CHAPTER 8 Exam 1

Calcium.

What causes the tropomyosin to cover back over actin binding sites?

Endomysium

structural organization of skeletal muscle Each individual muscle fiber is surrounded by a delicate connective tissue layer called the

epimysium

structural organization of skeletal muscle an entire skeletal muscle is covered by a connective tissue layer called the

perimysium

structural organization of skeletal muscle each fascicle (bundle of muscle fibers) is wrapped within a layer of connective tissue called the

contractile process

the end plate potential is always large enough to excite threshold and is the signal to begin the?

IIx

the myosin ATPase activity in type ___ fibers is higher than other fibers types resulting in the highest Vmax of all fiber types; they also generate the highest power output

myonuclear domain

the region of cytoplasm surrounding an individual nucleus is termed ? the importance of this is that a single nucleus is responsible for the gene expression for its surrounding cytoplasm

the oxidative capacity, the type of myosin isoform, and the abundance of contractile protein within the fiber

the three primary biomechamical characteristics of muscle that are important to muscle function are?

greater

type IIx fibers are less efficient than all other fibers- this low efficiency is due to the high myosin ATPase activity, which results in a ___ energy expenditure per unit of work performed

Phosphocreatine, glycolysis, and oxidative phosphorylation

what are the three sources of ATP production in muscle during contraction?

calcium

what ion is released from the sarcoplasmic reticulum that is required for triggering a muscle contraction?

high concentration of myoglobin, the large number of capillaries and the high mitochondrial enzyme activity

what provides type I fibers with a large capacity for Oxidative (aerobic) metabolism (Capacity of the fiber to USE oxygen to make ATP in the mitochondria) and a high resistance to fatigue?

Ca+; cross-bridge

when __ bind to troponin, tropomyosin is removed from the active sites on actin and _____ attachments can occur

motor unit

A ______ contains all of the muscle fibers innervated by a SINGLE nerve

myoglobin; mitochondria & capillaries

Characteristics of Muscle Fiber Types Biochemical properties: -*Oxidative capacity* muscle fiber with a high concentration of _____ along with a high number of ____ and ____ will have a high aerobic capacity and therefore will be fatigue-resistant during prolonged sub maximal exercise

degrade ATP rapidly

Characteristics of Muscle Fiber Types Biochemical properties: -*Type of myosin ATPase* muscle fibers that contain ATPase isoforms with high ATPase activity will ______; this results in a high speed of muscle shortening (muscle fibers with low ATPase activities shorten at slow speeds)

type I fibers

Fine motor movement are controlled by

Oxidative (aerobic) capacity

-Capacity of the fiber to USE oxygen to make ATP in the mitochondria -Determined by the number and oxidative capacity of mitochondria -I > IIa> IIx

Glycolytic (anaerobic) capacity

-Capacity of the fiber to make ATP WITHOUT using oxygen or the mitochondria -Determined by enzyme capacity of glycolysis (anaerobic) -IIx> IIa> I

type I fibers

-Postural muscles (soleus) are predominantly

Satellite cells

-migrate from muscle fiber basement membrane to become myoblasts (embryonic myotubes). -Then differentiate into mature muscle fibers or new myonuclei -Influenced by various growth factors

six steps of the sliding filament theory

1.) The influx of calcium triggering the exposure of binding sites on actin. 2.) The binding of myosin to actin forming a cross bridge. 3.) The power stroke of the cross bridge that causes the sliding of the thin filaments. 4.) The binding of ATP to the myosin head which results in the myosin head disconnecting from Actin. 5.) The hydrolysis of ATP which leads to the re-energizing and repositioning of the Myosin head. 6.) The transport of calcium ions back into the sarcoplasmic reticulum.

A

A muscle contraction begins with release of _______, which reaches a sarcolemma, depolarizing the sarcolemma. A) Acetylcholine B) ATP C) Troponin D) Calcium

sodium; into

Ach receptors are actually ___ channels which allow ___ to flood ____ cell

I band

Actin filament occur principally in the light regions of the sarcomere called the??

increasing the size of the neuromuscular junction; expanding the number of synaptic vesicles (containing acetylcholine); increasing the number of acetylcholine receptors on the postsynaptic membrane

Both endurance training and resistance exercise training stimulate positive adaptations to the neuromuscular junction which include what three things?

Maximal force production (Force per unit of cross-sectional area) speed of contraction ((Vmax) Myosin ATPase activity)) efficiency of contraction (muscle fiber efficiency)

Characteristics of Muscle Fiber Types What are the three contractile properties of muscle fiber types?

