Exm 3 (ch 10) Flashcards by Sarah Salinas

The organization of muscles? Smallest to largest

Muscle filaments -> myofibrils -
> muscle fibers -> fascicle ->
muscle organ

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Fibrous connective tissue that surrounds the entire muscle organ

Epimysium

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Connective tissue that surrounds a fascicle (group of muscle fibers)

Perimysium

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Connective tissue that surrounds each muscle fiber

Endomysium

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What is responsible for contraction?

Sarcomere

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Invagination of sarcoplasm that carry action potential, stimulating the muscle to contract

T Tubules

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Is a membrane sac that wraps around each myofibril. Calcium is released here.

Sarcoplasmic reticulum

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Sarcoplasmic reticulum on both sides of the T tubule

Terminal cisterns

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Cells between the Endomysium and muscle fiber. provides extra nutrients. Their function is to repair damaged muscles.

Satellite cells

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Connective tissue that extends beyond the muscle and attaches muscle to bone (epimysium)

Tendons

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Broad and flat tendons are called

Aponeurosis

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Each muscle fiber is made of myofibrils that have

Myofilaments (myosin and actin)

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Gives muscle fiber its elasticity. (The squiggly line connected to myosin in a sarcomere)

Titin

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Lighter, less dense area of sarcomere that contains remainder of thin filaments, but no thick, filaments. A Z disc passes through the center of each. Only thin filaments.

I band

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Dark, middle part of sarcomere that extends entire length of thick filaments, and includes those parts of thin filaments that overlap the thick filaments. Extends the entire length of thick filaments, even where there is no overlap.

A band

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Narrow region in center of each A band that contains thick filaments, but no thin filaments

H band

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Narrow, plate shaped regions of dense material that separate one sarcomere from the next

Z discs

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Has the filament attachments with no cross bridges

M line

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Which two change as muscle contracts

I and H band

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Muscle proteins. Contractile:

Myosin and actin

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Muscle proteins. Regulatory:

Troponin and tropomyosin

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Muscle proteins. Structural:

Titin

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When calcium is released from ____ it binds specifically to_____.

Sarcoplasmic reticulum. Troponin.

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Ca2+ release from sarcoplasmic reticulum -> binds troponin ->troponin/tropomyosin complex exposes actin binding sites -> myosin attaches -> head bends

Powerstroke

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Cross-bridge can’t detach since ATP synthesis has ceased. Calcium leaks out of sarcoplasmic reticulum

Rigor mortis

All fibers stimulated by a single motor neuron

Motor unit

What controls the strength of the contraction?

Motor neurons

Axons from these motor fibers secrete what

Acetylcholine

When you stimulate a motor neuron it is a what kind of response

An all or nothing response

pulls remaining acetylcholine out of the synapse at the NMJ – depolarization of the postsynaptic membrane stops which causes the sarcoplasmic reticulum to stop releasing calcium

Acetylcholinesterase

______ in sarcoplasmic reticulum binds calcium and allows for even more Ca2+ storage. A conditional component of sarcoplasmic reticulum. Activated by Ca2+-ATPase. A way to stop contraction

Calsequestrin

Troponin/tropomyosin falls back over the binding sites from what?

The lack of Ca2+

________:enlargement of existing muscle fibers. Due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum and other organelles

Muscular hypertrophy

______: increase in the number of fibers due to satellite cells, growing slow and helping build muscle

Muscular hyperplasia

______: decrease in size of muscle fibers due to loss of myofibrils. Occurs as a result of aging or disuse. Lack of exercise can cause ~flaccid~ muscle that gets flabby and soft – call it ~atrophied~

Muscle atrophy

Muscles have 3 ways to produce ATP:

Creatine phosphate, anaerobic glycolysis, aerobic respiration

rapid use but runs out quickly

Creatine phosphate

not very effective long-term

Anaerobic glycolysis

longer to make but most effective

Aerobic respiration

Creatine phosphate. Need energy:

creatine phosphate donates phosphate to ADP making ATP and creatine

At rest: phosphate attached to creatine

Creatine phosphate

Duration of energy provided for creatine phosphate

15 seconds

When creatine phosphate stores are depleted, glucose is converted into pyruvic acid to generate ATP via

Anaerobic glycolysis

Producing 2 ATP for every glucose that you feed into this cycle

Anaerobic glycolysis

Duration of energy provided for anaerobic glycolysis

2 minutes

Under aerobic conditions, pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of A T P

Aerobic respiration

Our main source of energy

Aerobic respiration

Our main source of energy

Aerobic respiration

Duration of energy provided for aerobic respiration

Several minutes to hours

Is the inability to maintain force of contraction after prolonged activity

Muscle fatigue

occurs due to changes in the central nervous system and generally results in cessation of exercise

Central fatigue

consists of a somatic motor neuron and the muscle fibers it innervates

A motor unit

Activating only a few motor units will generally result in a

Weak muscle contraction

Motor units contract alternatively, to sustain contractions for longer periods of time

Motor unit recruitment

The brief contraction of all muscle fibers in a motor unit in response to a single action potential

A single motor unit contraction

very short, the time period between threshold stimulus and shortening of muscle. Right when muscle receives impulse

Latent period

shortening of muscle

Contraction period

returns to original length and Ca2+ returns to sarcoplasmic reticulum

Relaxation period

after contraction when muscle cannot immediately respond to threshold stimulus

Refractory period

after one complete twitch muscle uses the same stimulus to make the contraction greater than the original

Treppe

is what happens BEFORE completion of the relaxation period

Wave summation

Even when at rest, a skeletal muscle exhibits a small amount of tension called_____ . It is established by the alternating, involuntary activation of small groups of motor units in a muscle

Tone

tension is constant while muscle length changes

Isotonic

(Isotonic) concentric

Muscle length shortens

(Isotonic) eccentric

Muscle length lengthens (while lowering a weight). Sort of like relaxing or being overpowered.

muscle contracts but does not change length

Isometric

Muscle fibers that bind O2, and don’t fatigue as fast

Myoglobin

lots of myoglobin, red • Marathon runners

Slow oxidative

glycolytic fibers with lots of myoglobin, red • 5K runners

Fast oxidative

low myoglobin and white in color • Sprinters or body builders

Fast glycolytic

The site of aerobic respiration

Mitochondria

centrally- located nucleus, intercalated discs , and desmosomes. Gap junctions allow action potentials to spread from one muscle fiber to another. Branched

Cardiac muscle

muscle cells have more mitochondria and their contractions last 10-15 times longer than skeletal muscle contractions

Cardiac

muscle contractions start more slowly and last longer than the other 2. Stretchy. Dense bodies: scattered throughout cytoplasm and attach to sarcolemma, similar to Z discs. Myofilaments attach to dense bodies and pull when muscle contracts

Smooth muscle

binds calcium NOT troponin • Activates myosin light chain kinase -> phosphorylation of myosin head -> actin attaches

Calmodulin

Neuromuscular junction from beginning to end

action potentials trigger voltage gated calcium channels->exocytosis of acetylcholine->Na+ channels on the postsynaptic membrane open-> depolarization of the muscle -> calcium release from the sarcoplasmic reticulum