more circulatory system

What are the three metabolic requirements for erythrocyte production?

Iron (Fe), B vitamins (folic acid and riboflavin), and amino acids for protein synthesis.

Describe the destruction process of the heme group (minus the iron).

Macrophages convert heme into a greenish pigment called biliverdin, which then becomes the yellowish bilirubin. Bilirubin is transported by albumin to the liver and eventually excreted as bile.

What happens to the iron (Fe++) when an erythrocyte is destroyed?

It is removed and transported by a protein called transferrin to the liver or spleen, where it is stored bound to ferritin or hemosiderin.

What is Physiologic Jaundice in newborns?

A condition where a baby's liver cannot process the bilirubin fast enough as fetal hemoglobin is replaced by adult hemoglobin.

Which leukocyte is the most numerous and acts as the 'first responder' to bacterial infections?

Neutrophils, making up 50-70% of all white blood cells.

What are the functions of Eosinophils?

They phagocytize antigen-antibody complexes and allergens, and they release chemicals to attack parasitic worms.

Define Diapedesis and Chemotaxis in relation to leukocytes.

Diapedesis is the process of WBCs squeezing between endothelial cells to enter tissues. Chemotaxis is the movement of WBCs toward an infection site in response to molecules released by damaged cells or pathogens.

Distinguish between T-lymphocytes and B-lymphocytes.

T-cells directly attack foreign or virus-infected cells, while B-cells become plasma cells that produce antibodies.

Why is the heart considered a 'functional syncytium'?

Because gap junctions within intercalated discs allow action potentials to move continuously between cells, ensuring the entire chamber contracts as a single unit.

What is the role of Desmosomes in cardiac muscle?

They act as mechanical junctions (protein filaments) that prevent cardiac cells from pulling apart during the stress of contraction.

How does cardiac muscle metabolism differ from skeletal muscle?

It relies almost exclusively on aerobic respiration, with mitochondria making up 25% of cell volume (compared to 2% in skeletal muscle). It can also use diverse fuels like fatty acids, glucose, and even lactate.

What is Myoglobin and when is it used by the heart?

It is a globular protein that binds oxygen when the heart muscle is at rest to provide a reserve for activity.

Contrast Elastic Arteries and Muscular Arteries.

Elastic arteries (e.g., Aorta) have high elastic fiber content to conduct blood. Muscular arteries have a thicker tunica media of smooth muscle to distribute blood to specific organs.

What is the Myogenic Response in local blood flow?

It is the reflexive contraction or relaxation of smooth muscle in a vessel wall in response to changes in stretch to keep blood flow constant.

Explain Autoregulation of blood flow.

Tissues regulate their own flow based on metabolic needs; a decline in O2 or an increase in CO2/lactate acts as a vasodilator to increase perfusion.

What are the three types of Capillaries from least to most permeable?

1. Continuous (found in skin/muscle), 2. Fenestrated (found in kidneys/intestines), 3. Sinusoids (found in liver/bone marrow).

Describe the RAAS Pathway (Renin-Angiotensin System).

Low BP triggers the kidney to release Renin, which converts angiotensinogen to Angiotensin I; this is converted by ACE into Angiotensin II, a powerful vasoconstrictor.

How do Aldosterone and Antidiuretic Hormone (ADH) differ in action?

Aldosterone increases Na+ and water absorption in the kidney. ADH primarily increases water reabsorption and stimulates the thirst center to increase blood volume.

What is Atrial Natriuretic Peptide (ANP)?

A hormone released by the heart atria in response to high blood volume that stimulates vasodilation and increases urine output to lower blood pressure.

Define Vagal Tone.

The continuous parasympathetic stimulation of the SA node by the vagus nerve, which slows the inherent heart rate from 100 bpm to a resting rate of about 75 bpm.