Physiology

• Formed elements

  Erythrocytes/RBC, leukocytes/WBC, and platelets
• Hemoglobin formation

  1. Develops in cells in the bone marrow that become red blood cells

  2. When red cells die, hemoglobin is broken up

  3. Iron from the heme binds to protein transferrin and transported through the bloodstream

  4. Iron is stored attached to ferritin

  5. Vitamin B12 helps in the process
• Factors that decrease oxygenation

  Less red blood cells will be produced
• Erythropoiesis

  1. Hematopoietic stem cells divide to produce myeloid stem cells

  2. Myeloid stem cells transform into pro-erythroblasts

  3. Pro-erythroblasts give rise to erythroblasts

  4. Erythroblasts synthesize hemoglobin and transform to normoblasts

  5. Normoblast ejects organelles, becoming a reticulocyte

  6. Reticulocytes are released into the bloodstream and become erythrocytes
• Blood coagulation

  1. Prothrombin is converted to thrombin by prothrombinase

  2. Thrombin catalyzes the conversion of fibrinogen to fibrin

  3. Activated factor XIII catalyzes the polymerization of crosslinked fibrin
• Frank Starling law of the heart

  • Relationship between stroke volume and end diastolic volume
  • Stroke volume increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant
  • Larger volume of blood stretches cardiac muscle, leading to an increase in the force of contraction
  • Allows cardiac output to be synchronized with venous return, arterial blood supply and humoral length, without depending upon external regulation
• Electrocardiogram

  • Records the excitation of the heart
  • P wave reflects atrial depolarization
  • QRS complex reflects ventricular depolarization
  • T wave reflects ventricular repolarization
• Norepinephrine stimulating cardiac contractility

  1. Binds to B1-adrenoreceptor on cardiac muscle fibers

  2. Activates G protein, which activates adenylate cyclase, producing cAMP

  3. cAMP activates protein kinase, increasing cytosolic Ca2+

  4. Increased Ca2+ increases contractility
• Events at onset of ventricular systole

  1. Filled ventricles begin to contract

  2. Pressure in ventricles increases above atria, forcing AV valves to shut

  3. Shutting of AV valves produces first heart sound

  4. Semilunar valves not yet open, no blood can enter or leave heart
• Physiological response to decreased blood sodium concentration

  1. Low sodium means no constriction in blood vessels, leading to low blood pressure

  2. Low blood pressure activates RAAS

  3. Kidney releases renin, which converts angiotensinogen to angiotensin 1

  4. Angiotensin 1 converted to angiotensin 2

  5. Angiotensin 2 stimulates aldosterone and antidiuretic hormone release

  6. Aldosterone increases sodium and water reabsorption

  7. Antidiuretic hormone stimulates water reabsorption