Final exam Flashcards

Question

How does blood flow work in the liver?

Answer 1

-most absorbed nutrients fromGI system enter capillaries then into hepatic portal vein (fat go into lymphatic system rather than blood) -xenobiotics (foreign substances) must first pass through the liver before reaching systemic circulation 25% hepatic artery + 75% hepatic portal vein -> sinusoids -> central vein -> hepatic vein

Answer 2

-bile salts (facilitate fat digetion) -bile pigments (eg. bilirubin, from Hb breakdown) -cholesterol also: -drugs and other xenobiotics being processed in liver and excreted in feces

Answer 3

1) Fe+ from diet 2) Fe+ absorbed by active transport 3) bone marrow uses Fe+ to make hemoglobin (Hb) 4) spleen converts Hb to bilirubin 5) excess Fe+ stored in liver as ferritin 6) liver metabolizes bilirubin and excretes it in bile 7) bilirubin metabolites excreted in urine and feces -bilirubin or its metabolites are responsible for: + normal colour of feces + normal colour of urine -indicators of injury/pathology + yellow phase of bruises + yellow pigmentation of jaundice (hyper bilirubin anemia)

Answer 4

combination of mechanical and enzymatic processes -occurs in mouth, stomach, small intestine -chewing, 'churning' -> expose more surface area to enzymes + emulsification via bile -> exposes more surface area for lipid digestion

Answer 5

crossing the gut epithelium -mostly in small intestine (some ions/water absorbed in the large intestine) -use many of the same transporters as the kidney + exception: fat enters lymph vessels (lacteals)

Answer 6

not directly related -influenced by motility and secretion, which are regulated

Answer 7

lumen -> apical membrane -> epithelial cell (enterocyte) -> basolateral membrane -> interstitium -> capillary OR lymph

Answer 8

-constitute ~50% caloric intake (mostly starch, sucrose) -can only be absorbed via a membrane transporter + we only have membrane transporters for MONOsaccharides -artificial sweeteners: typically interact, in some way, with 'sweet' receptors, but cannot be digested to a form that can cross enterocytes

Answer 9

glucose polymers - (amylase) -> dissarcharides -> monosaccharides

Answer 10

1) glucose/galactose enter with Na+ on SGLT (apical side) and exits on GLUT2 (basolateral side) 2) fructose enters on GLUT5 (apical side) and exits on GLUT2 (basolateral side)

Answer 11

1) endopeptidases (aka proteases) digests internal peptide bonds of polypeptides - making smaller peptides - example of endopeptidases: pepsin (stomach), trypsin, chymotrypsin (small intestine) 2) exopeptidases digest terminal peptide bonds to release amino acids -examples of exopeptidases: aminopeptidase (from brush border), carboxypeptidase (from pancreas) products of protein digestion = amino acids, di=peptides, tripeptides

Answer 12

proteins broken down into peptides -di and tripeptides cotransport with H+ -amino acids cotransport with Na+ -small peptides are carried intact across the cell by transcytosis + normally only occurs in first few hours to days of life prior to 'gut closure'

Answer 13

triglycerides (most fat calories are in this form, major lipid in plants and animals) cholesterol, phospholipids, long chain fatty acids, fat soluble vitamins -digestion complicated by solubility issues -leave stomach as large droplets mixed with aqueous chyme + low surface area available to interact with enzymes -broken down into smaller particles through action of bile salts + bile salts are derivatives of cholesterol 'amphipathic'

Answer 14

primary bile acid modified by gut bacteria -> secondary bile acid-> conjugated in liver -> conjugated bile acid OR conjugated in liver -> conjugated bile acid

Answer 15

-bile salts coat lipids to make emulsions of large droplets + hydrophobic side associates with lipids + polar side chains (hydrophilic side) associates with water -pancreatic lipases can act on triglycerides in droplets, aided by colipase from pancreas (break don into monoglyceride and free fatty acids)

Answer 16

formation of micelles -all fat is digested in smaller components except cholesterol -micelles can then move close to the surface of enterocytes (epilthelial cells of SI) and lipids can diffuse across apical membrane into cells

Answer 17

1) bile salts coat fat droplets 2) pancreatic lipase and colipase break down fats into monoglycerides and free fatty acids stored in micelles 3a) monoglycerides and fatty acids diffuse from micelles across apical membrane into cells 3b) cholesterol is transported into cells 4) absorbed fats combine with cholesterol and proteins in intestinal cells to form chylomicrons 5) chylomicrons removed by lymphatic systems more details: -monoglycerides and fatty acids reform into triglycerides in smooth ER -triglycerides, cholesterol, proteins form chylomicrons, which are packed into vesicles and exocytosed (short fatty acids can travel solo, entering capillaries rather than lymph)

Answer 18

digested into nucleotides, then bases and monosaccharides -bases -membrane transporters -sugars -same transporters as other monosaccharides

Answer 19

fat soluble (A, D, E, K) -absorbed in small intestine along with fats water soluble (C, most Bs) -typically absorbed in small intestine via membrane transporters exception: B12 (cobalamin) -participates in metabolic pathways in every single cell, particularly important in RBC synthesis *absorption (in ileum) requires protein secreted by gastric parietal cells ('intrinsic factor') *deficiency of intrinsic factor leads to deficiency of B12 that cannot be corrected by oral B12 supplementation

Answer 20

absorbed by small and large intestine 1) Na+ enters by multiple pathways 2) the Na+/K+ ATPase pumps Na+ into ECF 3) water and K+ move through paracellular pathway in general: ions (espNa+) moves across apical side (various transporters); main driver on basolateral side is Na+/K+-ATPase; water follows by osmosis

Answer 21

two of the few substances for which intestinal absorption is regulated -decreased levels -> detector -> signal -> increased intestinal uptake

Answer 22

-Fe2+ and H+ contransported across apical membrane by DMT1 -heme also transported across apical membrane -heme broken down (polypherin + Fe2+) -Fe2+ transported across basolateral membrane by ferroportin (regulated)

Answer 23

-paracellular absorption not regulated -Ca2+ crosses apical membrane via Ca2+ channel -transport of Ca2+ across basolateral membrane regulated by vitamin D3

Answer 24

integrated in CNS -sensory info from GI tract to CNS -'feedforward' reflexes that originate outside GI tract + include cephalic reflexes in response to sight, smell, thought of food, effects of emotion -efferent limb always autonomic + parasympathetic = excitatory + sympathetic = generally inhibitory

Answer 25

integrated in gut in 'enteric nervous system' (gut brain) -neurons in submucosal plexus receive signals from lumen, regulate secretion -neurons in myenteric plexus regulate motility

Answer 26

-can act locally (paracrine) or travel via blood (endocrine) + effects on motility - altered peristalsis, gastric emptying + effects on both exocrine and endocrine secretion -some gut peptides can also act on brain (some even produced there)

Answer 27

-has intrinsic neurons that lie entirely within the gut (similar to interneurons in CNS) -releases more than 30 different neurotransmitters and neuromodulators (not epi,NE,ACh but similar molecules used in CNS) -has glial supported cells (similar to astrocytes of CNS) -diffusion barrier -> capillaries surrounding ganglia are not very permeable (similar to blood-brain barrier) -acts as integrating center (gut function can be regulated without CNS)

Answer 28

-acid chyme passing into duodenum -> pancretic juice secreted mechanism? -vagus afferents from duodenum to brain -> vagal efferents from brain to pancreas -> pancreatic juice secreted into duodenum -pancreatic secretion was thought to be controlled only by vagus nerve

Answer 29

-carefully dissected away all nerves surrounding pancreas and duodenum + put acid in duodenum + pancreas still secreted -hypothesis: acid caused release of signal from duodenum into blood -tested hypothesis: + collected lining of duodenum + added acid to it + injected it intravenously + resulted in pancreatic secretion -factor from duodenum that stimulated pancreatic secretion = secretin -general term for blood-borne regulators: hormones

Answer 30

1) gastrin family -includes gastrin, CCK -major target are stomach (gastrin), intestine, and accessory organs (CCK) 2) secretin family -secretin, vasoactive intestinal peptide (VIP), gastric inhibitory peptide (GIP), glucagon-like peptide 1 (GLP-1) -both endocrine and exocrine targets 3) motilin -acts on gut smooth muscle -regulates migrating motor complexes

Answer 31

-saliva -> secretion under autonomic control + softens and lubricates food + digestion: salivary amylase, some lipase + antimicrobial: lysozyme, immunoglobins -chewing (mastication) -transfer to stomach (deglutition = swallowing)

Answer 32

1) tongue pushes bolous against soft palate and back of mouth, triggers swallowing reflex 2) breathing inhibited as bolous passes closed airway 3) food moves downward into esophagus, propelled by peristalic waves and aided by gravity -swallowing reflex integrated in medulla -sensory afferents in cranial nerve IX an somatic motor and autonomic neurons mediate reflex

Answer 33

-lower esophageal sphincter guards entry into stomach -if LES not closed acid from stomach can splash up into lower esophagus + during respiration (when intrathoracic pressure drops) + during churning of the stomach = gastroesophageal reflux disease (GERD) 'heartburn'

Answer 34

initiated with long vagal reflexe anticipation/presence of food in mouth -> activation of neurons in medulla -> efferent signals to salivary glands, autonomic signals via vagus to enteric nervous system (gut brain) -> increase motility and secretion in stomach, intestine, and accessory organs

Answer 35

once food enters stomach, series of short reflexes distention (stretching) or peptides and amino acids -> sensory signal to enteric nervous system -> increased motility and secretion in stomach, intestine, accessory organs

Answer 36

1. storage - neurally mediated 'receptive relaxation' of upper stomach -importance of storage function has been more apparent as gastric surgeries have become more popular *'gastric dumping syndrome' 2. digestion - mechanical and chemical processing into chyme -secretions begin before food arrives ... *enzymes, acid, hormones 3. protection - against microbes -> acid -self-protection -> mucus-bicarbonate barrier

Answer 37

1. parietal cells -> acid -activates pepsin -denatures proteins (more accessible to pepsin) -anti-microbial 2. chief cells -> pepsin -endopeptidase (particularly affective on collagen=meat digestion) 3. chief cells -> gastric lipase -minor contribution to fat digestion (co-secreted with pepsin) 4. ECLs -> histamine -binds to H2 receptors on parietal cells and stimulates acid secretion 5. G cells -> gastrin -triggered by long and short reflexes multiple roles 6. D cells -> stomatostatin -stops secretion of acid and pepsin (negative regulator)

Answer 38

1) food or cephalic reflexes initiate gastric secretion 2) gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine 3) acid stimulates short reflex secretion of pepsin 4) somatostatin release by H+ is feedback signal that modulates acid and pepsin release

Answer 39

bicarbonate barrier - protects itself from acid breakdown of mucus-bicarb barrier = peptic ulcer -acid and pepsin damage mucosal surface, creating holes that extend into submucosa and muscularis layers

Answer 40

-main treatment was 'antiacids' + substances that neutralized stomach acid -more modern approaches include +H2 receptors antagonists -> block histamine +proton pump inhibitors -> block Na/K ATPase

Answer 41

-gastrin, histamine, and ACh (PNS stim) cause H+/K+ATPase expression on parietal cells

Answer 42

-stomach produces chyme by actions of acid, pepsin, perastalsis -intestinal phase begins with controlled entry of chyme into small intestine -sensors in duodenum feed back to stomach to control delivery of chyme, feed forward to intestine to promote digestion, motility and nutrient utilization

Answer 43

bile salts are released into duodenum, absorbed in terminal ileum, enter portal circulation, travel back to liver -recycled several times during a meal

Answer 44

1. pancreatic secretions (including zymogens and trypsinogen) enter lumen of small intestine 2. enteropeptidase in brush border activates trypsin (trypsinogen -> trypsin) 3. trypsin activates zymogens (zymogens -> activated enzymes)

Answer 45

most fluid is absorbed in small intestine -transport of organic nutrients and ions creates osmotic gradient -most absorbed nutrients move into capillaries in villi, then into hepatic portal vein *fats go into lymphatic system rather than blood xenobiotics (foregin body substances) must first pass through liver before reaching systemic circulation

Answer 46

-removes most of the remaining water -> forms feces motility: -ileocecal valve relaxes each time a peristalic wave reaches it (also relaxes when food leaves the stomach- gastroileal reflex) -segmental contractions with little forward movement except when mass movements occur 3-4 times/day (wave of contractions that send bolus forward trigger distension of rectum -> defecation reflex)

Answer 47

imbalance between intestinal absorption and secretion 1. osmotic diarrhea= unabsorbed osmotically active solutes 2. secretory diarrhea= bacterial toxins increase CL- secretion eg. cholera -can be adaptive (flushing out toxin) but can also lead to dehydration and metabolic acidosis

Answer 48

-enters cell via pentameric B subunits -travels in retrograde direction through golgi -mimics a misfolded protein and gets dumped into the cytosol (normally to be degraded) -instead A1 subunit (enyzme) modifies Galpha subunit -remains bound to GTP -constant activation of AC -persistent elevation on cAMP -sustained activation of CFTR channel

Answer 49

suggestion: *CF heterozygotes have some advantage over `non-CF' homozygotes -heterozygotes have ~ 50% functional CFTRs *enough for normal function but allows them to resist death by cholera due to reduced Cl-secretion during infection? *survive to pass on the gene to offspring?? BUT: *cholera epidemics did not strike Northern Europe until 19th century RESPONSE: *CFTR channels involved in other diseases that were around earlier -bronchial asthma, typhoid fever, ...

