Skeletal Muscle Flashcards by Matt Brittain

Muscle Fasciculus are

the individual bundles of muscle fibers in a skeletal muscle

How well did you know this?

Not at all

Perfectly

Muscle Fibers consist of

a single muscle cell

How well did you know this?

Not at all

Perfectly

Myofibrils are made up of

thick and thin myofilaments giving muscle its striped appearance

How well did you know this?

Not at all

Perfectly

Myofilaments consist of

thick fillaments (myosin), thin filaments (actin) and elastic filaments (titans)

How well did you know this?

Not at all

Perfectly

Skeletal muscle fiber size

extends the tntire lenght of a muscle, 10-80 micrometers in diameter

How well did you know this?

Not at all

Perfectly

How many muscles does one nerve innervate?

One, usuall in the midele of the fiber

How well did you know this?

Not at all

Perfectly

What encapsulates a muscle fiber?

the sarcolemma

How well did you know this?

Not at all

Perfectly

What is a muscle fiber made up of?

contains 100s to 1000s of myofibrils

How well did you know this?

Not at all

Perfectly

Myofibrils contain more of what than what?

More actin than myosin

How well did you know this?

Not at all

Perfectly

What does the Sarcoplasma contain?

Glycosomes (membrane-enclosed organelle that contains glycolytic enzymes), Myoglobin-Oxygen, Mitochondria, Calcium

How well did you know this?

Not at all

Perfectly

What type of proteins are myofilaments?

Polymerized proteins

How well did you know this?

Not at all

Perfectly

Actin:

3000 filaments, Thin filaments, Light I bands

How well did you know this?

Not at all

Perfectly

Myosin:

1500 filaments, Thick filaments, Dark A bands

How well did you know this?

Not at all

Perfectly

What is a sarcomere

the portion of myofibril between 2 consecutive Z-discs (gets smaller and larger depending on contraction)

How well did you know this?

Not at all

Perfectly

What are Z-discs made of?

structural proteins

How well did you know this?

Not at all

Perfectly

Wehre do Z-discs attach

to the ends of actin

How well did you know this?

Not at all

Perfectly

What do Z-discs interdigate with

myosin

How well did you know this?

Not at all

Perfectly

Puropose of Z-discs

attach myofibrils together along the entire muscle fiber

How well did you know this?

Not at all

Perfectly

What does a Titan do?

keeps actin and myosin in place

How well did you know this?

Not at all

Perfectly

Titan size

BIG protein - molecular weight of 3 million

How well did you know this?

Not at all

Perfectly

How does a titan work?

Titans are springy, the elastic end attaches to the Z-disc and the other end is tethered to myosin thick filament

How well did you know this?

Not at all

Perfectly

what are A bands?

mysin (thick filament) + ends of actin (thin filament)

How well did you know this?

Not at all

Perfectly

what are I bands?

actin (thin filament)

How well did you know this?

Not at all

Perfectly

what is the H zone?

just myosin, middle / zero interaction with actin

How well did you know this?

Not at all

Perfectly

what is a Z-disk?

structure of the myofibril (ends of actin/interdigitates myosin)

What is the M line

within the H zone; M = "mittelscheibe" = "middle" of sarcomere

What is a Titan

springy framework holding myosin in place

How many polypeptide chains does a myosin molecule have?

How many heavy chains does a myosin molecule have?

2 (MW = 200,000)

How many light chains does a myosin molecule have?

4 (MW = 20,000)

What configuration are myosin heavy chins in?

double helix (tail, ends fold bilaterally into globulare polypeptide structures = heads)

Describe the myosin light chains

4 light chains are part of the myosin heads (2 per head)

What does Calsequestrin do

Binds with Ca++ in the sarcoplasmic reticulum attracting it towards the channels for quick exit when needed

What are two things the myosin light chains do

*#1: help control the function of the head during contraction *#2: functions as an ATP enzyme

How many molecules make up myosin?

