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Histology > Muscle > Flashcards

Muscle Flashcards

1
Q

what is wrong with the statement “one muscle cell”

A

Technicall a muscle cell is made up of many different types of cells:
-its got connective tissue! = collagen (produced by fibroblast) + fiber + adipocytes + WBC (active in the connective tissue)

muscle fiber = many muscle cells fused together
muscle tissue = excitable tissue

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2
Q

What is the difference in the arrangement of smooth muscle and skeletal muscle?

A

skeletal muscle = fiber parallel

smooth muscle = layers (each with different orientation)

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3
Q

striated muscle

A
  • skeletal
  • visceral striated (gut)
  • cardiac

Repeating sarcomeres – dark band / light band / dark band / light band

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4
Q

smooth muscle

A

vessels, organs, glands
viscera

– collections of cells (not fibers anymore)
– spindle shape
– long thin projections off each side

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5
Q

How are muscle fibers formed?

A

aggregations of myoblasts (fusing)

myo = muslce
blast = forming
*myoblast = muscle forming
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6
Q

A muscle fiber is a functional syncytium because it contains gap junctions

A

THIS is FALSE.
A muslce is a syncytium because it is MULTI-NUCLEATED
note: the nuclei are located peripherally in the cell (NOT CENTRAL)

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7
Q

Does a muscle fiber always extend the length of the muscle?

A

NO. not always

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8
Q

Tendons are what kind of connective tissue?

A

Dense regular connective tissue

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9
Q

what are the connective tissue components of skeletal muscle

A
  1. tendons

2. different coverings

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10
Q

epimysium

A
  • surrounds the collection of fascicles that make up the muscle
  • major structures will penetrate this layer
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11
Q

perimysium

A

-surrounds groups of muscle fibers to form fascicles

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12
Q

endomysium

A

delicate layer that surrounds individual muscle fibers

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13
Q

Where are nerves and blood vessels in the muscle?

A
  • traveling in between the connective tissue layers (epimysium, perimysium, endomysium)
  • there to supply the muscle fascicles and fibers
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14
Q

What is the purpose of a T-tubule?

A

-allows depolarization to quickly penetrate the membrane (speeds flow of ions to the sarcoplasmic reticulum - releases Calcium)

it’s an invagination of the plasma membrane (sarcolemma)

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15
Q

all skeletal muscle fibers are the same

A

NOPE.

  • there are white fibers, red fibers, and intermediate fibers
  • they have different amounts of myoglobin and mitochondria
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16
Q

red fibers

A

Type 1, slow twitch, aerobic

  • small
  • extensive blood supply
  • many mitochondria and myoglobin
  • a lot of succinate dehydrogenase and ATPase
  • marathon runner
17
Q

white fibers

most muscles are a mix of red and white

A

Type II (and IIb), fast twitch, anaerobic

  • larger fibers
  • extensive sarcoplasmic reticulum
  • lots of glycogen and glycolytic enzymes for rapid energy
  • weight lifting
18
Q

what the heck is a myofibril?

A
  • it’s the contractile unit of muscle fibers
  • one muscle fiber contains numerous arrangements of myofibrils
  • myofibrils are surrounded by the sarcoplasmic reticulum
  • myofibril = bundles of myofilaments (stacks of sarcomeres)
  • myofilaments = polymers of actin and myosin
19
Q 
A band
I band
M line
Z line
H zone
A

A band - dark (because its dense, light wont on microscope)
I band - light, Z line runs down the middle
M line - down the middle of A band (myosin scaffolding)
Z line - anchor point (actin) - defines the length of a sarcomere (z line to zline )
H zone

20
Q

What is sarcoplasmic reticulum?

A
  • modified smooth ER
  • arranged around myofibers (muscle fibers)
  • reservoir for Calcium (release and uptake!)
21
Q

motor end plate

A

where the efferent nerve fiber contacts the skeletal muscle fibers
note: sarcoplasmic reticulum is close to the motor end plate - this makes sense (influx of Ca needed for vesicle release)

22
Q

motor unit

A

motor unit = neuron + myofiber it loves

23
Q

what might you see when there is an infection or something wrong in the muscle?

A

could see:

  • WBCs (if there is an infection)
  • antibodies (attacking muscle by mistake in autoimmune disease)

-muscle atrophy - a smaller fascicle
result of loss of innervation/blood supply) - from being stabbed! mother fuckers! or in ALS motor neurons die, muscle shrivels up

24
Q

why is the muscle spindle important

A
  • they receive motor and sensory information
  • coordinate smooth muscle movement
  • muscle stretch stimulates mechanoreceptors, which activates sensory fibers
25
Q

what do muscle spindle fibers look like

A
  • they are kind of sickly looking compared to bulky muscle fibers
  • dont confuse them with nerve fibers (muscle spindle is smaller more sickly looking
26
Q

golgi tendon organ

A

senses changes in muscle tension

its a sensory receptor organ

27
Q

can muscle regenerate

A

fibroblasts can repair skeletal muscle some

satellite cells serve as a reserve of embryonic myoblasts

28
Q

cardiac vs. skeletal muscle

A
  • fewer nuclei (and centrally located!)
  • intercalated discs (sites of attachment of neighbor cells)
  • mono-nucleated
  • both are striated
29
Q

where is cardiac muscle found

A

heart and BASE of LARGE Veins that enter the heart

30
Q

intercalated discs

A

-Maculae adherentes/desmosomes:
holds the cells together

-Fasciae adherentes:
adherens, transverse component, hold the cells together, thin filaments anchor here

-Gap junctions:
provide ionic continuity between adjacent myocytes, part of the lateral component

31
Q

Sarcoplasmic reticulum and T-tubule system in cardiac muscle

A
  • not as well organized as skeletal
  • only one T-tubule per sarcomere
  • DIAD: 1 T-tubule + 1 SR
32
Q

can cardiac muscle regenerate

A

no repair

dead cells are replaced by scar tissue

33
Q

where is smooth muscle in the body?

A 
found lining the:
GI tract
UG tract 
respiratory tract
blood vessels 
iris and ciliary body of the eye
dartos muscle (scrotum)
erector pili
34
Q

smooth vs. cardiac/skeletal

A
  • nuclei are central (corkscrew appearance)
  • anchored in ECM (collagen, laminin, elastin), which smooth muscle cells secrete, along with (basal lamina)

some have an endocrine function
-Juxtaglomerular cells (sec. renin)

35
Q

can smooth muscle cells undergo mitosis?

A

YES. in the uterus

36
Q

smooth muscle contraction?

A

*contractions are slower, can last much longer and are more energy efficient (up to 1 second)

  • long, sustained contractions
  • peristaltic contractions
  • under the control of the ANS
  • hormonal control – control by the endocrine system
  • nerve terminals are small (compared to the motor end plate)
37
Q

smooth muscle differences

A
  • no T-tubule system
  • sarcoplasmic reticulum sequesters Ca++
  • gap junctions connect cells!
38
Q

smooth muscle contraction (more details)

probably dont need these detail but who knows

A

(probably dont need these detail but who knows)

  • contraction is initiated by a rise in cytosolic Ca++
  • Ca++ causes myosin light chain kinase to phosphorylate myosin  can then interact with actin (dephosphorylation stops contraction)

Histology (1 decks)

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