Answer 50

homesostatic: -eating when energy fuels are depleted (metabolically driven) non-homeostatic: -eating in absense of hunger -eating despite large fat reserves (involves cognitive, reward, emotion factors) (has neural similarities to addiction = hedonic eating)

Answer 51

2 centres in hypothalamus: 'hunger/feeding' centre and 'satiety' centre glucostatic theory: *intake regulated by glucose levels, monitored by centres in the hypothalamus -plasma glucose low -> satiety centre suppressed -> feeding centre dominant lipostatic theory: *signal from fat stores to brain modulates eating behaviour 1994: discovery of protein hormone synthesized in white adipose tissue = leptin

Answer 52

ob/ob mouse = mutation in leptin product db/db mouse = mutation in leptin receptor both cause mice to be obese and eat a lot

Answer 53

stomach: increased ghrelin - secreted by cells of empty stomach

Answer 54

stomach: -increased stretch or increased acid upper small intestine: -increased CCK (in response to protein/fat) -increased glucose in lumen lower small intestine/colon: -increased peptide YY (PYY) -increased GLP1 (both triggered by macronutrients in lumen and also neural reflex from upper small intestine)

Answer 55

neuropeptide Y

Answer 56

C6H12O6+ O2+ ADP + Pi -> CO2+ H2O + ATP + heat rate of oxygen consumption? rate of CO2 production? -But ratio of CO2produced / O2consumed is different for macronutrients other than glucose

Answer 57

*age, sex *lean muscle mass -muscle has higher O2consumption than adipose even at rest *activity level *diet (heat production increases after eating, extent depends on what was eaten) *hormones,gut peptides *genetics

Answer 58

1. metabolized to provide energy to fuel mechanical work = oxodize 2.used in synthesis reactions for growth and maintenance of tissues = build 3.stored as glycogen (liver, skeletal muscles) or fat= store

Answer 59

1. fed/absorptive state = anabolic, products of digestion being absorbed and used/stored 2. fasted/postabsorptive state = catabolic, body taps into stores

Answer 60

usually in plasma: -free fatty acid pool -glucose pool -amino acid pool

Answer 61

1. no regulation = pathway cycles bath and forth, no net synthesis of glucose or glycogen 2. fed-state metabolism under the influence of insulin = glucose to glycogen reaction increases, enzymes for glycogen breakdown inhibited = net glycogen synthesis 3. fasted state metabolism under the influence of glucagon = enzymes that break down glycogen are more active and enzymes that synthesize glycogen are inhibited = not glucose synthesis

Answer 62

absorbed glucose travels to liver -70% passes through to other tissues -30% moves into hepatic cells + enters glycolysis (ATP synthesis or stored as glycogen or fat)

Answer 63

absorbed amino acids travel to the liver -some pass through liver (used for synthesis) -some move out of sinusoids into hepatic cells (for synthesis of liver proteins, enzymes) if not used for protein synthesis AAs can be deaminated and and their carbon skeletons re-deployed -converted to metabolites that can be used to generate glucose -converted to acetoacetate to make fatty acids (ketogenic AAs)

Answer 64

formed in enterocyte -cholesterol, TGs, phospholipid plus lipid-binding proteins (apoproteins) -enter lymphatic drainage, eventually enter circulation -acted upon by lipases in capillary endothelium +FFA can be oxidized for energy (most cells) +FFA plus glycerol can be re-esterified and stored as TG (adipose) +remaining particles (HDL, chylomicron remnants) taken up by liver

Answer 65

-break down fat (βoxidation of FAs) -store fat (as TGs) -use cholesterol to form bile salts (release into gut lumen) -package FAs and cholesterol as LDL particles (release into circulation as sources of cholesterol and FAs) + can only be taken into cells by receptor-mediated endocytosis *protein components (apoproteins) interact with receptors

Answer 66

1.Glycerol can be made from glucose through glycolysis. 2.Fatty acids made when 2-carbon acyl units from acetyl CoA linked together. 3.One glycerol plus 3 fatty acids = triglyceride (happens in smooth ER). 4.Even with zero dietary cholesterol, cholesterol can and will be synthesized from acetyl CoA

Answer 67

maintain plasma glucose levels -achieved through pathways that yield glucose or ATP: glycogenolysis lipolysis oxidation of amino acids gluconeogenesis

Answer 68

1) liver glycogen -> glucose 2) TGs in adipose -> glycerol + FFAs -> enter blood 3) muscle uses glycogen for energy and also uses fatty acids and break down their proteins to amino acids that enter blood. 4) brain only uses glucose and ketone bodies for energy

Answer 69

breakdown of glycogen most glycogen becomes glucose 6 phosphate: -splitting off glucose by addition of Pi (most) + only liver can remove Pi to create free glucose -splitting off glucose then spending an ATP to phosphorylate *muscle can contribute to plasma glucose only indirectly by exporting pyruvate or lactate

Answer 70

-free amino acid pool is usually used for ATP production during fasted state (proteolysis- break down of proteins only occurs during extended fasts) -amino acids are deaminated and create intermediates that can: + directly enter glycolysis or krebs cycle + be sent to the liver to be converted into glucose (gluconeogenesis)

Answer 71

1) lipases digest TGs into glycerol and FFAs 2) glycerol becomes a glycolysis substrate 3) B-oxidation chops 2 acyl units off FA 4) acyl units become acetyl CoA and can be used in krebs cycle

Answer 72

formation of ketone bodies -occurs when lipids are broken down faster than acetyl CoA can be used in krebs cycle -can enter blood and provide brain with energy during times of starvation -typically generated by low carb, high protein/fat diets ketogenesis can be dangerous -certain ketone bodies are strong acids that can disrupt acid-base balance (ketoacidosis)

Answer 73

whether transformations of energy substrates (carbs, fats, proteins) are biased toward storage/ anabolism or breakdown/ catabolism

Answer 74

endocrine -primary role -products of endocrine pancreas *insulin/glucagon ratio neural -regulation of food intake -endocrine pancreas also innervated (autonomic)

Answer 75

little islands of endocrine cells within exocrine cells of pancreas -majority of pancreas is exocrine

Answer 76

more insulin = increase glucose oxidation increase glycogen synthesis increase fat synthesis

Answer 77

more glucagon = increased glycogenolysis increased gluconeogenesis increased ketogenesis

Answer 78

creating glucose from substrates

Answer 79

increased plasma glucose increased plasma amino acids increased GLP1, GIP increased PNS stimulation

Answer 80

striated muscle, adipose (expressing glut4 transporter) liver

Answer 81

-increased transport into glut4 expressing target cells -increased glucose metabolism -increased glycogenesis -increased fat synthesis, increased protein synthesis

Answer 82

-GLUT2 transporters -move glucose into beta cells by facilitated diffusion - K+leak channels -usually open, closes when ATP binds to it "ATP-gated K+channel" - voltage-gated Ca2+ channels - secretory vesicles of insulin waiting for release signal

Answer 83

low blood glucose -> metabolism slows -> decreased ATP -> KATP channels open (leaking) -> cell at resting Em = no insulin released (voltage gated Ca2+ channels closed) KATP channels open, cell at RMP, no insulin released

Answer 84

high blood glucose -> increased metabolism -> increased ATP -> KATP channels close -> cell depolarizes -> voltage gated Ca2+ channels open -> insulin released closure of K+ATP channels depolarizes cell, opening of Ca2+channels, exocytosis

Answer 85

-enzyme coupled, receptor, tyrosine kinase (RTK) + 2 alpha subunits, extracellular, insulin binds here + 2 beta subunits penetrate through the plasma membrane -when activated, RTKs transfer phosphate groups from ATP to tyrosine residues on target proteins insulin binds -> B subunits phosphorylate themselves -> activated RTK phosphorylates target proteins -> (altered protein/enzyme activity) -> cell responses

Answer 86

fasted state = no insulin = no GLUT4 transporters on membrane fed state = insulin signalling = GLUT4 inserted into membrane = glucose enters cell

Answer 87

fasted state = low blood glucose, low insulin -hepatocytes make glucose and export it via GLUT2 transporters fed state = high blood glucose, high insulin -gradient favours glucose import via GLUT2 -insulin signalling activates hexokinase which: glucose -> glucose 6 phophate ->.... (keeps free glucose low in cell)

Answer 88

activates enzymes that enhance: -glycolysis (glucose oxidation) -glycogenesis (storage) -AA utilization/protein synthesis -lipogenesis inhibits enzymes that enhance: -gluconeogenesis -glycogenolysis -proteolysis -lipolysis -B oxidation of fatty acids

Answer 89

-produced by alpha cells of pancreas -member of secretin family of peptides -main trigger is low blood glucose -main target is liver -activates GPCR, cAMP -main function is to prevent hypoglycemia + during overnight fast, ~75% of the glucose from the liver comes from glycogenolysis, ~25% from gluconeogenesis

Answer 90

group of diseases characterized by elevated blood glucose (hyperglycemia) resulting from: -inadequate insulin secretion (Type 1) -abnormal target cell responsiveness or both (Type 2)

Answer 91

*accounts for ~90% of diabetes -was once called "mature onset" diabetes (versus "juvenile") *typically there is "insulin resistance", with delayed response to a glucose 'challenge' (oral glucose tolerance test) -can be coupled with low, normal or high insulin secretion *acute symptoms not as severe as Type 1, but metabolism is not normal *Type 2 diabetes, atherosclerosis and hypertension often occur together, typically in association with obesity 'Metabolic Syndrome'

Answer 92

*larger animals (such as humans) have significant energy stores so can go without food for relatively long periods -but food restriction and fat depletion eventually lead to 'hungry brain' *powerful effector mechanisms that are adaptable, flexible, learn from experience *major force 'designing' the system was the constant struggle throughout evolution to find enough food for survival -resulted in very strong defence of the lower limits of adiposity

Answer 93

*modern environment acts on higher brain regions to over-stimulate food intake -advertising, social cues, stress vulnerability, ... *procuring food is no longer demanding or dangerous *exceeding the upper limits of body weight is no longer a disadvantage in terms of predator-prey relationships -little or no selection pressure for leanness *many obese humans become 'leptin-resistant' -also happens in lab animals when exposed to 'human' diets -makes sense in the wild in seasonal animals *elevated leptindoesn't curb appetite in summer when food abundant (building up stores), leptinsensitivity restored in winter -modern humans in perpetual 'summer'

Answer 94

yes - few reported cases

Answer 95

-located on top of the kidneys -adrenal cortex (outside) secretes hormones: aldosterone catecholamines (mostly epi) sex hormones cortisol -inside is neural

Answer 96

liver -> glucogenesis muscle -> protein catabolism adipose -> lipolysis *team glucagon = break down to get glucose also: immune system -> supression

Answer 97

in a circadian rhythm

Answer 98

*receptors expressed by all nucleated cells! *mostly longer-term (genomic) effects -classic steroid -increased expression of enzymes -"of receptors for other regulatory hormones effects in general: 1. prevention of hypoglycemia -adipose -> lipolysis -> FAs for energy, glycerol -muscle -> proteolysis -> AAs -liver -> gluconeogenesis *permissive for full effects of glucagon and epinephrine 2. suppress immune response

Answer 99

*built on work of Claude Bernard, Walter Cannon (homeostasis) -developed concept that a wide variety of 'stressors' (harmless, noxious, positive, negative) caused a generic response: *adrenal hypertrophy *atrophy of thymus / lymph nodes *GI ulcers -failure to cope with / adapt to stresses caused diseases of adaptation (ulcers, hypertension, etc) *led to many breakthroughs in hypothalamic-pituitary axis

Answer 100

*norepinephrine from sympathetic post-ganglionic neurons *epinephrine from adrenal medulla -rapid effects but very short half life (2 minutes) *various effects throughout body *metabolic effects: mobilize energy substrates -↓ insulin release, ↑ glucagon release -adipose -> lipolysis -> FAs for energy, glycerol -muscle -> glycogenolysis -liver -> glycogenolysis, gluconeogenesis -effects similar to glucagon but receptors expressed on a broader range of target cells

Answer 101

epinephrine and glucagon and cortisol together greatly increase blood glucose levels

Answer 102

aka. Cushing's syndrome *primary -cortisol-secreting adrenal tumors (not regulated by ACTH) *secondary -pituitary tumor that over-secretes ACTH "adenoma" *iatrogenic -secondary to cortisol therapy for other conditions "doctor's fault" would circulating ACTH be lower, higher, or normal?

