BISC 305 Final EXAM Notes PDF

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High yield summary notes for the final exam. Includes all the important information that you need to know including professor remarks not included in lecture slides....

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BISC 305: FINAL EXAM NOTES NOTE: ALL CREDIT FOR IMAGES GO TO “PRINCIPLES OF ANIMAL PHYSIOLOGY” 3RD EDITION BY CHRISTOPHER D. MOYES AND PATRICIA M.SCHULTE.

Lecture 22: The Kidney Kidney Structure + Function ●

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6 roles in homeostasis ○ Ion, osmotic, blood, pH balance ○ Excretion of metabolic waste + toxin ○ Hormone production Kidney has 2 layers ○ Outer cortex ○ Inner medulla Urine leaves kidney via ureter  , which empties into urinary  bladder

Nephron ● ●

Functional unit of kidney Composed of ○ Renal tubule ■ Lined with transport epithelium ■ Different segments with specific transport functions ○ Vasculature ■ Glomerulus: ball of capillaries surrounded by Bowman’s  capsule ■ Capillary beds surrounding renal tubule

Urine Production ●

4 processes: ○ Filtration: filtering blood at glomerulus into filtrate ○ Reabsorption: removing specific molecules from filtrate ○ Secretion: adding specific molecules to filtrate ○ Excretion: excreting urine from body

Filtration ●

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Liquid part of blood filtered into Bowman’s capsule ○ Water and small solutes can cross while blood cells and large macromolecules can’t Glomerular capillaries are very leaky ○ Podocytes with foot processes form filtration structure (contribute to leakiness)

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Mesangial cells control blood pressure and filtration within glomerulus

Reabsorption ● ● ●

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Initial filtrate is isosmotic to blood (same osmolarity) Most water/salt reabsorbed via transport proteins + energy Renal threshold: the limit of reabsorbing, ability of kidney to absorb certain molecule ○ Rate of reabsorption limited by # of transporters H2O + glucose primary molecules to reabsorb Glucose reabsorbed by secondary active transport

Secretion ● ● ● ●

Molecules removed from blood into filtrate Includes K+, NH4+, H+, drugs and water-soluble vitamins Requires transport proteins + energy K+ highly regulated ○ If too much K+ outside of cells ○ Irregular depolarization ○ Irregular muscle contraction

Tubule Regions ● ●

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Different regions have different transport functions + permeabilities (differences in epithelium) Proximal tubule: most of the solute and water reabsorption occurs here (other areas for “fine-tuning”) ○ Many solutes reabsorbed by N  a+ cotransport WATER FOLLOWS SALTS Proximal tubule also carries out secretion

Loop of Henle ●

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THIN Descending limb is PERMEABLE to water ○ Water reabsorbed via aquaporins (can remove/add them) ○ Volume of urine decreases and becomes more concentrated THICK Ascending limb i s IMPERMEABLE to water ○ Ions reabsorbed ○ Urine becomes dilute Reabsorbed ions help to create osmotic gradient

Distal Tubule ● ●

Can reabsorb salts/water and secrete potassium Transport function affected by hormones ○ PTH: increase Ca2+ reabsorption ○ Aldosterone: increase K+ secretion

 Countercurrent Multiplier ●

Loop of henle acts as countercurrent multiplier due to osmotic gradient facilitating reabsorption of water ○ Low osmolarity near cortex ○ High o  smolarity deep in m  edulla ■ RE: thin descending loop of henle is permeable to water, causing increased osmolarity going down, can reabsorb water

Glomerular FIltration Rate (GFR) ● ● ●

Capillaries are fragile so have to ensure pressure is well controlled GFR determined by pressure across glomerular wall 3 main forces: glomerular capillary and Bowman’s capsule hydrostatic pressure and oncotic pressure

3 Intrinsic Regulators for GFR ● ●

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Regulating blood flow into nephron, ball of capillaries is fragile so don’t want too much pressure, but want enough to get enough GFR (good filtration) Myogenic regulation [ arteriole stretch] ○ Constriction and dilation of afferent arteriole ○ Muscle cells can detect stretch and the higher blood pressure in afferent arteriole, cells contract to constrict the blood vessel, resulting in less pressure Tubuloglomerular feedback [ tubular stretch] ○ Juxtaglomerular apparatus: Juxtaglomerular  cells in afferent arteriole ○ Macula densa cells detect stretch in distal tubule and can control diameter of afferent arteriole by sending signal to juxtaglomerular cells (via RAA pathway) Mesangial control ○ Mesangial cells can contract to alter the permeability of glomerulus (control how much filters through)

