Biology 20-1 Unit D-2 (Human Cardiovascular System)

Functions of the Circulatory Syste

1. Transport of Oxygen and Nutrients

   • Delivers O2 from lungs to blood

   • Nutrients from digestive system to cells throughout body

   • Removal of Waste Products and CO2 via lungs and kidneys

2. Regulation of Body Temperature and pH

   • Blood regulates body temperature by redistributing heat

   • maintains pH balance to ensure cellular function

     • Blood pH (CO2 transported in blood as a buffer system)

3. Defensive Mechanisms (Immune Response)

   • White blood cells fights infections and removing damaged cells (produce antibodies)

   • Immune system relies on the circulatory system to distribute antibodies

4. Clotting and Healing (Preventing / Stopping blood loss)

   • Platelets help in blood clotting to prevent excessive bleeding when injured

Heart (Components of the Circulatory System)

Pumps blood throughout the body, ensuring circulation of oxygen and nutrients.

• Enclosed in a fluid-filled membrane thats called the pericardium (Prevents friction (protection) between heart and surrounding tissues)

• Muscle tissue that make up the heart wall is called myocardium

• Myocardium is made of functional unit cells that are contractile called cardiomyocytes

  • Cardiac Muscles

    • Branched appearance

    • Striated

    • Have lots of mitochondria

      • Needs lots of ATP

Blood Vessels (Components of the Circulatory System)

Includes:

• Arteries and Veins

  • Largest

• Arterioles and Venules

  • Smaller

• Capillaries

  • Smallest

Blood (Components of the Circulatory System)

Function:

• Carries O2, nutrients, hormones, wastes, clotting factors (platelets), antibodies, and immune components

Types:

• Red Blood Cells (Erythrocytes): Carry O2 to all cells in body

• White Blood Cells (Leukocytes): Important to immune system

• Platelets (Thrombocytes): Make Blood clot to stop bleeding

“cyte“ suffix = cell

Structure of the Heart

4 Chambers:

• Right Atrium: Receives deoxygenated blood from body

• Right Ventricle: Pumps deoxygenated blood to lungs

• Left Atrium: Receives oxygenated blood from lungs

• Left Ventricle: Pumps oxygenated blood to body

Heart is divided into 2 parallel systems separated by the septum to ensure no mixing of O2 rich and O2 poor blood

Pulmonary Circulation

Carries deoxygenated blood to lungs and returns oxygenated blood to heart

Systemic Circulation

Distributes oxygenated blood to body and returns deoxygenated blood to the heart

Full Heart

Parts:

Involve Deoxygenated Blood IN ORDER:

• Superior Vena Cava

• Inferior Vena Cava

• Right Atrium

• Right Ventricle

• Pulmonary Artery

Involve Oxygenated Blood IN ORDER:

• Pulmonary Vein

• Left Atrium

• Left Ventricle

• Aortic Arch (Ascending Aorta)

• Descending Aorta

All Valves:

• Right Atrioventricular Valve (Tricuspid Valve)

• Left Atrioventricular Valve (Bicuspid Valve or Mitral Valve)

• Right Semilunar Valve (Pulmonary Valve)

• Left Semilunar Valve (Aortic Valve)

4 Main Blood Vessels (Aorta)

1. Aorta (CARRIES Oxygenated blood): Largest blood vessel in the body, exits the left ventricle and goes to the rest of the body as well as the heart

   • Ascending Aorta

     • Supplies O2 rich blood to head + upper body

   • Aortic Arch

     • Loops up and down behind the heart

   • Descending Aorta

     • Supplies O2 rich blood to lower body

   • Aorta branches off into various arteries including coronary arteries

4 Main Blood Vessels (Vena Cava)

1. Vena Cava (CARRIES Deoxygenated blood): Largest vein in the body, enters in the right atrium from the rest of the body

   • Superior Vena Cava:

     • Blood returned thru veins to heart (venous) from top half of the body (all above diaphragm)

   • Inferior Vena Cava:

     • Blood returned thru veins to heart (venous) from bottom half of the body (all below diaphragm)

4 Main Blood Vessels (Pulmonary Arteries)

1. Pulmonary Arteries (CARRIES Deoxygenated blood): 4 pulmonary arteries, 2 to each lung, exits the right ventricle and goes to the lungs

