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Human SF > Histology of Muscle Tissue > Flashcards

Histology of Muscle Tissue Flashcards

1
Q

What are the classifications of muscle?

A
  • Appearance (straited, non straited)

- controlled by somatic or autonomic nervous system (voluntary or involuntary)

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2
Q

What are the three types of muscle?

A
  • Skeletal (straited voluntary)
  • Smooth (non straited, involuntary)
  • Cardiac (straited, involuntary)
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3
Q

What is a Sarcolemma

A

Sarcolemma is cell membrane

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4
Q

What is Sarcoplasm

A

Sarcoplasm is cytoplasm

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5
Q

What is Sarcoplasmic Reticulum

A

Its smooth endoplasmic reticulum

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6
Q

What is Sarcomere?

A

Functional unit within a myofiber

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7
Q

What is the function of skeletal muscle?

A
  • It is controlled by somatic nervous system
  • Forms the muscles of musculoskeletal system and some muscles that do not move bones (diaphragm, extraocullar muscles, muscles of facial expression)
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8
Q

What is a motor unit of skeletal muscle

A
  • A lower motor neuron (motor neuron in a cranial nerve nucleus, or a motor neuron in the ventral horn of the spinal cord) and the muscle fibers it innervates.
  • Each skeletal muscle has many motor units and the ratio of neuron to muscle fibers varies from 1/1 to 1/1000
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9
Q

Nerve supply of skeletal muscle

A
  • is essential for contraction and muscle tone

- Denervation results in flaccid paralysis, areflexia, atonia, and atrophy of the muscle (LMN lesion)

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10
Q

What are skeletal muscles specialized for?

A

for rapid, forceful, voluntary contractions

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11
Q

Connective tissue of skeletal muscle

A
  • Endomysium: delicate connective tissue around individual fibers
  • Perimysium: connective tissue that surrounds a group of fibers called fasicles
  • Epimysium: dense irregular tissue that surrounds the entire muscle

Epi, Peri, Endomysium are continous with the tendons and/or aponeuroses of the muscle

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12
Q

Is skeletal muscle one nucleated or multi?

A

It is multinucleate!

  • Each muscle fiber (myofiber) is a multinucleated cell
  • nuclei are peripherally located
  • myofibrils have actin/myosin (myofilaments)
  • A sarcolemma encloses the myofibrils and nuclei
  • there are periodic invaginations of the sarcolemma called T-tubules
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13
Q

Periodic invaginations of the sarcolemma are called?

A

T-tubules

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14
Q

What else is in the sarcoplasm of the skeletal muscle

A

sarcoplasm contains numerous glycogen granules, myoglobin, and SER

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15
Q

What does SER do?

A

It forms a system of membrane bound tubules that extend throughout the cytoplasm and expands into terminal cisterna next to a T-tubule

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16
Q

What is a triad made up of?

A

the two terminal cisternae and T-tubule arrangement is called a triad- that is located at the junction of A and I bands

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17
Q

What is myofibril made out of?

A

composed of thick myosin and think myosin and thin actin myofilaments

  • light bands (I)
  • thick bands (A)
  • fine dark lines called Z bands in the middle of the I bands
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18
Q

What is the outline region for a sarcomere

A

The region between 2 Z bands is a sarcomere which is the contractile unit in skeletal muscle (functional unit)

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19
Q

What is the I band composed of?

A

-Actin filaments and the Z line marks their attachments

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20
Q

What are the proteins associated with myofilaments?

A

Nebulin and Titin

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21
Q

Proteins associated with myofibrils?

A

Desmin and Plectin

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22
Q

What are the kinds of fibers of skeletal muscle?

A

Red, White, Intermediate

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23
Q

Describe Red fibers of skeletal muscle?

A
  • Small fibers with large amounts of myoglobin (o2 storage molecule)
  • Has many mito (aerobic cells that burn o2 to make ATP-use enzyme succinate dehydrogenase)
  • They are slower and more sustained in contracting (slow twitch motor units which are more resistant to fatigue)
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24
Q

Describe White fibers of skeletal muscle?

A
  • Large fibers with less myoglobin
  • Fewer mito and high levels of glycogen and glycolytic enzymes (highly anaerobic cells whose ATP comes from metabolism of glycogen into glucose)
  • Rapid and sporadic and intense contractions (fast twitch motor units that fatigue rapidly)
25
Q

Intermediate fibers?

A

Exhibit intermediate characteristics b/w red and white fibers

26
Q

Blood supply of skeletal muscle?

A

Has a rich blood supply that is usually derived from at least a couple of arteries

27
Q

Innervation of skeletal muscle?

A

Motor innervation ( derived from LMN in the brainstem)- motor nuclei of cranial nerves and LMN in spinal cord (a-motor and ventral horn cells)

28
Q

Sensory innervation of skeletal muscle?

