Human Anatomy & Physiology: Heart, Blood, and Endocrine/Nervous Integration Flashcards

Comprehensive Question and Answer flashcards covering human heart anatomy and circuits, blood components and hemostasis, and homeostatic/endocrine control systems.

What are the two major cardiovascular circuits pumped by the heart, and what are their primary functions?

The pulmonary circuit (driven by the right side of the heart) performs gas exchange with the external environment at the lungs, while the systemic circuit (driven by the left side of the heart) performs gas exchange with internal body tissues.

Where is the apex of the human heart located, and in which direction does it point?

The apex of the heart points inferiorly and to the left, terminating at the 5th intercostal space.

Why is the left ventricular wall significantly thicker than the right ventricular wall?

The left ventricle must generate significantly higher pressure to pump blood through the high-resistance systemic circuit to the entire body, whereas the right ventricle only pumps blood through the short, low-resistance pulmonary circuit.

What is the primary function of the atrioventricular (AV) valves, and what are the specific names of the AV valves on each side of the heart?

AV valves prevent blood regurgitation back into the atria during ventricular contraction. The right AV valve is the tricuspid valve, and the left AV valve is the bicuspid (or mitral) valve.

What specialized intercellular junctions are present at intercalated discs in cardiac muscle tissue, and what functions do they serve?

Intercalated discs contain gap junctions (which allow ionic diffusion for rapid electrical coupling and coordinated 'all-or-none' contraction as a functional syncytium) and desmosomes (which mechanically anchor adjacent cells during contraction).

Which coronary artery occlusion is clinically referred to as the 'widow-maker'?

Occlusion of the anterior interventricular artery.

What physiological mechanism causes tissue damage during a myocardial infarction (MI)?

An occluded coronary artery starves the myocardium of oxygen (hypoxia). Because cardiac muscle relies almost exclusively on aerobic respiration, severe oxygen deprivation causes cell damage and tissue necrosis.

What are the normal values for human blood pH and average blood volume in males and females?

Blood pH is tightly regulated between $7.35$ and $7.45$. Average blood volume is $5-6\,\text{L}$ in males and $4-5\,\text{L}$ in females.

What is the most abundant protein in blood plasma, and what are its primary functions?

Albumin (accounting for approximately $58\%$ of plasma proteins), which exerts osmotic force to retain fluid inside blood vessels, contributes to blood viscosity, and transports ions, lipids, and hormones.

Why is a mature erythrocyte (RBC) not considered a 'true cell'?

Mature erythrocytes lack a nucleus, mitochondria, and ribosomes, meaning they cannot divide, perform protein synthesis, or repair cellular damage.

How do erythrocytes generate ATP, and what is their average lifespan?

Erythrocytes generate ATP exclusively through anaerobic glycolysis (ensuring they do not consume the oxygen they transport) and have an average lifespan of approximately $120\,\text{days}$.

What specific amino acid mutation in the hemoglobin beta chain causes sickle cell anemia?

A single amino acid substitution where glutamic acid (Glu) is replaced by valine (Val) in the beta chain of hemoglobin.

Which hormone stimulates erythrocyte production, which organ secretes it, and what is the stimulus for its release?

Erythropoietin (EPO) is secreted primarily by the kidneys in response to blood hypoxia (low oxygen levels). EPO acts on red bone marrow to accelerate erythropoiesis.

Why is Type O negative considered the universal red blood cell donor, while Type AB positive is the universal plasma donor?

Type O red blood cells lack A and B surface antigens (so recipient antibodies will not agglutinate them), whereas Type AB plasma lacks anti-A and anti-B antibodies (so it will not attack recipient red blood cells).

What is the relative abundance order of leukocytes in normal human blood, from most to least abundant?

Neutrophils ($50-70\%$), Lymphocytes ($25-45\%$), Monocytes ($3-8\%$), Eosinophils ($2-4\%$), and Basophils ($0.5-1\%$). Mnemonic: 'Never Let Monkeys Eat Bananas'.

