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First Semester: Microscopic Anatomy > Lecture 12-13: Muscle > Flashcards

Lecture 12-13: Muscle Flashcards

1
Q

Four basic tissues of the body

A
  • Epithelium
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
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2
Q

Muscle cells

A

specialized cells capable of contraction to produce movement needed for locomotion, propulsion, and pressure regulation

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3
Q

Muscle cells are also known as

A

myocytes and myofibers

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4
Q

Muscle cells are ____-shaped and originate from

A
  • Spindle

- The mesoderm

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5
Q

Mesenchymal cells (myoblasts) align and fuse together forming multinucleated tubes called

A

myotubes

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6
Q

Myotubes differentiate, forming

A

Functional myofilaments

The nuclei are displaced against the plasma membrane

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7
Q

Satellite cells

A

Cells that don’t differentiate and remain as mesenchymal cells.
Function in muscle repair

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8
Q

Sarcoplasm

A
  • The cytoplasm of muscle cells

- Contains glycogen and myoglobin

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9
Q

Sarcolemma

A

Plasma membrane of the muscle cells

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10
Q

Sarcoplasmic reticulum

A

Highly specialized smooth er of a muscle cell that regulates calcium flow

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11
Q

Skeletal muscle make up ___% of body weight

A

50

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12
Q

Skeletal muscle nuclei

A

Multiple, peripherally located nuclei

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13
Q

Striations in skeletal muscle are seen in myocytes when cut in

A

longitudinal section

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14
Q

Epimysium

A

Muscles are surrounded by this dense irregular connective tissue layer

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15
Q

A whole muscle is made up of many smaller bundles known as _____ surrounded by _______

A

fascicles

perimysium

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16
Q

Myofibers contain cylindrical bundles of ______ which in turn contain many smaller bundles of _________

A

myofibrils

myofilaments

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17
Q

Individual myocytes are surrounded by reticular fibers which form

A

the endomysium

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18
Q

Two myofilaments

A

myosin and actin

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19
Q

What are the contractile elements of muscles

A

myofibrils

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20
Q

What cause the striated appearance of skeletal and cardiac muscles

A

myofibrils

A band and I band

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21
Q

Functional unit of myocyte

A

sarcomere

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22
Q

At full contraction the Z lines

A

will be drawn closer to each other

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23
Q

A band

A

actin and myosin

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24
Q

I band

A

actin filaments

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25
Q

A band on a stain

A
  • Dark
  • Corresponds to the area where the thick and thin filaments overlap
  • Composed of myosin and actin
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26
Q

I band on a stain

A
  • Pale

- Composed only of thin actin filaments

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27
Q

Each I band is bisected by

A
  • A protein disc known as the Z line

- Actin filaments are anchored into the Z line

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28
Q

Motion mediated by muscle cells is based on

A

The conversion of chemical energy (ATP) into mechanical energy by the contractile apparatus of muscle cells

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29
Q

During muscle contraction, actin filaments

A

slide over the myosin filaments which results in a shortening of the I band

30
Q

Actin and myosin are held in position by

A

The myofibril by other proteins (desmin, tropomyosin, troponin)

31
Q

Sliding filament model

A
  1. Each sarcomere shortens
  2. Myofilament length is constant
  3. I band shortens, almost disappears
  4. Thin filaments slide past thick filaments
  5. Summation of all sarcomere shortening produces contraction of the muscle cell
32
Q

5 steps of muscle contraction

A
  1. Bidning of Calcium to Troponin C
  2. Conformational change in tropomyosin, exposing the myosin-binding site on actin
  3. Myoisin head binds to actin; ATP->ADP moving myosin head
  4. Bound thin filaments slide over thick filaments
  5. Shortening of entire muscle fiber
33
Q

T-tubule

A

A deep invagination of the sarcolemma only found in skeletal and cardiac muscle.
Allow depolarization of the membrane to quickly penetrate to the interior of the cell allowing Ca release from the SR

34
Q

Sarcoplasmic reticulum

A
  • Equivalent to the ER but seen in smooth and striated muscle
  • Stores and releases Ca ions to initiate contractions
35
Q

Terminal cisternae

A

Expanded ends of the SR

36
Q

Type I muscle

A

Slow oxidative

37
Q

Type 2

A

Fast glycolytic

38
Q

Cardiomyocyte

A

Single cross-striated cell with one central nuclei.

