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A & P1 for PCP > Lecture 14 - Musculoskeletal system 4: muscles > Flashcards

Lecture 14 - Musculoskeletal system 4: muscles Flashcards

1
Q

What is the function of pectoralis major

A

Flexes the arm

-adducts the arm anteriorly and draws it across the chest

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2
Q

What is the function of the latissimus dorsi

A

Extends the arm

-adducts the arm posteriorly

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3
Q

What is the function of the deltoid

A

Abducts the arm

-assist in flexion and extension of the arm

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4
Q

What is the function of supraspinatus

A

Assists in abducting the arm

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5
Q

What is the function of Teres minor

A

Rotates the arm outward

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6
Q

What is the function of Teres major

A

Assists in extension, adduction, and medial rotation of the arm

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7
Q

What is the function of Infraspinatus

A

Rotates the arm outward

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8
Q

What is the function of Subscapularis

A

Medial rotation

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9
Q

What is the function of biceps brachii

A

Flexes the supinated forearm

-supinates forearm and hand

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10
Q

What is the function of brachialis

A

Flexes the forearm

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11
Q

What is the function of brachioradialis

A

Flexes the semi pronated or semi supinated forearm

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12
Q

What is the function of triceps brachii

A

Extends the lower arm

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13
Q

What is the function of pronator teres

A

Pronates and flexes the forearm

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14
Q

What is the function of pronator quadratus

A

Pronates the forearm

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15
Q

What is the function of supinator

A

supinates the forearm

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16
Q

What are 3 main functions of muscle

A
  1. movement
  2. heat production
  3. posture
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17
Q

What are 4 characteristics of muscle

A
  1. excitability
  2. contractility
  3. extensibility
  4. elasticity
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18
Q

what’s are 3 unique characteristics of myocytes

A
  1. sarcolemma: plasma membrane
  2. Sarcoplasma: cytoplasm (fluid matrix)
  3. Nucleus: many poly nucleated cells and is close to sarcolemma
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19
Q

What is in Sarcoplasma

A

ATP,
Glycogen(reserve)
Myoglobin (analogue hemoglobin)(binds to oxygen)
-basically protein that helps carry O2

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20
Q

What is T-tubule

A

Transverse tubule :

  • perpendicular extensions of the sarcolemma
  • Penetrates into cell
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21
Q

What is sarcoplasmic reticulum (S.R.)

A
  • contains lots of Ca2+

- membrane has a Ca2+ pump to help accumulate it

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22
Q

What are myofibrils

A

Bundles of cytoskeleton filaments

  • 1000+ per cell
  • made of myofilaments (actin = thin or myosin = thick filament)
  • each one is surrounded by sarcoplasmic reticulum (responsible for the contraction)
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23
Q

Describe microfilament actin

A
  • thin filament that consists of actin molecules (kidney shaped) twisted into a helix (rope like)
  • has sites that interact with myosin HEADS
  • at rest this site is hidden by the tropomyosin protein that is held by troponin protein
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24
Q

Describe microfilament myosin

A
  • thick filament
  • interwoven into sarcomere (Z-line)
  • 200 myosin molecules per myofilament
  • loos like 2 interwoven golf clubs
  • has bilobed head that is exposed and a tail which is parallel to the cells
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25
Q

What is sarcomere

A

The basic contractile unit for striated muscle cells
- about 15000 per myofibril
They are organization of the myofilaments actin and myosin

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26
Q

What is movement of sarcomere and myofilaments during a contraction

A

Sarcomere shortens during contraction and myofilaments (actin and myosin) slide on top of one another

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27
Q

what makes visible bands/ striations on skeletal muscle when we look in microscope

A

The way the filaments are organized

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28
Q

What is the Z-disk

A

Anchor for thin myofilaments

-elastic filament (Titin) attaches myosin and actin to the Z disk thus ensures the structural stability of the sarcomere

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29
Q

What is M-line

A

Line of M-proteins that hold the myosin filaments

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30
Q

What is A-band

A

Runs the entire length of myosin filaments

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31
Q

What is I-band

A

Includes Z-disk and ends of actin filaments

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32
Q

What is H-band

A

Region of myosin filament with no overlapping actin filaments

33
Q

What do myosin heads have

A
  • a site to link actin

- a site to link ATP

34
Q

What is initiation of sliding filament theory of contraction

A

Ca is released from the sarcoplasmic reticulum to the sarcoplasm (membrane)

