Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
9 Muscles Physiology: Where hath all my skin gone? MUSCLE STRUCTURE SLIDING FILAMENT THEORY (or, 6[ish] easy steps to contraction) 3 TESTS OF THE SLIDING FILAMENT MODEL 1 CONTRACTION ENERGETICS Three metabolic pathways supply ATP for muscle contraction Slow oxidative (SO), fast glycolytic (FG), and fast oxidative glycolytic (FOG) fibers have distinctive traits visible even in histologic section Q: How might dominant fiber type differ among athletes with different specialties? ? ? MUSCLE CELL TRADE-OFFS Fiber types in the running muscles of the cheetah (Williams et al. 1997) Proportion SO vs FG up to 83% of vastus lateralis fibers are FOG and FG Glycolytic enzymes Oxidative enzymes Mitochondria Myoglobin concentration (PK = pyruvate kinase / LDH = lactate dehydrogenase) PK and LDH levels are elevated CS = citrate synthase / HOAD = 3-hydroxyactyl-CoA dehydrogenase CS and HOAD levels are depressed 2-4% of volume of muscle fiber within range of other sprinters and endurance runners Q: Is there a downside to being the fastest mammal? http://www.youtube.com/watch?v=jMwefq1ZtNI Muscle cell volume as a zero-sum system Q: Predict the effects of maximizing: muscle protein mitochondria sarcoplasmic reticulum From: Rome and Lindstedt. 1998. News Physiol. Sci 13:261-268. If cell volume is constant, tradeoffs exist. Mitochondria (“fuel tank”) Myofibrillar (“horse power”) Sarcoplasmic reticulum (“accelerator”) 6 Q. How does Ca2+ get back within SR? sarco/endoplasmic reticulum calcium-ATPase (SERCA) actively pumps calcium back into the SR 7 Calcium transients for three different fibers taken from the oyster toadfish. SO fibers FG fibers Superfast twitch swimbladder fibers Q: which is which? Q: what can you predict about cell composition? http:// www.dosits.org/ audio/fishes/ oystertoadfish/ seconds Q: Which of the muscle profiles belongs to each of the muscles pictured? toadfish swim bladder typical skeletal muscle rattlesnake rattle myofibrils SR mitochondria (force) (Ca++ uptake) (ATP supply) 1 ≈ 90 ≈5 ≈5 50 30 4 31 26 26 2 3 9.5 - Food and Fuel Hydrolysis vs. cellular respiration Digestive tract anatomy and function DIGESTIVE TRACT ANATOMY AND FUNCTION Feeding Mechanical breakdown Storage Chemical breakdown = hydrolysis Absorption of monomers (elimination) Sequential processing of food HEADGUT - food capture, reception, mechanical breakdown, some storage (usually mouth, teeth, lips, tongue, salivary glands) FOREGUT - food conduction, storage, chemical digestion, limited maceration (usually esophagus and stomach) MIDGUT - chemical digestion and absorption (usually small intestine) HINDGUT - water and mineral absorption, waste storage and elimination (usually large intestine / rectum) Transported and assembled into more complex molecules after absorption Examples of EXOCRINE processes in digestion (monomers of macromolecules) salivary amylase, a carbohydrase pepsin, a protease bile is an emulsifier (not an enzyme) bicarbonate adjusts pH (not an enzyme) lipases, carbohydrases, and proteases make up “pancreatic juice” Examples of ENDOCRINE processes in digestion. gastrin stimulates pepsinogen and acid release secretin stimulates pancreatic release of bicarbonate cholecystokinin simulates release of pancreatic enzymes (and bile) Review: glucose homeostasis is regulated (in part) by pancreatic hormones β-cells are blue If blood glucose is high….. α-cells are red If blood glucose is low … Q: How can external conditions affect glucose levels? The HPA axis CRH = corticotropin releasing hormone ACTH = adrenocorticotropic hormone Glucocorticoids (e.g. cortisol, corticosterone) CARNIVORY vs HERBIVORY Q: Which diet is “higher quality” – carnivorous or herbivorous ? Hume, 1989 Carnivores Slicing dentition Small stomach Short midgut Large liver (bile production) Little storage space Short transit time Q: What makes meat so easy to digest? Q: How is diet reflected in digestive tract anatomy? Q: What is so problematic about a plant diet? Q: What digestive strategies are available to overcome these difficulties? 1. 2. 3. Mean retention time Fermentation of ingested plant material by symbiotic microbes Q: What anatomical innovations are required by the vertebrate host? Q: What constraints might the process of fermentation of low quality food exert on the process of host feeding / digestion? Q: What are the advantages / disadvantages of using different portions of the gut as the fermentation chamber? foregut - BEFORE the small intestine hindgut - AFTER the small intestine Fermentation chambers of foregut fermenters are usually enlarged regions of the esophagus and/or stomach. Rumination = rechewing Large hindgut fermenters usually use a tubular colon for fermentation. Small hindgut fermenters are usually cecum fermenters. Coprophagy is associated with small body size, nesting and cecum fermentation FASTING Pythons as models of extreme physiological regulation of digestion Q: Why do pythons down-regulate their guts between their rare feedings? At what cost? Q: How does fasting affect emperor penguin physiology and behavior? Groscolas and Robin 2001. Comparative Biochemistry and Physiology A 128:645. VITAMIN REQUIREMENTS Q: what does the term “essential” mean? enhances osteoclast activity Fat soluble vitamins are stored; both deficiency and toxicity are dangers. collagen synthesis Water soluble vitamins are not stored; only deficiency is a danger. Roald Amundsen Robert Scott Polar trip diets of both Amundsen (Norway) and Scott (England) in the austral summer of 1911-1912 Amundsen Dogs (carnivores) Scott Ponies (herbivores) and motorized sledges versus Collagen synthesis requires Vitamin C Vertebrates for which vitamin C is essential: bats, anthropoid hominids, some rodents some birds some fish Vitamin C is a water soluble vitamin that is not stored, so only deficiency is a danger. Scurvy, the “curse of the Arctic” is associated with decreased wound healing, osteoporosis, hemorrhaging, bleeding into the skin, joint pain, anemia, and friable bleeding gums with loosened teeth. The Australasian Expedition to Antarctica 1912-1913 Mawson Ninnis Mertz Vitamin A is a lipid soluble vitamin. It is stored, so both deficiency and toxicity are dangers. toxicity hemorrhage alopecia normal deficiency death erythema fractures bone exostoses eczema night blindness ↑cerebrospinal fluid pressure xerophthalmia inanition death 10 100 1,000 10,000 Vitamin A intake, µg/kg/day 100,000