Acetylcholinesterase

Degrades acetylcholine to help CEASE contraction

opening of sodium channels

During Excitation/Contraction Coupling the initiation of an action potential (AP), which provides sufficient ACh that leads to cell depolarization is due to?

slow; fast

Endurance athletes (i.e. marathoners) typically possess a high percentage of ___ muscle fibers and low percentage of ___muscle fibers

calcium; troponin

Excitation contraction coupling and relaxation: CONTRACTION 4. Depolarization of the T -tubules results in the release of ____ from the sarcoplasmic reticulum into the cytosol of the muscle fiber 5. Calcium ions bind to___ (located on actin molecules). Calcium binding to this result in a shift in the position of tropomyosin so that the myosin binding sites on the actin are exposed 6-8. Briefly, an energize myosin Cross bridge binds to the active sites on Actin and pulls the actin molecule to produce movement (i.e. fibers shortened)

acetylcholine; ligand gated; sodium

Excitation contraction coupling and relaxation: EXCITATION 1. A nerve signal arrives at the synaptic knob. 2. The synaptic vesicles release _____ that diffuses across the synaptic cleft and binds to receptors on the sarcolemma of muscle fiber. This opens ______ ion channels on the sarcolemma that result in the movement of ____ into the fiber. 3. The INWARD movement of positive ____ ions depolarize the fiber and sends a wave of depolarization through the T-tubules.

repolarized; myosin-actin cross-bridge formation

Excitation contraction coupling and relaxation: RELAXATION: 9. The first step in muscle relaxation occurs when the motor neuron stops to fire. Indeed when neural stimulation of the muscle ceases acetylcholine is no longer released in the muscle fiber is _____ 10. When the motor neuron ceases to fire and muscle excitation ceases, calcium is pumped from the cytosol into the sarcoplasmic reticulum for storage. Without free calcium in the cytosol, troponin moves tropomyosin back into position to cover the myosin binding sites on actin. This tropomyosin coverage of the active sites on actin prevents ______ and therefore muscle relaxation occurs.

depolarization- induced release of calcium from the sarcoplasmic reticulum

Excitation contraction coupling refers to the sequence of events in which the nerve impulse (action potential) depolarizes the muscle fiber, leading to muscle shortening by Cross-bridge cycling. The trigger to initiate muscle contraction is the ???

Dihydropyridine - Ryanodine Receptor complex (-Dihydropyridine receptor is a calcium channel that is voltage sensitive -Ryanodine receptor is mechanically coupled to dihydropyridine receptor and it opens with DHPR -This allows Ca++ to flow out of the SR and into the sarcoplasm) Sarcoplasmic Endoplasmic Reticulum Calcium ATPase Pump (SERCA) (-Pump embedded in membrane of SR that actively resequesters Ca++ back into SR to cease contraction)

For contraction to happen, Ca++ flows out of the sarcoplasmic reticulum and is resequesteredin order cease the contraction....how does this happen?

Testosterone

Growth Regulators Increases Satellite Cell mobilization for muscular Hypertropy/Hyperplasia

Myostatin

Growth Regulators Intramuscular protein that prevents satellite cell differentiation into myoblasts

Follistatin

Growth Regulators §Direct inhibitor of myostatin -Causes muscular growth

H zone

In the center of the sarcomere is a portion of the myosin filament with no overlap of the actin. This is called the?

a shift in the position (conformational change) of the myosin

Molecular steps leading to muscle contraction via cross- bridge cycling: 3. inorganic phosphate is released from the myosin head; this causes?

shortening; ADP

Molecular steps leading to muscle contraction via cross- bridge cycling: 4. The power stroke causes the myosin cross-bridge to pull actin inward and actin/myosin filaments slide across each other, resulting in fiber ______. Note that ____ is also released

the release of the myosin cross-bridge from actin

Molecular steps leading to muscle contraction via cross- bridge cycling: 5. A new ATP molecule binds to the myosin head; this results in?

myosin cross-bridge to return to its original orientation

Molecular steps leading to muscle contraction via cross- bridge cycling: 6. The breakdown of ATP (hydrolysis) and phosphate binds to myosin, causing ?

