Muscular Changes

Question 1

When do Myoblasts become post-miotic

Answer 1

after birth

Question 2

Satellite Cells

Answer 2

provide nuclei to the muscle cells as they get larger - important for muscle growth and repair

Question 3

When do most skeletal muscles present in mature form?

Answer 3

8 weeks gestation

Question 4

Fiber type in prenatal

Answer 4

All are present, but the proportions change

Question 5

Prenatal Type 1 muscle fibers develop from

Answer 5

• primarily myotubules –> do NOT require neural input to develop into fiber types
• seen in the fetus first

Question 6

Prenatal Type 2 fibers develop from

Answer 6

Develop from secondary myotubules –> DO require neural input
-not seen until 31-37 weeks gestation

Question 7

Progression of muscle fiber formation in prenatal stage

Answer 7

Myogenic precursor cells - embryonic myoblasts - primary myotubue - secondary myotube - muscle fibers

Question 8

Characteristic of muscular system from infancy-childhood in first year

Answer 8

Increase in muscle fiber size and number of fibers

Question 9

Increase in fiber number (in first year) due to

Answer 9

division of existing muscle cells

Question 10

Fiber type differentiation continues into:

Answer 10

adolescense (or young adulthood)

Question 11

Children up to 15 years have more ___ than ___

Answer 11

Type 1 than Type II muscles fibers

Question 12

When do you achieve adult levels of Type IIb until

Answer 12

young adulthood

Question 13

Strength gains follow a typical growth curve and are related to

Answer 13

1. Height and weight
2. Muscle mass
3. Fiber type distribution

Question 14

Muscles add the number of sarcomeres and fibrils to

Answer 14

add length

Question 15

Does bone growth proceed during adolescence?

Answer 15

Yes & stimulates muscle length

Question 16

Boys increase strength > girls and its related to hormones

Answer 16

testosterone, growth horomone, insulin, thyroid hormone

Question 17

1% year decline in number and size of muscle fibers after

Answer 17

20 years of age

Question 18

Characteristics of muscular system during older adulthood

Answer 18

• decreased number of motor units due to nervous system changes
• decreased number of contractile proteins due to decreased muscle protein synthesis
• hormonal changes: less growth horomone and testosterone
• increased basement membrane thickness - hypoxia - decreased mass

Question 19

Older adulthood muscle fiber changes

Answer 19

• Increase in Type I
• Decrease in type II; primary decrease in type IIb = decreases in power
• hypothesized that Type IIb become Type IIa or Type I

Question 20

In older adulthood, muscle fibers are replaced with:

Answer 20

fat & connective tissue (non-contractile) – increases stiffness

Question 21

increased connective tissue in the endomesium =

Answer 21

thickened basement membrane

Question 22

Motor end plate changes in oder adult

Answer 22

• enlarged synaptic cleft
• slower axoplasmic transport
• thickening of basement
• clumping of synaptic vesicles

Question 23

Muscle strength peaks in

Answer 23

age 30

Question 24

Muscle strength stays steady until

Answer 24

30-50s

Question 25

30% decrease in muscle strength between:

Answer 25

50-70; accelerates after age 70

Question 26

Is eccentric or concentric strength maintained better>

Answer 26

eccentric

Question 27

Is LE loss or UE muscle loss greater?

Answer 27

LE

Question 28

Does muscle endurance change much with age?

Answer 28

NO - not if you maintain exercise

Question 29

Muscle power in older adults

Answer 29

-Loss of power is greater than strength due to loss of type IIB fibers

Question 30

Best types of exercise for baby/young child

Answer 30

Short bouts of exercise with frequent rest breaks
As childhood progresses: increase the bout of activity time, introduce more power activities, but understand you won’t get greatest response of IIb fibers until adolesence

Question 31

Endochondroal bone growth

Answer 31

• rapid bone growth through childhood
• completed at adolescence (closure of growth plates)
• increased risk for epiphyseal and apophyseal injuries

Question 32

secondary ossificiation centers appear in

Answer 32

endochondral bone growth

Question 33

endochondral bone growth is stimulated by stress/loading on bone

Answer 33

• weight bearing

- muscle activity

Question 34

epiphysis

Answer 34

stimulated by weight bearing

Question 35

Apophysis

Answer 35

• growth zone at site of muscle attachment
• results in change of bone shape
• stimulated by a muscle pull

Question 36

Mechanostat theory

Answer 36

How mechanical input is used to develop effective load-bearing bone

• size
• shape
• density

As mechanical strain is placed upon bone by muscle or gravity, the bone adapts to effectively support the body

Nutritional, hormonal, and behavioral factors are also considered

Question 37

Endochondral ossification happens first in the

Answer 37

diaphysis

Question 38

Endochondral ossification happens second in the

Answer 38

epiphysis

Question 39

Appositional bone growth

Answer 39

• occurs throughout life
• stimulated by weight bearing and muscle pull
• increases diameter of bone; reduction in cortical thickness, increase in marrow cavity diameter

Question 40

50% of peak bone mass by

Answer 40

10 years of age

Question 41

90% of peak bone mass by

Answer 41

20 years of age

Question 42

architectural changes in bone with aging

Answer 42

• fibers are more longitudinal
• osteons shorter
• haversian canal wider
• increased mineral deposition; cancellous bone
• increased cross linkage and rearrangement of collagen