35
Q

What is the sliding filament theory of contraction

A
  • myosin head stores ADP+ and P+
  • Ca2+ from S.R. binds to troponin
  • tropomyosin shifts from blocking active site on actin
  • myosin head binds to active site then releases ADP+ and P+
  • release of those molecules gives myosin head energy to pull actin molecule
  • ATP binds to myosin and myosin is released from the active site
36
Q

during contraction, each actin is bound to:

A

millions of cross bridges of myosin

37
Q

do all the bonded actin-myosin groups detach at the same time

A

no they need to keep tension on the actin myofilament

38
Q

what happens during relaxation in sliding filament theory of contraction

A
  • Ca2+ reabsorbed

- tropomyosin hides the link site on actin

39
Q

when does rigor mortis usually set in

A

3-4 hrs after death (max 12 hrs)

-this is because Ca2+ is slowly realeased in the sarcoplasm which causes the contraction

40
Q

Why is rigor mortis a continuous contratioc

A

because ATP is no longer available (cells are no longer active)
-the myosin heads stay bonded to actin filaments and contraction is maintained

41
Q

what causes relaxation after rigor mortis

A

after 48-60 hrs the muscles relax again due to the degradation of the contractile proteins

42
Q

What are the energy sources for contractions

A

ATP
Glucose & Oxygen
Catabolic Pathways
Heat production

43
Q

how many seconds of contraction can muscle get with resynthesized ATP

A

2-4s so constantly resynthesizing

44
Q

What is a secondary source for resynthesizing ATP and how many seconds of contraction can the muscle achieve

A

Creatine phosphate and can get 20s of contraction

45
Q

How is ATP resupplied

A

through cellular respiration

46
Q

What happens if there is no more ATP going to muscles

A

End of contractions

47
Q

What is glucose and oxygen role in energy source for contractions

A
  • release of energy from glucose in cellular respiration produces ATP
  • Muscle fibers store glucose as glycogen
  • Oxygen is stored in muscle as myoglobin
48
Q

What are the catabolic pathways used to produce ATP

A

Aerobic: -max energy, requires a lot of oxygen
Anaerobic:-no immediate need of oxygen
-rapid
-results in fermentation of lactic acid
-when oxygen available, lactic acid can be converted back to glucose in liver
-excess post exercise oxygen consumption

49
Q

What is heat production role in energy source for contraction

A
  • as catabolic processes not 100% efficient; thermogenesis
  • important for homeostasis
  • shivering thermogenesis
50
Q

What is a motor unit of muscle

A

combination of:

  1. Motor neurons
  2. Grps of myocytes they innervate
51
Q

What is the motor nerve that each muscle receives one of

A
  • contains hundreds of myelinated axons
  • branches into many axon terminals
  • each terminal forms a neuromuscular junction with 1 myocyte
52
Q

How are cells of a motor unit dispersed

A

-interconnected by gap junctions so they can contract together

53
Q

The # of myocytes in a motor unit depends on:

A

the muscle itself

  • ex. 2000 cells in 1 motor unit = very strong muscle like arm, thigh
  • ex. a few cells in motor unit = precision muscle like larynx
54
Q

What is a muscle twitch

A

aka - muscle fasciculation

  • depolarization of small muscles leading to transient muscle contraction
  • contraction that follows only 1 nervous stimulation
  • intensity depends on the # of motor units involved
55
Q

What are 3 phases of muscle twitch

A
  1. latent period
  2. period of contraction
  3. period of relaxation
56
Q

What is latent period of muscle twitch

A
  • myocyte does not shorten at this point
  • myosin heads start to pullon actin & titin stretchs
  • time needed for excitation- contraction = few ms
57
Q

What is period of contraction of a muscle twitch

A
  • The force genrated is greater than the resistance and so the muscle shortens
  • duration up to 100ms
58
Q

What is the period of relaxation in muscle twitch

A
  • Ca2+ is reabsorbed in the sarcoplasmic reticulum (S.R.) and contraction stops
  • duration more than 100ms
59
Q

What dictates the speed at which a muscle will contract

A

Depending on their function, myocytes of different muscles will contract faster or slower due to many variations in the cells proteins
-The bigger the muscle, the longer it takes for the contraction and relaxation

60
Q

What needs to be done in order to affect the force of contraction

A
  • increase the frequency of stimulation (temporal summation and tetanus)
  • increase the intensity of stimulation (multiple motor unit summation)
61
Q