after

Molecular steps leading to muscle contraction via cross- bridge cycling: 2. The binding of myosin cross-bridge to actin, which occurs before or after? calcium is released from the sarcoplasmic reticulum

is not

Molecular steps leading to muscle contraction via cross- bridge cycling: Resting fiber; cross-bridge is or is not? attached to actin (i.e. calcium remains in the sarcoplasmic reticulum)

individual; neuromuscular junction; depolarize

Motor neurons extend outward from the spinal cord and innervate _____ muscle fibers. The site where the motor neuron and muscle cell meet is called the _____. Acetylcholine is the neurotransmitter that stimulates the muscle fiber to ____ which is the signal to start the contractile process

stops; calcium is pumped back into

Muscle *relaxation* occurs when the motor neurons ____ exciting muscle fiber and calcium is pumped ________ the sarcoplasmic reticulum. This removal of calcium from the cytosol causes a position change in tropomyosin, which blocks the Myerson Cross Bridge binding site on the acting molecule; this action results in muscle relaxation

binding of the myosin cross-bridge to actin; shortening

Muscular *contraction* occurs via the ???? and the repeated cycling of myosin pulling on the acting molecule resulting in the ____ of the muscle fiber

sarcomeres

Myofibrils are further subdivided into individual segments called

A band

Myosin filaments are located primarily with in the dark portion of the sarcomere which is called the

Z line (or Z disk)

Sarcomeres are divided from each other by a thin sheet of structural proteins called

fast; slow muscle type one

Successful power athletes (i.e. sprinters) generally possess a large percentage of __ muscle fibers and therefore low percentage of ___ muscle fibers

DHPR (Dihydropyridine receptor)

The _____ which is a voltage-dependent calcium channel, functions in skeletal muscle essentially as a voltage sensor, triggering intracellular calcium release for excitation-contraction coupling.

C

The binding of what to the myosin head puts the cross bridge in its high-energy conformation? A) Calcium B) Actin C) ATP

an increase in the permeability of the sarcolemma to sodium, resulting in a depolarization called the end plate potential.

The end of the motor neuron does not physically made contact with the muscle fiber but it is separated by a short gap called the synaptic cleft. When a nerve impulse reaches the end of the motor nerve the neurotransmitter acetylcholine is released and diffuses across the synaptic cleft and binds with the receptor sites on the motor end plate. This causes ????

C

The head of the myosin molecule binds to what molecule to form the cross bridge? A) Tropomyosin B) Myosin C) Actin D) Troponin

myosin ATPase activity

The key biochemical factor that regulates fiber Vmax is the ________ Therefore fibers with high myosin ATPase activities (fast fibers) possess a high Vmax whereas fibers with low myosin ATPase activities process a low Vmax (slow fibers)

store calcium ions (Ca2+)

The main function of the Sarcoplasmic reticulum is to

the number of mitochondria the number of capillaries surrounding the fibers and the mount of myoglobin within the fiber

The oxidative capacity of a muscle fiber is determined by?

shortening; actin filament over the myosin filament

The process of muscular contraction can be best explained by the sliding filaments/swinging Cross-bridge model, which proposes that muscle _____ occurs due to movement of the ?

D

The sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the A) membrane hyperpolarization B) motor end plate potential C) resting potential D) action potential E) membrane repolarization

Calcium ions binding with troponin, which shifts tropomyosin and allows the myosin-binding sites on actin to be exposed

The sliding filament theory of muscle contraction involves;

Scarcomere

The space between two Z lines constitutes the:

true

True or False: One nerve can innervate many muscle fibers, however 1 muscle fiber is only innervated by 1 nerve

1.) Energizes the power stroke of the cross bridge. 2.) Disconnects the myosin head fm the binding site on actin at the conclusion of a power stroke.3.) Actively transports calcium ions into the sarcoplasmic reticulum.

What are the 3 roles of ATP in the sliding filament theory?

C

What causes the sliding of the thin filament toward the middle of the sarcomere? A) Binding of the myosin head B) Binding of ATP to the myosin head C) Flexing of the cross bridge (power stroke)

Calcium binding.

What causes tropomyosin to move away from myosin binding sites on actin?

It blocks binding between actin and myosin.

What is the function of tropomyosin?

It binds calcium and moves the tropomyosin away from the actin.

What is the function of troponin?

A

What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges? A) Ca2+ B) myosin C) calmodulin D) troponin E) acetylcholine

Stimulates cellular contraction by opening voltage-gated ion channels

What is the role of acetylcholine in calcium release?

