Download 9 Muscles Physiology:

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