Answer 103

-primary- adrenal insufficiency (Addison's disease) *adrenal gland does not develop normally *mutations in key steroidogenicenzymes *adrenal gland damaged / destroyed (autoimmune) -secondary -lack of ACTH would circulating ACTH be lower, higher, or normal?

Answer 104

*amino acid derivative (from tyrosine), containing iodine -only known use of iodine in body *mechanism of action more like steroids -binds to nuclear receptor *lipophilic, travels in circulation bound to thyroid-binding globulin T4-main circulating form T3-most active form, converted at target cell by deiodinases

Answer 105

*essential for normal growth / development, esp nervous system -thyroid hormone levels checked in all newborns in Canada *in adults, not essential, but affects quality of life *main function is to provide substrates for oxidative metabolism -increase oxygen consumption and generation of heat (thermogenesis) in most tissues 'basal metabolic rate' *increase activity of Na+/K+-ATPase -interact with other hormones to modulate carbohydrate, protein and lipid metabolism

Answer 106

-decreased oxygen consumption, decreased metabolic rate (cold intolerant) -neurological effects, fatigue -effects on skin, hair, nails most common cause is iodine deficiency -> enlarged thyroid gland 'goitre'

Answer 107

-increased oxygen consumption, increased heart production (intolerant of heat) -muscle weakness (protein catabolism) -neurological, cardiac effects -exophthalmos (protruding eyes) most common cause is graves disease -> autoantibodies that resemble TSH overstimulate thyroid gland (not subject to negative feedback regulation)

Answer 108

control of growth depends on many factors: *GH, plus many other hormones playing direct and permissive roles -insulin, thyroid hormone, sex steroids *adequate nutrition *absence of chronic stress *genetics *released throughout life but much more important during childhood *effects can be direct - -target cells express GH receptor *or indirect - -mediated by insulin-like growth factors (IGFs = somatomedins) produced by liver or target cells themselves *growth effects and metabolic effects

Answer 109

1) metabolic -carbohydrate -indirect effects lead to increased plasma glucose -fat -increased lipolysis, increased oxidation + catabolic with respect to CHOs and fat, 'anti-insulin' protein -increased AA uptake, increased protein synthesis, decreased oxidation for energy + anabolic with respect to proteins, 'pro-insulin' 2) growth -increased proliferation and differentiation of chondrocytes -> cartilage and bone growth -increased muscle growth (see metabolic effects) -increased growth of other soft tissues

Answer 110

due to GH hyposecretion, GH-receptor mutations ... dwarfism (though GH issues are not a common cause)

Answer 111

depends on whether excess secretion is before or after closure of growth plates of long bones -before -giantism -after -acromegaly

Answer 112

component of extracellular matrix of bones and teeth -bone is largest reservoir of calcium but very little of it is ionized and available for exchange

Answer 113

*extracellular calcium involved in ... -secretion / exocytosis (neurotransmitters, secretory products) -contraction of cardiac and smooth muscle -clotting cascade *intracellular calcium in SR, cytosol, mitochondria -involved in muscle contraction, signalling pathways

Answer 114

compact bone - dense, used for support spongy bone - forms calcified lattice

Answer 115

1. proliferating columns of chondrocytes at epiphyseal plate secrete collagen and other extracellular matrix components 2. older chondrocytes degenerate, leaving spaces 3. osteoblastsinvade spaces, lay down Ca-PO4matrix on cartilage base 4. osteoblasts revert to less active form (osteocytes)

Answer 116

large, multinucleate cells derived from hematopoietic stem cells -breaks down bone for reabsorption

Answer 117

only about 1/3 ingested calcium is absorbed -by paracellular and transcellular routes -absorption via transcellular route is hormonally regulated

Answer 118

-primarily via kidneys -freely filtered, most reabsorbed *hormonally controlled reabsorption at distal nephron only

Answer 119

parathyroid hormone

Answer 120

PTH released in response to ↓ plasma Ca++ kidney: ↑ Ca++ reabsorption bone: ↑ osteoclastactivity -> ↑ bone resorption small intestine: ↑ Ca++ absorption (via transcellular route)

Answer 121

*refers to group of fat soluble vitamins *forms from diet and UV-induced conversion of dermal precursors not biologically active until hydroxylation steps in liver and kidney

Answer 122

too much calcium

Answer 123

PTH from parathyroid gland Vitamin D

Answer 124

the science of the function of living systems

Answer 125

the maintenance of a relatively stable internal environment (especially ECF) -oscillation around a set point

Answer 126

the father of physiology coined the term "homeostasis"

Answer 127

Local control = cells near site of change initiate response Reflex control = cells at a distant site control response

Answer 128

stabilizes variable (correction in opposite direction of change)

Answer 129

control anticipates change

Answer 130

reinforces stimulus (NOT homeostatic)

Answer 131

1. endocrine - chemical released in blood and distributed throughout the body 2. neural - electrical signal travels down neuron then becomes chemical which travels to target cell 3. neuroendocrine - electrical signal travels travel down neuron then becomes chemical signal that is secreted into the blood

Answer 132

chemical properties of the ligands surface receptor = hydrophillic/lipophobic/water soluble intracellular receptor = hydrophobic/lipophillic/water insoluble

Answer 133

change receptor number or sensitivity increase = increase expression of gene that codes for receptor or increase expression of receptor proteins on cell surface decrease = internalize surface receptors change receptor sensitivity = phosphorylation

Answer 134

-signal molecule binds to receptor and causes conformational change -activates G protein by exchanging GDP for GTP -when GTp binds alpha subunit+GTP dissociates from the B and gamma subunits -G alpha subunit turns itself off by hydrolizing GTP

Answer 135

-blocks GTP hydrolysis (GTPase activity) -results in persistent activation of adenylate cyclase

Answer 136

-the nervous system has a role in maintaining the 'fitness' of the internal environment -some systems under tonic control -some systems are under antagonistic control -one chemical signal can have different effects in different tissues

Answer 137

neural = single target cell or limited number of adjacent target cells endocrine = exposed to all cells but only those which receptors respond

Answer 138

neural = electrical signal that turns chemical (neurotransmitter) endocrine = chemical signals

Answer 139

neural = very rapid endocrine = much slower than neural responses

Answer 140

neural = usually very short endocrine = longer than neural responses

Answer 141

neural = each signal is identical in strength. Increase intensity by increasing frequency endocrine = intensity proportional to amount of hormone secreted

Answer 142

bilateral symmetry -> cephalization -> consolidation of PNS -> nerves -> ventral nerve cord -> dorsal nerve cord -> spinal cord -> increasing role of forebrain

Answer 143

4 weeks: anterior end of neural tube specialized into 3 regions (forebrain, midbrain, hindbrain) and spinal cord 6 weeks: neural tube differentiates into major brain regions present at birth forebrain -> diencephalon, cerebrum midbrain hindbrain -> medulla oblongata, cerebellum, and pons 11 weeks: growth of cerebrum much more rapid than that of other regions birth: cerebrum covers most of other brain regions; convoluted surface due to rapid growth in confined space

Answer 144

-surrounded by bony cage: cranium -3 layers of connective tissues: meninges -fluid between layer: cerebrospinal fluid

Answer 145

layers of connective tissue that surround the brain and spinal cord dura mater = outermost layer arachnoid mater = middle layer pia mater = innermost layer

Answer 146

-ventricles within the brain and hollow central canal within the spinal cord -2 lateral ventricles and 2 descending ventricles that extend through in brain stem -CSF in ventricles continuous with fluid in central canal of spinal cord -CSF is secreted by the choroid plexus within each ventricle (choroid plexuses produce ~500mL of CSF/day)

Answer 147

1. interstitial fluid - surrounds neurons and glial cells 2. plasma - within cerebral blood vessels 3. cerebrospinal fluid - within ventricular system and bathes external surfaces of the brain between meninges (removed and replaced ~4 times per day)

Answer 148

CSF has: - lower K+, Ca2+, HCO3-, glucose, pH -similar Na+ -very low protein, no blood cells (presence of elevated protein or blood cells collected from CSF indicates infection)

Answer 149

1. oligodendrocytes - form myelin sheaths within CNS "white matter" 2. microglia - immune cell lineage 3. astrocytes - regulate local ECF by releasing chemicals (numerous in the brain) 4. ependymal cells - creates barrier between compartments (decide what ends up in CSF)

Answer 150

1. astrocyte foot processes- secrete paracrine factors that promote tight junction formation 2. tight junctions- prevent solute movement between endothelial cells

Answer 151

-lipid soluble molecules cross readily (o2, co2) -hydrophillic substances (ions, amino acids, peptides, proteins) will only cross if specific transporters/carriers are present in endothelial cells of capillaries within CNS -considerations for drugs that are and are not wanted to reach the CNS: antihistamines and treating diseases of the CNS

Answer 152

1. oxygen requirement- neurons are "obligate aerobes' (require O2 to functions) so O2 readily crosses the blood brain barrier 2. glucose requirement- capillaries of CNS express high levels of glucose transporters to provide adequate levels of glucose (brain responsible for 1/2 body's glucose consumption) 3. vaculature to deliever O2 and glucose- approximately 15% of cardiac output received by the brain

Answer 153

-major path for information flow between CNS, skin, joints and muscles -contains neural networks involved in locomotion -divided into 4 regions (cervical, thoracic, lumbar, sacral) each of which is divided into 4 segments -each segment gives rise to a pair of spinal nerves

Answer 154

1. white matter (myelinated axons) - consists of ascending and descending tracts -ascending tracts: dorsal columns (fine touch, proprioception, vibration) or spinothalamic (pain,temp, crude touch) -descending tracts: corticospinal tracts (voluntary movement) 2. grey matter (synapse + cell bodies) - consists of sensory and motor nuclei

Answer 155

dorsal root -> dorsal horn gray matter

Answer 156

ventral horn gray matter -> ventral root

Answer 157

-spinal reflex initiates response without input from the brain (integrating center within spinal cord) -still sends feedback to the brain

Answer 158

-medulla pons and midbrain -oldest most primitive part of the brain -organized much like the spinal cord (most cranial nerves originate here) -contains nuclei associated with reticular formation (diffuse network of neurons involved in processes such as arousal/sleep, muscle tone, coordination of breathing, blood pressure)

Answer 159

coordination of eye movement, visual and auditory reflexes

Answer 160

1. gray matter involved in control of many involuntary functions (blood pressure, breathing, swallowing, vomiting) 2. white matter - ascending somatosensory tracts, descending corticospinal tracts 3. site of deccusation for most neurons in corticospinal tract

Answer 161

relay station between cerebrum and cerebellum (also works with medulla to coordinate breathing)

Answer 162

2nd largest structure in the brain coordinates movement

Answer 163

located between brain stem and cerebrum 1. thalamus - relays and integrates sensory info from lower parts of the CNS, ears, eyes, motor info from cerebellum 2. hypothalamus - homeostasis: contain centers that drive behavior related to hunger, thirst and influences autonomic responses, endocrine systems 3. pituitary gland - regulated by hypothalamus 4. pineal gland - secretes hormone melatonin (involved in circadian and seasonal rhythms)

Answer 164

-site of higher brain functions -each cerebral hemisphere divided into 4 lobes (parietal, temporal, frontal, occipital) -groove = sulcus -convolution = gyrus (raised parts) -degree of folding not related to higher processing

Answer 165

3 regions of cerebral gray matter: 1. basal ganglia - coordination of movement 2. limbic system - linking emotion/fear with higher cognitive functions 3. cerebral cortex

Answer 166

1. sensory areas - sensory input translated into perception (awareness) 2 motor areas - control skeletal muscles 3. association areas - integrate info from sensory and motor areas

Answer 167

-on ridge just anterior to central sulcus -cell bodies of descending 'upper' or 'first order' motor neurons

