MCAT Physiology

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MCAT Physiology
2015-06-25 23:22:09

MCAT review
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  1. Bicarbonate buffer system
    HCl in blood pushed H2CO3 ↔ H+ + HCO3- to the left

    More H2CO3 drives CO2 + H2O↔H2CO3 to the left

    More CO2 increases respiratory rate so more CO2 is discharged through lungs

    NaOH drives Na+ + OH- + H2CO3 ↔ NaHCO3 + H2O to the right

    Decreased H2CO3 drives CO2 + H2O↔H2CO3 to the right

    Decreased CO2 reduces respiratory rate and lungs decrease discharge of CO2
  2. Respiratory Tract
    • Air enters tract through nose and mouth (warm+moisten air)
    • Mucus and hair in naves, cilia in lungs, or phagocytosis get rid of large particles
    • Air passes through nasopharynx and oropharynx
    • Passes through larynx into trachea (held open by cartilaginous rings)
    • Trachea branches into left and right bronchus to bronchioles
    • At ends of bronchioles are alveoli, which are surrounded by pulmonary capillaries
  3. Inspiration
    Respiratory center in medulla oblongata sends signal to phrenic nerve to diaphragm to contract

    Contraction causes flattening and negative pressure between lungs and diaphragm

    Lungs expand to create negative pressure, which causes an inflow of air

    Intercostal muscles contract to expand chest cavity
  4. Lymphatic system
    Lymph vessels meet to form thoracic and right lymphatic ductm that drain into venous circulation via jugular and subclavian veins

    Vessels carry lymph (excess intersisital fluid) and lacteals collect fats by absorbing chylomircons in the small intestine

    Lymph nodes are swellings along the vessels with lymphocytes that removes foreign particles from lymph
  5. Blood flow
    left atrium through bicuspid valve → left ventricle through aortic valve → aorta to arteries → arterioles → capillaries → vessels → venules → veins → superior/inferior vena cava → right atrium through tricuspid valve → right ventricle through pulmonic valve → pulmonary artery → left and right pulmonary arteries → left and right pulmonary veings → left atrium

    Valves open when pressure is applied in the forward direction.
  6. Joints, Ligaments, Tendons
    Joint: location at which bones connect (fibrous, cartilaginous, synovial)

    Synovial: ends of two bones covered with synovial capsule (encloses synovial fluid - lubricant); knee, hip, shoulder, fingers

    Ligaments: Keep bones attached across joints

    Tendons: Attach muscles to bones
  7. Blood pressure
    Step 1A: A;; 4 chambers relaxed, blood comes from systemic circulation to RA from vena cava and to LA from pulmonary veins

    Step 1B: Atrial contraction, blood flows into left and right ventricles

    Steps 1A and 1B are diastole

    • Step 2: Ventricular contraction, blood flows from left ventricle to systemic circulation (aorta) and from right ventricle to pulmonary circulation (pulmonary artery)
    • Step 2 is systole
  8. Lymphatic Organs
    Spleen acts as lymphatic filter for blood, Thymus is the site of T-lymphocyte maturation
  9. Humoral immunity
    B lymphocytes - memory (remember antigen) or plasma (make and release antibodies)

    Active immunity: Antibodies produced during immune response

    Passive immunity: Antibodies produced by one organism and are transferred to another organism
  10. Cell-mediated immunity
    T lymphocytes - killer (destroy cells) or suppressor (regulate B and T cells to decreases anti-antigen activity) or Helper (activate B and T cells and macrophages by secreting lymphokines)
  11. Composition of Bone
    Bone matrix composed of organic and inorganic substances (hydroxyapatite is crystal made of calcium and phosphorous, Type I collagen, proteins)

    • Osteoblasts synthesize type I collagen
    • Osteocytes maintain matrix
    • Osteoclasts promotes ongoing breakdown, resorption, and remodeling of bone
  12. Pulse
    Force of propulsion of blood from left ventricle to aorta can be felt as arterial pulse. Radial pulse can be used as heart rate
  13. The heart's pacemaker
    The sinoatrial (SA) node is in right atrium just below superior vena cava and is intrinsically rhythmic

