Chapter 48 Cardiovascular System

Question 1

What are the basic components of a circulatory system?

Answer 1

1) Heart (muscular pump) moves ECF and generates pressure
2) Blood (fluid composed of plasma and blood cells made of connective tissue)
3) Blood Vessels (series of conduits: arteries, arterioles, capillaries, venules, veins)

Question 2

What are the functions of the circulatory system?

Answer 2

1) Transport material around body (oxygen, nutrients, hormones, blood, heat, CO2, urea)
2) Supports lymphatic system (transports immune cells and platelets)
3) pH stability (HCO3- buffer system in blood)
4) Body temperature (balances temperature by moving heat from active sites such as liver –> less active sites)
5) Prevents major blood loss (platelets + fibrinogen = fibrin; fibrin produces blood clots)

Question 3

How do organisms with no circulatory system get energy?

Answer 3

• Extract energy from their environment using diffusion
• Have gastrovascular systems that bring environment to organism

Question 4

What are the components of an open circulatory system?

Answer 4

• ECF = hemolymph instead of blood
• Hemolymph is used to transport nutrients by leaving vessels –> tissues –> heart

(Generally found in arthropods, mollusks, and some invertebrates like insects)

Question 5

What are the components of a closed circulatory system?

Answer 5

• 2 ECFs: blood plasma (in heart and vessels) and interstitial fluid
• Blood is in a continuous system of vessels and only plasma and immune cells leave vessels to allow faster blood transport
• Diameter of blood vessels change to allow flow to tissues in need

(Generally found in vertebrates and some invertebrates like annelids)

Question 6

How does a 1 circuit circulatory work and what organisms tend to have these?

Answer 6

• Typically seen in fish
  Heart –> gills –> tissue –> heart (Unidirectional blood flow is done by one-way valves)

1) Blood collects in sinus venosus
2) Flows to atrium
3) Atrium –> Ventricle
4) Ventricle contracts –> bulbus arteriosus
5) Bulbus arteriosus –> gills (blood gets oxygenated and respiratory gases changed)
6) Gills –> aorta –> arteries & arterioles –> tissues
7) Tissues –> Capillary Beds –> Venules & Veins –> Sinus Venosus

Question 7

What are the two types of closed circulatory systems and how do they work? Which organisms have these systems?

Answer 7

1) Pulmonary Circuit: heart –> lungs –> heart
2) Systemic Circuit: heart –> body (except lungs) –> heart

Typically seen in birds and mammals.

Question 8

What advantage does separation of blood in the heart have?

Answer 8

Maintains a high level of oxygen in systemic blood

Question 9

Which organisms show the transition from respiration in water –> air and how?

Answer 9

Lungfish!
- Most fishes have 6 gill arches to get O2; lungfish have 3 to get O2 from gills and 3 to get O2 from lungs
- Lungfish split the heart into deoxygenated blood from body (right side of atria) and oxygenated blood from lungs (left side of atria)
- Blood is separated from mixing using pulmonary and systemic circuits

Question 10

How many chambers are in amphibians’ hearts and what is the anatomy?

Answer 10

3 chambers (2 atria deliver blood to one ventricle)
- left atria brings oxygenated blood from lung
- right atria brings deoxygenated blood from body
Oxygenated + deoxygenated blood could mix so blood is not fully oxygenated at tissues

Question 11

How many chambers are in reptiles’ hearts and what is the anatomy?

Answer 11

Either 3 or 4 chambers
1) 3-chambered heart: ventricle is divided by a septum which moves oxygenated blood to body and deoxygenated blood to the lungs
- When resting, both ventricles goes to aorta but when active blood from right ventricle –> lung and blood from left ventricle –> aorta
2) 4-chambered heart: completely divided ventricles, but can shunt blood to pulmonary or systemic circuit via connection between two aortas
- Oxygenated+ deoxygenated blood don’t mix (body gets highest O2 content) so respiratory gas exchange is maximized (blood with lowest O2 + highest CO2 goes to lungs)

Question 12

How many chambers are in human hearts and what is the anatomy?

Answer 12

4 chambers (2 atria and 2 ventricles separated by interventricular septum)
- Right atria receives blood from systemic circuit after right ventricle pumps blood through pulmonary circuit
- Left atria receives blood from the pulmonary circuit after left ventricle pumps blood through the systemic circuit

Question 13

What is the purpose of the atria, what are the two parts and the valves that make it up?

Answer 13

The atria brings blood into the heart
1) Right atria is venous flow from the systemic circuit (superior and inferior vena cava - O2 poor blood)
2) Left atria is venous flow from the pulmonary circuit (lungs + pulmonary veins - O2 rich blood)

Atrioventricular Valves (AV): one-way valves between the atria and ventricles that prevent backflow of blood into atria when ventricles contract
1) Right AV is the tricuspid valve (right atrium + right ventricle) made up of 3 flaps
2) Left AV is the bicuspid or mitral valve (left atrium + left ventricle) made up of 2 flaps

Question 14

What is the purpose of the ventricles and how are they divided?

