Midterm 1 Chapter 9

What is the difference between a tendon & a ligament?

A tendon attaches muscle to bone and a ligament attaches bone to bone.

Which of the following statements concerning skeletal muscle contraction is TRUE? A. At rest the myosin head groups are pointed toward the Z - discs/lines B. At rest tropomyosin is covering the actin binding sites on myosin C. At rest calcium ions are attached to troponin D. Both A & B E. All of the above

A. is true. B. false, at rest tropomyosin is covering the myosin binding sites on actin not myosin.

What is the neurotransmitter released by a motor neuron?

ACH - acetylcholine.

What 3 molecules make up thin filaments?

Composed of these proteins: actin, tropomyosin, and troponin.

True or false. A second class lever has the fulcrum positioned in between the effort and the resistance.

False. In second class levers Fulcrum and effort are at the opposite ends with the resistance between them.

True or false. A third class lever has the fulcrum positioned in between the effort and the resistance.

False. In third class levers Fulcrum is at one end, resistance at the other end, effort between.

True or false. In smooth muscle cells, myosin kinase phosphorylates actin.

False. Myosin kinase phosphorylates Myosin.

True or false. Thick filaments are composed of myosin & tropomyosin.

False. Thick filaments are only composed of myosin.

True or false. In skeletal muscle contraction, calcium ions bind to tropomyosin.

False. it binds to troponin.

What does the "dystrophin-glycoprotein complex" help anchor within the muscle cells?

Helps anchor the structural skeleton.

What is the sarcolemma?

Is the cell membrane of a muscle cell.

What chromosome is Duchenne's muscular dystrophy linked to?

It is an X-linked genetic disorder, caused by a mutation in the dystrophin gene. (keywords: X-linked genetic disorder)

What is the function of myosin?

Moves to initiate a contraction by binding to actin & pulling on it. Powerstroke making the sacromere shorten.

What molecule makes up thick filaments?

Myosin (protein).

What is the basic contractile unit within a muscle cell?

Sarcomere.

What are the two main filaments make up the sarcomere?

Thin and thick filaments.

True or false. A first class lever has the fulcrum positioned in between the effort and the resistance.

True.

True or false. A fixator (type of synergist) helps the prime mover work more efficiently by stabilizing the origin.

True.

True or false. A motor unit (skeleltal muscle) is defined as a motor neuron and all of the muscle fibers that it innervates.

True.

True or false. A synergist helps the prime mover work more efficiently.

True.

True or false. In a sarcomere, the Z lines/discs anchor the thin filaments.

True.

True or false. The process of phosphorylation is equivalent to "energizing" a molecule.

True.

True or false.In a smooth muscle cell, dense bodies anchor the thin filaments.

True.

True or false. In skeletal muscle contraction, acetylcholine is released by the motor neuron onto every muscle fiber that it innervates.

True. It would be a false statement if it said "to a single muscle fiber".

What are the main functions of tropomyosin?

Winds itself around the actin shaft and prevents myosin from binding with actin. It's a blocker and a regulatory molecule.

For any muscle contraction, does ATP hydrolysis "energize" or "cock back the head" of myosin.

Yes. (In skeleton muscle) In order for the muscle to relax, a fresh molecule of ATP must bind to the myosin head to release it from the actin. ATP is then hydrolyzed, providing energy to "cock" (like a gun) the head again for another round of contraction.

What is the function of T-tubules as it relates to the sarcoplasmic reticulum - SR?

are invaginations of the sarcolemma which penetrate deep into each myofiber - allow electrical signals to be carried deep into the myofiber. (keywords: electrical signals)

The dystropin gene encodes for what skeletal muscle protein?

dystrophin.

What are the main functions of actin?

forms the main shaft of the thin filament. It possesses a myosin-binding site. (Keywords: shaft, myosin binding site)

What is Duchenne's muscular dystrophy?

is a disease characterized by the weakening & deterioration of muscle.

What is Myasthenia Gravis?

is an autoimmune disease caused by antibodies that either block the nicotinic acetylcholine receptors on the skeletal muscle cells or destroy the receptors via complement fixation (killing of the cell) or through endocytosis of the receptor. (keywords: antibodies, nicotinic acetylcholine receptors)

Define a motor unit.

is defined as a motor neuron and all of the muscle fibers that it innervates.

Define epimysium.

outermost layer encircling the entire muscle.

What membranous structure surrounds individual fascicles of muscle fibers?

perimysium

Define perimysium.

surrounds fascicles (bustles of muscle cells) which are bundles of 10 to 100 individual muscle fibers (muscle cells).

Define endomysium.

surrounds individual muscle fibers.

Which of the following statements concerning the smooth muscle contraction is TRUE? A. Calcium binds to calmodulin B. Smooth muscle contraction involves the activation of myosin kinase C. At rest, the myosin binding sites on actin are exposed (i.e available for myosin to bind to) D. Both A & B E. All of the above

E. All of the Above.

What are the main functions of tropomyosin and troponin?

Tropomyosin winds itself around the actin shaft with troponin stabilizing this interaction -together these two molecules have a regulatory function = they block myosin from binding to actin except under the appropriate stimulus. Troponin is the binding site for Ca2+ (calcium). (Keywords: winds, stabilizing, regulatory, block)