What are the primary immune functions of neutrophils, eosinophils, and basophils?

Neutrophils act as phagocytic 'bacteria slayers'; eosinophils release toxic enzymes to destroy parasitic worms and participate in allergic reactions; basophils release histamine to promote inflammation and vasodilation.

What do monocytes differentiate into upon exiting the blood vessels, and what is their role?

Monocytes differentiate into macrophages in tissues, where they are voraciously phagocytic and serve an important immune signaling role as antigen-presenting cells.

From what giant bone marrow cell type are platelets produced, and what hormone regulates this process?

Platelets (thrombocytes) are cytoplasmic fragments pinched off from megakaryocytes in red bone marrow, a process regulated by the hormone thrombopoietin (produced by the liver and kidneys).

What are the three sequential steps of hemostasis following vascular injury?

1. Vascular spasm (constriction of the injured blood vessel), 2. Platelet plug formation (platelets adhere to exposed collagen fibers via von Willebrand factor), 3. Coagulation phase (blood clotting cascade).

What are the final enzymatic steps of the coagulation cascade that yield a stable blood clot?

Prothrombin activator converts prothrombin into active thrombin, which then catalyzes the conversion of soluble plasma fibrinogen into insoluble fibrin strands that weave a sticky clot mesh.

How do the nervous and endocrine systems differ regarding speed of response and duration of effect?

The nervous system uses electrical impulses and neurotransmitters for immediate, short-lived responses (milliseconds to seconds), while the endocrine system uses hormones carried in blood for slower-onset, longer-lasting responses (minutes, hours, or days).

What are the main components of a homeostatic control loop in order?

Stimulus $\rightarrow$ Receptor $\rightarrow$ Afferent Pathway $\rightarrow$ Control Center $\rightarrow$ Efferent Pathway $\rightarrow$ Effector $\rightarrow$ Response.

How does negative feedback differ from positive feedback in homeostatic regulation?

Negative feedback reverses the direction of a physiological change to restore a variable to its set-point, whereas positive feedback amplifies and reinforces the change in the same direction until a climactic event occurs.

What is the primary structural and functional difference between exocrine and endocrine glands?

Exocrine glands possess ducts that carry secretions onto an epithelial body surface or internal lumen (e.g., sweat, tears, stomach acid), whereas endocrine glands are ductless and release hormones directly into interstitial fluid and blood.

How is the hypothalamus connected to the posterior pituitary versus the anterior pituitary?

The posterior pituitary is connected via the neural Hypothalamic-Hypophyseal Tract (unmyelinated axons from hypothalamic neurons), whereas the anterior pituitary is connected via the vascular Hypophyseal Portal System (capillary networks and portal veins).

Which two hormones are synthesized in the hypothalamus and stored/released by the posterior pituitary?

Oxytocin (stimulates uterine contractions and milk let-down) and Antidiuretic Hormone (ADH/vasopressin, stimulates kidney nephrons to reabsorb water into the bloodstream, raising blood volume and pressure).

What controls the release of Thyroid Hormone (TH), and what are TH's primary physiological effects?

Thyroid-Stimulating Hormone (TSH) from the anterior pituitary stimulates TH release. TH acts on virtually all body cells to increase Basal Metabolic Rate (BMR), stimulate nutrient catabolism, and generate body heat.

How do the adrenal cortex and adrenal medulla differ in their stimuli and responses to stress?

The adrenal cortex is stimulated hormonally by ACTH during long-term stress to release Cortisol (increases blood glucose/fatty acids and suppresses immune function). The adrenal medulla is stimulated neurally by sympathetic fibers during acute stress to release Epinephrine ($80\%$) and Norepinephrine ($20\%$) to extend fight-or-flight responses.

What is the mechanism of action of beta-blocker medications in treating hypertension?

Beta-blockers act as competitive antagonists that bind to adrenergic beta receptors on myocardial cells, preventing binding of epinephrine/norepinephrine to reduce heart rate and contractile force, thereby lowering blood pressure.