Answer 168

-on ridges just posterior to central sulcus -terminals of ascending sensory pathways from skin, musculoskeletal system, viscera (info about touch, pain, pressure, temperature, body position)

Answer 169

special senses have devoted regions (ex. visual cortex, auditory cortex)

Answer 170

developed the Montreal procedure -having patient lay awake and probed different area of their brain (mapped the brain) -burnt toast

Answer 171

stimulus -> receptor tranduces stimulus into intracellular signal (usually change in Em) -> APs travel along afferent neuron -> info reaches subcorticol integrating/relay centres (thalamus, medulla) -> information reaches appropriate regions in cortex (only becomes conscious when processing reaches cortex)

Answer 172

1. free nerve endings - cutaneous receptors for pain, temp, crude touch 2. receptors with nerve endings enclosed in connective tissue capsules - Pacinian corpuscle (vibration) 3. specialized receptor cell that release neurotransmitter onto sensory neuron - special senses, hair cell in inner ear

Answer 173

chemoreceptors - O2, pH, glucose, smell, taste mechanoreceptors - pressure (baroreecptors), cell stretch (osmoreceptors), vibration, acceleration, sound, touch photoreceptors - photons of light thermoreceptors - varying degrees of heat

Answer 174

each sensory receptor has an adequate stimulus... type of energy to which it best responds thermo - increased temp mechano - deformations of membrane that open ion channels photoreceptors - light

Answer 175

change in membrane potential

Answer 176

-somatosensory and visual neurons are activated by stimuli that fall within a certain physical area -at least 2 afferent neurons in pathway to CNS 1. first order (primary) sensory neuron - directly associated with stimuli 2. second order (secondary) sensory neuron - relays info from first neuron -receptive fields often determined by neurons further up the pathway (sensory input can then be gathered by more than one primary sensory neuron) -several primary neurons converge into a secondary neuron -convergence allows summation (creates larger receptive fields)

Answer 177

no 2-point discrimination: -2 stimuli fall within same receptive field and only 1 signal goes to the brain = perceived as a single point -smaller receptive fields = better 2 point discrimination (activate different pathways to the brain and perceived as distinct stimuli)

Answer 178

-olfactory pathways from nose projected through olfactory bulb to olfactory cortex -most sensory pathways (hearing, taste, vision, somatic) project to thalamus which modifies and relays info to cortical centres -equilibrium pathways project primarily to the cerebellum (some to thalamus) -visceral sensory info most integrated in brain stem and spinal cord (usually does not reach conscious processing)

Answer 179

CNS must be able to decode: -type of stimulus: modality -location -intensity -duration

Answer 180

adequate stimulus for that receptor type -> brain associates information from that receptor type with that modality ex. touch receptors - perceived as touch

Answer 181

-location is coded according to which receptive fields are activated (touch receptors in specific part of body project to certain area in somatosensory cortex) -special senses are different (ex. hair cells respond to different frequencies but no receptive fields relating to location of sound source)

Answer 182

-primary neuron response is proportional to stimulus strength -pathway closest to the stimulus inhibits neighbours -inhibition of lateral neurons enhances perception of stimulus (better localization)

Answer 183

1. # of receptors activated (population coding) -different thresholds for stimulation among groups of receptors -with low intensity stimulus most sensitive (lowest threshold) receptor recruited first -as stimulus intensifies, more receptors activated 2. frequency of APs coming from individual receptor cells -frequency of APs increases with stimulus intensity until a max. is reached

Answer 184

-receptor potential strength and duration vary with stimulus -receptor potential is integrated at the trigger zones -duration of a series of APs is proportional to duration of the stimulus -neurotransmitter release varies with pattern of APs arriving at the axon terminal -some receptors adapt to sustained stimuli 1. tonic receptors - slowly adapting, respond throughout stimulus 2. phasic receptors - rapidly adapt to a sustained stimulus and turn off

Answer 185

cutaneous sensory receptor location: superficial receptive field: small adaptation: slow (tonic) function: sustained touch/pressure, texture

Answer 186

cutaneous sensory receptor location: superficial receptive field: small adaptation: fast (phasic) function: beginning and end of fine touch/pressure

Answer 187

cutaneous sensory receptor location: deep receptive field: large adaptation: slow (tonic) function: sustained gross touch/vibration/stretch

Answer 188

cutaneous sensory receptor location: deep receptive field: large adaptation: fast (phasic) function: beginning and end of gross touch/vibration

Answer 189

cutaneous sensory receptor location: variable receptive field: variable adaptation: variable function: pain, temperature, hair movement

Answer 190

-found in many tissues (not just skin) -"pain" is a sensation rather than a stimulus -nociception is mediated by free nerve endings expressing ion channels that respond to a variety of strong stimuli (chemical/mechanical/thermal) -pain (eg. due to tissue injury) is mediated via release of local chemicals (K+, histamine, prostaglandins, serotonin, substance P): can either directly activate nociceptors or sensitize them (inflammation) -mediated by Transient Receptor Potential (TRP) channels

Answer 191

-mediate a wide variety of sensations including pain, heat/warmth, cold, some tastes, pressure, vision, osmotic pressure, stretch -relatively non-selective ion channels

Answer 192

-information from nociceptors can follow many different pathways 1. spinal reflexes 2. ascending pathways to cerebral cortex (info also sent to limbic system and hypothalamus) *emotional reactions *autonomic responses (sweating, vomiting, nausea) -different types of pain travel on different fibre types

Answer 193

1. alpha motor neurons = fastest -myelinated -diameter = largest -function: innervates extrafusal muscle fibres, afferent from muscle spindle, afferent from Golgi tendon organ 2. cutaneous mechanoreceptors (fine touch) -myelinated -diameter = medium 3. free nerve endings of crude touch/pressure, fast pain, temp and innervates intrafusal muscle fibres (gamma) -myelinated -diameter = small 4. slowest = slow pain, itch, temp -unmyelinated -diameter = small

Answer 194

1. according to effector -skeletal muscle (controlled by somatic motor neurons) -smooth and cardiac muscle, glands, adipose tissue (controlled by autonomic neurons) 2. according to integrating centre -spinal reflexes, 'cranial' reflexes 3. innate (inborn) vs. conditioned (learned) 4. number of neurons in pathway -monosypnaptic (only afferent and efferent neurons): somatic motor reflexes only -polysynaptic (eg. autonomic reflexes, involving interneurons)

Answer 195

-some are spinal reflexes (can often be modulated via signals from higher centers and inhibition by higher centres can be a learned response) -others integrated in the brain (hypothalamus, thalamus, brain stem) -emotional stimuli can be converted into visceral responses

Answer 196

-monitor: proprioception (position of limbs in space relative to other body parts) and effort exerted in lifiting/holding objects -integrating centre = CNS (via networks of excitatory or inhibitory neurons) -efferent pathway: somatic motor neurons (alpha motor neurons) -effectors: contractile skeletal muscle fibres (extrafusal muscle fibres)

Answer 197

-receptors that sense changes in joint movements, muscle length, muscle tension, and send info the CNS -depending on appropriate response, CNS activates motor neurons to make motor units contract or activates inhibitory interneurons to make muscles relax -examples of proprioceptors: muscle spindles (muscle stretch), Golgi tendon organs (muscle tension), joint receptors (distortions as bones are repositioned)

Answer 198

-each spindle consists of 3-12 intrafusal muscle fibres (arranged in parallel to extrafusal muscle fibres) -most sensitive to muscle stretch (increased length) -tonically active, sending stream of APs even at rest -mediate stretch reflexes (introduces contraction when muscle is stretched, tends to maintain muscle at constant length) -unloaded when muscle shortens unless tightened up by intrafusal muscle fibres (alpha-gamma coactivation) -alpha MN innervates extrafusal -gamma MN innervates intrafusal

Answer 199

-muscle stretched -increased firing from sensory neuron associated with spindle -increased firing of alpha motor neuron to biceps -biceps contracts -increased firing of inhibitory interneuron -decreased firing of alpha motor neuron to triceps (reciprocal inhibition) -antagonist muscle relaxes

Answer 200

-between fibres and tendon (in series with muscle fibres) -whether isotonic or isometric, contraction of muscle causes tendon and GTO to stretch (most sensitive to isometric contraction) -relatively insensitive to muscle stretch -monitors tension (force of contraction)

Answer 201

1. stretch reflex (sensor: muscle spindle - change in length) -maintenance of posture -positional info to CNS (usually includes reciprocal inhibition) 2. monitoring muscle tension (sensor: Golgi tendon organ) -eg. maintaining constant grip on a paper cup 3. withdrawal reflex (sensor: pain receptors) -get away from pain, ideally while maintaining posture and balance (usually involves reciprocal inhibition and crossed extensor reflex)

Answer 202

1. muscle reflex -primarily driven by external stimuli -inherent (vs. learned), rapid -mostly handled at the level of the spinal cord and brain stem with modulation by higher centres 2. voluntary movement -most complex, integrated in cerebral cortex -learned movements can improve with practice (become subconscious)

Answer 203

1. sensory inputs- sensory cortex, motor cortex 2. planning and decision making- prefrontal cortex, motor association areas, basal ganglia, thalamus 3. coordination and timing- input from cerebellum 4. execution- corticospinal tract to skeletal muscles 5. execution- brain stem, spinal cord 6. continuous feedback to sensory cortex

Answer 204

-results from death of dopamine secreting neurons in a particular region of basal ganglia -motor symptoms include tremor at rest, slowness of movement, rigidity (increased muscle tone) and many non-motor effects -main treatment is replacing dopamine with L-dopa (able to cross the blood-brain barrier

Answer 205

-the only sensory modality that does not go through the thalamus; does not cross the midline -the only special sense for which the sensory cell itself is the neuron that carries the info to the CNS -much more important in other species than humans (closely linked with taste and emotion/memory)

Answer 206

-bipolar neurons (replaced every ~60 days) -dendrites end in non-motile cilia which express odorant receptor proteins -axons go through gaps in cribiform plate; synapse on 2nd order neurons -odorant receptor proteins are GPCRs, form one of the largest gene families in vertebrates (3/5% of genome) (1000s of different types of receptors)

Answer 207

-each ORN expresses only one type of odorant receptor protein BUT -each receptor can recognize more than one odorant -each odorant can stimulate more than one receptor -subsequent processing en route to olfactory cortex (input of 100s of olfactory neurons in combination is then interpreted as a particular odour)

Answer 208

-small organic compounds that are simple enough to go up in the air -different sturctures have different odours

Answer 209

combination of 5 basic tastes: 1. sweet (carbs -> energy) 2. sour (H+) 3. salty (Na+) 4. bitter (many compounds -> possible toxicity) 5. umami (glutamate, some nucleotides -> protein) -taste receptor cells are non-neural epithelial cells (frequently come into contact with chemicals so replaced every 10 days)

Answer 210

-number of taste buds per papillae depends on type (circumvallate, foliate, fungiform) can be 1000-2000 -each taste bud contains 50-150 taste receptor cells -supporting epithelial cell secrete fluid into lumen of taste pore

Answer 211

-we can taste all flavours around our tongue, but some tastes more concentrated in certain areas

Answer 212

1. ligands activate TRCs 2. various intracellular pathways are activated 3. Ca2+ signal triggers exocytosis (sour H+) or ATP formation (sweet, bitter, umami) 4. neurotransmitter (sour H+) or ATP (sweet, bitter, umami) released 5. primary sensory neuron fires; APs sent to the brain -sweet, bitter, umami ligands believed to be GPCRs -ultimately release ATP as signal molecule

Answer 213

1. taste info travels through many cranial nerves to medulla 2. thalamus 3. gustatory complex

Answer 214

1. normal position = some ion channels open, tonic rate of APs 2. bent to the right = more ion channels open, cation entry depolarizes cell, increased frequency of APs 3. bent to the left = channels closed, less cation entry hyperpolarizes cell, no APs

Answer 215

-pattern in air pressure (amplitude and frequency) -amplitude = volume -frequency = pitch

Answer 216

1. sound wave strike tympanic membrane and become vibrations 2. sound wave energy is transferred to the 3 bones of the middle ear (malleus, incus, stapes) which vibrate 3. the stapes is attatched to the membrane of the oval window. Vibrations of the oval window create fluid waves within the cochlea 4. the fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter release 5. neurotransmitter release onto sensory neurons creates APs that travel through the cochlear nerve to the brain 6. energy from the waves transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear and the round window

Answer 217

-perilymph (similar to plamsa- high Na+, low K+) -endolymph (similar to ICF- low Na+, high K+) -cochlear duct contains the Organ of Conti (sensory hair cells and support cells)

