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BIO 212 Class > Unit 5 Study Guide > Flashcards

Unit 5 Study Guide Flashcards

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Biology 101 flashcards
1
Q

Fascicles

A
  • muscle fibers organized into bundles

- are bundled within the whole skeletal system

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2
Q

Epimysium

A

layer of dense irregular connective tissue that surrounds the whole skeletal muscle

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3
Q

Perimysium

A
  • surrounds the fascicles

- contains extensive arrays of blood vessels and nerves that branch to supply muscle fibers within each fascicle

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4
Q

Endomysium

A
  • innermost connective tissue layer
  • surrounds and electrically insulates each muscle fiber
  • Contains reticular protein fibers that help bind together neighboring muscle fibers and to support capillaries near this fiber
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5
Q

What is the purpose of the three layers of connective tissue?

A
  • provides protection
  • sites for distribution of blood vessels and nerves
  • site for attachment to skeleton
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6
Q

What is the purpose of the skeletal muscle’s being vascularized?

A
  • the extensive network of blood vessels deliver both oxygen and nutrients to the muscle fibers
  • also remove waste products
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7
Q

neuromuscular junction

A

the junction(gap) between an axon and muscle fiber

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8
Q

Sarcoplasm

A

the cytoplasm in the skeletal muscles

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9
Q

satellite cells

A
  • the myoblasts that do not fuse with the muscle fibers during development
  • remain in adult skeletal muscle
  • can be stimulated to differentiate and fuse with a damaged skeletal muscle to assist in repair and regeneration to a limited extent
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10
Q

Sarcolemma

A
  • The plasma membrane of the skeletal muscle fiber

- connected to the SR by T-tubules

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11
Q

T-Tubules

A
  • deep invaginations of the sarcolemma

- extend into the skeletal muscle fiber as a network of narrow membranous tubules to the sarcoplasmic reticulum

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12
Q

What type of channel(s) are located in the sarcolemma and T-tubules

A

-Na+ and K+ Voltage gates channels

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13
Q

Myofibrils

A
  • compose the muscle fiber
  • extends the length of the muscle fiber
  • composed of bundles of myofilaments enclosed within segments of the SR
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14
Q

Sarcoplasmic Reticulum

A
  • reservoir for Ca2+ ions

- contains Ca2+ pumps and Ca2+ voltage-gated channels

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15
Q

Terminal Cisternae

A
  • blind sacs at either end of individual sections of the SR
  • serve as reservoirs for calcium ions
  • immediately adjacent to each T-Tubule
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16
Q

Triad

A

-formed by two terminal cisternae and a centrally located t-Tubule that function during muscle contraction

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17
Q

Thick Filaments

A
  • assembled from myosin protein molecules
  • the head contains a binding site for actin of the thin filaments
  • contains a catalytic site where ATP attaches
  • myosin molecules are oriented so that their long tails point toward the center of the thick filaments and the heads point toward the ends of the thick filaments
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18
Q

Thin Filaments

A
  • composed of two strands of actin protein that are twisted around each other to form a helical shape
  • Each actin contains a myosin binding site
  • the myosin head attaches to the myosin binding site of actin during muscle contraction
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19
Q

Tropomyosin

A
  • regulatory protein associated with thin filaments

- covers the myosin binding sites in a non contracting muscle

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20
Q

Troponin

A
  • regulatory protein associated with thin filaments
  • attached to tropomyosin
  • contains the binding site for Ca2+
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21
Q

Connectin

A
  • protein that extends from the Z disks to the M line through the core of the thick filament
  • stabilizes the position of the thick filament
  • maintains thick filament alignment within a sarcromere
  • contributes to muscle elasticity
22
Q

Dysotrophin

A
  • anchors myofibrils that are adjacent to the sarcolemma to proteins within the sarcolemma
  • links internal myofilament proteins to a muscle fiber to external proteins
23
Q

Myoglobin

A

-binds oxygen when the muscle is at rest and releases it for use during muscular contraction

24
Q

List the steps that occur at the neuromuscular junction

A
  • a nerve signal is propagated down a motor axon and triggers the opening of voltage-gated Ca2+ channels, releasing it into the synaptic knob
  • Ca2+ binds to proteins in synaptic vesicle membrane
  • calcium binding triggers synaptic vesicles to merge with the synaptic knob plasma membrane and ACh is exocytosed into the synaptic cleft
  • ACh diffuses across the fluid-filled synaptic cleft in the motor end plate to bind with ACh receptors-causes excitation of a skeletal muscle fiber
25
Q

What is the structure and function of the motor end plate?

A
  • specialized region of the sarcolemma of a muscle fiber.
  • Numerous folds and junctions fold to increase the surface area covered by synaptic cleft.
  • has vast numbers of ACh receptors, which upon ACh binding, allows Na+ to flow into the muscle fiber and K+ to exit
26
Q

What is the end plate potential?

A
  • the minimum voltage change in the motor end plate that can trigger opening of voltage-gated channels in the sarcolemma to initiate an action potential.
  • Goes from -90mV to -65mV.
  • The EPP initiates an action potential to be propagated along the sarcolemma and T-Tubules
27
Q

Describe the steps in excitation-contraction coupling?

