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COT - Exam 1 > 6.3 - Lecture - Muscle > Flashcards

6.3 - Lecture - Muscle Flashcards

This is the syllabus lecture 6.3 as well as all of the notes from the slides (because one set of slides for both lectures)

1
Q

Caveolae

A
  • endocytoic vesicles in smooth muscle that shuttle calcium
  • Are present in all types of muscle
  • responsible for bringing calcium for sequestering in the SR until an electrical impulse is received
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2
Q

Sarcoplasmic reticulum (SR)

A
  • fancy name for endoplasmic reticulum
    = a modified ER in muscle
  • ends in tubular structures = called terminal cisterns
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3
Q

Transverse tubules

A
  • in cardiac (and skeletal) muscle
    = tubular extensions of the cell membrane
  • permeate into the cell creating an extracellular space adjacent to the membrane of the SR (adjacent to the terminal cisterns)
  • called t-tubulues
  • contain DHP receptors = voltage gated calcium channels
    DHPRs interact with ryanodine receptors on SR
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4
Q

Terminal Cisterns

A
  • tubular structures formed at the ends of the SR
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5
Q

Dyad

A
  • in cadiac muscle
  • formed by one t-tubule and one terminal cistern
  • recognizable in EM
  • specialized structure to increase the speed that electrical impulses can act on SR during contraction
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6
Q

Triad

A
  • in skeletal muscle
  • t-tubules weave along the region of actin-myosin overlap in the sarcomere just outside the myofibrils (not the same in cardiac)
  • formed by two terminal cisterns surrounding either side of a transverse tubule
  • even greater efficiency than in cardiac muscle
  • specialized to increase the speed that electrical impulses can act on SR to cause contraction
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7
Q

Myosin

A

thick filament

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8
Q

Actin

A
  • thin filament

- bound to sarcoskeleton

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9
Q

Dense bodes (dense plaques)

A
  • in smooth muscle only
  • bound to actin
  • can be located intracellularly or bound to the sarcolemma
  • also bind to intermediate filaments:
    Desmin in visceral muscle and vimentin in vascular muscle
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10
Q

Desmin

A
  • intermediate filaments that connect to dense bodies (plaques) in smooth muscle
  • in skeletal muscle desmin connects the Z-lines of myofibrils with each other
  • also connects to lateral sarcolemma via a complex of proteins (costamere)
  • intermediate filaments have little importance in cardiac muscle? (says the syllabus)
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11
Q

Vimentin

A
  • an intermediate filament in vascular muscle

- binds dense bodies (plaques)

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12
Q

Costamere

A

= complex of proteins (including dystrophin) that connect desmin to the lateral sarcolemma

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13
Q

Dystrophin

A
  • part of the complex of proteins that makes up a costamere and connects intermediate filaments (desmin) to the lateral sarcolemma
  • is lacking in muscular dystrophy
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14
Q

Skeletal muscle fibers are formed from….

A

syncytial embryonic myocytes - that come from a myoblast progenitor

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15
Q

Myoblast

A

the myocyte progenitor that will form the embryonic myocytes that form a syncytium to make a skeletal muscle fiber

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16
Q

Myosatellite cells

A
  • some undifferentiated progenitor cells that remain intact in adult muscle
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17
Q

Myotubes

A
  • formed from myocytes
  • initially contain central nuclei and few peripheral myofibrils
  • eventually grow into the myofibers of adult skeletal muscle
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18
Q

Describe the possible changes of an adult myofiber

A
  • cannot increase in number

- may change in size (diameter) by addition or subtraction of myofibrils

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19
Q

Discuss ideal conditions for muscle regeneration and injury

A

Much like in axons of peripheral nerves:

  • surrounding external membrane is intact (equivalent in structure and function the external membrane o nervous tissue and basement membrane of epithelia)
  • myosatellite cells are present within
  • supporting endoneurium is still in place
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20
Q

