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

Intramuscular Drug Administration and Receptor Binding

Explains what a circuit is: a drug that is administered intramuscularly until it reaches the receptor. It exits the bloodstream through the capillary endothelium, traveling through the interstitial fluid, and crosses the cell membrane of its target cells.

Morphine Effects in Elderly Patients

Explains why an old man, who is administered morphine in doses equal to a middle-aged person, may be at increased risk of sleepiness, even after the drug's effects should have worn off. The elderly, like children, have decreased hepatic activity, so the drug takes longer to metabolize and be disposed of by the body, which can cause drowsiness in the case of morphine.

Drug Molecule Characteristics for Barrier

Coordination Systems: Nervous and Hormonal

When a body is small (one cell or more), its component cells are capable of capturing different environmental stimuli and responding to them. When the body is complex and has organs and organ systems, they must act together to perform their roles effectively. The nervous and hormonal systems carry out the coordination function.

Nervous System

Structure of the Neuron: Neurons are highly specialized cells that make up the different tissues and organs of the nervous system. These cells have different morphologies but share common features:

• Soma: Contains the nucleus and cytoplasm with all organelles.
• Axon: A long, unbranched extension with a widened end called the synaptic button.
• Dendrites: Highly branched,

Cellular Response

Cellular response - Cell-mediated immunity is a form of adaptive immune response mediated by T lymphocytes. It acts as an attack mechanism against intracellular microorganisms, such as viruses and some bacteria, that can survive and proliferate inside phagocytes and other host cells. The defense against such infections depends on cellular immunity, which induces the destruction of the organism living in phagocytes or infected cells.

A phagocyte captures an element, becoming a macrophage. After several processes, helper T cells are created and activated, which perform cytotoxicity (lysis of target cells by cytotoxic T cells) and regulation of the immune response by T helper cells.

Primary and Secondary Immune Response

Primary and

Legislation on Stem Cells and Cloning

UN Declarations on Cloning

Resolution adopted on 23 March 2005, stating that practices contrary to human dignity, such as reproductive cloning of humans, must be avoided.

Solemnly declares the following:

• The Member States shall take all measures necessary to adequately protect human life in the application of life sciences.
• Member States shall prohibit all forms of human cloning inasmuch as they are incompatible with human dignity and protection.
• Member States shall take the necessary measures to prohibit the application of genetic engineering techniques that may be contrary to human dignity.

Stem Cell and Cloning Law in Spain

In Spain, the Biomedical Law passed in 2007 allows therapeutic cloning and the obtaining... Continue reading "Biotechnology Legislation and Genetic Material Basics" »

The Cerebral Cortex and Synaptic Transmission

The cerebral cortex is the highest level of the brain, responsible for controlling the activities of other neurons at lower levels. This demonstrates the hierarchical nature of our nervous system. For instance, while the medulla oblongata (often referred to as 'the bulb' in older texts) controls automatic breathing movements, it also sends signals to the cerebral cortex. This explains why, when we enter water, we can consciously hold our breath, as the cerebral cortex can override the medulla's automatic control.

Understanding the Synapse

A synapse is the specialized space between two neurons that a nerve impulse must traverse to pass from one to another. This crucial process is known as synaptic transmission.... Continue reading "Neural Control and Vision: Brain and Eye Functions" »

Early Earth: The Cradle of Life

The conditions on early Earth, the stage upon which life emerged, are quite well-defined:

• Intense Volcanism and Submarine Activity

  The planet's interior was extremely hot, leading to intense volcanism. As most continents had not yet formed, the majority of this volcanism was submarine.

• An Anoxic Atmosphere and Global Ocean

  The proto-atmosphere lacked oxygen, and consequently, there was no ozone layer to shield the planet's surface from lethal ultraviolet rays, which could destroy any nascent signs of life.

Theories on Life's Genesis

Current scientific thought on the origin of life includes several prominent hypotheses:

• The Metabolic Hypothesis

  This hypothesis suggests that small, simple molecules from the environment

Sensory Receptors

The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli.
• Photoreceptors: Light-sensitive.
• Thermoreceptors: Sensitive to temperature variations.
• Nociceptors: Sensitive to internal pressures.

Sensory Receptors:

• Internal receptors: Report the condition of the body, e.g., hunger, thirst, need to urinate.
• External receptors: Collect stimuli from outside, e.g., light, sound, temperature.

The Senses of Touch, Smell, and Taste

Touch

• Epidermis: Epithelial tissue formed by several layers of cells. These cells contain keratin, a protein whose function is to waterproof the skin.
• Dermis: Formed by connective tissue, which provides elasticity to the skin. The dermis contains many blood

Human Heart: Structure and Function

The heart is a vital muscular organ responsible for pumping blood throughout the body. Its walls are primarily composed of a specialized muscle tissue called the myocardium.

Heart Anatomy: Key Components

The heart is divided into four main chambers:

• Two Atria: These are the upper chambers. They have thin, elastic walls and receive blood returning to the heart via veins.
• Two Ventricles: These are the lower chambers. They possess thick, powerful walls, especially the left ventricle, which pumps blood to the entire body. Arteries exit from the ventricles.

The left ventricle is connected to the left atrium, while the right side is separated by a partition (septum). Blood enters the atria from veins and leaves the ventricles... Continue reading "Human Heart: Structure, Circulation, and Health" »

Habitat and Ecological Niche Defined

A habitat is the physical place where a species lives. It provides the natural conditions the species needs to survive. An ecological niche is the way a species relates to the biotic and abiotic factors in an ecosystem.

Two species can share the same habitat, although they do not usually occupy the same ecological niche.

Understanding Trophic Dynamics

Trophic dynamics is the system that describes the position of a living being in a food chain. The system uses trophic levels to explain what an organism eats or is eaten by.

Trophic Pyramids: Graphic Representations

A trophic pyramid is a graphic representation of a particular characteristic at each trophic level. These pyramids are specific to individual ecosystems.... Continue reading "Ecosystem Dynamics: Trophic Levels, Pyramids, and Energy Flow" »