Describe the 6 functions of the skeletal system.
A. Support for body frame, soft tissues, and point of attachment for muscles
B. Protection of vital internal organs
C. Movement in conjunction with skeletal muscles
D. Mineral Storage
-especially of calcium and phosphorus, which can be released to the bloodstream as the body requires. (99% of body's Calcium stored here.)
E. Hematopoiesis Blood cell formation
-Occurs in RED bone marrow. Has Stem Cells, adipose cells, and macrophages.
F. Storage of Energy
-Lipids stored in Yellow Marrow.
Describe the basic structure of cartilage tissue and distinguish the three types of cartilage, including fiber types, matrix composition, and locations of each type.
-Contains lots of WATER which accounts for it's springiness.
-Cells callled chondrocytes are in the lacunae
-Perichondrium (the girdle)
=has blood vessels that will supply nutrients
-Cartilage has no nerves or blood vessels
-Matrix is gel like: Proteoglycans, protein fibers
1.Hyline- Most everywhere
2.Elastic- ear, and epiglottis
(Table 4.10a,b,c and Fig. 6.1).
Describe how cartilage is formed and grows
(appositional vs. interstitial growth, Fig. 6.1)
Appositional Growth- Growth from Outside-Chondroblasts
Interstitial Growth- Growth from within- Chondrocytes
3. Generally stops when the skeleton itself stops growing, usually during adolescence
Define: chondroblasts, chondrocytes, perichondrium, articular cartilage.
- Cartilage forming cells CHONDROBLASTS in the perichondrium secrete new matrix against the external face of the existing cartilage
- CHONDROCYTES within lacunae in cartilage divide and secrete new matrix, expanding cartilage from within
-lacunae- small space containing an osteocyte in bone or chondrocyte in cartilage.
-perichondrium is the membrane surrounding the Cartilage
-articular cartilage-Is on the surface of joints
Describe the 4 types of bone cells, the functions and origin of each, and where you would find them in bone.
1. Osteochondral progenitor cells
- "stem cells"
- found in inner layer of periosteum and perichondrium and in endosteum
undergo mitosis to become osteoblasts or chondroblasts
2.Osteoblasts cells that will PRODUCE bone
- secrete the protein fibers and minerals found in bone matrix
mature bone cells which maintain bone matrix
- Found within tiny spaces called lacunae
- Cell membrane processes contact each other through Canaliculi
cells that BREAK DOWN bone
- originate from same bone marrow cells as monocytes (WBCs)
- several of these marrow cells fuse to form an osteoclast, which is very large with 3-4+ nuclei
Describe the chemical composition and most important functions of the organic (osteiod) and inorganic (hydroxyapatite) components of bone matrix.
-Collagen fibers and Proteoglycans, some glycoproteins
-Important in FLEXIBILITY and tensile strength of bone
-Mineral salts, primarily calcium phosphate and some calcium carbonate
-Gives bones it's HARDNESS and resistance to compression
What %-age of bone matrix is organic vs. inorganic?
Osteoid -organic- = 35% of Matrix
hydroxyapatite -inorganic- = 65% of Matrix
Compare and contrast cancellous (spongy) vs. compact bone vs. cartilage.
A. Cancellous -- "Spongy Bone"
1. Forms the ends of long bones and insides of short, flat, and irregular bones
2. Irregular latticework of thin plates of bone called "trabeculae"
3. Trabeculae resist the STRESS the bone is under
4. Open spaces between trabeculae contain red or yellow marrow.
5. Within trabeculae are lacunae, which contain OSTEOCYTES interconnected by CANALICULI [Fig. 6.4]
6. Nutrients get to the osteocytes by diffusing through canaliculi from blood vessels in marrow spaces between trabeculae
7. Outside surface of trabeculae -- layer of cells -- osteoblasts and a few osteoclasts
B. Compact Bone
1. Forms the external portion of all bones and the bulk of the shaft of long bones
2. Contains concentric ring structures called OSTEONS or Haversian systems
3. Nutrient arteries & veins and nerves from the PERIOSTEUM penetrate through compact bone through perforating (Volkmann's) canals.
