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

Cerebral and Basilar Arteries

The carotid artery supplies 80% of the oxygen to the cerebral hemispheres. The two internal carotid arteries branch into the middle cerebral arteries, which provide 60% of the brain's oxygen supply. The anterior communicating artery connects the right and left middle cerebral arteries.

Two vertebral arteries (left and right) ascend along the spinal cord and merge at the base of the skull to form the basilar artery. This artery supplies the medulla, pons, and other brainstem structures.

Circle of Willis

1. Frontal lobes
2. Temporal lobes
3. Middle cerebral artery (right and left)
4. Anterior cerebral artery
5. Posterior cerebral artery
6. Basilar artery
7. Vertebral arteries (right and left)
8. Spinal cord
9. Internal carotid artery
10. Anterior communicating

Cytokinesis

Cytokinesis begins in anaphase and continues through telophase.

• In animals: The process involves strangling the cytoplasm. Segmentation is a linear division, resulting in the formation of a contractile ring formed by actin filaments.
• In plants: The cell wall prevents segmentation. This is done by forming a new wall inside the cell. This new wall is formed at the equator by the association of Golgi apparatus vesicles and microtubules, and it is called a phragmoplast. It extends laterally to reach the cell wall.

Types of Cell Division

1. Bipartition

   Division of the cell. Two daughter cells originate, equal in size. The process involves karyokinesis and cytokinesis, with its variant being strangulation.

2. Multiple Fission

   Divisions of the cell.

Understanding Key Health Concepts

1 - Life expectancy is the average number of years a person born in a particular country in a specific year is expected to live, assuming mortality rates remain constant.

2 - According to the WHO, health can be defined as: "A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity."

3 - CVD stands for cardiovascular diseases, which affect the heart or blood vessels.

4 - Myocardial infarction, a type of coronary heart disease (CHD), results in the death of myocardial tissue and permanent damage to the heart muscle. Angina pectoris occurs when a partial blockage reduces blood flow to an area of the heart, causing pain but not irreversible damage. Heart attacks... Continue reading "Understanding Key Health Concepts: A Concise Overview" »

Understanding Excretion

Excretion is the process of eliminating substances produced by our body that are toxic due to cellular activity.

The Urinary System Components

• Kidneys: The organs responsible for cleaning the blood of waste substances.
• Ureters: The ducts connecting the kidneys with the bladder.
• Urinary Bladder: A hollow organ that serves to accumulate urine. Its muscular walls dilate as it fills. At the bottom, a sphincter opens and closes voluntarily to release urine.
• Urethra: A tube that leads urine from the bladder to the outside during urination.

Anatomy of the Kidneys

The kidneys are dark red, bean-shaped organs measuring about 10 cm, located on both sides of the spinal column.

Internal Structure

• Cortex (Bark): The outermost layer, dark in

Viral Morphology

The morphology of the virion capsid is defined by its composition of multiple copies of a single protein or several different proteins, each encoded by a viral gene. A capsid, along with the nucleic acid it contains, is called a nucleocapsid. Virions exhibit two primary types of symmetry: helical and icosahedral.

Symmetry Types

Helical Symmetry

This is a helical protein structure with RNA or DNA protected inside it.

Icosahedral Symmetry

An icosahedral virus is a polyhedron composed of 20 identical, equilateral triangular faces.

In some viruses, the nucleocapsid is coated by an outer shell, or envelope, which is a fragment of the host cell's plasma membrane acquired as the virus emerges through a process called budding.

Complex Structures

Some... Continue reading "The Fundamentals of Virus Morphology and Replication" »

Characteristics of Living Things

0-Nutrition:

The ability of a living being to attract foreign material and use it to their advantage to grow in size and develop, or simply to maintain their structures and perform other vital functions.

0-Relationship:

Is the ability to attract external stimuli and to give adequate responses to them. Without this function, living beings could not perform other vital functions such as reproduction.

0-Reproduction:

The ability to originate new individuals, the same or very similar to the parents.

Field of Ecology

Ecology is interrelated with the 5 levels of organization of matter: organisms, populations, communities, ecosystems, or Biosphere.

Bodies (Organisms):

The unity of life, represented in each species, from the... Continue reading "Key Characteristics of Living Organisms and Ecology" »

Staphylococcus

• Easily develops antimicrobial resistance
• Gram-positive cocci
• Catalase-positive
• Facultative anaerobes
• Not demanding in their nutritional requirements
• Grow in normal media
• Some pathogenic species are generally opportunistic pathogens, commensals
• Important in animal and human infections

Natural Habitat

Widespread in nature; found on human and animal skin, surfaces of objects, air, soil, water, and milk.

S. aureus

Main pathogen associated with infections; colonizes nasal passages and pharynx.

S. epidermidis

Produces skin lesions, wound infections; microbiota found in the skin, respiratory tract, and gastrointestinal tract.

S. saprophyticus

Associated with urinary tract infections.

Immunogens

• Polysaccharide A (specific for S. aureus)
  • Antiphagocytic
  • Antiplatelet
  • Activator

Forensic Aspects of Asphyxia

Carotid Artery Occlusion

Loss of consciousness typically occurs within 10-15 seconds of complete occlusion of the carotid arteries. This timeframe allows for the implementation of restraint mechanisms.

Differential Diagnosis at the Scene

Differential diagnosis is crucial and is made at the scene, considering:

• The victim's clothing state.
• Presence of extracervical lesions indicative of control or struggle.
• Severity of neck injuries.

The diagnosis of accidental etiology is based on a meticulous examination of the scene. A high blood alcohol level may explain the victim's low resistance or the possibility of accidental strangulation.

Forensic Pathology of Submersion (Drowning)

Definition and Types of Submersion

Death or pathological... Continue reading "Forensic Pathology: Asphyxia and Drowning Investigations" »

Diabetes and Glucose Regulation

Diabetes is a disease in which the glucose level in the blood is altered. This level increases because the body does not metabolize glucose properly.

Insulin: This hormone controls glucose levels in the blood and is produced by the pancreas.

Types of Diabetes Mellitus

Type 1 Diabetes

• Characterized by the body producing little or no insulin.
• Onset typically occurs before age 40, often during childhood or adolescence.

Type 2 Diabetes

• Characterized by the body not producing enough insulin or not utilizing it well (insulin resistance).
• Onset typically occurs after age 40, and it is the most common type.
• Management involves diet, exercise, medication, and sometimes insulin injections.

Biotechnology and Recombinant Insulin

Recombinant

The Nervous System

Consisting of two types of cells:

• Neurons: consist of neuronal bodies, Dendrites (extensions where the nerve impulse enters the body), and axons.
• Glia (or Neuroglia): Made by the supporting structure of the nervous system, they collaborate in nutrition and feeding of neurons.

Nervous System Division

Central Nervous System (CNS), peripheral nervous system, autonomic (or vegetative) nervous system.

Central Nervous System

Comprising:

• Brain: Located in the skull, it consists of an internal gray substance and an external white substance. Surrounded by 3 membranes called meninges: Piamater, Arachnoid, Dura mater.

Parts:

• Cerebrum: Divided into hemispheres (left and right), weighing between 1200 and 1600g. It includes frontal, parietal, occipital,