   • ONLY ARTERY that carries DEOXYGENATED blood

4 Main Blood Vessels (Pulmonary Veins)

1. Pulmonary Veins (CARRIES Oxygenated blood): 4 pulmonary veins, 2 to each lung, enters the left ventricle and comes from the lungs

   • ONLY VEIN that carries OXYGENATED blood

2 of 4 Valves of the Heart (Atrioventricular (AV) Valves)

1. Atrioventricular (AV) Valves: Prevents back flow of blood into right/left atrium from ventricle

• Right AV Valve: Tricuspid = Tri means 3 flaps opening/closing in the valve

• Left AV Valve: Bicuspid (AKA Mitral) = Bi means 2 flaps opening/closing in the valve

2 of 4 Valves of the Heart (Semilunar Valves)

1. Semilunar Valves: Prevents back flow of blood into right/left ventricles from pulmonary artery/aorta

• Pulmonary Valve: (Right Ventricle to Pulmonary Artery)

• Aortic Valve: (Left Ventricle to Aorta)

Path of Blood Through the Heart

1. O2 poor blood enters the right atrium from superior/inferior vena cava

2. Passes tricuspid valve into right ventricle

3. Right ventricle pumps O2 poor blood thru pulmonary valve into pulmonary arteries and to the lungs

4. O2 rich blood enters left atrium from lungs thru pulmonary veins

5. Passes bicuspid valve into left ventricle

6. Left ventricle pumps O2 rich blood thru aortic valve to the the aorta which supplies the rest of the body

Heart Sounds

“LUB-DUB” sounds created by the heart because of the closing of the valves in the heart

• “LUB”: Closing of AV valves during ventricular contractions (Systole)

• “DUB”: Closing of Semilunar valves during ventricular relaxation (Diastole)

Myogenic

Means the heart can contract without external nerve stimulation

• Generate their own electrochemical impulses

• Trigger muscle contractions

• different regions have different contraction rates with the atria contracting quicker then ventricles

Sinoatrial (SA) Node

"Pacemaker" of the heart

○ Located in the upper right atrium.

○ Sets the heart rate at about 70 beats per minute.

○ Initiates electrical impulses that spread through the atria, causing them to contract.

2. Atrioventricular (AV) Node

Conductor of impulses

○ Located in the right atrioventricular region.

○ Receives impulses from the SA node and relays them down the Purkinje fibers.

3. Purkinje Fibers

Distribute impulses to ventricles

○ Run along the septum and spread electrical impulses to the ventricular walls.

○ Ensure the ventricles contract from the bottom up, efficiently pumping blood.

The Cardiac Cycle

3 Step Process:

1. Atrial and Ventricular Diastole (chambers are relaxed and filling with blood)

2. Atrial Systole (atria contract and remaining blood is pushed into ventricles)

3. Ventricular Systole (ventricles contract and push blood out through aorta and pulmonary artery)

Autonomic Nervous System Control

• Sympathetic Nervous System: Increases heart rate (e.g. during stress).

• Parasympathetic Nervous System: Slows heart rate (e.g., during relaxation).

Electrocardiogram (ECG) or (EKG)

Is a diagnostic tool that records the electrical activity of the heart over time

P Wave (on ECG)

represents the atrial depolarization (charge reversal, triggers muscle contraction)

QRS Complex (on ECG)

represents the ventricle depolarization (signals sent from the SA node to AV node —> leads to purkinje, triggers muscle contraction)

T Wave (on ECG)

represents the ventricle repolarization (charge reversal, triggers muscle relaxation)

PR Interval (on ECG)

Time implulse takes to travel from the SA node to the ventricles

ST Segment (on ECG)

Represents time between ventricular contraction and relaxation

Uses of ECG’s

• Measure arrhythmias (irregular heart beats)

• Identify heart attacks

• Assesses electrical conduction problems

• Watch vitals after receiving medication or pacemakers

Pacemaker

Electrical device implanted into the chest to regulate heartbeats, prevents arrhythmias.

Blood vessels

are responsible for transporting blood throughout the body.

Three main types: arteries, veins, and capillaries.

● (Leaving the heart) Arteries branch into arterioles which branch off into capillaries

● Capillaries then branch off into venules which branch into larger veins (Returning to the heart)

Arteries and arterioles

Function: Carries O2 rich blood away from the heart

Structure: has a very thick-walled structure (3 layers)

● Pulse: Arteries expand and contract with each heartbeat, creating a detectable pulse.