Answer 218

-sound wave trigger activity at different places along the cochlea's basillar membrane and are perceived as different pitches 'tonographic map' *waves travel along cochlea, hair cells in areas that bend the most at a given frequency encode that pitch *'labelled line' based on which hair cells are stimulated -this explanation based on the anatomy of the ear -dominated for over 100 years -distance from stapes (farther = low frequency)

Answer 219

-frequency of sound wave determines frequency of APs travelling along auditory nerve, perceived as pitch (location along basillar membrane irrelevant) -eg. low frequency -> slow waves along basillar membrane -> low firing rate of primary sensory neurons -> perceived as low pitch sound -problem: we can hear pitches at 20,000 Hz but we cannot transmit APs at this frequency

Answer 220

-groups of neurons working as a team (with staggered firing rates) carry the temporal code *pooled neural response interpreted as pitch -place coding also plays a role (which region hair cells along the basillar membrane are stimulated) -relative importance of place and temporal coding depends on pitch (low pitches -> temporal coding, high pitches -> place coding)

Answer 221

1. primary auditory neurons project from the cochlea to the medulla 2. from the medulla, secondary sensory neurons project to 2 higher nuclei (one ipsilateral - on the same side of the body and one contralateral - on the opposite side). Splitting info into 2 ascending tracts means that each side of brain receives info from both ears 3a. ascending tracts synapse in midbrain and thalamus before projecting to the auditory complex 3b. collateral pathways take info to cerebellum and reticular formation 4. brain accounts for time difference between sides to create 3D representation of sound source (tell which side sound is coming from)

Answer 222

1. conductive -no transmission through either external or middle ear (issues with wax or fluid in middle ear- can usually be repaired) 2. central -damage to neural pathways between ear and cerebral cortex or damage to the cortex itself (ex stroke) -uncommon 3. sensorineural -damage to structures of inner ear -eg. death of hair cells due to loud noise -common in youth and elderly -hair cells cannot yet be replaced in mammals

Answer 223

1. dynamic component - movement of the body through space 2. static component - position of head -integrated with info from other sensory systems (muscle + joint proprioceptors and vision) -like hearing, detected by hair cells lining fluid-filled (endolymph) chambers * otolith organs- utricle, saccule -> linear acceleration and head position * 3 semicircular canals- rotational acceleration (superior, posterior, horizontal)

Answer 224

1. cristae are sensory receptors for rotational acceleration -hair cells grouped in cristae, within ampulla of canals -movement of endolymph pushes on the gelatinous capula and activates hair cells 2. macula are sensory receptors for linear acceleration and head position -otoliths are crystals that move in response to gravitational forces

Answer 225

1. vesitbular hair cells are tonically active and release neurotransmitter into primary sensory neurons of the vestibular nerve 2a. sensory neurons either synapse in medulla (vestibular nuclei) or continue to cerebellum (primary site for equilibrium processing) 2b. collateral pathways run from the medulla to the cerebellum or upward through the reticular formation and thalamus

Answer 226

1. light enters the eye and the lens focuses light onto the retina 2. photoreceptors of retina tranduce light into electrical signals 3. neural pathways from retina to brain process electrical signals into visual images

Answer 227

1. optic nerve 2. optic chiasm 3. optic tract 4. thalamic relay 5. visual cortex (occipital lobe)

Answer 228

-control of pupil diameter according to intensity of light -autonomic 'reflex' 1. detector: photoreceptors in retina (not rods and cones) 2. afferent: afferent neurons travelling in optic nerve 3. integrating centre: thalamus/brain stem (midbrain) 4. efferent: motor neurons travelling in oculomotor nerve 5. effectors: smooth muscles regulating pupil diameter a) circular (sphincter) = constriction (PNS) b) radial = dilation (SNS)

Answer 229

-conversion of light into changes in membrane potential by photoreceptor cells in the retina -photoreceptors = rods and cones -modified ganglion cells (mediate pupillary light reflex, circadian/seasonal rhythms): non-visual responses to light

Answer 230

-there are 2 opportunities to cross: 1. optic chiasm 2. midbrain -contraction of the same eye that received light = ipsilateral response -contraction of the opposite eye that received light = consenual response

Answer 231

-both rods and cones -rod vision = high convergence (good sensitivity to low light but poor resolution) -biploar cells -ganglion cells

Answer 232

-ALL cones -low convergence (high resolution, small receptive fields, low sensitivity- not good for low light) -biploar neurons -ganglion cells

Answer 233

1. dark: rhodopsin inactive, cGMP high, CNG and K+ channels open = tonic release of glutamate onto bipolar neurons 2. light: activated opsin, cGMP decreases, closes CNG channels, cell hyperpolarized = glutamate decreases in proportion to amount of light (less neurotransmitter) 3. in the recovery phase, retinal binds with opsin

Answer 234

thoracic and lumbar segments of spinal cord in grey matter

Answer 235

cranial and sacral segments of the spinal cord

Answer 236

filtering all then excreting selected solutes is easier because there isn't a need for specific transport mechanisms -able to happen quickly

Answer 237

1) regulation of ECF volume and blood pressure 2) regulates plasma osmolarity (Na+,CL-) 3) regulates ion balances 4) excretion of waste 5) regulates plasma pH 6) endocrine

Answer 238

1. fluid moves from plasma into nephrons (hollow tubules) in the kidneys 2. nephrons modify the composition of the fluid as it passes through 3. modified fluid leaves the kidneys and enters hollow tube called ureter 4. ureters lead from kidney to bladder 5. bladder fills and expands until it conracts and expels urine through a single tube called urethra

Answer 239

renal artery smaller arteries 1) afferent arteriole 2) glomerulus (capillaries) 3) efferent arteriole 4) peritubular capillaries 5) vasa recta (juxtamedullary only)

Answer 240

cortex: -all Bowman's capsules -PCTs -DCTs medulla: -Loop of Henle -collecting ducts

Answer 241

renal corpuscle (Bowman's capsule + glomerulus) proximal tubule descending limb Loop of Henle ascending limb distal tubule collecting duct to bladder

Answer 242

artery -> capillary -> vein -> capillary -> vein -> heart nephrons have 2 capillary beds (glomerulus capillaries and pertitubular capillaries)

Answer 243

jutaglomerular nephrons go through vasa recta

Answer 244

abdominal aorta -> renal artery -> branches of smaller arteries -> 1. afferent arterioles -> 2. glomerulus (capillaries) -> 3. efferent arteriole -> 4. peritubular capillaries/ 5. vasa recta -> venules -> veins -> renal vein -> vena cava

Answer 245

-kidneys process over 180 L plasma/day but only 1.5 L secreted - 99% of fluid is reabsorbed 1) filtration 2) reabsorption 3) secretion

Answer 246

movement of water/solute from blood into tubules -occurs in renal corpuscles -once in tubules, filtrate will be excreted if not reabsorbed

Answer 247

movement of water/solute from filtrate back into blood (peritubular capillaries)

Answer 248

removing molecules from blood, adding them to filtrate -much more selective than filtration

Answer 249

only at the glomerulus -blood to lumen

Answer 250

filtration, reabsorption and secretion amount of solute excreted = amount filtered - amount reabsorbed + amount secreted

Answer 251

-filtrate is almost identical to plasma in composition (isoosmatic with plasma, Na+ Cl-) -minus blood cells and most of the protein

Answer 252

-70% of filtrate and solute is reabsorbed in proximal tubule (iso-osmotic reabsorption) -fluid leaving ascending Loop of Henle is hypo-osmotic relative to plasma (at this point 90% of fluid has been reabsorbed) -distal tubule/collecting duct: "fine tuning" of water-salt balance (endocrine control)

Answer 253

~20% of the plasma moves out of glomerular capillaries into tubules (the rest exits in the efferent arteriole)

Answer 254

% of total plasma volume that filters into tubule

Answer 255

modifies tubular epithelium -macula densa cells release paracrine factors that act on smooth muscle of afferent arteriole

Answer 256

1) endothelium of glomerular capillaries -"fenestrated": allow most substances to pass -exceptions: cells (too big) and most proteins (repelled by negatively charged proteins on pore surfaces) 2) basement membrane -layer of ECM between capilary endothelium and epithelium of Bowman's capsule *collagens, other proteins (negatively charged) *acts as a course sieve, keeping most proteins in plasma 3) epithelium of Bowman's capsule -gaps between foot processes of podocytes leave narrow slits closed by semi-porous membrane

Answer 257

1) continuous -most common -muscle, neural tissue, connective tissue -tight junctions, intracellular clefts 2) fenestrated -kidney, intestine -fenestrations, tight junctions 3) sinusoid -no basement membrane -bone marrow, lymph nodes, liver, spleen

Answer 258

hydrostatic pressure = pressure that forces fluid out of the capillary (ie. blood pressure) colloid osmotic pressure = pressure of proteins within the capillary that pulls fluid into the capillary filtration = hydrostatic pressure > colloid osmotic pressure reabsorption = hyrostatic pressure < colloid osmotic pressure net pressure = hyrsotatic pressure - colloid osmotic pressure

Answer 259

Pfluid= fluid pressure created by fluid in Bowman's capsule net filtration pressure = Ph - colloid osmotic pressure - Pfluid -net driving force is low, but combined with leakiness of the barrier, filtration rate is HIGH -glomerular filtration rate (GFR) = 180 L/day; plasma volume is ~3L

Answer 260

-net filtration pressure -"filtration coefficient" *surface area of glomerular capillaries *permeability of the interface *note parallels with gas exchange in alveoli (partial pressure, surface area, thickness/permeability of barrier) -would expect glomerular filtration be heavily influenced by changes in Ph (blood pressure) BUT GFR relatively constant over wide range of BPs *kidneys are good at auto-regulating

Answer 261

1) increase resistance of afferent arteriole (vasoC) -decrease renal blood flow, decrease Ph, decrease GFR 2) increase resistance of efferent arteriole (vasoC) -decrease renal blood flow BUT increase Ph and GFR

Answer 262

-primarily regulated by altering renal blood flow via changes in resistance of afferent arteriole multiple mechanisms: 1) myogenic response: 'autoregulation' -instrinsic response of arteriolar smooth muscle to pressure changes (vasoC in response to increase BP more effective in normalizing GFR than vasoD in response to decrease BP) -similar to autoregulation in other systemic arterioles (also important in the brain) 2) tubuloglomerular feedback -flow through tubule influences GFR -involves juxtaglomerular apparatus 3) endocrine and autonomic control -changing resistance in arterioles -altering filtration coefficient

Answer 263

-modification of both tubule and arteriolar walls where they come into contact with each other *modified tubular epithelim -> macula densa *modified arteriolar wall -> specialized smooth muscle cells called granular cells (aka JG) -granular cells secrete renin +involved in salt/water balance -macula densa cells release paracrine factors that act on smooth muscle of the afferent arteriole

Answer 264

1) increase GFR (ie. increase BP) 2) increase flow though tubules 3) increase flow of NaCl past macula densa 4) paracrine signal from macula densa acts on afferent arteriole 5) afferent arteriole constricts -decrease renal blood flow -decrease Ph -decrease GFR

Answer 265

-due to the importance of kidneys in homeostatic regulation of blood pressure, integrating centres outside the kidney can override local control 1) autonomic effects on GFR: -via SNS innvervation of afferent & efferent arterioles -moderate SNS activity has little effect on GFR *extreme conditions (ie. bleeding,severe dehrydation) : sharp drop in Bp -> SNS vasoC -> decreae GFR 2) endocrine effects: -AgII -> potent vasoconstrictor -prostaglandins -> vasodilators *both can also affect filtration coefficient through actions on podocytes(alters size of slits) and mesangial cells (shape of glomerular capillaries)

Answer 266

increased renin secretion

Answer 267

filtration removes foreign / toxic substances in addition to endogenous material -high rate of filtration clears these substances quickly -setting the default to 'filtered -> excreted' makes it easy to clear solutes without specific transport mechanisms

Answer 268

filtrate in capsule has same [solute] as interstitial fluid (ICF) -to reclaim solute, tubular cells must create gradients (chemical or electrical) by active transport pump Na+out of tubule into interstitium anions follow water follows -loss of water from tubule remaining solute in tubular fluid @ higher conc (K+, Ca2+, urea) these solutes move into interstitium (if tubular epithelial cells are permeable to them)

Answer 269

1) Na+ reabsorbed (tubule -> ICF) by active transport 2) Electrochemical gradient created drives anion reabsorption 3) H2O moves by osmosis, following solute reabsorption into ICF -concentrations of other solutes in the tubule increase as fluid volume decreases 4) Permeable solutes are reabsorbed by diffusion through membrane transporters or paracellular pathway