- These branch to supply the marrow cavity and the central Haversian canals
4. Around the Haversian canals are CONCENTRIC lamellae, rings of hard, calcified matrix with COLLAGEN fibers
5. Between lamellae are spaces called lacunae, which contain OSTEOCYTES
6. Projecting outward in all directions from the lacunae are tiny canals called canaliculi
* Provides routes for nutrients and oxygen to reach osteocytes and waste removal
Terms: canaliculi; lamellae (all 3 types); Haversian (central) canals; Haversian systems / osteons;
* Provides routes for nutrients and oxygen to reach osteocytes and waste removal
lamellae (all 3 types) rings of hard, calcified matrix with COLLAGEN fibers (3 types: Concentric lamella, interstitial lamella, and circumferential lamella)
Haversian (central) canals-contains the bone's nerve and blood supplies.
Haversian systems / osteons; different names for same thing. fundamental functional unit of much compact bone.
Terms: trabeculae; chondrocytes; osteocytes; lacunae, Sharpey's fibers, Volkmann's / perforating canals.
trabeculae- Trabeculae resist the STRESS the bone is under. Spongy bone
chondrocytes- secrete new cartilage matrix interstitially.
osteocytes-secrete new bone matrix interstitially.
lacunae- contain OSTEOCYTES
Sharpey's fibers-a matrix of connective tissue connecting periosteum to bone.
Volkmann's / perforating canals.- Nutrient arteries & veins and nerves from the PERIOSTEUM penetrate through compact bone through perforating (Volkmann's) canals.
Describe the general structure of flat, short, and irregular bones
A. Flat; [Fig. 6.9] Short; Irregular - [Fig. 6.7]
2. Spongy inside, with marrow in open spaces
3. Flat -- good for protection and muscle attachment
(Fig. 6.9: compact outside; spongy inside; marrow.)
Know the different functions and locations of yellow vs. red marrow in a developing fetus vs. in an adult. Know the term hematopoiesis.
Fetus- all marrow is red marrow. After birth some marrow becomes yellow as it's overcome with fat cells.
At time of adulthood-red marrow in flatbones, epiphisies of long bones, (closer to trunk of body. Like humerus)
The rest is yellow marrow.
Hematoposiesis- hema- blood formation, posiesis- formation
Red bone marrow FUNCTION
Describe the parts of a long bone, including diaphysis, epiphyses, articular cartilage, medullary (marrow) cavity, epiphyseal plate/line.
diaphysis -SHAFT- :central medullary (marrow) cavity contains yellow bone marrow in adults
epiphyses -ENDS THE BONE- :
* often wider than diaphysis
* joint surface covered with articular cartilage
* separated from diaphysis by epiphyseal line
articular cartilage-line the joints
medullary (marrow) cavity-Very center. Filled with marrow.
epiphyseal plate/line-in epiphsis
Where is spongy bone found vs. compact in a long bone? Where is marrow (red or yellow) found?
Compact bone lines the outside where as the spongy bone is in the center. Marrow is found in the Trabeculae of spongy bone.
Compare the structure, location, and functions of endosteum and periosteum (fibrous and osteogenic layers.)
Periosteum membrane is around outer surface of bone
1. Outer "fibrous" layer
* dense, irregular connective tissue
* contains blood vessels that pass into the bone
2. Inner "cellular" (osteogenic) layer contains:
* elastic fibers
* blood vessels
* various types of bone cells (osteoblasts, osteoclasts, osteochondral progenitor cells)
3. Periosteum functions:
* necessary for protection, nutrition, growth, and repair of bones
* site of attachment for ligaments and tendons
Endosteum lining of the medullary cavity
- basically the inner lining of any bone tissue
- also covers spongy bone and lines canals that pass through compact bone
- more delicate connective tissue membrane
- Cells: osteochondral progenitor, osteoblasts, osteoclasts, epithelial
Be able to label Fig. 6.4, 6.6, and 6.8, and Fig. from lab manual, and know the functions of everything labeled in the figures.
Describe when (during development) and how the process of bone formation occur - "Intramembranous Ossification"
(1) Ossification center forms- in connective tissue membrane from mesenchyme
(2) Bone matrix (osteoid) secreted- trabeculae form and osteoblasts become trapped in matrix forming osteocytes.
(3) Blood vessels grow into area- trabeculae meet and fuse around blood vessels.
(4) Periosteum forms- from connective tissue surrounding growing bone mass.
(5) Compact bone forms- from osteoblasts of inner cellular layer of periosteum to form bone collar.
Describe when (during development) and how the process of bone formation occur -
(1) Cartilage model- formed from chondroblasts (cartilage model is lengthed with interstitial growth from Chondrocytes and thickened by Chondroblasts through Appositional growth.)