A

Derived from pseudounipolar neurons in dorsal root ganglia and some cranial nerve ganglia. Their peripheral process connects to muscle spindles and golgi tendon organs

29
Q

Do sensory and motor fibers to a muscle course in one nerve?

A

Yes

30
Q

What cells are involve in repair process of skeletal muscle?

A

Satellite cells within the skeletal muscle proliferate after injury, form myoblasts which fuse to form myotubes that mature into skeletal muscle fibers

31
Q

What does exercise do the size of the muscle?

A

Increase the size of the muscle fiber (hypertrophy) not the number of fibers by increasing the number of myofilaments and myofibrils within a myofiber or by the fusion of satellite cells with an existing myofiber

32
Q

Why does atrophy of muscle happen?

A

Atrophy of skeletal muscle is usually due to a pathological condition or disuse

33
Q

What is hyperplasia?

A

is an increase in the number of muscle fibers and is usually an abnormal condition

34
Q

Where is cardiac muscle located

A
  • located in the heart and at the base of large vessels entering or leaving the heart
  • within the heart it is located in the myocardium
35
Q

What is epicardium?

A

-Epicardium: covers the outside of the heart and is composed of mesothelium (visceral layer of serous pericardium) and underlying connective tissue containing the blood vessels and nerves to the heart

36
Q

What is myocardium?

A

Cardiac muscle held together by connective tissue. The inner portion of the myocardium contains specialized cardiac muscle fibers and purkinje fibers that are part of the impulse conduction system of the heart

37
Q

What is Endocardium?

A

Cover the inner surface of the heart and consists of an endothelium and subendothelial connective tissue

38
Q

Where is cardiac muscle nucleus located?

A

centrally located nuclei

39
Q

What is cardiac muscle syncytium?

A

Ends of fibers branch and meet branches of other fibers giving the appearance of a syncytium (not a syncytium bc of discrete borders but its functions like one)

40
Q

T-tubules and SER in cardiac muscle?

A

T-tubules are larger in cardiac and the SER is not as extensive and there are diads located at the Z line

Fibers accumulate lipofuscin pigment with age

41
Q

Where are intercalated discs located in cardiac muscle?

A

They are located at the ends of adjacent cardiac muscle fibers

42
Q

What is the function of intercalated disc?

A
  • provides points of anchorage for the myofibrils
  • provides for attachment to neighboring cells
  • permit extremely rapid spread of contractile stimulus from one cell to another
43
Q

What are cell junctions of the cardiac muscle?

A
  • Desmosomes
  • Gap junctions
  • Fascia adherens
44
Q

Blood supply of the cardiac muscle?

A

provided by the coronary arteries and their branches

45
Q

Innervation of cardiac muscle?

A

by both the portions of the autonomic nervous system (sympathetic, and parasympathetic)

46
Q

How is cardiac muscle repaired?

A
  • Destroyed cardiac muscle cells are not replaced by new cardiac muscle cells but rather by fibrous connective tissue
  • myocardial infarct is a common cause of cardiac cell death
  • a single large infarct or repeated small infarcts can be fatal
47
Q

Where are smooth muscles located?

A

-located in the wall of GI tract, ducts of glands, respiratory passages, ducts of urinary and genital tracts, walls of arteries, veins, lymphatic vessels, arrector pili muscles, areola of nipples, dartos tunic of scrotum, iris and ciliary body of eye

48
Q

Physical characteristics of Smooth muscle

A

Fusiform shaped cells

-single, central, elongated nucleus with two or more nucleoli

49
Q

In longitudinal section how are the nucleus?

A

Nuclei are staggered

50
Q

In cross section how are the nuclei?

A

Nuclei are only seen in some cells

51
Q

Contractile proteins in smooth muscle?

A

actin, myosin and intermediate filament s

the contractile proteins criss cross the cell attach to dense bodies (adhesion densities containing a-actinin) in the cell membrane and within the cytoplasm

52
Q

Tension transmission by contractions of sm is transmitted where?

A

tension generated by contraction is transmitted through the dense bodies to other cells allowing a group of smooth muscle cells to function as a unit

53
Q

What connective tissue elements do smooth muscle cells secrete?

A
  • Type III and IV collagen
  • Lamina and elastin
  • Proteoglycan (GAGs)
54
Q

What is smooth muscle specialized for?

A

contraction of low force

55
Q

What is smooth muscle influenced by?

A

ANS, hormones, and local metabolites

-peristalsis of the GI tract and enteric NS

56
Q

Blood supply of sm?

A

derived from small arteries in the surrounding connective tissue

57
Q

Innervation of sm?

A

Most sm is innervated by both the parasympathetic and sympathetic portions of the ANS; but some sm is only innervated by only one portion and some contract in response to hormones

58
Q

Repair of SM?

A

-some smooth muscle responds to injury by undergoing mitosis, and in other sm cells are derived from undifferentiated cells in blood vessels, endothelial cells and pericytes

(uterus has regularly replicating populations of smooth muscle cells )

Human SF (2 decks)

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