Muscle physiology Flashcards
The action of skeletal muscles are regulated by?
α-motor neurons of brain stem and spinal cord
What is a motor unit?
A motor neuron with all its connecting muscles fibers
Finish the sentence:
One neuron can innervate several muscle fibers, but
one muscle fiber is innervated by only one neuron.
What is a muscle spindle?
The sensory organ that responds to changes in muscle length – stretch detector
specialized muscle fibers essentially
Muscle spindles are innervated by?
both sensory and motor nerve fibers
What type of fibers are found in muscle spindles?
(3-12) intrafusal fibers
What is the golgi tendon organ?
The sensory organ that responds to changes in muscle tension - a type of proprioceptor
consists of sensory nerve endings interwoven between collagen fibers
What type of fibers are found in the golgi tendon organ?
(10-12) extrafusal fibers
The golgi tendon organ is innervated by?
sensory nerve fibers
Where is the golgi tendon organ found?
Located in the tendon near its fusion with the muscle
muscle fibers enveloped by?
endomysium
muscle fibers, myofibrils, enveloped by?
endomysium
whole muscles enveloped by?
epimysium
What is a sarcomere?
the basic contractile unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band.
Which filaments are thick?
myosin
Which filaments are thin?
actin
In a resting muscle fiber, the binding sites for myosin head on the actin molecules are masked by?
protein tropomyosin.
To each tropomyosin molecule, what protein is attached?
troponin
Troponin has binding sites for what?
for Ca 2+
When an AP is conducted along a motor nerve fiber through the synapsis, what happens?
Ca 2+ is released from the sarcoplasmatic reticulum
What happens when released Ca 2+ binds to troponin?
structure of troponin changes which in turn causes the
tropomyosin molecules to change position
this is followed by the binding sites for the myosin
head on the actin filament to open
What happens after binding sites are exposed on the actin filaments?
Myosin heads bind to the actin filaments →
myosin heads bend and the actin
filaments slide relative to the myosin filaments
What causes the bonds between actin and the myosin heads to break?
ATP binds to the myosin heads causing the bonds to break and the filaments separate
How do the myosin heads straighten back to their primary position?
ATP is hydrolysed, energy is released and transferred to the myosin heads allowing them to straighten
Finish the sentence:
As long as Ca 2+ is bound to troponin, the muscle fiber keeps?
contracting.
Define isotonic muscle contraction.
Isotonic – muscle shortens but the tension does not change
- limb movements
• Isometric – muscle does not shorten but the tension in the muscle
rises
- preserving the body position
• Auxotonic – both contraction and tension change
- characteristic to most of the muscle contractions
Define isotonic muscle contraction.
muscle shortens but the tension does not change
- limb movements
Define isometric muscle contraction.
muscle does not shorten but the tension in the muscle
rises
- preserving the body position
Define auxotonic muscle contraction.
both contraction and tension change
- characteristic to most of the muscle contractions
describe muscle fiber type: I – slow (oxidative fibers)
high content of myoglobin, lots of mitochondria,
small ø, lots of capillaries, gets tired slowly
(endurance capacity, long distances with slow speed)
describe muscle fiber type: IIA – fast (oxidative-glycolytic)
myoglobin content lower, less mitochondria,
medium ø, gets tired moderately
describe muscle fiber type: IIX(B) – fast (the fastest) (glycolytic)
thick fibers (large ø), few capillaries and mitochondria, little myoglobin, fast contractions, gets tired fast
(speed capacity, short distances with maximum speed)
Gross division for muscle fiber types in horses?
3 pure types
2 hybrid types
What are the 3 pure muscle fiber types found in horses?
I, IIA and IIx
What are the 2 hybrid muscle fiber types found in horses?
I/IIA and
IIA/IIx
