Science unit

Circulatory System- The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide.

Cardiac Output Calculations- Cardiac output is how many liters of blood your heart pumps in one minute.multiply stroke volume by heart rate.

Anatomy of the heart: two upper chambers left atrium and right atrium and two lower chambers called the left and right ventricles.The right atrium receives non-oxygenated blood from the body's largest veins — superior vena cava and inferior vena cava — and pumps it through the tricuspid valve to the right ventricle.

• The right ventricle pumps the blood through the pulmonary valve to the lungs, where it becomes oxygenated.

• The left atrium receives oxygenated blood from the lungs and pumps it through the mitral valve to the left ventricle.

• The left ventricle pumps oxygen-rich blood through the aortic valve to the aorta and the rest of the body.

The coronary arteries run along the surface of the heart and provide oxygen-rich blood to the heart muscle.
The superior vena cava and inferior vena cava are very large veins that bring deoxygenated blood to your heart to get oxygen. Your inferior vena cava, your body’s largest vein, carries oxygen-depleted blood back to your heart from the lower part of your body . Your superior vena cava, your second biggest vein, brings oxygen-poor blood from your upper body to your heart.Your superior vena cava and inferior vena cava have the important function of carrying oxygen-poor blood to your heart’s right atrium, where it moves into your right ventricle and then to your lungs (through your pulmonary artery) to trade in carbon dioxide for oxygen. Oxygenated blood comes back through your pulmonary veins to your heart’s left atrium. From there, blood that now carries fresh oxygen goes to your left ventricle and to your aorta for distribution to your body.
Your pulmonary veins are located between your lungs and your heart. Many smaller blood vessels converge in each of your lungs (right and left) to form a pair of pulmonary veins.From there, your pulmonary veins travel to your heart and connect with your left atrium. This is the top left chamber of your heart.The lung veins sometimes referred to as the pulmonary veins, are blood vessels that transfer freshly oxygenated blood from the lungs to the left atria of the heart.\

The aorta is the largest blood vessel in the body. This artery is responsible for transporting oxygen rich blood from your heart to the rest of your body. The aorta begins at the left ventricle of the heart, extending upward into the chest to form an arch. I

Blood flow through the heart veins, arteries and capilaries:
Arteries carry oxygen-rich blood away from the heart (

• Thick, muscular walls to withstand high pressure from the heart’s pumping action.

  • Elastic fibers that allow the arteries to stretch as blood is pumped through.

  • Small diameter (but larger than veins).

  • No valves (because the pressure from the heart keeps the blood moving forward).

  • Arteries are usually deeper within the body (e.g., the aorta and the pulmonary artery).

• Examples:

  • Aorta (largest artery), coronary arteries, carotid artery

Veins carry oxygen-poor blood back to the heart

• Thinner walls than arteries because the blood pressure in veins is much lower.

  • Valves to prevent blood from flowing backward due to low pressure and gravity (important in legs and arms).

• Examples:

  • Superior vena cava, inferior vena cava

    Capillaries : are the smallest blood vessels, where the exchange of oxygen, carbon dioxide, nutrients, and waste products occurs between the blood and tissues.

    • Very thin walls (just one cell thick) to allow easy exchange of gases and nutrients.

    • Extremely small diameter, allowing red blood cells to pass through in a single file.

    • No valves.

  • Location:

    • Found throughout the body, in tissues and organs, connecting arteries and veins.

  • Examples:

    • Capillary beds surrounding organs like muscles, lungs, and the intestines.

Blood pressure:Systolic top and diastolic bottom

Factors affecting heart rate

Age, health conditions, fitness conditions,and physical activities.

Varicose veins – how are they formed?

• Veins carry blood back to the heart, and they have one-way valves that help ensure blood flows upward, especially from the legs, against gravity.

  • Over time, the valves in the veins can become weakened or damaged, either due to aging, increased pressure, or other factors. This causes the valves to fail at their job of keeping blood from flowing backward.

  When the valves no longer close properly, blood can flow backward

  • The backflow of blood causes blood to pool in the veins, and because the veins are unable to handle the increased volume, they expand and bulge.

  • As the blood builds up, the veins enlarge, become twisted, and lose their elasticity, which causes them to appear swollen, twisted, and often discolored (usually blue or purple).

Components of blood: White blood cells, red blood cells and platelets

 What percentage each make up in the blood, White blood cells one percent, red blood cells 84%, and platletes one percentt.

Red blood cells: Red Blood Cells

This shape is like a donut with a flat center, which increases the surface area for gas exchange and allows the cells to flex as they move through the blood vessels.