● Arterioles: Smaller branches of arteries, regulate blood flow into capillaries through (constricting or dilating)

High pressure

Capillaries

Function: Site of fluid, gas, and nutrient exchange between blood and tissues (selectively permeable which is why proteins stay in blood)

Structure: Extremely thin walls with a small diameter (one-cell layer thick thats only one red blood cell thick) to allow diffusion (gas exchange - CO2, O2).

Capillary Beds

Beds: Networks of capillaries supplying oxygen and nutrients to tissues (capillary beds/networks surround tissues)

Veins and Venules

Function: Carry O2 poor blood toward the heart

Structure: Thinner walls compared to arteries, as pressure is lower. Contain valves to prevent backflow of blood. Skeletal muscle contractions help push blood through veins toward the heart.

● Venules: Small veins that collect blood from capillaries and

transport it to larger veins.

● Blood Reservoir: Veins store about 65% of total blood

volume and can redirect blood to other parts of the body

when needed (e.g. blood loss).

Blood Flow Regulation

● The autonomic nervous system, which controls involuntary functions, regulates the diameter of the arterioles

○ Vasoconstriction: Arterioles constrict to reduce blood flow (e.g., during cold exposure).

○ Vasodilation: Arterioles relax to increase blood flow (e.g., when blushing or during exercise).

● Effects on Circulation:

○ Increased metabolic activity → more vasodilation → increased oxygen supply.

○ Fight-or-flight response → blood redirected to muscles and vital organs.

Common Disorders

● Atherosclerosis: Plaque buildup in arteries, narrowing the passage and reducing blood flow.

● Aneurysm: A weakened artery wall bulges and may rupture, leading to serious complications like a stroke.

● Varicose Veins: Weak or damaged vein valves cause blood pooling, leading to swollen twisted veins.

Cardiac output

Is the amount of blood the heart is able to pump per minute

• Stroke volume × Heart rate

• Average resting person pumps about 4900 mL/min.

Stroke volume

amount of blood pumped per heartbeat

Blood pressure

The force exerted on the arteriole walls by the blood.

Baroreceptors

Pressure-sensitive receptors located in the aorta and carotid arteries that detect changes in blood pressure and signal the brain.

Hypertension

A condition of chronically high blood pressure, increasing the risk of stroke, heart attack, and kidney disease

Sphygmomanometer

A device used to measure blood pressure, typically reported as systolic/diastolic pressure (e.g., 120/80 mmHg).

Systolic Pressure

The pressure in arteries when the heart contracts (ventricular systole).

Diastolic Pressure

The pressure in arteries when the heart relaxes (ventricular diastole).

Metabolic Control of Blood Flow

Blood flow regulation based on tissue activity—active tissues trigger vasodilation for more oxygen, while inactive tissues receive less blood.

Homeostasis

Thermoregulation

The body's ability to regulate temperature by vasodilation (heat release) or vasoconstriction (heat retention).

Filtration

The selective movement of materials through the capillary walls by a pressure gradient into the Extracellular fluid

• At the arterioles pressure is higher than in the Extracellular fluid causing the materials to move out

Reabsorption

Osmotic pressure drives movement of materials from the Extracellular fluid into the venules by a pressure gradient

Extracellular fluid (ECF)

Occupies the gap between cells and tissue made of plasma (not the same one as in blood) and interstitial fluid

• Between capillaries/arterioles/venules and the muscular tissue

Osmotic pressure

The minimum pressure needed to prevent the net movement of solvent (usually water) from a solution with a lower solute concentration to a solution with a higher solute concentration across a semi-permeable membrane

Fluid pressure

the force exerted by a fluid, like blood or interstitial fluid, against the walls of a vessel or tissue

Maintaining Equilibrium in Capillary Fluid Exchange

Balance of osmotic and fluid pressure which is important in maintaining equilibrium in the body

• If disrupted:

  • Hemorrhage (Excessive internal / external bleeding): Decreased blood volume causes fluid pressure to decrease, but osmotic pressure stays the same THEREFORE blood is drawn back into the capillaries (lower filtration)