(2) Bone collar produced at diaphysis-perichondrium becomes periosteum and cartilage calcifies internally.
(3) Primary ossification center forms- blood vessels and osteoblasts invade calcified cartilage to form cancellous bone in diaphysis.
(4) Remodeling of diaphysis- bone collar becomes compact bone and medullary cavity forms.
(5) Secondary ossification centers form- blood vessels and osteoblasts migrate to epiphyses.
(6) Remodeling of epiphyses- articular cartilage forms at ends, spongy bone fills epiphyses and epiphyseal plate separates epiphyses and diaphysis.
Explain how bone growth occurs after bone's initial development.
During infancy and youth:
a. Long bones lengthen entirely by INTERSTITIAL growth of the epiphyseal plates
b. This is controlled by hormones such as human growth hormone and thyroxine, and sex hormones at puberty.
2. Occurs when cartilage cells are produced by mitosis on the epiphyseal side of the plate.
a. Those just a little older enlarge, calcify, and deteriorate.
b. They are invaded by marrow elements, and osteoblasts form spongy bone.
Be sure you understand the process of long bone growth in length as shown in Fig. 6.13 and 6.14, and growth in width as shown in Fig. 6.16.
Be sure to also know which kinds of bones are formed from each process.
[A study activity covering Osteogenesis is posted on Blackboard and may appear on the test in one form or another.]
Use Fig. 6.10 and 6.12 to help you understand these processes, and be able to identify what is occurring in each of the bone formation stages shown in these figures.
Which of these growth processes is called Interstitial? which is Appositional?
appositional growth increases in thickness (building from outside), in width,
interstitial growth increases within to increase in length (growth from within).
Also understand how bone is re-shaped to best meet the stresses it is withstanding as shown in Fig. 6.19.
Entire adult skeleton is renewed about every 10 years.
1. Usually, there is a balance of old bone resorption by osteoCLASTS and new bone formation by osteoBLASTS. They occur at both the periosteal and endosteal bone surfaces.
2. Remodeling bone resorption
a. OSTEOCLASTS secrete chemicals to form tunnels:
* Lysosomal enzymes digest away the ORGANIC matrix of bone
3. Remodeling bone deposit
a. Requires proper amounts of calcium, phosphorous, iron, magnesium, manganese, protein, vitamins C, A, and B12, D, etc.
b. Occurs along the walls of the tunnels produced by osteoclasts after blood vessels have grown into the area; tunnel becomes HAVERSIAN CANAL
c. In spongy bone, osteoCLASTS break down bone matrix along surface of trabeculae, then osteoBLASTS produce new matrix.
d. It's thought that the osteoid is secreted first by the osteoblast, and must mature for about 10-12 days, then it is calcified when the concentrations of Ca and P in the tissue fluids reach a certain level.
- This calcification occurs through the action of an enzyme alkaline phosphatase (produced by osteoblasts.)
terms to know: Osteogenesis; mineralization; calcification; appositional growth; interstitial growth; mesenchyme; periosteal bud; primary & secondary ossification centers.
primary & secondary ossification centers-
How and why does bone remodeling occur?
Describe bone resorption and bone deposit.
Bone is major storage site for body Ca+2
* OsteoBLASTS put Ca+2 into new bone matrix
* OsteoCLASTS take Ca+2 out of bone
What are the two factors that control the frequency and location of bone remodeling?
- Calcium homeostasis
- Mechanical and gravitational forces acting on the skeleton
What are the essential minerals and vitamins needed to maintain healthy bone?
calcium, phosphorous, iron, magnesium, manganese, protein, vitamins C, A, and B12, D,
Be able to relate the maintenance of calcium homeostasis by the body to bone production / resorption;
Hormones PTH and calcitonin help to maintain blood calcium levels. BUT - calcitonin most important in bone deposit in children.]
...know the relevant hormones that control this process, which gland secretes each of them, and how their secretion is controlled.
A.- PTH - Parathyroid hormone (parathyroid gland)
1) Stimulates osteoCLAT number and activity to degrade bone to release Ca+2 into blood
2) Increases absorption of Ca+2 from small intestine and reabsorption in kidneys
3) Very important in adults
B.- Calcitonin (thyroid gland)
1) Decreases osteoCLAST activity
2) Stimulates osteoBLAST activity to deposit Ca+2 from blood into bone in children and adolescents
Be able to explain or label Fig. 6.21 or Calcium homeostasis figure posted from other textbook.
How do mechanical forces / stresses affect the maintenance of calcium homeostasis?
