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ANP 1105 > Chapter 9 - Muscles and Muscle Tissue > Flashcards

Chapter 9 - Muscles and Muscle Tissue Flashcards

1
Q

What are the 3 types of tissues?

A

Skeletal, smooth, cardiac

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2
Q

Describe skeletal muscles (5).

A

skeletal muscle: organs that attach bones and skin
- fibers: longest and have striations (stripes)
- called voluntary muscle since can be controlled
- contract rapidly and get tired easily
-Key words: striations, voluntary, skeletal

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3
Q

Describe cardiac muscle (3).

A
  • makes up most of heart wall
  • contracts at steady rate because it is a pacemaker but heart increases rate
  • Key words: cardiac, striated, involuntary
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4
Q

Describe Smooth Muscle.

A
  • tissue: found in walls of hollow organs ex. stomach, bladder and airways
  • Key words: visceral, nonstriated and involuntary
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5
Q

What are the 4 main characteristic all muscles share?

A

Excitability (responsiveness): ability to receive and respond to stimuli
Contractility: ability to shorten forcibly when stimulated
Extensibility: ability to be stretched
Elasticity: ability to recoil to resting length

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6
Q

What are the 4 functions of muscles?

A
  • produce movement: responsible for all locomotion and manipulation ex. walking, digestion, pumping blood
  • maintaining posture and body position
  • stabilizing joints
  • generate heat as they contract
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7
Q

What are the 2 types of attachments for muscles?

A

direct (fleshy) attachments: epimysium fused to periosteum of bone or perichondrium of cartilage

indirect attachments: connective tissue, epinysium, perimysium and endomysiumform complex at endof muscle

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8
Q

What are the things that make up skeletal muscle (4).

A
  • nerves and blood supply
  • connective tissue sheaths
  • attachments
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9
Q

What does each muscle receive?

A
  • nerve
  • artery
  • veins
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10
Q

What does consciously controlled skeletal muscles have?

A

They have nerves supplying every fiber.

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11
Q

What do contracting muscle fibers need and produce?

A

Need: large amounts of oxygen and nutrients
Produce: waste products

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11
Q

What are muscles fibers covered with and what does it support?

A

connective tissue (endomysium)
- supports cells and reinforces whole muscle

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12
Q

What is the difference between the sarcolemma and the sarcoplasm?

A

SL - muscle fiber plasma membrane
SP - muscle fiber cytoplasm
- Contains many glycosomes for glycogen storage, as well as myoglobin for oxygen storage

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12
Q

What are the different levels of the sheaths from external to internal?

A

Epimysium: dense irregular connective tissue surrounding entire muscle; may blend with fascia
Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)
Endomysium: fine areolar connective tissue surrounding each muscle fiber

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12
Q

What are the structures within skeletal muscle cells?

A
  • Myofibrils
  • sarcoplasmic reticulum
  • t tubules
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13
Q

What is a myofibril and how much of the muscle volume does it take up?

A

dense packed and rodlike elements
- a single muscle fiber contains 1000s
- 80%

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14
Q

What characteristics do myofibrils contain?

A
  • striations
  • sarcomeres
  • myofilaments
  • molecular composition of myofilaments (actin and myosin)
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15
Q

What is the difference between the A Band and the I band?

A

AB: dark region
- H zone: lighter region in middle of A band
- M line: line of protein (myomesin) that
bisects (divides in 2 lines) H zone
vertically
IB: lighter region
- Z disc (line): coin-shaped sheet of proteins on midline of light I band

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16
Q

Describe Sarcomeres.

A
  • smallest contractile unit (functional unit) of muscle fiber
  • contains A band with half of an I band at each end
    - consists of area between Z discs
  • individual sarcomeres algin end to end along myofibril, like boxcars of train
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17
Q

What is a myofilament?

A

arrangement of actin and myosin
- actin: thin filament - extend across I band and partway in A band, anchored to Z disc
- myosin microfil: think filament - extends length of A band, connected to M line

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18
Q

Explain the composition of myosin.