• Function:

  • Transport oxygen: Red blood cells carry oxygen from the lungs to the body’s tissues and organs.

  • Transport carbon dioxide: They also help carry carbon dioxide from the tissues back to the lungs for exhalation.

  • The flexibility helps them pass through narrow capillaries.

Platelets:

• Platelets are small, irregularly shaped fragments of cells with no nucleus. They have a (disc-like) shape in circulation.

• Function:

  • Blood clotting: Platelets help with the process that stops bleeding by forming clots at the site of injury.

  • When blood vessels are damaged, platelets adhere to the area, clump together, and release chemicals that help form a clot to seal the wound.

• Why the shape matters:

  • The irregular shape helps platelets adhere to the site of injury and form an effective blood clot.

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The clotting process:

The blood clotting process involves several steps that work together to prevent excessive bleeding after a blood vessel is injured. The process creates a scab over the wound and involves key components like fibrin and platelets to form a protective barrier.

Cardiovascular Diseases and disorders : Atherosclerosis, coronary heart disease, heart attack, stroke, aneurysm, septal heart defect

What is angina?
Angina is chest pain or discomfort when your heart doesn’t receive enough oxygen-rich blood. As a result, your heart may beat faster and harder to gain more blood, causing you noticeable pain. Angina isn’t a disease. It’s a symptom and a warning sign of heart disease.

How plaque builds up in the heart and vessels

Plaque buildup in the heart and blood vessels is a gradual process known as atherosclerosis. It occurs when fats, cholesterol, and other substances accumulate in the walls of arteries, leading to narrowed and hardened arteries.Low-density lipoprotein (LDL cholesterol, the "bad" cholesterol) seeps into the damaged artery walls.igh LDL ("bad") cholesterol and low HDL ("good") cholesterol

• White blood cells rush to consume the LDL, forming foam cells that create fatty streaks.s plaque grows, it narrows the artery, reducing oxygen-rich blood flow to vital organs.

 How does your body fight invaders?

First Line of Defense: Physical and Chemical Barriers

Before the immune system even needs to respond to an invader, the body has physical and chemical defences:

• Skin,Mucous Membranes, Stomach Acid, (White Blood Cells): These are the first responders to an infection.

• Macrophages and neutrophils are types identify pathogens, and engulf (consume) them. Antigens: When a pathogen enters the body, it has molecules on its surface called antigens. These act as "identifiers" that the immune system uses to recognize and target the pathogen.

  • Helper T Cells: These cells are like commanders that help coordinate the immune response. They activate B cells to produce antibodies and stimulate killer T cells to attack infected cells.

    • Cytotoxic T Cells (Killer T Cells): These cells directly attack and kill infected cells or cancerous cells by releasing enzymes that cause the infected cells to self-destruct.

  • B Cells (B Lymphocytes): These cells produce antibodies (also called immunoglobulins). Antibodies are proteins that specifically recognize and bind to antigens on the surface of pathogens, marking them for destruction.

    • After exposure to a pathogen, B cells become memory B cells, which "remember" the pathogen and allow the body to respond more quickly and effectively if the pathogen is encountered again in the future.

  • Antibodies: These proteins are designed to bind to the antigen of a pathogen. This binding marks the pathogen for destruction by other immune cells (like macrophages) or neutralizes its ability to cause harm (such as preventing a virus from entering a cell).

    The immune system has a memory that allows it to respond more efficiently if the body is exposed to the same pathogen again. This is the basis for immunity and why vaccines are effective:

    • Memory B Cells: After an infection, some B cells become long-lived memory B cells. If the body encounters the same pathogen again, these cells can rapidly produce the appropriate antibodies to fight off the infection.

    • Memory T Cells: Similarly, memory T cells "remember" pathogens and can quickly recognize and destroy infected cells if

      they encounter the same pathogen in the future.

      physical Barriers: The skin, mucous membranes, and other physical barriers keep most pathogens out.

    • Innate Immunity: If pathogens bypass the physical barriers, the innate immune system responds with nonspecific defenses like inflammation, fever, and phagocytes (white blood cells).

    • Adaptive Immunity: If the innate immune system isn't enough, the adaptive immune system targets specific pathogens using T cells, B cells, antibodies, and memory cells.

    • Memory: The immune system "remembers" pathogens it has encountered, so if the body is exposed to the same pathogen again, it can respond much faster and more effectively.

 How is disease spread?When we talk about disease spreading in the immune system, we're referring to how pathogens (such as bacteria, viruses, fungi, or parasites) invade the body and how the immune system responds to these infections.Through cuts or wounds: Pathogens can enter through breaks in the skin.Once pathogens invade and are not immediately destroyed, they can spread to other areas of the body:

• Bloodstream: If a pathogen manages to enter the blood, it can spread throughout the body, potentially infecting distant organs and tissues. This is why infections like sepsis can be life-threatening.

