Chapter 1: Structure and Function of Body Systems

Question 1

Axial Skeleton

Answer 1

Skull
Vertebral Column (C1-Coccyx)
Ribs
Sternum

Question 2

Appendicular Skeleton

Answer 2

Shoulder Girdle
Pelvic Girdle (L/R coxal or innominate bones)
Bones of Extremities
Joints

Question 3

Types of Joints

Answer 3

Fibrous
Cartilaginous
Synovial

Question 4

Fibrous Joints

Answer 4

visually no movement

e.g. sutures of skull

Question 5

Cartilaginous Joints

Answer 5

allow limited movement

e.g. intervertebral disks

Question 6

Synovial Joints

Answer 6

allow considerable movement

e.g. elbow and knee

Question 7

Uniaxial Joints

Answer 7

virtually allows movement along one axis, like a hinge

e.g. elbow and knee

Question 8

Biaxial Joints

Answer 8

allow movements about two perpendicular axes.

e.g. ankle and wrist

Question 9

Multiaxial Joints

Answer 9

allow for movement about all three axes

e.g. hip and shoulder ball-and-socket joints

Question 10

Spinal Vertebrae

Answer 10

7 cervical (neck)
12 thoracic (mid-upper back)
5 lumbar (low back)
5 sacral (coccygeal)

Question 11

Connective Tissues

Answer 11

Epimysium (outer)
Perimysium (fascicles, or group of fibers)
Endomysium (individual fibers)

Question 12

Limb muscle attachment distances

Answer 12

Proximal (closer to trunk)

Distal (further from trunk)

Question 13

Neuromuscular Junction (motor end plate)

Answer 13

junction between motor neuron (nerve cell) and the muscle fiber it innervates

Question 14

Motor Unit

Answer 14

motor neuron and the muscle fiber it innervates

Question 15

Sarcoplasm

Answer 15

Cytoplasm of a muscle fiber, contains contractile components consisting of protein filaments, other proteins, stored glycogen and fat particles, enzymes, and specialized organelles such as mitochondria and the sarcoplasmic reticulum.

Question 16

Myofibrils

Answer 16

~1mm in diameter.
Hundreds dominate sarcoplasm.
Contain contractile apparatuses (myofilament): Myosin and Actin

Question 17

Myosin and Actin Filaments

Answer 17

Myosin (thick) and Actin (thin).

Organized longitudinally in sarcomeres.

Question 18

Discharge of an AP from a…

Answer 18

motor nerve signals the release of Ca from the SR into the myofibril, causing tension development in the muscle.

Question 19

Sliding Filament Theory

Answer 19

States that the Actin filaments on each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere, thus shortening the muscle fiber (aka muscle contraction).

Question 20

Phases of a Muscle Contraction

Answer 20

Resting
Excitation-Contraction Coupling
Contraction
Recharge
Relaxation

Question 21

Resting Phase of Muscle Contraction

Answer 21

Little Ca present in myofibril (most stored in SR) so very few myosin cross bridges are bond to actin.

Question 22

Excitation-Contraction Coupling Phase

Answer 22

SR is stimulated to release Ca ions.
Ca bonds with troponin (protein situated along actin).
Shift occurs to tropomyosin (another protein along actin).
Myosin cross bridges now attach more rapidly to actin filament.

Question 23

Contraction Phase

Answer 23

Power stroke (energy for pulling actin) comes from hydrolysis (breakdown due to reaction with water) of ATP to ADP + Phosphate (P).

Question 24

Recharge Phase

Answer 24

Occurs as long as Ca in available in myofibril, ATP is available to assist uncoupling myosin from actin, and sufficient active myosin ATPase is available for catalyzing (accelerating) the breakdown of ATP.

Question 25

Relaxation Phase

Answer 25

Occurs when stimulation of motor nerve stops.

Ca is pumped back into SR, which prevents link of myosin to actin filaments.

Question 26

Contraction of a Myofibril

Answer 26

In stretched muscle I-band and H-zone is elongated, and there is low force potential due to reduced cross bridge actin alignment.
When muscle contracts, I-band and H-zone are shortened.
With completely contracted muscle, there is low force potential due to reduced cross-bridge actin alignment.

Question 27

Step 1 of Muscle Contraction (5)

Answer 27

ATP splits (by myosin ATPase) causes myosin head to in energized state, allowing it to move into position to form bond with actin.

Question 28

Step 2 of Muscle Contraction

Answer 28

Release of Phosphate from the ATP splitting process then causes myosin head to change shape and shift.

Question 29

Step 3 of Muscle Contraction

Answer 29

Actin is pulled toward center of sarcomere and is referred to as Power Stroke; ADP is released.

Question 30

Step 4 of Muscle Contraction

Answer 30

After Power Stroke has occurred, myosin head detaches from actin but only after another ATP binds to myosin head b/c the binding process facilitates detachment.

Question 31

Step 5 of Muscle Contraction

Answer 31

The myosin head is now ready to bind to another actin (Step 1), and the cycle continues as long as ATP and ATPase are present and Ca is bound to the troponin.

Question 32

Activation of Muscles

Answer 32

Arrival of AP as nerve terminal causes release of acetylcholine. Once sufficient amount if acetylcholine its released, and AP is generated across sarcolemma, and the fiber contracts.

Question 33

Extent of muscle control depends on number of muscle fibers within each motor unit. Great and Less precision?

Answer 33

Greater precision: few as one muscle fiber per motor neuron.

Less precision: may have several hundred fibers served by one motor neuron.

Question 34

All-or-none Principle

Answer 34

All of the muscle fibers in the motor unit contract and develop force at the same time. There is no such thing as a motor neuron stimulus that causes only some of the fibers to contact. Similarly, a stronger AP cannot produce a stronger contraction.

Question 35

Twitch

Answer 35

Brief contraction caused by each AP traveling down motor neuron, causing a short period of muscle fiber activation within motor unit.

Question 36

Second Twitch

Answer 36

If a second twitch is elicited from motor nerve before fibers completely relax, force from the two twitches summates, and the resulting force is greater than that produced by a single twitch.

Question 37

Decreased time between twitches results in?

Answer 37

Greater summation of cross-bridge binding and force.

Question 38

Tetanus

Answer 38

Maximal amount of force the motor unit can develop.

Question 39

Muscle Fiber Types

Answer 39

Type I (slow-twitch)
Type IIa (fast-twitch)
Type Iix (fast-twitch)

Question 40

Type I Muscle Fiber

Answer 40

Efficient and fatigue resistant, high capacity for aerobic energy supply, but have limited potential for rapid force development, as characterized by low myosin ATPase activity and low anaerobic power.

Question 41

Type IIa Muscle Fibers

Answer 41

Inefficient and fatiguable and have low aerobic power, rapid force development, high myosin ATPase activity, and high anaerobic power.

Question 42

Type IIx Muscle Fibers

Answer 42

Show less resistance to fatigue than Type IIa.