  • Starvation: Causes swelling, plasma proteins in blood are used as a last resort leading to osmotic pressure to decrease, but fluid pressure stays the same THEREFORE less reabsorption

  • Inflammation (Allergic response): A chemical Histamine is released by cells who believe they are being attacked, this causes capillary permeability to increase (proteins enter ECF) and lowers osmotic pressure THEREFORE less fluid reabsorption

Lymphatic System

Network of vessels and nodes that helps maintain fluid balance and supports the immune system

• Drains excess proteins and fluids from tissues and returns them to the circulatory system/heart

Lymph

Clear fluid similar to blood plasma with white blood cells, proteins, and cellular debris in it

Lymph Vessels

A whole other set of vessels under the capillaries that to the following:

• Transport lymph one-way direction (like veins)

• Contain valves to prevent back-flow (low pressure)

• Depends on muscle contractions and low pressure

Lymph nodes

Found in the intervals along the lymph vessels

Function:

• Filter bacteria, damaged cells, and debris from lymph

• contain white blood cells (lymphocytes) that use phagocytosis (form of endocytosis where white blood cells eat pathogens) to fend off invaders

• swell during infections because of increased immune activity

Lymphoid organs

Places where lymph is stored/produced include:

• Red bone marrow: produces all blood cell types including white blood cells

  • Found in most bones in kids and in the skull, sternum, ribs, spine and long bones

• Thymus Gland: located above the heart and is where T lymphocytes mature

• Spleen: Stores and purifies blood (filters damaged cells)

  • Releases red blood cells in response to low O2 levels or low blood pressure

Main Components of Blood

• 55% Plasma: Fluid portion containing water, electrolytes, proteins, glucose, hormones, and waste.

• 45% Red Blood Cells (Erythrocytes): Transport oxygen via hemoglobin (iron-containing protein)

• <1% White Blood Cells ((Leukocytes): <1%): Defend against infections and foreign substances (pathogens)

• Platelets: Small cell fragments involved in blood clotting

Red Blood Cells (Erythrocytes)

Biconcave disc shape (concave on both sides) → Increases surface area by 20-30% for better gas exchange.

● Primary function: Transport oxygen via hemoglobin (O2 binding protein in red blood cells)

● Lifespan: ~120 days, after which they become brittle and rupture in narrow capillaries (get broken down)

● No nucleus in mature RBCs, allowing more space for hemoglobin but preventing self-replication (continuously broken up, continuously built up)

● RBC count per milliliter of blood:

● Males: ~5.5 billion.

● Females: ~4.5 billion.

● High-altitude individuals (Including Calgary): Up to 8 billion for better oxygen transport

Hemoglobin and Oxygen Transport

Each RBC contains 280 million hemoglobin

molecules.

• Hemoglobin structure:

• Heme group (contains iron) binds to oxygen.

• Globin protein structure supports the molecule.

• Oxyhemoglobin: Hemoglobin bound to oxygen → Bright red color (Arterial Blood).

• Deoxygenated Hemoglobin: When oxygen is released, it changes shape, resulting in a darker red colour (Venous Blood)

Carbon dioxide transport

• 27% binds to hemoglobin → Carbaminohemoglobin.

• 64% forms bicarbonate ions to maintain pH balance

  • Most CO2 is transported as HCO3- in plasma

Erythropoiesis and Cellular Breakdown

Erythropoiesis (How RBC’s are born) is the process by which red blood cells are made

• Produced in bone marrow from nucleated stem cells (undifferentiated potential to become different types of cells)

  • Cells divide and shrink as they take up hemoglobin

  • Eventually nucleus disappears

Breakdown process: Occurs in spleen and liver.

• Hemoglobin breakdown → Iron is stored in liver and bone marrow for new RBC production.

• Heme group → Converted into bile pigments (in liver)

RBC Disorders and Adaptations

• Anemia: Low RBC or hemoglobin levels → Reduced oxygen delivery, fatigue, weakness.

• Causes: Blood loss, iron deficiency, bone marrow

disorders, genetics (sickle cell anemia)

• Erythropoietin (EPO): Hormone that stimulates RBC production in response to low oxygen levels.

• High-altitude adaptation: People who live at high altitudes have more hemoglobin for efficient oxygen transport

Blood Types

• Discovered by Karl Landsteiner in the early 20th century.

