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

Cell Division Processes

Mitosis: Somatic Cell Replication

Mitosis is an equational division resulting in two identical daughter cells. This process covers the growth and repair throughout the life of organisms.

• Homologous chromosomes do not form pairs.
• Results in 2 identical daughter cells.
• Cells can undergo successive mitotic divisions.
• Occurs in somatic cells (all body cells, excluding germ cells).

Meiosis: Gamete and Spore Formation

Meiosis is the process of cell division that occurs in germ cells, resulting in genetically distinct reproductive cells (gametes or spores).

1. First Division: Reductional.
2. Second Division: Equational.

• Homologous chromosomes form pairs.
• Results in 4 daughter cells, genetically different from each other.
• Cells cannot undergo

Cellular Immunity

Cellular immunity involves two main types of lymphocytes: T lymphocytes and B lymphocytes. It also involves non-T, non-B cells. This system effectively destroys:

• Foreign cells
• Tumor cells
• Virus-infected cells
• Cells infected by intracellular pathogens

T Lymphocytes

T4 Lymphocytes

T_H Lymphocytes: These cells stimulate other T cells and B lymphocytes.

T_D Lymphocytes: These cells increase the number and activity of macrophages.

T8 Lymphocytes

T_C Lymphocytes: These cells destroy target cells.

T_S Lymphocytes: These cells regulate and suppress excessive or inappropriate immune responses. They deactivate lymphocytes once antigenic agents are controlled.

A phagocyte captures a foreign element, digests it, and presents it as an antigen-presenting... Continue reading "Understanding Cellular and Acquired Immunity: Types, Mechanisms, and Pathologies" »

Circulatory System Elements

The circulatory system includes:

• Veins, arteries, and capillaries: These vessels transport blood throughout the body.
• Heart: This organ pumps the blood.

Arteries vs. Veins

Arteries and veins differ in structure and function:

• Arteries: Have thick, elastic walls that stretch and spring back, propelling blood forward. They carry blood away from the heart.
• Veins: Have thinner walls that cannot stretch as much. They often have valves to prevent the backflow of blood, carrying blood to the heart.

Capillary Structure and Function

Capillaries form a network connecting arteries and veins throughout the body. Their walls are only one cell thick, facilitating the diffusion of nutrients and oxygen into tissues. This process occurs via... Continue reading "Circulatory and Excretory Systems: Structure and Function" »

Function of the Excretory System

The function of the excretory system is to remove the waste products that the body produces which are harmful to us.

Understanding Blood Pressure

Blood pressure is generated by the heart and is needed to keep the blood flowing. The value for a healthy person with normal pressure should be 120 over 80 mmHg (millimeters of mercury).

• The first number is the higher pressure caused as the left ventricle contracts to push blood out of the heart.
• The lower value is the pressure in the arteries during the time that the heart is filling with blood.

What is Hypertension?

Hypertension occurs when a resting person's blood pressure is higher than about 140/90 mmHg.

Causes and Risk Factors

It can be genetic, but you can also develop... Continue reading "Understanding Circulatory Health and Excretory Functions" »

Neck Anatomy

The head and neck join the upper chest. The neck comprises skin, fibrous muscles, major vascular elements, lymph nodes, organs (cervical larynx, cervical trachea), and glands (thyroid and parathyroid).

The skeletal neck includes the cervical spine.

• Platysma (2): Thin ring from the superclavicular zone to the face, deep chin.
• Sternocleidomastoid (2): Lateral neck, from the thorax to the temporal and occipital mastoid bones.
  • Origin: Lower insertion and command of the sternum and below the clavicle.
  • Lateral/External: External jugular vein, ending with the subclavian, used for serum.
  • Medial/Internal: Vasculo-nervous bundle, primitive carotid artery, internal jugular vein, neurogastric nerve.
  • Double Innervation: Branches of the nerve cord and

Fundamentals of Nutrition and Metabolism

Defining Key Biological Concepts

Nutrition: The set of processes by which living things incorporate foreign substances to obtain matter and energy.

Food (Alimentos): Substances consumed by living beings.

Feeding (Alimentación): The process of taking food. Food is composed of substances called nutrients.

Types of Nutrition

Nutrition is classified based on how organisms obtain organic matter:

• Autotrophs

  Capable of producing their own organic matter from simple inorganic substances. They require an energy source:

  • Photosynthetic: Obtain energy from sunlight (e.g., algae, plants, and photosynthetic bacteria).
  • Chemosynthetic: Use energy released by specific chemical reactions (e.g., determined bacteria).

• Heterotrophs

  Use

Acute Renal Failure (ARF)

Signs

ARF is often asymptomatic. However, some common signs include:

• Oliguria: Urine output of less than 400 ml per day
• Increased nitrogen products in the blood
• Electrolyte and acid-base abnormalities

Classification of Acute Renal Failure

1. Pre-renal ARF

This type accounts for 55% of cases. It is characterized by a deficiency in kidney perfusion, which decreases the glomerular filtration rate (GFR). There is no frank damage to the renal parenchyma initially.

Features of Pre-renal ARF:

• Often reversible
• No initial damage to the renal parenchyma
• Prolonged deficiency can lead to ischemia and acute tubular necrosis
• The renal tubules and loop of Henle are most affected by ischemia

Phases of Pre-renal ARF:

• Extension phase: Swelling occurs,

Mammals

• Females have breasts that produce milk to feed their young.
• The body is covered with hair.
• Body temperature is constant.
• Young are born alive.
• Examples: Prototherians (e.g., the platypus), marsupials (e.g., kangaroos), and eutherians (e.g., insectivores, bats, primates, cetaceans, carnivores, Perissodactyla, and Artiodactyla).
• Temperature: Mammals maintain a constant body temperature, typically between 38 and 40 degrees Celsius, regardless of whether they live in hot or cold climates.
• Reproduction: Mammals reproduce viviparously with internal fertilization. They lay eggs without nutrient reserves, which are implanted and developed in the womb. The placenta provides nourishment and oxygen to the developing fetus and facilitates the excretion

Cellular Respiration Explained

Respiration is the process in which glucose and oxygen are transformed inside the cell into water, carbon dioxide, and energy.

The goal is to transform glucose and oxygen into energy.

Gases involved are oxygen, which we use, and carbon dioxide, the result.

It happens inside the cell in the mitochondria.

Defining Metabolic Rate

Metabolic rate is an average of the amount of energy that a person needs. While sleeping, we spend energy in circulation, for development, breathing, and protection. We spend energy because the body is working constantly.

Function of the Breathing System

In breathing, gases are exchanged. Oxygen goes from the air to the blood, and carbon dioxide goes from the blood to the air.

Lining of the Respiratory

Neurons: The Basic Unit of the Nervous System

A neuron is the basic unit in the nervous system. It is a specialized conductor cell that receives and transmits electrochemical nerve impulses. A typical neuron has a cell body and long arms that conduct impulses from one body part to another.

Three Different Parts of the Neuron:

• The cell body
• Dendrites
• Axon

Types of Neurons

• Multipolar neurons have one axon and several dendrites. These are common in the brain and spinal cord.
• Bipolar neurons have one axon and one dendrite. These are seen in the retina of the eye, the inner ear, and the olfactory (smell) area.
• Unipolar neurons have one process extending from the cell body. The one process divides with one part acting as an axon and the other part functioning