second class

Introduction

  • Speaker shares personal experience of taking a long afternoon nap, indicating a good day.

  • Mentions this is the second session of a course, indicating a slow start for the first few weeks.

Course Structure

  • Overview of the schedule is given for the day, access to this can be found on the course homepage.

  • Reminder that students were to finish signing their technology in the laboratory.

Assignments

  • Update on homework status: Most students have completed it, though some are still on the second attempt or have not started.

  • Homework is due today at 11:59 PM Eastern Time.

    • Encouragement to not wait too long if still working on it.

    • Instructions on resource usage are emphasized: Students can reference course notes while completing assignments.

Lecture Content

Review of Cardiovascular System

  • Opens questions regarding numbers and percentages related to the cardiovascular system.

  • If someone pretends to be a chef building blood, they need:

    • Components:

    1. Plasma

    2. Formed Elements.

    • Formed elements include:

    • Erythrocytes (Red blood cells)

    • Leukocytes (White blood cells)

    • Thrombocytes (Platelets)

Key Cellular Components

  • Erythrocyte: red blood cells, specialized cells that carry oxygen throughout the body.

  • Leukocyte: white blood cells, involved in the immune response to protect against infections.

  • Thrombocyte: platelets, responsible for blood clotting.

  • Erythrocytes are derived from precursor cells called proerythroblasts.

Blood Cell Preparation Stats

  • In a healthy adult, there are approximately:

    • Total Blood Cells: 5,000 to 10,000 cells/microliter.

    • Red Blood Cell Count: 140,000 to 400,000 per microliter for thrombocytes.

Gas Transport by Blood

  • Oxygen Transport:

    • 98.5% of oxygen in the blood is carried by hemoglobin within red blood cells.

    • 3.5% is dissolved in plasma.

  • Carbon Dioxide Transport:

    • 23% is transported by hemoglobin.

    • 7% is dissolved in plasma; 70% exists as bicarbonate ions (HCO3-).

Hematocrit Levels

  • Average blood composition in a healthy adult is approximately:

    • Plasma: 55%

    • Red Blood Cells: 45% (Hematocrit)

  • Hematocrit ranges:

    • Men: 40-54%

    • Women: 38-46%

    • Discussion of why men typically have higher hematocrit due to physiological factors like menstruation.

Factors Influencing Hematocrit

  • Key factors include:

    • Menstruation: women lose blood monthly which can lead to lower overall red blood cell counts.

    • Testosterone Levels: Higher in males, stimulates erythropoiesis (production of red blood cells).

    • Testosterone promotes the conversion of proerythroblasts to reticulocytes.

Erythropoiesis Process

  • Process of red blood cell formation is called erythropoiesis.

    1. Stem Cells: Known as pluripotent stem cells in red bone marrow that can differentiate into different blood cells.

    2. Proerythroblast: Early precursor in the development of erythrocytes.

    3. Reticulocyte: Immature red blood cell that will lose its remaining organelles before maturing in the bloodstream.

  • Hemoglobin production is critical; each erythrocyte contains roughly 80-300 million hemoglobin molecules.

Roles of Kidneys in Erythropoiesis

  • Erythropoietin (EPO): Hormone secreted by kidneys in response to low oxygen levels (hypoxia), stimulating the production of red blood cells.

  • Mechanism:

  1. Receptors in kidneys detect hypoxia.

  2. Signal sent to control center (brain) which sends out erythropoietin in response.

  • This demonstrates a negative feedback system that maintains hematocrit levels within a healthy range.

Discussion of Feedback Systems

  • Feedback systems are essential for maintaining homeostasis in the body.

  • Components include:

    • Receptors: Detect changes (e.g., changes in temperature or oxygen levels)

    • Control Center: Processes signals and decides on an action

    • Effectors: Act based on control center directives (e.g., sweat glands cooling body down)

  • Positive feedback: Enhances change, e.g., during childbirth.

  • Negative feedback: Counteracts change, e.g., temperature regulation.

Conclusion

  • Feedback systems and erythropoiesis process are critical for maintaining homeostasis and ensuring adequate oxygen delivery by adjusting red blood cell count based on physiological demands.

Next Steps in Class

  • Overview of upcoming labs and specific actions required from students.

  • Reinforcement of importance of patient safety and comfort during interactive lab exercises.

  • Announcement regarding participation and expectation for video reviews to prepare for hands-on lab activities.

Practical Considerations for Erythropoiesis

  • Passive understanding through listening will not suffice; active engagement with materials through writing or drawing enhances learning and memory retention.

  • Instructor emphasizes the importance of utilizing various resources, including group studies and written notes, for understanding complex physiological concepts.