These forces determine which osteoclasts are going to be most sensitive to PTH, so bone in the LEAST stressed areas is degraded when necessary.
- Mechanical stress increases osteoblast activity to strengthen bone where it's most needed
- Lack of stress decreases osteoblast activity so bone is less dense
What is the role of Vitamin D in calcium homeostasis? estrogen? What is osteoporosis?
- Ca+2 is absorbed from foods in the intestines in the presence of Vitamin D.
- Estrogen inhibits PTH
Osteoporosis occurs when the body fails to form enough new bone, when too much old bone is reabsorbed by the body, or both. (p. 194-5)
Describe the 4 basic steps to repairing a bone fracture: hematoma formation; callus formation; callus ossification; remodeling
1) Hematoma formation
- caused by breaking of blood vessels in bone and periosteum, which results in a mass of clotted blood.
-area becomes swollen, inflamed, and hurts!
2) Callus formation
- Capillaries grow into the hematoma, and phagocytes move in and clean up debris.
- Fibroblasts and osteochondral progenitor cells move into fracture area from local periosteum and endosteum
- Fibroblasts produce collagen fibers of internal callus
- Osteochondral progenitor cells become osteoblasts and chondroblasts
- Osteoblasts produce bone and chondroblasts produce cartilage to make external callus
- Osteoblasts farthest from capillaries secrete a bulging cartilaginous matrix that later calcifies.
3) Callus ossification
- The fibrocartilage callus is converted into a woven spongy bone through endochondral ossification
- Starts at 3-4 weeks after injury; continues for 2-3 months.
4) Bone Remodeling
- will continue for several months
- removes external bulge and forms the medullary cavity
- replaces woven spongy with lamellar compact bone.
Know the 6 functions of the muscular system and the 4 characteristics of muscle tissue.
1. Body as a whole
2. Things within body
B. Maintaining body position (posture)
C. Regulating organ volume, entrance/exit
* Food in stomach
* Urine in bladder
D. Stabilizing joints
E. Producing heat
F. Respiration, communication, heartbeat
A. Excitability (Irritability) muscle can receive and respond to STIMULI
B. Contractility muscle can SHORTEN & THICKEN when stimulated
C. Extensibility muscle can STRETCH
D. Elasticity muscle returns to its original shape after contracting or extending
Be able to distinguish between the 3 types of muscle tissue in terms of their appearance, functions, control, and locations in the body.
Skeletal, Cardiac, Smooth
(Tables 4.13 and 9.2 will help with this.]
Be able to describe the detailed structure of skeletal muscles, and label Fig. 9.1, 9.3, 9.4, 9.5(a) and (b), and 9.13.
Make sure that you know the specific functions of ALL cellular components (like SR, T-tubules, sarcolemma, myoglobin, etc.)
- Sarcoplasmic reticulum (smooth ER)
*stores and pumps calcium ions
* carries the electrical stimulus into the myofibril
* brings extracellular fluid into the inner portion of the muscle fiber
*red protein that stores __________________
as well as blood vessels, nerves, and connective tissues.
What is a triad?
terms: muscle fascicle vs. fiber vs. myofibril vs. sarcomere vs. myofilament.
Myofibril- bundles of protein filaments.contains 2 types of protein filaments called MYOFILAMENTS.
Myofilaments: Actin and Myosin
*Actin is smaller than myosin
*Together they form a SACROMERE.
Sacromeres are joined end to end to form myofibrils.
Fiber- A cylindrical, multinucleate cell composed of numerous myofibrils that contracts when stimulated.
In figures showing sarcomeres, you should know the A and I bands, M-line, and Z-disc (line.)
Look at figures and label them
Describe the composition, location, and functions of perimysium, endomysium, and epimysium.
All contain lots of collagen:
Endomysium- Membranes that surrounds each muscle fiber. Also made of areolar connective tissue.
Perimysium- Membrane that holds together bundles of fibers which is called a FASICLE
Epimysium- Membrane that holds together groups of fasicles which make up a muscle
What is fascia? satellite cells? tendons? ligaments?
Fascia- found just outside of the epimysium
* an even denser sheet of fibrous connective tissue
* holds muscles together in functional groups.
Satalite Cells- embryonic stem cells found scattered between fibers and endomysium; help damaged muscle cells by enlarging, dividing, and fusing with them.
