Muscle Anatomy and Physiology

Review of Skeletal Muscle Anatomy

Skeletal muscle is composed of bundles of muscle fibers, each containing myofibrils made up of sarcomeres—the basic contractile units.

• Sarcomere Anatomy: The sarcomere is defined by Z-lines and contains thick (myosin) and thin (actin) filaments.

• Transverse Tubules (T-tubules): Invaginations of the sarcolemma that help transmit action potentials into the muscle fiber.

• Motor Unit: A single motor neuron and all the muscle fibers it innervates.

• Isotonic vs. Isometric Contraction: Isotonic contractions change muscle length, while isometric contractions maintain length but increase tension.

Example: Lifting a weight involves isotonic contraction; holding a weight steady involves isometric contraction.

Neural Control and Reflexes

Reflex Physiology

Reflexes are rapid, involuntary responses to stimuli, mediated by neural pathways called reflex arcs.

• Crossed Extensor Reflex: Withdrawal of one limb and extension of the opposite limb for balance.

• Integration Centers: Most reflexes are integrated in the spinal cord, but some involve higher brain centers.

• Autonomic Reflexes: Involve smooth muscle, cardiac muscle, or glands.

Factors Affecting Blood Pressure and Blood Flow

• Mean Arterial Pressure (MAP): Average pressure in arteries during one cardiac cycle.

• Parameters Associated with Increased Blood Pressure: Increased cardiac output, peripheral resistance, blood volume.

• Factors Affecting Blood Flow to Tissues: Vessel diameter, blood viscosity, pressure gradients.

Formula:

Cardiovascular Physiology

Cardiac Output and Regulation

• Frank-Starling Law: The strength of the heart's contraction increases with greater filling (preload).

• Perfusion: The process of delivering blood to capillary beds in tissue.

• Endothelium: The inner lining of blood vessels, crucial for vascular health.

• ECG (Electrocardiogram): A recording of the electrical activity of the heart.

Heart Structures

• Intercalated Discs: Specialized connections between cardiac muscle cells for synchronized contraction.

• Chordae Tendineae: Tendinous cords that anchor heart valves.

• Artery vs. Veins: Arteries carry blood away from the heart; veins return blood to the heart.

• Platelets: Cell fragments involved in blood clotting.

Blood and Immune System

Blood Physiology

• Fibrinolysis: The breakdown of fibrin in blood clots.

• Erythropoietin: Hormone stimulating red blood cell production.

• Plasma Proteins: Albumin, globulins, and fibrinogen are key proteins in plasma.

Immune Response

• Cells of the Immune Response: Includes lymphocytes, neutrophils, monocytes, etc.

• Functions: Innate immunity (nonspecific) vs. adaptive immunity (specific); cell-mediated vs. humoral immunity.

• Immunoglobulins: Five types (IgG, IgA, IgM, IgD, IgE) with distinct functions.

• Allergy Response: Hypersensitivity reaction involving IgE and mast cells.

• Chemotaxis: Movement of immune cells toward chemical signals.

• Opsonization: Marking pathogens for phagocytosis.

Respiratory Physiology

Gas Exchange and Regulation

• Type I and Type II Alveolar Cells: Type I cells form the alveolar wall; Type II cells secrete surfactant.

• Surfactant: Reduces surface tension in alveoli, preventing collapse.

• Pulmonary Ventilation: Movement of air into and out of the lungs.

• Dalton's Law: Total pressure of a gas mixture equals the sum of partial pressures of individual gases.

• Boyle's Law: Pressure and volume of a gas are inversely related at constant temperature.

Formulas:

(Boyle's Law)

(Dalton's Law)

Renal Physiology

Functions of the Kidney

• Filtration: Removal of waste from blood.

• Juxtaglomerular Cells: Regulate blood pressure and filtration rate.

• Location of Primary Osmoreceptors: Hypothalamus monitors blood osmolarity.

• RAAS (Renin-Angiotensin-Aldosterone System): Hormonal system regulating blood pressure and fluid balance.

• ADH (Antidiuretic Hormone): Promotes water reabsorption in kidneys.

Digestive System

Functions and Enzymes

• Cells of the Stomach: Parietal cells (secrete HCl), chief cells (secrete pepsinogen).

• Functions of Large Intestine: Water absorption, feces formation.

• Cells of Pancreas and Their Products: Alpha cells (glucagon), beta cells (insulin).

• Digestive Enzymes: Amylases (carbohydrate digestion), lipases (fat digestion), proteases (protein digestion).

• Fat Digestion/Absorption: Bile emulsifies fats; absorption occurs in small intestine.

• Pernicious Anemia: Caused by lack of intrinsic factor, leading to poor vitamin B12 absorption.

Inflammation and Immune Disorders

• Inflammation: Tissue response to injury or infection, characterized by redness, heat, swelling, and pain.

• Acid-Base Disorders: Vomiting (loss of acid), diarrhea (loss of base), hyperventilation (respiratory alkalosis), emphysema (respiratory acidosis).

Reproductive System and Development

Male and Female Reproductive Anatomy

• Review of Anatomy: Includes structures such as testes, ovaries, uterus, and associated ducts.

• Meiosis: Cell division producing gametes with half the chromosome number.

• SRY Gene: Sex-determining region Y, initiates male development.

• Development of Embryo: Fertilization, cleavage, gastrulation, organogenesis.

• Mullerian Ducts: Develop into female reproductive tract.

• Wolffian Ducts: Develop into male reproductive tract.

• Role of FSH/LH: Follicle-stimulating hormone and luteinizing hormone regulate gametogenesis and hormone production.

• Menstrual Cycle: Ovarian and uterine phases; regulated by hormones.

• Spermatogenesis: Production of sperm in seminiferous tubules.

• Spermiogenesis: Final maturation of sperm.

• Interstitial (Leydig) Cells: Produce testosterone in testes.

• Sertoli Cells: Support and nourish developing sperm.

Summary Table: Key Cell Types and Functions

Additional info: Some topics were expanded for clarity and completeness, including definitions, examples, and formulas. This guide covers all major areas listed in the original notes, grouped by physiological system for effective exam preparation.