Anatomy and Physiology II: Blood, Endocrine System, and Autonomic Nervous System

Vocabulary practice flashcards covering blood composition and hematopoiesis, endocrine glands and chemical signaling pathways, and the structure and pharmacology of the autonomic nervous system.

Hematocrit

The percentage of red blood cells in a blood sample, also referred to as packed cell volume (PCV).

Buffy Coat

The thin intermediate layer in a centrifuged blood sample that contains white blood cells and platelets.

Albumin

The most abundant plasma protein, comprising $54\%$ of total plasma protein content.

Hemopoiesis

The process of producing blood cellular elements, taking place primarily in the red bone marrow in adults.

Erythropoietin (EPO)

A hemopoietic growth factor secreted by the kidneys that stimulates red blood cell production.

Thrombopoietin

A glycoprotein hormone produced by the liver and kidneys that triggers the development of platelets.

Spectrin

A flexible cytoskeletal protein in erythrocytes that allows red blood cells to bend and navigate through narrow capillary beds.

Reticulocyte

An immature, non-nucleated erythrocyte released into the bloodstream that lacks mitochondria and endoplasmic reticulum.

Hemoglobin

A large protein molecule in erythrocytes consisting of $4$ globin proteins and $4$ heme groups, each containing an iron ion ($\text{Fe}^{2+}$) capable of binding one oxygen molecule.

Sickle Cell Disease

A genetic disorder characterized by an abnormal hemoglobin type that alters erythrocyte shape, reducing oxygen delivery and cell flexibility.

Polycythemia

A blood disorder marked by an elevated erythrocyte count, which increases blood viscosity and strains cardiac pumping.

Diapedesis

The process by which leukocytes squeeze between adjacent endothelial cells to exit blood vessels into tissues.

Positive Chemotaxis

The directed movement of leukocytes toward higher concentrations of specific chemical signals released by damaged or infected cells.

Neutrophils

The most abundant leukocytes ($50\text{--}70\%$ of WBCs), functioning as phagocytes that release lysozyme and defensins.

Eosinophils

Granular leukocytes representing $2\text{--}4\%$ of WBCs that produce antihistamines and combat parasitic worms.

Basophils

The rarest granular leukocytes ($<1\%$ of WBCs), which promote inflammation by releasing histamine and heparin.

Megakaryocyte

A large bone marrow cell that pinches off cellular fragments to yield $2000\text{--}3000$ platelets before being consumed by macrophages.

Hemostasis

The physiological process by which the body stops bleeding from a damaged blood vessel through vascular spasm, platelet plug formation, and coagulation.

Fibrinolysis

The gradual dissolution of a blood clot driven by Factor XII, bradykinin release, and fibrin breakdown.

Embolus

A piece of a thrombus or blood clot that breaks free from a vessel wall and circulates through the bloodstream.

Agglutination

The clumping together of erythrocytes caused by antibodies binding to foreign cell-surface antigens during a mismatched blood transfusion.

Autocrine Signaling

A mode of chemical communication in which a cell secretes a hormone or chemical that binds to receptors on its own surface.

Paracrine Signaling

Local chemical signaling in which a secreted substance affects nearby target cells in the immediate environment, such as histamine release during tissue injury.

First Messenger

A hormone that binds to an extracellular cell-membrane receptor, initiating intracellular signal transduction pathways.

Cyclic Adenosine Monophosphate (cAMP)

A major second messenger molecule generated from ATP by adenylyl cyclase that activates intracellular protein kinases.

Upregulation

The process by which target cells increase their number of hormone receptors in response to low hormone concentrations, raising tissue sensitivity.

Downregulation

The process by which target cells decrease their number of hormone receptors in response to chronically elevated hormone levels, reducing tissue sensitivity.

Antidiuretic Hormone (ADH)

A peptide hormone stored and released by the posterior pituitary in response to high blood osmolarity, increasing renal water reabsorption.

Oxytocin

A posterior pituitary peptide hormone that stimulates uterine muscle contractions and cervical dilatation during labor via positive feedback.

Hypophyseal Portal System

A specialized capillary network that carries regulatory releasing and inhibiting hormones directly from the hypothalamus to the anterior pituitary.

Growth Hormone (GH)

An anterior pituitary protein hormone (somatotropin) that stimulates tissue growth, protein synthesis, lipolysis, and glucose regulation.