Ligament- fibrous tissue that connects bones to other bones
Describe the structures of actin, myosin, titin and nebulin in detail, and know tropomyosin and the 3 types of troponin.
h. Myosin (16nm)
* 2 heavy polypeptide chains: twisted rods + globular heads (cross bridges)
* 4 light chains
* Each thick filament has about 300 myosins
* Heads have ACTIN binding sites, ATP binding sites, and ATPases
i. Actin (8 nm)
* beaded double chain of globular proteins
* Has active sites to bind myosin cross bridges
* Two other proteins are associated with it
o Troponin - 3 subunits
o Tropomyosin - fibrous
* Very large PROTEIN
* elastic filament that attaches Z disk to myosin, and runs through myosin to the M line
* helps muscle spring back to shape after contraction.
(Fig. 9.4 and Fig. from another text).
* Protein that anchors ACTIN
* Runs from Z disk to Z disk along actin
3 types of troponin ??????????????
Describe the structure of a neuromuscular junction, and explain how a nerve impulse initiates muscle contraction
Structure: place where the end of a motor neuron (axion terminal?) "connects" with the muscle fiber.
a. An impulse travels down the neuron, reaches the axon terminal, and opens VOLTAGE-gated Ca+2 channels so Ca+2 enters the neuron from interstitial fluids [#1 on Fig. 9.12]
b. Ca+2 interacts with contractile proteins in the axon terminal, and they move the synaptic vesicles to the axon's pre-synaptic membrane, where EXOCYTOSIS occurs to release the contents of the synaptic vesicle. (containing a neurotransmitter chemical called Acetylcholine) [#2 & 3]
d. Ach diffuses across the synaptic cleft, and binds to receptors on CHEMICALLY-gated ion channels in the sarcolemma, which causes them to open and allow Na+ to enter the muscle cell. [#4 & 5]
(label or explain Fig. 9.11 or 9.12)
Be able to describe the Resting Membrane Potential and the process of Nervous stimulation of muscle contraction.
Resting Membrane Potential - established by passive Na+ and K+ ion channels and the Na+/K+ pump
- Inside of the cell:
* NEGATIVE charge just inside membrane
* higher concentration of K+
- Outside of the cell:
* POSITIVE charge just outside membrane
* higher concentration of N+
What is "excitation-contraction coupling"?
* Excitation-Contraction Coupling = linkage of nervous stimulation (excitation) with the events of contraction
* Basically, this means that "excitation from a nerve impulse causes contraction"
Relate this to Fig. 9.14 and be able to label / identify anything in this figure and explain what is occurring in the figure.
Describe the process of skeletal muscle contraction
1. Exposure of active sites - binding sites on actin
2. Cross bridge formation activated myosin heads bind to ACTIN binding sites, then ADP and Pi from previous contraction are released
3. Power stroke stored energy causes myosin head to pivot about 70o; this causes it to pull actin toward the center of the sarcomere (the M-line)
4. Cross bridge release new ATP binds to myosin head, causing it to let go of actin.
5. Hydrolysis of ATP ATP is hydrolyzed by ATPase, which gives myosin energy to return to its cocked position.
6. Recovery stroke - Myosin is in resting position, with ADP, Pi, and energy stored in head; cycle can repeat if continued CA+2 is available.
7. Each pulling stroke of the myosin results in muscle shortening of about 1%
- since muscles usually shorten as much as 30% during contraction, many pulling strokes must occur for a muscle to visibly contract.
8. Continual supply of Ca+ and ATP is necessary for this process to continue.
9. Ca+2 is actively pumped back into the SR when stimulation is no longer received, so muscle relaxes.
(called the Sliding Filament Theory of Contraction, Fig. 9.6).
Pay special attention to the role of calcium and ATP in the process.
Recognize the stages of Depolarization and Repolarization.
e. As Na+ rushes into muscle cell, it causes a change in the charge just inside the cell called a depolarization (inside becomes more +)
f. This causes nearby VOLTAGE-gated Na+ channels along the sarcolemma to open, so more Na+ rushes in, spreading the depolarization along the sarcolemma in a wave called an action potential.
Fig. 9.8(b) #3) Spread of a wave of depolarization (an ACTION POTENTIAL) 4) K+ then leaves the cell to bring polarity back to normal (called repolarization.)]
(Fig. 9.8 and 9.9).
Also be able to identify what is going on the the contraction steps shown in Fig. 9.15.
Recognize whether a sarcomere is relaxed or contracted, as shown in Fig. 9.6.
