Pool Questions 3

Question 1

This type of growth involves division of chondrocytes, secretion of new matrix, and the expansion of cartilage from within.

Answer 1

Interstitial Growth; typically cartilage growth ends during adolescence when the skeleton stops growing.

Question 2

This type of joint is held together by very short, interconnecting fibers, and the bone edges interlock.

Answer 2

Suture joints; found only in the skull

Question 3

Define sarcomere.

Answer 3

A sarcomere is a “muscle segment”, or the region of a myofibril between two successive Z discs. About 2 micrometers long and the smallest contractile unit of a muscle fiber.

Question 4

Briefly summarize the mechanisms of excitation-contraction coupling

Answer 4

1. Action potential propagates along the sarcolemma and down the T tubules
2. The action potential causes the T tubules to change shape. Consequently, this opens calcium channels of the sarcoplasmic reticulum, allowing Ca(2+) to flow into the cytosol.
3. The calcium ions then bind to troponin C and remove the blocking action of tropomyosin. When calcium ions bind, the troponin C protein changes shape, thus exposing binding sites for myosin on the thin actin filaments.
4. Myosin binding to actin form cross bridges and contraction then begins. At this point, Excitation-Contraction coupling is considered complete.

Question 5

Energy for the sliding-filament model of muscular contraction is provided by__________

Answer 5

ATP hydrolysis causes ATP to ADP, causing change in affinity

Question 6

____ wraps each fiber; _____ surrounds several fibers; ____ surrounds all the bundles to form the muscle

Answer 6

1. Endomysium
2. Perimysium
3. Epimysium

Question 7

What stores, releases, and reabsorbs Ca2+ for muscular contraction?

Answer 7

Cisternea found in the sarcoplasmic reticulum

Question 8

Synarthrotic joints are: _____ Ampiarthrotic are ____;Diarthrotic are_____

Answer 8

1. Immovable joints
2. Slightly moveable joints
3. Freely moving joints

Question 9

Why does the body break down bone when a person is in space?

Answer 9

In space there are relatively no “demands” placed on the bone due to the lack of gravity. With no “demands” (weight bearing) on the bone, the ratio of osteoblasts and osteoclasts is thrown off from what it is on Earth, leaving more osteoclasts breaking down the bones. As a result, calcium in bones leaches out, leaving the bones weaker.

Question 10

What does the epiphyseal plate allow?

Answer 10

Between the diaphysis and each epiphysis of an adult long bone is an epiphyseal line, a remnant of the epiphyseal plate, which is a disc of hyaline cartilage that grows during childhood to lengthen the bone

Question 11

T/F Articular cartilage is fibrocartilage

Answer 11

False; Articular cartilage is a type of hyaline cartilage that covers the ends of long bones, providing springy pads that absorb compression at joints

Question 12

T/F Hyaline cartilage within the body will maintain the hydration levels throughout a persons’ life.

Answer 12

False; When dehydrated areas of the body that are not important for survival are deprived of water in order to supply the brain and other vital organs with water. Because cartilage is not a vital organ the body begins to pull water out of it, dehydrating it. When the water content of cartilage drops it begins to lose it’s smooth, low-friction, and wear-resistant qualities allowing it to be damaged. This will cause joint pain in the dehydrated individual.

Question 13

Why do menopausal women tend to break their hips more often?

Answer 13

Estrogen helps preserve calcium in the body and prevent bone breakdown, so when estrogen levels decrease during menopause the bone becomes weaker and the breakdown of bone (by osteoclasts) outpaces the building/remodeling of bones (by osteoblasts).

Question 14

What area of the femur is at a greater risk of fracture when a person is suffering from osteoporosis?

Answer 14

The femoral neck, which is located near the top of the femur bone, is especially susceptible to fractures due to osteoporosis because it is the weakest part of the femur.

Question 15

How does bone repair begin?

Answer 15

1. hematoma forms
2. fibrocartilaginous callus forms
3. bony callus forms
4. bone remodeling occurs

Question 16

What types of joints are within the body?

Answer 16

Cartilaginous, fibrous, synovial

Question 17

What are general descriptions for the joint types?

Answer 17

1. Cartilaginous - joined by cartilage, no joint cavity, little movement (amphiarthrotic)
   synchondroses and symphyses
2. Fibrosis - joined by collagen fibers, no joint cavity, mostly immovable (mostly synarthrotic)
   sutures, syndesmoses, and gomphoses
3. Synovial - joints separated by fluid filled cavity, allows for freedom of movement (diarthrotic)
   most joints of the body fall in the synovial class (plane, hinge, pivot, condylar, saddle, ball-and-socket)

Question 18

What function do bursae accomplish?