Colloid

The central fluid-filled material inside thyroid follicles where thyroid hormones are synthesized and stored.

Calcitonin

A peptide hormone secreted by thyroid C cells that lowers blood $\text{Ca}^{2+}$ levels by inhibiting osteoclasts and increasing osteoblast activity.

Parathyroid Hormone (PTH)

A peptide hormone secreted by chief cells of the parathyroid glands that increases blood $\text{Ca}^{2+}$ levels by inhibiting osteoblasts and stimulating calcitriol synthesis.

Zona Glomerulosa

The outermost layer of the adrenal cortex, responsible for secreting mineralocorticoids like aldosterone.

Zona Fasciculata

The thick middle layer of the adrenal cortex that produces glucocorticoids such as cortisol.

Zona Reticularis

The deepest layer of the adrenal cortex that releases small quantities of sex steroid precursors known as androgens.

Cushing's Disease

A metabolic disorder caused by hypersecretion of cortisol, leading to elevated blood glucose, rapid weight gain, moon face, and a buffalo hump.

Addison's Disease

An adrenal endocrine disease caused by hyposecretion of corticosteroid hormones, resulting in low blood glucose, hyponatremia, fatigue, and salty food cravings.

Melatonin

An amine hormone secreted by the pineal gland in response to darkness that regulates circadian rhythms and sleep cycles.

Glucagon

A protein hormone secreted by pancreatic alpha cells that raises blood glucose levels by triggering glycogenolysis, gluconeogenesis, and lipolysis.

Insulin

A protein hormone secreted by pancreatic beta cells that lowers blood glucose levels by facilitating cellular glucose uptake and glycogenesis.

Atrial Natriuretic Peptide (ANP)

A hormone produced by cardiac muscle cells in response to high blood volume that decreases blood pressure and promotes renal excretion of $\text{Na}^+$.

Leptin

A peptide hormone produced by adipose tissue that acts on brain receptors to produce satiety signals after meal intake.

Thoracolumbar Outflow

The structural anatomical arrangement of the sympathetic division, originating in the lateral horns of thoracic T1 through lumbar L2 spinal segments.

Craniosacral Outflow

The structural anatomical arrangement of the parasympathetic division, originating from nuclei in the brainstem and lateral horn segments of the sacral spinal cord.

Preganglionic Fiber

An autonomic neuron whose axon extends from a central cell body in the CNS to an autonomic ganglion; it is short and myelinated in the sympathetic system.

Postganglionic Fiber

An autonomic neuron whose axon extends from an autonomic ganglion cell body to the visceral target organ; it is long and unmyelinated in the sympathetic system.

Terminal Ganglia

Parasympathetic autonomic ganglia located near or adjacent to the wall of a target effector organ.

Intramural Ganglia

Parasympathetic autonomic ganglia located directly inside the tissue wall of a target organ.

Autonomic Varicosities

Chains of neurotransmitter-filled swellings along postganglionic autonomic axons that diffuse neurotransmitters across broad areas of smooth muscle cells.

Cholinergic Synapse

A synapse that synthesizes and releases acetylcholine onto either nicotinic or muscarinic receptors.

Adrenergic Synapse

A synapse that releases norepinephrine or epinephrine to act upon alpha or beta adrenergic receptors.

Referred Pain

The sensation of visceral pain perceived at a superficial or distant body site due to shared spinal cord neural pathways.

Short Reflex

A visceral reflex arc that bypasses the central nervous system entirely, involving local sensory input and motor output integration within autonomic ganglia.

Long Reflex

A visceral reflex arc that routes afferent sensory information into the spinal cord or brain stem before sending efferent motor signals to effector organs.

Sympathomimetic Drug

A class of pharmaceutical compounds, such as phenylephrine or cocaine, that stimulate adrenergic receptors or enhance norepinephrine action to increase sympathetic tone.

Sympatholytic Drug

A pharmaceutical compound, such as a beta-blocker, that acts as an antagonist at adrenergic receptors to decrease sympathetic tone.

Parasympathomimetic Drug

A drug, such as pilocarpine, that acts as a muscarinic receptor agonist to enhance parasympathetic response.

Anticholinergic Drug

A drug, such as atropine, that acts as a muscarinic antagonist to block acetylcholine binding and suppress parasympathetic activity.