Anatomy Chapter 6

Describe Isometric contractions and give an example

- Muscle filaments are trying to slide, but the muscle is pitted against an immovable object - Tension increases, but muscles do not shorten Example: pushing your palms together in front of you

Describe Isotonic contractions and give an example

- Myofilaments are able to slide past each other during contractions - The muscle shortens, and movement occurs Example: bending the knee; lifting weights, smiling

Describe Anaerobic pathway

- Reaction that breaks down glucose without oxygen - Glucose is broken down to pyruvic acid to produce about 2 ATP - Pyruvic acid is converted to lactic acid, which causes muscle soreness - This reaction is not as efficient, but it is fast - Huge amounts of glucose are needed

Describe Aerobic pathway

- Supplies ATP at rest and during light/moderate exercise - A series of metabolic pathways, called oxidative phosphorylation, use oxygen and occur in the mitochondria - Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP) - This is a slower reaction that requires continuous delivery of oxygen and nutrients

What are the characteristics of skeletal muscle?

- attached to the skeleton - long cylindrical cells - multinucleate - have striations - voluntary control - fast to slow - not rhythmic

What are the characteristics of cardiac muscle?

- found in the heart - branching cells - uninucleate - have striations - involuntary control (pacemaker) - slow - rhythmic

What are the characteristics of smooth muscle?

- in the walls of hollow organs - fusiform cells - uninucleate - no striations - involuntary control - very slow - rhythmic sometimes

Describe direct phosphorylation

- muscle cells store CP - after ATP is depleted, ADP remains - CP transfers a phosphate group to ADP to regenerate ATP - CP supplies are exhausted in less than 15 seconds - 1 ATP is produced per CP molecule

What are the structures of the skeletal muscle from largest to smallest?

1. Fascicle 3. Muscle fiber (cell) 4. Myofibril 5. Myofilament 6. Sarcomere

What are the three main functions of the muscular system?

1. maintain posture and body position 2. stabilize joints 3. generate heat

What are the three basic types of muscle found in the body?

1. skeletal 2. cardiac 3. smooth

According to the sliding filament theory, how does muscle contraction occur? A) Myosin heads form cross bridges and pull thin filaments, causing them to slide. B) Both thick and thin filaments shorten as the muscle contracts. C) A bands bunch up and shorten as myosin heads attach to thin filaments. D) Myosin heads attach and detach from thin filaments, causing thin filaments to shorten.

A

Contractions in which muscles shorten and produce movement are known as ________. A) isotonic contractions B) twitches C) isometric contractions D) resistance exercises

A

The plasma membrane of a skeletal muscle cell is called the ________. A) sarcolemma B) sarcomere C) myofilament D) sarcoplasm

A

Which one of the following is composed mostly of the protein myosin? A) thick filaments B) thin filaments C) all myofilaments D) Z discs

A

- Movement of a limb away from the midline

Abduction

- Opposite of abduction - Movement of a limb toward the midline

Adduction

A sarcomere is ________. A) the nonfunctional unit of skeletal muscle B) the contractile unit between two Z discs C) the area between two intercalated discs D) the wavy lines on the cell, as seen in a microscope

B

During skeletal muscle contraction, to what do myosin heads bind? A) myosin filaments B) actin filaments C) Z discs D) thick filaments E) the H zone

B

One neuron and all the skeletal muscles it stimulates is known as a ________. A) sarcoplasmic reticulum B) motor unit C) synaptic cleft D) neuromuscular junction

B

What is the unstoppable electrical current that travels down the length of the entire surface of a sarcolemma? A) neuromuscular junction B) action potential C) neurotransmitter D) acetylcholine

B

Anaerobic glycolysis requires ________ to make ATP. A) creatine phosphate only B) oxygen only C) glucose only D) both oxygen and glucose

C

Muscle tissue has the ability to shorten when adequately stimulated, a characteristic known as ________. A) elasticity B) irritability C) contractility D) extensibility

C

The heads of the myosin myofilaments are called ________ when they link the thick and thin filaments together during skeletal muscle contraction. A) neuromuscular junctions B) synapses C) cross bridges D) motor units

C

What creates the alternating light and dark bands that provides the striation pattern on skeletal muscle tissue? A) sarcoplasm and sarcolemma B) thick filaments and myosin heads C) A bands and I bands D) H zones and M lines

C

What is covered by the endomysium? A) fascicles of muscle cells B) an entire muscle C) an individual muscle cell D) myofibrils E) smooth muscle only

C

Why are calcium ions necessary for skeletal muscle contraction? A) Calcium ions increase the speed of the action potential transmitted along the sarcolemma. B) Calcium ions release the inhibition on Z discs. C) Calcium ions trigger the binding of myosin heads to actin filaments. D) Calcium ions cause ATP binding to actin. E) Calcium ions bind to regulatory proteins on the myosin filaments, changing both their shape and their position on the thick filaments.

C

Why are calcium ions necessary for skeletal muscle contraction?

Calcium triggers the binding of myosin to actin

- Combination of flexion, extension, abduction, and adduction - Common in ball-and-socket joints - Proximal end of bone is stationary, and distal end moves in a circle

Circumduction

-Turning sole of foot medially

Inversion

- Moving the thumb to touch the tips of other fingers on the same hand

Opposition

- Pointing the toes away from the head

Plantar flexion

- Forearm rotates medially so palm faces posteriorly - Radius and ulna cross each other like an X

Pronation

- Movement of a bone around its longitudinal axis - Common in ball-and-socket joints - Example: moving the atlas around the dens of axis (i.e., shaking your head "no")

Rotation

- Forearm rotates laterally so palm faces anteriorly - Radius and ulna are parallel

Supination

Creatine phosphate (CP) functions within the muscle cells by ________. A) forming a temporary chemical compound with myosin B) forming a chemical compound with actin C) inducing a conformational change in the myofilaments D) storing energy that will be transferred to ADP to resynthesize ATP as needed E) storing energy that will be transferred to ATP to resynthesize ADP as needed

D

Striated involuntary muscle tissue found in the heart is ________. A) smooth muscle B) skeletal muscle C) dense regular D) cardiac muscle

D

What is released by axon terminals into the synaptic cleft to stimulate a muscle to contract? A) potassium ions B) actin C) sodium ions D) acetylcholine E) myosin heads

D

What must rush into a muscle cell to promote its depolarization? A) potassium ions B) calcium ions C) acetylcholine D) sodium ions E) acetylcholinesterase

D

What organelle wraps and surrounds the myofibril and stores calcium? A) cross bridge B) sarcomere C) sarcolemma D) sarcoplasmic reticulum

D

Which of the following is NOT a function of the muscular system? A) production of movement B) maintenance of posture C) stabilization of joints D) blood cell formation

D

- Lifting the foot so that the superior surface approaches the shin (toward the dorsum)

Dorsiflexion

- Turning sole of foot laterally

Eversion

- Opposite of flexion - Increases angle between two bones - Typical of straightening the elbow or knee - Extension beyond 180º is hyperextension

Extension

- Decreases the angle of the joint - Brings two bones closer together - Typical of bending hinge joints (e.g., knee and elbow) or ball-and-socket joints (e.g., the hip)

Flexion