Vasopressin [ADH] ● ● ● ● ●

Extrinsic regulator of GFR, peptide hormone produced in hypothalamus and released by posterior pituitary gland Increases water reabsorption from collecting duct by INCREASING number of aquaporins Stimulated by increased plasma osmolarity Inhibited by increasing blood pressure Molecular mechanism: ○ GPCR pathway leading to phosphorylation, resulting in insertion of aquaporins in membrane

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Alcohol inhibits release of ADH, resulting in LESS aquaporins, thus dilute urine (don’t reabsorb as much water, that’s why danger of dehydration) Vasopressin regulates permeability of aquaporins in collecting duct, which determines f inal osmotic concentration of final urine

Aldosterone ●

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Mineralocorticoid hormone (steroid) that controls ion excretion, produced by adrenal cortex ○ Can diffuse to nucleus to activate transcription factor, different mechanism than ADH (slower) Targets distal tubule and collecting duct cells Stimulates Na+ r eabsorption and K+ excretion Aldosterone controls K+ levels in blood (stimulated by increases in circulating K+)

Renin-Angiotensin-Aldosterone (RAA) Pathway ● ●

Juxtaglomerular cells secrete renin enzyme when blood pressure or GFR lower than normal Secretion of renin can be controlled by: ○ Juxtaglomerular cells release renin in response to LOW B.P. (Via baroreceptors) ○ Macula densa cells in distal tubule respond to decrease blood flow by sending signal to juxtaglomerular cells to release renin

Atrial Natriuretic Peptide (ANP) ● ● ●

Increases urine output and lowers blood volume + pressure Antagonist to RAA pathway, increases excretion of Na+ Increases GFR

Thirst ● ●

Detected and controlled by hypothalamus Osmoreceptors monitor body fluid concentrations

Lecture 23: Digestion 1 ● ●

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Assimilation: p  rocesses of nutrient uptake, digestion and absorption taking place in G  I (gastrointestinal) tract Diets provide energy ○ Caloric equivalent: energy content of gram of specific molecule (e.g. protein/carb = 4 kcal/gram) Some energy spent digesting food (have to expend energy to break down food): ○ Specific dynamic action (SDA): increased metabolic rate during digestion ○ Heat increment (energy released as heat): importance source of thermal energy

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Vitamins: group of unrelated molecules with diverse functions, many participate as cofactors for enzymes, obtained in diet or from GI tract bacteria ○ Fat soluble: vitamins D, E, A, K ○ Water soluble: vitamins B, C Minerals: metallic elements participating in protein structure (e.g. calcium), most absorbed by specific transporters along GI tract Amino acids: used to build proteins, 8 essential (obtained from diet), deficiency can lead to development defects ○ Protein quality: amino acid profile of dietary protein ■ Animal tissue provides HIGHER protein quality than plant  tissue (animal has similar amino acid profile to you when eaten, some plants lack specific amino acids) Digestive enzymes: enzymes that convert macromolecules into forms that can be absorbed and processed ○ Lipases: break down triglycerides/phospholipids into fatty acids ○ Proteases: break down proteins into shorter polypeptides ○ Amylase: break down polysaccharides into oligosaccharides ○ Nucleases: break down DNA into nucleotides Most digestion occurs extracellularly (GI tract lumen) Symbiotic organisms aid digestion in many animals (e.g. bacteria and fungi) ○ Enterosymbionts: in gut, live within lumen of GI tract ○ Exosymbionts: actively cultivated outside body ○ Endosymbionts: g  row in interstitial spaces or within host cells Nutrient transport (across plasma membranes) ○ Some polar molecules require protein carriers ■ Facilitated diffusion: d  own concentration gradient ■ Active transport: against concentration gradient (via N  a+ dependent cotransporters) ○ Some nutrients transported via v esicles: ■ Uptake ● Pinocytosis: nutrients in solution ● Phagocytosis: particulate nutrients ■ Expulsion ● Exocytosis Carbohydrate breakdown and absorption ○ Maintenance of glucose levels is crucial ○ Polysaccharides (e.g. glycogen, starch) and disaccharides (e.g. sucrose, lactose) are broken down into monosaccharides (e.g. glucose) ○ Mouth: ■ Salivary amylase can digest glycogen/starch into oligosaccharides ○ Small intestine: ■ Pancreatic amylase can digest glycogen/oligosaccharides/starch into disaccharides (which then digested into monosaccharides such as glucose, which can be used as fuel) Carbohydrate Transport (absorbing glucose) ○ LOW glucose levels in gut lumen