• Lymphatic System: The lymphatic system, which includes lymph nodes and lymph fluid, is also a pathway that pathogens can use to travel throughout the body. This system helps filter pathogens and is closely tied to the immune response.

• Tissues and Organs: Pathogens can spread through tissues, infecting different organs, depending on the type of infection. For example, tuberculosis spreads to the lungs, while hepatitis spreads to the liver.

• Inhalation: If airborne pathogens are breathed in, they enter the respiratory system.

• Ingestion: Eating contaminated food or water can introduce pathogens into the digestive system.

• Sexual contact or blood transfusions: Some diseases, such as HIV, spread through bodily fluids.

 Protists: Protists are single-celled organisms . Some protists are parasites, meaning they live and reproduce inside a host, making them difficult for the immune system to eliminate.

How Protists Spread in the Body

• Protists can enter the body through contaminated water or food, mosquito bites or direct contact with infected feces.

• Once inside, they invade cells or tissues, using the body's nutrients to grow and multiply.

• Some, like Plasmodium, hide inside red blood cells, making it harder for the immune system to detect them.

How the Immune System Responds

• Macrophages and Neutrophils try to engulf and destroy protists.

• Inflammatory responses help slow down the infection.

• T cells and B cells create a specific response by producing antibodies to target the protist.

• Some protists, like Plasmodium, constantly change their surface proteins to evade immune detection, making them difficult to eliminate.

fungi: Fungi are multicellular or single-celled organisms that can cause infections like athlete’s foot, yeast infections (Candida), and lung infections (Aspergillosis). Most fungi do not harm healthy people, but they can cause severe infections in people with weakened immune systems.

How Fungi Spread in the Body

• Skin contact: Fungal infections like athlete’s foot spread through contact with contaminated surfaces.

• Inhalation: leading to respiratory infections.

• Overgrowth of normal fungi: Some fungi, like Candida, are normally present in the body but can grow uncontrollably if the immune system is weak.

How the Immune System Responds

• Skin Barrier: The first defense is intact skin, which prevents fungal entry.

• Macrophages and Neutrophils: These immune cells engulf and digest fungal spores.

• T Cells and Cytokines: Helper T cells release cytokines to activate other immune cells against the fungi.

• Some fungi create protective biofilms or change their shape to evade immune attacks, making them difficult to remove completely.

viruses; Viruses are non-living infectious agents that invade host cells, hijack their machinery, and force them to create more viruses.

How Viruses Spread in the Body

• Through the air

• By direct contact (HIV).

• Through insect bites (Zika virus).

• By contaminated surfaces (cold viruses).

How the Immune System Responds

• Natural Killer (NK) Cells: These cells destroy virus-infected cells before the virus can spread.

• T Cells:

  • Helper T Cells activate other immune responses.

  • Cytotoxic (Killer) T Cells attack and destroy infected cells.

• B Cells and Antibodies: Antibodies bind to viruses and prevent them from infecting more cells.

• Some viruses, like HIV, attack and weaken the immune system by directly targeting T cells, making the body vulnerable to other infections.

 Immune Response:

Pathogen Entry & Detection (Innate Immunity)

• When a pathogen (bacteria, virus, or other foreign substance) enters the body, the immune system detects antigens.

• Antigens: Proteins or molecules on the surface of pathogens that trigger an immune response.

• Macrophages: Large white blood cells that act as the body's first line of defense.

• They engulf and digest pathogens through a process called phagocytosis.

• After digesting the pathogen, macrophages present fragments of the antigens on their surface to alert other immune cells.

• Helper T Cells (CD4+ T Cells): Recognize antigens displayed by macrophages.

• They release chemical signals (cytokines) that activate other immune cells, including B cells and Killer T cells.

• B Cells (a type of white blood cell) are activated by Helper T Cells.

• Once activated, B Cells differentiate into Plasma Cells, which produce antibodies.

• Antibodies: Y-shaped proteins that specifically bind to antigens, marking pathogens for destruction or neutralizing them.

• Killer T Cells (Cytotoxic T Cells, CD8+ T Cells): Attack and destroy infected cells.

• They release toxic proteins (e.g., perforin and granzymes) that puncture infected cells, leading to cell death (apoptosis).

  After the infection is cleared, some B and T cells become memory cells:

  • Memory B Cells: Remember the pathogen and rapidly produce antibodies if reinfected.

  • Memory T Cells: Quickly activate a T Cell response upon future exposure.

