Test 3

What is systemic circulation?

The flow of blood throughout the body.

What is parallel blood flow?

A circulatory arrangement where organs receive blood side-by-side, ensuring that an injury to one vessel does not interrupt blood supply to other organs.

What is a pressure gradient?

The difference in pressure between two points in the circulatory system.

Why does blood flow from arteries to capillaries to veins?

Fluids flow from high pressure to low pressure; arteries have high pressure, capillaries and veins have low pressure.

What is the myocardium?

The thick, muscular middle layer of the heart wall, composed of cardiac muscle tissue responsible for contraction.

What is a cardiac myocyte?

A striated, branching muscle cell found in the heart, containing many mitochondria and specialized structures called intercalated disks.

What is an intercalated disk?

A specialized cell junction in cardiac muscle containing desmosomes and gap junctions, enabling synchronized contraction.

What is a gap junction?

A channel protein that allows ions to pass directly from the cytoplasm of one cardiac cell to another, permitting rapid spread of action potentials.

What are the two components of intercalated disks and their functions?

Desmosomes hold adjacent cells together, interlocking them; gap junctions allow ions to move between cells, allowing action potentials to travel quickly from cell to cell.

How does cardiac muscle tissue contract to produce greater force?

It forms concentric layers that spiral around the ventricles and contracts in a twisting motion (like wringing out a rag).

What is systole?

The phase of the cardiac cycle during which the ventricles contract, ejecting blood into the arteries; also involves atrial relaxation.

What is systolic blood pressure?

The arterial pressure measured during ventricular contraction, when blood is pushed out of the heart under high pressure (the pulse felt in the wrist).

What is diastole?

The phase of the cardiac cycle during which the ventricles relax and fill with blood; also involves atrial contraction.

What is diastolic blood pressure?

The arterial pressure measured during ventricular relaxation, when the heart is filling with blood.

What is End Diastolic Volume (EDV)?

The volume of blood loaded into a ventricle just before it contracts and ejects the blood; also known as preload.

What is End Systolic Volume (ESV)?

The volume of blood remaining in a ventricle after it has finished contracting and ejecting blood.

What is Stroke Volume (SV)?

The volume of blood pumped out of the heart per contraction; calculated as SV = EDV - ESV.

If EDV = 118 mL and ESV = 45 mL, what is the stroke volume?

SV = 118 mL - 45 mL = 73 mL.

What is Cardiac Output (CO)?

The volume of blood pumped out of the heart per minute; calculated as CO = SV × Heart Rate (HR).

If stroke volume is 70 mL per contraction and heart rate is 70 bpm, what is the cardiac output?

CO = 70 mL × 70 bpm = 4900 mL/min = 4.9 L/min.

What is the cardiac cycle?

The complete sequence of events in the heart from the start of one heartbeat to the next, lasting approximately 0.8 seconds.

What are the two main phases of the cardiac cycle?

Systole (ventricular contraction, ~0.3 seconds) and diastole (ventricular relaxation, ~0.5 seconds).

What is isovolumetric contraction?

The brief phase where the ventricles contract but all valves are closed, so no blood moves and ventricular pressure rises.

What is isovolumetric relaxation?

The brief phase where the ventricles relax with all valves closed, resulting in no change in blood volume as pressure drops.

During mid-diastole, why are AV valves open?

Because pressure in the atria is greater than pressure in the ventricles.

During mid-diastole, why are semilunar valves closed?

Because pressure in the aorta/pulmonary artery is greater than pressure in the ventricles.

During isovolumetric contraction, why are both AV valves and semilunar valves closed?

AV valves close because ventricular pressure exceeds atrial pressure; semilunar valves remain closed because aortic/pulmonary pressure exceeds ventricular pressure.

During ejection (systole), why do semilunar valves open?

Because ventricular pressure exceeds pressure in the aorta and pulmonary artery.

What is a pacemaker cell?

A specialized cardiac cell (primarily in the SA node) that automatically depolarizes to generate an action potential and set the heart rate.

What is the pacemaker potential?

The slow, spontaneous depolarization of pacemaker cells that drives the membrane potential toward threshold to trigger a heartbeat.

What is the sinoatrial (SA) node?

The natural pacemaker of the heart, located in the right atrium, which initiates each heartbeat and sets the heart rate.

What are the three phases of a pacemaker cell action potential?

Phase 1 (slow/pacemaker potential): more Na⁺ enters than K⁺ leaves, slow increase in membrane potential. Phase 2 (depolarization): Ca²⁺ channels open, Ca²⁺ flows in. Phase 3 (repolarization): K⁺ channels open, K⁺ flows out.

What determines heart rate?

