Human Physiology Quiz on Cardiac Function

Control of the Heart

• Home is where the heart is.
• Cardiac muscle (myogenic muscle) contracts without external stimulation.
• Heart contractions are caused by electrical impulses from nodes within the heart.

Control of the Heartbeat

• Cardiac muscle, unlike other muscles, doesn't require external stimulation to contract.
• Heart contractions are due to electrical signals from two heart nodes.
• The nodes are named the sinus node and atrioventricular node
• The electrical impulses travel via various heart structures (bundle of His, right/left bundle branches, Purkinje fibers)
• The sinoatrial (SA) node and the atrioventricular (AV) node are important in controlling the heartbeat.

Internal Control

• The SA node (pacemaker), located in the right atrium, sets the heart's rhythm.
• Nerve impulses travel from the SA node to other cardiac muscle cells via modified muscle tissues.
• Cardiac muscle contracts automatically, producing electrical signals.
• Approximate heart rate is 70 beats per minute, with 70mL of blood being pumped out per beat.
• Heart rate starts with the contraction of the atria, which pushes blood into the ventricles

Atrioventricular Node (AV node)

• The AV node picks up the electrical impulses from the SA node.
• The impulses cause the ventricles to contract, pushing blood out to the lungs and body.
• It passes nerve impulses along special fibers (Purkinje fibers) to initiate ventricular contractions.

Diastole and Systole

• Diastole refers to the heart at rest.
• Systole refers to the heart contracting to pump blood.
• The SA and AV nodes are involved in controlling these phases of the heartbeat.

Heart Electrical Activity Summary

• The images show the electrical signals moving through different parts of the heart (atria, ventricles, AV node, SA node) during diastole and systole via conducting fibers, for example, bundle branches and Purkinje fibers.
• The sequence of activation can be seen in different images.

Artificial Pacemaker

• An artificial pacemaker emits electrical signals to regulate the heartbeat if the SA node isn't functioning correctly.
• Irregular heartbeat is called arrhythmia

External Control

• Two nerves of the autonomic nervous system (sympathetic and parasympathetic) regulate heart rate.
• Sympathetic nerves increase heart rate during stress (fight or flight response).
• Parasympathetic nerves slow the heart rate during relaxation.
• The medulla oblongata (part of the brain) responds to the body's needs by influencing the pacemaker (SA node) via nerve impulses.

Adjustment Due to Exercise

• Increased carbon dioxide levels in the blood during exercise stimulate the medulla oblongata.
• This triggers a nerve impulse to the SA node.
• The increased heart rate moves blood to the lungs, removing excess carbon dioxide.

Other Factors Affecting Heart Rate

• High temperature increases heart rate.
• Hormones, such as adrenaline, also increase heart rate.

Disorders of the Circulatory System

• Atherosclerosis is the buildup of fatty material inside arteries, which can cause the arteries to become hard.
• This may cause high blood pressure, and/or rupture in arteries.
• A blood clot may also form inside the arteries.
• A heart attack occurs when blood flow to the heart is blocked, resulting in the death of heart muscle.
• Angina is chest pain caused by reduced blood flow to the heart muscle.
• Stroke occurs when a blood clot lodges in a blood vessel in the brain, or if a blood vessel ruptures. Tissues damage becomes significant after about 4 minutes, and can result in death or mental/physical problems

Embolus

• A blood clot that dislodges inside a vessel, and later jams in another vessel.

Aneurysm

• Aneurysms are due to a weak spot in an artery that causes a bulge in the artery wall.
• If left untreated, may be extremely dangerous resulting in a rupture and instant death.

Lymphatic System

• The lymphatic and circulatory systems are closely related; they interact and are similar to one another.
• The lymphatic system returns extracellular fluid (containing protein and bacteria that leaked from capillaries) back to the circulatory system.
• Lymph is fluid (containing protein) that leaks out of the capillaries.
• Lymph flows through lymph vessels due to skeletal muscle contractions to prevent backflow (similar to veins).
• Lymph nodes filter lymph for foreign particles, combating infections using white blood cells and phagocytosis.

Blood Structure and Function

• Blood is made up of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.
• Plasma is about 55% of blood volume; RBCs about 44%; and WBCs & Platelets about 1%.
• Plasma is mostly water, and includes proteins (like fibrinogen), glucose, vitamins, minerals, gases, and waste products.
• RBCs carry oxygen to tissues and exchange with carbon dioxide for respiration. They are short lived (about 120 days) and contain hemoglobin to carry O₂. They have no nucleus when mature to maximize space for hemoglobin.
• WBCs (leukocytes) combat infections through phagocytosis. They also produce antibodies for immunity. They are the largest of blood cells and each one has a nucleus.
• Platelets play a critical role in blood clotting by secreting specialized proteins.

