Chapter 9 Muscular System Part 2

During muscle relaxation

Ca+2 ions are stored in SR Troponin-tropomyosin complexes cover binding sites on actin filaments

Myasthenia Gravis (MG) treatments

Drugs that inhibit acetylcholinesterase, Immunosuppressant drugs, Administering antibodies that inactivate harmful antibodies, Plasma exchange

which muscle group is composed of mainly slow-twitch (type i) fibers

Erector spinae muscles of the back

A lever has four basic components:

a rigid bar or rod, a fulcrum or pivot, an object that is moved against resistance, and a force that supplies energy

Must generate _______ __________ in sarcolemma for activation _at neuromuscular junction)

action potential

cross bridge cycle continues as long as Ca2+ and _________ ___are present

adequate ATP

Myasthenia Gravis (MG)

an autoimmune disorder; antibodies attack Acetylcholine receptors on skeletal muscle fibers; leads to widespread muscle weakness and muscle fatigue

which equation best describes how the muscle cell can replenish ATP when ATP levels are low?

creatine phosphate + ADP --> creatine + ATP

which muscle is the prime mover of shoulder abduction (abduction of the arm)

deltoid, Supraspinatus, teres minor, infraspinatus, trapezius, latissimus dorsi, levator scapula, teres major, rhomboid major

the figure shows two _____ each consisting of one _______ and all muscle fibers with which it synapses

motor units, motor neuron

Which type of muscle is most likely found in the walls of large blood vessels?

multiunit smooth muscle

Place in order from largest to smallest the components of a skeletal muscle.

muscle, fascicle, muscle fiber, myofibril, filaments

third-class-levers

resistance-force-fulcrum (tweezers)

first-class levers

resistance-fulcrum-force (scissors)

Relaxation

when a muscle returns to its original form

action potential caused by changes in electrical charges

Depolarization, Repolarization

TRUE

(TRUE or FALSE) The following sentences are placed in order, starting with the muscle that is most superficial and ending with the deepest layer:- 1)The fibers of the external oblique run down and forward from the lower ribs to the pelvic girdle and linea alba. 2) The fibers of the internal oblique run up and forward from the pelvic girdle to the lower ribs. 3) The fibers of the transversus abdominis run horizontally.

When neural stimulation of muscle fiber stops

-Acetylcholinesterase (enzyme) rapidly decomposes ACh remaining in the synapse -Muscle impulse stops when ACh is decomposed -Stimulus to sarcolemma and muscle fiber membrane ceases -Calcium pump moves Ca+2 back into sarcoplasmic reticulum (SR) -Troponin-tropomyosin complex again covers binding sites on actin -Myosin and actin binding are now prevented -Muscle fiber relaxes

cross bridge cycling

-Myosin head attaches to actin binding site, forming cross-bridge -Myosin cross-bridge pulls thin filament toward center of sarcomere -ADP and phosphate are released from myosin -New ATP binds to myosin -Linkage between actin and myosin cross-bridge break -ATP splits -Myosin cross-bridge goes back to original position

Place the steps of muscle fiber contraction in the correct sequence.

1) a nerve impulse arrives at the distal end of a motor neuron 2) ACh is released into synaptic cleft 3) ACh binds to receptors on the motor end plate 4) an electrical impulse travels across the sarcolemma and into transverse tubules 5) the impulse causes calcium channels to open in the sarcoplasmic reticulum 6) calcium ions diffuse out of sarcoplasmic reticulum and bind to troponin 7) tropomyosin molecules move to expose binding sites on actin 8) the myosin heads link to the active sites on actin 9) thin filaments are pulled toward the center of the sarcomere by myosin 10) the muscle fiber shortens as a contraction occurs

Place the steps of muscle relaxation in order.

1) nerve impulses no longer arrive at neuromuscular junction 2) acetylcholine is no longer released 3) acetylcholinesterase breaks down ACh and the muscle fiber is no longer stimulated 4) calcium ions are actively transported from sarcoplasm into the sarcoplasmic reticulum 5) troponin and tropomyosin shift blocking further interaction between myosin and actin 6) muscle fiber relaxes

place in order the sources of ATP used as an exercise bout continues

1) use of ATP molecules present in the cytoplasm 2) use of creatine phosphate as a means to convert ADP to ATP 3) production of ATP via anaerobic metabolism 4) production of ATP via aerobic metabolism

Starting with the most proximal insertion (on the pubic symphysis) muscles placed in order based on the proximity of their insertion to the axial skeleton.

