LEC EXAM #3 CHP 9 Flashcards by Natasha Tenen

6 functions of skeletal muscle:

skeletal movement
store nutrient reserves
support soft tissues
guard openings
body temperature
body position

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Myoglobin is specific to:

Skeletal and cardiac muscle tissues

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Myoglobin binds:

Oxygen

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What is a power stroke?

Movement of myosin cross bridges pushes actin towards center of sarcomere

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What does the end of a power stroke consist of?

Myosin releases bound actin and grabs another actin molecule

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Skeletal muscle stores:

Glycogen

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Striations have:

Contractile fibers

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When muscle tissues are damaged they release:

Myoglobin into blood and lactate dehydrogenase

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Dark line:

Light line:

Myosin

Actin

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Myoglobin has a higher affinity for:

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Skeletal muscle structure:

Repeating circular bundles

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What is tennis elbow?

Makes sheaths flat instead of round

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What is stored at the sarcoplasmic reticulum?

Calcium

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Z line connects/anchors:

Actin (always thin)

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Space where there is ONLY actin:

I band

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Space where actin and myosin overlap:

A band

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M line anchors:

Myosin (always thick)

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Space where there is ONLY myosin:

H band

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Sheath like protein that covers binding site:

Tropomyosin

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Beaded complex where calcium binds:

Troponin

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ATPase is where:

ATP binds to get myosin head activated

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What are the steps of contraction?

AP in t-tubule alters DHP receptor
DHP receptor causes calcium to bind to troponin
Moves tropomyosin out of the way for myosin to bind to actin

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Why do we need calcium?

To move tropomyosin

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Neuromuscular junction:

Regulates force

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Axon contains:

Na V.G.C.

The nerve synapses with the skeletal muscle at the:

Motor end plate

Acetylcholesterase:

An enzyme that breaks down acetyl--coa

The holes of the t-tubule take it deep into the:

Skeletal muscle

Relaxation steps:

ATP pulls apart actin and myosin cross bridge ATP splits into ADP and phosphate Activates head for power stroke ADP and phosphate leave

What stops skeletal muscle contraction?

Nerve by nerve impulse shutting off -> no more acetyl-coa

What regulates skeletal muscle?

Somatic nervous system

Relaxation begins in the:

Brain

Relaxation requires: Contraction requires:

ATP Calcium and ATP

Rigor mortis:

Stiffness of muscles after death for 72 hours, caused by lack of ATP

TEA:

- Blocks potassium voltage gated channels - K+ cannot repolarize via K+ v.g.c. - long drawn out repolarzation-> hyper-excitable (above 55)

Curare:

- Blocks nicotinic cholinergic receptors - no nerve->nerve conduction - no nerve-> skeletal muscle conduction

Esterine/physostigmine:

- blocks Acetylcholesterase (AchE) - Ach stays in synapse - continued contraction

Organophosphates (never toxins):

- blocks AchE | - causes continuous contraction

Myasthenia gravis:

- autoimmune disease - antibodies attack nicotinic cholinergic receptors - no AP/ no skeletal muscle contraction - use eserine to increase Ach in the synapse

What allows action potentials to go deep into where contractile fibers are? (nerve-> skeletal muscle)

T-tubules

What floods into the area where the contractile fibers are, causing excitement of skeletal muscle?

Calcium

Once calcium floods the area where the contractile fibers are, where the actin and myosin are, what does calcium bind to?

Troponin

Calcium then moves:

Tropomyosin away from the actin

What ion or molecule do we have to have to move tropomyosin?

Calcium

Myosin is now bound to actin, what causes the power stroke/contraction?

- Phosphate leaves - get power stroke - then ADP leaves - stuck here until ATP binds

ATP releases:

crossbridge

ATP will bind if:

Calcium is present

REQUIRED for contraction/power stroke:

ATP and calcium

What ion causes the vesicle to dump into the synapse?

Calcium

Curare does not effect:

nerve -> heart | nerve -> digestive tract

If curare is stuck here, what cannot bind?

Ach

Threshold stimulus:

Strength of stimulus required to cause a twitch

Latent period:

Delay between stimulus and contraction

Twitch:

Single, brief contraction of a muscle fiber after a single threshold stimulus

Relaxation is caused by:

Transport of calcium back into the sarcoplasmic reticulum

What is the "all or none" principle?

At threshold, a fiber will contract its maximum extent

Tension of a single muscle fiber depends on:

- fiber's resting length at time of stimulation - frequency of stimulation - number of pivoting cross bridges

Skeletal muscles are capable of:

graded responses

The force of muscle contraction can increase by:

Summation or recruitment

Refractory period:

time between initial and subsequent stimuli that is required for sarcolemma to repolarize

Summation:

Greater force generated from more frequent stimuli

Tetanic contraction:

- Continuous contraction without relaxation between stimuli | - all motor units of muscle are activated

Fatigue:

Loss of response due to lack of ATP

Motor unit:

Motor neuron + all the fibers it controls

Motor unit rule:

All muscle cells in a motor unit respond maximally, or they don't respond at all

Each motor neuron on average controls:

150 fibers

Recruitment:

increasing the number of motor units activated/responding

Strength increases as...

the number of motor units increases

2 types of tension production:

- sustained tension | - muscle tone

Sustained tension:

- less than maximum tension - allows motor units to rest in rotation - uses a lot of ATP

Muscle tone:

-the normal tension and firmness of a muscle at rest

Increasing muscle tone increases:

metabolic energy used even at rest

We use sustained tension to:

Actively maintain body position without motion (isometric contraction)

CrP (creatine phosphate):

stored in skeletal muscle and used to make ATP for skeletal muscle contraction

When muscle can no longer perform a required activity, they are:

Fatigued

4 results of muscle fatigue:

- depletion of ATP - damage to sarcolemma and sarcoplasmic reticulum - low pH - muscle exhaustion and pain

The time required after exertion for muscles to return to pre-exercise condition:

Recovery period

In recovery period, you have to deal with: (3)

- depletion of metabolic reserves by making more glycogen and ATP via aerobic metabolism-> breath heavy - repair sarcolemma and sarcoplasmic reticulum - recover from low pH by processing lactic acid via cori cycle

How does the cori cycle play a role in recovery period? (3)

- removal and recycling of lactic acid by the liver - liver converts lactic acid to pyruvic acid - glucose is released to recharge muscle glycogen reserves

Muscle hypertrophy:

muscle growth from heavy training

Muscle atrophy: effects:

lack of muscle activity | -reduces muscle size, tone, and power

3 effects of muscle hypertrophy:

- increases diameter of muscle fibers - increases number of myofibrils - increases mitochondria, glycogen reserves

Muscle fibers break down into:

Proteins