellular Needs and Organ System Functions

Surface Area to Volume Ratio (SA:V)

Cells work best with a high SA:V ratio (more membrane per unit of volume).

• Small cells = high SA:V → efficient transport
• Large cells = low SA:V → less efficient

SA:V Ratio Calculation Formulas

• Surface Area of cube:

Lymphocyte Migration and Immune Response

Lymphocytes constantly migrate through the blood and lymph, moving from one lymphoid organ to another. This process:

• Enhances the chance that an antibody will encounter its specific antigen.
• The spleen filters blood, while other lymphoid organs filter lymph.

Phagocytosis: A Non-Specific Innate Immune Response

Phagocytosis is the ingestion of microorganisms or particulate matter by a cell. It is performed by phagocytes, which are certain types of white blood cells or their derivatives.

Actions of Phagocytic Cells

1. Among the granulocytes, neutrophils are the most important phagocytes.
2. Enlarged monocytes transform into wandering macrophages and fixed macrophages.
3. Fixed macrophages are located in selected tissues

Local Inflammation

1. Occurs when bacteria enter a break in the skin.
2. Inflammatory reaction is initiated by nonspecific mechanisms of phagocytosis and complement activation.
3. Complement activation attracts phagocytes to the area.
4. As inflammation progresses, B cells produce antibodies against bacterial antigens.
5. Attachment of antibodies to antigens amplifies nonspecific responses because of complement activation.
6. Promotes phagocytic activity of neutrophils, macrophages, and monocytes (through opsonization).
7. In the inflamed area, leukocytes attach to the surface of endothelial cells.
8. Move by chemotaxis to the inflamed site.

• Neutrophils arrive first, then monocytes, then T cells.
  • Undergo extravasation (the entire process of movement of leukocytes from the bloodstream

Alright, let’s make Cell Structure & Cell Theory feel alive—less textbook, more story 👇

What is a Cell? The Mini City of Life

A cell is the tiniest unit of life—like a mini city that keeps everything running.
Your body isn’t one big thing; it’s a community of trillions of cells, each doing its own job but working together so you can breathe, think, move, and feel.

The Three Fundamental Rules of Cell Theory

Cell theory is basically biology’s ground rules. Three simple but powerful ideas:

1. All Living Things Are Composed of Cells

From a tiny bacterium to a giant banyan tree to you—everything alive is built from cells.
Some organisms have one cell, others have millions or trillions, but no cell = no life.

2. The Cell Is the Basic

1. Homeostasis and Ecology

• 1(a) Maintaining constant internal conditions.
• 1(b) 250 hours.
• 1(c)(i) A.
• 1(c)(ii) Fertilisers from farms run off into rivers. This causes algal growth. Less light penetrates, reducing photosynthesis. Pesticides kill organisms.
• 1(d)(i) Low FSH: eggs do not mature.
• 1(d)(ii) Low LH: no ovulation.
• 1(e)(i) Less water is absorbed into the blood. Water moves by osmosis because water potential remains higher in the blood.
• 1(e)(ii) Mutation. Only resistant bacteria survive. They reproduce and pass on the allele.
• 1(f)(i) Denitrifying bacteria convert nitrate to nitrogen gas. This reduces algal growth, so there is more oxygen in rivers.
• 1(f)(ii) Roots absorb water. More transpiration occurs, leading to slower water flow and less runoff.

Understanding Feeding and Nutrition

Feeding vs. Nutrition: Key Differences

• Feeding (Eating): Subjective, voluntary, and conscious actions related to consuming food.
• Nutrition (Nourishing): Involuntary, unconscious, and objective processes involving the assimilation of nutrients by the body.

Essential Nutrients: Organic and Inorganic

Nutrients are classified based on whether they contain carbon (C).

Inorganic Nutrients

These nutrients do not contain carbon (C). They are vital for bodily functions.

• Water: Essential for all chemical reactions in the body.
• Mineral Salts: Essential inorganic nutrients needed in small amounts.

Organic Nutrients

These nutrients contain carbon (C). They provide energy and building blocks for the body.

• Carbohydrates: Provide fast

Bone Lesions

Cemento-ossifying Fibroma

• Masses of poorly cellular cementum
• Fibro-cellular connective tissue

Central Giant Cell Lesion

• Multinucleated giant cells
• Areas of hemorrhage
• Loose vascular connective tissue rich in mononuclear cells

Facial Fibrous Dysplasia: Osseous Stage

• Dysplastic fibrous tissue
• Trabeculae of woven bone without peripheral osteoblastic rimming
• Trabeculae are equidistant from each other, taking the shape of C, U, or W letters (Chinese letter appearance)
• Retraction of dysplastic fibrous tissue from woven bone trabeculae
• Presence of blood vessels

Facial Fibrous Dysplasia: Osteoid Stage

• Trabeculae of osteoid bone laid down equidistant from each other
• Characteristic C, U, or W letter shapes and Chinese letter appearance

Malignant Neoplasms

Fibrosarcoma

• Malignant

Joints: Definition and Classification

A joint, also known as an articulation, is the point where two or more bones meet. Joints allow for movement, flexibility, and support in the skeletal system.

Classification of Joints

Joints can be classified based on their structure and function:

Structural Classification

1. Fibrous Joints: Held together by dense connective tissue (e.g., sutures in the skull).
2. Cartilaginous Joints: Connected by cartilage (e.g., intervertebral discs, symphysis pubis).
3. Synovial Joints: Characterized by a fluid-filled space between bones (e.g., hinge joints like the elbow, ball-and-socket joints like the shoulder).

Functional Classification

1. Synarthroses: Immovable joints (e.g., sutures in the skull).
2. Amphiarthroses: Slightly movable joints