  • Suppressor (Regulatory) T Cells: Prevent the immune system from overreacting.

  • They help turn off the immune response after the infection is cleared to prevent autoimmune diseases.

 Autoimmune disease: An autoimmune disease occurs when the immune system mistakenly attacks the body's own healthy cells and tissues. Normally, the immune system defends against harmful invaders like bacteria, viruses, and other pathogens. However, in autoimmune diseases, the immune system cannot distinguish between "self" and "non-self,"

Causes of Autoimmune Diseases

The exact causes are not fully understood, but several factors may contribute:

1. Genetics – Some autoimmune diseases run in families.

2. Infections – Some viral or bacterial infections may trigger an autoimmune response.

3. Environmental Factors – Exposure to toxins, pollution, or certain medications can play a role.

4. Hormonal Changes – Some autoimmune diseases are more common in women, suggesting a link to hormones.

o Chromosomes-Where are they located?Chromosomes are thread-like structures made of DNA and proteins that carry genetic information.Chromosomes are found inside the nucleus of the cell. Humans have 46 chromosomes (23 pairs) in most body cells.

Karyotyping- A laboratory technique used to examine an individual's chromosomes to detect genetic abnormalities. It involves arranging and analyzing chromosomes based on their size, shape, and number.Chromosomes are arranged in pairs (from largest to smallest) to form a karyotype chart. Scientists check for extra, missing, or abnormal chromosomes.

What do genetic disorders look like?These disorders involve missing, extra, or altered chromosomes:

How do you tell if something is male or female? Due to their sex chromosmes. XX is female. XY is male.X Chromosome: Larger, carries many genes important for development.

 What does Down syndrome look like?a genetic disorder caused by an extra copy of chromosome 21. Total of 47 chromosomes instead of 46

 Mitosis; is a type of cell division that produces two identical daughter cells from a single parent cell. It is essential for growth, repair, and maintenance in multicellular organisms Produces two genetically identical cells. Each daughter cell has the same number of chromosomes as the parent (diploid, 2n) Occurs in somatic (body) cells, not in reproductive cells

Meiosis: a type of cell division that produces four genetically unique daughter cells, each with half the number of chromosomes as the parent cell. It is essential for sexual reproduction and occurs in reproductive cells (gametes: sperm and egg cells)
✔ Produces four genetically unique cells, Each daughter cell has half the number of chromosomes (haploid, n), Occurs in germ cells (sperm & egg)

 Fertilization: the process where a sperm cell (male gamete, haploid) and an egg cell (female gamete, haploid)combine to form a zygote (diploid), restoring the full number of chromosomes. Sperm Cell (n = 23 chromosomes) → Carries either an X or Y chromosome (determines biological sex). Egg Cell (n = 23 chromosomes) → Always carries an X chromosome. When they fuse, the zygote has 46 chromosomes (diploid, 2n).

 Selective breeding: Selective breeding is the process of choosing specific parents with desirable traits to produce offspring with those same traits. This method relies on chromosomes and genes that control inherited characteristics.

 Differences between cross pollination and self-pollination.

• Self-pollination, on the other hand, involves the fusion of gametes from the same plant, meaning the offspring inherit identical or very similar chromosomes.

• Over generations, this can lead to genetic uniformity, making plants more vulnerable to environmental changes or diseases.

• Because no new chromosome combinations are introduced, self-pollinated plants may show less variation in traits.

  Cross-pollination leads to greater genetic variation because chromosomes from two different parent plants combine.

• During fertilization, each parent contributes half of its chromosomes, resulting in offspring with a unique genetic makeup.

• This genetic diversity helps plants adapt to changing environments and develop resistance to diseases.

• Since different alleles (gene variations) mix, cross-pollination can produce plants with new and improved traits.

 Dominant gene: A dominant gene is a gene that expresses its trait even if only one copy is present. It overpowers the effect of a recessive gene when both are inherited.

Recessive Genes: A recessive gene is a gene that is only expressed when an individual inherits two copies of it (one from each parent). If a dominant gene is present, the recessive gene is hidden and does not show its effect. (Homozygous aa)

 Homozygous vs. Heterozygous: Referring to the alleles (gene variants) inherited for a particular trait.n individual is homozygous when they inherit two identical alleles for a particular gene (either both dominant or both recessive).

• • Homozygous Dominant (AA) – Two copies of the dominant allele (e.g., for brown eyes, if B = brown, AA would result in brown eyes).

  • Homozygous Recessive (aa) – Two copies of the recessive allele (e.g., for blue eyes, if b = blue, aa would result in blue eyes).

