Review Session Ch 18, 19 Flashcards by Austin Knutson

A motor unit:

Is a neuron and all the muscle fibers it is connected to
-contains only one type of muscle fiber
-receives input from higher brain centres

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Sarcoplasmic reticulum
-where the calcium is stored

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These are exchanged across the sarcolemma during contraction

Sodium and Potassium

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Axons

Transmit electrical signals from nervous from nerves to muscle fibers

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Motor neurons

Nerve cells that are connected to muscle fibers

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Motor cortex

Part of the brain where voluntary contraction originates

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Transverse tubule

Indentation of the muscle fibers membrane (sarcolemma)

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What are two ways you can increase your force development through how you recruit motor units?

Recruit more, increase firing rate

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What causes force summation?

Ca2+ is not fully released so muscle is not fully removed

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What causes tetanus

Force maximized through growing summation up to max
-excess of Ca2+

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Summation occurs:

When a stimulus is delivered to a muscle before it has time to completely relax

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Tetanus occurs:

When you have a very high amount of calcium released from the SR

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A single motor unit can have a mixture of fast twitch and slow twitch muscle fibers

Fast- can only have one type of

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When an action potential is generated in the axon of a motor neuron, only a portion of muscle fibers innervated by that axon will contract if the action potential isn’t strong enough

False -all fibers innervated by the axon will contract

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fast twitch motor units usually have a higher number of muscle fibers compared to slow twitch motor units?

True -large motor units

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Muscle hypertrophy occurs during the first week of strength straining at the same time that strength increases

False -takes some time for it to occur

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You can use your higher brain centres not override the GTO inhibition of motor neurons

False -if GTO is firing, can’t override it directly

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Do you think the muscle spindle is more active or less active during a muscle cramp?

Muscle spindle is more active

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Long duration of static stretching can impair subsequent strength/ power performance

True -plyometric exercise would be better

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What activity will be improved by activation of the muscle spindle?

The ability to jump higher for a basketball rebound
-spindle would cause muscle to contract during stretch

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Proteins found in a sarcomere

Actin, myosin, ATPase, tropomyosin, Troponin

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Proteins involved in muscle contraction

Actin, myosin, ATPase, tropomyosin, Troponin

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Proteins that can prevent muscle contraction

Troponin and Tropomyosin

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Fast contracting fiber type

Type 2x

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Energy currency of a cell

ATP

Enzyme involved in muscle contraction

ATPase

Which of the following is the smallest structure

Myosin -very small

An enzyme:

Is a protein, a molecule that increases the rate of chemical reactions, could change its level following exercise training

What suffix is commonly used to describe an enzyme

-are

Using -are, name the enzyme that is involved in the reaction where ATP is broken down for energy

ATPase

Which protein interacts with myosin during muscle contraction

Actin

Where 2 proteins are involved in the blocking of myosin to prevent muscle contraction (when the muscle is relaxed)

Troponin and Tropomyosin

There are three main fiber types : type 1 (slow, type 2a (intermediate), fast (2x)

True

The fiber types an individual possesses is determined by genetics and can not be changed

False -individual could train

Type 1 fibers are the fastest contracting fibers in humans

False -fastest are 2x

Strength training leads to a conversion of slow fibers to fast fibers

False -not a conversion, but fast fibers will adapt to be faster or slower

Largest to Smallest components:

Whole Muscle > Muscle Fascicles > Muscle Fibers > Myofibrils > Sarcomeres > Actin and Myosin > Myosin Heavy Chains

What are the contractile proteins

Actin and myosin

What are the regulatory proteins

Troponin and tropomyosin

Which protein binds calcium

Troponin

What is bordered by the z-discs

Sarcomere

What protein blocks binding sites on actin

Tropomyosin

What protein controls speed of contraction

ATPase

After a muscle contractions, what ion must be removed from the cytoplasm of the muscle cells before relaxation can happen?

Calcium

Force productions:

Eccentric (highest) Isometric (middle) Concentric (least)

Where is ATPase enzyme found in skeletal muscle?

In the globular head on the myosin head, in the SR, in the sarcolemma

Type 2x breakdown

High ATPase, fast fatigueable

Type 1 breakdown

Low ATPase, slow twitch

Type 2a breakdown

Fast fatigue resistant

Classifications based on myosin heavy chains use

Types of fibers (1, 2a, 2x)

Classification based on metabolic properties

Slow oxidative, fast glycolytic

Describe how motor unit recruitment (i.e. recruitment of fast or slow twitch or intermediate motor units) would change as one goes from a slow walk to a jog to a sprint.

Recruit type 1 slow twitch during walk, as intensity increases, more would be recruited and more fast twitch would be recruited

Which receptor when activated causes reflex contraction of muscle?

Muscle spindle

Which receptor when activated causes inhibition of contraction?

GTO

Which receptor causes activation of antagonistic musculature?

GTO

Which receptor causes inhibition of antagonistic musculature?

Muscle spindle

Reflex contraction of s muscle after spindle activation

Efferent

Your eyes transmit a signal to your brain about the position of a soccer ball

Afferent

Voluntary contraction of your biceps by recruitment of motor neurons in the spinal cord

Efferent

Golgi tendon is activated, sending inhibitory signal to the muscle

Efferent

Vestibular (inner ear) sensors send a message to your brain to correct your balance

Afferent

A motor neuron receives 10 excitatory impulses from one other neuron over the time period of 2 ms

Temporal summation

Another motor neuron receives one excitatory impulse from each of 5 different neurons

Spatial summation

A motor unit has only one motor neuron but many muscle fibers

True

A motor unit can have a mixture of slow twitch and fast twitch muscle fibers

False -can only have one or the other

When a motor neuron is activated, only a portion of the muscle fibers in that motor unit will contract if low intensity exercise is being performed

False -all or none

Motor units in different muscles throughout the body are the same size

False

Sarcoplasmic reticulum -where calcium is stored

Sodium and potassium

Influx/ eflux of these cause change in membrane potential

Transverse Tubule

Transmits action potential from neuron to muscle fiber

Motor neurons

Nerve cells connected to muscle fibers

Motor cortex

Part of the brain where voluntary contraction originates

Acetyl Choline

Excites membrane and changes permeability

Axons

Covered by a myelin sheath

Motor unit

A motor neurons and all the muscle fibers that are connected to it

Fast-twitch muscle fibers require a higher frequency electrical input to reach tetanus compared to slow twitch fibers. Why is this so?

Because they relax faster

Hyperpolarize

Membrane potential changes from -70mV to -90mV

Depolarize

Membrane potential changes from -70mV to -50mV

Repolarize

Membrane potential changes from +40mV to -60mV

Excitation contraction coupling steps

1. Impulse, calcium causes ACh release -diffuses act cross synaptic cleft, changes membrane permeability 2. At threshold =depolarizes T-Tubule 3. Repolarization of T-Tubule causes Ca2+ to release from SR 4. Ca2+ binds to Troponin and tropomyosin, allows actin+myosin to combine 5. Actin combines my son, ATPase activated to split ATP into energy 6. Sliding of actin and myosin -cross bridge detaches from actin 7. Continued new cord bridge occurs if Ca2+ remains -depolarization inhibits Troponin- tropomyosin complex) 8. Muscle stim stops, Ca2+ moves back to SR 9. Removes Ca2+ ,restarts Troponin-tropomyosin inhibitory -muscle relaxes