Answer 14

Ventricles push blood out of heart.
1) Right ventricle pushes blood to lungs via pulmonary artery
2) Left ventricle pushes blood to aorta into systemic circulation

Question 15

What shape are the pulmonary and aortic valve and what are the purpose of the two valves?

Answer 15

They are semilunar valves since they are in the shape of half-moons.

Pulmonary valve goes to lungs and is between the right ventricle and pulmonary artery , aortic valve goes to aorta and is between the left ventricle and aorta.

Question 16

What is the aorta?

Answer 16

The aorta is the largest artery in the body covered by thick connective tissue which limits its elasticity so blood is pushed forward.

Question 17

How do the superior vena cava and inferior vena cava work?

Answer 17

SVC returns deoxygenated blood from upper body to right atrium
UVC returns deoxygenated blood from lower body to right atrium.

Question 18

Describe flow of blood in pulmonary vs. systemic circuit.

Answer 18

Pulmonary circuit:
Right ventricle – via pulmonary valve –> pulmonary artery –> lungs –> pulmonary veins –> left atrium –> bicuspid value –> left ventricle

Systemic Circuit:
Left ventricle – via aortic valve –> aorta –> rest of body (except lungs) –> SVC/IVC –> right atrium –> tricuspid valve –> right ventricle

Question 19

How do the ventricles fill and empty? What are those interactions called?

Answer 19

1) 2 atria contract
2) 2 ventricles contract
(*atria and ventricles contract at the same time)
3) relaxation

Systole: ventricles contract (“lub”)
Diastole: ventricles relax (“dub”)

Question 20

When you measure blood pressure what are the two values you need? What is the average healthy BP?

Answer 20

Systolic value: pressure needed to compress an artery so blood doesn’t flow
Diastolic value: pressure needed to allow intermittent flow through artery

• 120/80

Question 21

What are sounds of the cardiac cycle caused by?

Answer 21

• They are caused by the heart valve slamming shut
• The valves open and close due to pressure differences on 2 sides of the valves

Question 22

What happens when valves don’t fully close?

Answer 22

Heart murmurs which cause (“whoosh”) sounds

Question 23

What causes the heart to beat?

Answer 23

Gap Junctions: allow cardiac cells to communicate with each other (action potential spreads rapidly) causing large groups of cardiac muscle to contract in unison allowing more efficient blood pumping

Pacemaker cells: initiate action potentials without input from the nervous system
- Sinoatrial node is the primary pacemaker of the heart located at the junction of the SVC and right atrium

Ventricles don’t contract in unison with aorta since they aren’t attached

Question 24

What sequence of events causes atrial and ventricular contraction?

Answer 24

1) Sinoatrial node fires and atria contract
2) Atrioventricular node fires since atria is depolarized and action potential goes from atria to ventricles
3) Bundle of His: conduct action potentials but do not contract; they are divided into left and right bundle branches that run to tips of ventricles
4) Purkinje Fibers: go from tips of ventricles all throughout ventricles to allow rapid and even contraction
5) Ventricles Contract

Question 25

How is action potential generated?

Answer 25

1) Resting potential of pacemaker cells are unstable due to cation channels
2) In pacemaker cells Na+ enters more easily than K+ generating a less negative membrane potential
3) Since membrane potential is less negative, Ca2+ channels (T-type/transient) open and membrane potential rises
4) Once membrane potential reaches threshold, Ca2+ channels (L-type/long-lasting) open and action potential is generated

Question 26

What does the autonomic nervous system do and what are the two parts?

Answer 26

The autonomic nervous system controls heart rate.
1) Sympathetic (“fight or flight”): speeds up heart rate
- Norepinephrine increases permeability of Na+/K+/Ca2+ channels and resting potential rises more rapidly and action potentials are closer together
2) Parasympathetic: (“rest and digest”) slows down heart rate
- Acetylcholine causes increased K+ permeability and decreased Ca+ permeability so resting potential rises slowly and action potentials are farther apart

Question 27

How does the ECG/EKG work?

Answer 27

1) P-wave: depolarization (contraction) of atria
2) QRS-wave: depolarization (contraction) of ventricle
3) T-wave: repolarization of ventricles

Question 28

What are the different types of blood vessels and their functions?

Answer 28

1) Arteries: carry blood away from heart (includes aorta and pulmonary artery)
2) Arterioles: artery branches
3) Capillaries: tiny, thin-walled vessels where materials are exchanged
4) Venules: small vessels that drain capillary beds
5) Veins: deliver blood towards heart (include SVC/IVC and pulmonary vein)

Question 29

What are the tissue layers in blood vessels and the heart?