The frequency of pacemaker potentials (the slope of phase 1/slow phase).

How does the SA node trigger continuous wave-like contraction of the heart?

When the SA node triggers a heartbeat, depolarization rapidly flows from cell to cell via gap junctions in intercalated disks.

What are the four events of cardiac muscle contraction?

1. Voltage-gated Ca²⁺ channels open, rapid Ca²⁺ influx causes depolarization. 2. Ca²⁺ released from SR binds to troponin, forming cross-bridges. 3. During repolarization, Ca²⁺ release channels close and Ca²⁺ pumps move Ca²⁺ back into SR. 4. Na⁺/Ca²⁺ pumps bring Na⁺ into cell and Ca²⁺ out of cell to restore resting potential.

What effect does the sympathetic nervous system (SNS) have on heart rate?

Increases heart rate by acting on beta-adrenergic receptors on SA node cells with epinephrine and norepinephrine (catecholamines).

What effect does the parasympathetic nervous system (PSNS) have on heart rate?

Decreases heart rate by acting on muscarinic receptors on SA node cells with acetylcholine.

What is the Frank-Starling Law?

The principle that the heart increases its force of contraction (and thus stroke volume) in response to increased venous return and end-diastolic volume (EDV).

What happens to stroke volume when you stand up (venous blood pressure drops)?

Less blood fills the ventricle (lower EDV), causing a decrease in stroke volume.

What happens in heart failure regarding the Frank-Starling mechanism?

The ventricle cannot increase its contraction force and stroke volume to match an increase in venous return; adding more blood has no effect.

What is contractility?

The intrinsic strength of the heart's contraction; higher contractility leads to higher stroke volume (more efficient pumping).

How does higher contractility increase stroke volume?

More Ca²⁺ is released from the sarcoplasmic reticulum, forming more actin-myosin cross-bridges, leading to stronger contractions and higher stroke volume.

How does reduced contractility affect stroke volume?

Fewer Ca²⁺ are released from the SR, forming fewer cross-bridges, leading to weaker contractions and lower stroke volume.

What are baroreceptors?

Pressure receptors located in blood vessels that send sensory input to the brain (cardiac center) to help regulate heart rate and blood pressure.

What are chemoreceptors?

Receptors that detect chemical changes (such as pH or CO₂ levels) and send sensory input to the cardiac center to adjust heart rate accordingly.

Where is the cardiac center located?

In the medulla of the brainstem.

What is microbiology?

The study of very small living organisms (microorganisms or microbes) that are usually too small to be seen with the unaided eye.

What does the word "microbiology" literally mean?

Micro = very small (viewed with a microscope), bios = living organisms, logy = the study of.

How far back does microbiology date as a science?

Only about 200 years.

What was the belief about disease before the microscope was invented?

Disease was believed to be a punishment for crimes; villages became ill from "demons" appearing as foul odors from sewage/swamps (miasma theory).

What was the Black Death (The Plague)?

A pandemic caused by the bacterium Yersinia pestis, transmitted from rats to humans by fleas.

How many people died in the first Black Death pandemic?

(mid-500s A.D.): 40 million.

How many people died in the second Black Death pandemic?

(14th century): 25 million.

Where did the third Black Death pandemic spread?

(1860s): spread from China across Asia, Africa, Europe, and the Americas.

What happens to a flea infected with Yersinia pestis?

The bacteria multiply in the flea, blocking its digestive tract, causing the starving flea to jump to a new host (e.g., a human).

What are the symptoms of untreated plague?

Within a week: high fever, swollen lymph nodes (buboes), leading to intravascular coagulation and subcutaneous hemorrhaging (tissue death).

What is the mortality rate of untreated plague?

50-75%; death can occur less than one week after onset of symptoms.

What antibiotics are available to treat plague?

Streptomycin, gentamycin, tetracycline, and chloramphenicol.

How many cases of plague occur worldwide per year?

1,000-3,000 cases.

List three environmental impacts of microbes.

Maintain balance of life in oceans/lakes/rivers; convert nitrogen gas into organic compounds; break down wastes returning CO2; produce methane and ethanol; play a role in photosynthesis.

List four food products produced by microbes in the food industry.

Cheese, yoghurt, bread, alcoholic beverages.

What vitamins do microbes in human intestines produce?

Vitamin K (for blood clotting) and B vitamins (for metabolism).

What is a pathogenic microorganism?

A disease-producing microbe.

How many Hospital Acquired Infections (HAIs) occur each year in Canada, and how many deaths result?

220,000 HAIs result in 8,500-12,000 deaths annually.

What is the rate of hospital patients who get an HAI?

1 in 9 hospital patients.

Between 1995-2006, how much did the incidence of MRSA increase?