Answer 18

Reduce friction

Question 19

In the shoulder a bursa is located appropriately to prevent what from occurring?

Answer 19

It prevents the ligament from rubbing against the bone

Question 20

What is bursitis?

Answer 20

The inflammation and swelling of a bursa

Question 21

What is a tendon sheath?

Answer 21

1. Layer of membrane around a tendon that allows the tendon to move
2. Elongated bursa that wraps completely around a tendon subjected to friction. Common where several tendons are crowded together (i.e. wrist region)

Question 22

T/F Muscle has a single nucleus similar to other cells within the body.

Answer 22

False.

Muscle fibers are long, slender, and multinucleated

Question 23

When a single muscle cell is stimulated, will the tendon register the activation of the fiber?

Answer 23

Yes, the stimulation of one muscle cell can be felt by the tendon.

Question 24

What is the weakest area of muscle?

Answer 24

“musculotendinous junction” - where the muscle attaches to the tendon

Question 25

What are the three types of lever systems in the body?

Answer 25

1. 1st Class - the axis (fulcrum) is located between the weight and the force
   i. e. joint between the head and first vertebra
2. 2nd Class - the weight is between the axis and the force
   i. e. lower leg standing on tiptoes
3. 3rd Class - the force is applied between weight and axis. 3rd Class is the most common level system in the human body, least efficient, has the greatest range of motion
   i. e. flexion at the elbow

Question 26

T/F The 2nd class lever is the most efficient lever system.

Answer 26

False; 1st class is

Question 27

How does unipennate orientated muscle affect force production of the muscle?

Answer 27

Unipennated fibers lose up to 13% of force because force production is directly related to the angle of the muscle fiber. (30 degree angle also, if you want to show off when you answer the question)
Greater the angle of pennation → smaller the force being transmitted to the tendon

Question 28

What is the advantage of pennated muscle with regard to muscle shortening speed?

Answer 28

Pennated muscle causes the shortening speed at the tendon to be faster
Pennate muscle allows for higher force production but smaller range of motion
The pennation angle increases when the muscle contracts

Question 29

How are adhesion molecules within skeletal muscle important?

Answer 29

Keeps the muscle together
Cell adhesion molecules (CAMs) are proteins located on the cell surface involved in binding with other cells and with the extracellular matrix (ECM) in the process called cell adhesion.
CAMs are essential in maintaining a multicellular environment (such as skeletal muscle)

Question 30

What is the advantage of varying motor neurons within a single muscle?

Answer 30

Able to recruit more motor neurons to perform a task (such as a heavy lift)
Muscles which possess more motor neurons are able to control force output more finely.
Each muscle fiber is innervated by multiple neurons, including excitatory and inhibitory neurons and the force of contraction of muscles is regulated by how many motor neurons are activated, and the balance between excitatory and inhibitory signals.

Question 31

T/F The eye and hand are examples of large motor neurons which control a large number of muscle fibers.

Answer 31

False; the eye only has 5 muscle fibers

Question 32

Why does the blood supply vary to the skeletal muscle?

Answer 32

Blood flow varies depending on the demands placed on the muscle (contracting or at rest).
During exercise (muscular contraction) skeletal muscle needs more oxygen, so blood flow is increased in order to deliver more oxygen to the muscles involved (blood is what carries oxygen throughout the body).
When at rest the muscles do not need as much oxygen and thus do not need the increased blood flow.

Question 33

When an axon terminates on a muscle fiber, what is formed between the axon and muscle fiber?

Answer 33

A synaptic cleft

Question 34

What neurotransmitter is released by the nerve on the muscle fiber?

Answer 34

ACh (acetylcholine)

Question 35

How is ACh resynthesized?

Answer 35

The enzyme acetylcholinesterase converts acetylcholine into choline and acetate. This enzyme is abundant in the synaptic cleft to clear it of acetylcholine to be used for muscular function.

Question 36

What is a triad?

Answer 36

triple-unit structure consisting of T tubule sandwiched between sacs of cisternae in sarcoplasmic reticulum

Question 37

What function does the triad serve?

Answer 37

Release of calcium ions into the cytosol when the sarcoplasmic reticulum depolarizes. AP from T tubules is transferred to cisternae of Sarcoplasmic Reticulum and Calcium channels at cisternae open.

Question 38

What is the importance of dystrophin?

Answer 38

Dystrophin anchoring costamere and sarcolemma.

connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane

Question 39

What is the life expectancy of an individual with muscular dystrophy?

Answer 39

30 years

Question 40

T/F muscle fibers are the smallest unit of skeletal muscle.

Answer 40

False; Myofilaments or filaments (actin and myosin) are even smaller structures within the sarcomere that are involved in muscular contraction.