    Under normal conditions, vagus nerve slows rate of SA node to 50-75 beats/min

    Signal from SA node goes → atrioventricular (AV) node → the septum by way of bundle of His → purkunje fibers → ventricular walls
  14. Skeletal muscle
    • Long, multinucleated cells "myofibers"
    • Sarcomere - contractile unit, composed of thin filaments (actin), and thick filaments (myosin)
  15. Muscle Contraction
    Nerve impulse→neuromuscular junction→release of acetylcholine which binds to sarcolemma→depolarization by T tubulues→release of Ca2+→binds to troponin on actin filaments→conformational change that makes tropomyosin uncover binding sites→myosin heads attach to actin→interactions with ATP cause shortening of sarcomere→contraction
  16. Smooth muscle
    • Involuntary control
    • Mononucleate, elongated, non-striated cells
    • Since they don't have troponin/tropomyosin, Ca2+ binds to myosin light chain kinase (MLCK), which phosphorylates myosin head
  17. Cardiac muscle
    Intercalated disks - attachment points between adjacent muscle cells

    Gap junctions between muscle fibers allow for unimpeded flow of ions, which makes it easier to propagate an action potential
  18. Haversian system, Haversian canal, spicules
    System: A set of concentric lamellar parallel to the bone's long axis, dsitrubte nutrients throughout compact bone

    Canal: Carries blood vessels and nerves, filled with loose connective tissue

    Spicules: thin segments of bone in spongy bond that absorb nutrients from marrow
  19. Purpose of Capillary Bed Exchange
    Capillaries bring oxygen and nutrients to all cells and remove waste products

     - capillaries constrict in cold to reduce bThermoregulationlood flow to reduce loss of heat
  20. Hydrostatic/oncotic pressure
    At the proximal (arterial) end of capillary has higher hydrostatic pressure so that fluid is propelled across vessel's wall into interstitial fluid

    At the distal (venous) end of the capillary has higher oncotic pressure so that the fluid just released is drawn back in
  21. Morphology of bone
    • The outer, dense portion is compact
    • The inner, marrow-filled cavity is spongy
    • Marrow is either red (RBC/platelet production) or yellow (fat cells)
    • In newborns, all marrow is red
    • In adults, red marrow is confined to flat bones (ribs, pelvis)
    • Under stress, yellow marrow can be turned to red to increase RBC production
  22. Biochemistry of blood gasses
    CO2 enters blood stream, and in presence of carbonic anhydrase CO2 + H2O ⇄ H2CO3

    In RBCs, carbonic acid dissociates: H2CO3 ⇄ H+ + HCO3-

    Carbon dioxide combines with hemoglobin: CO2 + HbO2 ⇄ HbCO2 + O2
  23. Resting Potential, Depolarization, Action Potential, Repolarization
    • Resting: High sodium outside and high potassium inside, cells is electrically negative inside 
    • Depolarization: Sodium rushes inside cell so cell is positive inside
    • Action potential: Depolarization along entirety of cell membrane
    • Repolarization: resting potential restored when potassium rushes outward
  24. Digestion enzymes, site of production, site of function, function
    • Salivary amylase, salivary glands, mouth, starch to maltose
    • Pancreatic amylase, pancreas, small intestine, starch to maltose
    • (Maltase, sucrase, lactase), instestinal glands, small intestine, (maltose, sucrose, lactose) to glucose
    • Pepsin, chief cells of gastric glands, stomach, hydrolyze peptide bonds
    • Trypsin, pancreas, small intestine, hydrolyzes peptide bonds and activates other zymogens
    • Chymotrypsin, pancreas, small intestine, hydrolyzes peptide bonds
    • Carboxypeptidase, pancreas, small intestine, hydrolyzes terminal peptide bond
    • Aminopeptidase, intestinal glands, small intestine, hydrolyzes proximal peptide bond
    • Dipeptidases, intestinal glands, small intestine, hydrolyzes pairs of amino acids
    • Enteropeptidase, intestinal glands, small intestine, converts trypsinogen to trypsin
  25. mouth, esophagus, stomach
    • Mouth: mechanical (mastication) and chemical (initiates breakdown of starch)
    • Esophagus: conduit for food from mouth to stomach, series of contractions - peristalsis
    • Stomach:low pH, vagus nerve stimpulates production and secretion of HCl from parietal cells, food goes to pyloric sphincter to the duodenum
  26. The liver and bile
    • Bile is produced in the liver and stored in teh gall bladder
    • Bile contains no enzyme but emulsifies fats
    • Liver roles include gluconeogenesis, processing urea, detoxification of waste/chemicals/drugs, storage of iron and vitamin B12, beta-oxidation of fatty acids to ketones, interconversion of carbs, fat, and amino acids
  27. Small intestine
    Chyme enters duodenum and is processed by enzymes. Small food subunits can enter the bloodstream via capillaries or go to the liver
  28. Large intestine
    Watery mix of food at end of small intestine arrives to large intestine by ileocecal valve

