Skeletal Muscle Lecture

What causes the myosin head to disconnect from actin?

ATP binding

Mitochondria and glycogen break down into glucose for

ATP for muscle to contract and shorten

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

Acetylcholine

The binding of the neurotransmitter to receptors on the motor end plate causes what to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.

Skeletal muscle contract when stimulated by

CNS

Upon death, circulation ceases, depriving skeletal muscles of nutrients and oxygen. Within a few hours, skeletal muscle fibers run out of ATP. Without ATP, the cross-bridges cannot detach from the active sites, and all of the body's muscles lock in a contracted position called rigor mortis. What crucial ion must bind to troponin in order for actin and myosin to form a cross bridge?

Calcium Ions

order of skeletal muscle structural organization

Epimysium, Endomysium, perimysium (fasicle), myofibirl

Myogram

a chart of the timing and strength of a muscle's contraction

Any presence of CA+ is the beginning of...

a muscle contraction

Froms tendon or aponeurosis filled with collagen fibers

epimysium, perimysium, Endomysium. Both provide passageway for BV and Nerves for muscle fiber function.

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

What is the name of the specialized attachment sites containing gap junctions and desmosomes found in cardiac cells?

intercalated discs

Actin has active sites to interact with...

myosin heads for contraction

Cross bridges

myosin heads interacting with actin active sites.

What is the name of the serous membrane that lines the abdominopelvic cavity?

peritoneum

Sarcolemma

plasma membrane of a muscle fiber, surround sarcoplasm

slow twitch muscle fibers

red muscle fibers that are fatigue resistant slow contraction speed lower capacity for tension endurance activities

What causes the power stroke?

release of ADP and Pi (the hydrolysis of ATP provides the energy for the power stroke. Energy is transferred from ATP to the myosin head.)

How is acetylcholine (ACh) removed from the synaptic cleft?

simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)

Twitch

single stimulus-contraction-relaxation sequence in a muscle fiber

What is an Isometric Contraction?

tension develops, but there is no change in the length of the muscle. (Keeps us upright)

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisterns (cisternae) of the sarcoplasmic reticulum

Aerobic Endurance

the length of time a muscle can continue to contract while supported by mitochondrial activities

Anaerobic Endurance

the length of time muscle contractions can be supported by glycolysis

Contraction Cycle

1) CA+ bond to troponin, expose active site 2) Myosin heads attach to actin sites 3) Head pivots toward m-line 4)ATP bonds to head of myosin and breaks cross-bridge

neuromuscular junction (NMJ)

1) Cytoplasm of axon have vesicles with ACh (Neurotransmitter), AChE in synaptic cleft breaks ACh down 2) ACh stimuli, arrival of electrical impulse.(Action potential to NMJ) 3) Exoxytosis of ACh 4) NA+ come into cytosol 5) AChE breaks down ACh

Aerobic respiration

95% of ATP Relied on when skeletal muscles resting 32-38 ATP

How do we maintain posture and body position?

Continuous muscular contractions, especially through Isometric Contractions (keep us upright, stabalize vertebrae)

Latent Period

Contraction has yet to begin, CA+ releases by Sarcoplasmic Reticulum

What is the action of the diaphragm?

Contraction of the diaphragm expands thoracic cavity and compresses abdominopelvic cavity.

Tropomyosin (protein)

Covers thin actin when muscle is resting

Any condition that interferes with the generation of an action potential in the sarcolemma will cause muscular paralysis. Two examples worth noting are Botulism and Myasthenia Gravis. Botulism is a disease that results from the consumption of foods contaminated with a bacterial toxin that prevents the release of ACh at the axon terminals, leading to a severe, potentially fatal, muscular paralysis. The progressive muscular paralysis seen in the autoimmune disease myasthenia gravis results from the loss of ACh receptors at the motor end plate. What is the name of the enzyme that normally breaks down Ach in the neuromuscular junction?