Answer 270

1) paracellular pathway -through cell-cell junctions (tight junctions aren't that tight- can sneak through) 2) epithelial (trans-cellular) transport -can be regulated -crossing apical and basolateral membranes of epithelial cells -mechanism depends on driving force *down gradient-'leak' channels or facilitated diffusion *against gradient- primary or indirect active transport -Na+ directly or indirectly involved in most transport, both passive and active

Answer 271

1) Na+ enters cell through various membrane proteins (ENaC), moving down its electrochemical gradient 2) Na+ pumped out basolateral side of cell by Na+/K+-ATPase. -net result: Na+ reabsorption across tubular epithelium

Answer 272

ENaC= epithelial sodium channel -expressed in apical membranes of epithelial cells (especially kidney) -expression / activity regulated in some regions of nephron *major role in Na+and K+homeostasis (target of many diuretics)

Answer 273

1) Na+moving down its electro-chemical gradient uses SGLT transporter to pull glucose into the cell against its concentration gradient. 2) glucose diffuses (facillitated diffusion) out basolateral side of cell using GLUT protein. 3) Na+pumped out by Na+/K+-ATPase -same basic mechanism responsible for reabsorption of amino acids, lactate, Krebs cycle intermediates, phosphate, sulphate, ... *apical symporter + basolateral facilitated diffusion carrier or ion exchanger

Answer 274

-urea has no transporters in proximal tubule but can move across membrane passively down its gradient -up to 40% of filtered urea reabsorbed in proximal tubule 1) Na+ and other solutes absorbed at proximal tubule 2) water follows by osmosis 3) water loss results in higher [urea] 4) urea moves passively out of tubule through epithelial cells into ICF

Answer 275

relative permeability (high -> low) 1. hydrophobic molecules (O2, CO2, N2) 2. small polar uncharged molecules (H2O, urea) 3. large polar uncharged molcules (glucose, fructose) 4. ions (K+, Cl-, Na+)

Answer 276

~40% of the filtered urea is reabsorbed in the proximal tubule About urea: *formed from ammonia, product of AA metabolism *small, neutral, neither acidic or basic, non-toxic *handy to have around ... -key intermediate in nitrogen metabolism (urea cycle) *kidney doesn't have much choice, since urea movement is passive

Answer 277

[protein] in urine are usually very low but kidney is major route of 'elimination' of small proteins

Answer 278

serum albumin (~55% of total plasma protein) globulins (~38%) fibronogen (~7%) size = > 50 kDa (BIG)

Answer 279

-depends on size, charge, conformation of protein -general cut-off is 50 kDa proteins < 50 kDa are filtered small proteins: glycoprotein hormones - FSH, LH, hCG many protein hormones- insulin, GH

Answer 280

1) proteins / complex polypeptides: -exocytosis through apical membrane then leave as AA's out of the basical membrane into the ICF -enter vasculature as AA's 2) small, linear peptides -break down into AA's and enter apical membrane and leave as AA's

Answer 281

most renal transport involves membrane proteins -exhibit specificity, competition, and saturation transport maximum (Tm) = transport rate at saturation renal threshold = plasma [substrate] at which Tm (saturation) occurs *need to keep concentrations of substrates that need to be brought back into the blood below the renal threshold

Answer 282

-you can filter any volume of blood glucose -you can only reabsorb a certain amount of glucose (renal threshold) -if plasma [glucose] is normal, it falls below renal threshold so all glucose is reabsorbed -in people with diabetes melitus plasma [glucose] is above renal threshold so not all glucose is reabsorbed (SLGT is saturated) and some is excreted in urine -excretion = filtration - reabsorption

Answer 283

-lower hydrostatic pressure (blood pressure) in peritubular capillaries results in net reabsorption of ICF

Answer 284

1) small protein/peptide hormones from peritubular capillaries taken up by epithelial cells of proximal tubule (e.g. insulin) -requires receptor on basolateral face of epithelial cells 2) K+and H+secreted by epithelial cells of distal nephron -major means of their homeostatic regulation 3) many organic compounds secreted by proximal tubule -endogenously produced metabolites, xenobiotics *secretion of organic compounds is active process (typically secreted across proximal tubule epithelium by indirect active transport)

Answer 285

1) Direct active transport. The Na+/K+ATPase keeps intracellular [Na+] low 2) Secondary inactive transport. NaDC cotransporter concentrates dicaroboxylate inside the cell using energy stored in [Na+] gradient 3) Teritary indirect active transport. Basolateral OAT transporters concentrates organic anions (OA-) inside cell, using energy stored in dicarboxylate gradient. 4) Organic anions enter the lumen of tubule by facilitated diffusion

Answer 286

Na+-dicarboxylate cotransporters -on both apical and basolateral membranes -dicarboxylates-two carboxyl groups (citrate-, oxaloacetate-, αKG-, krebs cycle intermediates)

Answer 287

OAT = organic anion transporters -able to transport range of anions *endogenous -bile salts, cyclic nucleotides, ... *exogenous -benzoate, salicylate, saccharine, penicilli

Answer 288

-compounds that compete with drugs for OAT transporter will slow that drug's clearance from the blood *used during WWII to extend limited supplies of penicillin -led to development of probenecid (early 1950s) -current uses of probenecid: *antibiotic-sparing agent in severe infections (also works for certain antivirals) *prevent nephrotoxicity for certain drugs *masking agent (on anti-doping list)

Answer 289

excretion = filtration - reabsorption + secretion

Answer 290

composition of urine versus original filtrate: *glucose, amino acids, other useful metabolites gone *proteins mostly gone *waste products much more concentrated -water and ions variable depending on needs

Answer 291

1) GFR - indicator of overall kidney function 2) details of renal handling is required for drug approval

Answer 292

"the rate at which a substance X disappears from the body by excretion or metabolism" clearance rate (mL/min) = excretion rate of X (mg/min)/[X] in plasma (mg/mL)

Answer 293

inulin clearance = GFR inulin: -storage carbohydrate from roots of many plants 'soluble fibre' -all the inulin filtered at glomerulus ends up being excreted (none reabsorbed or secreted)

Answer 294

100-125 mL/min

Answer 295

can be used to estimate GFR -endogenous substitution for inulin -freely filtered, some secreted, none reabsorbed

Answer 296

-with 1) GFR, 2) its plasma concentration and 3) its excretion rate, can determine how the kidney handles any solute filtered load of X = [X] in plasma x GFR -compare filtered load with excretion rate: less in urine than was filtered? net reabsorption more in urine that was filtered? net secretion *e.g.glucose *filtered load is 125 mg glucose / min; none in urine *conclusion: all reabsorbed

Answer 297

100% of filtered inulin is excreted

Answer 298

No glucose is excreted (100% reabsorbed) -when would it not be 0? SLGT saturation, plasma [glucose] above renal threshold

Answer 299

50% is excreted Would you expect urea clearance to be lower or higher than GFR? -can never be higher, always expect some clearance

Answer 300

more excreted than was filtered How can penicillin clearance be higher than GFR? -in addition to being filtered you also secrete more in

Answer 301

*filtrate (now urine) can no longer be modified once it leaves collecting ducts *opening between bladder and urethra guarded by two sphincters -internal -smooth muscle (continuation of bladder wall) -external -skeletal muscle *tonic stimulation from CNS keeps it closed most of the time *micturition is simple spinal reflex, but subject to both conscious and unconscious control from CNS -bladder fills -> activates stretch receptors -> afferent information travels to spinal cord *activates two sets of neurons -parasympathetic: acts on smooth muscle of bladder -somatic: inhibits motor neurons to external sphincter

Answer 302

-internal sphincter passively contracted -external sphincter stays contracted via tonic discharge from CNS

Answer 303

1) stretch receptors fire 2) parasympathetic neurons fire. Motor neurons stop firing (tonic discharge inhibited) 3) smooth muscle contracts. Internal sphincter passively pulled open. External sphincter relaxes

Answer 304

water gain: -food and drink (2.2L) -metabolism (0.3L) water loss: -insensible water loss: skin and lungs (0.9L) -urine (1.5L) -feces (0.1L)

Answer 305

can conserve water but cannot replace lost water -volume loss can be replaced only by volume input from outside the body -volume gain = drinking -GFR can be adjusted -regulated H2O reabsorption -kidneys conserve water -if water volume falls too low GFR stops

Answer 306

*osmolarity of urine is indicator of how much water is being excreted by the kidneys -to eliminate excess water: -50 mOsM *diuresis, diuretics -to conserve water" -1200 mOsM(human) *agents that promote water conservation = antidiuretics *changes in osmolarity (therefore water loss vs conservation) achieved by varying amt of water and Na+ reabsorbed in distal nephron (distal tubule and collecting duct) 1) to produce dilute urine: reabsorb solute without letting water follow 2) to concentrate urine: reabsorb water but leave solute in tubules

Answer 307

1) 'leaks' through lipid bilayer -happens in most cells but doesn't explain the rapid movement through some cells 2) travels through 'water channels' aquaporins (Nobel Prize 2003) -13 different aquaporins in mammals (so far) *6 of them expressed on apical or basolateral surfaces of epithelial cells in various regions of renal tubules

Answer 308

1) produce dilute urine: reabsorb solute without letting water follow?? *epithelial cells that transport solutes but are impermeable to water -reduced expression of aquaporins = less water reabsorbed 2) produce concentrated urine: reabsorb water but leave solute in tubules?? *make epithelial cells (and surrounding interstitium) more saltythan tubular fluid AND *make tubular epithelial cells highly permeable to water -accomplished in renal medulla, by juxtamedullar nephrons *high osmolarity of medullary interstitium allows urine to become concentrated as it flows through collecting duct

Answer 309

1) iso-osmotic fluid leaving proximal tubule becomes progressively more concentrated in descending limb. 2) removal of solute in thick ascending limb creates hyposmotic fluid. 3) permeablilty to water and solutes is regulated by hormones. 4) urine osmolarity depends on reabsorption in collecting duct.

Answer 310

permeability of distal nephron to water is regulated -via hormone-induced changes in expression of aquaporinson apical surface -basis of cellular responses to hyper/hypotonic environments known by various names: *antidiuretichormone, ADH -prevents diuresis -> conserves water *vasopressin, arginine vasopressin, AVP -named for 'pressor' (vasoconstrictive) effect (even though there is no pressor effect at physiological concentrations ...)

Answer 311

AVP causes insertion of aquaporins into apical membrane 1) AVP binds to membrane receptor 2) receptor activates cAMP messenger system 3) AQP2 inserted into apical membrane. 4) water absorbed by osmosis into the blood aquaporins added to plasma membrane by exocytosis and removed by endocytosis: "membrane cycling"

Answer 312

AVP synthesized by 'magnocellular' neurons in supraoptic nucleus of hypothalamus 1) AVP is made and packaged in cell body of neuron 2) Vesicles are transported down the cell.. 3) Vesicles containing AVP are stored in posterior pituitary. 4) AVP is released into blood.

Answer 313

increased plasma osmolarity decreased blood volume/pressure

Answer 314

1) affects cell size/volume - physical integrity of cells and tissues 2) affects ionic strength - activity of macromolecules

Answer 315

(normal variation 1-3%) 1) variations in water intake / water loss 2) variations in Na+ intake / Na+ excretion

Answer 316

too much salt (e.g. ingestion of salt to induce vomiting) = seizures, death too much water -hypo-osmolarity (e.g. excessive voluntary drinking, compulsive drinking, accidental overhydration in hospital) = headache/ nausea/ vomiting -> mental confusion -> seizures -> coma ->death

Answer 317

plasma osmolarity monitored by stretch-sensitive neurons (mechanoreceptors) that increase firing rate as osmolarity increases *stimulated by "cellular dehydration"

Answer 318

*oropharyngeal cavity (back of mouth/ throat) *within blood vessels that collect solutes absorbed from intestines *How do we know there are peripheral osmoreceptors? -Water intake satisfies thirst long before ECF hyperosmolarity is fully corrected. -Gastric water loading lowers AVP release long before plasma osmolarity decreases. *peripheral osmoreceptorscan detect osmotic strength of ingested materials and induce anticipatory responses *however, central osmoreceptorsare the major points of regulation

Answer 319

*circumventricular organs (around ventricles) -organum vasculosum laminae terminalis (OVLT) -subfornicalorgan (not shown) *supraopticnucleus in hypothalamus (SON; origin of AVP-secreting neurons)

Answer 320

lack of nocturnal rise in AVP -> failure to concentrate urine -> output of high volume/dilute urine -> bedwetting

Answer 321

desmopressin

Answer 322

key to producing concentrated urine is high osmolarity of medullary interstitium -creates osmotic gradient for reabsorption of water Why doesn't osmolarity of interstitium decrease as water is drawn out of tubules?? -related to anatomical arrangement of loop of Henleand associated vasculature, vasarecta *arterial and venous vessels traveling very close to each other, with fluid moving in opposite directions *allows transfer from one vessel to another -"countercurrent exchange system"

Answer 323

1) filtrate in descending limb becomes progressively more concentrated as it loses water 2) blood in vase recta removes h2o leaving loop of henle 3) ascending limb pumps out Na+, K+, Cl- filtrate becomes hyposmotic descending limb - permeable to water but doesn't trnasport ions ascending limb - impermeable to water but pumps Na, K, an Cl out of tubules

Answer 324

1) 1200 mOsm entering ascending loop 2) salt reabsorption (NKCC symporter) 3) water cannot follow solute 4) 100 mOsm leaving loop NKCC symporter: -expressed on apical membrane -moves Na+, K+, 2 Cl- -secondaryactive transport K+and Cl-leave basolateral side via cotransporters or open channels -inhibition of NKCC transporter is target of 'loop diuretics'

Answer 325

the two limbs of the loop of Henle are inter-dependent: *salt is pumped out of ascending limb *salty interstitium draws water out of descending limb *as water leaves descending limb, tubular fluid becomes more concentrated, making it easier for ascending limb to pump out salt *which draws more water out of descending limb ...