    Resoprtion of large amounts of water from lumen

    Feces leave through anus
  29. Energy Requirements for Muscular function
    Maintaining resting membrane potential that allows for depolarization and action potential

    Dynamic interaction between myosin and actin

    Return of calcium from sarcoplasm to sarcoplacmic reticulum after contraction
  30. Filtration at the glomerulus
    Blood from abdominal aorta → renal artery→ afferent arterioles→ individual renal corpuscles→ glomerular capillaries→ visceral layer (just beneath glomerular basement)→ bowman's space

    non-filterable blood components (blood cells/macromolecules) don't pass through visceral (inner) layer of Bowman's capsule and exit via efferent arteriole
  31. Renal corpuscle
    • Composed of flomerulus, glomerulear basement, Bowman's capsule
    • Bowman's capsule is a double-walled cup formed as enlargement of proximal end of renal tubule (parallel with renal tubule)
    • Twists into proximal convoluted tubule→ descending limb of the loop of Henle→ extends into the pyramids of renal medulla→ ascending limb of the loop of Henle→ cortex→ distal convoluted tubule→ collecting duct→ calyces (sections of renal pelvis)→ ureter→ urinary bladder→ micturition
  32. Hormonal Regulation of Water Retention
    ADH is released from posterior pituitary to increase collecting duct's permeability to water to increase water reabsorption (in times of dehydration)
  33. Purpose of kidneys
    • Excretion of hydrophilic waste (liver responsible for hydrophilic waste)
    • Maintain constant solute concentration
    • Maintain constant pH (7.4)
    • Maintain constant fluid volume (important for blood pressure and cardiac output)
  34. Structure of kidneys
    • Outer is renal cortex and inner is renal medulla
    • Medulla is made of renal pyramids
    • Renal pelvis is innermost portion of kidney with is an extension of the ureter
    • Each nephrone(basic unit of filtration) consists of renal corpuscle which is continuous with a renal tubule
  35. Ascending limb of the loop of Henle
    • Impermeable to water but is permeable to sodium
    • NaCl reabsorbed by passive diffusion and active transport into interstitial volume
  36. Descending limb of the loop of Henle
    Filtrate encounters higher salt concentration so water leaves out of loop to equalize concentrations; large amounts of water reabsorbed into body here
  37. Proximal Convoluted Tubule
    most reabsorption happens here (75% of filtrate) or waste molecules are added to filtrate (secretion)
  38. Peptide hormone (chemical class, synthesis, blood travel, receptor binding, effect on target, length of effect)
    Hydropilic, made in ER/golgi, stored in vesicles, dissolve in plasma, bind to receptors on surface of target cell, induce second messenger cascades that result in modifying existing enzymes and proteins, rapid buy short-lived
  39. Steroid hormone (chemical class, synthesis, blood travel, receptor binding, effect on target, length of effect)
    hydrophobic, made from cholesterol in SER, secreted right away, travel in blood bound to proteins, diffuse across plasma membrane and bind to receptors in cytoplasm, go to nucleus and alter transcription (change amounts of protein), slow but long-lasting
  40. Anterior Pituitary Hormones
    follicle-stimulating (P-follicle maturation), luteinizing (P-ovulation), adrenocorticotropic (P-stimulates adrenal glands to make ans secrete glucorticoids), thryoid-stimulating (P), prolactin (P-milk production/secretion), growth hormone (P-bone and muscle growth/lipolysis)
  41. Posterior Pituitary Hormones
    Oxytocin (P-uterine contractions during labor, milk secretion), ADH (P-water reabsorption in kidneys)
  42. Thryroid Hormones
    T4/T3 (a.a.-metabolic activity), calcitonin (P-decreases blood calcium levels)
  43. Parathyroid Hormones
    Parathyroid (P-increases blood calcium levels)
  44. Adrenal Hormones
    Cortisol in cortex (S-increase blood glucose and decrease protein synthesis), aldosterone in cortex (S-increase sodium reabsorption and potassium secretion in kidneys), epinephine in medulla (a.a.-increases blood glucose levels and heart rate)
  45. Pancreas Hormones
    Glucagon (P-conversion of glycogen to glucose in liver, increases blood glucose), insulin (P-lowers blood glucose, increases glycogen storage), somatostatin (P-suppresses secretion of glucagon and insulin)
  46. Testes Hormones
    Testosterone (S-male secondary sexual characteristics)
  47. Ovary/Placenta Hormones
    Estrogen (S-female secondary sexual characteristics), progresterone (S-growth/maintenance of endometrium)