• An individual is heterozygous when they inherit two different alleles for a particular gene, one dominant and one recessive.

  • Heterozygous (Aa) – One dominant allele (A) and one recessive allele (a) (e.g., for brown eyes, where B = brown and b = blue, an individual with Bb would have brown eyes).

 Genotype vs. Phenotype

• Genotype: The genetic makeup of an organism, referring to the specific combination of alleles inherited from both parents.

  • Homozygous Dominant: AA

  • Heterozygous: Aa

  • Homozygous Recessive: aa\

    Phenotype: The physical appearance or traits of an organism that are expressed as a result of the interaction between its genotype and the environment.

 Sex linked traits- Femal- XX Male XY

 Structure of DNA: DNA is a double-stranded molecule that carries genetic information in all living organisms. It has a double helix shape, similar to a twisted ladder.

1. Double Helix Shape 🧬

   • DNA has two strands twisted around each other, forming a spiral staircase-like structure.

2. Nucleotides (Building Blocks of DNA)

   • Each strand of DNA is made up of nucleotides, which consist of:

     • Sugar (Deoxyribose) – Provides structure.

     • Phosphate Group – Connects nucleotides together.

     • Nitrogenous Base – Carries genetic information.

3. Nitrogenous Bases (A, T, C, G)

   • There are four nitrogenous bases that pair up:

     • Adenine (A) pairs with Thymine (T) → A-T

     • Cytosine (C) pairs with Guanine (G) → C-G

   • These base pairs are held together by hydrogen bonds.

4. Antiparallel Strands

   • The two strands of DNA run in opposite directions

 Cytosine, Guanine, Adenine and Thymine: These are the four nitrogenous bases that make up the DNA molecule. They pair together in specific ways to form the "rungs" of the DNA double helix.

Adenine (A)

• A purine base.

• Pairs with Thymine (T) through two hydrogen bonds.

• Represents genetic instructions in the DNA sequence.

1. Thymine (T)

   • A pyrimidine base.

   • Pairs with Adenine (A) through two hydrogen bonds.

   • Important in the process of replication and transcription.

2. Cytosine (C)

   • A pyrimidine base.

   • Pairs with Guanine (G) through three hydrogen bonds.

   • Plays a role in encoding genetic information and ensuring DNA stability.

3. Guanine (G)

   • A purine base.

   • Pairs with Cytosine (C) through three hydrogen bonds.

   • Crucial in the function and stability of the DNA strand.

Base Pairing in DNA:

• Adenine (A) pairs with Thymine (T) (A-T)

• Cytosine (C) pairs with Guanine (G) (C-G)

These specific pairings are critical because they ensure the accuracy of DNA replication and genetic information transmission.

 Protein SynthesisProtein synthesis is how our cells make proteins, which are necessary for everything in our body, like building muscles, repairing tissues, and carrying out important functions.

• Transcription: Copy the recipe (DNA) onto a piece of paper (mRNA).

• Translation: Use the recipe (mRNA) to cook the dish (protein) in the kitchen (ribosome).

 Cystic Fibrosis: Cystic fibrosis is a genetic disorder that affects the lungs, digestive system, and other organs. It is caused by a problem with a gene called the CFTR gene.

• Cystic fibrosis occurs when a person inherits two faulty copies of the CFTR gene – one from each parent.

• This gene normally helps control the movement of salt and water in and out of cells. When it's faulty, it leads to thick, sticky mucus in the body.

 Point Mutations: A point mutation is a type of genetic mutation that affects a single nucleotide in the DNA sequence. This is a change in just one "letter" of the DNA code (A, T, C, or G).One nucleotide is replaced by another.

• Example: If the original sequence is "ATG", a substitution could change it to

• "AAG"Silent Mutation: The substitution does not change the amino acid (protein) because of the redundancy in the genetic code. For example, both GAA and GAG code for the amino acid glutamic acid.

• Missense Mutation: The substitution causes a change in the amino acid, which could affect the protein’s function.

 Tracing genetic diseasePedigree charts show the affected individuals in different generations and help in determining if a disease is inherited in a dominant or recessive pattern.

• Example: If a child has a genetic disorder and both parents are unaffected, a carrier status for a recessive genetic disorder may be suspected.

• Genetic Testing:

  • Genetic testing involves analyzing an individual’s DNA to detect mutations or genetic changes that are linked to specific diseases. This can be done through:

Gene Therapy and Technologies for “curing” genetic disorders Gene therapy is a technique aimed at treating or curing genetic disorders by altering or repairing the faulty genes that cause the condition. This can involve replacing a missing or malfunctioning gene, adding a new gene to help treat a disease, or editing existing genes.