A

contains two heavy and four light polypeptide chains
- heavy: intertwine to form myosin tail
- light: form globular head
- head links to thin filament to form cross bridging
- 2 heads are off set

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19
Q

What is the molecular composition of myofilaments (3 [5])?

A

Elastic fibers: made of protein titin
- holds thick filament in place; helps with recoil, resist over stretching

Dystrophin
- links thin filament to sarcolemma

Nebulin, myomesin and C protein: bind filament or sarcomeres together
- maintain alignment of sarcomere

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20
Q

Explain the composition of actin and their regulatory proteins.

A

polypeptide made of kidney shaped G-actin (globular) subunits
- G actin bears active sites for myosin head to attach during contractions
- G actin link together to form F actin (filamentous)

RP: tropomyosin and troponin

21
Q

Explain the role of Sarcoplasmic reticulum.

A

SR: network of smooth endoplasmic reticulum tubules surrounding each myofibril
- run longitudinally
- terminal cisterns form perpendicular cross channels at the A-I band junction
- SR functions in regulation of intracellular Ca2+ levels
- stores and releases Ca2+

21
Q

Explain the function of T tubules (6).

A

Formed by protrusion of sarcolemma deep into cell interior
- Increase muscle fiber’s surface area
- Lumen continuous with extracellular space
- Allow electrical transmissions to reach interior of each muscle fiber
- Tubules penetrate cell’s interior at each A–I band junction between terminal cisterns

Triad: area formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere

22
Q

What are the triad relationship (5)?

A

T tubule contains integral membrane proteins into intermembrane space (between tubule and muscle fiber sarcolemma)
- T proteins act as voltage sensors that change shape

S R cistern membranes also have integral membrane proteins that protrude into intermembrane space
- S R integral proteins control opening of calcium channels in S R cisterns
- with impulses, T tubule proteins change shape, causing S R proteins to change shape, causing release of calcium into cytoplasm

23
Q

Explain contractions in relation to muscle fibers (3).

A

activation of cross bridges to generate force
- occurs when forces exceeds forces opposing shortening
Sliding filament model of contraction: thin filaments slide past thick filaments (actin and myosin overlap) - don’t change shape

24
Q

Which structures are involved in shortening of muscle fibers?

A
  • I band shorten
  • Z disc become closer
  • H zones disappear
  • A bands move closer to each other
25
Q

Explain the location and function of axons in skeletal muscles.

A

stimulated by somatic motor neurons
- axons travel from CNS to skeletal muscle
- divides into branches to form neuromuscular junctions and motor end plate

26
Q

How does AP cross from neuron to muscle cell?

A

Acetylcholine

27
Q

Explain neuromuscular junction.

A
  • motor neuron contacts the skeletal muscle
  • consists of multiple axon terminal and the underlaying junctions folds of the sarcolemma
28
Q

Explain end-plate potential.

A
  • ACh released from motor neuron binds to ACh receptors on sarcolemma
  • cause chemically gated ion channels (ligands) on sarcolemma to open
  • Na+ diffuses in, interior of sarcolemma becomes less negative
29
Q

What are the 3 steps of AP for skeletal muscles ?

A
  • Generation of end plate potential
  • Depolarization
  • Repolarization
30
Q

Explain depolarization.

A
  • if end plate potential causes enough change, voltage-gated
  • Na+ channels open
  • AP spreads across sarcolemma from one voltage gated Na+ channel to the next
31
Q

Explain repolarization.

A

Na+ voltage-gated channels close, and voltage-gated K+ channels open
K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
- refractory period: muscle fiber cannot be stimulated for a specific time, until repolarization is complete

32
Q

What is special about AP in muscle fibers?

A

They don’t have a hyperpolarization period

33
Q

Explain Excitation-contraction (E-C) coupling.

A

events that transmit AP along sarcolemma (excitation) are coupled to sliding of myofilaments (contraction)
- AP propagated into T tubules where it stimulates the release of Ca2+ from SR

34
Q

What are the 4 steps of the cross bridge cycle?

A

1)Formation of cross bridging
2) the power stroke fueled by ADP and Pi
3) cross bridging detachments
4) returns back to pre stroke formation

35
Q

explain what a muscle twitch is.

