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Physiology > Musculoskeletal > Flashcards

Musculoskeletal Flashcards

1
Q

Skeletal muscles is composed of ……. which are attached by ….. to the skeletal system

A

Myofibers (multinucleated, surrounded by sarcolemma)

tendons

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2
Q

The shortening of the skeletal muscle results from increase of ………. towards the center of the …… . This method is called …..

A

the extent of thin-thick filaments overlap
sarcomere
the sliding filament mechanism

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3
Q

When the actomyosin complex is formed, the head undergoes ……..

A

conformational change displacing the thin filament toward the center of the sarcomere

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4
Q

In skeletal muscle contraction, Power stroke means ………

A

the dissociation of Pi from the ADP, which leads to the acceleration of the tilting step
* The molecular event in this cycle is driven ty the hydrolysis of ATP

See P. 516 if not clear

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5
Q

In skeletal muscle contraction, the dissociation of ADP from the tilted head leads to …..

A

attachment of a new ATP from the cytoplasm, and the dissociation of the head

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6
Q

In skeletal muscle contraction, the final step involves …..

A

the hydrolysis of ATP, and repositioning of the myosin head for another cycle

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7
Q

In skeletal muscle contraction, if ATP runs out, this leads to ……

A

trapping of the myosin head in the tilted state, also know as rigor state
* Example is rigor mortis

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8
Q

Excitation contraction coupling means ………

A

the mechanism by which an AP by a motor neuron leads to skeletal muscle contraction

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9
Q

AP in the myofiber leads to the release of ….. from the …..

A

Ca, sarcoplasmic reticulum

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10
Q

Both troponin and tropomyosin are located on ……. . State the subunits with their functions

A

the actin filament
* Troponin is a complex of subunits T,I,C.
C binds Ca, while T binds to tropomyosin, and I binds to T and inhibits its action
* Binding of Ca to subunit C shifts the position of the tropomyosin in respect to the actin filament, exposing the myosin binding site
* Ca-ATPase of the sarcoplasmic reticulum depletes Ca and restores the inactivation state of actin

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11
Q

In skeletal muscle contraction, a single AP results in ….

A

a single muscle twitch, that occurs 2 miliseconds after depolarization (during repolarization)

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12
Q

Define

  1. Isometeric contraction
  2. Isotonic contraction
  3. Dynamic contraction
A
  1. muscle length is fixed, tension increases
  2. muscle length shorten, tension constant
  3. both length and tension change. It is two types, Concentric (muscle shortens) & eccentric (muscle pulled out)
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13
Q

Ryanodine receptor is …..

A

located on the sarcoplasmic reticulum. When activated by Ca, leads to release of more Ca from the sarcoplasmic reticulum (Ca induced Ca release).
* Succinylcholine (general anesthetic) causes inhibition of this receptor and release of large amount of Ca, and subsequent overheating (malignant hyperthermia).

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14
Q

In isometric contraction, the tension developed depends on ……

A

the length of the muscle

* There is an optimal length for the development of maximum muscle tension

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15
Q

The total force generated by many sarcomeres acting in series is the same as that of one sarcomere. T/F??

A

True
because the forces act in opposing direction on both side of the Z line and cancel each other
* This means that sarcomeres in the same myofibril do not generate additive force
* The more sarcomeres arranged in series, the faster the shortening of the muscle

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16
Q

The force that the muscle generates is proportional to …..

A

the cross sectional area of the contractile material.

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17
Q

In isotonic contraction, the velocity of contraction is inversely proportional to the ……….

A

load

* At zero velocity, the contraction becomes isometric. This is the maximum active force of the muscle at this point

18
Q

What is difference between fast & slow muscle fibers??

A
  1. Fast: white, large in diameter, less mitochondria, depends on anaerobic glycolysis, high myosin ATPase, and high in SR and T tubules content. Allow finer movements.
  2. Slow: Red (myoglobin), high mitochondria, small diameter, oxidative phosphorylation used for energy, low myosin ATPase, and low in SR and T tubules content, smaller motor end plates, high capillary content
19
Q

Muscles with less sarcoplasmic reticulum contracts slowly because …..

