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

Nervous Coordination and the Neuron System

Nervous coordination is carried out by the nervous system. This system is made up of nerve tissue whose cells, called neurons, are capable of transmitting information through nerve impulses.

Structure and Function of Neurons

Neurons are typically divided into three main parts:

• Cell Body (Soma): Contains the nucleus and other essential organelles.
• Dendrites: Short, branch-like projections that receive signals.
• Axon: A longer projection that transmits signals away from the cell body. It ends in a series of slender branches that widen slightly at the tip, called axon terminals.

In general, axons are protected by a white substance called myelin. The axons of various neurons sometimes group together to form nerve

3.3 The Nervous System

Receives information from the receptors, processes and coordinates it, and generates orders for the effectors. It is made up of the central nervous system or CNS, and the peripheral nervous system or PNS.

3.4 The Central Nervous System or CNS

Coordinates all the body's functions. It is formed by the encephalon and the spinal cord.

The Encephalon

Protected by the skull or cranium and by three membranes, the meninges, between which a liquid called the cerebrospinal fluid circulates. This liquid protects the encephalon from knocks and blows. Divided into three parts:

• The brain is divided into two hemispheres, which are separated by a fissure. Its surface, the cerebral cortex, is full of folds and furrows, known as circumvolutions.

Regulation of Enzyme Activity

Enzymes are the workhorses of cells, catalyzing the thousands of biochemical reactions that keep cells alive and functioning. The activity of enzymes is carefully controlled to ensure that the proper amount of product is produced at the right time.

Why Regulate Enzyme Activity?

There are several reasons why cells need to regulate enzyme activity. First, the concentration of substrates and products can vary widely within the cell. If enzyme activity were constant, the rate of the reaction would also vary wildly, depending on the availability of substrates. Regulation allows the cell to adjust the rate of the reaction to match the needs of the cell.

Second, the cell needs to coordinate the activities of different enzymes... Continue reading "Enzyme Regulation: Mechanisms and Examples" »

Chapter 5: Life Processes

Introduction

Life processes are the basic functions performed by living organisms for survival and body maintenance. These include nutrition, respiration, transportation, and excretion.

Nutrition

There are two modes of nutrition: autotrophic and heterotrophic.

Autotrophic Nutrition (Photosynthesis)

Photosynthesis is the process by which green plants synthesize their own food using carbon dioxide (CO₂) and water (H₂O) in the presence of chlorophyll and sunlight.

Raw Materials for Photosynthesis: Carbon dioxide and water.

Site of Photosynthesis: Chloroplasts in the leaves. Chloroplasts contain a green pigment called chlorophyll.

Main Events of Photosynthesis:

• Absorption of light energy by chlorophyll.
• Conversion of light energy

Valve Disorders

Valve disorders can be caused by congenital deformities or acquired diseases. Stenosis (narrowing) restricts blood flow. Structural malformations prevent the valve from closing properly, causing murmurs. These often present with other cardiac conditions/disorders. Athletes with electrical (arrhythmia) or structural changes (hypertrophy) may have limitations on their ability to play.

Mitral Valve Prolapse

Mitral valve prolapse prevents the valve from closing properly and is the most common valve disorder. Return to play (RTP) is often possible if there is no significant family history.

Systemic Hypertension

Systemic hypertension is common in athletes but is not the etiology of sudden cardiac death (SCD). The pathogenesis involves... Continue reading "Understanding Cardiovascular Conditions in Athletes" »

Human reproduction is sexual. Two individuals from different sexes are needed. Each produces a type of gamete (reproductive cell).

Embryo development: Zygote undergoes cell division until it becomes an embryo that continues development up to being a fetus.

Childbirth: Baby is born, alive and fully formed

Development: The baby grows until maturity is reached (adulthood)

Changes leading to sexual maturity

• Primary sex characteristics: The reproductive organs
• Puberty: Stage from the ages 10-16, when majority occurs
• Adolescence: From puberty to adulthood, physical maturity and physiological and social changes, sexual desire appears
• Sex

The Internal Environment and Nutrition

All cells need to live in an internal environment that provides them with all the food and nutrients they need and allows cells to release waste substances. It is formed of interstitial plasma, and the plasma has to be continually renewed thanks to the blood, which transports nutrients and removes waste products. The circulatory system connects the other three systems involved in nutrition.

Blood Composition

• Blood Plasma (55%): Made up of water with minerals (90%), nutrients (glucose, amino acids, vitamins, etc.), waste products (urea, uric acid, CO2), proteins, and dissolved hormones.
• Blood Cells (45%): Includes erythrocytes (98-99%), leukocytes (granulocytes and agranulocytes), and platelets (1-2%).

Blood

Female Reproductive System

Key Components and Functions

Uterus

The myometrium, the middle layer of the uterine wall, is responsible for the contractions during childbirth.

Vagina

The vagina is an elastic tube that facilitates penetration during sexual intercourse.

Vulva

The vulva, the external female genitalia, consists of the labia majora, labia minora, and the clitoris, which is responsible for sexual pleasure.

Bartholin's Glands

These glands produce lubricant to facilitate sexual intercourse.

The Ovarian Cycle

Each ovarian cycle lasts approximately 28 days and consists of three phases:

1. Follicular Phase (14 days): An egg cell matures.
2. Ovulation: The mature egg is released from the ovary into the fallopian tube.
3. Luteal Phase (14 days): The corpus luteum,

The Locomotor System

The locomotor system is made up of the skeletal system and the muscular system.

The Skeletal System

The skeletal system is formed by bones and joints.

Purpose of the Skeletal System

• To serve as an internal framework for our bodies.
• To protect organs and internal tissues.
• To provide anchorage support for muscles.
• To manufacture blood cells.
• To serve as a reserve store of calcium and phosphorus.

Bones

Bones are organs composed of compact bone tissue on the outside and spongy bone tissue at the core. To avoid friction, the ends of our bones are covered with cartilage. The holes in the spongy bone tissue are filled with bone marrow. There are two types: red bone marrow, in which blood cells are produced, and yellow bone marrow, which... Continue reading "Understanding the Human Locomotor System" »

Neurological and Mental Health Disorders

• Alzheimer's Disease

  Destruction of neurons in the cerebral cortex, leading to symptoms such as memory loss, disorientation, and behavioral changes.

• Parkinson's Disease

  Characterized by involuntary trembling (especially in the hands) and loss of muscle strength.

• Multiple Sclerosis (MS)

  An immune system-related disorder where the myelin sheaths and neurons destroy each other, affecting the entire body.

• Amyotrophic Lateral Sclerosis (ALS)

  A neuromuscular disorder involving the loss of function and death of motor neurons, resulting in slow paralysis and eventual death.

• Schizophrenia

  A lack of coordination between thoughts, feelings, and actions, often resulting in the person living an isolated life.

• Neurosis

  Chronic