1)Rectus Abdominis 2)Gluteus medius 3)iliopsoas 4)adductor longus 5)adductor magnus 6)Biceps femoris 7)soleus 8)fibularis longus 9)Flexor digitorum longus

steps in EC coupling

1)The action potential (AP) propagates along the sarcolemma and down the T tubules 2)Calcium ions are released 3)Calcium binds to troponin and removes the blocking action of tropomyosin. When Ca2+ binds, troponin changes shape, exposing binding sites for myosin (active sites) on the thin filaments 4)Contraction begins: Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins. At this point, E-C coupling is over

Starting with the most proximal insertion muscles placed in order based on the proximity of their insertions to the axial skeleton.

1. Pectoralis minor 2 supraspinatus 3 pectoralis major 4 Deltoid 5 Brachialis 6 Biceps brachii 7 pronator teres 8 brachioradialis 9 Flexi carpi ulnaris 10 Flexor digitorum superficialis

Rigor mortis

3-4 hours after death muscles begin to stiffen with weak rigidity at 12 hours post mortem (Dying cells take in calcium cross bridge formation, No ATP generated to break cross bridges)

For skeletal muscles to contract

Activation (at neuromuscular junction), Excitation-contraction coupling

Cellular respiration

Anaerobic Phase:• Glycolysis.• Occurs in cytoplasm.• Produces little A T P.

Compare the characteristics of skeletal and smooth muscle fiber contractions

Both smooth and skeletal muscle contractions involve the reactions of actin and myosin, are triggered by membrane impulses and the release of calcium ions, and use energy from ATP molecules. The differences between their contractions are: a. Skeletal muscles use acetylcholine as the neurotransmitter. Smooth muscle uses acetylcholine and norepinephrine as its neurotransmitters. b. Several hormones that cause either contractions or alter the amount of response to the neurotransmitters affect smooth muscles. c. Smooth muscle is slower to contract and relax than skeletal muscle. However, smooth muscle can maintain a forceful contraction for a longer period of time with a given amount of ATP. d. Unlike skeletal muscle, smooth muscle fibers can change length without changes in tautness. As a result, as the hollow organs become filled, the muscles can stretch without internal pressure changing.

Excitation-Contraction Coupling

Connection between muscle fiber stimulation and muscle contraction

Distinguish between multiunit smooth muscle and visceral smooth muscle

Multiunit smooth muscle features fibers that are somewhat disorganized and occur as separate fibers rather than in sheets. It can be found in the iris of the eyes and in the walls of blood vessels. Multiunit smooth muscle tissue contracts only after stimulation by motor nerve impulses. Visceral smooth muscle is composed of sheets of spindle-shaped cells in close contact with one another. This type, which is more common, is found in the walls of hollow, visceral organs such as the stomach, intestines, urinary bladder, and uterus. The fibers of visceral smooth muscle are capable of stimulating each other. So, when one fiber is stimulated, the impulse may excite adjacent fibers that, in turn, may excite others. Visceral smooth muscle fibers also display rhythmicity—a pattern of repeated contractions. These two features of visceral smooth muscle are largely responsible for peristalsis.

Upon muscle stimulation

Muscle impulses cause SR to release Ca+2 ions into cytosol Ca+2 ion binds to troponin to change its shape The position of tropomyosin is altered Binding sites on actin are now exposed Myosin heads bind to actin, forming cross-bridges

Compare the contraction mechanisms of skeletal and cardiac muscle cells

Skeletal muscle can contract individually. Cardiac muscle works in a network. When one portion of the cardiac muscle network is stimulated, the impulse travels to the other fibers in the network. It then contracts as a unit. It is self-exciting and rhythmic, and the entire network responds in an all-or-none manner. Cardiac muscle occurs only in the heart. It is made of striated muscle fibers joined end-to-end, forming three-dimensional networks. The internal components are the same, except that the cisternae of the cardiac fibers are not as well developed and contain fewer calcium ions than skeletal muscle fibers. The T-tubules of the cardiac muscle fibers are more developed and release more calcium ions, which comes from the extracellular fluid, in response to stimuli. This enables the cardiac muscle fibers to maintain contractions for a longer period of time. The cardiac muscle cells are joined to each other at the ends by means of intercalated disks. These disks help hold adjacent cells together and transmit the force of the contraction from cell to cell. The disks are also low in electrical resistance, so the muscle impulse travels from cell to cell rapidly. Cardiac muscle is self-exciting, rhythmic, and the entire network responds in an all-or-none manner.

depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

The following layers are associated with skeletal muscles. Place them in order from superficial to deep.

fascia, epimysium, perimysium, endomysium, sarcolemma, fascicle

second-class levers

fulcrum-resistance-force (wheelbarrow)