Not many glucose transporters to absorb glucose, physically removed to ensure glucose is “trapped” within enterocyte (otherwise glucose would leave, going down its concentration gradient) ○ HIGH glucose levels in gut lumen ■ Transporters move to apical surface to absorb extra glucose Proteins are broken down into dipeptides and amino acids, which can then be absorbed by epithelial cells ○ Slide 20 Lipids are more difficult to digest/import because of their h  ydrophobicity ○ GI tract secretes bile, which emulsifies large lipids into smaller droplets, which can then diffuse across cell membrane into epithelial cell ○ Lipids go through smooth ER for packaging, since lipophilic, they get a protein coat to ensure that lipid doesn’t diffuse into any cell in body when travelling through bloodstream ○ Lipids carried in blood as lipoprotein complexes ■

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Finding + Consuming Food ● ● ● ● ●

Digestion physiology matches chemical + physical nature of diet Animals detect food via sensory receptors (gustatory + olfactory) Simple animals (e.g. sponges  ) ingest food by phagocytosis ○ Nutrients taken up directly Cnidaria have primitive gut, takes up bigger molecules which can digest via digestive enzymes, then absorb Teeth: many vertebrates have toothlike structures ○ Chewing breaks up food to smaller chunks to i ncrease surface area for digestive enzymes to more efficiently “attack” (digest) ○ Teeth shape reflects diet

Digestive Systems ●

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Surface area: ○ Nutrients hydrolyzed in GI tract lumen and taken up by epithelial cells lining the gut ○ Net uptake of nutrients is based on the surface area (i.e. exposed epithelial cells) ○ Increase surface area via: ■ Increasing gut length ■ Increasing surface “undulations”: circular folds, villi and microvilli Specialized compartments: increases efficiency of digestion ○ Functional specialization (pH, enzymes, types of cells) ○ Sphincters controls passage of food between compartments ○ Ruminants: modification in some mammals allowing to digest plant material (i.e. cellulose) Salivary glands: exocrine gland that secretes saliva, which contains enzymes to initiate digestion

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Stomach: c ontains columnar  epithelial cells on surface ○ Tight junctions: prevent leakage across epithelium ○ Mucous neck cells: secrete mucous ○ Parietal cells: secrete HCl ○ Chief cells: secrete pepsin (protease) ○ Enteroendocrine cells: detect if food is in gut and secrete hormones into blood Intestines: most nutrients absorbed here Exocrine secretion into intestines ○ Bile: solution of digestive chemicals + liver waste products ■ Produced in liver ■ Stored in gallbladder ■ Contains: ● Phospholipids: aids in uptake of lipids ● Bile salts: emulsify  salts ○ Pancreas s ecretes enzymes (e.g. proteases, amylase etc.) Activation of proenzymes ○ Pancreas secretes proenzymes into small intestine via pancreatic duct ○ Membrane-bound enterokinase i n small intestine activates trypsinogen to trypsin, which activates other proenzymes into the active enzymes (small intestine mucous walls ensure body doesn’t get digested) ○ Procarboxypeptidase -> carboxypeptidase ○ Trypsinogen -> trypsin ○ Chymotrypsinogen -> chymotrypsin 

Lecture 24: Digestion 2 Regulation of Feeding + Digestion ● ●

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Nerve signals (e.g. CNS) and hormones control digestive functions Control of appetite ○ 3 gut hormones control appetite by binding hypothalamus receptors: ■ Leptin: secreted by white adipose tissue when lipid content is high ● suppresses a  ppetite ■ Peptide YY (PYY): secreted by colon when full, ● suppresses a  ppetite ■ Ghrelin: secreted by stomach when empty, ● stimulates appetite   ○ Hypothalamic neurons release neurotransmitters in response to gut hormones ■ NPY STIMULATES appetite ■ POMC INHIBITS appetite Control of Secretions ○ Gastric: i ngestion + sight/taste/smell of food leads to secretion of enzymes for digestion (e.g. gastric acid + pepsinogen)

Intestinal: acidic gastric secretions produce VIP/secretin/CCK into bloodstream, which act on target organs (e.g. pancreas, liver, gallbladder), which secrete things that aid in digestion (e.g. HCO3-, bile and digestive enzymes) Control of gut motility ○ Smooth muscle contractions move food along GI tract (control via nerves + hormones) ○ Optimal speed: want to minimize amount of indigestible material in GI tract but also want to maximize time for digestion and assimilation (if too slow, wasting energy) ○ Myenteric plexus: nerve network between smooth muscle layers that controls gut motility (receives CNS signals) ■ Motor neurons and interneurons within nerve network are part of enteric system ○ Peristalsis: contractile waves that move food down GI tract, controlled by intrinsic myogenic activity (pacemaker cells) Control of smooth muscle motility ○ acetylcholine activates GPCR transduction pathway, leading to activation of calcium channels (in membrane AND in sarcoplasmic  reticulum), resulting in increased intracellular calcium concentration ○ Increased calcium in muscle cell results in more activated cross bridges and more forceful contraction ○