Increased 17-fold.

Between 1991-2003, how much did the number of patients contracting C. difficile increase?

Increased 5-fold.

What does MRSA stand for?

Methicillin-Resistant Staphylococcus aureus.

What infections can Staphylococcus aureus cause?

Pimples, pneumonia, food poisoning, wound infections.

How is MRSA spread?

By skin-to-skin contact.

What are the signs of a MRSA infection on the skin?

Red, swollen, painful; pus or fluid may drain.

Who is credited with discovering "cells" in 1665?

Robert Hooke.

What did Anton van Leeuwenhoek discover in 1673?

"Animalcules" (now known as bacteria and protozoa), found in rainwater, his own feces, and material scraped from his teeth.

What are the six categories of microorganisms?

Bacteria, Archaea, Fungi, Protozoa, Multicellular animal parasites (helminths), and Viruses.

What are the characteristics of bacteria?

Unicellular, prokaryotic (no nucleus), enclosed in cell walls composed of peptidoglycan, reproduce by binary fission, use organic chemicals for nutrition, some have flagella for swimming.

What are the three main groups of Archaea based on their environment?

Methanogens (produce methane), extreme halophiles (salty environments), and extreme thermophiles (hot sulfurous water).

Do Archaea cause disease in humans?

No, Archaea are not known to cause disease.

What are the characteristics of fungi?

Eukaryotic (have a nucleus), cell walls composed of chitin, absorb nutrients from environment, reproduce sexually or asexually; includes multicellular (mushrooms, molds) and unicellular (yeast) forms.

What are the characteristics of protozoa?

Unicellular eukaryotes, most are capable of locomotion (pseudopods, flagella, cilia), live as free entities or inside hosts where they can cause disease, reproduce sexually or asexually.

What are the characteristics of algae?

Unicellular or multicellular eukaryotes, cell walls contain cellulose, perform photosynthesis (produce oxygen and carbohydrates), reproduce sexually or asexually.

What are the two major classes of multicellular animal parasites (helminths)?

Flatworms and roundworms.

Are helminths strictly microorganisms?

No, only certain stages of their life cycle are microscopic.

What is the basic structure of a virus?

Very small (visible only with electron microscope), acellular, core made of either DNA or RNA (not both), core surrounded by a protein coat.

Are viruses considered living organisms?

Only when they multiply within a living host; they are inert (non-living) outside a living host.

What are the three domains of classification for microorganisms?

Bacteria, Archaea, and Eukarya (which includes protists, fungi, plants, and animals).

What is the correct format for writing a microorganism's scientific name?

First name (genus) capitalized, second name (species) not capitalized, both underlined or italicized. After first use, genus may be abbreviated (e.g., Staphylococcus aureus → S. aureus).

What did Francesco Redi demonstrate in 1668?

He challenged spontaneous generation by showing that maggots arise from flies, not from decaying corpses.

What did John Needham's experiment show in 1745?

Nutrient broth heated and then placed in a sealed flask still showed microbial growth (supporting spontaneous generation).

What did Rudolf Virchow claim in 1858?

Living cells can arise only from pre-existing living cells (biogenesis), challenging spontaneous generation.

What did Louis Pasteur's S-shaped flask experiment demonstrate in 1861?

Microorganisms can be present in nonliving matter, microbial life can be destroyed by heat, and methods can be devised to block access of airborne microorganisms.

What process did Pasteur discover that converts sugars to alcohol in the absence of air?

Fermentation (carried out by yeasts).

What is pasteurization?

Heating beer and wine just enough to kill bacteria, preventing spoilage.

What was the "miasma theory"?

The belief that disease was caused by "bad air" or foul odors from sewage and swamps, not by invisible microbes.

What observations did Ignaz Semmelweis make in the 1840s?

Childbed fever deaths were much higher in the division with doctors and medical students (600-800 deaths) than the division with midwives (60 deaths), because physicians didn't disinfect their hands.

What did Joseph Lister do in the 1860s?

Applied the Germ Theory to medical procedures, treating surgical wounds with phenol solution, greatly reducing infections and deaths.

What did Robert Koch discover in 1876?

The rod-shaped bacterium Bacillus anthracis, the cause of anthrax.

What did Edward Jenner discover in 1796?

Vaccination: infecting an 8-year-old boy with cowpox protected him from smallpox.

What is vaccination?

A process to protect from disease; protection from disease by vaccination or recovery is called immunity.

What is chemotherapy?

Treatment of disease by use of chemical substances; success depends on chemicals being more poisonous to microbes than to humans.

What are antibiotics?

Chemicals produced naturally by bacteria and fungi that act against other microorganisms.