PHYSIO EXAM 3 STUDY GUIDE

Vocabulary practice flashcards covering core concepts from the Endocrine, Muscle Physiology, and Respiratory Physiology lecture review sheets.

Hormones

Chemical messengers secreted by endocrine glands directly into the bloodstream that regulate specific physiological activities and maintain homeostasis in target cells.

Steroid-based Hormones

Lipid-soluble hormones derived from cholesterol that diffuse directly across the phospholipid bilayer of target cell membranes to bind to intracellular or nuclear receptors.

Protein-based and Biogenic Amine Hormones

Water-soluble hormones (composed of amino acids or peptides) that cannot cross the plasma membrane; they bind to extracellular cell-surface receptors and initiate intracellular second-messenger cascades.

Anterior Pituitary Hormones

Six peptide hormones secreted by this gland: Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), Growth Hormone (GH), and Prolactin (PRL).

Thymosin

A hormone secreted by the thymus gland that plays a crucial role in immune development by promoting the maturation and differentiation of T-lymphocytes.

Thyroid Gland Hormones

Thyroxine ($T_4$) and Triiodothyronine ($T_3$)—Metabolic and homeostatic regulators secreted by follicular cells to regulate basal metabolic rate

Calcitonin— secreted by parafollicular (C) cells to lower blood calcium levels

Adrenal Gland Hormones

Hormones produced by the cortex (mineralocorticoids like aldosterone, glucocorticoids like cortisol, and androgens) and the medulla (epinephrine and norepinephrine), which regulate electrolytes, stress responses, and sympathetic activity.

Antagonistic Hormone Interaction

A homeostatic feedback mechanism where two hormones exert opposing actions

Spermatogenesis

male gamete (sperm) production occurring within the seminiferous tubules of the testes, supported by Sertoli (sustentacular) cells and stimulated by testosterone from Leydig (interstitial) cells.

Diabetes Insipidus

A metabolic condition caused by a deficiency in antidiuretic hormone (ADH) secretion or lack of renal response to ADH, resulting in excessive dilute urination and thirst without hyperglycemia, distinguishing it from diabetes mellitus.

Three "P's" of Diabetes

The hallmark clinical manifestations of _____ mellitus: Polyuria (excessive urination), Polydipsia (excessive thirst), and Polyphagia (excessive hunger).

Prolactin

reproductive hormone that stimulates milk synthesis and secretion in mammary glands

Ovarian Hormones

Estrogen and progesterone, which regulate the female reproductive cycle, secondary sex characteristics, endometrial growth, and maintenance of pregnancy.

Epimysium

encases the entire muscle and consists of dense connective tissue.

Fascicle

A distinct bundle of skeletal muscle fibers segregated from adjacent bundles by a connective tissue layer called the perimysium.

Sarcomere

The fundamental microscopic contractile unit of striated muscle, bounded by two successive Z-discs and consisting of overlapping thick (myosin) and thin (actin) myofilaments organized into A bands, I bands, H zones, and M lines.

Actin

primary contractile myofilament that forms thin filaments with specific binding sites for cross-bridge formation

Tropomyosin

Regulatory protein on thin filaments that blocks myosin-binding sites on actin at rest

Motor Unit

consists of a single somatic motor neuron and all the individual skeletal muscle fibers it innervates.

T-Tubule (Transverse Tubule)

Invaginations of the sarcolemma that project deep into the interior of a muscle fiber, allowing action potentials to rapidly propagate inward toward the sarcoplasmic reticulum.

Sarcoplasmic Reticulum

The specialized smooth endoplasmic reticulum of muscle fibers that stores and regulates $Ca^{2+}$;

Acetylcholine (ACh)

The specific neurotransmitter released from the somatic motor axon terminal into the synaptic cleft of the neuromuscular junction to trigger depolarization of the motor end plate.

Role and Fate of $Ca^{2+}$ in Muscle Physiology

1. Intracellular $Ca^{2+}$ binds troponin to initiate cross-bridge cycling
   
   

2. after action potentials cease, $Ca^{2+}$ is actively pumped back into the sarcoplasmic reticulum via primary active transport ($Ca^{2+}$-ATPase) to allow relaxation.

Function of ATP in Muscle Contraction

-ATP energizes myosin head cocking via hydrolysis
-provides the energy for the power stroke
-binds to myosin to cause detachment from actin
-powers active transport pumps ($Ca^{2+}$-ATPase and $Na^+/K^+$ pump).

Sliding Filament Theory

The mechanism of muscle contraction stating that thin actin filaments slide past thick myosin filaments toward the M line, shortening the sarcomere, I band, and H zone without altering individual filament lengths.