A

simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron

36
Q

What are the three phases of muscle twitch?

A

Latent: events of excitation-contraction coupling
- no muscle tension seen
Contractions: cross bride formation
- tension increase
Relaxation: Ca2+ reentry into SR
- tension declines

37
Q

What are the 3 ways responses are graded by?

A
  • changing frequency of stimulation
  • changing strength of stimulation
  • muscle response to change in stimulus frequency
    - single stimulus results in single
    contractile response
38
Q

Draw and describe the 4 types of temporal summation.

A
  • individual twitches
  • temporal summation
  • unfused tetanus
  • fused tetanus
39
Q

What is recruitments?

A

stimulus is sent to more muscle fibers, leading to more precise control

40
Q

What are the 3 types of stimulus involved in recruitment?

A

Subthreshold: stimulus not strong enough, so no contractions seen
Threshold: stimulus is strong enough to cause first observable contraction
Maximal: strongest stimulus that increases maximum contractile force
- all motor units have been recruited

40
Q

How does size effect recruitment?

A
  • smaller fibers are recruited first then larger fibers (only for powerful contractions)
  • some contract while others don’t to fight against fatigue
41
Q

What are the 2 types of contractions and explain?

A

Isometric: no shortening; muscle tension increases but does not exceed load
Isotonic: muscle shortens because muscle tension exceeds load
- concentric contractions: muscle shortens and does work
- eccentric: muscle lengthens and generates force

42
Q

What are the three mechanisms for regenerating ATP?

A
  • direct phosphorylation of ADP by creatine phosphate (CP)
  • anaerobic - glycolysis and lactate formation
  • aerobic - glycolysis and aerobic respiration in mitochondria
43
Q

What is the difference between short distance and prolonged duration exercise when it comes to ATP generation.

A

SD - uses ATP stored in muscles then ATP generated by creatine and ADP then glycogen

LD- generates ATP from other nutrients by aerobic pathway

44
Q

Explain Muscle fatigue.

A

the inability to contract despite stimulation
causes:
Ionic imbalances
K, Na and Ca levels can change membrane potentials
- increased Pi from CP and ATP interfere with calcium release in SR
- decreased levels ATP means increased levels Mg which interferes with voltage sensitive T tubules
- decreased glycogen

45
Q

What are the 4 things the force of muscle contractions depend on?

A

1) frequency of stimulation
2) number of muscle fibers stimulated (recruitment)
3) size of muscle fibers
4) degree of muscle stretch: if stretched to various lengths and maximally stimulated, the tension generated varies

46
Q

Which stretch length percentage is optimal?

A

80% to 120%

47
Q

How fast and long muscle fibers contract for is determined by …

A
  • muscle fiber type
  • load and recruitment
48
Q

What are the muscle fiber characteristic for contractions?

A

speed: speed which myosin ATPases splits ATP - electrical activity of motor neurons
metabolic pathway for ATP synthsis
- oxidative fibers: use aerobic pathways
- glycolytic fibers: use anaerobic glycolysis

49
Q

What are the 3 fibers types for contractile speed?

A

slow oxidative fibers: low-intensity, endurance activities
fast oxidative fibers: medium-intensity activates
fast glycolic fibers: short-term intense or powerful movements

50
Q

What are the 2 layers of smooth tissue?

A

Longitudinal layer: fibers run parallel to long axis of organ
- contraction causes organ to shorten - more space
circular layer: fibers run around circumference of organ
- contraction causes less space

51
Q

5 Characteristics of smooth muscles.

A
  • are spindle-shaped
  • have only 1 nucleus
  • lack the coarse connective tissue sheaths found in skeletal muscles (only have endomysium)
  • has varicosities (bulbous swellings) instead of neuromuscular junctions
  • less elaborate SR and no T tubules
52
Q

What is different between skeletal and smooth muscle when it comes to excitation-contraction coupling?

A

calcium doesn’t bind to troponin like it does in skeletal muscle

ANP 1105 (10 decks)

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