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Metabolic Transitions Between Meals ● ●

Postprandial period: immediately after meal, nutrients  absorbed into blood Hormones control postprandial levels of nutrients: ○ Pancreatic beta-cells secrete insulin to stimulate glucose uptake ○ Pancreatic alpha-cells secrete glucagon  to stimulate glucose release by liver

Starvation Response ●

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Metabolism reorganization to ensure long-term survival: ○ Conserve glucose to protect glucose-dependent tissue ○ Muscle shifting to lipid metabolism ○ After lipid + glucose stores depleted, PROTEIN BREAKDOWN ACCELERATED ■ Amino acids converted to fatty acids + carbohydrates ○ Structural degradation occurs because no protein stores in body (have to degrade skeletal muscle, B  AD) Early starvation: use glycogen stores early Late starvation: protein breakdown starts (once lipid + glucose stores depleted) ○ Muscle tissue breaks down, skeletal musculature degrades

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Digestive system degradation + rebuilding

Can reduce energetic costs in between meals E.g. pythons eat infrequently, digestive organ mass increases right after eating big meal, then gradually degrades, smooth muscle + nerves retained Dormancy: ○ Hypometabolism: metabolic rate decreased allowing animal to survive adverse conditions ■ Torpor: short sleeps ■ Hibernation: longer sleeps (e.g. bears) ■ Estivation: avoiding dry/hot climate to avoid dehydration (e.g. desert animals) ○ ○

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Lecture 25: Locomotion 1 ● ●

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Locomotion is the act of moving, integrates anatomy with physiological system (mode of locomotion is constrained by e nvironment) Invertebrates: move by crawling except arthropods ○ Simple muscles work with a fluid-filled internal chamber (hydrostatic skeleton, pressure on fluid provides structure) ○ Nematodes: muscle layers alternate contractions to produce undulations ○ Earthworm: peristaltic waves of contraction (muscle contractions alternate) Fish: muscles composed of homogenous fibre  types (either red [slow] or white [fast]) Central pattern generator: area of CNS that controls timing of muscle contraction ○ Alternating sequence of motor neuron activation Tetrapods (and humans) have heterogenous fibre types within muscle fibres due to many complex movements (transition to land) Muscle activity requires lots of ATP energy, metabolic efficiency: ○ Glycolysis: 2 ATP per glucose ○ Aerobic metabolism: 36 ATP per glucose Oxidative phosphorylation: allows for steady-state activity ○ HIGH mitochondrial content in oxidative muscles Glycolysis: high-intensity activity ○ Uses large quantities of glucose and produces lactic acid, which results in muscle exhaustion (ion disturbances + pH imbalances) ○ Exhaustion recovery: must replenish energy  stores (e.g. glycogen, ATP) AND reestablish ion  gradients (Ca2+ distribution + pH) ○ Lactate produced by glycolysis is removed during recovery, converted back into glucose by liver (gluconeogenesis) Postexercise oxygen recovery: rates of oxygen consumption remain elevated even after exercise is done Metabolic Transitions During Exercise ○ Respiratory Quotient (RQ): the ratio of CO2 production to O2 consumption

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■ This can determine type of fuel being used for activity Metabolic Transitions During Migration ○ Initially S  almon are FAT, energy expenditure is mostly from fat  (conserve glycogen stores) ○ During migration, less fat is used, more p  rotein is utilized as fuel (digest muscle) ○ Near end of migration, Salmon are SKINNY, glycogen  is now used for spawning Metabolic transitions controlled by hormones   Glucose main fuel for low-moderate activity (insulin/cortisol) During sustained activity, glycogen stores become depleted, triglycerides are mobilized and utilized Both glucose  and fatty acids can be used as metabolic fuel sources Oxygen delivery to muscles important ○ Small animals can use diffusion  (low metabolic rates) ○ Large animals use cardiovascular  system (use blood to carry oxygen) Rate of oxygen delivery depends on ○ Capillary density ○ Blood flow (vascular tone) ○ Hemoglobin oxygen affinity Rate of O2 diffusion out of RBC depends on ○ Partial pressure gradient for Oxygen ○ Diffusion distance August Krogh Model of Capillary Geometry: capillaries flow straight ○ Problem: hypoxic  regions (deprived of oxygen supply) Actual c apillary geometry ○ Capillary tortuousity: Capillaries are NOT straight tubes, actually weave back and forth in muscle to ensure no hypoxic regions Angiogenesis: synthesis of additional blood vessels ○ Triggered by persistent regional hypoxia ○ More capillaries increase perfusion (blood flow) Myoglobin: oxygen-binding heme protein in aerobic muscle, functions as oxygen storage and for oxyg...