Answer 326

*typical North American diet, 9 g NaCl per day consumed -if kidneys weren't clearing any salt, would need to take in 1.1 L extrawater per day just to maintain normal [Na] in ECF *would result in major gain in ECF volume = effects on blood pressure! -if no water ingested to offset Na intake, unacceptable increase in [Na] in ECF -> hyperosmolarity->cell shrinkage ->etc *kidneys responsible for most Na excretion -loss via feces, sweat normally minimal exceptions: vomiting, diarrhea, heavysweating Note: Na+regulated, but not Cl- -Cl-normally follows Na+ -via electrochemical gradient -via NKCC, NaClsymporters

Answer 327

recaps: *all Na+is filtered at the glomerulus *70% reabsorbed in proximal tubule (iso-osmotic, unregulated) *~25% reabsorbed in ascending loop of Henle(unregulated) *only reabsorption through the distal nephronis regulated -regulated by hormone aldosterone *aldosterone synthesized 'on demand' in adrenal cortex -acts via intracellular receptors *drives transcription of genes with upstream 'aldosterone response elements' synthesis of new proteins insertion of new pumps/channels modulation of existing pumps/channels

Answer 328

'Principal cells' within epithelium of distal nephron 1) aldosterone binds to cytoplasmic receptor 2) hormone receptor complex = transcription factor -> initiates transcription 3) new proteins, channels, and pumps synthesized 4) aldosterone-induced protein modulate existing channels and pumps 5) result in increased Na+ reabsorption and K+ secretion

Answer 329

at proximal tubule: *Na+reabsorption unregulated (ENac, Na/K-ATPase) -water reabsorption automatically follows by osmosis (proximal tubule always permeable to water) at loop of Henle: *Na+reabsorption (in ascending limb via NKCC) unregulated *water reabsorption (in descending limb) unregulated at distal tubule and collecting duct: *water reabsorption regulated by AVP insertion of aquaporins *Na+ reabsorption regulated by aldosterone *increased expression / activity of channels and pumps -apical channels -Na+import, K+export -basolateralpumps -Na/K-ATPase

Answer 330

*primary action of aldosterone is Na+ reabsorption (and K+secretion) two primary stimuli for aldosterone release: 1) increased plasma [K+] -monitored by cells in the adrenal cortex -aldosterone protects against 'hyperkalemia' 2) decreased blood pressure -involves a complex pathway

Answer 331

*only a small proportion (2%) of the K+ in our bodies is in ECF -mostly within cells *yet important to maintain ECF K+concentrations in narrow range -major determinant of resting membrane potential / excitability in excitable cells hyperkalemia: reduced concentration gradient, more K+stays in cell hypokalemia: greater concentration gradient, more K+leaves cell

Answer 332

1) angiotensingen - liver 2) renin - from kidneys (juxtaglomerular cells) 3) AgI (inactive) 4) ACE - in endothelium of blood vessels 5) AgII 6) aldosterone - made on demand in adrenal cortex 7) principal cells

Answer 333

*activated in response to low blood pressure *renin from kidney initiates pathway

Answer 334

1. granular (JG) cells themselves monitor blood pressure in afferent arteriole, release renin in response to decreased BP 2. paracrine feedback from macula densa cells in distal tubule -decreased flow rate = increased renin release (and vice versa) 3.s ympathetic pathways originating in cardio control centre in medulla terminate on granular cells -part of baroreceptor response to decreased BP

Answer 335

blocking angiotensin II is of great interest for treatment of hypertension -ACE inhibitors -angiotensin receptor blockers (antagonists) *fewer side effects than ACE inhibitors? -direct renin inhibitors (recently approved)

Answer 336

atrialnatriureticpeptide (ANP): *produced in specialized myocardial cells, mostly in atria *released when these atrial cells stretch more than normal oppose RAS

Answer 337

1) replacing water = thirst *sensors in hypothalamus -thirst triggered by: *hyper-osmolarity = shrinkage of osmoreceptors *angiotensin II acting on hypothalamus -act of drinking relieves thirst (i.e.before water is absorbed and osmolarity corrected) 2) replacing Na+: *low Na+ triggers salt appetite *linked to angiotensin II and aldosterone (and Na+balance)

Answer 338

similarity: *both trigger a 'low volume alarm' differences: *dehydration involves loss of more water than solute (sweat is hypotonic) -hyperosmolarity *hemorrhage involves equal loss of water and salt -no hyperosmolarity

Answer 339

*normal plasma pH 7.38-7.42, intracellular pH is similar -fluids 'outside' the body can have pH outside this range *GI tract, renal tubules, ... *H+concentration closely regulated -affects tertiary structure of proteins -> enzyme function *abnormal pH affects the nervous system acidosis -neurons become less excitable; CNS depression alkalosis -hyperexcitable; sensory changes, twitches, tetanus *pH disturbances are associated with K+disturbances -partly due to renal transporter, H+/K+-ATPase *antiporter,acidosis -excretes H+, reabsorbs K+ alkalosis -vice versa

Answer 340

-dealing with CO2 produced during aerobic respiration is the main source of acid in the body -reaction takes place in all cells and in plasma, but slowly *occurs very rapidly in some cells due to high levels of carbonic anhydrase CO2 + H2O <-> H2CO3 <-> HCO3- + H+

Answer 341

1) buffers -combine with or release H+ -first line of defence -cellular proteins, phosphate ions, hemoglobin, bicarbonate 2) ventilation -rapid response, second line of defence -corrects 75% of disturbances; can also cause them ... 3) renal regulation -slower, but highly effective -directly by excreting or reabsorbing H+ -indirectly by changing in the rate at which HCO3-is reabsorbed or excreted

Answer 342

-if plasma pH moves out of normal range, buffering has been overwhelmed, it is up to respiratory and renal mechanisms -if primary cause respiratory, only renal mechanisms remain -if primary cause metabolic, both respand renal mechanisms can be used

Answer 343

hypoventilate: *reaction shifts right, higher [H+] = acidosis hyperventilate: *reaction shifts left, lower [H+] = alkalosis

Answer 344

2 general mechanisms: 1) excreting (vs. reabsorbing) H+ 2) reabsorbing (vs. excerting) HCO3- -excreted H+is buffered by NH3 and HPO42-in urine -reabsorbed HCO3- helps buffer H+ in ECF

Answer 345

*huge amounts of bicarbonate are filtered at the glomerulus, that must be reabsorbed to maintain buffering capacity -occurs in proximal tubule *no transporters for HCO3-on apical membrane, so indirect method used: HCO3- converted to CO2 to cross membrane then back to HCO3- before leaving the cell *fine-tuning of acid-base balance carried out in distal nephron -in intercalated cells(I cells), interspersed among principal cells (P cells) *type A intercalated cells secrete H+and reabsorb bicarb -deal with acidosis *type B do the opposite, compensating for alkalosis

Answer 346

1) NHE secretes H+ 2) H+ in filtrate plus filtered HCO3- forms CO2 3) CO2 diffuse into the cell 4) CO2 plus water forms HCO3- and H+ 5) H+ secreted again 6) HCO3- is reabsorbed with Na+ 7) glutamine metabolized to NH4+ and HCO3- 8) NH4+ secreted and excreted

Answer 347

acidosis: type A cells excrete H+; HCO3- and K+ are reabsorbed alkalosis: type b cells excrete HCO3- and K+; H+ is reabsorbed

Answer 348

not ventilating enough to remove enough CO2 -alveolar hypoventilation -> CO2 retention -> ↑plasma PCO2 -causes respiratory depression (drugs), asthma, fibrosis, severe pneumonia, other diseases affecting breathing

Answer 349

too much CO2 lost = ↓ plasma PCO2 -excessive artificial ventilation .... (solution: turn down ventilator) -anxiety-driven Hyperventilation .... (solution: bag breathing)

Answer 350

increased acidity or loss of HCO3- *H+input (dietary, metabolic) exceeds H+excretion -lactic acidosis -anaerobic metabolism -ketoacidosis -excessive breakdown of fats or certain AAs (type I diabetes, low carb diets) -ingestion of certain toxins (methanol, ethylene glycol) *loss of bicarb-diarrhea

Answer 351

decreased acidity due to loss of H+ *loss of H+ from stomach (excessive vomiting) *ingestion of excessive bicarb-based antacids (TUMS)

Answer 352

*chemical messenger secreted into the blood by specialized cells *regulate long-term and/or on-going functions -growth, development -metabolism -regulation of internal environment (temp, water balance, ions) -reproduction *hormone act on target cells by regulating ... -enzyme activity -ion transport across a membrane -gene expression protein synthesis

Answer 353

Arnold Adolph Berthold *long known that removing testes from farm animals reduced masculine behaviour and phenotype *Berthold wondered whether effects were due to neural connections with testes experimental model: male chickens -first experiment in endocrinology

Answer 354

Charles-ÉdouardBrown-Séquard(1817-1894) *claimed that injecting himself (age 74) with extracts of testes (bull, dog, guinea pig, monkey?) ground up in water caused ... -sexual rejuvenation, extension of life

Answer 355

*ablate(remove suspected gland) *replace(gland or extract of gland) *create situation of excess -isolate active substance characterize chemically -through these classic approaches, 'classic' hormones were identified major tool of endocrinologists, then and now: biological assays (bioassays) -biological systems (intact animals, tissue/cell cultures) -introduce putative hormone -> monitor response

Answer 356

exocrine has an exit point, outside endocrine has no connection with the surface, travels in blood

Answer 357

*secreted by a group of cells derived from epithelial tissue that form discrete glands *secreted into blood *travel to distance targets *act at very low concentrations -nanomolar(10-9), picomolar(10-12)

Answer 358

-not secreted by identifiable glands -secreted by neurons, immune cells, endocrine cells of gut -act locally -diffusion through ECF -clearly identified as hormones in one context but also secreted within CNS, act as neurotransmitters

Answer 359

*by far the largest group *3 amino acids -> larger peptides -> proteins -> glycoproteins *t1/2(half life) in ECF brief (seconds to minutes) -sustained responses require continuous release of hormone *hydrophilic -bind to membrane receptors

Answer 360

chemical messenger secreted into the blood by specialized cells

Answer 361

Generated from within

Answer 362

Generated from outside

Answer 363

long-term and/or on-going functions

Answer 364

Removed testes from farm animals

Answer 365

A system of excess was established in which isolated active substances were generated to characterize each substances chemically.

Answer 366

- ablation - extract - induction of "excess" hormone

Answer 367

Into blood vessels, onto surface

Answer 368

Nanomolar or picomolar

Answer 369

having receptors for said hormone being examined

Answer 370

- secreted by a group of cells derived from epithelial tissue - secrete into blood - travel to distant targets - act at very low concentrations

Answer 371

secreted by Neurons, immune cells and endocrine cells of gut

Answer 372

Implications of hydrophobicity/ philicity

Answer 373

- source - mechanism - chemistry

Answer 374

Membrane surface receptors

Answer 375

via a secretory pathway

Answer 376

Non-specific proteases in ECF

Answer 377

A large precursor to hormones that is a product of the ribosome

Answer 378

Endoplasmic reticulum to the Golgi apparatus

Answer 379

their caches of peptide hormones

Answer 380

Tryptophan and tyrosine

Answer 381

Catecholamines and thyroid hormones

Answer 382

Cholesterol

Answer 383

No, they're made on demand by increasing activity of enzymes.