2 Types of Smooth Muscle

A

Unitary

Multiunit

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21
Q

2 Special types of cardiac muscle

A

Purkinje fibers

cardiac endocrine cells

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22
Q

3 Types of skeletal muscle

A

Type I = red
Type IIa = intermediate
Type IIb = white

23
Q

General Features of smooth muscle

A
  • reticular layer
  • intermediate filaments
  • dense bodies
  • caveolae
  • SR
24
Q

Innervation of Smooth muscle

A
  • by the ANS through second neuron in chain
  • Epinephrine - if stimulated by Sympathetic Divison
  • Ach - if stimulated by Parasympathetic division
25
Q

Describe features of Myogenic Regulation of Contraction

A

= Single unit, visceral

  • one axon –> many cells
  • MANY gap junctions
  • coordinated action
  • responsive to hormones, etc.
  • low ratio of nerve fibers to muscle cells
26
Q

Describe features of Neurogenic Regulation of contraction

A

= multi-unit

  • one axon –> few cells
  • independent action
  • found in iris, arrectar pili, large vessels, small airways of lungs
  • high ratio of nerve fibers to muscle cells
27
Q

Regulation of calcium in smooth muscle

A
  • mainly through caveolae
28
Q

Describe the general features of cardiac muscle

A
  • T-tubules
  • centralized nucleus
  • sarcoplasmic reticulum
  • dyads (at the z-line)
  • intercalated disc
  • fascia adherens
  • GAP junctions
29
Q

Fascia Adherens

A
  • parallels zonular adherens of epithelial cells

- connects actin of 1 cell to neighboring actin of other cell

30
Q

Describe the morphology of cardiac muscle

A
  • cardiac myocytes (may be branched?)
  • fiber size ~100 micrometeres long and 10-15 diameter
  • one (sometimes 2) centralized nuclei per cell
  • striated –> striateiion are more delicate than in skeletal muscle fibers
  • many mitochondria and few myofibrils
  • sarcoplasmic cone
  • intercalated disc
31
Q

Describe the intercalated disc

A

= distinct band-oriented perpindicular to the cell long axis
= complex of 3 intercellular JXNs:
1) Fascia adherens (connects to actin in terminal sarcomere)
2) GAP JXN
3) Desmosome

32
Q

What are the two cardiac myocyte subtypes

A

1) Myocardial endocrine cell

2) Cardiac Conducting cell

33
Q

Describe the myocardial endocrine cell

A
  • mostly located in atria of heart
  • cells have granules filled with atrial natriuretic peptide (ANP) which is released in response to stretch of atrial wall
34
Q

What is ANP, where does it come from, what is its FXN

A

= atrial natriuretic peptide

  • enclosed in granules of the myocardial endocrine cell
  • is released in response to stretch of atrial walls
  • promotes loss of sodium, potassium and water in kidneys –> decreases the body fluids to decrease blood pressure
35
Q

What is a cardiac conducting cell

A
  • cardiac myocyte modified for conducting electrical activity (increased size, # GAP JXNs, [glycogen] + decreased myofibrils)
    = purkinje cell
36
Q

What are the characteristic modifications to a cardiac myocyte that cause it to become a cardiac conducting cell

A
  • increased size of cell
  • incerased number of gap junctions
  • increased glycogen content
  • fewer myofibrils (because space is occupied by glycogen)
37
Q

What is the conduction path of a cardiac conducting cell

A

1) SA node
2) AV node
3) Bundle of His
4) Purkinje Fibers
5) Ventricular fibers

38
Q

What are the general features of skeletal muscle

A
  • t-tubules
  • myofibrils
  • sarcomeres
  • actin/myosin
  • SR
  • Triads ( at A-I interface)
  • mitochondria
  • peripheral nucleus
39
Q

Describe Red/ Type I skeletal muscle and its characteristic staining

A
  • slow-twitch
  • oxidative
  • capable of repeated contraction without fatigue
    Staining:
  • least glycogen/PAS stain
  • most mitochondrial activity (most cyto c oxidase staining)
40
Q

