Muscle physiology

Question 1

The action of skeletal muscles are regulated by?

Answer 1

α-motor neurons of brain stem and spinal cord

Question 2

What is a motor unit?

Answer 2

A motor neuron with all its connecting muscles fibers

Question 3

Finish the sentence:

One neuron can innervate several muscle fibers, but

Answer 3

one muscle fiber is innervated by only one neuron.

Question 4

What is a muscle spindle?

Answer 4

The sensory organ that responds to changes in muscle length – stretch detector

specialized muscle fibers essentially

Question 5

Muscle spindles are innervated by?

Answer 5

both sensory and motor nerve fibers

Question 6

What type of fibers are found in muscle spindles?

Answer 6

(3-12) intrafusal fibers

Question 7

What is the golgi tendon organ?

Answer 7

The sensory organ that responds to changes in muscle tension - a type of proprioceptor

consists of sensory nerve endings interwoven between collagen fibers

Question 8

What type of fibers are found in the golgi tendon organ?

Answer 8

(10-12) extrafusal fibers

Question 9

The golgi tendon organ is innervated by?

Answer 9

sensory nerve fibers

Question 10

Where is the golgi tendon organ found?

Answer 10

Located in the tendon near its fusion with the muscle

Question 11

muscle fibers enveloped by?

Answer 11

endomysium

Question 12

muscle fibers, myofibrils, enveloped by?

Answer 12

endomysium

Question 13

whole muscles enveloped by?

Answer 13

epimysium

Question 14

What is a sarcomere?

Answer 14

the basic contractile unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band.

Question 15

Which filaments are thick?

Answer 15

myosin

Question 16

Which filaments are thin?

Answer 16

actin

Question 17

In a resting muscle fiber, the binding sites for myosin head on the actin molecules are masked by?

Answer 17

protein tropomyosin.

Question 18

To each tropomyosin molecule, what protein is attached?

Answer 18

troponin

Question 19

Troponin has binding sites for what?

Answer 19

for Ca 2+

Question 20

When an AP is conducted along a motor nerve fiber through the synapsis, what happens?

Answer 20

Ca 2+ is released from the sarcoplasmatic reticulum

Question 21

What happens when released Ca 2+ binds to troponin?

Answer 21

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

Question 22

What happens after binding sites are exposed on the actin filaments?

Answer 22

Myosin heads bind to the actin filaments →

myosin heads bend and the actin
filaments slide relative to the myosin filaments

Question 23

What causes the bonds between actin and the myosin heads to break?

Answer 23

ATP binds to the myosin heads causing the bonds to break and the filaments separate

Question 24

How do the myosin heads straighten back to their primary position?

Answer 24

ATP is hydrolysed, energy is released and transferred to the myosin heads allowing them to straighten

Question 25

Finish the sentence:

As long as Ca 2+ is bound to troponin, the muscle fiber keeps?

Answer 25

contracting.

Question 26

Define isotonic muscle contraction.

Answer 26

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

Question 27

Define isotonic muscle contraction.

Answer 27

muscle shortens but the tension does not change

- limb movements

Question 28

Define isometric muscle contraction.

Answer 28

muscle does not shorten but the tension in the muscle
rises
- preserving the body position

Question 29

Define auxotonic muscle contraction.

Answer 29

both contraction and tension change

- characteristic to most of the muscle contractions

Question 30

describe muscle fiber type: I – slow (oxidative fibers)

Answer 30

high content of myoglobin, lots of mitochondria,
small ø, lots of capillaries, gets tired slowly

(endurance capacity, long distances with slow speed)

Question 31

describe muscle fiber type: IIA – fast (oxidative-glycolytic)

Answer 31

myoglobin content lower, less mitochondria,

medium ø, gets tired moderately

Question 32

describe muscle fiber type: IIX(B) – fast (the fastest) (glycolytic)

Answer 32

thick fibers (large ø), few capillaries and mitochondria, little myoglobin, fast contractions, gets tired fast

(speed capacity, short distances with maximum speed)

Question 33

Gross division for muscle fiber types in horses?

Answer 33

3 pure types

2 hybrid types

Question 34

What are the 3 pure muscle fiber types found in horses?

Answer 34

I, IIA and IIx

Question 35

What are the 2 hybrid muscle fiber types found in horses?

Answer 35

I/IIA and

IIA/IIx