Acetylcholinesterase

Thin Filament

Actin

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

Action Potential

What is Tension?

Active force created when muscles contract

Another way Calcium gets into muscle

Active transport into terminal cisternae or Sarcoplasmic Reticulum CA+ ions pumped across plasma membrane

Contracting Sacromere

I band shorten, Z line move closer, H band decrease, Zones of overlap bigger

Glycolysis

Anaerobic. Glucose breaks down, ATP yields low. Last longer. 2ATP Lactic Acid

What is Lactic Acid

C3H6O3 and it causes your muscles to burn during hard exercise

Contraction (Myosin head and actin)

CA+ binds to troponin. (From terminal cisternae of Sarcoplasmic Reticulum) Troponin changes position and move tropomyosin away from Actin active sites for myosin head to attach to action.

Danger of Creatine?

Can be dangerous is taken too many supplements, toxins can not get out of the liver, or kidneys because water gets trapped in muscle. Better with resistance. Water will only move out when you quit creatine supplements

Tetanus

Clostridium tetani bacteria Survive in low O2 fibers (slow twitch) Affect Central NS Result in powerful contractions 40-60% mortality rate

Tension produced as a whole determined by

Frequency of stimulation, # of muscle fibers

Action Potential

In T-Tubules triggers massive release of CA+ from terminal cisternae

Sacromere

Myofilaments actin and myosin

Thick Filament

Myosin

Blood vessels ensure

O2 supply for nutrients and carry metabolite waste created by active muscle away from muscle.

O2 Debit

Oxygen that is required during exercise recovery

How does the muscular system move the skeleton?

Pulling on tendons results in moving the bones

Compression

Push applied to object and forces object away

Myoglobin

Reddish brown protein in sarcoplasm (Cytoplasm) Stores O2 for ATP to contract and not fatigue as quick

Tension varied by

Resting length, frequency of stimulation.

Relax Phase

Resting levels CA+ drops Active sites cover with tropomyosin Cross-bridge decline

Sarcoplasmic Reticulum

Special SMOOTH ER. bound to T-Tubules Terminal Cisternae Expanded chambers of tubules encircling a myofibril

Axons penetrate the epimysium, branch through the perimysium and enter the endomysium to innervate m fibers (T or F)

T

Openings in sarcolemma

T-tubules form passageways for nerve impulses and allow muscle fibers to contract all at same time

Resistance

Tension must overcome resistance, affected by object, shape, weight, friction.

Contraction Phase

Tension peaks cross bridge interact with actin active sites

What is Creatine?

The 15 second burst of energy you have for sprinting.

What is an Isotonic Contraction?

Where tension/load on muscle is constant, length can change. EX. Walking, running, lifting objects.

What is Recruitment?

Where you use more and more motor units to help lift something.

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

Troponin

Are some motor units always active?

Yes, but not enough Tension applied to cause movement.

A myosin head binds to which molecule to form a cross bridge?

actin

Drugs are commonly injected into tissues rather than directly into the bloodstream. This method makes it possible to introduce a large amount of a drug at one treatment, yet have it enter the circulation gradually. An intramuscular (IM) injection introduces the drug into the mass of a large skeletal muscle. Bulky muscles, like the gluteus maximus and deltoid muscles that contain few large vessels or nerves make ideal injection sites. The vastus lateralis muscle is another common injection site. The vastus lateralis belongs to the quadriceps group. What is the principle action of the vastus lateralis and the other quadriceps muscles?

extension of the knee

Troponin

holds tropomyosin in place on actin

Unlike skeletal muscle tissue, smooth muscle tissue __________.

is involuntary, lacks sarcomeres, and is not striated

How is creatine made?

made by excess ATP loosing its phosphate(ADP)

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels

fast twitch muscle fibers

white muscle fibers that contract rapidly and forcefully but fatigue quickly actions requiring strength, power, or speed Glycolysis (Anaerobic)