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

Understanding Heart Failure

Heart Failure (HF) is the inability of the heart to maintain adequate cardiac output to meet the patient's physiological needs.

Factors Influencing Cardiac Output

The primary factors influencing cardiac output are:

1. Distensibility: This is influenced by preload. An excessive increase in preload may be caused by conditions such as anemia, hyperthyroidism, or atrioventricular fistula.
2. Contractility: Often affected by conditions like myocardial infarction.
3. Afterload: Determined by the pressure in the aortic root.

Heart Failure Syndrome

The syndrome of heart failure is characterized by:

• Decreased Cardiac Output: Leading to lower blood pressure.
• Increased Secretion of Catecholamines: Which causes vasoconstriction, piloerection,

The Digestive System

Humans need to consume a range of foods from which they obtain the necessary materials and energy for their bodily functions. The body requires proteins, lipids, carbohydrates, vitamins, and minerals.

Understanding Nutrition

Nutrition is the biological function through which living organisms acquire and transform matter and energy from their environment. We can distinguish three main phases in nutrition:

• Ingestion
• Digestion
• Absorption

The digestive system is responsible for transforming food. This process occurs through various parts of the body:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Anus

Common Dental Diseases

• Gingivitis
• Periodontitis (Pyorrhea)
• Plaque
• Cavities

Diseases of the Digestive System

• Constipation and Diarrhea
• Peptic

Key Definitions in Health and Disease

Agent: An animate or inanimate entity whose presence or absence can disrupt host health.

Host: Any organism capable of harboring an agent.

Environment: The complex of factors influencing a system, determining its course and way of life.

Stimulus Trigger: A factor or condition arising after a disturbance in the ecological triad's balance, initiating the disease process.

Sign: A measurable or quantifiable manifestation in an individual.

Symptom: A subjective expression of a condition reported by an individual.

Latency: A stable phase in disease evolution without subclinical manifestations, signs, or symptoms.

Causality: Conditions involving agent, host, environment, and transmissibility factors that generate a stimulus... Continue reading "Understanding Health: Agents, Hosts, and Environmental Factors" »

The Human Ear: Structure and Function

The ear can be divided into three main sections: the outer ear, middle ear, and inner ear.

Outer Ear

• Auricle (Pinna)

  Consists of cartilage covered with skin. Its primary function is to collect sound waves and direct them into the ear canal.

• Ear Canal

  Extends from the auricle to the eardrum. It contains hairs to help keep out foreign bodies like insects and glands that secrete cerumen (earwax) to protect against water and debris.

Middle Ear

• Tympanic Membrane (Eardrum)

  A thin membrane that vibrates in response to sound waves.

• Ossicular Chain

  Consists of three tiny bones: the malleus (hammer), incus (anvil), and stapes (stirrup). These bones transmit and amplify vibrations from the eardrum to the inner ear.

Inner Ear

• Cochlea

Invertebrate Excretory Systems (Protonephridia): These are found in animals with no coelom, such as flatworms. They consist of highly branched tubes that end in a few cells with cilia (flame cells) or flagella (solenocytes). Both cilia and flagella are located in the lumen of the tube, and their movement causes the continuous elimination of waste substances. (Metanephridia): This system occurs in coelomates (annelids, mollusks, etc.). It is made up of a coiled tube surrounded by a capillary network, with two openings: the external (nephridiopore) and internal (nephrostome), which opens into the coelomic cavity. Inside the metanephridia, reabsorption occurs for compounds that are still useful, while waste substances are expelled outside through... Continue reading "Understanding Invertebrate and Vertebrate Excretory Systems" »

Connective Tissue Functions and Components

Connective tissues provide a frame to attach the other tissues of the body, such as body structures, and to protect the internal organs. The intercellular substance of these tissues is very important and is reinforced by a matrix of fibers dispersed and interwoven, and a transparent amorphous extracellular matrix.

Specialized Cell Types

• Fibroblasts: Fixed cells, which are variable.
• Adipocytes; Monocytes: Accumulate fat; WBC migrants. When inflammation occurs, they turn into macrophages that engulf microbes.
• Lymphocytes: Produce antibodies.
• Mast cells: They produce heparin (anticoagulant function) and histamine, which increases the permeability of capillary walls.
• Chromatophores: Stem cells that are very bulky.

Neodarwinism

This theory, born in 1947, defines evolution based on six core principles:

1. Refusal of Lamarckism

   It does not accept the theory of acquired characteristics.

2. Variability: Mutation and Recombination

   Individuals with asexual reproduction have mutation as the only source of variability. Individuals in sexual reproduction involve the process of genetic recombination.

3. Natural Selection Acts on Genetic Variability

   The individual is the bearer of different alleles, and natural selection acts on these varieties.

4. Evolution Occurs in the Population, Not Individuals

   A population is defined as a group of individuals of the same species that share an area and can crossbreed to produce fertile offspring. Populations survive, change, and evolve, while individuals

Unit 10: The Basis of Heredity - Molecular Genetics

Basics of Genetics

• Gene: Each piece of DNA containing information for one character.
• Alleles: Each form a gene can have.
• Locus: The physical location a gene occupies on a chromosome.
• Loci: The place occupied by several genes.
• Diploid Organisms: Individuals who have two alleles for each gene, one from the mother and one from the father. This is represented as 2n.
• Haploid Organisms: Individuals that have only one gene for each character. This is represented by n.
• Gamete: A sexual reproductive cell, haploid (n), produced by meiosis.
• Genotype: The set of alleles of an individual for one or more characters.
• Phenotype: Each of the aspects or observable manifestations of a character.
• Phenotype = Genotype +

Lipids

Functions of Lipids

• Energy Storage: Lipids serve as the primary energy reserve in the body.
• Structural Components: Lipid bilayers form the plasma membrane and other cell organelles.
• Protection: Lipids cushion vital organs, like the kidneys, and protect body surfaces (e.g., waxes on hair and fruit).
• Biocatalysis: While not all lipids are biocatalysts themselves, some play a role in biocatalyst synthesis.
• Transport: Lipids are emulsified and transported from the intestine to either storage in adipose tissue or sites of utilization.

Amino Acids

Amino acids are small organic compounds characterized by a carboxyl group and an amino group. They are solid, crystalline, water-soluble, have high melting points, and exhibit optical activity. Primary amino... Continue reading "Lipids, Amino Acids, and Proteins: Structure, Function, and Properties" »