A

1) ACh binding causes chemically-gated ion channels to open and Na+ to rapidly enter the skeletal muscle fiber and K+ to slowly exit, which results in the development of an end-plate potential at the motor end plate.
- initiation and propagation of an action potential along the sarcolemma and T-tubules (depolarization and repolarization)
- action potential triggers release of Ca2+ from the terminal cisternae of the sarcoplasmic reticulum. Diffuses into the sarcoplasm

28
Q

Sarcomere

A
  • repeating microscopic cylindrical units of myofilaments

- composed of overlapping thick and thin filaments

29
Q

Z discs

A
  • at the end of each sarcomere
  • composed of specialized proteins that are positioned perpendicular to the myofilaments
  • serve as anchors for the thin filaments
30
Q

I band

A
  • extend from both directions of Z disc
  • contain only thin filaments
  • disappears during contraction
31
Q

A Band

A
  • central region of sarcomere that contains the entire thick filament
  • thin filaments overlap thick filaments on each end
  • does not change in length during muscle contraction
32
Q

H Zone

A
  • most central portion of the A band
  • only thick filaments are present
  • disappears during contraction
33
Q

M line

A
  • thin protein meshwork in the center of the H zone
  • Attachment site for the thick filaments
  • aligns the thick filaments during contraction/relaxation
34
Q

Steps of Crossbridge Cycling

A
  • Calcium binding
  • Crossbridge formation
  • Power stroke
  • Release of myosin head
  • Reset myosin head
35
Q

Calcium binding

A
  • Ca2+ from SR binds to troponin in muscle thin filaments, causing a conformational change in troponin
  • Troponin changes shape and the entire troponin-tropomyosin complex is moved
  • tropomyosin no longer covers the myosin binding site on actin
36
Q

Crossbridge formation

A
  • myosin heads, in a cocked position, bind to exposed myosin binding site on actin forming a cross bridge between the thick and thin filaments (myosin and actin)
37
Q

Power stroke

A
  • the myosin head swivels toward the center of the sarcomere, pulling along the attached thin filament a small distance past the thick filament - power stroke
  • ADP and Pi released
  • ATP binding site becomes available again
38
Q

Release of myosin head

A
  • ATP binds to ATP binding site on myosin head

- causes release of the myosin head from the binding site on actin

39
Q

Where ATP is used in muscle contraction

A
  • ATP is used during release of the myosin head
  • It binds to the binding site on the myosin head,
  • causes the release of the myosin head from the actin binding site
  • provides energy to reset the myosin head
40
Q

Phosphagen system

A
  • an additional few seconds of energy generated by transfer of a high-energy phosphate
  • Myokinase transfers a phosphate from one ADP to another ADP, yielding ATP and AMP
  • Creatine kinase transfers a Pi from creatine phosphate to ADP, yielding ATP and creatine
  • proves an additional 10-15 seconds of energy
  • during times of rest, as small amounts of ATP accumulate, the pathway is reversed
41
Q

Aerobic cellular respiration

A
  • Occurs within mitochondria
  • nutrient source is pyruvate made in glycolysis
  • oxidized to CO2 in Krebs
  • results in NADH and FADH2
  • Used in ETC to generate ATP through oxidative phosphorylation
42
Q

Anaerobic cellular respiration

A
  • Goes through glycolysis then fermentation
  • used to regenerate NAD+
  • Pyruvic acid or organic molecule is final electron acceptor
  • Only 2 ATP produced from glycolysis in entire process
43
Q

Structural characteristics of cardiac muscle

A
  • individual muscle cells arranged in thick bundles in heart wall
  • branch and are shorter and thicker than skeletal
  • individual cells joined at intercalated junctions
  • striated
  • controlled by ANS
44
Q

intercalated junctions

A
  • where individual cardiac muscle cells join to adjacent muscle
45
Q

Structural characteristics of smooth muscle

A
  • small and widest in middle with tapered ends and centrally located nucleus
  • diamater 10X small and lengths 1000X shorter
  • endomysium wraps around each smooth muscle cell. Tapered ends overlap
  • T-tubules are absent
  • Sarcolemmal surface area increased by caveolae
  • No Z discs or sarcomeres
46
Q

Smooth muscle thin filaments

A
  • composed of actin and tropomyosin but do not contain troponin
  • instead have Calmodulin
47
Q

Calmodulin

A
  • binds to Ca2+ and forms Ca2+-calmodulin complex
48
Q

Myosin Light-chain kinase (MLCK)

A
  • activated by Ca2+-calmodulin complex to phosphorylate smooth muscle myosin head
  • activation of ATPase activity
49
Q

Steps of smooth muscle contraction

A
  • Stimuli triggers opening of voltage-gated Ca2+ channels
  • enters sarcoplasm from IF and SR
  • binds to Calmodulin, forming Ca2+-calmodulin complex, and activating MLCK
  • MLCK phosphorylates myosin head and actives myosin - slow
50
Q

Activated myosin

A
  • binds to thin filaments to form cross bridges.
  • Myosin ATPase hydrolyzes ATP providing energy for power stroke
  • Myosin head releases and reattaches to actin repetitively, causing the thin filament to slide past the thick filament.
  • the process is repeated
  • the force generated is transferred to the anchoring filaments and the smooth muscle shortens
  • allow for much stronger contractions.
51
Q

RyR1 receptor

A

mediates release of Ca2+ from sarcoplasmic reticulum into the cytoplasm

52
Q

DHP receptors

A
  • found in T-tubule membrane

- arrival of AP initiates change in receptor (allows Na+ in) which initiates a change in RyR1 receptor

BIO 212 Class (12 decks)

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