Cardiovascular System, Lecture 2

Question 1

Erythrocytes

Answer 1

• live ~120 days; then need to be replaced (longer than platelets) (constantly changing them on a day to day basis)
• bioconcave disc (concave on both sides); no nucleus or other organelles in mature cells -> gases can move around easier and hemoglobin in the main content inside
• contain large amounts of hemoglobin (~250 million Hb per erythrocyte)
  Hb struture:
• 4 globin chains (2 alpha/2 beta)
• 4 heme groups (each heme with iron ion in core)
  can bind:
• oxygen -> oxyhemoglobin (what it becomes when it binds
• carbon dioxide -> carbominohemoglobin (binds to the globin part not the heme part)
  carbon monoxide -> carboxyhemoglobin (binds to the disc part of hemoglobin)
• hydrogen -> deoxyhemoglobin (hydrogen binds to disc)

Question 2

Homeostasis

Answer 2

• physiological variables in a state of dynamic constancy; not static (bury within some level of tolerance; never fixed)
• maintain within a set range over time (which ever way it goes, detect it and move it the other way to normalize it)
• negative feedback - move in opposite direction to original change
• controlled variable is what is being monitored by receptors, stimulus then disrupts homeostasis by increasing or decreasing by which the receptors will detect and send action potentials or signals to a controlled center that will respond by sending an effector to give a response to bring it back to to homeostasis by increasing or decreasing depending on what has happened

Question 3

Erythrocytes (2)

Answer 3

erythropoiesis - erythrocyte production
~ 15 day process start to finish, cells continuously being formed
- a stimulus disrupts oxygen delivery to kidneys (controlled variable), so the receptors (kidney cells) detect low oxygen levels increasing EPO secretion into blood by which the control center will lead proerythroblasts as they mature quickly into reticulocytes that eventually mature into erythrocytes in blood stream in 1 to 2 days, the effector now has a larger number of erythrocytes in circulation which will lead to the response of increased oxygen carrying capacity to counter initial hypoxia; more erythrocytes - more Hb to bind to oxygen - greater oxygen delivery which will eventually return it to homeostasis

Question 4

Hematocrit (Hct)

Answer 4

spin blood sample (blood volume) in a centrifuge to separate into:
- plasma volume (55%)
- “buffy coat” volume - leukocytes and platelets
- erythrocyte volume (hematocrit = 45%)
Hct: percentage of blood volume that is erythrocyte volume
- average ~42-47%
- “buffy coat” volume is quite small and usually ignored in Hct determination

Question 5

Hematocrit (Hct) - anemia

Answer 5

• same blood volume
• reduced erythrocytes, hematocrit
• lower oxygen carrying capacity can lead to hypoxia issues (lower oxygen -> lower red blood cells)
  source:
  hemorrhagic - blood loss (wounds/ulcers/menstruation)
  nutritional - lack elements for erythrocyte formation (iron-deficient; low iron levels)
• developmental - damage in critical area (aplastic; red bone marrow)
• hemolytic - erythrocytes destroyed (sickle-cell)

Question 6

Hematocrit - polycythemia

Answer 6

• same blood volume
• increased erythrocytes, Hct (elevated level of red blood cells equals elevated hematocrit)
• higher oxygen carrying capacity can lead to blood viscosity/pressure issues
• blood becomes thicker with higher level of red blood cells (less liquid component, blood tends to get a syrup-like consistency), leading more pressure needed to push it around with blood pressure having to rise up (body has to work harder)
  source:
  primary - bone marrow tumor
  secondary - some altitude living cultures, heart and lung diseae
  induced - athletics

Question 7

Hematocrit - “relative” polycythemia

Answer 7

• reduced blood volume, plasma volume
• same amount of erythrocytes
• increased hematocrit
• red blood cells are the same but the blood volume and plasma are quite a bit less (plasma volume went down) - losing the fluid part of it
  source:
• dehydration; “making weight” sports (sacrificing plasma fluid to provide it to other areas of the body & dehydrate themselves to reach a certain weight)
• not a “true” polycythemia as there is no increase in erythrocytes