A

less Ca is released, and contraction takes longer because of the slower removal of Ca

20
Q

The motor unit consists of …… & ……

A

all muscle fibers & a single alpha motor neuron axon

* Excitation of the alpha motor neuron results in contraction of all the fibers in the motor unit

21
Q

Changing the firing rate of an alpha motor neuron leads to ……

A

change in the muscle type (fast or slow)

* If the nerve is destroyed,, all related muscle fibers atrophy

22
Q

Length and tension in a skeletal muscle depends on ……

A

rate of firing of the motor neuron

* All motor neuron inputs are excitatory & reach threshold

23
Q

Neuronal cell bodies of the alpha motor neuron are located in …….

A

the ventral horn of the spinal cord gray matter

* Alpha motor neurons are myelinated

24
Q

Initiation of contraction for the skeletal muscle occurs in …… & ……

A

cerebral cortex and the cerebellum

25
Q

Before tension in a skeletal muscle is exerted, stretching of ……..

A

all elastic element in the muscle (tendons, CT) must occur.

26
Q

Tension in skeletal muscles does not build in a single twitch because …..

A

by the time the slack is removed, the single twitch begin to decline

27
Q

Tetanus is …….

A

summation of all muscle contractions during repetitive stimuli within a short time.
Ca availability will be increased from repeated contractions
* Tetanus can continue until fatigue is developed due to lactic acid accumulation

28
Q

Graded tension forces in skeletal muscles can be developed by ……

A

increasing the number of motor units and increase firing rate

29
Q

What are the two types of skeletal muscles receptors??

A
  1. Muscle spindles: located between the fibers (intrafusal)

2. Golgi tendon organ: in the tendons, arranged in series with the muscle fibers

30
Q

Muscle spindles consist of two parts, …. & ….

A

Nuclear bag & nuclear chain (depending on the arrangement of the nuclei in their equatorial region)

31
Q

What is the innervation of the muscle spindles?

A
  1. Gamma motor neuron (efferent): controls the tone and contraction of the muscle spindles during activity. Input is from the CNS
  2. Ia fibers (primary, annulospiral, afferent): fast, innervate nuclear bag & chain. Detect dynamic Δ in muscle length.
  3. II fibers (secondary, flower spray, afferent): slower, innervate the nuclear chain only. Detect the static Δ in muscle length
32
Q

Golgi tendon fires when ……….

A

the muscle contracts, stretching the tendons

* GTO responds to muscle tension, while muscle spindles respond to change in length

33
Q

Golgi tendons are supplied by …… afferents, with their function being …….

A

type Ib
* These fibers synapse on inhibitory interneurons, which inhibit alpha motor neurons to prevent damage to the skeletal muscle

34
Q

Both skeletal muscle afferents fire if …….

A

the muscle is stretched

  • If the stretched muscle contract, spindles cease its discharge, while GTO increases.
  • Muscle spindles are arranged in parallel, while the GTO are in series with the myofibers
35
Q

Smooth muscles are usually …….. than skeletal muscles, and have less …. & ….

A

smaller & uninucleated
myofibrils per cell
myosin
* Also, no T tubules and sparse SR

36
Q

The analogous to Z line in the smooth muscle is …..

A

Dense bodies

  • it is the site of actin insertion
  • Also located in the cell membrane, so it causes deformation of the cell during contraction
37
Q

Excitation-Contraction coupling in smooth muscles is mediated by …… because

A

myosin kinase, because there’s no troponin

38
Q

What is the function of satellite cells???

A

Regeneration of muscle cells

39
Q

Each sarcomere has …… T-Tubules

A

two

40
Q

Ca enters the smooth muscle and binds to ….., which it activates the …..

A

calmodulin
myosin kinase
* Phosphorylation of myosin enables it to interact with actin.
* Each contraction cycle requires 1 ATP

41
Q

……. are located at the junction of the I & A band

A

T tubules

Physiology (10 decks)

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