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

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

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

Nervous System Actions: Reflexes and Voluntary Acts

Reflex acts are fast and automatic, and do not involve conscious brain processing. These acts occur when a quick response is needed.

Neurons Involved in Reflexes

• Sensory neurons: Come from the skin and their axons enter the spinal posterior roots.
• Interneurons: Synapse with sensory neurons and transmit nerve impulses to other neurons.
• Motor neurons: They leave the spinal cord by the anterior roots and reach muscles, causing contraction and reflex.

Voluntary acts are varied, changing, and more elaborate than reflexes, involving the cerebral cortex.

Autonomic Nervous System

Also called the involuntary nervous system, it is responsible for the proper regulation and coordination of internal organs.

Types

Carnitine: An Essential Nutrient

Carnitine is a nutrient synthesized in the liver, kidneys, and brain from two essential amino acids: lysine and methionine. Carnitine is responsible for transporting fatty acids into the mitochondria, cellular organelles responsible for energy production.

Some individuals need carnitine supplements to maintain normal metabolism, which indicates that carnitine should be considered an essential nutrient.

Carnitine Deficiency

Carnitine deficiency is classified into two major groups: systemic deficiency (rare) and myopathic (more common). The systemic form affects the whole body, while the myopathic form affects only muscle tissue.

Causes of Carnitine Deficiency

Known causes of carnitine deficiency include:

• Deficiency

Population, Community, and Ecosystem

A population is a group of individuals of the same species living in a specific area. A community is a set of populations inhabiting the same area. The biotope is the physical environment occupied by a community, characterized by specific environmental conditions. An ecosystem encompasses both the community (biocenosis) and the biotope, including the interactions of organisms with each other and their environment.

Habitat and Optimal Conditions

A habitat is the specific environment where an organism finds the necessary conditions for life. Optimal conditions, regarding a given environmental factor, are the values at which a species thrives, reproduces effectively, and experiences high offspring survival.... Continue reading "Understanding Ecosystems: Species, Niches, and Interactions" »

In the early 1990s, research on the human being began with the Human Genome Project. In April 2003, the entire nucleotide sequence of the human genome was completed. Today, we know that:

• Our haploid genome (all 23 different chromosomes that we possess) contains 3,000 million pairs of nitrogenous bases, which equates to about 30,000 genes.
• 99.9% of these genes are the same in all people: the differences between us do not represent more than 0.1% of the genome.
• 90% of the genome has no known coding function, which does not mean it has no function, such as gene regulation or various biological controls. It is thought that some of this DNA may correspond to genetic remains of our ancestors.

Applications of the Human Genome Project

The practical applications... Continue reading "Decoding the Human Genome: Applications and Biotechnology" »

Biotic Relationships

Biotic relationships are the interactions among living organisms in an environment. There are two main types of biotic relationships:

Interspecific Relationships

Interspecific relationships occur between organisms of different species. These include:

• Mutualism: A relationship where both species benefit. Example: Bees pollinating flowers.
• Commensalism: A relationship where one species benefits, and the other is unaffected. Example: Beetles feeding on mammal excrement.
• Inquilinism: A specific type of commensalism where one organism uses another for housing.
• Parasitism: A relationship where one species (the parasite) benefits at the expense of the other (the host). Example: Cochineals feeding on cacti.
• Predation: A relationship where

Non-Infectious Diseases

In addition to diseases caused by microorganisms, other diseases are caused by different reasons:

a) Diseases Affecting the Functioning of the Equipment

These include circulatory diseases, which affect the respiratory tract (such as asthma or bronchitis), and those that affect bones or joints (osteoarthritis and osteoporosis).

b) Cancer

This occurs when certain cells, for reasons not yet fully clarified, undergo a metamorphosis that makes them divide rapidly and uncontrollably. As a result, it creates a mass of abnormal cells, called a tumor, which causes the destruction of nearby tissue.

c) Deficiency Diseases

These are caused by a poor diet lacking in certain nutrients. Examples include vitamin deficiency or anemia.

d) Traumatic