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 repolarization (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

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.

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).