[A study activity (paragraph) will be posted on Blackboard to help you study #14 and 15, and may appear on the test in one form or another.] CARDS 43-48
muscular system terms: action potential; refractory period; All-or-None law; myoglobin; acetylcholinesterase; motor unit
action potential- spreading the depolarization along the sarcolemma in a wave
refractory period- Time when another stimulus can't produce a new fiber action potential (and therefore contraction)
All-or-None law-either a muscle FIBER contracts completely or not at all
myoglobin- red protein that stores oxygen
acetylcholinesterase- enzyme found in the synapse which quickly breaks down Ach so the sarcolemma is not continuously stimulated. One nerve impulse will therefore result in one muscle contraction (twitch).
motor unit- motor neuron + muscle fibers it invervates.
Define the parts of a single muscle twitch shown in Fig. 9.16 -- lag phase, contraction phase, relaxation phase.
1. Contraction of muscle in response to single stimulus
2. Lag phase?
3. Contraction phase?
Sacromeres are shortening
4. Relaxation phase?
Sacromeres are expanding
Define treppe (Fig. 9.18), multiple motor unit summation (Fig. 9.19), tetanus (Fig. 9.20).
Treppe occurs when muscle is well-rested and is stimulated repeatedly with maximal stimuli with complete relaxation between stimuli.
multiple motor unit summation
tetanus- increasing stimulation of muscle resulting in sustained maximal contraction
Describe the basic skeletal muscle length / tension relationship.
Higher the length, the more tension there is. ????
(shown in Fig. 9.21.)
Identify the overall summary reaction for aerobic cellular respiration; what occurs in the anaerobic phase vs. the aerobic phase?
ATP is produced by cellular respiration
2. Occurs in 2 phases:
a. Anaerobic phase (Glycolysis)
- Occurs in cell cytoplasm
- Results in breakdown of glucose to two 3-Carbon pyruvic acid molecules
- Yield is 2 ATP's
b. Aerobic phase [Pre-Krebs, Krebs Cycle, and Electron transport system (ETS)]
- Occurs in mitochondrial matrix (Pre-Krebs & Krebs Cycle) or cristae (ETS)
- Results in breakdown of pyruvic acids to CO2 + H2O
- Requires O2
- Yield is 34-36ATP's (most from ETS)
How is anaerobic energy production different from aerobic?
Aerobic is good for longer durations. Provides energy for hours
Anaerobic is good for up to 3 minutes
Describe the 3 ways that the supply of ATP is replenished in muscle tissue.
a. Phosphorylation of ADP by Creatine Phosphate (CP)
* muscles make CP when at rest
* muscles store 5x more CP than ATP
* very efficient process
* ADP + CP ----------------------> ATP + Creatine
* Provides energy for up to 10 seconds
b. Anaerobic respiration - glycolysis
* glucose taken from blood or stored glycogen
* only 2 ATP's produced per glucose
* pyruvic acid is converted to lactic acid
* much faster than aerobic, so useful for short bursts of intense activity
* Provides energy for up to 3 minutes
c. Aerobic respiration
* Uses glucose from glycogen, or fatty acids or amino acids
* Yields 36-38 ATP per glucose
* Slower process, so useful for sustained activity
* Provides energy for hours
Other terms to know: glycolysis; creatine phosphate; oxygen debt.
glycolysis-Anaerobic process during which glucose is converted to pyruvic acid; net of two ATP molecules is produced during glycolysis 3 min of energy
creatine phosphate-a. Phosphorylation of ADP by Creatine Phosphate (CP)
* muscles make CP when at rest
* muscles store 5x more CP than ATP
oxygen debt- extra O2 required when muscle contraction stops
- When O2 is available (to pay O2 debt):
- lactic acid produced in muscle is transported to the liver and converted to glucose
- creatine is converted to creatine phosphate
How are muscle fiber types classified? [fast vs. slow; aerobic (same as oxidative) vs. anaerobic (same as glycolytic)]
1. Names based on speed of contraction and type of energy production used.
2. Energy production:
* oxidative (aerobic)
* glycolytic (anaerobic)
3. Speed of contraction:
* slow-twitch oxidative (Type I)
* fast-twitch oxidative (Type IIa)
* fast-twitch glycolytic (Type IIb)
4. Most muscles contain mixtures of the 3 types, but some people have more of one type than another.
What kinds of body activities rely more on slow twitch vs. fast twitch fibers?
What other differences would you expect to see between these fibers?
(See Table 9.5)