In order to get a long lasting contraction...

the binding sites on actin must remain opev

Why is it important the binding sites on actin must remain open

this depends on keeping Ca2+ levels elevated in the sarcoplasm

which in turn depends on a high frequency of nervous stimulation

Why do you need a high frequency of nervous stimulation?

if there's just one nerve impulse (actin potential), only a tiny amount of ACh is released

therefore the change in charge of the sarcolemma would only last a split second

when the charge ends, Ca2+ is quickly removed from the sarcoplasm and restored in the S.R

without Ca2+, the binding sites on actin for myosin heads get covered up

stiffness of deceased person's body

starts 3 hours after death and usually lasts 15-25 hours

What causes rigor mortis?

the supply of ATP begins to drop

Ca2+ levels in sarcoplasm rise, the sarcoplasmic reticulum can't Ca2+ efficiently with little ATP.

high Ca2+ causes a prolonged contraction

when ATP is completely gone, myosin heads are stuck to actin

Tension at the cellular level depends on:

the muscle fiber's resting(initial) length

the frequency of nervous stimulation

the cross-sectional area of the muscle cell(thicker fibers are stronger)

Why is resting length of the fiber important?t

the greater the number of myosin heads that bind to actin, the greater the tension or "pulling" power produced

overlapping thin filaments interfere with each other and thereby reduce tension

It influences the speed of muscle fatigue.

It determines the color of the muscle fiber.

When the muscle fiber (and sarcomeres) gets stretched apart, there's less and less overlap between thick and thin. So...

The muscle generates less tension.

The muscle fibers contract more efficiently.

The muscle generates more force.

When sarcomere is compressed too far, thin myofilaments from opposite sides get in each other's way. This causes.....

Increased muscle contraction strength.

Why is the frequency of nervous stimulation important?

one action potential (nerve impulse) produces a "twitch" in the muscle=a single cycle of bind pull release

as the frequency of action potentials increases so does the tension produced

max tension is produced when calcium levels are high enough to open nearly all the binding sites. Max # of myosin heads can bind and pull

Tension at the whole muscle level depends on:

amount of tension produced within each muscle fiber

the number (%) of muscle fibers that get activated within the whole muscle

How does the muscle engage in muscle mechanics with the nervous system

By activating different motor units as well as different numbers

Muscles contract independently of the nervous system.

The nervous system only relaxes muscles, not contracts them.

Muscle mechanics are solely controlled by hormones.

Some motor units are large. Motor neuron controls 1000s of muscle cells. What is an example?

Biceps brachii muscle motor units

Some motor units are small. Motor neuron only controls a small number of muscle cells. What is an example?

Biceps brachii muscle motor units

Is it better to have large or small motor units?

It depends on the activity; there is an important trade of between the amount of tension generated and the degree of fine motor control

Small motor units are only useful for strength training.

Large motor units are always better for all activities.

Motor units have no impact on performance.

How do contracted muscles return to their resting length?

Through interaction between thick and thin can only shorten a muscle; it cannot return a muscle to its original length

Muscles return to resting length through the process of fatigue.

Muscles remain contracted until stimulated again.

Muscles return to resting length by contracting further.

Muscles 2

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MULTIPLE CHOICE QUESTION

30 sec • 1 pt

How many steps are involved in muscle contraction?

10 steps

4 steps

5 steps

12 steps

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the first step of muscle contraction?

activating myosin heads by splitting ATP into ADP and P

myosin binds to actin

myosin pulls actin

myosin binds to a new ATP, this causes the myosin head to release from actin

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the second step of muscle contraction?

activating myosin heads by splitting ATP into ADP and P

myosin binds to actin

myosin pulls actin

myosin binds to a new ATP, this causes the myosin head to release from actin

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the third step of muscle contraction?

activating myosin heads by splitting ATP into ADP and P

myosin binds to actin

myosin pulls actin

myosin binds to a new ATP, this causes the myosin head to release from actin

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

What is the fourth step of muscle contraction?

activating myosin heads by splitting ATP into ADP and P

myosin binds to actin

myosin pulls actin

myosin binds to a new ATP, this causes the myosin head to release from actin

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Immediately after binding to actin, the myosin head pivot. The energy that was stored in the _____ head powers the pull. ADP and P are finally released.

tropomyosin

titin

cocked

actin

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Neural stimulation is the first in the sequence of muscle contraction

True

False

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Muscles 2

How many steps are involved in muscle contraction?

What is the first step of muscle contraction?

What is the second step of muscle contraction?

What is the third step of muscle contraction?

What is the fourth step of muscle contraction?

Immediately after binding to actin, the myosin head pivot. The energy that was stored in the _____ head powers the pull. ADP and P are finally released.

Neural stimulation is the first in the sequence of muscle contraction

1. The ___ or _ __ activates a motor neuron which is a nerve cell that controls muscle

2. Nerve impulse(aka. action potential) reaches the end of the motor neuron and causes the release of __________ (ACh; a neurotransmitter)

3. ACh diffuses across the tiny space that separates the end of the motor neuron from the sarcolemma. This tiny gap is called the ______ _.

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Muscles 2

How many steps are involved in muscle contraction?

What is the first step of muscle contraction?

What is the second step of muscle contraction?

What is the third step of muscle contraction?

What is the fourth step of muscle contraction?

Immediately after binding to actin, the myosin head pivot. The energy that was stored in the _____ head powers the pull. ADP and P are finally released.

Neural stimulation is the first in the sequence of muscle contraction

1. The _____ or _____ ____ activates a motor neuron which is a nerve cell that controls muscle

2. Nerve impulse(aka. action potential) reaches the end of the motor neuron and causes the release of __________ (ACh; a neurotransmitter)

3. ACh diffuses across the tiny space that separates the end of the motor neuron from the sarcolemma. This tiny gap is called the ____________ _______.

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1. The ___ or _ __ activates a motor neuron which is a nerve cell that controls muscle

3. ACh diffuses across the tiny space that separates the end of the motor neuron from the sarcolemma. This tiny gap is called the ______ _.