CH 18 Pt Cd Flashcards
Fusiform muscles
Long fibers, high FL: ML ratio
-hamstring, dorsiflexor
-spindle like, long and narrow
-low physiological cross sectional area
Pennants muscles
Short fibers, low FL:ML ratio
-quad, plantar flexors
-fan like fascicles
High physiological cross sectional area
PCSA changes how
With the muscle fibers directions
The more fibres packed into the PCSA…
The greater the force it can produce
The more fibres packed into the PCSA…
The greater the force it can produce
Short fibers create greater force in a pennate muscle, so the greater the force…
The lower the velocity, thus long fibers create greater velocity
Fiber Arrangement Influences: (2)
Force Generating Capacity
-fusiform: longer working range, lower max force
-pennate: 2X force of fusiform
Range of Motion
-fusiform muscle exhibits greater ROM as compared to pennate muscles
What stage of a push-up is hardest and why?
The start because when muscles are really stretched or shortened, they will be weaker as they need to get to the other “side” of their extreme
At any absolute force
The speed of movement is greater in muscle with higher percent of fast twitch fibers
What shortens during a contraction?
Sarcomere
During contraction:
The length of the thick and thin filaments do not change
The eight of the sarcomere decreases as actin is pulled over myosin
Main molecule used for energy in muscle contraction is from:
ATP hydrolysis
-atp is broken down into ADP+ Pi+ Energy
Globular head of myosin contains:
Actin activated myosin ATPase
Relaxed state/ Detached/ At Rest:
Myosin on the globular head
-atp attached to binding site on globular head
-actin binding site is empty
-myosin binding site on actin is covered by Troponin and Tropomyosin
- Actomysoin complex
If binding site is available, loose binding between actin and myosin
-ADP and Pi both still attach to the globular hear
- Power Stroke
Pi released= tightens binding
-myosin head conformation change
-reposition angle of attachment
Myosin pulls actin towards M-line
Sliding Filament Model Review
- ATP bound to myosin
- ATP hydrolysis, energy stored in myosin head
- Loose binding between myosin and actin
-ATP broken down to ADP+ Pi + Energy - Pi is released -tightens binding
- Conformational change of myosin head
- Starts pulling of actin towards M-line (cross bridge movement)
- Myosin drops ADP as it moves
- New ATP binds to myosin
- Release of myosin head from actin (cross bridge disassociates)
Actin, Myosin, and ATP Review
- Myosin head bound to ATP
- ATP hydrolysis, energy stored in globular head
- Myosin loosely interacts with actin
- Pi released, myosin and actin bonds tightens
- Myosin cross bridge movement starts to creature sliding motion
- ADP released
- Myosin bins with new ATP, acctomyosin complex dissasociates
What are regulatory proteins? (2)
Troponin and Tropomyosin
What is steric blocking
Inhibitory action of regulatory proteins
Physiological mechanism of excitation- contraction coupling
Electrical discharge at muscle initiates chemical events at cell surface
SR releases intracellular Ca2+
Ca2+ combines to Troponin Troponin pulls tropomyosin off active actin sites (removes inhibitory)
Allows actin to combine with myosin
Relaxation of Muscle Process:
Ca2+ is actively pumped out and back into the SR by SR ATPase
-removal of Ca2+ restores inhibitory action of Troponin- tropomyosin
Troponin allows tropomyosin to interfere with actin- myosin interaction
If a muscle fibre has greater SR ATPase what characteristic would it demonstrate?
Fast twitch/ Type 2 properties as it fatigues faster
EC Coupling and Sliding Filament Model: Step 1
Depolarizationn of T-tubule system causes Ca2+ release from lateral sacs of SR
-Ca2+ binds to Troponin- tropomyosin in actin filaments, releasing inhibition that prevented actin from combining with myosin
Actin combines with myosin