  • Has intercalated discs (gap junctions, desmosomes)
  • Has sarcoplasmic reticulum and many mitochondria
39
Q

Intercalated discs function as a ________ and

A

Syncytium

Attach cardiac muscle cells together, providing strength and ability to function

40
Q

A true syncytium

A

A multinucleated cell

E.g. Skeletal muscle cell

41
Q

Two elements of intercalated discs

A
  1. Transverse element

2. Longitudinal element

42
Q

Transverse element of intercalated disc

A
  • Anchor
  • Desmosome - fascia adherens and/or macula adherens
  • Serve as strong attachment
43
Q

Longitudinal element of intercalated disc

A
  • Communication
  • Gap junction (nexus) with ion channels
  • Propagate electric impulse
44
Q

Atrial muscle cells contain

A

membrane bound granules

45
Q

Where are atrial granules especially numerous?

A

Right atrium

46
Q

Atrial granules have an endocrine function due to the presence of

A

Atrial Natriuretic Factor (ANF)
also known as
Atrial Natriuretic Peptide (ANP)

47
Q

Two types of cardiac myocytes

A
  • Contractile (red)

- Conductile (pale pink)

48
Q

___ ____ ____ ____ form the cardiac nodes and fibers involved in impulse conduction

A

Modified cardiac muscle cells

49
Q

Purkinje fibers

A
  • Modified cardiac muscle cells with 1 or 2 nuclei, myofibrils ar sparse and restricted to periphery of cells
  • Arranged in groups, cels arebiggere and paler than contractile cardiac muscle cells
50
Q

Smooth muscle cell nucleus

A

Single centrally located

51
Q

Are actin and myosin present in smooth muscle

A

Yes, but not ordered

52
Q

In smooth muscle cells, cytoplasmic dense bodies

A

Anchors for myofilaments, like Z bodies

53
Q

Do smooth muscle cells have desmosomes and gap junctions

A

yes

54
Q

Smooth muscle Ttubules and SR

A

No T-tubules

SR is poorly developed

55
Q

Smooth muscle shape

A

Spindle (fusiform)

Surrounded by basal lamina and reticular fibers

56
Q

Single (unitary smooth muscle)

A
  • Found in visceral organs
  • Cells behave like syncytium contracting in a network
  • Sparse nerve innervation but cell communicate via multiple gap junctions
57
Q

Multi-unit smooth muscle

A
  • In iris of eye
  • Precise contraction
  • Individual innervations of each myocyte
  • Lack of gap junctions, function individually
58
Q

4 functions of smooth muscle cells

A
  • Peristalsis: Wave-like contractions (ex. gastrointestinal tract)
  • Vascular dynamics: contraction alters blood flow and important in blood pressure
  • Propulsion: urinary bladder, uterus
  • Secretion
59
Q

Contracted appearance of smooth muscle cells

A
  • Oblique arrangement of actin/myosin filaments and the intermediate filament arrangement allow the entire cell to shorten up to 80%.
  • Corkscrew appearance of nucleus
60
Q

Innervation of smooth muscle

A
  • Innervated by ANS
  • Allows stimulation and inhibition of muscle cells
  • Acetylcholine, norepinephrine, epinephrine are common neurotransmitters
61
Q

Non-muscle cells

A

myoepithelial cells

62
Q

Myoepithelial cells have what origin

A

Ectodermal

63
Q

Do myoepithelial cells contain actin/myosin

A

yes

64
Q

Can myoepithelial cells be stimulated by hormones?

A

Yes

65
Q

Myoepithelial cells are also called

A

Basket cells (basket shape)

66
Q

Where are basket cells located?

A

Salivary/mammary/lacrimal glands

67
Q

Satellite cells

A
  • Positioned between basal lamina and sarcolemma of muscle cell
  • These cells retain mitotic potential and thus can accomplish some repair
  • Fibroblasts also form connective tissue (scar) as a part of the repair process
68
Q

Can cardiac muscle cells regenerate?

A

Nope

69
Q

In addition to mitotic activity, new smooth muscle cells may be derived from

A

pericapillary mesenchymal ccells

70
Q

All types of muscle repaid is completed by

A

Scar tissue formation

First Semester: Microscopic Anatomy (23 decks)

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