200+

How long is myosin filament

1.6 micrometers in length

Muscle from big to small

Muscle - muscle fascicles - muscle fibers - myofibrils (made of many sarcomeres) - myofilaments (made of actin, myosin, titan)

What are myofilaments made of?

actin, myosin, and titans

What are myofibrils made of?

many sarcomeres

What is Actin made up of?

2 F-actin molecules twisted like a helix - have G-actin molecules "active sites"

What does tropomyosin do?

Spirals around F-actin covering the "active sites" (G-actin molecules "G sites")

Troponin I has an affinity for:

Actin

Troponin T has an affinity for:

Tropomyosin

Troponin C has an affinity for:

Calcium

3 sources of energy

*1: Rephosphorylation of ATP (phosphocreatine-donates phosphate group to convert ADP to ATP) *2: Glycolysis (restores phosphocreatinine, direct energy for contraction in absence of O2, 2.5x faster than "foodstuff method" *3: Oxidative Metabolism (O2 + foodstuff = ATP)

One motor uniti is innervated by a single nerve fiber, how many muscle fibers are in each motor unit?

80-100 muscle fibers/motor unit

What is the motor end plate coverd by?

Schwann Cells (protection from surrounding enviornment)

What is the Synaptic Gutter?

Invagination caused by the nerve ending on the membrane layer

What is a Synaptic Cleft?

Space between terminal & fiber membrane (25 nanometers)

How does Choline enter the axon?

Via the Choline Transporter (CHT), sodium also enters with it

What is needed to synthesize (ACh)?

Acetyl CoA + Choline (and an enzyme)

What enzyme catalyzes synthesis of ACh?

Choline Acetyltransferase (CAT)

What moves ACh vesicles to the nerve terminal?

Vesicular Acetylcholine Transporter (VAT)

When ACh is released, what 2 things can happen?

*1: It attaches to a receptor *2: It is degraded

What degrades ACh in the synaptic cleft?

Acetylcholinesterase cleaves ACh into Choline + Acetate

What degrades ACh in plasma

Pseudocholinesterase

How are new vesicles formed?

After AP, "coated pits" appear in the nerve terminal and clathrin protein contracts forming new vesicles in the terminal

What are ACh vesicles attracted too in the nerve terminal?

Dense Bars

What allows ACh vesicles to attach to the pre-synaptic cleft and exocitose?

Ca++/Calmodulin dependent protein kinase that has beeen activated by calcium

How many ACh attach to an ACh receptor to create a conformational change (activation)

What charge does the ACh receptor have and what does it do?

Negative charge - repels negative ions and attracts positive such as Na+ (VIP)

Adult ACh is comprised of what subunits?

2x alpha 1 beta 1delta 1episilon

Fetal ACh is comprised of what subunits?

2x alpha 1 beta 1 delta 1 gamma

What allows action potentials depolarize the entire muscle?

Transverse tubules (T-tubuels)

What sections is the Sarcoplasmic reticulum divided into?

Terminal Cisternae and Longitudinal Tubules

An important voltage gated channel often targeted by calcium channel blockers:

Dihydropyridine receptor (DHP)

Receptor on the SR targeted by Dantrolene:

Ryanodine receptor

Two receptors that work together to release calcium from the SR in skeletal muscle:

Dihydropyridine receptor Ryanodien receptor

What do Desmosomes do?

Prevent sheering of cell connections

What do Connexins do?

Form intercellular gap junctions (channels that mediate direct signaling between cells)

What causes muscle fatigue?

glycogen depletion, bloodflow interruption

What causes Rigor Mortis?

ATP is all utilized. No more present to trigger release of myosin

How long until Rigor Mortis relaxes?

15-25 hours due to protien deterioration (myosin no longer connected)

How long is an AP in skeletal muscle?

1 - 5 milliseconds (5x longer than large myelinated nerves)