Blood Typing

• There are four basic blood types (A, B, AB, O) determined by antigens on red blood cells.
• Antibodies in blood plasma are made against other blood types and will clump (agglutinate) with their opposing antigen.
• Blood typing is important for blood transfusions (avoiding clumping and blood blockages).

Rhesus (Rh) Factor

• The Rh factor (another antigen) is present or absent on red blood cells.
• Rh+ is present in about 85% of people.
• Rh- is present in about 15% of people.
• Humans do not naturally have Rh antibodies; an Rh- person can receive Rh+ blood in a transfusion.
• Rh antibodies can be produced after an Rh- individual receives Rh+ blood in a transfusion, creating issues with blood clumping and blocking.

Rh and Pregnancy

• If the mother is Rh- and the father is Rh+, the child might be Rh+.
• If it's the first child, this is not an issue.
• During birth, maternal and fetal blood mix.
• The mother's immune system produces Rh+ antibodies.
• The second child (if Rh+) will be attacked by antibodies from mother resulting in potentially fatal issues.

Erythroblastosis Fetalis

• The condition occurs when a Rh- mother has an Rh+ second or subsequent child.
• Mixing fetal and maternal blood during or after birth activates the mother's immune system, causing the production of Rh+ antibodies.
• The antibodies attack the Rh+ fetal red blood cells, causing clumping and decreased oxygen delivery (resulting in a 'blue baby').
• Transfusion of Rh- blood to the baby is the typical solution.

Sickle Cell Anemia

• Sickle cell anemia is a genetic blood disorder.
• In this condition, the hemoglobin is defective causing the red blood cells to become 'sickle-shaped', thus blocking blood flow through capillaries.
• This can lead to numerous health issues.

Hemophilia

• Hemophilia is a genetic condition wherein the ability to clot blood is affected.
• It can be life-threatening as it can involve uncontrolled blood loss.
• Transfusions can help address this problem and manage this condition.

Leukemia

• Leukemia is a cancer of the white blood cells.
• The number of WBCs increases, but the cells do not function normally.

Immunity

• The immune system defends the body against pathogens (bacteria, viruses, fungi, and protozoa that can cause disease).
• A series of physical (skin, stomach acid, cilia, mucous) and non-barrier (inflammation, antibody production) defenses protect against antigens.
• The immune system can detect and fight invaders using antibodies and other immune response mechanisms.
• Pathogens have marker proteins (antigens) that trigger antibody production when they enter the body.

Barrier Responses

• Skin (layers of dead cells, oil, and sweat)
• Digestive system (stomach acid, enzymes)
• Gas exchange (hair, cilia, mucus, coughing, and sneezing)
• Urinary system (mucus, periodic flow of urine)

Levels of Immune Protection

• Innate response (physical barriers, phagocytic cells)
• Acquired response (cellular and humoral responses, including memory immune responses)

Non-Barrier Responses

• Inflammation is a response triggered when a pathogen enters the body.
• Antibody production is the process by which antibodies are generated in the body in response to foreign antigens.

HIV

• HIV (Human Immunodeficiency Virus) is a virus that can live in T-cells for days or even years, potentially not being active immediately.
• Active HIV uses the helper T-cells' DNA to reproduce; when the helper T-cell bursts, HIV spreads to other T-cells.
• HIV decimates T-cells, which can eventually lead to AIDS (Acquired Immunodeficiency Syndrome), wherein the immune system is poorly functioning.

Vaccines

• Vaccines introduce a weakened or dead virus to the body to stimulate an immune response.
• This helps the body develop antibodies to prepare the immune system for future infections by the same pathogen.
• Second exposure to the antigen is met with a stronger and faster immune response due to memory cells.

Antibiotics

• Antibiotics are medicines used to combat bacterial infections.
• Overuse of antibiotics can lead to antibiotic-resistant bacteria, making treatment more difficult or impossible in the future.

Blood Sample Problems

• Blood samples can be analyzed using different tests to determine if there are any abnormalities in the blood cell composition.
• Common issues include low iron levels (anemia), high altitude, infection, heart disease, COPD, leukemia, and injury requiring clotting.

Blood Pressure

• Blood pressure is the force exerted by the ventricles of the heart against the artery walls when they contract and relax.
• Systolic pressure pertains to the heart pumping blood.
• Diastolic pressure is the pressure when the heart is at rest between beats.
• Increased blood pressure (hypertension) is associated with an elevated risk of strokes, heart attacks, and kidney failure, as well as dementia and sexual problems.
• Low blood pressure (hypotension) can cause dizziness, fatigue and can cause organs like the heart, brain and kidneys to not receive enough blood.
• Lab work involving blood pressure uses a cuff and stethoscope.

Test your knowledge of human physiology, focusing specifically on cardiac function and the nervous system's role in heart activity. This quiz covers the effects of stress, exercise, and various heart conditions. Perfect for students studying biology and physiology!