DHP and Ryanodine Receptors

Coupled receptors involved in excitation-contraction

AChE (Acetylcholinesterase)

An enzyme located in the synaptic cleft of the neuromuscular junction that rapidly degrades acetylcholine into acetate and choline, halting continuous muscle excitation.

Isotonic Contractions

contractions that involve movement; muscle tension remains constant as the muscle changes length (shortening or lengthening)

Conductive Division

carries, warms, and filters air from the nose to terminal bronchioles without gas exchange

Type I Alveolar Cells

thin simple squamous cells that form the structural gas exchange barrier in the alveoli of the lungs, facilitating the diffusion of oxygen and carbon dioxide.

Dust Cells

Alveolar macrophages located in the alveoli that phagocytize particulate matter, inhaled debris, and infectious pathogens to keep the lungs clean.

Muscles of Respiration

Quiet inspiration—diaphragm and external intercostals

Forced inspiration—accessory muscles (scalenes, sternocleidomastoid, pectoralis minor)

Forced expiration—internal intercostals and abdominal muscles

Pulmonary Exchange

type of exchange (external respiration) that involves $O_2$ loading into blood and $CO_2$ unloading into alveoli

Carbonic Anhydrase

The red blood cell enzyme that catalyzes the reversible conversion of carbon dioxide and water into carbonic acid: $CO_2 + H_2O \rightleftharpoons H_2CO_3$, which dissociates into $H^+$ and bicarbonate ($HCO_3^-$).

Hypoxia

A state of insufficient tissue oxygenation ($\text{low } O_2$), which triggers hyperventilation that often drives down blood $CO_2$ levels and raises blood pH (respiratory alkalosis).

Hypercapnia

An abnormal elevation of carbon dioxide levels in the blood ($\text{high } CO_2$), which promotes carbonic acid formation, increases $H^+$ concentration, and lowers blood pH (respiratory acidosis).

Chemoreceptors (Blood pH Monitors)

Sensory receptors that monitor arterial $pH$, $CO_2$, and $O_2$: central receptors in the medulla oblongata detect brainstem extracellular $pH$, and peripheral receptors in the carotid and aortic bodies monitor arterial blood

Obstructive Disorders

disorders such as asthma & COPD that are characterized by increased airway resistance limiting expiratory airflow

Eupnea

normal, quiet breathing at rest

Apnea

temporary cessation of breathing

Type II Alveolar Cells

cuboidal cells that secrete pulmonary surfactant to lower surface tension and prevent alveolar collapse. also serving as stem cells to repair the alveolar epithelium.

systemic gas exchange

(internal respiration) type of exchange that involves $O_2$ unloading into body tissues and $CO_2$ loading into systemic capillaries.

Restrictive Disorders

disorders such as pulmonary fibrosis that are characterized by reduced lung compliance and decreased vital capacity

Dyspnea

labored, difficult, or painful breathing

Tachypnea

abnormally rapid breathing rate

Oxytocin

distinct reproductive hormone that stimulates uterine smooth muscle contraction during labor and milk ejection ("let-down") during nursing

Perimysium

wraps bundles of muscle fibers (fascicles)

Endomysium

surrounds individual muscle fibers

Troponin

Regulatory protein on thin filaments that binds calcium ions ($Ca^{2+}$) to induce a shift that exposes those binding sites

Myosin

forms thick filaments with globular heads possessing ATPase activity

Respiratory Division

encompasses respiratory bronchioles, alveolar ducts, and alveoli where gas exchange of oxygen and carbon dioxide occurs

Isometric Contractions

contractions that involve no movement; muscle tension increases without changing its length

Kussmaul respiration

deep, rapid, hyperventilatory pattern triggered as a compensatory response to severe metabolic acidosis

Give an example of Antagonistic Hormone Interaction between Insulin and Glucagon

Insulin decreases blood glucose by promoting cellular uptake and glycogen synthesis, while glucagon increases blood glucose by stimulating glycogenolysis and gluconeogenesis.

DHP (dihydropyridine) receptors

voltage-sensitive receptors in the T-tubule that mechanically open calcium-release channels (ryanodine receptors) in the terminal cisternae during excitation-contraction coupling

Ryanodine receptors

calcium-release channels in the terminal cisternae that are mechanically opened by DHP receptors during excitation-contraction coupling

Terminal cisternae

enlarged end-sacs of the smooth endoplasmic reticulum that flank T-tubules to form triads and release $Ca^{2+}$ upon depolarization and trigger muscle contraction