Answer 29

1) Endothelium: innermost epithelium
2) Muscular Layer: cardiac or smooth muscle + connective tissue
3) Connective Tissue: outer layer of CT with elastin and collagen fibers

Question 30

How does the anatomy of blood vessels affect their function?

Answer 30

1) Artery: large, muscular, and elastic
2) Arteriole: small, less muscle, and sphincters (resistance vessels control blood flow)
3) Capillary: small, no muscle, large surface area
4) Venules: larger than capillaries, not elastic or muscular
5) Veins: large, some muscle, and valves

Question 31

How do large arteries withstand high BP?

Answer 31

Walls of large arteries have collagen and elastin fibers to withstand high BP
- Stretched during systole to store some heart contraction energy
- Elastic recoil during diastole squeezes blood and pushes it forward

Capillaries have small diameter and slow blood flow; have a single layer of endothelial cells
- Permeable to water, ions, and small molecules
- Not permeable to large proteins and red blood cells

Question 32

What do sphincters do and what are they made up of?

Answer 32

Sphincters control amount of blood in capillaries
1) Precapillary sphincters: can shut off blood supply by deciding which capillaries get the most blood
2) Autoregulation: depends on smooth muscle being sensitive to its chemical environment
a) Arteries and arterioles are innervated by the sympathetic nervous system
b) Norepinephrine causes arterioles to constrict in tissues not needed for “fight or flight” response (limits blood flow)
c) Hormones regulate pressure

Question 33

What two parts in capillaries force water in and out?

Answer 33

1) BP forces water and small solutes out of capillary
2) Osmotic pressure draws water back into capillary

*Where BP>osmotic pressure, fluid leaves the capillary; when BP<osmotic pressure, fluid returns to the capillary

Question 34

How does blood flow back to the heart?

Answer 34

1) Above the heart: veins are assisted by gravity
2) Below the heart: muscle contractions squeeze veins
3) Breathing: negative pressure pulls blood to heart

Pressure of blood from capillaries to venules is too low to propel back to heart

Question 35

What are the four components of blood?

Answer 35

1) Plasma: fluid found in blood cells
- of the 5 liters of blood humans have, 50-60% is plasma
- composed of ions, nutrients, water, plasma proteins
2) RBCs (erythrocytes): transport O2 and CO2
- Hematocrit = (% of blood that is RBCs) 42-46%
- higher in people at higher elevations since hypoxia (low O2) stimulates RVC production via erythropoietin hormone (in kidney)
3) WBCs (leukocytes): immune system cells for defense (not gas exchange)
- found in buffy coat (less than 1% blood volume)
- some transported in lymphatic system (lymphocytes)
4) Platelets: prevents excessive blood loss
- produced by bone marrow
- found in buffy coat
- work with fibrin from fibrinogen to form a clot
- fragments of a megakaryocyte (not a whole cell)

Question 36

What are some characteristics of RBCs?

Answer 36

1) Biconcave, flexible discs that can squeeze through capillaries
2) Large surface area for gas exchange
3) Generated by stem cells in bone marrow
4) Life span = 120 days (old RBCs discarded in spleen)
5) Anucleated in mammals when mature, nucleated in fish and birds
6) Hgb contains Fe –> attracts O2 for transport
7) Hgb makes it red in color

Question 37

What are the steps for blood clotting?

Answer 37

1) Damage to blood vessel lining exposes collagen fibers, platelets become sticky
2) Prothrombin (inactive enzyme from liver) –> thrombin (active form)
3) Thrombin + fibrinogen = fibrin
4) Fibrin forms a mesh that binds platelets, RBCs trapped in fibrin threads and a clot is formed + scar tissue

Question 38

What are some vascular diseases and what are their causes?

Answer 38

1) Hypertension (HTN): high BP (160/100 or higher)
- heart is working too hard
- arteries are resistant, clogged, or lack elasticity
2) Atherosclerosis: cholesterol and fat deposits, caused by HTN
- platelets stick to plaque to form thrombus (blood clot)
- hardening of arteries, endothelial lining of arteries is damaged
Risk factors: genetics, age, environmental factors, medical conditions
3) Coronary Thrombosis: blood clot forms in a coronary artery and leads to heart attack
- coronary arteries supply blood to heart muscle
- atherosclerosis reduces blood flow, leads to chest pain and shortness of breath
4) Embolism + Stroke:
- Embolus is a piece of a thrombus that breaks loose
- can cause an embolism (blockage) if lodged in a smaller blood vessel
- typically seen when arteries are narrowed by plaque
- if embolism is in brain, cells fed by that artery die and a stroke is caused

Question 39

How does plaque form?

Answer 39

(Formed at damage sites)
1) Damaged cells attract WBCs and smooth muscle cells
2) Cholesterol is deposited and plaque is fatty
3) Connective tissue is made by invading smooth muscle cells + calcium deposits, make artery wall less elastic
4) Growing plaque narrows artery and blocks blood flow
5) Platelets stick to plaque and form thrombus which blocks artery