• Differences in blood types are due to glycoprotein markers (antigens) on red blood cells

  • Antigens are a surface marker of cells (exist to signal to the immune cells that they are a part of the body)

ABO Blood Group System

• Blood types are classified based on A and B antigens present on red blood cells.

• Individuals also have antibodies in their plasma that react against foreign blood antigens.

Agglutination (clumping)

occurs if incompatible blood types mix.

● Example: Type O cannot receive A or B blood because it produces antibodies against both antigens

Rhesus (Rh) Factor

A separate blood antigen discovered in the 1940s.

● Rh+ individuals have the Rh antigen; Rh- individuals lack it.

● Rh- individuals should not receive Rh+ blood as their immune system may develop antibodies against it (anti-Rh antibodies)

Universal Donor

Blood Type O- because there are no antigens so it doesn’t trigger the immune system

Universal Recipient

Blood Type AB+ because it has all of the antigens so it doesn’t produce antigens against any blood types

Mismatched Transfusions

Can cause fatal immune reactions due to agglutination and blockage of the capillaries

Rh Incompatibility in Pregnancy (Erthroblastosis Fetalis)

Only occurs in Rh- mothers carrying a Rh+ baby

• Rh- mother, Rh+ father

• The first pregnancy usually has little danger but during childbirth fetal and maternal blood can mix in the mothers bloodstream triggering the production of antibodies in the blood

• In the second and all other pregnancies the maternal antibodies that formed in the first birth attack the Rh+ fetus and causes anemia, jaundice and organ enlargement

• ALL of this can be prevented by the RhoGAM injection which prevents antibody formation

Platelets (Thrombocytes)

They have no nucleus, are irregular shapes, and are produced in bone marrow.

• Initiates the Blood Clotting Process in 3 steps

• Platelet Activation:

  • When a blood vessel is injured platelets adhere to the damaged area

  • platelets change shape and release clotting factors such as Thromboplastin

• Formation of a Clotting Cascade

  • Thromboplastin (from platelets) + Calcium Ions —> Activates Prothrombin

  • Prothrombin (A plasma protein from the liver) is converted to Thrombin

• Formation of Fibrin Mesh

  • Thrombin acts like an enzyme, cutting amino acids from fibrinogen (another plasma protein)

  • The fibrinogen then converts to fibrin and fibrin forms a mesh that traps the red blood cells and more platelets to seal the wound

    • This is what a scab is on external wounds

Blood Clot Disorders

Cerebral Thrombosis: Clot in the Brain (causes a stroke)

Coronary Thrombosis: Clot in the coronary artery (causes a heart attack)

Embolism: A clot (embolus) dislodges and moves through the bloodstream potentially blocking vital organs

The Immune System

Protects the body from harmful invaders like bacteria, viruses, and toxins.

Antigens

Are foreign substances (proteins on pathogens) that trigger an immune response

• The immune system recognizes its own antigens and attacks foreign antigens

Defense System of the Immune System

• The first line of defence is physical and chemical barriers with physical barriers like skin which encapsulates the whole body for protection, mucous membranes that can trap pathogens inside of its sticky mucus. The chemical barriers which would burn or disintegrate the pathogens include acidic skin secretions, stomach acid, and lysozymes in saliva and tears. 

• The second line of defence is non-specific immunity where phagocytosis occurs which is when macrophages or neutrophils swallow the pathogens. It also has the inflammatory response in which is when the body increases blood flow to the affected area to bring immune cells (like phagocytes) to fight pathogens.

• The third line of defence is specific immunity which involves lymphocytes (B cells and T cells), which recognize and attack specific pathogens. There are 3 types of B and T cells including: helper T cells which activate B cells, killer T cells which Destroy infected cells by puncturing the membranes, suppressor T cells which Inhibit the immune response, plasma B cells which Produce lots of antibodies, and memory B cells which store antigen information for faster responses in the future

Antibody-Antigen Interaction

Antibodies bind to Antigens —> Form antigen-antibody complexs which:

• Mark pathogens for destruction by macrophages

• Neutralize toxins by blocking their binding sites

• Prevent viruses from attaching to host cells

  • covering acceptors

Immune Memory and Vaccination

• Memory B cells ensure a faster and stronger response upon reinfection

• Vaccines introduce weakened pathogens to stimulate memory cell production