What is temporal summation (T.S.) or wave summation

A
  • When a skeletal muscle is stimulated twice in a short interval of time
  • The magnitude of the 2nd contraction will overlap with the 1st because the Ca2+ released by 1st hasn’t been completely reabsorbed, making 2nd contraction a bit stronger
62
Q

What is tetanus

A
  • Rapid stimulation of a skeletal muscle
  • Results in a continuous or prolonged type of contraction
  • Normal state: the nerve impulses rapidly arrive to the motor units & provoke a tetanus instead of an isolated twitch
  • complete tetanus = contractions are all fused
63
Q

What is muscle tone or tonus

A
  • Tension of skeletal muscles at rest
  • when you stimulate a muscle, it is voluntary (ATP & Ca2+ essential for contraction)
  • Healthy & resting skeletal muscles are always slightly contracted but without producing any movement(involuntary)
  • spinal reflexes activate a grp of motor units activating the muscles and tendons governing stretch
64
Q

Function of tonus

A
  • stabilize articulations

- maintain posture

65
Q

Myocytes are often metabolically minimally active, when are they intensely active

A

when they contract

66
Q

What is the quantity of ATP present in myocytes

A

small only 4-6 sec. of contraction

-ATP is the energy source used for contraction

67
Q

What 3 pathways to obtain ATP

A
  1. Direct phosphorylation(~15 sec)
    - release of energy from ATP bond breaking
  2. Anaerobic glycolysis & lactic acid production(30-60s)
    - ATP formed from breaking glucose down in pyruvate
  3. Aerobic respiration(for many hrs)
    - Kreb’s cycle, ETC
    - Oxygen required
    - myoglobin and hemoglobin transport
68
Q

What are the smooth muscles

A
  • small, fusiform,
  • not striated as myofilaments not organized with sarcomere
  • sarcolemma has no T tubules
  • central nucleus due to network arrangment of myofilaments
  • contains least S.R.
  • Endomysium = CT w/ blood vessels & neural fibers
  • found in viscera / walls of hollow organs
69
Q

Events that differ in smooth muscle contraction

A

Calcium attaches to calmodulin (on myosin) and is activated

-Calmodulin functions slowly, so slows calcium effect on contraction

70
Q

What are 2 types of smooth muscle

A
  1. Single unit smooth muscle (visceral)

2. multiunit smooth muscle

71
Q

What is single unit smooth muscle(visceral)

A
  • has important gap junctions that link networks
  • has pacemaker cells
  • neurons of the autonomic nervous system innervate a few smooth myocytes & the action potentials spread to other networks
  • hormones influence complete networks
  • ex. bladder, uterus, digestive sys.
72
Q

What is multiunit smooth muscle

A
  • not many gap junctions
  • each myocyte has synapses (neuromuscular junctions) btw neuron & myocyte w/ the ANS
  • React to hormonal regulation
  • ex. large arteries, large airways, arrector pili muscles
73
Q

What is myalgia

A

Pain in the muscle bcs of a myopathy (muscular disease)

74
Q

What is myositis

A

muscle inflammation

75
Q

What is tetanus

A
  • infectious disease
  • acute: fast acting, not lengthy in time, can die suddenly
  • Chronic: slow acting, over prolonged period of time
  • caused by a toxin frm Clostridium tetani (bacteria)
  • =painful spasms & contractures (jaw, cervical, trunk, limbs)
  • w/o vaccination can die of respiratory failure
76
Q

What is poliomyelitis

A
  • viral inf. of body frm polio virus
  • sometimes asymptomatic
  • infection travels along motor neuron pathway
  • leads to paralysis and death
  • no tx once infected
77
Q

What is Duchenne progressive muscular distrophy

A
  • hereditary disease, recessive, linked to sex (almost always in men
  • muscle hypertrophy (fat & CT deposits)
  • myocytes degenerate & atrophy
  • missing dystrophin: maintain integrity of the sarcolemma
78
Q

What is myasthenia gravis

A
  • Chronic weakness, especially in face & throat
  • begin w/ mild weakness progress to longer periods & more muscles involved
  • resp fail possible
  • caused by autoimmune malfunction, ACh receptors in sarcolemma are targeted
  • leads to impulses that are unable to produce full contractions

A & P1 for PCP (19 decks)

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