Describe intermediate/ Type IIa skeletal muscle

A
  • fast-twitch
  • glycolytic-oxidative
  • fatigue resistant
41
Q

Describe White/ Type IIb skeletal muscle and its characteristic staining

A
  • fast-twitch
  • glycolytic
  • strong + fast contraction
  • fatigues easily
    Staining:
  • most glycogen/PAS stain
  • least mitochondrial activity (least cyto C oxidase staining)
42
Q

Describe Skeletal muscle fiber developement

A

1) Skeletal muscle fiber myoblasts
2) primary myotubes form from the fusion of myoblasts
3) secondary myotubes from with the external membrane of primary myotubes + subsequently separate to from additional fibers of equivalent adult morphology
4) myoblast (some) persist beneath (within) the external membrane of adult fibers as satellite cells (not full stem cells- have limited regenerative abilities)

43
Q

Describe general characteristics of Satellite cells and which muscle types if any will they not be present in

A

= muscle stem cells

  • population of undifferentiated quiescent precursors that become activated to divide and differentiate in response to demands of growth + damage
  • multipotential
  • not present in cardiac muscle
44
Q

describe the Function of satellite cells

A

= monitor the interface between muscle fiber and CT along the external membrane

  • monitor the integrity of skeletal muscle fibers + clean up and repair these areas
  • if external membane breaks - it is much harder for them to repair muscle tissue
45
Q

Describe the neuronal regulation by afferent fibers

A
  • muscle spindle = afferent fiber in parallel with the body of muscle (each comprising by itself a small fascicle) - positioned for supplying information on length of muscle
  • golgi tendon organ - afferent fiber in series with muscle and tendon (between them) - positioned for supplying info of force being exerted by muscle
46
Q

Describe the function and location of muscle spindle

A
  • Afferent neuronal regulation in skeletal muscle
  • sits in parallel with the muscle
  • positioned for supplying information on length of muscle
47
Q

Describe the function and location of the golgi tendon order

A
  • afferent neuronal regulation in skeletal muscle
  • sits in series between the muscle and tendon
  • positioned for supplying information on the force being exerted by the muscle
48
Q

Describe the morphology of the muscle spindle

A
  • similar to the Golgi tendon organ
  • contains bad and chain fibers = each is sensitive to different ranges of stretch
  • receives efferent (gamma motor neurons) and generates afferent ( type Ia and II sensory) innervation
  • surrounded by a capsule that is equivalent to perimysium
49
Q

Describe the two broad functions of muscle spindle

A

1) Proprioceptive inputs to the nervous system

2) prevent over stretch of muscle

50
Q

What does desmin do

A
  • connects myofibrils with each other at z-line (holds them in register)
  • important for transmission of force to body of muscle
51
Q

What are costameres and what are their function

A

= Collection of intracellular protein binding desmin to sarcolemma at the z-line

  • a protein complex that connects intermediate filaments that exist throughout the z-line of the sarcomere with the cell membrane
  • mutation in costamere-associated protein dystrophin - has been implicated in muscular dystrophy
52
Q

Describe the transmission of force to the tendon

A
  • at the Myotendinous JXN - actin filaments are directly anchored to cell membrane in a similar structure to the fascia adherents
  • the anchoring region is largely parallel to direction of force
53
Q

Describe the External membrane of muscle: what it surrounds, its composition, and function in regards to repair

A
  • surrounds skeletal muscle fibers, cardiac muscle cells, smooth muscle cells
  • is analogous in structure + composition to basement membrane of epithelia
  • can serve as scaffolding for the repair of damaged muscle fibers
54
Q

Discuss the possibility of muscle repair as it relates to muscle fibers

A

1) a broken muscle fiber with an external membrane –> can be repaired
2) a broke muscle fiber with a broken external membrane –> cannot be repaired

COT - Exam 1 (26 decks)

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