C

What is the role of tropomyosin in muscle contraction? A) To release troponin from tropomyosin, allowing myosin to bind to the actin filament B) To release calcium from the sarcoplasmic reticulum C) To prevent myosin from continuing to slide up the actin filament D) To aid in myosin 'cocking' on the actin filament

D

What must bind to the cross bridge for it to disconnect from the actin molecule? A) Troponin B) Tropomyosin C) Calcium D) ATP

A

What regulatory molecule on the thin filament covers the myosin head binding site on actin? A) Tropomyosin B) Troponin

D

Where does 95% of the energy needed for contraction come from during moderate exercise? A) creatine phosphate B) anaerobic glycolysis C) lactic acid D) aerobic respiration

A

Which molecule is responsible for moving the calcium back into the terminal cisternae (sarcoplasmic reticulum)? A) ATP B) Actin C) Myosin D) Troponin

B

Which molecule on the thin filament has a binding site for calcium? A) Tropomyosin B) Troponin C) Actin

E

Which of the following does NOT occur during skeletal muscle contraction? A) ATP is hydrolyzed. B) The I bands shorten and H zones disappear. C) Myosin heads bind to actin. D) Calcium concentration in the sarcoplasm increases. E) Calcium binds to myosin heads.

B

Which of the following does NOT shorten during muscle contraction? A) The sarcomere B) The thin filament (actin) C) The H zone

C

Which of the following is NOT a characteristic of skeletal muscle contraction? A) It can exert tremendous power. B) It contracts rapidly. C) It can contract for long periods of time without tiring. D) It is voluntary.

A

Which of the following is accurate regarding Type I and Type II muscle fibers? A) Type I fibers store much of their energy as triglycerides, whereas Type II fibers store energy as ATP or creatine phosphate B) Type I fibers are easily fatigued and are therefore intended for short bursts of activity C) Type I fibers employ anaerobic metabolism, whereas Type II fibers utilize aerobic metabolism D) Type I fibers are white, whereas Type II fibers are red

C

Which of the following substances increases in quantity during repetitive muscle contraction during oxygen deficit? A) oxygen B) creatine phosphate C) lactic acid D) adenosine triphosphate (ATP) E) glucose

Myogolbin

____ binds oxygen (O2 ) and also acts as a 'shuttle' mechanism for O2 between the cell membrane and the mitochondria. a high concentration of this improves the delivery of oxygen from the capillary to the mitochondria where it will be used.

DHPR (Dihydropyridine receptor); Ryanodine receptor

_____ senses the membrane potential on the T-tubule membrane and relays this to another protein, the ______, on the Sarcoplasmic reticulum membrane inside the fiber.

aerobically (require oxygen)

a large number of mitochondria provides a greater capacity to produce ATP ____ A high number of capillaries surrounding a muscle fiber ensures that the fiber will receive adequate oxygen during periods of contractile activity.

sarcomeres

a skeletal muscle fiber contains numerous myofibrils, each consisting of units called

power stroke

a stimulated myosin cross-bridge binds to the active site on actin and pulls on the actin molecule to generate movement of each cross-bridge, resulting in muscle shortening. This movement of the myosin cross-bridge pulling on the actin molecule is notably called a

myosin cross-bridges per cross sectional area

fast fibers exert more force than slow fibers because they contain more? than slow fibers

type IIx (fast-twitch or fast-glycolytic)

which fiber type has a relatively small number of mitochondria, have limited capacity for aerobic metabolism, and have less resistance to fatigue (tire out quickly) -these fibers are rich in glycolic enzymes, which provide them with a large Glycolytic (anaerobic) capacity (capacity of the fiber to make ATP WITHOUT using oxygen or the mitochondria) -this is the fastest muscle fiber in humans

type I

which fiber type has the highest Muscle capillarization (small blood vessels that supply the muscle-Ability to deliver and remove substances (such as O2) to muscle via the blood circulation)) ??

Type I (slow oxidative or slow-twitch fibers)

which fibers contain large numbers of oxidative enzymes (high mitochondrial volume) and are surrounded by more capillaries. -They possess a slower maximal shortening velocity (Vmax) and a lower myosin ATPase activity. -They contain less actin and myosin per cross-sectional area.

Type IIx

which muscle fiber holds the greatest Glycolytic (anaerobic) capacity, has the highest speed of contraction, greatest sarcoplasmic reticulum development (rate of release and resequestering of Ca2+), and highest number of fibers innervated per motor neuron

type I

which muscle fiber holds the greatest Oxidative (aerobic) capacity?

Satellite Cells

§Play role in muscle growth and repair -Increase number of nuclei §Myonuclear domain -Cytoplasm surrounding each nucleus -Each nucleus can support a limited myonuclear domain §More nuclei allow for greater protein synthesis Important for adaptations to strength training

alpha (α ) motor neurons

§Skeletal muscle is innervated by _____ that provide muscle movement §Nerves terminate on muscle fibers at the motor end plate

Acetylcholine(Ach)

•Binds to receptor on Motor End Plate to cause action potential