Bio Class 10 Flashcards
Function of muscles
Voluntary control
Location of muscles
On bones
Nuclei in muscles
Multinucleated
Microscopic appearance of muscles
striated
Hierarchy of muscle composition
Protein filaments (actin & myosin) –> Sarcomere (arrangement of myosin & actin in a specific way) –> myofibril (sarcomere lined end to end) –> muscle cell fiber *myofiber (bundle of myofibrils + plasma membrane, some organelles, fibroblast) –> fasicle (bundle of myofiber) –> whole muscle (bundle of fasicles)
Which muscles have sarcomeres?
Cardiac muscles
Why do skeletal muscles have t-tubules?
Skeletal muscle is really thick so need T-tubules to carry AP deep into cell
H-zone
Region of only myosin
A band
Region of entire myosin with some actin
I band
Region of actin between each myosin
Z line
Beginning to end of each sarcomere
What happens to the sarcomere upon contraction?
H zone & I band will disappear, A band will remain the same; myosin will attach to actin and pull it closer bringing the Z line closer to myosin each time
Sliding Filament Theory
- Myosin head will bind to actin in presence of Ca2+; also called “cross bridge formation”
- Myosin pulls actin towards center of sarcomere; called “power stroke” but NO ATP
- In presence of ATP, myosin will bind to ATP and release actin
- Myosin resets to high energy conformation; requires ATP hydrolysis
After each round of steps 1-4, Z line will get closer and closer to thick filament
Excitation-Contraction Coupling
Tropomyosin binds to actin and blocks the sites of myosin binding
- tropomyosin is attached to troponin which has a binding site for Ca2+
- When Ca2+ is present, troponin will make tropomyosin move apart, unblocking the myosin sites which will allow contraction to happen
What happens to muscles when you run out of ATP?
You can’t relax, myosin will stay bound to actin and you will stay contracted
Do myosin heads operate asynchronously or synchronously?
Asynchronously because if they worked in the same way then they would all bind to actin at the same time & release at same time so the Z line will just snap back to its original position
Bohr-shift
Shift to right:
increases carbon dioxide
increases temperature
decreases pH
What happens to oxygen affinity & delivery during exercise?
Hb affinity to o2 during exercises decreases, while delivery to tissues increases
- will shift to the right
Motor Unit
motor neuron and all muscle cells under its control
Large Motor unit vs small motor unit
Large
- 1000 muscle cells per neuron
Small
- 10-20 muscle cells per neuron
Gross vs fine motor control
Gross
- Eg. big scale movements like running
- few large motor units
Fine
- Eg. precision so things like eye movement
- many many small motor units
How can you address oxygen debt?
- Replenish oxygen on myoglobin
- Convert lactic acid to something useful (so you want to oxidize lactic acid back to pyruvate or maybe even all the way to glucose through gluconeogenesis)
Muscle Energy Sources
- Creatine-P + ADP –> Creatine + ATP
- Glycolysis
- Aerobic Respiration (Krebs, PDC, ETC)
Myoglobin
Stores oxygen
- one polypeptide so no cooperative binding
Fiber Types
Slow twitch
Fast Twitch Type IIA
Fast Twitch Type IIB
Slow Twitch: Myoglobin Content Capillary Network Speed of contraction Mitochondrial # Fatigue resistance Force generated Example
- also known as “red slow twitch or red oxidative fibers”
- high with myoglobinc
- dense capillary network
- slow contaction
- high mito #
- extended contraction with no fatigue
- low force
- Eg. Leg muscle of marathon runner
Fast Twitch Type IIa: Myoglobin Content Capillary Network Speed of contraction Mitochondrial # Fatigue resistance Force generated Example
- also known as “fast twitch oxidative fibers”
- lower myoglobin
- less dense capillary network
- intermediate contraction
- some mito #
- ~30 mins
- medium force
- Eg. Leg muscle of 400 m fast runner
Fast Twitch Type IIb: Myoglobin Content Capillary Network Speed of contraction Mitochondrial # Fatigue resistance Force generated Example
- also known as “white fast twitch fibers”
- very low myoglobin
- very few capillary network
- fast contraction
- very few mito #
- ~1 min
- explosive force
- Eg. Chicken breasts
Cardiac vs Smooth Muscle
Cardiac
- uninucleated
- involuntary
- in heart
- striated (actin & myosin organized into sarcomeres)
Smooth
- uninucleated
- involuntary
- walls of hollow organs
- nonstriated (myosin and actin randomly in place)
_____blast vs _____cyte
- blast:
- still dividing
- produces the matrix
- immature bone cells
- cyte:
- not dividing
- maintains matrix
- mature bone cells
What is the matrix composed of?
Fibers (elastic or collagen) Glop substance (liquid = plasma, solid = bone)
Bone function (skeletal system function)
- Support & movement
- Protection
- Mineral storage
- Blood cell formation
Long Bone anatomy
2 epiphysis & a diaphysis
- epihysis is protruding end with spongy bone
- diaphysis is composed of compact bone