Answer 384

Circulate in blood while bound to proteins, either specific carriers or albumin

Answer 385

No, there are numerous precursors between a steroid and cholesterol

Answer 386

ligand-activated transcription factors, steroid response elements

Answer 387

hypothalamus

Answer 388

hypthalamus, posterior pituitary gland

Answer 389

trophic hormones

Answer 390

Releasing hormones

Answer 391

tropic hormones

Answer 392

- hypothalamus - anterior pituitary gland - endocrine target of pituitary hormone

Answer 393

hypothalamus and the anterior pituitary

Answer 394

increase, low

Answer 395

Synergistic, Permissive Antagonistic

Answer 396

combined effect is greater than the sum of individual effects of hormones

Answer 397

Hormone is required for a effect to occur but is not enough on its own for the full effect

Answer 398

One substance opposes the action of another

Answer 399

permissive

Answer 400

Synergistic

Answer 401

Antagonism

Answer 402

benign tumors or cancerous tumors of glands

Answer 403

the inability to produce a hormone

Answer 404

Mutations in genes that code for hormones or enzymes that produce said hormones, atrophy of gland due to disease process deficiency in iodine

Answer 405

suppression

Answer 406

vasopressin receptor

Answer 407

Driving transcription of particular genes leading to synthesis of proteins

Answer 408

Thyroxin (aka thyroid hormone, T4) and TRH

Answer 409

decrease, decrease

Answer 410

By the presence of either 2 X chromosomes (female) or 1 X and 1 Y (male)

Answer 411

at fertilization -female can only donate X -male can donate X and Y

Answer 412

"indifferent"

Answer 413

-differentiate gonads down either male or female pathway -build appropriate ductwork for internal transport of gametes -build appropriate external genitalia for receipt/delivery of male gametes

Answer 414

-requires expression of master gene on the Y choromsome --> Sry gene

Answer 415

you default to ovary

Answer 416

germ cell precursors plus two major somatic cell types: Laydig cells, Sertoli cells

Answer 417

Leydig cells, sertoli cells

Answer 418

components of urinary tract (mesonephric duct)

Answer 419

components of paramesonephric duct

Answer 420

Wolffian duct

Answer 421

Mullerian duct

Answer 422

-need testosterone from Leydig cells (to support male tract) -need Anti-mullerian hormone (AMH) from Sertoli cells to regress Mullerian duct

Answer 423

-from Leydig cells -to support male tract

Answer 424

-comes from Sertoli cells -to regress Mullerian duct

Answer 425

-testosterone --> dihydrotestosterone (DHT)

Answer 426

F. Build THREE pairs of kidneys and TWO sets degenerate

Answer 427

Each sex forms paramesonephric ducts --> but they are only retained in females

Answer 428

primitive kidney

Answer 429

paramesonephric duct

Answer 430

-the early version of the kidney is called the pronephros and then stops growing (and later degenerates) -the second set is is called the mesonephros and contains mesonephric ducts --> these are lost in females and retained in males -similar idea in females but with para-mesonephric duct -metanephros is the mature kidney that is retained

Answer 431

-Wolffian derivatives: -epididymis -vas (ductus) deferens -accessory sex glands

Answer 432

Mullerian derivatives: -oviducts (Fallopian tubes) -uterus -cervix -upper vagina

Answer 433

-if somatic cells in testes express Sry = testis -if somatic cells do not express Sry = ovary

Answer 434

-testis leads to spermatogonia, Sertoli cells and Leydig cells -Sertoli cells produce AMH = Mullerian duct regresses -Leydig cells secrete testosterone = Wolffian duct retained + DHT = male genitalia

Answer 435

ovary leads to oogonia, granulosa cells, theca cells -ovary --> oocytes -granulosa cells = no AMH = mullerian duct retained + no androgen = female external genitalia -theca cells = no T = Wolffian duct regresses

Answer 436

-5-alpha-reductase in XY individuals -21-hydroxylase in XX individual -androgen receptor in XY individual

Answer 437

converts progesterone to corticosterone and involved in the production of cortisol

Answer 438

converts testosterone to DHT

Answer 439

-don't have conversion of testosterone to DHT which means we don't see male genitalia develop

Answer 440

-won't be able to produce cortisol = enlargement of adrenal -leads to higher production of androgens (male hormones) which leads to masculinizing effects in women

Answer 441

- androgen insensitivity syndrome which leads to intra-abdominal testes

Answer 442

-stem cells = oogonia -starts and ends in fetal life

Answer 443

females are born with all the oocytes they will ever have

Answer 444

arrest in meiosis 1

Answer 445

1: when follicle/egg is selected for ovulation. Then meiotic arrest (again) 2: Meiosis II completed only if/when that oocyte is fertilized

Answer 446

at puberty

Answer 447

-complete meiosis and differentiation into functional sperm without arrests

Answer 448

male germ cells undergo mitosis/meiosis throughout life

Answer 449

-Germ cell = oogonium --> proliferates by mitosis (have 46 diploid chromosomes per cell) and differentiates to produce oogonia -DNA replicates but no cell division --> meiosis 1 arrest until selected for ovulation = primary oocyte -meiosis 1 occurs and we have formation of a polar body and a secondary oocyte (again arrested development, 23 chromosomes, duplicated) -egg is released from ovary at ovulation -if fertilized, undergoes meiosis 2, forms another polar body and a zygote

Answer 450

-At puberty, spermatogonium begin proliferating by mitosis (46 chromosomes per cell) to produce spermatogonia -some spermatogonia differentiate to yield primary spermatocytes -undergoes meisosis 1 to produce secondary spermatocytes -undergo meiosis 2 to yield spermatids which develop into sperm and can fertilize an egg

Answer 451

2. They degenerate

Answer 452

Females: from the beginning, but primary oocyte is arrested until ovulation males: start mitosing at puberty

Answer 453

The interaction between the CNS, hypothalamus and the anterior pituitary in regulating gamete production in the gonads

Answer 454

-Internal and environmental stimuli are detected by the CNS -stimulate hypothalamus to release gonadotropin-releasing hormone -acts on anterior pituitary to release luteinizing hormone and follicle stimulating hormone -LH acts on endocrine cells to produce steroids for gamete production -FSH acts in gamete production

Answer 455

hormones in anterior pituitary feed back to regulate release -steroids produced in the HPG axix feed back to GnRH in hypothalamus and to the anterior pituitary

Answer 456

-main hormones of testes: testosterone (androgen) -main hormone of ovaries: estradiol (estrogen), progesterone (progestin)

Answer 457

-testosterone (androgen) -estradiol (estrogen) -progesterone (progestin)

Answer 458

T (kind of). With exception of estradiol under certain conditions

Answer 459

-sustained high levels of estradiol will cause massive "surge" release of LH/FSH = positive feedback

Answer 460

testicular migration into scrotal sac

Answer 461

androgen dependent

Answer 462

temperature 2-3 degrees celsius less than body temperature

Answer 463

cryptorchidism

Answer 464

In the testes, have highly coiled seminiferous tubules --> progresses into epididymis and then the vas deferns

Answer 465

-has entered meiosis 1

Answer 466

-has entered meiosis 2

Answer 467

-haploid sperm that have completed meiosis but have not yet undergone cell remodelling

Answer 468

-cells associated with the basal lamina and tight junctions between Sertoli cells

Answer 469

-near the basal lamina, have the spermatogonia -going out from the basal lamina, have primary spermatocytes, secondary spermatocytes, then spermatids and spermatozoa

Answer 470

-Have the head, midpiece and tail -Head: contains nucleus, acrosome contains enzymes to aid fertilization -Midpiece: contains mitochondrial spiral -tail: made of microtubules

Answer 471

The portion of the head that contains enzymes to aid fertilization

Answer 472

64 days (in humans)

Answer 473

Sertoli cells

Answer 474

Leydig cells

Answer 475

LH/FSH and GnRH

Answer 476

-development and maintenance of internal and external genitalia -support of spermatogenesis

Answer 477

-protein synthesis --> muscle growth

Answer 478

-negative feedback control of LH/FSH and GnRH -primary sex characteristics -secondary sex characteristics -behaviour

Answer 479

testosterone --> but often converted in target tissue to DHT

Answer 480

2-3x higher affinity for androgen receptor

Answer 481

-differentiation of external genitalia during development -development and support of accessory sex glands -male pattern baldness, acne, facial hair

Answer 482

-have ovarian tubes ending in fimbriae that hover near the ovary -ovarian tubes go to the uterus, lined by the endometrium -cervix opens up into the vagina

Answer 483

inner lining of uterus

Answer 484

glandular epithelium and lamina propria

Answer 485

smooth muscle of uterus

Answer 486

On top of the myometrium

Answer 487

-start out with primary follicles -they progress into secondary follicles -gets bigger and bigger until it ruptures and you have ovulated oocyte -leftover somatic cells of the follicle will form into the corpus luteum which make progesterone --> process called luteinization -in a non-preganant cycle, the corpus luteum will regress

Answer 488

luteinization

Answer 489

luteolysis

Answer 490

progesterone

Answer 491

-antrum is the inner chamber -then layer of granulosa cells, the basal lamina and then the theca

Answer 492

-LH remains steady until ovulation where you see a big peak

Answer 493

-decreases slightly during the follicular phase and then small peak during ovulation

Answer 494

-follicular phase -ovulation -luteal phase

Answer 495

follicle grows during follicular phase up until ovulation when the oocyte is released -corpus luteum forms during luteal phase and (in a non-pregnant cycle) regresses

Answer 496

-estrogen increases up to a peak at ovulation (because follicle gives off estrogen) -when corpus luteum forms, have surge in progesterone don't have to look at inhibin

Answer 497

During menses, endometrium sheds off and becomes thinnest. Then during proliferative phase it grows again -Then enters secretory phase where it is secreting compounds that make it a good place for a baby to grow

Answer 498

When corpus luteum regresses, you have a steroid withdrawal that causes shedding of the endometrium

Answer 499

luteal regression that leads to low ovarian steroid = menses

Answer 500

-selected follicle begins to grow and secrete estrogen -sustained exposure to high estrogen (low progesterone) causes massive release of gonadotropins

Answer 501

LH surge = ovulation

Answer 502

-part of endometrial lining shed due to steroid withdrawal = menses -rising estrogen (from maturing follicle) stimulate regrowth of lining

Answer 503

proliferative phase

Answer 504

begins with LH surge, which triggers ovulation

Answer 505

-oocyte escapes ovary, completes meiosis 1 in response to LH surge, then arrests again in meiosis 2 -somatic cells of ovulatory follicle transform into luteal cells =luteinization -high ovarian steroids suppress gonadotropins, preventing growth of large follicles -in the absence of pregnancy, luteal regression occurs after 12 days

Answer 506

-surge in LH

Answer 507

luteinization

Answer 508

-solid, progesterone secreting structure

Answer 509

-high ovarian steroids suppress gonadotropins

Answer 510

-absence of pregnancy

Answer 511

-under influence of progesterone and estrogen, uterus continues to prepare for pregnancy -luteal regression leads to steroid withdrawal and menses

Answer 512

secretory phase

Answer 513

1. ovulation 2. day 1: fertilization 3. Days 2-4: early cleavage stages 4. Day 4-5: Blastocyte reaches uterus 5. Days 5-9: Blastocyte implants

Answer 514

inner cell mass and trophectoderm

Answer 515

inner cell mass

Answer 516

trophectoderm (such as placenta)

Answer 517

-undergoes changes as it moves through vagina--> cervix --> uterus --> oviduct

Answer 518

-must penetrate layer of granulosa cells and glycoprotein layer (zona pellucida)

Answer 519

assisted by enzymes released from acrosomal cap

Answer 520

-it has completed meiosis I (extruded polar body) and arrested part way through meiosis II

Answer 521

fusion of membrane activates oocyte, triggering completion of meiosis II, closely followed by syngamy with sperm and preparation for the first mitotic division

Answer 522

-floating in amniotic fluid which is held by the amnion and placenta

Answer 523

The act of giving birth

Answer 524

cervical softening

Answer 525

-cervical softening -initiation of rhythmic uterine contractions -delivery of the baby -expulsion of the placenta

Answer 526

sequential cascade of hormones

Answer 527

consistent finding is positive feedback/neuroendocrine reflex involving oxytocin

Answer 528

-cervical stretch occurs -baby drops lower in uterus to initiate labor -stimulates oxytocin release from the posterioir pituitary which causes uterine contractions -pushes baby against the cervix causing cervical stretch